On-chip systems for CW-lidar operations

Abstract

An integrated system for selectively emitting and detecting coherently optical signals is disclosed. In one implementation an electro-optical demultiplexing / multiplexing module comprises a plurality of transmitting optical waveguides each configured to transmit an optical signal; a plurality of receiving optical waveguides each configured to receive an optical signal, wherein each receiving optical waveguide is associated with a corresponding one of the plurality of transmitting optical waveguides; an optical distribution matrix comprising at least one input and a plurality of outputs, each output being coupled to one of the plurality of transmitting optical waveguides; and, an electro-optical reception matrix comprising a plurality of inputs, each input being coupled to one of the plurality of receiving optical waveguides and associated with one of the plurality of outputs of the optical distribution matrix, and at least one output.

Description

ON-CHIP SYSTEMS FOR CW-LIDAR OPERATIONSCross References to Related ApplicationsThis application claims the benefit of priority of U.S. Provisional Patent Application No. 63 / 600,820, filed November 20, 2023; U.S. Provisional Patent Application No. 63 / 614,669, filed December 26, 2023; U.S. Provisional Patent Application No. 63 / 615,489, filed December 28, 2023; and U.S. Provisional Patent Application No. 63 / 685,712, filed August 22, 2024. All of the foregoing applications are incorporated herein by reference in their entirety.Technical Field

[0001] The present disclosure relates generally to technology for scanning a surrounding environment including, for example, systems that use CW-LIDAR technology to detect objects in the surrounding environment. More specifically, these technologies may be implemented using Photonic Integrated Circuits (PIC).Background

[0002] With the advent of driver-assist systems and autonomous vehicles, automobiles need to be equipped with systems capable of reliably sensing and interpreting their surroundings, including identifying obstacles, hazards, objects, and other physical parameters that might impact the navigation of the vehicle. To this end, a number of differing technologies have been suggested including RADAR, LIDAR, and camera-based systems, operating alone or in a redundant manner.

[0003] One consideration with driver assistance systems and autonomous vehicles is the ability of the system to determine surroundings across different conditions. A light detection and ranging system, (LIDAR a.k.a. LADAR) is an example of technology that operates by illuminating objects with light and measuring the reflected light with a sensor. Based on measured optical signals at different spatial locations, in a field of view (FOV), such as FOV pixels, a point cloud of range data may be generated where each FOV pixel is associated with a particular range measurement value corresponding to a distance between the LIDAR system and objects or portions of objects in the LIDAR FOV.

[0004] Frequency Modulated Continuous Wave (FMCW) LIDAR systems, a category of CW-LIDAR systems, employ frequency-modulated light beams to sweep across the surrounding environment. A portion of the incident light that undergoes diffuse reflection from an object is captured and combined with a local oscillator wave. The resulting difference in frequency between these two signals, referred to as the beat frequency, is thendetected and utilized to calculate not only the distance between the LiDAR system and the object but also its relative velocity along the direction of the light beam. These measurements are obtained by employing a tunable laser as the light source and a photodiode as the detector, which enables the extraction of the beat frequency from the photodiode's current output.

[0005] Efforts to integrate CW-LIDAR systems such as FMCW-LIDAR onto photonic integrated chips (e.g., Silicon photonic chips) have been made to enhance their suitability for mobile applications like autonomous vehicles. Several challenges are associated with these implementations, such as miniaturization of certain optical components (e.g., tunable laser, photodiodes...), optical efficiency, signal processing, environmental robustness, cost and / or scalability. Certain prior systems tend to incorporate optical circulators or optical splitter to emit, collect, and route optical signals. As these components are either non-integrable or present limited efficiency, there is a need for an integrated system ensuring the above-noted function with a sufficient level of efficiency. Furthermore, as certain parasitic effects such as speckles may compromise the quality of acquired images, an efficient LIDAR system must incorporate a level of diversity in its measurements to mitigate these effects.

[0006] The systems of the present disclosure are directed towards fully integrated emitting, collecting, and routing systems overcoming one or more of the above-stated problems, among other problems in the prior art.SUMMARY

[0007] Embodiments consistent with the present disclosure provide integrated electro- optical multiplexing / scanning systems for selectively emitting and detecting coherently optical signals. The disclosed embodiments may be implemented within a CW-LIDAR system.

[0008] In one embodiment, an electro-optical demultiplexing / multiplexing module is disclosed. The module may comprise a plurality of transmitting optical waveguides each configured to transmit an optical signal; a plurality of receiving optical waveguides each configured to receive an optical signal, wherein each receiving optical waveguide is associated with a corresponding one of the plurality of transmitting optical waveguides; an optical distribution matrix comprising at least one input and a plurality of outputs, each output being coupled to one of the plurality of transmitting optical waveguides, configured to: selectively distribute an optical output signal generated by a light source to the plurality oftransmitting optical waveguides; and, an electro-optical reception matrix comprising a plurality of inputs, each input being coupled to one of the plurality of receiving optical waveguides and associated with one of the plurality of outputs of the optical distribution matrix, and at least one output, the electro-optical reception matrix configured to: mix, for each particular receiving waveguide among the plurality of receiving waveguides, a portion of the optical output signal generated by the light source with the optical signal received by the particular receiving waveguide to provide a plurality of interference signals, one for each of the plurality of receiving waveguides; generate a plurality of electronic signal outputs, one for each of the plurality of interference signals; and sum all of the plurality of electronic signal outputs to provide a summed signal to the at least one output.

[0009] In another embodiment, a photonic integrated circuit (PIC) chip is disclosed. The chip may comprise at least one transmitting waveguide configured to deliver, at an output port, an optical beam to a predetermined location in space; at least one receiving waveguide configured to receive, at an input port via, a reflected optical beam from the predetermined location in space; wherein the optical beam and the reflected optical beam pass through a scanning module; and wherein a physical location on the PIC chip of the output port of the at least one transmitting waveguide and a physical location on the PIC chip for the input port of the at least one receiving waveguide are arranged relative to each other with respect to one or more scanning properties of the scanning module such that the optical beam and the reflected optical beam overlap over a predetermined spatial range.

[0010] In yet another embodiment, a photonic integrated circuit (PIC) chip is disclosed. The chip may comprise a transmitting waveguide, configured to convey a transmission optical signal from a laser source; a receiving waveguide, configured to convey a fraction of a reflected optical signal from a target toward a detection module, wherein the detection module is configured to detect the fraction of the reflected optical signal; a Polarization Beam Rotator Splitter (PBRS) including a first port, a second port, and a third port; a local oscillator light path configured to convey at least a sample portion of the transmission optical signal from the laser source to the detection module; wherein the transmitting waveguide is coupled to the first port of the PBRS and the receiving waveguide is coupled to the second port of the PBRS, or vice versa; wherein the third port of the PBRS is coupled to an output coupler, wherein the output coupler is configured to output the transmission optical signal and collect the reflected optical signal from the target; and, wherein the PBRS is configured to: transmit the transmission optical signal to the output coupler; convert a polarization state of an optical signal travelling from the second port to thethird port or vice versa; separate the reflected optical signal from the target collected by the output coupler into a first divided optical signal and a second divided optical signal; output the first divided optical signal via the first port; and, output the second divided optical signal via the second port.

[0011] In yet another embodiment, a photonic integrated circuit (PIC) chip is disclosed. The photonic integrated circuit (PIC) chip may comprise a transmitting waveguide, configured to convey a transmission optical signal from a laser source; a receiving waveguide, configured to convey a fraction of a reflected optical signal from a target toward a detection module, wherein the detection module is configured to detect the fraction of the reflected optical signal; a first Polarization Beam Rotator Splitter (PBRS) including a first port, a second port, and a third port; a second Polarization Beam Rotator Splitter (PBRS) including a first port, a second port, and a third port; a local oscillator light path configured to convey at least a sample portion of the transmission optical signal from the laser source to the detection module; an optical splitter, including a transmitting port, a receiving port, a first transport port, and a second transport port, wherein the transmitting port is coupled to the transmitting waveguide, the receiving port is coupled to the receiving waveguide, the first transport port is coupled to the second port of the first PBRS, the second transport port is coupled to the first port of the second PBRS, and wherein the optical splitter is configured to split the transmission optical signal to provide a first portion of the transmission optical signal at the first transport port and a second portion of the transmission optical signal at the second transport port; wherein the third port of the first PBRS is coupled to a first output coupler, the first output coupler being configured to output the first portion of the transmission optical and collect a first portion of the reflected optical signal, and wherein the first PBRS is configured to: transmit the first portion of the transmission optical signal to the first output coupler; convert a polarization state of an optical signal travelling from the second port of the first PBRS to the third port of the first PBRS or vice versa; separate the first portion of the reflected optical signal from the target collected by the first output coupler into a first divided optical signal and a second divided optical signal; and transmit the second divided optical signal to the first transport port of the optical splitter; wherein the third port of the second PBRS is coupled to a second output coupler, the second output coupler is configured to output the second portion of the transmission optical signal and collect a second portion of the reflected optical signal, and wherein the second PBRS is configured to: transmit to the second portion of the transmission optical signal to the second output coupler; convert a polarization state of an optical signal travelling from the second port of the second PBRS tothe third port of the second PBRS or vice versa; separate the second portion of the reflected optical signal from the target collected by the second output coupler into a third divided optical signal and a fourth divided optical; and transmit the third divided optical signal to the second transport port of the optical splitter; wherein the optical splitter is further configured to combine the second divided optical signal with the third divided optical signal to provide the fraction of the reflected optical signal from the target conveyed by the receiving waveguide from the receiving port.

[0012] In yet another embodiment, a photonic integrated circuit (PIC) chip is disclosed. The photonic integrated circuit (PIC) chip may comprise a transmitting waveguide, configured to convey a transmission optical signal from a laser source; one or more optical splitters, arranged in a binary tree structure of optical splitters comprising N layers with N being a natural number greater than zero, wherein each of the one or more optical splitters includes a transmitting port, a receiving port, a first output port, and a second output port, and wherein a total number of optical couplers is equal to 2N-1; a plurality of Polarization Beam Rotator Splitters (PBRSs), each including a first port, a second port, and a third port, each third port being coupled to an associated output coupler from among a plurality of output couplers configured to output a portion of the transmission optical signal from the laser source and collect a portion of a reflected optical signal from a target, wherein a total number of PRBSs and of output couplers is equal to 2N; a first plurality of receiving waveguides, configured to convey a first sub-portion of the reflected optical signal from the target, wherein a total number of receiving waveguides in the first plurality of receiving waveguides is equal to 2N, each receiving waveguide from the first plurality of waveguides being coupled to the first port or the second port of a PBRS from among the plurality of PBRSs; a second plurality of receiving waveguides, configured to convey a second sub-portion of the reflected optical signal from the target, wherein a total number of receiving waveguides in the second plurality of receiving waveguides is equal to 2N-1, each receiving waveguide from the second plurality of waveguides being coupled to the receiving port of an optical splitter from among the one or more optical splitters; a plurality of detection modules, each detection module being coupled to a receiving waveguide from among the first plurality of receiving waveguides or the second plurality of receiving waveguides, each of the plurality of detection modules being configured to detect a first sub-portion or a second sub-portion of the reflected optical signal from the target; a plurality of local oscillator light paths, each local oscillator light path being configured to convey at least a sample portion of the transmission optical signal from the laser source to a distinct detection module from among the plurality ofdetection modules; wherein the transmitting waveguide is coupled to the transmitting port of a first optical splitter of a first layer of the binary tree structure of optical splitters; wherein the first output port and the second output port of each optical splitter of the first N-l-th layers of the binary tree structure of optical splitters are coupled to transmitting ports of two subsequent optical splitters; wherein the first output port and the second output port of each optical splitter of an N-th layer of the binary tree structure of optical splitters are coupled to distinct PBRSs from among the plurality of PBRSs; and wherein each PBRS from among the plurality of PBRS is configured to: transmit the portion of the transmission optical signal from the laser source conveyed by the binary tree structure of optical splitters to the associated output coupler; convert a polarization state of an optical signal travelling from the second port to the third port or vice versa; separate the portion of the reflected optical signal from the target collected by the associated output coupler into a first divided optical signal and a second divided optical signal; transmit the first divided optical signal to the binary tree structure of optical splitters or one receiving waveguide from among the first plurality of receiving waveguides; and, transmit the second divided optical signal to the binary tree structure of optical splitters or one receiving waveguide from among the first plurality of receiving waveguides.

[0013] In yet another embodiment, a photonic integrated circuit (PIC) chip is disclosed. The photonic integrated circuit (PIC) chip may comprise a transmitting waveguide, configured to convey a transmission optical signal from a laser source; a first receiving waveguide, configured to convey a first divided optical signal toward a first detection module, wherein the first detection module is configured to detect the first divided optical signal; a second receiving waveguide, configured to convey a second divided optical signal toward a second detection module, and wherein the second detection module is configured to detect the second divided optical signal; a first local oscillator light path configured to convey at least one first sample portion of the transmission optical signal from the laser source to the first detection module; a second local oscillator light path configured to convey at least one second sample portion of the transmission optical signal from the laser source to the second detection module; a first Polarization Beam Rotator Splitter (PBRS) including a first port, a second port, and a third port; wherein the transmitting waveguide is coupled to the first port of the first PBRS or to the second port of the first PBRS, and the third port of the first PBRS is coupled to a first output coupler configured to output the transmission optical signal from the laser source, and wherein the first PBRS is configured to: transmit the transmission optical signal to the first output coupler; and, convert a polarization state of an optical signaltravelling from the second port of the first PBRS to the third port of the first PBRS or vice versa; and, a second Polarization Beam Rotator Splitter (PBRS) including a first port, a second, and a third port; wherein the first port of the second PBRS is coupled to the first receiving waveguide, the second port of the second PBRS is coupled to the second receiving waveguide, and the third port of the second PBRS is coupled to a second output coupler configured to collect a reflected optical signal from the target, and wherein the second PBRS is configured to: convert a polarization state of an optical signal travelling from the second port of the second PBRS port to the third port of the second PBRS or vice versa; separate the reflected optical signal from the target collected by the second output coupler into the first divided optical signal and the second divided signal; transmit the first divided optical signal to the first receiving waveguide; and, transmit the second divided optical signal to the second receiving waveguide.

[0014] In yet another embodiment, a photonic integrated circuit (PIC) chip is disclosed. The photonic integrated circuit (PIC) chip may comprise a transmitting waveguide, configured to convey a transmission optical signal from a laser source; a first receiving waveguide, configured to convey a first fraction of at least one reflected optical signal from a target toward a first detection module, wherein the first detection module is configured to detect the first fraction of the at least one reflected optical signal; a second receiving waveguide, configured to convey a second fraction of the at least one reflected optical signal from the target toward a second detection module, wherein the second detection module is configured to detect the second fraction of the at least one reflected optical signal; a first local oscillator light path configured to convey at least one first sample portion of the transmission optical signal from the laser source to the first detection module; a second local oscillator light path configured to convey at least one second sample portion of the transmission optical signal from the laser source to the second detection module; an optical splitter, including a first receiving port, a second receiving port, a first input port, and a second input port, wherein the first receiving port is coupled to the first receiving waveguide, and the second receiving port is coupled to the second receiving waveguide; a Polarization Beam Rotator Splitter (PBRS), having a first port coupled to the transmitting waveguide, a second port coupled to the first input port of the optical splitter, and a third port coupled to a first output coupler configured to output the transmission optical signal from the laser source and to collect a first reflected optical signal from the target, wherein the PBRS is configured to: transmit the transmission optical signal from a laser source conveyed by the transmitting waveguide to the first output coupler; convert a polarization state of an optical signaltravelling from the second port to the third port or vice versa; separate the first reflected optical signal from the target collected by the first output coupler into a first optical subsignal and into a second optical sub-signal; and transmit the second optical sub-signal to the first input port of the optical splitter; and, a second output coupler coupled to the second input port of the optical splitter and configured to collect a second reflected optical signal from the target; and, wherein the optical splitter is further configured to combine the second optical sub-signal transmitted by the PBRS with the second reflected optical signal from the target collected by the second output coupler to provide the first fraction of the at least one reflected optical signal from the target and the second fraction of the at least one reflected optical signal from the target.

[0015] In yet another embodiment, a photonic integrated circuit (PIC) chip is disclosed. The photonic integrated circuit (PIC) chip may comprise a transmitting waveguide, configured to convey a transmission optical signal from a laser source; a 90° optical hybrid coupled to a first balanced photodetector and to a second balanced photodetector; a local oscillator light path configured to convey at least one sample portion of the transmission optical signal from the laser source to the 90° optical hybrid; a Polarization Beam Rotator Splitter (PBRS), having a first port coupled to the transmitting waveguide, a second port coupled to the 90° optical hybrid, and a third port coupled to a first output coupler configured to output the transmission optical signal from the laser source and to collect a first reflected optical signal from the target, wherein the PBRS is configured to: transmit the transmission optical signal from a laser source conveyed by the transmitting waveguide to the first output coupler; convert a polarization state of an optical signal travelling from the second port to the third port or vice versa; separate the first reflected optical signal from the target collected by the first output coupler into a first optical sub-signal and into a second optical sub-signal; and transmit the second optical sub-signal to the 90° optical hybrid; a second output coupler coupled to the 90° optical hybrid and configured to collect a second reflected optical signal from the target; and, wherein the optical hybrid configured to mix the at least one sample portion of the transmission optical signal from the laser source conveyed by the local oscillator light path with at least one of the second optical sub-signal or the second reflected optical signal to provide a pair of in-phase combined signals and a pair of quadrature combined signal, and wherein the first balanced photodetector is configured to detect the pair of in-phase combined signal and the second balanced photodetector is configured to detect the pair of quadrature combined signal.

[0016] In yet another embodiment, a photonic integrated circuit (PIC) chip is disclosed. The photonic integrated circuit (PIC) chip may comprise a transmitting waveguide, configured to convey a transmission optical signal from a laser source; a receiving waveguide, configured to convey a fraction of a reflected optical signal from a target toward a detection module, wherein the detection module is configured to detect the fraction of the reflected optical signal; an optical splitter, including a transmitting port, a receiving port, a first output port, and a second output port, wherein the transmitting port is coupled to the transmitting waveguide, the receiving port is coupled to the receiving waveguide, and wherein the optical splitter is configured to split the transmission optical signal conveyed by the transmitting waveguide to provide a first portion of the transmission optical signal and a second portion of the transmission optical signal; a first output waveguide disposed between the first output port and a first output coupler, wherein the first output coupler is configured to output the first portion of the transmission optical signal and collect a first portion of the reflected optical signal, and wherein the first output waveguide is configured to convey the first portion of the transmission optical signal to the first output coupler and to convey the first portion of the reflected optical signal to the first output port; a second output waveguide disposed between the second output port and a second output coupler, wherein the second output coupler is configured to output the second portion of the transmission optical signal and collect a second portion of the reflected optical signal, and wherein the second output waveguide is configured to convey the second portion of the optical signal to the second output coupler and to convey the second portion of the reflected optical signal to the second output port; a local oscillator light path configured to convey at least a sample portion of the transmission optical signal from the laser source to the detection module; a phase shifter included in at least one of the first output waveguide or the second output waveguide; and, wherein the optical splitter is further configured to combine the first portion of the reflected optical signal with the second portion of the reflected optical signal to provide the fraction of the reflected optical signal to the receiving waveguide.BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate various disclosed embodiments. In the drawings:

[0018] Fig. 1A is a plot representing the time-dependent evolution of the frequency of a local oscillator and a reflection signal reflected from a moving object, consistent with some embodiments of the present disclosure;

[0019] Fig. IB is a diagrammatic representation of an exemplary CW-LIDAR system, consistent with some embodiments of the present disclosure;

[0020] Fig. 1C is an illustration of an exemplary vehicle including a CW-LIDAR system, consistent with some embodiments of the present disclosure;

[0021] Fig. 2A is an illustration of an exemplary implementation of an electro-optical multiplexing / scanning module, consistent with some embodiments of the present disclosure;

[0022] Fig. 2B is an illustration of an exemplary implementation of an electro-optical multiplexing / scanning module featuring a local oscillator light path, consistent with some embodiments of the present disclosure;

[0023] Fig. 2C is an illustration of an exemplary implementation of an electro-optical multiplexing / scanning module featuring a plurality of local oscillator light paths, consistent with some embodiments of the present disclosure;

[0024] Fig. 3 A is an illustration of an exemplary implementation of an optical distribution matrix based on a plurality of optical switches arranged in a tree structure, consistent with some embodiments of the present disclosure;

[0025] Fig. 3B is an illustration of an exemplary Mach-Zehnder interferometer based optical switch, consistent with some embodiments of the present disclosure;

[0026] Fig. 3C is an illustration of an exemplary micro-ring based optical switch, consistent with some embodiments of the present disclosure;

[0027] Fig. 3D is an illustration of an exemplary electro-optical switch, consistent with some embodiments of the present disclosure;

[0028] Fig. 3E is an illustration of an exemplary thermo-optical switch, consistent with some embodiments of the present disclosure;

[0029] Fig. 3F is an illustration of an exemplary implementation of an optical distribution matrix based on a bus waveguide and a plurality of micro-rings switches, consistent with some embodiments of the present disclosure;

[0030] Fig. 3G is an illustration of an exemplary implementation of an optical distribution matrix based on a plurality of MEMS switches, consistent with some embodiments of the present disclosure;

[0031] Fig. 3H is an illustration of an exemplary implementation of an optical distribution matrix based on a wavelength demultiplexer, consistent with some embodiments of the present disclosure;

[0032] Fig. 31 is an illustration of an exemplary implementation of an optical distribution matrix based on a combination of active and passive optical switches, consistent with some embodiments of the present disclosure;

[0033] Fig. 4A is an illustration of an exemplary implementation of an electro-optical optical reception matrix featuring a plurality of couplers and a plurality of photodetectors, consistent with some embodiments of the present disclosure;

[0034] Fig. 4B is another illustration of an exemplary implementation of an electro- optical optical reception matrix featuring a plurality of couplers and a plurality of photodetectors, consistent with some embodiments of the present disclosure;

[0035] Fig. 4C is yet another illustration of an exemplary implementation of an electro-optical optical reception matrix featuring a plurality of couplers and a plurality of photodetectors, consistent with some embodiments of the present disclosure;

[0036] Fig. 4D is yet another illustration of an exemplary implementation of an electro-optical optical reception matrix featuring a plurality of couplers and a plurality of photodetectors, consistent with some embodiments of the present disclosure;

[0037] Fig. 4E is yet another illustration of an exemplary implementation of an electro-optical optical reception matrix featuring a plurality of couplers and a plurality of photodetectors, consistent with some embodiments of the present disclosure;

[0038] Figs. 5A-B are illustrations of common approaches to address routing challenges in LIDAR systems using a circulator or a directional coupler;

[0039] Fig. 6A is an illustration of a photonic integrated circuit including a transmitting waveguide with its associated output port and a receiving waveguide with its associated input port, along with a scanning module, consistent with some embodiments of the present disclosure;

[0040] Fig. 6B is an illustration of the evolution of an overlap between a Tx optical beam and a Rx reflected optical beam in the presence of a pitch caused by the arrangement of the transmitting and receiving waveguide illustrated in Fig. 6A, consistent with some embodiments of the present disclosure;

[0041] Fig. 6C is an illustration of the evolution of the position of a Tx optical beam and an Rx reflected optical beam during a scanning process, consistent with some embodiments of the present disclosure;

[0042] Fig. 6D is a plot illustrating the evolution of the overlap between a Tx optical beam and an Rx reflected optical beam as a function of a distance taking into account thepitch effect and scanning properties of a scanning module, consistent with some embodiments of the present disclosure;

[0043] Fig. 7, is an illustration of an exemplary edge coupler and of an exemplary grating coupler, consistent with some embodiments of the present disclosure;

[0044] Fig. 8 is an illustration of a photonic integrated circuit including a transmitting waveguide and a receiving waveguide both featuring straight sections and tapered sections, consistent with some embodiments of the present disclosure;

[0045] Fig. 9, is an illustration of three exemplary tapered profiles, consistent with some embodiments of the present disclosure;

[0046] Fig. 10 is an illustration of an exemplary integrated Polarization Beam Rotator Splitter (PBRS), consistent with some embodiments of the present disclosure;

[0047] Fig. 11 is an illustration of an exemplary photonic integrated circuit including a monostatic pixel architecture having a PBRS, consistent with some embodiments of the present disclosure;

[0048] Fig. 12A is an illustration of another exemplary photonic integrated circuit including a monostatic pixel architecture having a PBRS and an optical switch, consistent with some embodiments of the present disclosure;

[0049] Fig. 12B is an illustration of two different operation modes for an optical switch, consistent with some embodiments of the present disclosure;

[0050] Fig. 13 is an illustration of yet another exemplary photonic integrated circuit including a monostatic pixel architecture having a PBRS and an optical splitter, consistent with some embodiments of the present disclosure;

[0051] Fig. 14 is an illustration of yet another exemplary photonic integrated circuit including a monostatic pixel architecture having a PBRS, an optical switch and a 90° optical hybrid, consistent with some embodiments of the present disclosure;

[0052] Fig. 15A is an illustration of an exemplary photonic integrated circuit including a dual monostatic pixel architecture having two PBRS, consistent with some embodiments of the present disclosure;

[0053] Fig. 15B is an illustration of another exemplary photonic integrated circuit including a dual monostatic pixel architecture having two PBRS, and a 90° optical hybrid consistent with some embodiments of the present disclosure;

[0054] Fig. 15C is an illustration of yet another exemplary photonic integrated circuit including a dual monostatic pixel architecture having two PBRS, a first and second additionalreceiving waveguides, a first and second additional detection modules and a first and second additional local oscillator light path, consistent with some embodiments of the present disclosure;

[0055] Fig. 16A is an illustration of an exemplary photonic integrated circuit including a plural monostatic pixel architecture having an optical splitter binary tree structure with a single layer, consistent with some embodiments of the present disclosure;

[0056] Fig. 16B is an illustration of another exemplary photonic integrated circuit including a plural monostatic pixel architecture having an optical splitter binary tree structure with two layers, consistent with some embodiments of the present disclosure;

[0057] Fig. 17A is an illustration of an exemplary photonic integrated circuit including a bistatic pixel architecture having two PBRS, a first detection channel, and a second detection channel, consistent with some embodiments of the present disclosure;

[0058] Fig. 17B is an illustration of another exemplary photonic integrated circuit including a bistatic pixel architecture having two PBRS, a first detection channel including a first 90° optical hybrid, and a second detection channel including a second 90° optical hybrid, consistent with some embodiments of the present disclosure;

[0059] Fig. 17C is an illustration of yet another exemplary photonic integrated circuit including a bistatic pixel architecture having two PBRS, a first detection channel, and a second detection channel and an optical switch, consistent with some embodiments of the present disclosure;

[0060] Fig. 17D is an illustration of yet another exemplary photonic integrated circuit including a bistatic pixel architecture having two PBRS, a first detection channel, and a second detection channel, an optical switch, and a third monostatic detection channel, consistent with some embodiments of the present disclosure;

[0061] Fig. 17E is an illustration of yet another exemplary photonic integrated circuit including a bistatic pixel architecture having two PBRS, a first detection channel including a first 90° optical hybrid, and a second detection channel including a second 90° optical hybrid, an optical switch, and a third monostatic detection channel including a third 90° optical hybrid, consistent with some embodiments of the present disclosure.

[0062] Fig. 18A is an illustration of an exemplary photonic integrated circuit including a monostatic / bistatic pixel architecture, consistent with some embodiments of the present disclosure;

[0063] Fig. 18B is an illustration of an exemplary photonic integrated circuit including an IQ monostatic / bistatic pixel architecture, consistent with some embodiments of the present disclosure;

[0064] Fig. 18C is an illustration of another exemplary photonic integrated circuit including an IQ monostatic / bistatic pixel architecture, having a main local oscillator light path consistent with some embodiments of the present disclosure;

[0065] Fig. 19 is an illustration of yet another exemplary photonic integrated circuit including an IQ monostatic / bistatic pixel architecture, having a 90° optical hybrid; consistent with some embodiments of the present disclosure;

[0066] Fig. 20A is an illustration of an exemplary photonic integrated circuit including a dual monostatic pixel architecture having a phase shifter, consistent with some embodiments of the present disclosure;

[0067] Fig. 20B is an illustration of another exemplary photonic integrated circuit including a dual monostatic pixel architecture having a phase shifter and a detection module including a 90° optical hybrid, consistent with some embodiments of the present disclosure;

[0068] Fig. 20C is an illustration of yet another exemplary photonic integrated circuit including a dual monostatic pixel architecture having a phase shifter and an additional phase shifter, consistent with some embodiments of the present disclosure;

[0069] Fig. 20D is an illustration of yet another exemplary photonic integrated circuit including a dual monostatic pixel architecture having a phase shifter and a detection module including a PBRS, consistent with some embodiments of the present disclosure.DETAILED DESCRIPTION

[0070] The following detailed description refers to the accompanying drawings.Wherever possible, the same reference numbers are used in the drawings and the following description to refer to the same or similar parts. While several illustrative embodiments are described herein, modifications, adaptations and other implementations are possible. For example, substitutions, additions or modifications may be made to the components illustrated in the drawings, and the illustrative methods described herein may be modified by substituting, reordering, removing, or adding steps to the disclosed methods. Accordingly, the following detailed description is not limited to the disclosed embodiments and examples.Instead, the proper scope is defined by the appended claims. Also, it is to be understood that the present disclosure may be practiced without one or more of these details.

[0071] Moreover, various terms used in the specification and claims may be defined or summarized differently when discussed in connection with differing disclosed embodiments. It is to be understood that the definitions, summaries, and explanations of terminology in each instance apply to all instances, even when not repeated, unless the transitive definition, explanation or summary would result in the inoperability of an embodiment. Throughout, this disclosure mentions “disclosed embodiments,” which refer to examples of inventive ideas, concepts, and / or manifestations described herein. Many related and unrelated embodiments are described throughout this disclosure. The fact that some “disclosed embodiments” are described as exhibiting a feature or characteristic does not mean that other disclosed embodiments necessarily share that feature or characteristic.

[0072] This disclosure employs open-ended permissive language, indicating for example, that some embodiments “may” employ, involve, or include specific features. The use of the term “may” and other open-ended terminology is intended to indicate that although not every embodiment may employ the specific disclosed feature, at least one embodiment employs the specific disclosed feature. Definitions

[0073] Disclosed embodiments may involve an optical system. As used herein, the term “optical system” broadly includes any system that is used for the generation, detection and / or manipulation of light. By way of example only, an optical system may include one or more optical components for generating, detecting and / or manipulating light. For example, light sources, lenses, mirrors, prisms, beam splitters, collimators, polarizing optics, optical modulators, optical switches, optical amplifiers, optical detectors, optical sensors, fiber optics, semiconductor optic components, while each not necessarily required, may each be part of an optical system. In addition to the one or more optical components, an optical system may also include other non-optical components such as electrical components (in which case the system could be referred to as an electro-optical system), mechanical components, chemical reaction components, and semiconductor components. The non-optical components may cooperate with the optical components of the optical system. For example, the optical system may include at least one processor for analyzing detected light.

[0074] Consistent with the present disclosure, the optical system may be a LIDAR system. As used herein, the term "LIDAR system" broadly includes any system that candetermine values of parameters indicative of a distance between a pair of tangible objects based on reflected light. In one embodiment, the LIDAR system may determine a distance between a pair of tangible objects based on reflections of light emitted by the LIDAR system. As used herein, the term "determine distances" broadly includes generating outputs that are indicative of distances between pairs of tangible objects. The determined distance may represent the physical dimension between a pair of tangible objects. By way of example only, the determined distance may include a line of flight distance between the LIDAR system and another tangible object in a field of view of the LIDAR system. In another embodiment, the LIDAR system may determine the relative velocity between a pair of tangible objects based on reflections of light emitted by the LIDAR system. Examples of outputs indicative of the distance between a pair of tangible objects include a number of standard length units between the tangible objects (e.g. number of meters, number of millimeters), a number of arbitrary length units (e.g. number of LIDAR system lengths), a ratio between the distance to another length (e.g. a ratio to a length of an object detected in a field of view of the LIDAR system), an amount of time (e.g. given as standard unit, arbitrary units or ratio, for example, the time it takes light to travel between the tangible objects), one or more locations (e.g. specified using an agreed coordinate system, specified in relation to a known location), and more.

[0075] In some embodiments, the LIDAR system may be used for detecting a plurality of objects in an environment of the LIDAR system. The term "detecting an object in an environment of the LIDAR” broadly includes generating information which is indicative of an object that reflected light toward a detector associated with the LIDAR system. If more than one object is detected by the LIDAR system, the generated information pertaining to different objects may be interconnected, for example, a car is driving on a road, a bird is sitting on the tree, a man touches a bicycle, or a van moves towards a building. The dimensions of the environment in which the LIDAR system detects objects may vary with respect to implementation. For example, the LIDAR system may be used for detecting a plurality of objects in an environment of a vehicle on which the LIDAR system is installed, up to a horizontal distance of 100m (or 200m, 300m, etc.), and up to a vertical distance of 10m (or 25m, 50m, etc.). In another example, the LIDAR system may be used for detecting a plurality of objects in an environment of a vehicle or within a predefined horizontal range (e.g., 25°, 50°, 100°, 180°, etc.), and up to a predefined vertical elevation (e.g.. ±10°, ±20°, +40°-20°, ±90° or 0°-90°).

[0076] As used herein, the term "detecting an object" may broadly refer to determining an existence of the object (e.g., an object may exist in a certain direction withrespect to the LIDAR system and / or to another reference location, or an object may exist in a certain spatial volume). Additionally, or alternatively, the term "detecting an object" may refer to determining a distance between the object and another location (e.g., a location of the LIDAR system, a location on earth, or a location of another object). Additionally or alternatively, the term "detecting an object" may refer to identifying the object (e.g. classifying a type of object such as car, plant, tree, road; recognizing a specific object (e.g., the Washington Monument); determining a license plate number, determining a composition of an object (e.g., solid, liquid, transparent, semitransparent); determining a kinematic parameter of an object (e.g., whether it is moving, its velocity, its movement direction, expansion of the object). Additionally, or alternatively, the term "detecting an object" may refer to generating a point cloud map in which every point of one or more points of the point cloud map corresponds to a location in the object or a location on a face thereof. In one embodiment, the data resolution associated with the point cloud map representation of the field of view may be associated with 0.1x0.1° or 0.05°x0.05° of the field of view.

[0077] Consistent with the present disclosure, the term "object" broadly includes a finite composition of matter that may reflect light from at least a portion thereof. For example, an object may be at least partially solid (e.g., cars, trees); at least partially liquid (e.g. puddles on the road, rain); at least partly gaseous (e.g., fumes, clouds); made from a multitude of distinct particles (e.g. sand storm, fog, spray); and may be of one or more scales of magnitude, such as ~1 millimeter (mm), ~5mm, ~10mm, ~50mm, -lOOmm, ~500mm, ~1 meter (m), ~5m, ~10m, ~50ra, ~100tn, and so on. Smaller or larger objects, as well as any size in between those examples, may also be detected. It is noted that for various reasons, the LIDAR system may detect only part of the object. For example. In some cases, light may be reflected from only some sides of the object (e.g., only the side opposing the LIDAR system will be detected); in other cases, light may be projected on only part of the object (e.g. laser beam projected onto a road or a building); in other cases, the object may be partly blocked by another object between the LIDAR system and the detected object; in other cases, the LIDAR's sensor may only detects light reflected from a portion of the object, e.g., because ambient light or other interferences interfere with detection of some portions of the object.

[0078] Consistent with the present disclosure, a LIDAR system may be configured to detect objects by scanning the environment of LIDAR system. The term "scanning the environment of LIDAR system" broadly includes illuminating the field of view or a portion of the field of view of the LIDAR system. In one example, scanning the environment of LIDAR system may be achieved by moving or pivoting a light deflector to deflect light indiffering directions toward different parts of the field of view. In another example, scanning the environment of LIDAR system may be achieved by combining or splitting optical signals, using a multiplexing / demultiplexing module. In another example, scanning the environment of LIDAR system may be achieved by changing the position (i.e., location and / or orientation) of a sensor with respect 10 the field of view. In another example, scanning the environment of LIDAR system may be achieved by changing a positioning (i.e., location and / or orientation) of a light source with respect to the field of view. In yet another example, scanning the environment of LIDAR system may be achieved by changing the positions of at least one light source and of at least one sensor to move rigidly respect to the field of view (i.e., the relative distance and orientation of the at least one sensor and of the at least one light source remains).

[0079] As used herein the term "field of view of the LIDAR system" may broadly include an extent of the observable environment of LIDAR system in which objects may be detected. It is noted that the field of view (FOV) of the LIDAR system may be affected by various conditions including but not limited to an orientation of the LIDAR system (e.g., the direction of an optical axis of the LIDAR system); a position of the LIDAR system with respect to the environment (e.g., distance above ground and adjacent topography and obstacles); operational parameters of the LIDAR system (e.g., emission power, computational settings, defined angles of operation), etc. The field of view of LIDAR system may be defined, for example, by a solid angle (e.g., defined using , 0 angles, in which y and 0 are angles defined in perpendicular planes, e.g., with respect to symmetry axes of the LIDAR system and / or its FOV). In one example, the field of view may also be defined within a certain range (e.g., up to 200m or more).

[0080] Disclosed embodiments may involve obtaining information for use in generating reconstructed three-dimensional models. Examples of types of reconstructed three-dimensional models which may be used include point cloud models, and Polygon Mesh (e.g., a triangle mesh). The terms "point cloud" and "point cloud model" are widely known in the art, and should be construed to include a set of data points located spatially in some coordinate system (i.e., having an identifiable location in a space described by a respective coordinate system). The term "point cloud point" refers to a point in space (which may be dimensionless, or a miniature cellular space, e.g. 1 cm3), and whose location may be described by the point cloud model using a set of coordinates (e.g. (X, Y, Z), (r.<b,9)). By way of example only, the point cloud model may store additional information for some or all of its points (e.g., color information for points generated from camera images). Likewise, anyother type of reconstructed three-dimensional model may store additional information for some or all of its objects. Similarly, the terms "polygon mesh" and "triangle mesh" are widely known in the art, and are to be construed to include, among other things, a set of vertices, edges and nodes that define the shape of one or more 3D objects (such as a polyhedral object). The models may include one or more of the following: triangles (triangle mesh), quadrilaterals, or other simple convex polygons, since this may simplify rendering. The faces may also include more general concave polygons or polygons with holes. Polygon meshes may be represented using differing techniques, such as Vertex -vertex meshes, Face-vertex meshes, Winged-edge meshes and Render dynamic meshes. Different portions of the polygon mesh (e.g., vertex, face, edge) are located spatially in some coordinate system (i.e., having an identifiable location in a space described by the respective coordinate system), either directly and / or relative to one another. The generation of the reconstructed three-dimensional model may be implemented using any standard, dedicated and / or novel photogrammetry technique, many of which are known in the art. It is noted that other types of models of the environment may be generated by the LIDAR system.

[0081] Consistent with disclosed embodiments, the LIDAR system may include at least one light source. As used herein, the term "light source" broadly refers to any device configured to generate / emit light. In one embodiment, the light source may be a laser such as a solid-state laser, laser diode, a high-power laser, or an alternative light source such as a light emitting diode (LED)-based light source. In addition, a light source may emit light in differing formats, such as light pulses, continuous wave (CW), quasi-CW, and so on. For example, one type of light source that may be used is a vertical-cavity surface-emitting laser (VCSEL). Another type of light source that may be used is an external cavity diode laser (ECDL). In some examples, the light source may include a laser diode configured to emit light at a wavelength between about 650 nm and 1150 nm. Alternatively, the light source may include a laser diode configured to emit light at a wavelength between about 800 nm and about 1000 nm, between about 850 nm and about 950 nm, or between about 1300 nm and about 1600 nm. Unless indicated otherwise, the term "about" with regard to a numeric value is defined as a variance of up to 5% with respect to the stated value.

[0082] Consistent with disclosed embodiments, the LIDAR system may include at least one scanning unit with at least one light deflector configured to deflect light from the light source in order to scan the field of view. The term "light deflector" broadly includes any mechanism or module which is configured to make light deviate from its original path; for example, a mirror, a prism, controllable lens, a single-axis or biaxial mechanical mirror,mechanical scanning polygons, active diffraction (e.g. controllable LCD), Risley prisms, nonmechanical-electro-optical beam steering (such as made by Vscent), polarization grating (such as offered by Boulder Non-Linear Systems), optical phased array (OP A), and more. In one embodiment, a light deflector may include a plurality of optical components, such as at least one reflecting element (e.g., a mirror), at least one refracting element (e.g. a prism, a lens), and so on. In one example, the light deflector may be movable, to cause light to deviate to differing degrees (e.g., discrete degrees, or over a continuous span of degrees). The light deflector may optionally be controllable in different ways (e.g., deflect to a degree a, change deflection angle by Aa, move a component of the light deflector by M millimeters, change speed in which the deflection angle changes). In addition, the light deflector may optionally be operable to change an angle of deflection within a single plane (e.g., 0 coordinate). The light deflector may optionally be operable to change an angle of deflection within two nonparallel planes (e.g., 0 and cp coordinates). Alternatively, or in addition, the light deflector may optionally be operable to change an angle of deflection between predetermined settings (e.g. along a predefined scanning route) or otherwise. With respect to the use of light deflectors in LIDAR systems, it is noted that a light deflector may be used in the outbound direction (also referred to as transmission direction, or TX) to deflect light from the light source to at least a part of the field of view. However, a light deflector may also be used in the inbound direction (also referred to as reception direction, or RX) to deflect light from at least a part of the field of view to one or more light sensors.

[0083] Disclosed embodiments may involve pivoting the light deflector in order to scan the field of view. As used herein the term "pivoting" broadly includes rotating of an object (especially a solid object) about one or more axis of rotation, while substantially maintaining a center of rotation fixed. In one embodiment, the pivoting of the light deflector may include rotation of the light deflector about a fixed axis (e.g., a shaft). For example, in some MEMS mirror implementations, the MEMS mirror may move by actuation of a plurality of benders connected to the mirror, the mirror may experience some spatial translation in addition to rotation. Nevertheless, such mirror may be designed to rotate about a substantially fixed axis, and therefore consistent with the present disclosure it is considered to be pivoted. In other embodiments, some types of light deflectors (e.g. non- mechanical- electro-optical beam steering, Optical phased array (OP A)) do not require any moving components or internal movements in order to change the deflection angles of deflected light. It is noted that any discussion relating to moving or pivoting a light deflector is also mutatis mutandis applicable to controlling the light deflector such that it changes a deflectionbehavior of the light deflector. For example, controlling the light deflector may cause a change in a deflection angle of beams of light arriving from at least one direction.

[0084] Consistent with disclosed embodiments, the LIDAR system may include at least one sensing unit with at least one sensor configured to detect reflections from objects in the field of view. The term "sensor" broadly includes any device, element, or system capable of measuring properties (e.g., power, frequency, phase, pulse timing, pulse duration) of electromagnetic waves (e.g., optical signal) and generating an output (e.g., an electrical signal) relating to the measured properties. In some embodiments, the sensing unit may include one or more detection modules, each including at least one sensor. As used herein, a detection module may refer to any sort of system including components designed to detect and convert electromagnetic waves (e.g., optical signals) into electrical signals. Detection modules may output a current signal. Following the conversion of the optical signals using, for instance, a photodetector, each of these detection modules can generate a current that is proportional to the respective signal being processed. In some embodiments, current signals may be combined by a short circuit. This implies that the individual current signals may be directly merged or interconnected, typically with minimal impedance, facilitating their summation, integration, or aggregation. The short-circuiting process allows for the simultaneous consideration of information from different channels, enabling a consolidated analysis or processing of each of the combined signals collectively.

[0085] In some embodiments, the at least one sensor may include a plurality of detectors constructed from a plurality of detecting elements. The at least one sensor may include light sensors of one or more types. It is noted that the at least one sensor may include multiple sensors of the same type which may differ in other characteristics (e.g., sensitivity, size). Other types of sensors may also be used. Combinations of several types of sensors can be used for different reasons, such as improving detection over a span of ranges (especially in close range); improving the dynamic range of the sensor; improving the temporal response of the sensor, and improving detection in varying environmental conditions (e.g., atmospheric temperature, rain, etc.).

[0086] In some embodiments, the at least one sensor includes a photodetector. A photodetector refers to an electronic component designed to detect and convert incoming optical signals into electrical signals. Photodetectors exhibit sensitivity to a broad range of light wavelengths, encompassing visible light, infrared, and ultraviolet radiation, depending on their intended application and design. They find extensive use across diverse fields, including optical communication systems, imaging devices (such as cameras), lightmeasurement instruments, and optical sensing systems. Photodetectors play an important role in capturing and processing optical information within electronic devices and systems, facilitating the conversion of light signals into practical electrical signals for subsequent analysis and data processing. Various technologies and architectural designs are available for photodetectors, such as photodiodes, phototransistors, and avalanche photodiodes, each tailored to specific performance requirements and operating principles.

[0087] In some embodiments, the at least one sensor may include a balanced photodetector. As used herein, a balanced photodetector refers to a specific type of photodetector configuration including two closely matched photodetectors (e.g., photodiode) that are operated differentially, meaning that their electrical outputs are subtracted from each other commonly. A balanced photodetector may be employed in optical communication and coherent optical detection systems. The balanced configuration is designed to cancel out or mitigate common-mode components, such as optical intensity fluctuations or phase noise while enhancing the sensitivity to the differential signal. When coupled with an optical coupler (e.g., a 50:50 optical coupler), a beat frequency between two incoming optical signals may be determined, providing an output that cancels common-mode components and which may enhance sensitivity to the differential signal. The coupler initially mixes the incoming optical signals coming from two distinct input branches and distributes evenly the generated interference signal to two output branches. Each output branch is connected to one of the closely matched photodetectors within the balanced photodetector configuration. The photodetectors in the balanced pair individually detect the optical power in their respective branches. By subtracting the electrical signals generated by these detectors, the commonmode components, which are identical in both branches, get cancelled out, leaving behind only the differential signal component. This electronic signal output carries a frequency equal to the beat frequency between the two incoming signals.

[0088] In some embodiments, the at least one sensor includes a PIN diode, a type of semiconductor diode with a wide, undoped intrinsic region sandwiched between a p-type semiconductor and an n-type semiconductor region. A PIN diode can convert incoming optical signal into an electrical current. PIN diode characteristics include but are not limited to high sensitivity, fast response time, low noise and wide spectral response. Additionally, PIN diode may be implemented on a silicon chip / photonic integrated circuit chip.

[0089] In some embodiments, the at least one sensor includes a SiPM (Silicon photomultipliers) which is a solid-state single-photon-sensitive device built from an array of avalanche photodiode (APD), single photon avalanche diode (SPAD), serving as detectionelements on a common silicon substrate. In one example, a typical distance between SPADs may be between about 10pm and about 50um, wherein each SPAD may have a recovery time of between about 20ns and about 100ns. Similar photomultipliers from other, non-silicon materials may also be used. Although a SiPM device works in di gi tai / switching mode, the SiPM is an analogue device because all the microcells may be read in parallel, making it possible to generate signals within a dynamic range from a single photon to hundreds and thousands of photons detected by the different SPADs. It is noted that outputs from different types of sensors (e.g., SPAD, APD, SiPM, PTN diode, Photodetector) may be combined together to a single output which may be processed by a processor of the LIDAR system.

[0090] Consistent with disclosed embodiments, the LIDAR system may include or communicate with at least one processor configured to execute differing functions. The at least one processor may constitute any physical device having an electric circuit that performs a logic operation on input or inputs. For example, the at least one processor may include one or more integrated circuits (ICs), including Application-specific integrated circuits (ASICs), microchips, microcontrollers, microprocessors, all or part of a central processing unit (CPU), graphics processing unit (GPU), digital signal processor (DSP), field- programmable gate array (FPGA), or other circuits suitable for executing instructions or performing logic operations. The instructions executed by at least one processor may, for example, be pre-loaded into a memory integrated with or embedded into the controller or may be stored in a separate memory. The memory may comprise B Random Access Memory (RAM), a Read-Only Memory (ROM), a hard disk, an optical disk, a magnetic medium, a flash memory, other permanent, fixed, or volatile memory, or any other mechanism capable of storing instructions. In some embodiments, the memory is configured to store information representative data about objects in the environment of the LIDAR system. In some embodiments, the at least one processor may include more than one processor. Each processor may have a similar construction or the processors may be of differing constructions that are electrically connected or disconnected from each other. For example, the processors may be separate circuits or integrated into a single circuit. When more than one processor is used, the processors may be configured to operate independently or collaboratively. The processors may be coupled electrically, magnetically, optically, acoustically, mechanically or by other means that permit them to interact.

[0091] Disclosed embodiments may involve one or more optical waveguides. As used herein, an optical waveguide may refer to any physical structure or medium designed to confine and guide light (electromagnetic waves) as it propagates through it. Opticalwaveguides are made from materials with optical properties that enable total internal reflection, which ensures that light remains confined within the waveguide's core and does not escape into the surrounding medium (e.g., air, vacuum, or any other material with a lower refractive index than the optical waveguide). Optical waveguides possess different characteristic features such as cross-section profile and dimensions (e.g., rectangular or squared cross-section), material properties (dielectric constant), electromagnetic modes (polarization, number of nodes / lobes), optical loss characteristics or non-linear effects.

[0092] Electromagnetic modes in optical waveguides are defined by the distribution of the electric and magnetic field components within the waveguide structure. Electromagnetic modes are characterized by mode orders (number of nodes of the electric / magnetic field along a direction orthogonal to the direction of propagation), polarization states, and cutoff frequency (i.e., frequency above which optical signals will propagate through the waveguide in a particular mode with minimal attenuation). For example, a rectangular waveguide supports two types of modes: TE Modes (modes that have an electric field with no component along the direction of propagation) and TM Modes (modes that have a magnetic field with no component along the direction of propagation). The number of modes, as well as their characteristics, are directly correlated to the cross- sectional profile and the material properties of the waveguides. In some embodiments, the cross-sectional profile dimensions of an optical waveguide may align with the wavelength optical signal it conveys. For example, a rectangular cross-section transmitting waveguide for a 1550 nm optical signal may have dimensions ranging from 500 to 2000 nm in width, and 200 - 300 nm height (for example, 220 nm for a Silicon core material). In some embodiments, the cross-sectional dimensions of optical waveguide may align with the wavelength order of magnitude of the light it conveys.

[0093] Consistent with the disclosed embodiments, a LIDAR system may include one or more optical waveguides. In some embodiments, a LIDAR system may include at least one transmitting (optical) waveguide and / or at least one receiving (optical) waveguide. Within a LIDAR system, the designated transmitting waveguide may be referred to as a transmitting channel. As used herein, a transmitting waveguide may be an optical waveguide that serves as the conduit through which a transmission optical signal (also referred to as Tx signal) from a light source (e.g., a laser source) is guided to a predetermined location within the LIDAR FOV. A transmitting waveguide may possess specific characteristics, including material properties, cross-sectional profile, and supported electromagnetic modes. The characteristics and parameters of the transmitting waveguide may influence the transmission of the signal tothe predetermined location within the LIDAR FOV. As used herein, a receiving waveguide may be configured to convey a fraction of a reflected optical signal (also referred to as Rx signal) from a target object in the LIDAR FOV toward a detection module, wherein the detection module is configured to detect the fraction of the reflected signal. Within a LIDAR system, the designated receiving waveguide may be referred to as a receiving channel. This waveguide may serve as the conduit guiding the reflected optical signal (Rx signal) from a predetermined location within the LIDAR FOV, where a target may be situated. Similar to its transmitting counterpart, the receiving waveguide may possess specific characteristics, including material properties, cross-sectional profile, and supported electromagnetic modes.

[0094] In some embodiments, the transmitting waveguide and the receiving waveguide may share one or more parameter values. For instance, both optical waveguides may be constructed from the same material(s) and possess similar cross-sectional profiles, with uniform dimensions generating identical electromagnetic modes and substantially identical Mode Field Diameters (MFDs). In some cases, the transmitting and receiving waveguides may have different overall lengths. In some embodiments, either or both of the transmitting and receiving waveguides may function as single mode waveguides, which may support only a single electromagnetic mode within the relevant range of optical wavelengths for the transmitted or received signals. For example, in the case of waveguides characterized by rectangular cross-sections, only the primary fundamental TE Mode, referred to as TEoo, may be sustained.

[0095] Disclosed embodiments may involve one or more optical switches. As used herein, an optical switch refers to a component designed to selectively route optical signals within an optical network. These switches facilitate the management and control of optical data flow, allowing signals to be directed to specific destinations. Optical switches are characterized by their number of inputs (n) and outputs (m), denoted as n x m optical switches. In this instance, the switch may be 2 x 2 switch with at least two inputs and two outputs. Optical switches may be broadly categorized into passive and active types based on functionality. Passive optical switches operate without external power or control signals, relying on components like couplers, splitters, and waveguides to redirect or split optical signals. In contrast, active optical switches require external control and power sources, using mechanisms such as electro-optical, thermo-optical, opto-mechanical, or other non-linear effects to actively manipulate signal paths. Active switches are suitable in scenarios requiring dynamic control and precise routing, while passive switches, on the other hand, can distribute optical power across different outputs when used for signal splitting. In some embodiments,the switch may include an active switch such as a Mach-Zehnder interferometer, an electro- optical switch, or a thermo-optical switch. Additionally, in some embodiments, a 2 x 2 optical switch may have two modes of operation, namely bus mode and cross mode. In the bus mode, a first input is coupled to a first output, while the second input is coupled to the second output. On the other hand, in the cross mode, the first input is coupled to second output and the second output is coupled to the first input.

[0096] Disclosed embodiments may involve one or more optical splitters (also referred to as optical coupler). As used herein, an optical splitter may refer to any optical device configured to divide or combine optical signals. An optical splitter may function as an optical switch and may typically be equipped with multiple input / output ports. In practical terms, if an optical signal is provided at one of the input ports, the optical splitter may divide the signal into multiple portions and route the portions to the output ports. For example, the optical splitter may be configured to divide the transmission optical signal (Tx signal) into two or more portions. Moreover, an optical splitter can handle multiple input signals, combining them and subsequently splitting the resulting combination into the output ports. Optical splitters may be categorized as passive or active components. Passive splitters may have fixed weights assigned to different inputs / outputs during the division or combination process, determined by their design. In contrast, active splitters allow dynamic tuning of weights through an external control signal (e.g., an electric signal). In some embodiments, the optical splitter may include a directional coupler or a multimode interference (MMI) coupler. Both directional couplers and MMIs are passive integrated structures, and their function as splitters or mixers depends on the optical properties of the materials used in their construction and their specific design. A directional coupler consists of two waveguides separated by a small gap and relies on evanescent coupling. By adjusting parameters such as the thickness of the waveguides or the width of the gap, the transfer of optical signals between the waveguides may be controlled, enabling mixing or splitting operations. On the other hand, a multimode interferometer (MMI) is a passive optical device that utilizes the interference of multiple optical modes within a wider core waveguide to split or combine optical signals. MMIs function based on the principle that these multiple modes can interfere constructively or destructively, creating a power imbalance and allowing for controlled power splitting or combining without requiring active components.

[0097] Disclosed embodiments may involve one or more phase shifters. As used herein, a phase shifter may refer to any sort of component designed to modify the temporal phase of an optical signal passing through it. When a phase shifter is included in awaveguide, the phase shifter may be integrated or embedded within the structure of the waveguide. For example, a phase shifter or the phase shifting function may be realized by modifying one or more parameters over a predetermined portion of a waveguide structure, such as altering cross-sectional profile dimensions, or manipulating the electromagnetic modes sustained by such a waveguide. This type of phase shifter is often termed a passive phase shifter because the phase shift is dependent on the waveguide's design. It is fixed during nanofabrication, meaning the phase shift occurs universally and cannot be tuned or deactivated. Alternatively, a phase shifter can be implemented as an active phase shifter comprising a controller combined with a waveguide structure. In this scenario, the phaseshifting controller is integrated into the waveguide structure to alter the phase of an optical signal as it travels therethrough. These are phase shifters controlled by external signals, such as electrical signals, enabling control over the phase-tuning function. The phase tuning function can be activated or deactivated as needed, providing flexibility in manipulating the phase of the optical signal within the integrated structure. For example, in some embodiments, the phase shifter (of phase tuner may be a thermal phase shifter (a.k.a. thermo- optical phase shifter) or an electro-optical phase shifter. Thermo-optical phase shifters and electro-optical phase shifters rely on the fact that the refractive index of a material may vary in response to a change in temperature or an applied electric field. By applying an electrical current to a resistor or an electrode, a portion of a waveguide structure may undergo a local change in temperature or electric field. Consequently, the material constituting the waveguide may experience a local shift in refractive index, thereby leading to an induced phase shift.

[0098] Disclosed embodiments may involve one or more Polarization Beam Rotator Splitters (PBRS). As used herein a PBRS corresponds to any optical device capable of manipulating the polarization state of an optical signal. PBRS devices may be used in managing polarization diversity within optical systems. PBRS may include reciprocal optical devices and may also include at least three input and output ports, allowing for the separation / combination of differently polarized components of incoming / outcoming light signals. The first port may be dedicated to a first polarization state, the second port to a second polarization state (e.g., orthogonal polarization state), or rather to the first polarization state rotated to the second polarization state or vice-versa, while the third port may accommodate a combination of the first and second polarization states. In accordance with the disclosed embodiments, a PBRS may be fully integrated on a photonic integrated circuit (PIC) chip. In such scenarios, the PBRS may be constructed using waveguides configured with characteristics designed to implement the functionalities described above.

[0099] Disclosed embodiments may involve one or more output couplers (also referred to as free-space coupler). As used herein, a free-space coupler denotes any optical device designed to facilitate light coupling between optical structures (such as waveguides or PBRSs) and free-space optical beams. When an output coupler is configured to both emit and collect a free-space optical beam, it may be referred to as monostatic. Conversely, if an output coupler is solely configured to emit or collect a free-space optical beam, it may be referred to as bistatic.Disclosed embodiments may include one or more optical hybrids. As used herein, an optical hybrid refers to a six-port optical device featuring two input ports and four output ports, structured to provide four distinct vectorial additions at each of its output ports. This process involves the combination of a primary signal from one of the two input ports with a secondary signal from the remaining input port. Optical hybrids may encompass various optical components, including optical splitters, combiners, phase shifters, or interferometers. A specific variant of the optical hybrid relevant for complex IQ demodulation is the 90° optical hybrid. This particular optical hybrid is configured to mix the primary signal with the four quadrature states associated with the secondary signal. A 90° optical hybrid may incorporate adjustability, for example by including one or more optical phase tuners. These phase tuners may be used to fine-tune and correct any deviations from the 90-degree path difference that may arise due to various sources of noise, such as temperature fluctuations or manufacturing mismatches.

[0100] Disclosed embodiments may involve one or more local oscillator light paths. As used herein, a "local oscillator light path" refers to a dedicated optical channel carrying a reference signal, known as the local oscillator (LO) signal. The LO light path may be configured to convey at least a sample portion of the transmission optical signal from the laser source to a sensing unit and / or detection module. This signal may act as a stable reference in optical processes like heterodyne / homodyne detection, interacting with other optical signals for information extraction, signal modulation, or various measurements. In applications like FMCW-LIDAR, the LO signal may be mixed with the reflected optical signal (Rx) to determine a beat frequency, which can be used to estimate target range and velocity. The beat frequency between the LO and the Rx signals may be determined using a balanced photodetector.

[0101] The local oscillator light path may assume various configurations. For example, an LO light path may be realized with a waveguide structure. The local oscillator may be a replica of the unmodulated light source signal. Alternatively, the local oscillatormay be a replica of the modulated Tx signal transmitted through the Tx waveguide. In some embodiments, the local oscillator light path may be coupled directly to a light source (e.g., a laser source) or to a transmitting waveguide. While embodiments disclosed may indicate one of such local oscillators, it should be noted that these are interchangeable.CW-LIDAR system overview

[0102] Continuous Wave (CW) LIDAR systems represent a broad range of LIDAR technology, encompassing various methodologies like Frequency Modulated Continuous Wave (FMCW) and Amplitude Modulated Continuous Wave (AMCW) LIDAR, each employing unique techniques for environmental sensing and object detection.

[0103] FMCW-LIDAR systems are a subcategory of LIDAR systems, specifically falling under Coherent LIDAR systems. In contrast to Time of Flight (ToF) LIDAR systems, which measure the time taken for a pulse of light to travel to and from an object, FMCW- LIDAR systems employ a frequency-modulated (e.g., linearly chirped) light source. This source emits light that splits into two components: one is directed towards an object to be detected in the FOV (following the transmission or outbound direction, denoted as Tx), while the other (referred to as LO - local oscillator) remains local. When the part directed towards the object returns after reflecting off the object (following the reflection or inbound direction, denoted as Rx), it combines with the LO signal. This reflected optical signal Rx corresponds to a delayed replica of the LO waveform. An interferometric device is then used to measure the frequency difference, known as the beat frequency, between the Rx and LO signals. This beat frequency offers information about the distance (range, denoted as 'd') between the FMCW-LIDAR system and the object.

[0104] In cases where the object is in motion, the received signal experiences an additional frequency shift due to the Doppler effect known as the Doppler shift. This shift is proportional to the object's velocity (V) relative to the FMCW-LIDAR system. The Doppler shift is calculated using the formula: 5f ~ (2v / X), where 5f represents the Doppler shift, and 'X' stands for the wavelength of light.

[0105] To simultaneously measure both the range ('d') and relative velocity (V), a common approach is to employ triangular modulation or a saw-tooth pattern. This pattern consists of an up-chirp immediately followed by a down-chirp. The frequency differences (5fupand Sfdown) measured during the up-chirp and down-chirp phases can then be used to calculate both the range and the relative velocity. These values are given as follows:Range d = (c / 4r) * (5fup+ Sfdown)Relative Velocity v = (X / 4) * (5fup- bfdown)In these equations, c represents the speed of light and r is the chirp ramp rate.

[0106] Fig.1 A illustrates the time-dependent evolution of the frequency of a local oscillator (LO) signal (represented by the continuous black line) and an inbound / reflection signal Rx (represented by the dashed black line) originating / reflected from a moving object. In this illustration, a saw-tooth modulation pattern (linear chirp) is employed. The Rx signal is essentially a delayed replica of the LO signal, and due to the dynamic nature of the target object, Doppler shifts become evident during both the ascending and descending phases of the chirp. By utilizing the relationships described above, it is possible to calculate both the distance (d) between the LIDAR system and the object, as well as the object's relative velocity (v) in relation to the LIDAR system.

[0107] Amplitude-modulated continuous-wave (AMCW) LIDAR shares similarities with Time-of-Flight (TOF) LIDAR, as it measures the time delay of signals at the receiver. However, in AMCW LIDAR, an intensity pattern, with a frequency fAM is imposed on the transmitted optical power. This chirp encodes a phase shift on the received signal, which is detected by mixing the received intensity with an unaltered electronic version of the chirp. This approach allows for precise measurement of the phase shift, enabling accurate distance calculations. The range d of AMCW-LIDAR is given by the following relation: d=(c / 47t)*(A / fAM), wherein c represents the speed of light, A the phase shift between the transmitted and reflected signal, and fAM is the modulation frequency of the AMCW-LIDAR.

[0108] In the upcoming sections, unless explicitly stated otherwise, the reference to a "LIDAR system" primarily concerns Continuous Wave (CW) LIDAR. However, it is to be appreciated that certain components and configurations introduced in the following sections may be relevant and applied in a wider range of LIDAR technologies, encompassing non-CW LIDAR. Fig. IB illustrates a CW-LIDAR system 100 including a light source 112, a modulation unit 114, a scanning unit 116, a sensing unit 118, and a processing unit 120. Consistent with embodiments of the present disclosure, light source 112 and the above- mentioned units 114, 116, 118, and 120 may be interconnected. In Fig. IB, black continuous lines represent optical connections within the various components of the LIDAR system 100, while the dashed black lines represent electrical connections. As used herein, "optical connections" refer to any means for transmitting optical signals, such as optical fibres, optical waveguides, free-space transmission, or any other suitable optical components for carrying optical signals. Conversely, electrical connections, refer to any type of systems or methodsfor transmitting electrical signals and information, including cables, wires, printed circuit traces, antennas, or any other physical connections capable of conveying electrical signals or data. In accordance with the disclosed embodiments, sensing unit 118 may include at least one sensor and processing unit 120 may include at least one processor.

[0109] Modulation unit 114 is responsible for generating a continuous wave optical signal with a modulated frequency profile such as the one depicted in Fig. 1 A, or a modulated intensity profile and closely interfaces with the light source 112. Consistent with embodiments of the present disclosure, modulation unit 114 may include a signal / waveform generator. For example, modulation unit 114 may achieve frequency modulation by utilizing a signal within the microwave or radio frequency (RF) range to control a laser-driving current (light source 112). Additionally, in some embodiments, modulation unit 114 may include one or more modulators, including phase modulators or IQ modulators. Although modulation unit 114 and light source 112 are represented as two separate entities, it is to be appreciated that these two components may be integrated into a single physical system, such as a tunable laser source. Moreover, in some other embodiments, the modulation function performed by modulation unit 114 may be carried out by other components (e.g., scanning unit 116) within the LIDAR system and may be integrated into those components as well.

[0110] Furthermore, in some embodiments, modulation unit 114 may include monitoring and feedback mechanisms, via a calibration module to ensure that the generated optical signal meets the desired specifications and is stable / reproducible over time. Any deviations or drifts such as deterministic (e.g., modulation non-linearity) and stochastic modulation errors (e.g., phase noise) in frequency or intensity may be corrected or mitigated to maintain measurement accuracy. The calibration module may encompass a range of optical and electrical components including but not limited to a delay line, one or more sensors (e.g., photodiodes, frequency -to-amplitude converter), or one or more photonic structures that generate control signals. These control signals may be employed within a feedback loop to rectify any errors introduced in the modulation pattern. Processing unit 120 within the broader LIDAR system may process these signals. Alternatively, the calibration module may include an independent processing unit, possibly housing at least one processor specifically configured to analyze the control signals and manage the feedback loop.

[0111] Consistent with embodiments of the present disclosure, scanning unit 116 may include at least one multiplexing / demultiplexing module 122 and at least one light deflector 124. Multiplexing / demultiplexing module 122 may be used to generate more points in the LIDAR system 100 FOV and / or increase the resolution of the LIDAR. A Multiplexingmodule (often referred to as MUX) is an integrand part of a scanning unit, as it is configured to split a single optical signal into multiple signals each being directed to different points in the FOV. A Demultiplexing module (often referred to as a DEMUX), on the other hand, is configured to combine multiple optical signals into a single optical signal which may facilitate detection and reduce the number of sensors in sensing unit 118 (e.g., a single sensor can detect optical signals reflected from different points in the LIDAR FOV).

[0112] While depicted as separate entities in Fig. IB, any of the LIDAR system modules or units may be consolidated. For instance, light source 112 and modulation unit 114 could be manufactured as a single entity / body, or scanning unit 116 might incorporate the multiplexing / demultiplexing module 122, light deflector 124, and sensing unit 118.

[0113] In some embodiments, LIDAR system 100 may include one or more additional units, not illustrated in Fig. IB. For example, LIDAR system 100 may further include a measuring unit encompassing different devices (e.g., wavelength meter, power meter, etc.) configured to assess one or more characteristics of at least a portion of the optical signal generated by the light source 112. This measuring unit may be integrated into the LIDAR 100 in a manner that allows it to measure the characteristics of a portion of the optical signal before modulation. In this scenario, a portion of the optical signal is diverted towards the measuring unit prior to entering the modulation unit. Alternatively, the measurements may be conducted post-modulation, with a portion of the optical signal being redirected towards the measuring unit after being generated by light source 112 and passing through modulation unit 114. In another example, LIDAR system 100 may further include an amplification unit including at least one amplifier or amplification means. The optical signal generated by laser source 112 may be amplified to reach the desired power levels for transmission and to maintain a consistent signal-to-noise ratio (SNR) throughout the measurement process. By passing through the amplifier (e.g., Semiconductor Optical Amplifier - SOA, Erbieum Doped Fiber Amplifier - EDFA or Raman amplifier), the signal undergoes a significant boost in strength before proceeding to interface with other elements of the LIDAR system and ultimately being directed towards an external object. In yet another example, LIDAR system 100 may further include a signal conditioning unit configured to shape (e.g., filter, modify polarization etc.) the generated optical signal before exiting the LIDAR system.

[0114] Consistent with the present disclosure, LIDAR system 100 may be mountable on vehicle 110 as illustrated in Fig. 1C. For example, LIDAR system 100 may be used in autonomous or semi-autonomous road vehicles (for example, cars, buses, vans, trucks andany other vehicle type). Autonomous road vehicles with LIDAR system 100 may scan their environment and drive to a destination without certain human inputs. Similarly, LIDAR system 100 may also be used in autonomous / semi-autonomous aerial vehicles (for example, UAV, drones, quadcopters, and any other airborne vehicle or device); or in an autonomous or semi-autonomous water vessel (e.g., boat, ship, submarine, or any other watercraft). Autonomous aerial vehicles and watercraft with LIDAR system 100 may scan their environment and navigate to a destination autonomously or using a remote human operator. According to one embodiment, vehicle 110 (either a road vehicle, aerial vehicle, or watercraft) may use LIDAR system 100 to aid in detecting and scanning the environment in which vehicle 110 is operating.

[0115] In one embodiment, processor unit 120 may be configured (e.g., programmed) to coordinate operation of light source 112 with the movement of light deflector 124 in order to scan a field of view 130. During a scanning cycle, each instantaneous position of at least one light deflector 124 may be associated with a particular portion 132 (e.g., a vertical section as illustrated in Fig. 1C) of field of view (FOV) 130. In addition to this coordinated operation, processing unit 120 may assume different functions related to other components of LIDAR system 100. For example, it may control light source 112 and modulation unit 114, analyze and post-process the data and signal generated by sensing unit 118, process signals measured by a measurement unit or adjust a level of amplification associated with an amplification unit.

[0116] In some embodiments, LIDAR system 100 may include at least one optional optical window 126 for directing light (Tx signals) projected towards field of view 130 and / or receiving light reflected (Rx signals) from objects in field of view 130. Optional optical window 126 may serve different purposes, such as collimation of the projected light and focusing of the reflected light. In one embodiment, optional optical window 124 may be an opening, a flat window, a lens, or any other type of optical window.

[0117] In some embodiments, LIDAR system 100 may include one or more scanning units 116 to scan the environment around vehicle 110. LIDAR system 100 may be attached or mounted to any part of vehicle 110. Sensing unit 118 may receive reflections from the surroundings of vehicle 110, and transfer reflection signals indicative of light reflected from objects in field of view 130 to processing unit 120. Consistent with the present disclosure, scanning units 116 may be mounted to or incorporated into a bumper, a fender, a side panel, a spoiler, a roof, a headlight assembly, a taillight assembly, a rear-view mirror assembly, a hood, a trunk, a grill, a windscreen or any other suitable part of vehicle 110 capable ofhousing at least a portion of the LIDAR system. In some cases, LIDAR system 100 may capture a complete surround view of the environment of vehicle 110. Thus, LIDAR system 100 may have a 360-degree horizontal field of view. In one example, as shown in Fig. 1C, LIDAR system 100 may include a single scanning unit 116 mounted on a roof of vehicle 110. Alternatively, LIDAR system 100 may include multiple scanning units (e.g., two, three, four, or more scanning units 116) each with a field of view such that in the aggregate the horizontal field of view is covered by a 360-degree scan around vehicle 110. One skilled in the art will appreciate that LIDAR system 100 may include any number of scanning units 116 arranged in any manner, each with an 80° to 120° field of view or less, depending on the number of units employed. Moreover, a 360-degree horizontal field of view may be also obtained by mounting multiple LIDAR systems 100 on vehicle 110, each with a single scanning unit 116. It is nevertheless noted that the one or more LIDAR systems 100 do not have to provide a complete 360° field of view, and that narrower fields of view may be useful in some situations. For example, vehicle 110 may require a first LIDAR having a field of view of 75° looking ahead of the vehicle, and possibly a second LIDAR system 100 with a similar FOV looking backwards (optionally with a lower detection range). It is also noted that different vertical field-of-view angles may also be implemented.

[0118] In accordance with the disclosed embodiments, at least a portion of the optical components involved in CW-LIDAR system 100 may be implemented / integrated on a Photonic Integrated Chip (PIC). For example, referring to Fig. IB, any of light source 112, modulation unit 114, scanning unit 116 and / or sensing unit 118 may be implemented on a PIC. As used herein, a PIC may refer to any kind of semiconductor device that integrates multiple optical components and functions on a single chip, akin to how electronic integrated circuits (ICs) or Printed Circuit Boards (PCBs) combine various electronic components. These PICs perform functions that involve detecting, generating, transporting, and processing light (photons), and they may be constructed using various materials such as Silicon (Si), Indium Phosphide (InP), Silicon Nitride (SiN), or Gallium Arsenide (GaAs). Some PICs may combine multiple chip types with differing materials to achieve hybrid or heterogeneous interactions. Inside a PIC, the transmission of optical signals may be facilitated through the utilization of optical waveguides. Optical waveguides are further described in the definition section of the present disclosure.

[0119] Consistent with the disclosed embodiments, as LIDAR systems include electronic components such as the at least one processor of the at least one processing unit 120, a packaging approach may be used to supplement the capabilities of the PIC by enablingcombination of the PIC with other components, including electronic circuits. Integration of PICs with electronic Integrated Circuits (ICs) or Printed Circuit Boards (PCBs) by optimizing the interaction between photonic and electronic components may enable fully functional compact designs. In some embodiments, various elements of a LIDAR system module (such as the light source 112, modulation unit 114, scanning unit 116, or sensing unit 118) may be divided between a PIC and an IC or a PCB. For instance, in the case where light source 112 represents a laser source, the optical components of the laser (such as the optical cavity and gain medium) may be integrated within a PIC, while electronic components responsible for the laser's operation may be integrated into a PCB. A PIC and an IC or a PCB may be combined into a cohesive structure, possibly achieved by utilizing adhesive bonding to join these components together, or another mechanism with a similar outcome.Multiplexing / Scanning Modules For CW-LIDAR Systems

[0120] In the realm of CW-LIDAR systems, the multiplexing / scanning modules can contribute significantly to the system's functionality and performance. These components enable the LIDAR system to efficiently gather spatial information through the precise control of optical signal emissions and the scanning of light beams. The following sections are directed to different aspects of these modules, exploring their functions, mechanisms, and contributions to the overall operation of FMCW-LIDAR systems. Such electro-optical systems may incorporate the function of scanning unit 116 (more specifically of multiplexing / demultiplexing module 122) and sensing unit 118 described earlier. Additionally, these electro-optical systems, may be implemented on a PIC in conjunction with an IC or PCB.

[0121] In some embodiments, an electro-optical (demultiplexing) multiplexing / scanning module may include a plurality of transmitting optical waveguides. Each transmitting optical waveguide may be configured to transmit an optical signal. As previously discussed, an optical waveguide is a term used to describe any physical structure or medium intentionally designed to confine and direct the propagation of light. Optical waveguides may be integrated into photonic chips and can be defined by several parameters, as described in the definition section of the present disclosure. In some embodiments, each of the plurality of transmitting optical waveguides may share one or more identical parameters. For example, the plurality of transmitting optical waveguides may be composed of a common type of material, and may possess uniform rectangular cross-sections with common dimensions, resulting in similar electromagnetic modes. However, they may vary in terms oftheir physical lengths. Additionally, in some embodiments, the dimensions of the cross- sectional profiles of these transmitting optical waveguides may be within a similar order of magnitude as the wavelength of the optical signals they are designed to convey within the material of the waveguide, as further described in the definition section of the present disclosure. In some embodiments, the dimensions of the cross-sectional profiles of the transmitting waveguides may undergo a controlled transformation along their physical length according to a predefined pattern. For example, a transmitting optical waveguide may include a square-shaped cross-section that gradually transitions, in an adiabatic manner, to a rectangular cross-section along a linear profile. Alternatively, in some other embodiments, the cross-sectional profile of the transmitting waveguides may remain uniform and consistent along their entire physical length. Within the context of a CW-LIDAR system, each of the plurality transmitting waveguides may represent an independent transmission (Tx) channel.

[0122] In some embodiments, the electro-optical (demultiplexing) multiplexing / scanning module may include a plurality of receiving optical waveguides. Each of the plurality of receiving optical waveguides may be configured to receive an optical signal and associated with a corresponding one of the plurality of transmitting optical waveguides. In other words, each receiving waveguide is matched or paired with a transmitting waveguide and the number of receiving waveguides is equal to or greater than the number of transmitting waveguides. This arrangement ensures that each transmitting waveguide has at least one corresponding receiving waveguide. As for the transmitting optical waveguides, in some embodiments, the plurality of receiving optical waveguides may also exhibit one or more common characteristics (e.g., material, cross-section profile, electromagnetic modes, etc.). Additionally, in some other embodiments, the specific dimensions of the cross-sectional profiles of these receiving optical waveguides may align closely with the wavelength of the optical signals they are intended to carry / receive within the waveguide material. In yet further embodiments, the cross-sectional profiles of the plurality of receiving waveguides may change in a controlled manner along their physical length according to a predefined pattern or remain constant and consistent along their entire physical length. Within the context of a CW-LIDAR system, each of the plurality receiving waveguides may represent an independent transmission (Rx) channel.

[0123] In some embodiments, the plurality of transmitting optical waveguides and the plurality of receiving optical waveguides may share one or more identical parameters. For example, each pair of transmitting and receiving waveguides could be constructed from identical materials and possess similar cross-sectional profiles, with uniform dimensions thatyield identical electromagnetic modes. However, they may vary in terms of their overall physical lengths. Additionally, in some embodiments, each of the plurality of transmitting optical waveguides and / or each of the plurality of receiving optical waveguides may operate as single mode waveguides. In other words, each of the above-mentioned waveguides may only support a single electromagnetic mode within the range of optical wavelengths relevant to the transmitted or received optical signals. For example, in the context of waveguides characterized by rectangular cross-sections, only the primary fundamental TE Mode, denoted as TEoo, may be sustained.

[0124] In some embodiments, the electro-optical (demultiplexing) multiplexing / scanning module may include an optical distribution matrix comprising at least one input and a plurality of outputs. Each of these outputs is coupled to one of the plurality of transmitting optical waveguides. In such a case, the number of outputs from the optical distribution matrix matches the number of transmitting waveguides. In some embodiments, the optical distribution matrix may be configured to selectively distribute an optical output signal generated by a light source to the plurality of transmitting optical waveguides. The term "selectively distributing" encompasses the versatile capability of the optical distribution matrix to route an optical signal to its outputs in multiple ways: simultaneously, individually, or in an ordered sequence (e.g., one after the other), based on specific requirements. This means it may distribute the optical signal to all outputs at once or selectively direct the optical signal to particular outputs, depending on the operational needs. Moreover, the optical distribution matrix may possess the capacity to finely control the amount of optical power allocated to each output. For instance, it may concentrate the incoming optical power from its input onto a single output or distribute it (evenly or not) across multiple outputs as needed. Alternatively, in another example, the optical distribution matrix may attenuate the incoming optical signal, reducing its optical power, and distributing the attenuated signal across one or more outputs. In essence, the optical distribution matrix may serve the role of an optical demultiplexer, i.e., it has the function of splitting or demultiplexing optical signals as necessary.

[0125] In some embodiments, the electro-optical (demultiplexing) multiplexing / scanning module may include an electro-optical reception matrix comprising a plurality of inputs. Each of these inputs is coupled to one of the plurality of receiving optical waveguides and associated with one of the plurality of outputs of the optical distribution matrix. Furthermore, the electro-optical reception matrix may include at least one output. To clarify, each input may be matched or paired with a receiving waveguide and the number ofinputs may be equal to the number of receiving waveguides (i.e., equal to or greater than the number of transmitting waveguides / number of inputs from the optical distribution matrix). In some embodiments, the electro-optical reception matrix may be configured to mix, for each particular receiving waveguide among the plurality of receiving waveguides, a portion of the optical output signal generated by the light source with the optical signal received by the particular receiving waveguide to provide a plurality of interference signals, one for each of the plurality of receiving waveguides; generate a plurality of electronic signal outputs, one for each of the plurality of interference signals; and sum all of the plurality of electronic signal outputs to provide a summed signal to the at least one output. In other words, three steps may be performed by the electro-optical reception matrix. First, for each specific receiving waveguide among the plurality of receiving waveguides, the electro-optical reception matrix combines / mixes a portion of the optical output signal generated by the light source with the optical signal received by that particular receiving waveguide (Rx signal). This combination step creates a set of interference signals, with one signal generated for each of the multiple receiving waveguides. Then, after mixing, the electro-optical reception matrix generates a corresponding set of electronic signal outputs, with one electronic signal output produced for each of the interference signals created in the previous step. These electronic signal outputs represent the interference patterns resulting from the interaction between the incoming optical signals conveyed by the receiving waveguides and the portions of the optical output signal from the light source. Finally, the electro-optical reception matrix sums together all of these electronic signal outputs. This summation process aggregates the information from each receiving waveguide's interference signal. The result is a summed signal that is then directed to the at least one output of the electro-optical reception matrix. In essence, this three-step process enables the reception matrix to extract and process information from multiple receiving waveguides, combining optical and electronic signals to provide a coherent and consolidated output signal. As such, the electro-optical reception matrix may serve the role of an electro-optical multiplexer, i.e., it has the function of combining different optical signals into one summed electrical output.

[0126] Fig. 2A is a diagrammatic illustration of an example implementation of an electro-optical (demultiplexing) multiplexing / scanning module, consistent with some embodiments of the present disclosure. This diagrammatic illustration encompasses the electro-optical multiplexing / scanning module 200, along with a light source 112 configured to deliver an optical output signal. As shown, module 200 incorporates an optical distribution matrix 210, a plurality of transmitting waveguides (202-1 through 202-4, also labelled astransmission channels Txi through TX4), an electro-optical reception matrix 220, and a plurality of receiving waveguides (204-1 through 204-4, also labelled as reception channels Rxi through RX4). In this illustration, waveguides (both for transmitting and receiving purposes), are depicted as continuous black lines.

[0127] In this example, the optical distribution matrix 210 is equipped with a single input labelled as 214 and four distinct outputs designated as 212-1 through 212-4. These outputs (212-1 through 212-4) are directly coupled to individual transmitting optical waveguides (202-1 through 202-4), as represented by black diamonds indicating the couplings. However, in some embodiments, each output (212-1 through 212-4) of the optical distribution matrix 210 may be coupled to one of the plurality of transmitting optical waveguides (202-1 through 202-4) through at least one electro-optical component. As used herein, an electro-optical component refers to any kind of device or element that may actively manipulate, modulate, or change the state of optical signals using an electrical control. For example, in some embodiments, the at least one electro-optical component may be a polarization beam splitter. The function of optical distribution matrix 210 is to selectively distribute an optical output signal generated by light source 112 to the plurality of transmitting optical waveguides (204-1 through 202-4). Accordingly, in this depiction, the light source 112 is directly linked to the input 214 of the optical distribution matrix 210. Nevertheless, in some embodiments, light source 112 may be coupled to the at least one input 214 of the optical distribution matrix 210 through at least one optical or electro-optical component. For example, light source 112 may be coupled to input 214 through a variable attenuator configured to modulate the optical power of the output optical signal delivered by light source 112.

[0128] In parallel, as shown in Fig. 2A, the electro-optical reception matrix 220 includes four distinct inputs, labelled as 224-1 through 224-4, with each input being directly linked to individual receiving waveguides (204-1 through 204-4), and possessing a single output, designated as 222. As previously explained, the function of the reception matrix 220 is to perform several tasks: firstly, it mixes, for each specific receiving waveguide among the set of receiving waveguides (204-1 through 204-4), a portion of the optical output signal generated by the light source 112 with the optical signal received by the particular receiving waveguide. This process yields a plurality of interference signals, with one interference signal generated for each of the receiving waveguides. Subsequently, the reception matrix 220 generates a series of electronic signal outputs, producing one electronic signal output corresponding to each of the generated interference signals. Finally, it aggregates all of theseelectronic signal outputs through summation to produce a single summed signal, which is then directed to the at least one output 222 of the matrix. Once delivered at the at least one output 222, the summed signal may be directed and processed by at least one processor (e.g., the at least one processor of processing unit 120).

[0129] It is to be appreciated that the electro-optical multiplexing / scanning module 200 depicted in Fig. 2A is just one example, and its arrangement and composition may be subject to variation. For instance, in the configuration shown in Fig. 2A, the number of transmitting waveguides matches the number of receiving waveguides. However, in alternative embodiments, the number of receiving waveguides may exceed the number of transmitting waveguides. Likewise, while Fig. 2A shows four distinct transmitting waveguides, the actual number of transmitting waveguides may vary. For instance, in certain embodiments, the number of transmitting waveguides could be any other suitable power of 2 (e.g., 2, 8, 16, 32...) or any other natural number greater than one (3, 6, 10...). Moreover, while Fig. 2A illustrates only one side of each waveguide (both transmitting and receiving) being linked to a specific entity (such as distribution matrix outputs or reception matrix inputs), it is important to recognize that the other side of these waveguides may be connected to various other optical or electro-optical components (not illustrated in Fig. 2A). For instance, each transmitting waveguide (202-1 through 202-4) and receiving waveguide (204- 1 through 204-4) may be coupled to a coupler, such as a grating coupler or an edge coupler, configured to either emit or collect an optical signal conveyed by the respective transmitting or receiving waveguide. In an alternative scenario, each transmitting waveguide (202-1 through 202-4) may be connected to an optical splitter, such as a directional coupler, to divert a portion of the optical signal being transmitted. This diverted optical signal may then be used for estimating the optical power circulating within these waveguides through measurements conducted by photodiodes, enabling monitoring and control of optical power levels within each transmitting waveguide / transmission channel.

[0130] In some embodiments, the portion of the optical output signal generated by the light source (which is combined by the reception matrix 220 with the optical signal received by each specific receiving waveguide) may be supplied via a local oscillator light path. As used herein, a "local oscillator light path" refers to a dedicated optical path or channel that carries a reference optical signal (here a portion or a local copy of the output optical signal generated by light source 112), often referred to as the "local oscillator" or LO signal. A local oscillator light path may include various configurations; for instance, it may be realized through a waveguide coupled to any appropriate component within the electro-opticalmultiplexing / scanning module 200 and the reception matrix 220. This waveguide is configured to transmit a portion of the optical signal outputted by the light source 112, effectively embodying the local oscillator function. Further details regarding local oscillator light paths are provided in the definition section of the present disclosure.

[0131] In some embodiments, the local oscillator light path may be directly coupled to the light source. For example, Fig. 2B illustrates a configuration wherein a local oscillator light path 206 is directly coupled to light source 112 and electro-optical reception matrix 220 via for example a dedicated local oscillator input. Once the portion of the optical signal generated by the light source 112 (referred to as the LO signal) is transmitted through the local oscillator light path 206, the reception matrix 220 can be further configured to selectively distribute the LO signal to each of its inputs (224-1 through 224-4). This distribution enables subsequent mixing with the optical signal received by each specific receiving waveguide (204-1 through 204-4). Alternatively, the reception matrix 220 may divide the LO signal across the various outputs, either evenly or with variations, before proceeding with the mixing operation. It is to be appreciated that although Fig. 2B depicts the local oscillator 206 being connected to reception matrix 220 through a dedicated local oscillator input, local oscillator light path 206 may be coupled to reception matrix 220 in alternative ways. For instance, it may be linked to one of the multiple inputs, such as 224-1 through 224-4, within reception matrix 220.

[0132] In some other embodiments, the local oscillator light path may be directly coupled to at least one of the plurality of outputs of the optical distribution matrix. To illustrate, local oscillator light path 206 may be linked to output 212-1 of the optical distribution matrix 210 and then further connected to reception matrix 220, either through a dedicated local oscillator input or via one of the available inputs (224-1 through 224-4) within the reception matrix 220. In some other embodiments, the local oscillator light path may be directly coupled to at least one of the plurality of transmitting optical waveguides. For example, local oscillator light path 206 may be coupled to transmitting waveguide 202-1. Subsequently, it may establish a connection with the reception matrix 220, either through a dedicated local oscillator input or by utilizing one of the accessible inputs (224-1 through 224-4) within the reception matrix 220.

[0133] In some embodiments, each of the plurality of inputs of the electro-optical reception matrix may have a local oscillator light path coupled to the associated output of the optical distribution matrix. This situation is depicted in Fig. 2C, wherein each of the plurality of inputs (224-1 through 224-4) of the reception matrix 220 is coupled to the associatedoutput of distribution matrix 210 via a distinct local oscillator light path (206-1 through 206- 4). Alternatively, in some other embodiments, each of the plurality of inputs of the electro- optical reception matrix may have a local oscillator light path coupled to the transmitting waveguide coupled to the associated output of the optical distribution matrix. In all the aforementioned configurations, the objective of the one or more local oscillator light paths remains consistent, which is to deliver a portion of the optical signal generated by light source 112 (LO signal). This function is carried out regardless of whether the one or more local oscillator light paths are directly connected to the light source 112, the different outputs (212-1 through 212-4) from distribution matrix 210, or the multiple transmitting waveguides (202-1 through 202-4). The reason for this consistency is that neither distribution matrix 210 nor the transmitting optical waveguides (202-1 through 202-4) introduce any substantive alterations (e.g., frequency or amplitude modulation) of the electromagnetic properties of the optical signal generated by light source 112. The signal generated by light source 112 maintains its consistency even after traversing the distribution matrix 210. While the optical power may undergo alterations, the overall signal characteristics, including modulation patterns like the one depicted in Fig. 1 A, are preserved following its passage through the distribution matrix 210.

[0134] It is to be appreciated that in the above-mentioned configurations, the transmission (Txi, Tx2, Tx3, TX4) and reflection channels (Rxi, Rx2, Rx3, RX4) are precisely synchronized. Each electronic signal output associated with a reflection channel (Rxi, i denoting a particular reflection channel) is proportional to the interference signal (Rxi * LO). Consequently, when the optical distribution matrix 210 is configured to output an optical output signal for a particular transmission channel i (Txi), the local oscillator (LO) signals for every other channel different from i are either equal to or close to zero. Accordingly, only an interference signal for the i-th reception channel (Rxi) will be generated. Therefore, Txi and Rxi may remain synchronized throughout the process. This approach may offer several advantages, including a reduced number of components, lower signal losses (no excess loss due to multiplexing), and compatibility with partially switched outputs,

[0135] In some embodiments, the optical distribution matrix 210 may be based on a plurality of optical switches arranged in a tree structure. When these optical switches are arranged in a tree structure with a hierarchical layout involving multiple layers, it allows for an expansion of the number of potential outputs, enhancing the versatility and scalability of optical distribution matrix 210. Within a tree structure, optical switches may establish direct connections, where the output of one switch is directly linked to the input of a subsequentswitch. Alternatively, they may also form indirect connections, such as through the utilization of optical waveguides, to facilitate signal routing between switches. Further details on optical switches are provided in the definition section of the present disclosure.

[0136] Fig. 3A is an exemplary illustration of an optical distribution matrix 210 that relies on a set of optical switches organized within a tree structure. This tree structure consists of three 2 x 2 switches (302-1, 302-2, and 302-3), although in each of these optical switches, only one of the two inputs is actively employed. These switches, 302-1, 302-2, and 302-3, are arranged across two layers, with the initial layer housing a single switch, 302-1, and the subsequent layer accommodating the remaining two switches, 302-2 and 302-3. These switches are interconnected by optical waveguides represented as bold continuous lines. This structured arrangement facilitates the selective distribution of optical signals, allowing them to be routed from a single input to four distinct outputs. To accommodate a different number of desired outputs, the structure illustrated in Fig. 3 A may be expanded accordingly. For instance, if eight outputs are required, the tree structure may be augmented by adding a third layer, which includes four additional switches, creating therefore eight distinct outputs.

[0137] In some embodiments, the optical switches (302-1, 302-2, and 302-3) employed in the tree structure of the distribution matrix 210, may include at least one of Mach-Zehnder interferometers, micro-ring resonator, electro-optic switches, thermo-optic switches, or a combination thereof. Figs. 3B-E illustrate examples of the previously mentioned switch architectures. These switches all feature a single input signal ("In") delivered to a single input and two output signals ("Outi" and "Out2") provided at separate outputs. Fig. 3B showcases a Mach-Zehnder interferometer 310b situated between two passive optical splitters, denoted as 308b-l and 308b-2 (e.g., 3dB optical splitters). The overall structure is formed by two waveguides, 306b-l and 306b-2. This structure corresponds to a type of electro-optic switch that takes advantage of the changes in refractive index of a material in response to an applied electric field. By applying an electrical field to the electrodes of this structure (304b), a phase difference is induced, ultimately leading to the partial or total redirection of the input optical signal toward one of the two outputs. Fig. 3C illustrates a micro-ring 312 positioned between and evanescently coupled to two waveguides, 306c-l and 306c-2. This configuration also functions as an electro-optic switch, taking advantage of the refractive index change of the ring 312 with an applied electric field (via a current provided to electrode 304c) to control signal routing. Fig. 3D presents an active optical splitter 3 lOd formed by two waveguides, 306d-l and 306d-2. Similar to the previous examples, this switch relies on the electro-optic effect. By applying an electrical field via theelectrodes (304d), a phase shift is induced, facilitating partial or complete redirection of the input optical signal. Fig. 3E, in contrast, employs a different mechanism and leverages the variation in the refractive index of a material with temperature. The structure depicted here resembles that of Fig. 3B, featuring a Mach-Zehnder interferometer 3 lOe flanked by two passive optical splitters, 308e-l and 308e-2, and formed by two waveguides, 306e-l and 306e-2. By applying an electrical current to the resistor 314, changes in temperature within one of the two arms of the Mach-Zehnder interferometer 3 lOe induce a phase variation, resulting in the partial or total redirection of the input optical signal toward one of the optical outputs. It is to be appreciated that thermo-optic switches, such as the one in Fig. 3E, tend to operate more slowly due to the thermal inertia of the structure compared to electro-optic switches. This limitation may impact their applicability in certain scenarios. Electro-optic switches may enable fast (analogue) switching procedures.

[0138] As mentioned above, the role of electrodes 304b, 304c, and 304d, as well as the role of resistor 314, is to create a phase shift based on the electro-optic or thermo-optic effect, respectively. The electrodes 304b, 304c, and 304d are employed in the Mach-Zehnder interferometer and micro-ring resonator configurations to induce a phase difference by altering the refractive index of the material when an electric field is applied. Similarly, resistor 314 in the thermo-optic switch configuration is used to induce a phase variation by changing the temperature, which in turn affects the refractive index. Accordingly, these components may be characterized as phase shifters. In some embodiments, phase shifters configured to modify the refractive index by the electro-optic effect, such as electrodes 304b, 304c, and 304d, may include a PN junction (also referred to as a diode junction). This PN junction may be directly connected via a substrate to a portion of the active optical splitter (e.g., arms of the Mach-Zehnder interferometer 310b, portions of waveguides 306d-l and 306d-2, portion of ring 312). In some embodiments, the PN junction may be forward biased (P side of the junction connected to the positive terminal and N side of the junction connected to the negative terminal) or reverse biased (P side of the junction connected to the negative terminal and N side of the junction connected to the positive terminal). A reverse-biased PN junction will create a carrier depletion zone in the portion of the active optical splitter, inducing thereby an electric field and causing a change in the refractive index through the electro-optic effect. A forward-biased PN junction in association with a thin insulator layer in the middle of the junction, will create a carrier accumulation zone in the portion of the active optical splitter, inducing thereby an electric field and causing a change in the refractive index through the electro-optic effect. Both forward-bias and reverse-bias PN junctions are suitablethe high-speed modulation / phase shifting (higher than thermal control) due to majoritycarrier-based operation, however, reverse-bias junctions tend to present more loss due to free carrier absorption.

[0139] In some embodiments, the optical distribution matrix 210 may be based on a bus waveguide coupled to a plurality of micro-ring switches, each micro-ring switch being coupled with a corresponding one of the plurality of transmitting waveguides. In this scenario, the tree structure is replaced by a bus structure, and the transmitting waveguides extend into the distribution matrix. Consequently, each output (212-1 through 212-4) from the distribution matrix 210 may be viewed as forming a single entity with the associated transmitting waveguide. Fig. 3F depicts such an approach, where the optical distribution matrix 210 includes four micro-ring switches (312-1 through 312-4). Each of these microring switches is linked to a bus waveguide 316 and is correspondingly connected to an associated transmitting waveguide (202-1 through 202-4). The black arrows indicate potential routes for the output optical signal delivered by light source 212. Furthermore, in some embodiments, the micro-ring switches may be electronically controlled. As shown in Fig. 3F, similar to the configuration depicted in Fig. 3C, the introduction of electrical currents to the electrodes (304-1 through 304-4) will induce a corresponding phase shift in the optical signal circulating in the optical rings (312-1 through 312-4), enabling selective routing (either complete or partial) of the output optical signal delivered by the light source 112 towards the plurality of transmitting waveguides (202-1 through 202-4).

[0140] In some embodiments, the optical distribution matrix 210 may be based on a plurality ofMEMS switches. MEMS switches, short for Micro-Electro-Mechanical Systems switches, refer to any kind of devices that employ microscale mechanical components, often at the micron or sub-micron scale, along with electrical control / actuation mechanisms to manipulate optical signals. They may redirect or modify the path of optical signals through precise movements of their microscale elements. There are two main types ofMEMS switches: Micromirror-based MEMS switches, which employ miniature mirrors adjusted with precision through electrostatic forces to redirect optical signals, and Microbeam-based MEMS switches that use small beams or waveguides moved electronically to reconfigure optical paths within the switch. MEMS switches offer dynamic and precise control over optical signal routing and find valuable applications in optical networks and related fields.

[0141] Fig. 3G illustrates a system based on the above-described approach. In this illustration, the optical distribution matrix 210 encompasses several Micromirror-based MEMS switches (322-1 through 322-4). These switches, operating in free space, necessitatethe presence of couplers (318 and 320-1 through 320-4) to either transmit an optical signal from a waveguide into free space or collect and confine an optical signal propagating in free space into an optical waveguide (e.g., transmitting waveguides 202-1 through 202-4). Additionally, the distribution matrix includes mirrors (represented as black rectangles, denoted as 324) strategically placed to deflect and redirect the incoming optical signal from light source 112 towards the array of MEMS switches (322-1 through 322-4). Each MEMS switch may assume either an "On" state (indicated by a filled rectangle, exemplified by switch 322-2), where it interacts with a light beam by reflecting or splitting the optical signal, or an "Off1state (depicted as an empty rectangle, for instance, switches 322-1, 322-3, and 322-4), where it remains inactive and does not obstruct the optical path. In the provided example, complete redirection of the incoming optical signal toward the second transmitting waveguide, 202-2, is achieved using MEMS switch 322-2, essentially functioning as a perfect mirror, in conjunction with coupler 320-2. Nonetheless, the incoming optical signal may also be distributed among the various outputs of the distribution matrix. In this scenario, miniature beam-splitters are incorporated into the switches rather than mirrors. For instance, if MEMS switches 322-1 through 322-4 are configured with 100:0, 50:50, 66:33, and 75:25 beam splitters, respectively, and are all in the "On" state, the incoming optical signal may be evenly split across the four outputs, 212-1 through 212-4. The arrangement and quantity of MEMS switches may be adjusted based on the desired number of outputs for the distribution matrix 210.

[0142] In some embodiments, the optical distribution matrix 210 may be based on a wavelength demultiplexer and each transmitting waveguide is associated with a specific wavelength range. As used herein, a wavelength demultiplexer refers to any type of optical device engineered to efficiently separate or split optical signals into distinct outputs (also referred to as channels) based on their individual wavelengths. Wavelength demultiplexers typically feature a single input port, where an optical signal containing multiple wavelengths enters the device. The device then disperses this combined signal into multiple output ports, each corresponding to a specific wavelength or wavelength range. This separation is achieved by exploiting the distinct properties of different wavelengths of light. Wavelength demultiplexers come in both passive and active forms. Passive WDEMUXs do not require external power sources or control signals to perform their function. They rely on the inherent properties of optical materials and structures to separate wavelengths. Active WDEMUXs, on the other hand, rely upon external control and power sources (e.g., electric control signals) to manipulate optical signals actively. These active versions may be used in scenarios wheredynamic control and precise signal routing are desired. WDEMUXs may be based on a variety of different technologies, such as gratings, waveguides and couplers, micro-cavities or photonic crystals.

[0143] Fig. 3H represents an embodiment based on this alternative approach to optical signal distribution. In this example, the optical distribution matrix 210 is directly implemented as a wavelength demultiplexer (WDEMUX), with the input and plurality of outputs of distribution matrix directly corresponding 210 to the input and outputs of the WDEMUX. The incoming optical signal emitted by light source 112, which contains wavelengths within a specified range labelled [Xo, X4], is effectively separated into four distinct optical signals. Each of these optical signals corresponds to a unique and nonoverlapping wavelength range, denoted as [Xo, Xi[, [Xi, X2 [X2, Xs[, and [X3, X for transmitting waveguides 201-1, 202-2, 202-3, and 202-4 respectively. This arrangement ensures that each output channel carries optical signals within a specific wavelength band, allowing for precise wavelength-based signal distribution and management.

[0144] In some embodiments, the optical distribution matrix 210 may be based on a combination of active optical switches and passive optical switches. As mentioned, passive optical switches operate without the need for external power sources or control signals, whereas active optical switches require external control and power sources for their operation. Active optical switches excel in scenarios where dynamic control and precise signal routing are demanded but tend to be more expensive, require more meticulous nanofabrication, and are larger in size. Consequently, in situations where a large number of outputs for the optical distribution matrix is desired, using only active switches may result in increased cost and footprint. In contrast, employing a combination of passive and active optical switches can enable an increase in the number of outputs while maintaining a moderate size and reasonable cost. By strategically incorporating passive switches, which do not require power or control signals, the overall distribution matrix may be made more cost- effective and compact. At the same time, the presence of active optical switches ensures that dynamic and precise signal routing can still be achieved where necessary. This hybrid approach leverages the benefits of both types of switches, optimizing the optical distribution matrix for both scalability and performance.

[0145] The combination of active and passive optical switches may take various forms to optimize the performance and scalability of the optical distribution matrix. For example, in some embodiments, the optical distribution matrix 210 may include a plurality of active optical switches arranged in a tree structure, and each output of the active opticalswitches tree structure may be connected to one or more passive optical switches or splitters. This arrangement may enable the active switches to handle the dynamic and precise routing of signals at the upper levels of the tree structure. The passive optical splitters, connected to the outputs of the active switches, may then further distribute the signals without requiring additional power or control signals. This setup may maximize the number of outputs while minimizing the overall cost and size of the distribution matrix. The one or more optical switches may be further arranged in a tree structure.

[0146] Alternatively, in some other embodiments, a different paradigm can be employed where the optical distribution matrix may be based on a plurality of passive optical switches or splitters, and each output of the passive optical switches or splitters tree structure may be connected to one or more active optical switches. This approach may leverage the inherent simplicity and cost-effectiveness of passive components for the initial distribution of signals. The active switches, positioned at the endpoints of the distribution paths, may enable adjustments and control over the final signal distribution.

[0147] Fig. 31 illustrates a system based on the above-described approaches. In this illustration, the optical distribution matrix 210 includes a plurality of active optical switches 302-1 through 302-3 (e.g., Mach-Zehnder interferometers, micro-ring resonators, electrooptic switches, thermo-optic switches, etc.) arranged in a tree structure 240 akin to the one presented in Fig. 3 A. Each output 242-1 through 242-4 of the active optical switch tree structure 240 is connected to a passive optical switch 332-1 through 332-4. Each of these passive optical switches 332-1 through 332-4 includes one input and three outputs: outputs 202-11 through 202-13 for passive optical switch 332-1, outputs 202-21 through 202-23 for passive optical switch 332-2, outputs 202-31 through 202-33 for passive optical switch 332-3, and outputs 202-41 through 202-43 for passive optical switch 332-4. This configuration brings the total number of outputs of the optical distribution matrix to twelve. This arrangement combining use of active and passive optical switches in a hierarchical structure may enhance the optical distribution matrix’s versatility, efficiency, and cost-effectiveness.

[0148] In the previously mentioned embodiments where distribution matrix 210 utilizes active components for selective signal distribution, control signals, typically in the form of electric control signals, may be provided to operate distribution matrix 210. These demultiplexing control signals may be provided via various electrical pathways / connections / contact points within distribution matrix 210, and the management and operation of distribution matrix 210 may be overseen by at least one processor or processing unit 120, as discussed earlier. As previously noted, processing unit 120 may be located on aPCB adjacent to a PIC, where the electro-optical multiplexing / scanning module is implemented. This setup allows for efficient control and coordination of the active components within the distribution matrix, ensuring precise signal distribution as needed. In some embodiments, a monitoring unit may be connected to optical distribution matrix 210 and may be configured to provide feedback signals to control the operations of optical distribution matrix 210. For example, in some embodiments, the monitoring unit may provide a feedback signal to control the selective distribution of the optical output signal generated by the light source to the plurality of transmitting optical waveguides. Such a monitoring unit may be included in processing unit 120, or may be internal to electro-optical multiplexing / scanning module 200. Further example embodiments regarding the monitoring unit are provided in subsequent sections.

[0149] In some embodiments, the electro-optical reception matrix 220 may include, for each input (224-1 through 224-4) at least one (optical) coupler / optical splitter and at least one photodetector. As employed within the electro-optical reflection matrix 220, optical couplers may be responsible for the mixing of the portion of the portion of the optical output signal generated by the light source with the optical signal received by the receiving waveguides, leading to the generation of interference signals. A large variety of technologies and designs may be used for couplers. For example, in some embodiments, the at least one coupler may include at least one of a directional coupler (exemplary directional coupler are illustrated in Figs. 3B, 3D and 3E) or a multimode interferometer (MMI). Further details regarding optical couplers / splitters are provided in the definition section of the present disclosure. Within the electro-optical reception matrix, the photodetectors are responsible for generating a plurality of electronic signal outputs corresponding to the plurality of interference signals. Further details regarding photodetectors are provided in the definition section of the present disclosure.

[0150] In some embodiments, the at least one photodetector may include a balanced photodetector. When the at least one balanced photodetector is used in conjunction with the at least one coupler, more specifically a 50:50 combiner, a beat frequency between two incoming optical signals (e.g., LO signal and Rx signal) to the coupler may be determined. The coupler mixes optical signals from two input branches and distributes them to two photodetectors. By subtracting the detectors’ electrical signals, common-mode components are cancelled, leaving only the differential signal, which carries the beat frequency between the incoming signals, such as the Rx and LO signals. Further details regarding balanced photodetectors are provided in the definition section of the present disclosure.

[0151] In some embodiments, the electro-optical matrix 220 may include at least one trans-impedance amplifier (TIA). A trans-impedance amplifier refers to an electronic circuit or component designed to convert a current signal, (e.g., generated by a photodetector in response to an incoming optical signal - photocurrent), into a voltage signal. The primary function of a TIA is to amplify this “weak” current signal while converting it into a more manageable and measurable voltage signal, suitable for further electronic processing, analysis, or data transmission. TIAs may be used in optical communication systems, photodetection applications, and other scenarios where accurate amplification and conversion of optical signals into electrical signals are sought.

[0152] In some embodiments, the summing operation performed by the electro- optical matrix 220 on any or all of the plurality of electronic signal outputs may include short-circuiting the plurality of electronic signal outputs currents into the at least one trans- impedance amplifier to provide a summed voltage signal to the at least one output 222. Fig. 4A depicts an exemplary electro-optical reception matrix 220 configured similarly to the one shown in Fig. 2C. In this close-up view, each of the multiple inputs of the electro-optical reception matrix (224-1 through 224-4) is equipped with a local oscillator light path (206-1 through 206-4) that is linked to the respective output of the optical distribution matrix (212-1 through 212-4). Notably, each input (224-1 through 224-4) is split, allowing it to accommodate both the LO signal and the Rx signal within two distinct sub-inputs. This electro-optical reception matrix 220 incorporates, for each input, at least one optical coupler (402-1 through 402-4) and at least one photodetector (404-1 through 404-2) directly coupled to the optical coupler. In this specific example, the optical couplers (402-1 through 402-4) are configured as passive 50:50 (e.g. 3dB) directional couplers, while the photodetectors (404-1 through 404-4) take the form of balanced photodiodes. Each coupled directional coupler / balanced photodiode pair (402-i / 404-i, with 'i' representing a particular input) is designed to produce an electronic signal output with a frequency equal to the beat frequency between the associated LOi and Rxi optical signals. The electronic signal outputs generated by each of these pairs are subsequently short-circuited and directed into TIA 406, which is configured to convert the summed current signal into a summed voltage signal. This summed voltage signal is then transmitted to the at least one output 222 of the electro-optical distribution matrix 220.

[0153] In some embodiments, the summing operation performed by the electro- optical matrix 220 on the plurality of electronic signal outputs may include converting the plurality of electronic signal outputs currents into a plurality of electronic signal outputvoltages using the at least one trans-impedance amplifier and summing electronic signal output voltages to provide a summed voltage signal to the at least one output. Fig. 4B represents an embodiment including such an alternative approach to the electro-optical distribution matrix 220 configuration. The overall architecture of the matrix remains quite similar to that in Fig. 4A, with the distinction that in this setup, each input (224-1 through 224-4) is linked to a dedicated TIA (406-1 through 406-4). These TIAs are specifically designed to convert the individual current output from the balanced photodiodes (404-1 through 404-4) into individual voltage output signals. The generated voltage signals from each input are then combined, using a summing amplifier configuration in this example, to produce a summed voltage signal. This summed voltage signal is subsequently directed to the at least one output 222 of the electro-optical distribution matrix 220. It is to be appreciated that while a summing amplifier circuit is illustrated here, various electronic circuit configurations may be employed to achieve the voltage summing operation.

[0154] In some embodiments, the summing operation performed by the electro- optical matrix 220 on the plurality of electronic signal outputs may include a combination of the two above-described operations. Each of these methods may offer advantages. For instance, in the short-circuiting configuration, the need for individual dedicated TIAs is eliminated, reducing the overall number of electronic components required. Conversely, the voltage summing configuration with individual TIAs allows for better control of gain and signal conditioning. A hybrid approach may combine the strengths of both methods, providing a flexible and efficient solution for signal summation within the electro-optical matrix 220. For example, in some embodiments, the plurality of Rx channels may be divided into different subsets based on system requirements. Within each subset, the currents generated by the balanced photodiodes may be short-circuited and individually converted into voltage signals by dedicated TIAs . Once these voltage signals are obtained for each subset, they may be further summed together to create the summed voltage output.

[0155] In some embodiments, each electro-optical reception matrix input may be split before the at least one coupler to generate complex I-Q demodulation. In other words, each input of the electro-optical reception matrix may be divided into two sub-channels, I and Q, to enable complex I-Q demodulation. Complex I-Q demodulation is a signal processing technique used to separate an incoming signal into its in-phase (I) and quadrature (Q) components. In this configuration, both the LO signal and the Rx channel signal are divided into two parts. For the LO signal, one part goes directly to a coupler, while the other part is directed to a phase shifter configured to introduce a 90° phase shift before going to anothercoupler. Similarly, the Rx signal is split into two portions. For each input, the electro-optical reception matrix includes therefore two couplers (splitter) dedicated to splitting the LO and Rx signals, two couplers (mixers) dedicated to mixing these split signals (one pair for each sub-channel I and Q), and two photodetectors dedicated to generating electronic signals for both the I and Q components.

[0156] Fig. 4C provides a close-up view of the first reception channel Rxi of an electro-optical reception matrix 220 employing this complex I-Q demodulation technique. A first optical coupler / splitter (e.g., a directional coupler with a 50:50 split ratio) 402-11 splits the LO signal into two parts, with one part sent directly to a first mixer 402-13. The other part is directed to a phase shifter 410, which introduces a 90° phase shift before being sent to a second mixer 402-14. A second optical coupler / splitter (also a directional coupler with a 50:50 split ratio) 402-12 splits the Rx signal into two parts, each part being directed to the first 402-13 and second mixer 402-14. Each pair of split signals (one from LO and one from Rx) is consequently mixed, one pair by mixer 402-13 for the I sub-channel and the second pair by mixer 402-14 (for the Q sub-channel) to create two distinct interference signals. Finally, two balanced photodetectors, 404-11 and 404-12, generate electronic signal outputs (e.g., currents) corresponding to these interference signals. These electronic signal outputs may be further processed (e.g., short-circuited, subtracted, converted into voltage signals via a TIA. . .) as needed, depending on the specific detection approach employed. Complex I-Q demodulation in an FMCW LIDAR system may effectively resolve ambiguities that may arise when determining the beat frequency of received signals. This capability enables the system to provide more precise measurements of both range (distance) and Doppler shift (velocity) for target objects, enhancing the accuracy of the LIDAR system's output data.

[0157] Alternatively, in some embodiments, the electro-optical reception matrix may include for each input an optical hybrid configured to perform complex IQ demodulation. Specifically, the electro-optical reception matrix may include for each input a 90° optical hybrid. Further details regarding optical hybrids are provided in the definition section of the present disclosure. Within the electro-optical reception matrix, for complex IQ demodulation, the primary signal provided at one of the two inputs of the 90° optical hybrid is the Rx signal, while the secondary signal is the LO signal. In this context, the output signal of the 90° optical hybrid includes components like Rx+LO, Rx-LO, Rx+jLO, and Rx-jLO. Once outputted these signals may be detected. For example, they may be detected by a pair of balanced photodetectors, such as 404-11 and 404-12 illustrated in Fig. 4C. Optical hybrids may encompass various optical components, including optical splitters, combiners, phaseshifters, or interferometers. To illustrate, a structural example of a 90° optical hybrid (420) is depicted in Fig. 4C, with the actual boundaries of the optical hybrid delineated by a black dashed line. In some embodiments, the 90° optical hybrid may incorporate adjustability, for example by including one or more optical phase tuners.

[0158] It is to be appreciated that the various embodiments described in this disclosure revolve around an optical distribution matrix 210, which includes an optical input and optical outputs, and may also incorporate electrical control or feedback signals when active elements are employed. In contrast, the electro-optical reception matrix 220 is configured with optical inputs and an electrical output, along with the incorporation of optical control signals (LO signals). In some embodiments, the dual optical distribution matrix 210 / electro-optical reception matrix 220 architecture may be utilized for various monitoring and / or calibration procedures.

[0159] Calibration procedures may involve using feedback from measurements of each receiving waveguide (e.g., 204-1 to 204-4) to detect non-zero electronic signal outputs from inactive Rx channels where a zero electronic signal output is expected. Such Rx channels may be tuned in the optical distribution matrix 210 to reduce the measured electronic signal output to zero. In order to detect non-zero electronic signal outputs, a dedicated mechanism to monitor the electronic signal output from each receiving waveguide (e.g., 204-1 to 204-4) may be added for each receiving waveguide (e.g., 204-1 to 204-4). This detection of non-zero electronic signal outputs may be beneficial in embodiments wherein the plurality of electronic signal outputs currents of the electro-optical reception matrix 220 are short circuited before being fed to a TIA (e.g., as shown in FIG. 4A).

[0160] In some embodiments, the electro-optical reception matrix 220 may further include, for each input, at least one resistor connected to the photodetector. A resistor refers to an electronic component that regulates the flow of electrical current in an electric circuit, characterized by a resistance value measured in ohms (Q). Furthermore, in some embodiments, the at least one resistor may be connected on a lower side of the photodetector power supply or on a higher side of the photodetector power supply. As used herein, the lower side of the power supply of a photodetector refers to the ground or the more negative side of the power supply. Connecting a resistor on the lower side of a photodetector power supply amounts to placing the resistor between the photodetector and the ground. In other words, the resistor is connected in series with the photodetector and the ground or the negative terminal of the power supply. Conversely, the higher side of the power supply of a photodetector refers to the positive or higher voltage side of the power supply. Connecting aresistor on the higher side means amounts to placing the resistor between the positive terminal of the power supply and the photodetector. This configuration places the resistor in series with the photodetector and the positive terminal of the power supply. Fig. 4D illustrates an exemplary electro-optical reception matrix 220, similar to the one shown in Fig. 4A. In this configuration, each input 224-1 to 224-4 of the electro-optical matrix 220 is connected to a balanced photodetector 404-1 to 404-4. A resistor 406-1 to 406-4, with resistance value "R" is placed on the lower side of each photodetector's power supply, specifically between the photodetector 404-1 to 404-4 and the ground. While the resistance values "R" of all the resistors in this example are identical, it should be noted that resistors with different resistance values may also be used. In some alternative embodiments, each input 224-1 to 224-4 of the electro-optical matrix may include a first resistor connected to the higher side of the photodetector power supply and a second resistor connected to the lower side of the photodetector power supply.

[0161] Consistent with the disclosed embodiments, electro-optical matrix 220 may be further configured to generate a plurality of electronic control signals, one for each of the plurality of interference signals. For instance, referring to Fig. 4D, an electronic control signal can be generated by measuring the voltage, intensity, and / or power across the terminals of each resistor connected on the lower side of the power supplies of balanced photodetectors 404-1 to 404-4. This configuration allows for precise monitoring and control of the performance of the photodetectors by tapping into the electrical characteristics at these points. The electronic control signals may be generated in addition to the electronic signal outputs.

[0162] In contrast to the plurality of electronic signal outputs produced by each coupled directional coupler / balanced photodiode pair (402-i / 404-i, with 'i' representing a particular input) with a frequency equal to the beat frequency between the associated LOi and Rxi optical signals (and which are subsequently summed to provide the summed signal), the electronic control signal outputs (labeled Pi in Fig. 4D) each include different contributions or portions according to the interference signal provided by the associated optical coupler 402 -i. In a situation wherein an optical coupler 402-i is providing an interference signal corresponding to a mixture of the associated LOi and Rxi optical signals, the corresponding electronic control signal Pi includes a first contribution (PLOI) related to the LOi signal, a second contribution (PRX0 related to the Rxi signal (i.e. reflection signals from the FOV), and a third contribution (Pieakage) related to the intrinsic noise of the photodiode. It is to be appreciated that these contributions are canceled in the electronic signal outputs provided thatthe optical coupler corresponds to a 50:50 coupler and the photodiodes possess similar characteristics. In a situation wherein the optical coupler 402-i is only receiving the LOi signal as an input and thus providing an interference signal corresponding to a fraction of the LOi signal to the photodiodes, the corresponding electronic control signal Pi only includes the contribution (PLOI) related to the LOi signal and the contribution (Pieakage) related to the intrinsic noise of the photodiode. In a situation wherein the optical coupler 402-i is only receiving the Rxi signal as an input and thus providing an interference signal corresponding to a fraction of the Rxi signal to the photodiodes, the corresponding electronic control signal Pi only includes the contribution (PRX0 related to the Rxi signal and the contribution (Pieakage) related to the intrinsic noise of the photodiode. In a situation wherein the optical coupler 402- i is not receiving any signal as an input and thus not providing any interference signal, the corresponding electronic control signal Pi only includes the contribution (Pieakage) related to the intrinsic noise of the photodiode. Since the LOi signal is provided by the laser source, it should be noted that in the vast majority of cases, the contribution related to the LOi signal (PLO0, when present, dominates the electronic control signal Pi. It is also to be appreciated that Pi only reflect the photocurrent generated by a single photodiode.

[0163] In some embodiments, electro-optical reception matrix 220 may be further configured to provide the plurality of electronic control signal outputs to a monitoring unit. The monitoring unit may be connected to the optical distribution matrix. As mentioned earlier, in scenarios where optical distribution matrix 210 utilizes active components for selective signal distribution, feedback or control signals, typically in the form of electric control signals, may be provided by a monitoring unit to operate distribution matrix 210. Fig. 4E illustrates an electro-optical module 200 similar to the one shown in Fig. 2B further featuring a monitoring unit 230 connected to optical distribution matrix 210 and electro- optical reception matrix 220, and thus configured to receive the plurality of electronic control signal Pi provided by electro-optical reception matrix 220. Monitoring unit 230 may include various electronic components configured to collect and analyze the plurality of electronic control signal Pi (e.g., analog-to-digital converters, amplifiers, processors etc.) Monitoring unit 230 may be internal to electro-optical reception matrix 200 (as shown in Fig. 4E) or external to electro-optical reception matrix 200 (e.g., included in processing unit 120).

[0164] In some embodiments, monitoring unit 230 may be configured, based on the plurality of electronic control signal outputs, to determine leakage signals associated with the at least one photodetector of each of the electro-optical reception matrix inputs. In scenarios where the outputs 202-1 to 202-4 of optical distribution matrix 210 are non-active and / or noLO signal is provided to electro-optical reception matrix 220, no interference signal is generated. Consequently, each electronic control signal Pi includes only the contribution (Pieakage) related to the intrinsic noise of the photodiode. This configuration notably enables calibration of the photodetectors and more accurate readings of the output power, as the absence of interference signals allows for the precise measurement of the photodiode's intrinsic noise levels. By isolating the noise contribution, monitoring unit 230 may assess the true performance and integrity of the system, leading to improved diagnostics and optimization of the electro-optical components. Determination of the photodiodes leakage signals may be more efficient when module 200 or LIDAR system 100 is not exposed to any external light sources, as some of these sources may inadvertently reach and affect a specific reception channel Rx, thereby contributing to the electronic control signal as PRX. This ensures that the measurement of leakage signals remains accurate and reliable, without external influences skewing the data.

[0165] In some embodiments, monitoring unit 230 may be configured to determine ambient light levels based on the plurality of electronic control signal outputs. This assessment occurs during periods when the laser source is inactive or in channels that are currently not in use for readout purposes. Ambient light can originate from various sources, such as sunlight or other sources emitting wavelengths detectable by the photodetectors, which is particularly pertinent in LIDAR applications. By evaluating the electronic control signal Pi of a reception channel Rxi when the corresponding transmission channel Txi is inactive (i.e., no LOi signal provided and optical signal Txi transmitted), the contribution PRXI observed in the Rx signal collected corresponds solely to ambient light. This allows for precise measurement of ambient light levels. Within the context of LIDAR systems, the ambient light levels per reception channel Rximay be associated with a position in the measured LIDAR FOV, and further associated with a corresponding distance measurement of an object in the same position of the LIDAR FOV, since the distance and electronic control signals are obtained using the same photodetectors in the reception channel.

[0166] In some embodiments, multiple ambient light levels may be measured and grouped to form a two-dimensional image. For example, each ambient light measurement may be associated with a portion of the FOV of a LIDAR system, and associated with the distance measurements obtained using the reception matrix. The ambient light ‘pixels’ may be grouped to form a two-dimensional image. This image may not suffer from artifacts LIDAR systems are sensitive to, and may enable each photodetection Rx channel to output an IR measurement in similar to a pixel in a camera system. The image may have the advantageof being fully correlated with the distance measurement pixels, and may be used downstream for object detection and redundancy in scene perception.This approach enables monitoring unit 230 to accurately assess ambient light conditions by analyzing electronic signals from inactive channels or during laser downtime. Calibrating leakage can further enhance the determination of ambient light levels by effectively separating the Pieakage contribution (related to intrinsic noise, which is consistently present) from the PRXcontribution in the Pi electronic control signal. This decoupling process enhances the accuracy of ambient light level measurements, improving overall system performance and functionality.

[0167] Within the context of a LIDAR system, determining the ambient light level may enable the generation of a ‘noise’ image. This noise image comprises ambient light (e.g. infrared light) signal levels per pixel measured in the FOV. The noise image is a 2D image, and may be acquired at the desired resolution and frequency. This noise image, which may be acquired at a frequency lower than the frame rate (i.e., the rate at which Rx signals are detected and measured for generating the electrical output signals), provides a detailed map of the noise environment. By generating a noise image, a LIDAR system may provide an additional measurement to the point cloud, with essentially the same hardware. The photodetectors may be used to measure both coherent detection signals, and ambient light signals (which are not modulated, but passively sampled). The noise image may be used to increase redundancy in measurements, and may be used to determine if measurements suffer from blooming or other artifacts LIDAR systems are typically prone to, and improve scene perception including identification of objects, classification of objects, and determining the size of objects.

[0168] In line with the disclosed embodiments, monitoring unit 230 may also include various components configured to provide feedback or control signals to the optical distribution matrix 210. The feedback signal may be based on the plurality of electronic control signals provided by the electro-optical reception matrix 220. For example, in some embodiments, monitoring unit 230 may be configured, based on the plurality of electronic control signal outputs, to provide a feedback signal to optical distribution matrix 210 to tune the selective distribution of the optical output signal generated by the light source to the plurality of transmitting optical waveguides. For a given reception channel in the absence of Rxi signal, i.e., when only the LOi signal is provided, only the contribution (PLO related to the LOi signal and the contribution (Pieakage) are included in the Pi electrical control signal. Given that the contribution PLOI dominates, and / or as discussed above the contribution Pieakagemay be known from calibration, evaluating Pi under these conditions allows for the determination of the optical power of the LO signal provided. Because the LO optical power is directly correlated to the optical power of the corresponding Tx signal (as the local oscillator light paths are directly linked to the output of the optical distribution matrix, and the LO-to-Tx ratio is calibrated), it becomes feasible to determine the transmitted optical power of the Tx signal. By obtaining the electronic signal output of a given reception channel Rx, the optical power of the corresponding Tx signal transmitted by the optical distribution matrix 210 can be determined. A feedback control signal can then be generated to tune the selective distribution if the determined optical power does not match the desired optical power. Such discrepancies may arise due to thermal fluctuations, aging, or other environmental factors that cause the active components of the optical distribution matrix to become miscalibrated. These fluctuations can result in non-active channels inadvertently emitting signals and active channels emitting weaker signals than expected. By continuously monitoring the electronic control signals and comparing the determined optical power with the desired optical power, monitoring unit 230 can identify and correct these discrepancies in real-time. This dynamic adjustment process ensures that the optical distribution matrix 210 maintains optimal performance and accuracy in the transmission of optical signals. The described approach enables the system to detect and compensate for variations in optical signal distribution, thereby enhancing the reliability and stability of the overall system.

[0169] Regular calibration and feedback adjustments may help prevent performance degradation, ensuring that each transmission channel Tx operates within specified parameters. The calibration process may involve several steps:• Sequential Activation: Output channels of the optical distribution matrix 210 (e.g., 202-1 to 202-4) may be sequentially activated.• Sampling: Monitoring unit 230 may sample each electronic control signal (e.g., Pi to P4) provided by the electro-optical reception matrix 220. This sampling may occur at a frequency lower than the frame rate, i.e., the rate at which optical signals are transmitted and collected, and the plurality of electronic signal outputs are generated.• Identification: During this step, monitoring unit 230 may identify transmission channels that have a non-zero signal when a zero signal is expected. Zero signal may be expected when the laser is off, or when the optical distribution matrix 210 is off for a particular channel.• Feedback and Tuning: Monitoring unit 230 may then provide a feedback signal to tune the active components of the optical distribution matrix (e.g., phase shifters) for the identified transmission channels, minimizing discrepancies.

[0170] Monitoring unit 230 repeats this process continuously to ensure optimal performance and accuracy in the transmission of optical signals. This systematic approach may enable real-time adjustments and maintenance, ensuring that the system remains properly calibrated and performs within the specified parameters.

[0171] In some embodiments, the determination of the power transmitted on each transmission channel may serve other purposes. For example, in addition to calibrating the optical distribution matrix, this process may ensure compliance with eye safety regulations. By accurately evaluating the transmitted optical power for each channel, monitoring unit 230 may verify that the emitted signals remain within safe intensity levels, thus preventing potential harm to human eyes or other sensitive components. This may be particularly beneficial in applications such as LIDAR, telecommunications, and medical devices, where precise control over optical power is valuable for both performance and safety. Monitoring unit 230 may continuously evaluate the electronic control signals and compare the measured optical power against predetermined safety thresholds. If any channel exceeds the safe limits, monitoring unit 230 may automatically adjust the power output, either by reducing the signal strength or shutting down the channel temporarily. This proactive approach helps maintain a safe operational environment and ensures regulatory compliance.

[0172] In another scenario, determining the power transmitted may enable control of the generated electrical output signals. By ensuring that the transmitted LO signal and Rx signals are not excessively strong, the monitoring unit 230 can prevent the photodetector from becoming saturated. Consequently, the control signals employed in the optical distribution matrix can be fine-tuned to calibrate and adjust the values of the electrical signals generated within the electro-optical matrix. This fine-tuning process enhances the overall measurement accuracy and reliability.

[0173] In some embodiments, monitoring unit 230 may configured to, based on the plurality of electronic control signal outputs, mitigate blooming effects. In the context of a LIDAR system, blooming occurs when the laser beam is reflected or scattered back to the sensor by a particularly bright or reflective object, such as a retroreflector (e.g. cat-eye road markers, road signs, etc). This reflection can overwhelm the LIDAR sensor, leading to detections by neighboring Rx channels, leading to distorted or erroneous data. The term "blooming" refers to the appearance of the dilated point cloud data, where the size of objectsappears incorrectly increased due to detections of strong reflections by neighboring receiving channels. In theory, if the optical distribution matrix 210 is calibrated, and only one Rx channel is active at any given time, blooming should be mitigated. Blooming may occur in the event that the optical distribution matrix 210 is not calibrated, and the LO signal is nonzero when a zero signal is desired. In such cases, strong reflections may result in false signal detections.

[0174] By analyzing the electronic control signals, monitoring unit 230 may identify instances of blooming and adjust the system parameters accordingly. This may involve modifying the power output of the laser, altering the sensitivity of the photodetectors, ignoring certain measured signals, or dynamically adjusting the signal processing algorithms to filter out the effects of blooming. This may ensure that the data collected remains accurate and reliable, preventing the LIDAR system from being overwhelmed by highly reflective objects and maintaining the integrity of the point cloud data. Transmission / Reflection overlapping coupler

[0175] In the aforementioned section, it was noted that a LIDAR system typically consists of at least one transmitting channel and at least one corresponding receiving channel. One primary function of the transmitting channel is to emit an optical signal directed toward a specific location within the LIDAR FOV, potentially interacting with a target. Conversely, the receiving channel is tasked with capturing the resultant reflected optical signal. One key question that arises is how to optimize the collection and routing of the reflected optical signal toward the designated receiving channel. Addressing this challenge can be important for the effective functioning of the LIDAR system. The subsequent sections describe a system, which can be implemented on a photonic chip and which is aimed at enhancing the overall performance and accuracy of the LIDAR system by improving collection and routing of reflected optical signals. It is to be appreciated that the systems presented in the following sections may be relevant to various types of LIDAR technologies, including but not limited to CW-LIDAR and ToF-LIDAR.

[0176] Figs. 5A-B depict various existing solutions in the current state of the art designed to address aforementioned challenges. Some LIDAR systems, exemplified by the configuration shown in Fig. 5 A, include a circulator 510 to handle the routing function. In this approach, both the transmitting channel and its corresponding receiving channel are connected to a circulator, a device that facilitates the unidirectional flow of an optical signal. In this setup, when the transmitting channel delivers an optical signal, the circulator routes itthrough an external coupler configured to emit the optical signal toward a specific location in the LIDAR FOV. The same external coupler is then used to collect the reflected optical signal, which, based on the operation of the circulator, is directed toward the associated receiving channel. Although this configuration offers advantages such as a high overall efficiency (e.g., at or near 100%, meaning the entire optical signal from the transmitting channel is delivered, and the entirety of the collected reflected optical signal is routed to the receiving waveguide), there remain challenges with such a structure. Circulators are not suitable for implementation on a photonic chip (e.g., using silicon photonics). Consequently, a circulator configuration requires the use of optical fibers and / or other non-integrated components, leading to an increased overall footprint for the LIDAR system and higher costs.

[0177] An alternative approach applicable to a PIC involves the use of passive optical splitters. For example, as illustrated in Fig. 5B, a 50:50 (e.g. 3dB) passive optical splitter 520 may be connected to a transmitting channel and a receiving channel. By utilizing just one of the two outputs from the optical splitter (e.g., Txi / Rxi) along with a corresponding external coupler, an optical signal can be directed towards a specific location, and the corresponding reflected optical signal can be collected and then routed to the receiving channel. However, due to the inherent splitting principle, only 50% of the signal delivered by the transmitting channel is emitted, and only 50% of the collected signal is routed to the receiving channel, resulting in an overall efficiency of no more than 25%. Moreover, since passive optical splitters are typically polarization-specific, only a single polarization can be directed toward the receiving channel, causing an additional 50% loss and an overall efficiency of no more than 12.5%.

[0178] When employing the two different outputs (Txi / Rxi and TX2 / RX2) associated with external couplers pointing to two distinct locations in the LIDAR FOV, transmission efficiency can be improved. Depending on the actual geometry of the optical splitter, these two locations may be relatively close, allowing the two delivered optical signals to merge and resemble a single larger transmitting signal, which can result in a transmission efficiency at or near 100%. However, this configuration can also result in compromised system resolution. Furthermore, the two collected reflected signals may interfere within the optical splitter, leading to additional challenges such as loss due to speckle effects. In essence, while approaches utilizing a passive optical splitter are implementable on a PIC chip, they may result in lower system efficiency.

[0179] Achieving a high level of emitting / collecting / routing efficiency, at or near 100%, is preferable for the optimal functionality of a LIDAR system. While certainconfigurations utilizing circulators or passive optical splitters show promise, their limitations, such as the inability to integrate circulators on a photonic chip and the inherent signalsplitting drawbacks, underscore the need for alternative strategies in the quest for enhanced system efficiency. For a fully integrated LIDAR system, alternative strategies may be beneficial. One alternative strategy may include fully distinct transmitting and receiving channels pointing to substantially the same location in the LIDAR system FOV. This approach not only aims for an emitting / collecting / routing efficiency approaching 100% but also can offer improved spatial resolution of the LIDAR system.

[0180] In some embodiments, a photonic integrated circuit (PIC) may include at least one transmitting waveguide. The at least one transmitting waveguide may be configured to deliver, at an output port, an optical beam to a predetermined location in space. Further details regarding waveguides are provided in the definition section of the present disclosure. In some embodiments, the cross-sectional profile dimensions of the at least one transmitting optical waveguide may align with the order of magnitude of the wavelength of the optical signal it is designed to convey within the waveguide material, as outlined in the definitions section herein.

[0181] When employed in conjunction with an (external) output port or coupler, the optical signal confined in the waveguide may exit the waveguide structure (and the PIC) and propagate in free space towards a specific location in the LIDAR FOV. Depending on the properties of the port, the optical signal may assume the form of a beam, such as a Gaussian beam, characterized by various parameters, including beam waist, divergence, and polarization, each influencing the behavior of the beam along its trajectory. Within a LIDAR system, the designated transmitting waveguide may assume the role of a transmitting channel. This waveguide serves as the conduit through which the optical signal (Tx signal) is guided, with its characteristics and parameters influencing the transmission of the signal to a predetermined location within the LIDAR FOV.

[0182] In some embodiments, the PIC may include at least one receiving waveguide. The at least one receiving waveguide may be configured to receive, at an input port via, a reflected optical beam from the predetermined location in space. The at least one receiving waveguide may be paired with the at least one transmitting waveguide, establishing an intrinsic association between the two. Similar to the transmitting optical waveguide, the receiving counterpart may possess specific characteristics, including material properties, cross-sectional profile, and supported electromagnetic modes. Additionally, in certain embodiments, the dimensions of the cross-sectional profile of the receiving waveguide maybe closely aligned with the wavelength of the optical signal it is intended to receive and carry within the waveguide material.

[0183] When utilized in conjunction with an (external) input port or coupler, the receiving waveguide may collect an optical beam, such as a Gaussian beam, reflected from a specific location in free space (outside the PIC). Subsequently, this collected optical signal is confined within the waveguide structure. Within the context of a LIDAR system, the designated receiving waveguide may assume the role of a receiving channel. This waveguide functions as the conduit guiding the reflected optical signal (Rx signal) from the predetermined location within the LIDAR FOV.

[0184] In some embodiments, the at least one transmitting optical waveguide and the at least one receiving optical waveguide may share a substantially similar mode-field diameter (MFD). As used herein, the term "mode-field diameter" refers to the spatial extent of an optical mode within a waveguide. It characterizes the cross-sectional size of the optical field distribution in the waveguide, which, in turn, relates to the effective size of the guided mode. Matching MFDs between different waveguides may be valuable in certain optical systems for optimizing the coupling efficiency. References to the transmitting waveguide and receiving waveguide sharing a "substantially similar" mode-field diameter (MFD) indicate that their respective MFDs are comparable in value, with a small permissible difference. In this context, "substantially" suggests a degree of similarity that accommodates a certain tolerance or margin of error. For example, a tolerance of 10% signifies that the MFD of the transmitting waveguide and the MFD of the receiving waveguide may differ by up to 10% from each other. This tolerance accounts for slight variations that might occur due to manufacturing processes (e.g., nanofabrication imperfections), other factors, or design reasons. Such deviations between the two MFDs may exist without rendering the overall performance of the optical system unsuitable for an intended purpose.

[0185] In some other embodiments, the at least one transmitting waveguide and the at least one receiving waveguide may share one or more common properties without necessarily resulting in substantially identical electromagnetic modes. As an illustration, both waveguides could be constructed from identical materials, yet have different cross-sectional profiles, resulting in distinct electromagnetic modes, and they may also differ in terms of their overall physical lengths.

[0186] Furthermore, in some embodiments, the at least one transmitting optical waveguide and / or the at least one receiving optical waveguide may function as single mode waveguides, as outlined in the definitions section herein.

[0187] In some embodiments, the optical beam delivered by the at least one transmitting waveguide and the reflected optical beam received by the at least one receiving waveguide pass through a scanning module. A scanning module refers to any system or component configured to introduce controlled adjustments to the directionality or orientation of optical beams. This versatile module may incorporate various mechanisms, including motorized elements, such as mirrors, lenses, or other optical components, enabling precise scanning or sweeping of the beams across a designated region. The primary objective of the scanning module is to augment the spatial coverage of a PIC and facilitate the collection of comprehensive and accurate 2D and / or 3D spatial data by directing and capturing optical signals from different angles or directions. Operating from a static position of the output and input ports of the PIC, the scanning module enables emission toward multiple points and the collection of optical beams from various positions, enhancing the system's capability to perceive and analyze its surrounding environment. A scanning module is capable of sweeping across a designated region following a specific scanning pattern. Scanning patterns may be categorized as either continuous or discrete, exhaustive or non-exhaustive, redundant (involving overlap between different scanning points), or non-redundant.

[0188] Within the context of LIDAR systems, scanning modules may play a prominent role, as a scanning module can dictate the spatial coverage of a LIDAR system. Scanning modules can define a LIDAR system FOV and influence various associated parameters.

[0189] Fig. 6A illustrates an exemplary PIC 600 and scanning module 650 in accordance with the disclosed embodiments. As shown PIC 600 features a transmitting waveguide 602 and a receiving waveguide 604 coupled respectively to an output port 612 and an input port 614 represented by black diamonds. Transmitting waveguide 602 is configured to deliver at output port 612 an optical beam (Tx signal, black dashed line) while receiving waveguide 604 is configured to capture at input port 614 a reflected optical beam (Rx signal, black dotted line). Both Tx and Rx signals traverse scanning module 650, which is configured to alter in a controlled manner the direction of the optical beam (Tx signal). This alteration enables the scanning of a predetermined portion of space, facilitating the collection of reflected optical signals across swept positions. Scanning module 650 comprises multiple components, including an optical lens 652 (Tx / Rx lens), two motorized mirrors 654 and 656, and an optical window 658. Mirrors 654 and 656 through changes in their positions, manipulate the beam's direction, allowing scanning along both a substantially horizontal axis in the plane of PIC 600 and a vertical axis orthogonal to the PIC 600 plane, thereby enablinga 3D scan of a designated region. In some embodiments, one of these axes may be referred to as a fast axis, i.e., scanning is performed rapidly and potentially continuously along this axis while the other axis is referred to as a slow axis, i.e., scanning along this direction is incremental and changes relative to this axis are performed incrementally (e.g., after completing a scan along the fast axis to provide raster scanning, continuous raster scanning, etc.). Not all scanning patterns are generated using a fast and slow axis approach. Other approaches may be used to sweep a designated region. Examples include spiral scanning, diagonal scanning, elliptical or circular scanning, periodic scanning, 360°-scanning, or any other suitable pattern offering a desired level of coverage of a designated zone. In such cases, more specific motorizations and mirror systems may be implemented within the scanning module 650.

[0190] Consistent with the disclosed embodiments, PIC 600 and scanning module 650 may be integrated within a LIDAR system such as CW LIDAR 100 illustrated in Fig. 1. In this context, the designated scanning region of scanning module 650 aligns with a LIDAR FOV, whose dimensions are delimited by the characteristics of mirrors 654 and 656. Transmitting waveguide 602 and receiving waveguide 604 may not only be coupled to output port 602 and input port 604 at one of their ends but may also be connected to different components of a LIDAR system. For instance, considering the scanning / multiplexing module 200 shown in Fig. 2 A, which can be integrated into LIDAR system 100, transmitting waveguide 602 may be linked to the optical distribution matrix 210, while the receiving waveguide is connected to the electro-optical reception matrix 220. It is to be appreciated that the system illustrated in Fig. 6A is for illustrative purposes only, and PIC 600 and scanning module 650 may include various different configurations based on specific application requirements.

[0191] In some embodiments, a physical location on the PIC chip of the output port of the at least one transmitting waveguide and a physical location on the PIC chip for the input port of the at least one receiving waveguide may be arranged relative to each other with respect to one or more scanning properties of the scanning module such that the optical beam and the reflected optical beam overlap over a predetermined spatial range. In other words, the specific arrangement of the output and input ports may take into account the scanning properties of the scanning module, to spatially align the emitted and reflected optical beams during the scanning process. This alignment may improve system efficiency, as it may result in the transmitted and received beams effectively coinciding over a designated spatial region, contributing to accurate and reliable data collection. As noted above, such an efficiency maybe valuable to the overall performance of the LIDAR system. In contrast, in the approaches illustrated in Figs. 5A-B, the output and input ports of the systems (external ports) are separated. Achieving a desired level of system performance using the configurations of Figs. 5A-B may require arranging the ports to target or “shoot” beams to substantially the same location in space, in order to provide overlap between the optical and reflected optical beams. In such arrangements, the two ports may need to be sufficiently close to each other on the PIC to obtain a reasonable amount of overlap over a predetermined spatial range, which, within the context of LIDAR systems, may account for the LIDAR system operational range.

[0192] In the following sections, unless explicitly mentioned otherwise, the term "overlap" refers to the alignment between the optical beam (Tx signal) and the reflected optical beam (Rx signal), also known as Tx / Rx overlap. However, it is to be appreciated that while this definition of overlap primarily pertains to the spatial coordination between the transmitted and reflected optical beams, other aspects of the system may involve the concept of overlap. For instance, concerning the scanning module, a scanning pattern may incorporate overlap between various swept portions of space to achieve comprehensive scanning. This form of overlap is linked to the scanning pattern rather than to the physical arrangement of the output and input ports.

[0193] Fig. 6B illustrates an example of Tx / Rx overlap, with respect to features identified in Fig. 6A. Referring to the example configuration of Fig. 6B, transmitting waveguide 602 and receiving waveguide 604 with their associated output 612 and input 614 ports are shown together with the Tx / Rx lens 652 of scanning module 650. For the sake of clarity, the other components of scanning module 650, namely mirrors 654 and 656 and optical window 658, are not represented. In this illustration Tx and Rx signals are represented as optical beams (shaded area for Tx signal, dotted pattern area for Rx signal) rather than optical rays. It is to be appreciated, that while referring to a reflected optical beam, the Rx beam does not necessarily strictly correspond to the actual reflected optical beam from a target at a predetermined location. Instead, it pertains to a potential field of optical paths defined by the construction of the input port on the PIC chip that can be efficiently collected and conveyed by the receiving waveguide. This field is capable of accommodating the reflected optical signal. If this potential field of optical paths aligns precisely with the actual reflected signal, the collection efficiency may be up to 100%.

[0194] Consistent with the disclosed embodiments, these two beams exhibit overlap over a predetermined spatial range, e.g., over a certain distance from lens 652, in a direction in the plane of PIC 600. In some embodiments, the overlap, or the degree of the overlapbetween the optical beam and the reflected optical beam may evolve along the predetermined spatial range. Due to the separation of output 612 and input 614 ports, Tx signal and Rx signal may not be parallel to each other. Consequently, the overlap may gradually decrease along the predetermined spatial range. For instance, the overlap could start at 100%, indicating perfect overlap (and therefore 100% efficiency), and then decrease gradually until reaching 0% at the predetermined spatial range. This evolution is also evidenced in the insets illustrating the cross-section of the Tx and Rx optical beams at three intermediary distances below the predetermined spatial range. In the example provided, the overlap diminishes from 80% at distance di to 50% at d2 and further to 20% at ds.

[0195] Fig. 6B illustrates the Tx optical beam and Rx reflected optical beam as consistent across the predetermined spatial range, exhibiting identical cross-sections. In practice, optical beams, such as Gaussian beams may experience divergence (after the Rayleigh range) when propagating along a direction in space. However, such divergence, depending on the design and arrangement of the output / input ports 612 / 614 and lens 652 may be minimized. Nevertheless, the divergence of the beams may have a slight impact on the overlap evolution. For example, as the beam gradually expands, the overlap diminution may be slightly slowed compared to a situation with consistent optical beams. Given the different scales involved, such as the Rayleigh range versus the predetermined spatial range and beam divergence versus angular separation of the two non-parallel beams, this effect may be negligible. It may not significantly contribute to the overall evolution of the overlap.

[0196] Fig. 6B illustrates Tx optical beam and Rx reflected optical beams with identical cross-sections. However, such a stringent condition is not obligatory, and in some embodiments, the two beams may exhibit different cross-sectional areas without compromising the establishment of overlap. In fact, in certain scenarios, purposely increasing the size of the Rx reflect optical beam or rather the size of the beam that may be accommodated by the input port, may prove to be an useful strategy, e.g., to promote a higher and more consistent degree of overlap, which may potentially compensate for certain scanning properties. Further, accepting a potential penalty stemming from ambient noise may allow increased collection of the Rx signal (e.g., fully collected). However, this type of collection may degrade the signal and could be detrimental to certain technologies that rely on coherent detection such as CW-LIDAR technologies.

[0197] In some embodiments, the one or more scanning properties may include at least one of a scanning velocity, a scanning direction, a scanning period, or a combination thereof. As used herein, the term "scanning properties" encompasses any factors influencingthe scanning behavior of the scanning module. The scanning velocity, along a specific direction, denotes the speed at which the scanning module introduces adjustments to the directionality or orientation of optical beams. In the context of a LIDAR system, this velocity affects the rate at which the system collects data points across its FOV. Scanning velocity may be expressed in terms of angular velocity, representing the angle swept across a designated area for a certain period, or distance velocity, indicating the distance swept across a designated area for a certain period. The scanning direction, (e.g., relative to fast and slow axes), relates to the orientation in which the scanning module modifies the direction of the optical beams. This aspect determines the spatial coverage and potentially influences the order in which different portions of the designated region are scanned. The scanning period, also known as pixel time, corresponds to the time taken by the scanning module to scan a region defined by the module's resolution for a single pixel measurement. The overall scanning duration is the time required for the scanning module to complete a full scan or cycle, dependent on the scanning period. Both the scanning period and the overall scanning duration can influence the temporal aspects of data acquisition and contribute to determining the frequency at which the system, e.g., LIDAR system, captures spatial information. Although other factors, such as scanning resolution or scanning FOV, may also play a role in the scanning properties and be taken into account in the design of the PIC, these properties are linked by various mathematical relationships, and these other properties can be directly deduced from others.

[0198] In some embodiments, a physical distance on the PIC chip between the at least one transmitting waveguide and the at least one receiving waveguide may be in plane of the PIC chip or out of plane of the PIC chip. This physical distance refers to the spatial arrangement of the at least one transmitting waveguide and the at least one receiving waveguide on the surface of the PIC chip. When the distance is in-plane, the transmitting and receiving waveguides are situated on the same plane of the chip. On the other hand, if the distance is out-of-plane, the transmitting and receiving waveguides are positioned on different planes, possibly at different vertical levels or heights within a PIC having a three- dimensional structure. This flexibility in the spatial arrangement allows for various different configurations depending on the design requirements and constraints of the system. In certain embodiments, the spatial arrangement of the at least one transmitting waveguide and the at least one receiving waveguide may be chosen based on the scanning direction. If the fast scanning axis aligns with an axis in the plane of the PIC, the two waveguides may be positioned in the same plane. Conversely, if the fast scanning axis is orthogonal to the planeof the PIC, the two waveguides may be designed to be stacked on top of each other. Each configuration presents its own set of advantages and challenges in terms of nanofabrication. For example, a vertical configuration with waveguides stacked on top of each other could offer a reduced footprint for the overall PIC. However, it comes with the constraint that the physical distance between the two waveguides is less flexible and is determined by the initial layer stack structure.

[0199] In some embodiments, the scanning velocity multiplied by the scanning period and the physical distance between the at least one transmitting waveguide and the at least one receiving waveguide on the PIC chip may compensate each other for a predefined distance. In other words, an angle or distance swept during the scanning period effectively counteracts the angular or spatial separation caused by the non-parallelism of the optical and reflected optical beams due to the physical distance between the at least one transmitting waveguide and the at least one receiving waveguide on the PIC chip (sometimes referred to as pitch). This compensation occurs at a specific scanning distance, optimizing the alignment of the beams and contributing to the overall efficiency of the system. This compensation mechanism is further described below in relation to Figs. 6C and 6D.

[0200] Figs. 6C illustrates different snapshots corresponding to the evolution of the position of the Tx optical beam and the Rx reflect optical beam when the scanning module is sweeping a designated region in a horizontal scanning direction x. At time to, the optical Tx beam reaches a target located at a distance ds (shown in Fig. 6B) for which the Tx / Rx overlap value is relatively moderate (20%). When the optical beam reaches the target situated at ds, assuming a certain degree of specular reflection and normal incidence, the reflected optical beam will travel back from ds to the PIC chip following a direction of propagation aligning with the position of the Tx beam at to. This return journey takes a certain time, referred to as Time of Flight (TF) and defined by ds / c, with c the speed of light. Accordingly, during the TF duration, the reflected optical beam maintains its direction of propagation. The key challenge lies therefore in aligning the position defined by Tx(t0) with the position of the Rx reflected optical beam at TF, in order to affect the collecting efficiency. As scanning continues during the TF duration, the position of the Rx beam (potential fields of optical path) evolves over time and gradually converges back to the position of the Tx beam at to, eventually surpassing this position. If TF corresponds to time ti, the Rx beam at ti has initiated its foldback towards the position of the Tx beam at to, resulting in a greater overlap than the initial overlap set by construction. If TF corresponds to a later time t2, the Rx beam at t2 perfectly aligns with the position (foldback completed) of the Tx beam at to, achieving a maximum overlap of 100%,and consequently, maximum efficiency. If TF extends to a further time, the Rx beam begins to overtake the position of the Tx beam at to, and the overlap begins to decrease again. Hence, the compensation for the pitch induced by the physical distance between the at least one transmitting waveguide and the at least one receiving waveguide may be achieved by the product of the scanning velocity and the scanning period for a predefined distance, for which TF satisfies the condition RX(TF) = Tx(to).

[0201] In Fig. 6D, the evolution of the Tx / Rx overlap is depicted, considering both the pitch and the fallback of the Rx beam. As illustrated, this evolution displays a local maximum for the predefined distance D, where the overlap reaches 100%. For a distance of zero, the overlap is also 100% but starts to decrease. In these short distances, the time of flight is so brief that the fallback operation of the Rx beam barely commences and cannot adequately compensate for the overlap drop caused by the pitch. Beyond a certain distance, the positive impact of the fallback operation begins to outweigh the overlap losses due to the pitch, leading to an increase in overlap until it reaches the 100% target for the predefined distance D. Once beyond the predefined distance D, the fallback operations cease and may even become detrimental. Consequently, the overlap decreases at a steeper rate, reflecting the destructive effect of the Rx beam's scanning position surpassing the initial Tx beam position, compounded by the pitch effect.

[0202] In some embodiments, the predefined distance may be tuned by selecting the scanning velocity and scanning period. As the pitch is fixed by the construction of the PIC, modifying the scanning module properties enables the selection of the predefined distance for which the overlap would be equal to 100% and the efficiency maximized. In some embodiments, the scanning properties of the scanning module may be modified and controlled by at least one processing unit. For example, if such a system is implemented within LIDAR system 100 shown in FIG. IB, processing unit 120 may be configured to control and modify the scanning properties of scanning module 650. It is to be appreciated that the existence of the predefined distance and the associated local maximal overlap arises from the initial imperfect overlap of the Tx and Rx beam positions. The Rx beam position is considered somewhat delayed compared to the Tx beam position in the scanning process. If the two beams were perfectly overlapping initially, the overlap would start at 100% and monotonically decrease at a rate determined by the scanning velocity. In an alternative scenario where the Rx beam position is ahead of the Tx beam position, the overlap would never reach 100%, starting below that value and decreasing at a steeper rate, influenced bythe scanning velocity and the pitch, similar to the latter part of the overlap evolution after the predefined distance shown in Fig. 6D.

[0203] Therefore, this configuration not only allows for the optimization of the Tx / Rx overlap but by compensating for pitch effects and utilizing the fallback operation of the Rx beam, the system may initiate the scanning of the next pixel without waiting for the reflected signal to return, leading to faster and more efficient data acquisition. Moreover, particularly in the context of a LIDAR system, such a system with the ability to adjust scanning module parameters provides flexibility in adapting the system to different scenarios, distances, and environmental conditions, enhancing overall versatility. Finally, another advantage, once again particularly relevant in the context of LIDAR systems, concerns the resolution of the long-range ambiguity proposed by this solution. In the context of LIDAR systems, long-range ambiguity refers to a situation where the system encounters challenges in distinguishing between signals that are received after traveling long distances. In LIDAR, which measures distances by analyzing the time taken for light to travel to a target and back (distance measurement may depend on the type of LIDAR technology involved but the overarching principle remains the same), distinguishing between signals may become more challenging when the travel time exceeds a certain limit. The complexity arises when the travel time surpasses a specific threshold, rendering it difficult for the LIDAR system to distinguish between the initial optical signal and the returning signals. In this situation, delayed signals, originating from a more distant target, might be misinterpreted as emanating from a closer target (e.g., as a result of later Tx illumination). This confusion arises because a new measurement cycle could commence before the time delayed signals reach the LIDAR detectors. Consequently, this phenomenon can introduce inaccuracies in distance measurements and has the potential to disrupt the precision of mapping or sensing processes. The proposed solutions described herein are aimed at addressing and resolving such long- range ambiguity, as the overlap factor is null for such long distances and that any signal received after a certain time limit can be interpreted either as an artifact or emanating from a closer target. The solution presented in this context effectively tackles and mitigates long- range ambiguity by ensuring that the overlap factor is negligible for long distances. In essence, this implies that any signal received beyond a certain time limit is treated as an artifact or is confirmed to originate from closer targets.

[0204] In some embodiments, the at least one receiving waveguide may include a plurality of receiving waveguides with a plurality of input ports. In such a situation each of the plurality of receiving waveguides would be associated or paired with the transmittingwaveguide. This approach may offer a larger versatility in the receiving channels. For example, in some embodiments, the plurality of input ports of the receiving waveguides may be arranged geometrically to receive the reflected optical beam at different times during a scanning period. In other words, the plurality of receiving waveguides may be each independently optimized in order to have a 100% overlap at different predefined distances, i.e., for reflected signals with different TF, received at different times. This configuration provides increased flexibility in controlling the overlap enabling a maximized or desired overlap factor for various predefined distances without altering the scanning properties. As an illustration, within the realm of LIDAR systems, a PIC chip might incorporate four distinct receiving waveguides associated with a transmitting waveguide, each optimized for pitch compensation by scanning at different predefined distances (e.g., 100m, 200m, 300m, 400m). Implementing such a setup allows for obtaining an average value of the Tx / Rx overlap (denoted as E[Tx / Rxi], with i denoting the distinct receiving channels) that remains relatively stable across the predetermined spatial range and high.

[0205] In some embodiments, the output port of at least one transmitting waveguide and the input port of the at least one receiving waveguide may include grating couplers or edge couplers. Grating couplers and edge couplers refer to optical components configured to facilitate the efficient coupling of light between integrated optical waveguides and free-space optical beams. A grating coupler is a device that uses a diffraction grating to couple light between a guided wave in an optical waveguide and a free-space optical beam. The grating structure diffracts the guided light into free space or collects incoming free-space light into the waveguide. Grating couplers can offer relatively high coupling efficiencies. On the other hand, an edge coupler is a structure where the optical waveguide terminates at the edge of the chip, and light is coupled to or from the waveguide at the chip's edge. Edge couplers are designed to transfer light between the waveguide and external optical components (e.g., optical fiber) or free space.

[0206] Fig. 7 illustrates exemplary geometries for an edge coupler and a grating coupler for the transmitting waveguide on a PIC chip 600. On the left side of Fig. 7, PIC chip 600 features an edge coupler 710 terminating at the edge of the chip. In this configuration, the emitted TX optical beam follows a direction parallel to the plane of the PIC chip 600. The edge coupler may include a tapered section designed to adiabatically convert the electromagnetic mode size from a confined, relatively small mode into a beam mode (e.g., Gaussian beam). The tapering may provide a smooth transition without significant perturbation to the electromagnetic mode. More details on tapered sections will be providedin subsequent sections. On the right side of Fig. 7, the PIC chip 600 includes a grating coupler 720. In contrast to the edge coupler, the emitted TX optical beam follows a direction out of the plane of the PIC chip 600, forming an angle with the normal to the plane. This angle may take any value ranging from 0 to 90° depending on the specific design of the grating coupler (scattering from individual grooves / rulings interfere at a certain angle).

[0207] In some embodiments, the output port of the at least one transmitting waveguide and the input port of the at least one receiving waveguide may be edge couplers and the at least one transmitting waveguide and the at least one receiving waveguide may include a straight section and a tapered section. A "straight section" in the context of waveguides refers to a segment of the waveguide that maintains a constant cross-sectional profile and does not exhibit significant variations in its geometry along its length. This portion allows for the propagation of an optical signal with minimal alteration to its spatial characteristics. On the other hand, a "tapered section" of the waveguide involves a gradual change in the cross-sectional dimensions along the length of the waveguide. As noted above tapering is designed to modify the mode size of the optical signal. In the context of an optical waveguide, the tapered section facilitates the transformation of the confined optical mode from a relatively small size in the straight section to a larger beam mode, such as a Gaussian beam. The tapering is often achieved in an adiabatic manner to ensure a smooth transition without inducing significant perturbations to the electromagnetic mode. In such a configuration the waveguides themselves may consist of a straight section for maintaining the guided mode and the output / input ports of a tapered section for mode transformation to facilitate efficient coupling and transmission / collection of optical signals.

[0208] Such an embodiment is illustrated in Fig. 8, which features a transmitting waveguide 602 (shaded waveguide) and a receiving waveguide 604 (dotted pattern waveguide) that both include a straight section (respectively 802 and 804) and a tapered section (respectively 812 and 814) that functions as the output 612 and input 614 ports. Specifically, the straight sections are responsible for maintaining the guided optical mode, while the tapered sections facilitate the transformation of the optical mode for efficient coupling. In some embodiments, a gap distance on the PIC chip between the at least one transmitting waveguide and the at least one receiving waveguide may vary in a vicinity of the tapered sections. For example, as illustrated in Fig. 8, the gap distance g between transmitting waveguide 602 and receiving waveguide 604 remains constant along the straight sections 802 and 804 and gradually decreases when progressing through the tapered sections 812 and 814 until ultimately reaching the gap value g’ at the edge of PIC 600. This tapering of the gap isdesigned to enhance the initial overlap between the transmitting Tx and receiving Rx beams. A smaller gap distance is advantageous in ensuring a more substantial initial overlap between the Tx and Rx beams. The proximity of the edges of the waveguides (or output / input ports) promotes a closer alignment, contributing to a higher initial Rx / Tx overlap, potentially approaching 100%.

[0209] In some embodiments, the tapered section of the at least one transmitting waveguide and the tapered section of the at least one receiving waveguide may have a different MFD. Alternatively, in some other embodiments, both tapered sections may possess substantially identical MFDs. The MFD refers to the spatial extent of an optical mode within a waveguide, characterizing the cross-sectional size of the optical field distribution. When the tapered sections have different MFDs, the spatial extent of the optical modes in the transmitting and receiving waveguides may differ during the transition from the straight sections to the tapered sections and may be different at the edges. This discrepancy in MFDs might be intentionally designed to achieve desired optical characteristics, desired performance goals, and / or to avoid coupling between the two waveguides. On the other hand, in cases where both tapered sections possess substantially identical MFDs, the spatial extent of the optical modes in the transmitting and receiving waveguides may undergo a similar expansion or compression during the tapering process. Such a configured may assist in maintaining consistency or symmetry in the optical characteristics of the waveguides, potentially simplifying the manufacturing process or achieving specific coupling efficiency goals. The choice between having different or identical MFDs in the tapered sections depends on the specific requirements and objectives of the optical system being designed. In the example shown in Fig. 8, transmitting waveguide 602 and receiving waveguide 604 share similar tapered sections 812 / 814, with similar geometry provided that these two waveguides 602 / 604 are made of a same material these two tapered sections 812 / 814 share an identical MFD.

[0210] In some embodiments, the straight sections and the tapered sections of the at least one transmitting waveguide and the at least one receiving waveguide may be aligned. Alignment in this context refers to the intentional coordination or positioning of the straight and tapered sections of these waveguides. Aligning the straight and tapered sections implies that the corresponding portions of the transmitting and receiving waveguides are configured in a coordinated manner. This intentional alignment may serve various purposes, such as optimizing or preventing coupling between the waveguides, enhancing the spatial overlap of transmitted and received optical beams, and / or ensuring consistent optical characteristics inboth sections. The alignment of straight and tapered sections may be selected to achieve specific performance goals, reduce losses, or simplify the manufacturing process. In the example illustrated in Fig. 8, straight sections 802 and 804, and tapered sections 812 and 814 are precisely aligned. In alternative embodiments, intentional misalignment may be introduced between the straight sections and tapered sections of the at least one transmitting waveguide and the at least one receiving waveguide. This deliberate misalignment could involve differences in the length or size of the tapered sections between the two waveguides. For instance, the tapered section of the first waveguide may be intentionally shorter than the corresponding section of the second waveguide. The intentional misalignment may serve specific purposes, such as mitigating or controlling the coupling between the waveguides.

[0211] In some embodiments, the tapered section (of either the transmitting waveguide, the receiving waveguide, or both) may include a tapered profile. A tapered profile refers to the actual shape or appearance of a gradual change in the cross-sectional dimension(s) of the waveguide. The dimensions, such as width or height, may vary smoothly along the length of the tapered section. Certain tapered profiles may promote an adiabatic transformation, such that the electromagnetic mode undergoes the transition gradually without significant disruptions or with substantial coupling with higher-order electromagnetic modes. In some embodiments, the tapered profile may be one of linear, non-linear, concave, or convex. A linear profile involves a uniform change in dimension(s) and may simplify the design considerations. Non-linear tapered profiles, on the other hand, introduce a more complex curvature (e.g., parabolic profile, exponential profile. . .) to the variation in dimensions, potentially allowing for enhanced control over specific mode transitions. Concave and convex tapered profiles are characterized by inward and outward curvatures, respectively. These profiles can influence the mode transformation in different ways. A convex profile may tend to guide the electromagnetic mode toward the center, while a concave profile may guide it outward. The choice of a particular tapered profile depends on the desired mode transformation characteristics and the specific requirements of the waveguide system. Fig. 9 illustrates three exemplary distinct tapered profiles, namely a linear profile 902-1, a concave profile 902-2, and a convex profile 902-3.

[0212] Additionally, in some embodiments, the tapered profile of the tapered section of the at least one transmitting waveguide may be different from the tapered profile of the tapered section of the at least one receiving waveguide. This intentional difference in profiles allows for tailored control of the mode transformation characteristics for each waveguide, addressing specific requirements and functionalities associated with transmission andreception. For instance, the transmitting waveguide may employ a particular tapered profile that facilitates efficient coupling and transmission / emission of the optical signal. Conversely, the receiving waveguide may have a different tapered profile designed to enhance light collection and reception. In alternative scenarios, the tapered profile of the tapered section in both the transmitting and receiving waveguides may be identical or different depending on the specific design considerations or functional requirements for the optical system. Having an identical tapered profile for both waveguides may simplify the manufacturing process, streamline nanofabrication techniques, and contribute to overall system symmetry.

[0213] In some embodiments, the at least one transmitting waveguide and the at least one receiving waveguide may be symmetrical with respect to a plane. This symmetry implies that the geometric features, such as shapes, dimensions, and positions, exhibit a mirror-image relationship across this plane. The symmetrical configuration is intentional and may serve multiple purposes. For instance, symmetry may simplify the manufacturing process by allowing for shared or mirrored fabrication techniques for both waveguides (especially in a configuration wherein waveguides are staked), contributing to cost-effectiveness and efficiency. Additionally, symmetry may enhance the predictability and control of optical properties within the system. The symmetry may extend to various sections of the waveguides, including straight sections, tapered sections, or other relevant components. This design choice is particularly advantageous in situations where identical or highly similar optical characteristics are desired for both the transmitting and receiving waveguides. In the example illustrated in Fig. 8, transmitting waveguide 602 and receiving waveguide 604 are in the same plane and are symmetric according to the plane of symmetry P orthogonal to the plane of PIC chip 600. In an alternative example, wherein the two identical waveguides would be located one on top of the other, the plane of symmetry would be a median plane parallel to the plane of PCI chip 600.

[0214] In some scenarios, as different aspects may be uniquely attributed (e.g., specific MFD, tapered length, tapered profile. . .) to either the transmitting or receiving waveguides, no symmetry relationship may exist, but the lack of symmetry may not adversely impact the functionality or the routing / collecting efficiency of the system. The choice of symmetry or asymmetry may depend on specific design considerations and requirements for the optical system.

[0215] In some embodiments, the tapered section of the at least one transmitting waveguide and the tapered section of the at least one receiving waveguide may be further arranged relative to each other such that a value of a coupling ratio between the at least onetransmitting waveguide and the at least one receiving waveguide is below a predetermined threshold. As the structure defined by the closely spaced double tapered sections may resemble that of a "half directional coupler, a coupling may exist between the tapered section of the transmitting waveguide and the tapered section of the receiving waveguide, characterized by a coupling coefficient. The positioning of the two tapered sections may be optimized to maintain a coupling ratio below a predetermined threshold. By controlling the coupling ratio, undesired crosstalk or interference between the transmitting and receiving channels (which may be detrimental to the overall efficiency) may be reduced or eliminated. Keeping the coupling ratio below a predetermined threshold ensures that the interaction between the two waveguides remains at an acceptable level, preventing excessive signal leakage or cross-interference that could compromise the system's performance. Such an arrangement may involve adjusting the gap distance, the length of the tapered sections, or other geometric parameters to achieve the desired coupling ratio.

[0216] In some embodiments, the predetermined threshold may correspond to a value wherein there is no coupling between the at least one transmitting waveguide and the at least one receiving waveguide. In other words, the coupling ratio may be controlled (e.g., minimized) to eliminate cross-talk between the two waveguides. Reduced coupling can ensure that the transmitted optical signal remains within its designated waveguide, and there is minimal to no interaction with the adjacent receiving waveguide. The objective of setting the predetermined threshold at a point of no coupling is to maximize the routing efficiency of the system. Achieving a no coupling state between the waveguides involves careful design considerations, including the geometry, separation distance, and other parameters of the tapered sections. For instance, introducing a sufficiently large gap distance between the two tapered sections of the waveguides may reduce the coupling ratio to zero, as the evanescent tails of the electromagnetic modes do not overlap. However, a balance may be struck, as an excessively large gap distance may be detrimental to the initial value of the Tx / Rx overlap, impacting the overall efficiency of the system.

[0217] Alternatively, in some other embodiments, the predetermined threshold may correspond to a value wherein there is coupling between the at least one transmitting waveguide and the at least one receiving waveguide, and at a coupling length from the input port, a coupling ratio is 0 or 100%. This configuration represents a paradigm where deliberate cross-talk between adjacent tapered sections is sought. Within the context of codirectional coupling in the coupled mode theory formalism, the coupling ratio exhibits periodic behavior with the coupling length. In this scenario, the coupling length is defined asthe distance where maximum power transfer occurs. This intentional coupling configuration introduces controlled cross-talk between the waveguides at predetermined distances, offering versatility in system design. The periodic nature of coupling allows for strategic points along the waveguide where the coupling is minimized (0%) or maximized (100%), facilitating specific functionalities such as controlled signal transfer between the waveguides. The overall coupling region, where the tapered sections cross-talk, should accordingly be equal to the coupling length or a multiple of the coupling length. This configuration may be achieved by maintaining a sufficiently small gap distance between the tapered sections of the transmitting and receiving waveguides.On-chip Pixel architectures.

[0218] Signal quality in a LIDAR system may depend on refinements of various parameters within the LIDAR pixel structure and architecture. Such parameters may include:1. Rx and Tx Efficiency: Elevating the efficiency of both the transmission and reflection paths is valuable. Higher efficiency can offer increased signal intensity, consequently improving the signal-to-noise ratio.2. Polarization Data: In the context of LIDAR, polarization data may allow for material differentiation, characterization of surface properties, reduction of specular reflections, improved object segmentation, and enhanced environmental sensing. The analysis of polarization data may also enhance object recognition and depth measurements across diverse applications.3. Speckle Diversity: Speckle diversity may be used in conjunction with optical imaging and remote sensing to counteract the adverse effects of speckle noise. Speckle noise arises when coherent signals, such as laser light or radar waves, interact with rough surfaces or inhomogeneous media, creating a granular interference pattern. These patterns may cause the apparition of dark spots on acquired images or at a light sensor, which can limit measurement accuracy.

[0219] As an illustration of the formation of speckles, each point on an illuminated surface may be considered as a secondary source emitting or scattering spherical waves. Speckles result from the quasi-random interference of these waves, characterized by variations in amplitudes, phases, and polarization, either partially or completely depolarized relative to the incident light. To address the challenges posed by speckle noise, speckle diversity can be employed in remote sensing applications like LIDAR. This concept involves capturing multiple independent measurements of the same scene by introducing diversity intothe imaging system. This diversity may be achieved through alterations in illumination sources, polarizations, frequencies, phases, viewing angles, or acquisition times.

[0220] By acquiring diverse measurements, the speckle-noise patterns in each image become statistically independent. This independence arises from variations in the quasirandom distribution and phase of scatterers contributing to the interference pattern across different measurements. Through appropriate processing and combination of these images, the influence of speckle noise may be mitigated, resulting in improved image quality, a higher signal-to-noise ratio, and more accurate information extraction.

[0221] The subsequent sections focus on various pixel architectures aimed at addressing the effects of speckle noise. In the context of this disclosure, a pixel architecture refers to any electro-optical system designed to emit an optical signal to a predetermined location in space and capture a reflected optical signal from that location. In simpler terms, it may encompass all electro-optical components traversed by an emitted or collected optical signal until detection, detector included. Within the realm of LIDAR systems, the term "pixel" derives from the constraint that this predetermined location in space corresponds to one point in the resulting image. These diverse structures may exhibit distinct characteristics related to efficiency, polarization, and speckle diversity, with certain designs optimizing one or more of these factors. This collection of electro-optical components may perform the function of the scanning unit 116, specifically the multiplexing / demultiplexing module 122, and the sensing unit 118 as previously described. A pixel architecture may span across these different units. Furthermore, these electro-optical systems may be integrated on a PIC in conjunction with an IC or Printed Circuit Board PCB, resulting in a fully integrated solution. Additionally, pixel architecture may be classified as either monostatic or bi static. In monostatic architectures, the transmitted light signal and the received light signal share at least part of their optical path, whereas bistatic architectures involve completely distinct optical paths for the transmitted and received light signals. In the context of monostatic architectures, multiple components may be traversed by both the transmitted and received light signals. Examples of such components include optical splitters, optical switches, or optical couplers.Polarization Beam Rotator Splitter (PBRS) - Monostatic Pixel Architecture

[0222] In some embodiments, a photonic integrated chip (PIC) for transmitting and detecting optical signals may comprise a transmitting waveguide. The transmitting waveguide may be configured to convey a transmission optical signal from a laser source. Asmentioned, optical waveguides refer to photonic structures crafted to confine and direct light propagation. In this specific instance, the transmitting waveguide may be configured to guide an optical signal emitted by a laser source (e.g., light source 112). Further details regarding transmitting waveguides are provided in the definition section of the present disclosure.

[0223] In some embodiments, the PIC chip may comprise a receiving waveguide. The receiving waveguide may be configured to convey a fraction of a reflected optical signal from a target toward a detection module, wherein the detection module is configured to detect the fraction of the reflected signal. In the present configuration, the receiving waveguide may be configured to deliver the reflected optical from a target to a detection module. Further details regarding receiving waveguides and detection modules are provided in the definition section of the present disclosure.

[0224] In some embodiments, the transmitting waveguide and the receiving waveguide may share one or more identical parameters, as outlined in the definitions section herein.

[0225] In some embodiments, the PIC chip may comprise a Polarization Beam Rotator Splitter (PBRS) including a first port, a second port, and a third port. Within the context of this disclosure, a PBRS corresponds to any optical device capable of manipulating the polarization state of an optical signal. Further details regarding PBRS are provided in the definitions section of the present disclosure.

[0226] In accordance with the disclosed embodiments, a PBRS may be fully integrated on a PIC chip. In such scenarios, the PBRS may be constructed using waveguides configured with characteristics designed to implement the functionalities described earlier. Fig. 10 illustrates an exemplary integrated PBRS structure 1000 consisting of two parallel coupled waveguides. This structure includes a first port 1002-1 dedicated to a first polarization state "Poh," a second port 1002-2 designed to convert / rotate the first polarization "Poh" into a second polarization state "Poh" or vice versa, and a third port 1002-3 capable of accommodating optical signals with either polarization state.

[0227] When an optical signal with polarization state "Poh" enters first port 1002-1, it traverses the upper waveguide and exits the structure at third port 1002-3 with the same polarization state. If an optical signal enters second port 1002-2 with polarization state "Poh," it traverses the lower waveguide, couples with the upper waveguide, undergoes a power transfer with a conversion of the polarization state, and exits at third port 1002-3 with the second polarization state "Poh" ("Poli"— "Poh"). Conversely, if a signal with polarizationstate "Poh" enters third port 1002-3, it traverses the upper waveguide and exits at first port 1002-1 while maintaining the polarization state "Poh." If a signal with polarization state "Poh" enters third port 1002-3, it traverses the upper waveguide, is transferred to the lower waveguide, and exits the structure at second port 1002-2 with its polarization state rotated to "Poh ("Poh"— "Poh")." When a mixture of optical signals with polarization states "Poh" and "Poh" enters the structure at third port 1002-3, each component is split, with each exiting respectively at first port 1002-1 with the same polarization state ("Poh") and at second port 1002-2 with its polarization state rotated ("Poh"— "Poh").

[0228] For waveguides featuring a rectangular cross-section, "Poh" and "Poh" may correspond to TEoo and TMoo, respectively. The conversion of TEoo into TMoo or vice versa relies on the principle of mode evolution. Starting from third port 1002-3 with a mixture of TEoo and TMoo modes, the process involves gradually increasing the rectangular crosssections of the upper waveguide, leading to the evolution of effective refractive indices for different electromagnetic modes. Hybridization of some modes, such as TMoo with TEio, may occur. In the adiabatic coupling region, supermodes spanning both waveguides are generated, with the transfer of certain supermodes from a broader waveguide to a narrower one or vice versa. At the onset of the coupling, TEoo and hybrid TMoo / TEio supermodes are well confined in the broad upper waveguide and may have minimal overlap with the narrow lower waveguide. Subsequently, the broad upper waveguide is narrowed, and the narrow lower waveguide is widened with a constant gap. At this stage, the TEoo supermode is well confined in the upper waveguide, while the TMoo / TEio supermode is well confined in the narrow waveguide. As the waveguides separate, the TEoo and TMoo / TEio supermodes of the adiabatic coupler evolve into the TEoo modes of the isolated upper and lower waveguides, respectively. It is to be appreciated that due to the geometric parameters of the upper and lower waveguides, these two waveguides are not single mode throughout their entire length. However, in the vicinity of the first port 1002-1 and the second port 1002-2, the dimensions of the rectangular cross-sections may be configured in such a way that the waveguides become locally single mode, sustaining only the TEoo mode for instance.

[0229] In some embodiments, the PIC chip may comprise a local oscillator (LO) light path. The LO light path may be configured to convey at least a sample portion of the transmission optical signal from the laser source to the detection module. Further details regarding local oscillator light paths are provided in the definitions section of the present disclosure.

[0230] Fig. 11 illustrates an exemplary PIC chip 1100 comprising a pixel architecture consistent with the disclosed embodiments. PIC chip 1100 includes a transmitting (Tx) waveguide 1102, a receiving (Rx) waveguide 1104 linked to a detection module 1106, a Polarization Beam Rotator Splitter (PBRS) 1108 with first 1108-1, second 1108-2, and third 1108-3 ports, represented as a schematic version of the double waveguide structure in Fig. 10, and a Local Oscillator (LO) light path 1110. Such a PIC chip may be utilized in a LIDAR system, such as LIDAR system 100 depicted in Fig. IB. Accordingly, transmitting waveguide 1102 may be configured to carry the transmission optical signal from the light source 112, assuming the role of a laser source. Various connection configurations may be considered for transmitting waveguide 1102 to convey the transmission optical signal from light source 112. For example, it may be directly connected to the laser source 112 or linked to one of the outputs of the optical distribution matrix 210, as demonstrated in Fig. 2A.

[0231] In some embodiments, the transmitting waveguide is coupled to the first port of the PBRS, and the receiving waveguide is coupled to the second port of the PBRS, or vice versa. For example, in the depicted structure in Fig. 11, transmitting waveguide 1102 is coupled to first port 1108-1 of PBRS 1108, while receiving waveguide 1104 is connected to second port 1108-2 of PBRS 1108. In alternative scenarios, transmitting waveguide 1102 could be connected to second port 1108-2 of PBRS 1108, and receiving waveguide 1104 to first port 1108-1 of PBRS 1108.

[0232] In some embodiments, the third port of the PBRS may be coupled to an output coupler. The output coupler may be configured to output the transmission optical signal and collect the reflected optical signal from the target. In this context, an output coupler refers to any optical component designed to facilitate efficient light coupling between integrated optical structures (e.g., waveguides, PBRS, etc.) and free-space optical beams. When an output coupler is configured for both emitting and collecting a free-space optical beam, it may be termed monostatic. Within the context of LIDAR systems, an output coupler may function as the intermediary component between the on-chip optical signals and the optical signals traversing the LIDAR system FOV. In the illustrated example in FIG. 11, third port 1108-3 of PBRS 1108 is connected to output coupler 1112, depicted as a square. In some embodiments, the output coupler may include an edge coupler or a grating coupler. For instance, output coupler 1112 may adopt a form similar to the ones illustrated in Fig. 7, featuring an edge coupler 710 and a grating coupler 720. Accordingly, output coupler 1112 may be configured to emit the transmission optical signal in a direction substantially in or parallel to the plane of the PIC 1100 or forming a non-zero angle with the normal of the planeof PIC 1100. Similarly, output coupler 1112 may collect light reflected from a target from a direction either in or out of the plane of PIC 1100. In cases where the PBRS 1108 and output coupler 1112 are structured based on waveguides, a continuity may be observed between the waveguides constituting PBRS 1108 and output coupler 1112, forming a single integrated structure within the PIC chip 1100. It is to be appreciated that given the capability of PBRS 1108 to handle optical signals of varying polarization states at its third port 1108-3, output coupler 1112 is also designed to accommodate optical signals exhibiting diverse polarization states.

[0233] In some embodiments, the PBRS may be configured to: transmit the transmission optical signal to the output coupler; convert a polarization state of an optical signal travelling from the second port to the third port or vice versa; separate the reflected optical signal from the target collected by the output coupler into a first divided optical signal and a second divided optical signal; output the first divided optical signal via the first port; and, output the second divided optical signal via the second port. This configuration allows the PBRS to handle multiple functions, including directing the transmission optical signal, converting polarization states, and / or separating the reflected optical signal into distinct components for output through the corresponding ports. Moreover, in some embodiments, the first divided optical signal and the second optical divided signal may be in a same polarization state.

[0234] In some embodiments, the fraction of the reflected optical signal from the target conveyed by the receiving waveguide and detected by the detection module may correspond to the first divided optical signal or the second divided optical signal. In other words, the nature of the detected fraction of the reflected optical signal depends on the specific structure of the PIC chip. For instance, in reference to Fig. 11, if the transmitting waveguide 1102 is connected to the first port 1108-1, and the receiving waveguide 1104 is connected to the second port 1108-2, the detected fraction of the reflected optical signal will correspond to the second divided optical signal. Conversely, if the configuration is inverted, the detected fraction will correspond to the first divided optical signal.

[0235] The overall efficiency of such a structure may be influenced by several factors, particularly the properties of output coupler 1112 and the polarization-maintaining characteristics of the target. For instance, in Fig. 11, assuming both transmitting waveguide 1102 and receiving waveguide 1104 are single mode and sustain the TEoo mode, PBRS 1108 may convert a TEoo mode into a TMoo mode for signals traveling from second port 1108-2 to third port 1108-3 or vice versa. The transmission optical signal with associatedelectromagnetic mode TEoo conveyed by transmitting waveguide 1102 is transmitted from first port 1108-1 to third port 1108-3 by PBRS 1108, and subsequently to output coupler 1112, where it is emitted as an optical beam (e.g., Gaussian beam) with a certain polarization state corresponding to the TEoo mode of the waveguide. Once the transmission optical beam hits a target and is reflected, the reflected optical signal, in the majority of cases, does not maintain polarization. Consequently, the reflected optical signal will have a random polarization not aligned with the TEoo mode. When the reflected optical signal is collected by the output coupler, the random polarization state may excite both TEoo and TMoo modes. The power distribution between TEoo and TMoo modes may be influenced by various characteristics, notably related to the design features of output coupler 1112. This power distribution directly impacts the power distribution of the first and second divided optical signals. In the embodiment illustrated in Fig. 11, only the second divided optical signal may be detected, and the efficiency is therefore directly correlated with the power distribution between TEoo and TMoo modes, as the transmission efficiency is equal to 100%. In some cases, the power distribution may be close to 50% for TE and 50% for TM, especially if the system has certain symmetries. However, in other cases, the distribution may be skewed towards one polarization state more than the other. It is to be appreciated that if the target maintains polarization (as might be the case for certain retroreflectors, or other reflective targets with smooth surfaces for example), the reflected optical signal conveyed by the receiving waveguide 1104 will be null. This is because all the collected reflected optical signal will be directed to the port of PBRS 1108 from which it originated (and thus connected to transmitting waveguide 1102), irrespective of the configuration, i.e., whether transmitting waveguide 1102 is connected to the first port 1108-1 or the second port 1108-2. In other words, regardless of the polarization state of the transmission optical signal beam, if the target maintains polarization, the reflected optical signal may excite the same mode in output coupler 1112 used for transmission.

[0236] In some embodiments, the PIC chip may further include an optical switch, as outlined in the definitions section herein. The optical switch may have a transmitting port coupled to the transmitting waveguide; a receiving port coupled to the receiving waveguide; a first transport port coupled to the first PBRS port; and a second transport port coupled to the second PBRS port.

[0237] Fig. 12A depicts the pixel architecture implemented on the PIC chip 1100 illustrated in Fig. 11, further featuring an optical switch 1202. The switch 1202 comprises a transmitting port 1212-1 connected to transmitting waveguide 1102, a receiving port 1212-2connected to receiving waveguide 1104, a first transport port 1212-3 connected to first port 1108-1 of PBRS 1108, and a second transport port 1212-4 connected to second port 1108-2 of PBRS 1108. Additionally, in some embodiments, the optical switch may have two modes of operation, namely bus mode and cross mode. In the bus mode, transmitting port 1212-1 is coupled to the first transport port 1212-3, and receiving port 1212-2 is coupled to second transport port 1212-4. Consequently, the fraction of the reflected optical signal from the target conveyed by receiving waveguide 1104 and detected by detection module 1106 corresponds to the second divided optical signal. On the other hand, in the cross mode, transmitting port 1212-1 is coupled to second transport port 1212-4 and receiving port 1212-2 is coupled to first transport port 1212-3. Accordingly, the fraction of the reflected optical signal from the target conveyed by receiving waveguide 1104 and detected by detection module 1106 corresponds to the first divided optical signal. These two modes of operation are illustrated in Fig. 12B.

[0238] In this way, optical switch 1202 enables a change from a state wherein transmitting waveguide 1102 is coupled to PBRS 1108 first port 1108-1 and receiving waveguide 1104 is coupled to PBRS 1008 second port 1108-2, to a state wherein transmitting waveguide 1102 is coupled to PBRS 1108 second port 1108-2 and receiving waveguide 1104 is coupled to PBRS 1008 first port 1108-1. These two modes of operation introduce speckle diversity in measurements, enabling the subsequent detection by switching modes of two different optical signals arising from distinct polarization states in the collection of the reflected optical signal. Such operation may provide more comprehensive information about the target during consecutive measurements with a single PIC chip pixel architecture. Such operation may also mitigate losses caused by speckle. For a single measurement, the state of the optical switch, combined with the signal received at the detector, may provide insights into the polarization-maintaining properties of the target. It should be noted that optical switches typically exhibit minimal optical losses. Consequently, in this configuration, the efficiency for a single measurement is predominantly determined by the power distribution of excited modes during collection. Additionally, irrespective of the mode of operation, be it bus mode or cross mode, a polarization-maintaining target may still result in a null fraction of the reflected optical signal.

[0239] Alternatively, in some other embodiments, the PIC further includes an optical splitter, as outlined in the definitions section herein. The optical splitter may have a transmitting port coupled to the transmitting waveguide; a receiving port coupled to the receiving waveguide; a first transport port coupled to the first PBRS port; and a secondtransport port coupled to the second PBRS port. Fig. 13 illustrates such a configuration, wherein optical splitter 1302 comprising a transmitting port 1312-1 coupled to transmitting waveguide 1102, a receiving port 1312-2 coupled to receiving waveguide 1104, a first transport port 1312-3 coupled to PBRS 1108 first input 1108-1, and a second transport port 1312-4 connected to PBRS 1108 second port 1108-2. As noted above an optical splitter may be regarded as a subcategory of a passive switch. In this configuration, while the transmission efficiency remains at 100%, the transmitted optical signal corresponds to a mixture of two polarization states. In contrast, the reception efficiency is no longer determined by the power distribution across polarization modes in the output coupler 1112, as both the first divided signal and the second divided signal are conveyed to the receiving waveguide 1104. Instead, it is fixed by the design of the optical splitter. For instance, in the case of a 50:50 e.g., 3dB splitter, the reception efficiency is fixed at 50%. It should be noted that with this configuration, the fraction of reflected optical signal is a combination of the first and second divided optical signals. Consequently, even in the presence of a polarization-maintaining target, the detected signal will not be null.

[0240] In some embodiments, the local oscillator light path may be directly coupled to the transmitting waveguide. For instance, referring to Fig. 11, local oscillator light path 1110 is directly coupled to transmitting waveguide 1102. Alternatively, in some other embodiments, the local oscillator light path may be directly coupled to the laser source. For example, local oscillator light 1110 may be coupled directly to laser source 112. The local oscillator signal may have the same modulation as the Tx signal. Alternatively, the local oscillator signal may be unmodulated (i.e. coupler to the laser source upstream from a laser modulator). In yet different embodiments, the local oscillator light path may be directly coupled to the third port of the PBRS. For example, local oscillator light path 1110 may be coupled to third port 1108-3 of PBRS 1108. In each of these example configurations, a sample portion of the transmission optical signal from laser source 112 may be extracted. Importantly, the characteristics of the transmission optical signal (e.g., wavelength, modulation pattern, etc.) may remain unchanged as it is conveyed from the laser source 112 to the output coupler 1112, even though the optical power levels may vary at different points along this path.

[0241] In some embodiments, the detection module may comprise an optical coupler, as outlined in the definitions section herein, configured to combine the at least one sample portion of the optical signal from the laser source conveyed by the local oscillator light path and the fraction of the reflected optical signal from the target conveyed by the receivingwaveguide to provide two combined signals. The detection module may further include a photodetector, as outlined in the definitions section herein, configured to detect the two combined signals. In this instance, the optical coupler may be configured to combine the at least one sample portion of the optical signal from the laser source (LO signal), with a fraction of the reflected optical signal from the target (Rx signal). This combination yields two combined signals. The combination may be a product of the two signals. In some embodiments, the optical coupler may include a directional coupler or a multimode interferometer, both of which are passive structures

[0242] In some embodiments, the photodetector may include a balanced photodetector, consisting of closely matched photodetectors operated differentially. When coupled with an optical coupler, a beat frequency between two incoming optical signals (e.g., LO and Rx signals) may be determined, providing an output that cancels common-mode components and which may enhance sensitivity to the differential signal. In the example illustrated in Fig. 11, detection module 1106 includes a directional coupler 1126 (e.g., a 50:50 e.g., 3dB optical splitter), acting as an optical coupler. Additionally, it incorporates a balanced photodetector 1116 designed to detect the two combined signals resulting from the mixing of the LO signal transmitted via LO optical path 1110 and the Rx signal conveyed through receiving waveguide 1104.

[0243] In some embodiments, the detection module may comprise a 90° optical hybrid, as outlined in the definitions section herein, configured to mix the at least one sample portion of the transmission optical signal from the laser source conveyed by the local oscillator light path with the fraction of the reflected optical signal conveyed by the receiving waveguide to provide a pair of in-phase combined signals and a pair of quadrature combined signal. The detection module may then further include a first balanced photodetector configured to detect the pair of in-phase combined signal and a second balanced photodetector configured to detect the pair of quadrature combined signal. Fig. 14 presents an exemplary pixel architecture, akin to the one in Fig. 12 A, where the detection module 1106 comprises a 90° optical hybrid 1402, a first balanced photodetector 1416-1, and a second balanced photodetector 1416-2. For complex IQ demodulation, in the context of the PIC chip 1100 pixel architecture, the Rx signal serves as the primary signal from one input, while the LO signal acts as the secondary signal. The output signals from the 90° optical hybrid includes components such as Rx+LO, Rx-LO, Rx+jLO, and Rx-jLO. These signals may be detected, for instance, by a pair of balanced photodetectors, as shown in Fig. 14 (1416-1 and 1416-2). An illustrative structural example of a 90° optical hybrid (420) isdepicted in Fig. 4C, demarcated by a black dashed line. In some embodiments, the 90° optical hybrid may be adjustable. For example, it may incorporate one or more optical phase tuners. Polarization Beam Rotator Splitter (PBRS) - Dual Monostatic Pixel Architecture

[0244] In some embodiments, a photonic integrated chip (PIC) for transmitting and detecting optical signals may comprise a transmitting waveguide. The transmitting waveguide may be configured to convey a transmission optical signal from a laser source. As mentioned, optical waveguides refer to photonic structures crafted to confine and direct light propagation. In this instance, the transmitting waveguide may be configured to guide an optical signal emitted by a laser source (e.g., light source 112). Further details regarding transmitting waveguides are provided in the definitions section of the present disclosure.

[0245] In some embodiments, the PIC chip may comprise a receiving waveguide. The receiving waveguide may be configured to convey a fraction of a reflected optical signal from a target toward a detection module, wherein the detection module is configured to detect the fraction of the reflected signal. In the present configuration, the receiving waveguide may be configured to deliver the reflected optical signal from a target to a detection module. Further details regarding receiving waveguides and detection modules are provided in the definitions section of the present disclosure. In some embodiments, the transmitting waveguide and the receiving waveguide may share one or more parameter values, as outlined in the definitions section herein.

[0246] In some embodiments, the PIC may comprise a first Polarization Beam Rotator Splitter (PBRS) including a first port, a second port, and a third port. As described in earlier sections, a PBRS refers to any sort of optical device capable of manipulating the polarization state of an optical signal. Further details regarding PBRSs are provided in the definitions section of the present disclosure. In accordance with the disclosed embodiments, a PBRS may be fully integrated on a PIC chip. An illustrative example of this integration is depicted in Fig. 10, showcasing a PBRS 1000 based on two parallel coupled waveguides. In a situation where both the transmitting and receiving waveguides feature a rectangular crosssection, the first mode (e.g. TEoo) and the second mode (e.g. TMoo) may represent two separate polarization states managed by the first PBRS.

[0247] In some embodiments, the PIC chip may comprise a second PBRS including a first port, a second port, and a third port. Notably, this second PBRS may be designed to execute operations akin to those of the first PBRS. For instance, both PBRS units may be configured to influence optical signals with comparable polarization states. In this context, itis observed that the design and structure of both the first and second PBRS may be fashioned to be analogous, emphasizing a deliberate similarity in their configurations. This design consistency may contribute to a harmonized functionality within the integrated system. Moreover, such an alignment in the structures may streamline the nanofabrication process. However, in some other scenarios, the first and second PBRS units may differ in their structural configurations while maintaining similar operational functionality.

[0248] In some embodiments, the PIC chip may comprise a local oscillator (LO) light path. The LO light path may be configured to convey at least a sample portion of the transmission optical signal from the laser source to the detection module. Further details regarding local oscillator light paths are provided in the definition sections of the present disclosure.

[0249] In some embodiments, the PIC chip may comprise an optical splitter, including a transmitting port, a receiving port, a first transport port, and a second transport port. The transmitting port may be coupled to the transmitting waveguide, the receiving port to the receiving waveguide, the first transport port to the second port of the first PBRS, and the second transport port may be coupled to the first port of the second PBRS. Additionally, the optical splitter may be configured to split the transmission optical signal to provide a first portion of the transmission optical signal at the first transport port and a second portion of the transmission optical signal at the second transport port. For example, in this instance, the optical splitter may be configured to divide the transmission optical signal into two segments: the first portion being directed to the first transport port and the second portion directed to the second transport port. Moreover, an optical splitter may receive multiple input signals, combining them and subsequently splitting the resulting combination to the output ports. In some embodiments, the optical splitter may include a directional coupler or a multimode interference coupler. Further details regarding optical splitter / couplers are provided in the definition section of the present disclosure.

[0250] Fig. 15A illustrates an exemplary PIC chip 1500 comprising a pixel architecture consistent with the disclosed embodiments. The components of PIC chip 1500 include a transmitting (Tx) waveguide 1502, a receiving (Rx) waveguide 1504 linked to a detection module 1506, a first PBRS 1508 with first 1508-1, second 1508-2, and third 1508-3 ports, a second PBRS 1510 with first 1510-1, second 1510-2, and third 1510-3 ports, a Local Oscillator (LO) light path 1512, and an optical splitter 1514. The transmitting port 1514-1 of the optical splitter is coupled to the transmitting waveguide 1502, the receiving port is coupled to the receiving waveguide 1504, the first transport port 1514-3 is coupled to thesecond port 1508-2 of the first PBRS 1508, and the second transport port is coupled to the first port 1510-1 of the second PBRS 1510. Both first PBRS 1508 and second PBRS 1510 are represented as schematic versions of the double waveguide structure in Fig. 10. In line with the disclosed embodiment, such a PIC chip may be utilized in a LIDAR system like LIDAR system 100 depicted in Fig. IB. Accordingly, transmitting waveguide 1502 may be configured to carry the transmission optical signal from the light source 112. Various connection configurations may be considered for transmitting waveguide 1502 to convey the transmission optical signal from light source 112. For example, it may be directly connected to the laser source 112 or linked to one of the outputs of the optical distribution matrix 210, as demonstrated in Fig. 2A.

[0251] In some embodiments, the third port of the first PBRS may be coupled to a first output coupler. The first output coupler may be configured to output the first portion of the transmission optical and collect a first portion of the reflected optical signal. As described above, an output coupler denotes any optical device designed to facilitate efficient light coupling between integrated optical structures, such as waveguides and PBRSs, and firee- space optical beams. Within the realm of LIDAR systems, an output coupler may function as the intermediary component between on-chip optical signals and those traversing the LIDAR system's FOV. Further details regarding output couplers / free-space couplers are provided in the definitions section of the present disclosure. In the illustrated example shown in Figure 15 A, the third port 1508-3 of the first PBRS 1508 is connected to the first output coupler 1516, depicted as a square.

[0252] In some embodiments, the first PBRS may configured to: transmit the first portion of the transmission optical signal to the first output coupler; convert a polarization state of an optical signal travelling from the second port of the first PBRS to the third port of the first PBRS or vice versa; separate the first portion of the reflected optical signal from the target collected by the first output coupler into a first divided optical signal and a second divided optical signal; and transmit the second divided optical signal to the first transport port of the optical splitter. This configuration allows the first PBRS 1508 to handle multiple functions, including directing the transmission optical signal, converting polarization states, and separating the first portion of the reflected optical signal into distinct components for output through the corresponding ports. Moreover, in some embodiments, the first divided optical signal and the second optical divided signal may be in a same polarization state. For example, those signals may adopt a first (e.g. TEoo) polarization state.

[0253] In some embodiments, the third port of the second PBRS may be coupled to a second output coupler. The second output coupler may be configured to output the second portion of the transmission optical signal and collect a second portion of the reflected optical signal. In the illustrated example shown in Fig. 15A, the third port 1510-3 of the second PBRS 1510 is connected to the second output coupler 1518, depicted as a square. In some embodiments, one or more of the first output coupler and the second output coupler may include an edge coupler or a grating coupler. For example, first output coupler 1516 and second output coupler 1518 may adopt a configuration akin to the couplers illustrated in Fig. 7, incorporating both an edge coupler 710 and a grating coupler 720. Consequently, these output couplers may be designed to emit the first and second portions of the transmission optical signal either substantially within the plane of PIC 1500 or at a non-zero angle with the normal of the PIC 1500 plane. Similarly, first output coupler 1516 and second output coupler 1518 may collect the first and second portions of the reflected optical signal from a target from a direction within or outside the plane of PIC 1500. In cases where both the first 1508 and second 1510 PBRSs and first 1516 and second 1518 output couplers are constructed using waveguides, there may exist continuity between the waveguides constituting the PBRSs 1508 / 1510 and the output couplers 1516 / 1518, forming a unified integrated structure within PIC chip 1500. Given the capability of first PBRS 1516 and second PBRS 1518 to handle optical signals of diverse polarization states at their respective third ports 1508-3 / 1510-3, first output coupler 1516 and second output coupler 1518 may also be engineered to accommodate optical signals exhibiting a range of polarization states. Furthermore, in certain embodiments, first output coupler 1516 and second output coupler 1518 may share a similar structure. This shared structural similarity may ensure consistent and harmonized performance between the two output couplers. Since both output couplers may be utilized in a monostatic configuration, the resulting pixel architecture within PIC chip 1500 may be referred to as a dual monostatic configuration.

[0254] In some embodiments, the second PBRS may be configured to: transmit to the second portion of the transmission optical signal to the second output coupler; convert a polarization state of an optical signal travelling from the second port of the second PBRS to the third port of the second PBRS or vice versa; separate the second portion of the reflected optical signal from the target collected by the second output coupler into a third divided optical signal and a fourth divided optical; and transmit the third divided optical signal to the second transport port of the optical splitter. Similar to the functionality of the first PBRS 1508, this configuration allows the second PBRS 1510 to handle multiple tasks,including directing the transmission optical signal, converting polarization states, and separation of the second portion of the reflected optical signal into distinct components for output through the corresponding ports. Additionally, in some embodiments, the third divided optical signal and the fourth divided optical signal may share the same polarization state. For instance, these signals may adopt a TEoo polarization state.

[0255] In some embodiments, the optical splitter may be further configured to combine the second divided optical signal with the third divided optical signal to provide the fraction of the reflected optical signal from the target conveyed by the receiving waveguide from the receiving port. After the first and second portions of the reflected optical signal are respectively collected by the first output coupler 1516 and the second output coupler 1518, the second and third divided optical signals resulting from the operations of the first PBRS 1508 and the second PBRS 1510 are directed back to the optical splitter 1514. As previously mentioned, when optical signals are provided at one or more input ports of an optical splitter, the splitter may combine these signals and split the resulting combination among its output ports. In this specific scenario, optical splitter 1514 may combine the second divided optical signal arriving from the second port 1508-2 of the first PBRS 1508 via the first transport port 1514-3 with the third divided optical signal arriving from the first port 1510-1 of the second PBRS 1510 via the second transport port 1514-4. The resulting combined signal may then be split between the transmitting port 1514-1 and the receiving port 1514-2. Consequently, the fraction of the reflected signal conveyed by the receiving waveguide 1504 and detected by the detection module 1506 may therefore correspond to a mixture of the second and third divided optical signals.

[0256] In some embodiments, the first portion of the transmission optical signal and the second portion of the transmission optical signal may spatially overlap over at least a predetermined distance and may spatially not overlap beyond the predetermined distance. The specific arrangement on PIC chip 1500 of the first output coupler 1516 and the second output coupler 1518 may be such that the first portion of the transmission optical signal (emitted by first output coupler 1516) and the second portion of the transmission optical signal (emitted by the second output coupler 1518) may spatially overlap over a predetermined distance and cease to overlap beyond the predetermined distance. Such overlap may be an indicator of a certain level of proximity between the first output coupler 1516 and the second output coupler 1518. In some embodiments, the spatial overlap may decrease along the predetermined distance. For example, as illustrated in Fig. 6B, the overlap between the first portion of the transmission optical signal and the second portion of thetransmission optical signal could start at 100% and then decrease gradually until reaching 0% at the predetermined distance. Consequently, the overlap may cease to exist beyond the predetermined distance.

[0257] Overlap between the first and second portions of the transmission optical signal may indicate that the two signals will address a substantially identical portion of a target. Likewise, the first and second portions of the reflected optical signals are collected from the same substantially identical portion of the target. Alternatively, in some embodiments, a distance between either the first output coupler 1516 or the second output coupler 1518 and the target may be greater than the predetermined distance. In other words, when reaching the target, the first portion of the transmission optical signal, emitted by first output coupler 1516, and the second portion of the transmission optical signal, emitted by the second output coupler 1518, do not overlap. They may therefore target different positions on a target.

[0258] In some embodiments, beyond the predetermined distance, an angular separation between the first portion of the transmission optical signal outputted by the first output coupler and the second portion of the transmission optical signal outputted by the second output coupler may be below an angular threshold. Put differently, beyond the predetermined distance where the portions of the transmission optical signal cease to overlap, the emitted beams (including a first beam for the first portion of the transmission optical signal outputted by the first output coupler and a second beam for the second portion of the transmission optical signal outputted by the second output coupler) may diverge but still maintain an angular separation below a certain threshold. For instance, in some embodiments, the angular threshold may be equal to 0.005 rad, signifying that these emitted beams have a minimal angular separation, ensuring that they remain within a small angular deviation from each other.

[0259] When implemented within a LIDAR system, the predetermined distance and the angular separation may be related to certain LIDAR properties. For instance, in some embodiments, the predetermined distance may be lower than a LIDAR system maximum range. This suggests that some targets falling below the predetermined distance within the LIDAR system range will experience overlapping beams, while those beyond the predetermined distance will not. More precisely, in some embodiments, the predetermined distance may be between 0.1 and 0.9 of the maximum range of the LIDAR system. Additionally, in some embodiments, the angular separation may be lower than a LIDAR system resolution, along a same axis. This implies that even though the two portions of thetransmission optical signal diverge and no longer overlap beyond the predetermined distance, their separation remains below the resolution limit of the LIDAR system. Consequently, from the perspective of the LIDAR system, these two beams, including the first beam for the first portion of the transmission optical signal outputted by the first output coupler and the second beam for the second portion of the transmission optical signal outputted by the second output coupled, transmitted via output couplers 1516 and 1518, while technically targeting different spatial positions on a target, will still be registered as a single data point, representing a unified pixel value in the LIDAR system.

[0260] In some embodiments, the local oscillator light path may be directly coupled to the transmitting waveguide. For instance, referring to Fig. 15 A, local oscillator light path 1512 is directly coupled to transmitting waveguide 1502. Alternatively, in some other embodiments, the local oscillator light path may be directly coupled to the laser source. For example, local oscillator light path 1512 may be coupled directly to laser source 112. In each of these example configurations, a sample portion of the transmission optical signal from laser source 112 may be extracted. Importantly, the characteristics of the transmission optical signal (e.g., wavelength, modulation pattern, etc.) may remain unchanged as it is conveyed from the laser source 112 to the first 1516 and second 1518 output couplers, even though the optical power levels may vary at different points along this path.

[0261] In some embodiments, the detection module may comprise an optical coupler, as outlined in the definitions section herein, configured to combine the at least one sample portion of the optical signal from the laser source conveyed by the local oscillator light path with the fraction of the reflected optical signal from the target conveyed by the receiving waveguide to provide two combined signals. The detection module may further include a photodetector, as outlined in the definitions section herein, configured to detect the two combined signals. In this instance, the optical coupler may be configured to combine the at least one sample portion of the optical signal from the laser source (LO signal), with a fraction of the reflected optical signal from the target (Rx signal). This combination yields two combined signals. The combination may be a product of the two signals. In some embodiments, the optical coupler may include a directional coupler or a multimode interferometer, both of which are passive structures. Further details regarding detection modules and optical couplers are provided in the definitions section of the present disclosure.

[0262] In some embodiments, the photodetector may include a balanced photodetector, consisting of closely matched photodetectors operated differentially. When coupled with an optical coupler, a beat frequency between two incoming optical signals (e.g.,LO and Rx signals) may be determined, providing an output that cancels common-mode components and which may enhance sensitivity to the differential signal. In the example illustrated in Fig. 15 A, detection module 1506 includes a directional coupler 1536 (e.g., a 50:50 e.g., 3dB optical splitter), acting as an optical coupler. Additionally, it incorporates a balanced photodetector 1526 designed to detect the two combined signals resulting from the mixing of the LO signal transmitted via LO optical path 1512 and the Rx signal conveyed through receiving waveguide 1504.

[0263] In some embodiments, the detection module may comprise a 90° optical hybrid, as outlined in the definition section herein, configured to mix the at least one sample portion of the transmission optical signal from the laser source conveyed by the local oscillator light path with the fraction of the reflected optical signal conveyed by the receiving waveguide to provide a pair of in-phase combined signals and a pair of quadrature combined signal. The detection module may then further include a first balanced photodetector configured to detect the pair of in-phase combined signal and a second balanced photodetector configured to detect the pair of quadrature combined signal. Fig. 15B presents an exemplary pixel architecture, akin to the one in Fig. 15 A, where the detection module 1506 comprises a 90° optical hybrid 1552, a first balanced photodetector 1562-1, and a second balanced photodetector 1562-2. For complex IQ demodulation, in the context of the PIC chip 1500 pixel architecture, the Rx signal serves as the primary signal from one input, while the LO signal acts as the secondary signal. The output signals from the 90° optical hybrid includes components such as Rx+LO, Rx-LO, Rx+jLO, and Rx-jLO. These signals may be detected, for instance, by a pair of balanced photodetectors, as shown in Fig. 15B (1562-1 and 1562-2).

[0264] An illustrative structural example of a 90° optical hybrid (420) is depicted in Fig. 4C, demarcated by a black dashed line. In some embodiments, the 90° optical hybrid may be adjustable. For example, it may incorporate one or more optical phase tuners.

[0265] The efficiency of a dual monostatic pixel architecture presented in Fig. 15 A may rely on various factors, including the allocation of weights to different ports of optical splitter 1514 and the splitting capacities of the first PBRS 1508 and the second PBRS 1510. For instance, assuming the optical splitter 1514 operates as a 50:50 splitter and both the first PBRS 1508 and the second PBRS 1510 transmit the same pair of polarization states and are configured to equally split the first and second portions of the reflected signal, the overall efficiency of the pixel architecture can be estimated at 25%. Specifically, 100% of the transmission optical signal is emitted, as optical splitter 1514 divides the transmission opticalsignal into two equal portions with 50% magnitude each. Subsequently, 50% of each of the first portion and the second portion of the reflected signal, with a magnitude equal to 50% of the overall reflected optical signal, is directed back to the optical splitter through the actions of the first PBRS 1508 and the second PBRS 1510. The optical splitter 1514 then combines these 50% fractions, namely the second divided optical signal and the third divided optical signal, and provides 50% of the combined signal to the receiving waveguide 1504 via its receiving port 1504-2.

[0266] The dual monostatic pixel architecture of the present disclosure may also enable the introduction of speckle diversity in the measurements. Specifically, the fraction of the reflected optical signal represents a combination of two distinct polarization states. The second divided optical signal, corresponding to a sub-portion of the first portion of the reflected optical signal, excites a mode with a polarization different (e.g., orthogonal) from the polarization of the mode excited by a sub-portion of the second portion of the reflected optical signal, corresponding to the third divided optical signal. For example, in a scenario involving waveguides and implemented structures with rectangular cross-sections, the fraction of the reflected optical signal detected by the detection module 1506 may correspond to a mixture of the second divided optical signal stemming from the excitation of the TMoo mode of the first output coupler 1516 and the third divided optical signal from the excitation of the TEoo mode of the second output coupler 1518. Similarly, diversity may be introduced in the transmission optical signal as the first and second portion of the transmission optical signal emitted by first 1516 and second 1518 output coupler may have two different polarization states.

[0267] In alternative embodiments, the coupling connections between optical splitter 1514 and the first PBRS 1508 and second PBRS 1510 may be exchanged. In these scenarios, the first transport port 1514-3 of the optical splitter 1514 may be connected to the first port 1508-1 of the first PBRS 1508, and the second transport port 1514-4 may be coupled to the second port 1510-2 of the second PBRS 1510. Alternatively, the first transport port 1514-3 of the optical splitter 1514 could be linked to the second port 1508-2 of the first PBRS 1508, and the second transport port 1514-4 may be connected to the second port 1510-2 of the second PBRS 1510. Another configuration may involve coupling the first transport port 1514-3 of the optical splitter 1514 to the first port 1508-1 of the first PBRS 1508, and the second transport port 1514-4 may be connected to the first port 1510-1 of the second PBRS 1510. These various configurations may function differently relative to the overall operation of the pixel architecture. Indeed, only two of these configurations may enable theintroduction of speckle / polarization diversity. The first of these two configurations corresponds to the configuration represented in FIG. 15 A. The second configuration involves the connection of the first transport port 1514-3 of the optical splitter 1514 with the first port 1508-1 of the first PBRS 1508 and the connection of the second transport port 1514-2 of the optical splitter 1514 with the second port 1510-2 of the second PBRS 1510, which may enable collection of a fraction of the reflected optical signal accounting for distinct collected polarization states (e.g., a mixture of TEoo and TMoo modes). The other two configurations will result in a fraction of the reflected optical signal corresponding to two identical collected polarization states (e.g., TEoo / TEoo or TMoo / TMoo).

[0268] In some embodiments, the PIC chip may further comprise a first additional receiving waveguide coupled to the first port of the first PBRS, configured to convey the first divided optical signal. Accordingly, the first PBRS may be further configured to transmit the first divided optical signal to the first additional receiving waveguide. In some embodiments, the cross-sectional dimensions of the first additional receiving waveguide may align with the wavelength order of magnitude. Within the context of a LIDAR system, the first additional receiving waveguide may assume the role of a first additional receiving channel. This waveguide functions as the conduit guiding the first additional fraction of the reflected optical signal (first divided optical signal - Rxi signal) different from the fraction conveyed by the receiving waveguide (Rx signal).

[0269] In some embodiments, the PIC chip may further comprise a second additional receiving waveguide coupled to the second port of the second PBRS, configured to convey the fourth divided optical signal. Accordingly, the second PBRS may be further configured to transmit the fourth divided optical signal to the second additional receiving waveguide. In some embodiments, the cross-sectional dimensions of the second additional receiving waveguide may align with the wavelength order of magnitude. Within the context of a LIDAR system, the second additional receiving waveguide may assume the role of a second additional receiving channel. This waveguide functions as the conduit guiding a second additional fraction of the reflected optical signal (fourth divided optical signal - Rx2 signal) different from the fraction conveyed by the receiving waveguide (Rx signal).

[0270] In some embodiments, the transmitting waveguide, the receiving waveguide, the first additional receiving waveguide, and the second additional receiving waveguide may share one or more identical parameters, as outlined in the definitions section herein.

[0271] In some embodiments, the PIC chip may further comprise a first additional detection module, configured to detect the first divided optical signal conveyed by the firstadditional receiving waveguide. The first additional detection module may be coupled to the first additional receiving waveguide.

[0272] In some embodiments, the PIC chip may further comprise a second additional detection module, configured to detect the fourth divided optical signal conveyed by the second additional receiving waveguide. The second additional detection module may be coupled to the second additional receiving waveguide.

[0273] In some embodiments, the PIC chip may further comprise a first additional local oscillator light path, as outlined in the definitions section herein, configured to convey at least one first additional sample portion of the transmission optical signal from the laser source to the first additional detection module. In applications like FMCW-LIDAR, the LOi signal (e.g., a first additional sample portion of the transmission optical signal) may be combined with the reflected optical signal Rxi (e.g., a first divided optical signal) to determine a beat frequency and estimate target range and velocity.

[0274] In some embodiments, the PIC chip may further comprise a second additional local oscillator light path configured to convey at least one second additional sample portion of the transmission optical signal from the laser source to the second additional detection module. In applications like FMCW-LIDAR, the LO2 signal (e.g., second additional sample portion of the transmission optical signal) may be combined with the reflected optical signal RX2 (e.g., fourth divided optical signal) to determine a beat frequency and estimate target range and velocity.

[0275] Fig. 15C depicts an exemplary PIC chip 1500, incorporating components from Fig. 15A and the additional elements outlined in the preceding paragraphs. This configuration includes a first additional receiving waveguide 1524, conveying the Rxi signal to a first additional detection module 1546, and a second additional receiving waveguide 1534, guiding the Rx2 signal to a second additional detection module 1576. The PIC chip also features a first additional local oscillator light path 1522 and a second additional local oscillator light path 1532. These paths provide a first additional sample portion of the transmission optical signal (LOi) and a second additional sample portion of the transmission optical signal (LO2) to the first 1546 and second 1576 additional detection modules, respectively.

[0276] In some embodiments, the first additional local oscillator light path and the second additional local oscillator light path may be directly coupled to the laser source. For instance, referring to Fig. 15C, first additional local oscillator light path 1522 and second additional local oscillator light path could be directly coupled to laser source 112.Alternatively, in some other embodiments, the first additional local oscillator light path and the second additional local oscillator light path may be directly coupled to the transmitting waveguide. For instance, referring to Fig. 15C, first additional local oscillator light path 1522 and second additional local oscillator light path 1532 may be directly coupled to transmitting waveguide 1502, akin to the situation illustrated for local oscillator light path 1512. Furthermore, in some embodiments, the sample portion of the transmission optical signal delivered by the local oscillator light path, the first additional sample portion delivered by the first additional local oscillator light path, and the second additional sample portion delivered by the second additional local oscillator light path may have substantially the same magnitude or may have different magnitudes. In some cases, all of these sample portions share the same properties (wavelength, modulation pattern, etc.) but may or may not differ in intensity.

[0277] In some embodiments, the first additional detection module may comprise a first additional optical coupler configured to combine the at least one first additional sample portion of the transmission optical signal from the laser source conveyed by the first additional local oscillator light path and the first divided optical signal conveyed by the first additional receiving waveguide to provide two first additional combined signals. The first additional detection module may further include a first additional photodetector configured to detect the two first additional combined signals. Additionally, in some embodiments, the second additional detection module may comprise a second additional optical coupler configured to combine the at least one second additional sample portion of the transmission optical signal from the laser source conveyed by the second additional local oscillator light path and the fourth divided optical signal conveyed by the first additional receiving waveguide to provide two second additional combined signals. The second additional detection module may further include a second additional photodetector configured to detect the two second additional combined signals. The terms "optical coupler" and photodetector are outlined in the definitions section herein.

[0278] In some embodiments, one or more of the first additional photodetector and the second additional photodetectors may include a balanced photodetector, consisting of closely matched photodetectors operated differentially. Alternatively, or additionally, in some embodiments one or more of the first additional optical coupler and the second additional optical coupler may include a directional coupler or a multimode interferometer coupler, both of which are passive structures

[0279] In the illustrated example of Fig. 15C, first additional detection module 1546 comprises a directional coupler 1566 functioning as a first additional optical coupler. It also integrates a balanced photodetector 1556 designed to detect the two first additional combined signals resulting from the mixing of the LOi signal transmitted via first additional LO optical path 1522 and the Rxi signal (first divided optical signal) conveyed through first additional receiving waveguide 1524. Similarly, second additional detection module 1576 includes a directional coupler 1596 acting as a second additional optical coupler, along with a balanced photodetector 1586 designed to detect the two second additional combined signals resulting from the mixing of the LO2 signal transmitted via second additional LO optical path 1532 and the RX2 signal (fourth divided optical signal) conveyed through second additional receiving waveguide 1534. In essence, the structure of the first 1546 and second 1576 additional detection modules may be identical to that of the detection module 1506.

[0280] In some embodiments, the detection module, the first additional detection module, and the second additional detection module may each output a current signal. Following the conversion of the optical signals using, for instance, a balanced photodetector, each of these detection modules can generate a current that is proportional to the respective signal being processed. Additionally, in some embodiments, the current signals from the detection module, the first additional detection module, and the second additional detection module may be combined by a short-circuit. This implies that the individual current signals may be directly merged or interconnected, typically with minimal impedance, facilitating their summation, integration, or aggregation. The short-circuiting process allows for the simultaneous consideration of information from different channels, enabling a consolidated analysis or processing of each of the combined signals collectively. The short circuiting saves components (e.g. ADCs). However, polarization information is lost in the event that the signals are combined. A short-circuit arrangement is depicted in Fig. 15C, where the outputs of first additional detection module 1546, detection module 1506, and second additional detection module 1576 are combined in a short-circuit configuration. Alternatively, in different embodiments, the current signals from the detection module, the first additional detection module, and the second additional detection module may undergo individual conversion into voltage signals (e.g., using a trans-impedance amplifier). Subsequently, these voltage signals may be combined or summed, employing a configuration such as a summing amplifier.

[0281] In some embodiments, the first additional detection module may comprise a first additional 90° optical hybrid configured to mix the at least one first additional sampleportion of the transmission optical signal from the laser source conveyed by the first additional local oscillator light path with the first divided optical signal conveyed by the first additional receiving waveguide to provide a first additional pair of in-phase combined signals and a first additional pair of quadrature combined signal. The first additional detection module may then further include a first additional balanced photodetector configured to detect the first additional pair of in-phase combined signal and a second additional balanced photodetector configured to detect the first additional pair of quadrature combined signal. Additionally in some embodiments, the second additional detection module may comprise a second additional 90° optical hybrid configured to mix the at least one second additional sample portion of the transmission optical signal from the laser source conveyed by the second additional local oscillator light path with the fourth divided optical signal conveyed by the second additional receiving waveguide to provide a second additional pair of in-phase combined signals and a second additional pair of quadrature combined signal. The second additional detection module may then further include a third additional balanced photodetector configured to detect the second additional pair of in-phase combined signal and a fourth additional balanced photodetector configured to detect the second additional pair of quadrature combined signal.

[0282] Similar to the configuration of detection module 1506 shown in Fig. 15B, both or either of first additional detection module 1546 and second additional detection module 1576 may include a 90° optical hybrid. Further details regarding optical hybrids are provided in the definitions section of the present disclosure. In the case of first additional detection module 1546, for complex IQ demodulation, the Rxi signal serves as the primary signal from one input, while the LOi signal acts as the secondary signal. The resulting output signal from the first additional 90° optical hybrid includes components such as Rxi+LOi, Rxi-LOi, Rxi+jLOi, and Rxi-jLOi. These components may be detected, for example, by a pair of balanced photodetectors. Similarly, for second additional detection module 1576, the Rx2 signal serves as the primary signal from one input, while the LO2 signal acts as the secondary signal for complex IQ demodulation. The output signal from the second additional 90° optical hybrid includes components such as RX2+LO2, RX2-LO2, Rx2+jLO2, and Rx2-jLO2. These components may also be detected, for instance, by a pair of balanced photodetectors.

[0283] Moreover, in some embodiments, at least one of the first additional 90° optical hybrid or the second additional 90° optical hybrid may be adjustable. For example, these 90° optical hybrids may incorporate one or more optical phase tuners.

[0284] Compared to the structure in Fig. 15 A, the dual monostatic pixel architecture in Fig. 15C may offer improved efficiency. This structure considers both the first and fourth divided optical signals in the measurement / detection process, which were previously not relied upon. The efficiency of this structure could reach or approach 75%, assuming that optical splitter 1514 functions as a 50:50 splitter and both first PBRS 1508 and second PBRS 1510 handle the same pair of polarization states, equally splitting the first and second portions of the reflected signal. Consequently, the structure in Fig. 15C, featuring two additional receiving channels (Rxi and Rxz), may demonstrate a threefold improvement compared to the Fig. 15A structure, which has a single receiving channel (Rx).

[0285] As previously mentioned, the coupling connections between optical splitter 1514 and the first 1508 and second PBRS 1510 units may be exchanged. Accordingly, in alternative embodiments, first additional receiving waveguide 1524 may be coupled to either first port 1508-1 or second port 1508-2 of first PBRS 1508 and provide a first or second divided optical signal to first additional detection module 1546 (which may be configured to detect either signal). Similarly, second additional receiving waveguide 1534 may be coupled to either first port 1510-1 or second port 1510-2 of second PBRS 1510 and provide an either third or fourth divided optical signal to second additional detection module 1576 (which may be configured to detect either signal). The principle remains that the first 1524 and second 1534 additional receiving waveguides are respectively attached to the remaining port of the first 1508 and second 1510 PBRS, i.e., the port not coupled to either the first 1514-3 or the second 1514-4 transport port of optical splitter 1514.

[0286] Irrespective of the chosen configuration, the dual monostatic pixel architecture depicted in Fig. 15C introduces speckle / polarization diversity in measurements. In all four possible setups, all four divided optical signals are detected. This implies that signals arising from the excitation of all modes of the first 1516 and second 1518 output couplers are captured. For instance, in a scenario involving waveguides and structures with rectangular cross-sections, the architecture in Fig. 15C would result in the following detections:• The first divided optical signal from the excitation of the TEoo mode (i.e., first TE mode) of the first output coupler 1516 detected by the first additional detection module 1546.• A combination of a mixture of the second divided optical signal from the excitation of the TMoo mode (i.e., first TM mode) of the first output coupler 1516 and the third divided optical signal from the excitation of the TEoo mode of the second output coupler 1518 detected by detection module 1506.• The fourth divided optical signal from the excitation of the TMoo mode of the second output coupler 1518 detected by the second additional detection module 1576.

[0287] The dual monostatic pixel architecture described in the preceding sections focuses on systems that may be capable of splitting an optical transmission signal into two portions, outputting them potentially in two overlapping positions with different or identical polarization states, and collecting and detecting two reflected signals distributed in divided signals representing diverse polarization collection configurations. While this architecture involves the separation of the transmission optical signal into two portions through the optical splitter's structure, the principle may be extended to two or more portions, for instance, by employing a tree of optical splitters. The following sections explore aspects of such a generic structure.

[0288] In some embodiments, a photonic integrated chip (PIC) for transmitting and detecting optical signals may comprise a transmitting waveguide. The transmitting waveguide may be configured to convey a transmission optical signal from a laser source. The transmitting waveguide may be characterized by different and may have cross-sectional dimensions that align with the wavelength order of magnitude of the conveyed signal. Further details regarding transmitting waveguides are provided in the definitions section of the present disclosure.

[0289] In some embodiments, the PIC chip may comprise one or more optical splitters, arranged in a binary tree structure of optical splitters comprising N layers with N being a natural number greater than zero. Each of the one or more optical splitters may include a transmitting port, a receiving port, a first output port, and a second output port. A total number of optical couplers may be equal to 2N-1. As used herein a binary tree refers to a hierarchical structure in composed of nodes arranged in layers, where each node has at most two child nodes. Nodes in a binary tree are organized in a way that each node can have zero, one, or two child nodes. The topmost node in a binary tree is called the root, and nodes with no child are called leaves or terminal nodes. In the context of a binary tree structure of optical splitters, each node may represent an independent optical splitter. In some embodiments, each of the one or more optical splitters may include a directional coupler or a multimode interference coupler. Further details regarding optical splitters are provided in the definitions section of the present disclosure.

[0290] In some embodiments, the PIC chip may comprise a plurality of Polarization Beam Rotator Splitters (PBRSs), each including a first port, a second port, and a third port. Each third port may be coupled to an associated output coupler from among a plurality ofoutput couplers configured to output a portion of the transmission optical signal from the laser source and collect a portion of a reflected optical signal from a target. A total number of PRBSs and of output couplers may be equal to 2N. P...

Claims

WHAT IS CLAIMED IS:

1. An electro-optical demultiplexing / multiplexing module comprising: a plurality of transmitting optical waveguides each configured to transmit an optical signal; a plurality of receiving optical waveguides each configured to receive an optical signal, wherein each receiving optical waveguide is associated with a corresponding one of the plurality of transmitting optical waveguides; an optical distribution matrix comprising at least one input and a plurality of outputs, each output being coupled to one of the plurality of transmitting optical waveguides, configured to: selectively distribute an optical output signal generated by a light source to the plurality of transmitting optical waveguides; and an electro-optical reception matrix comprising a plurality of inputs, each input being coupled to one of the plurality of receiving optical waveguides and associated with one of the plurality of outputs of the optical distribution matrix, and at least one output, the electro-optical reception matrix configured to: mix, for each particular receiving waveguide among the plurality of receiving waveguides, a portion of the optical output signal generated by the light source with the optical signal received by the particular receiving waveguide to provide a plurality of interference signals, one for each of the plurality of receiving waveguides; generate a plurality of electronic signal outputs, one for each of the plurality of interference signals; and sum all of the plurality of electronic signal outputs to provide a summed signal to the at least one output.

2. The module of claim 1 wherein the portion of the optical output signal generated by the light source is supplied via a local oscillator light path.

3. The module of claim 2, wherein the local oscillator light path is directly coupled to the light source.

4. The module of claim 2, wherein the local oscillator light path is directly coupled to at least one of the plurality of outputs of the optical distribution matrix.

5. The module of claim 2, wherein the local oscillator light path is directly coupled to at least one of the plurality of transmitting optical waveguides.

6. The module of claim 1, wherein each of the plurality of inputs of the electro-optical reception matrix has a local oscillator light path coupled to the associated output of the optical distribution matrix.

7. The module of claim 1, wherein the optical distribution matrix is based on a plurality of optical switches arranged in a tree structure.

8. The module of claim 7, wherein the optical switches include at least one of Mach- Zehnder interferometers, micro-ring resonators, electro-optic switches, thermo-optic switches, or a combination thereof.

9. The module of claim 1, wherein the optical distribution matrix is based on a bus waveguide coupled to a plurality of micro-ring switches, each micro-ring switch being coupled with a corresponding one of the plurality of transmitting waveguides.

10. The module of claim 9, wherein the micro-ring switches are electronically controlled.

11. The module of claim 10, wherein the optical distribution matrix is based on a plurality of MEMS switches.

12. The module of claim 1, wherein the optical distribution matrix is based on a wavelength demultiplexer and each transmitting waveguide is associated with a specific wavelength range.

13. The module of claim 1, wherein each output of the optical distribution matrix is coupled to one of the plurality of transmitting optical waveguides through at least one electro-optical component.

14. The module of claim 13, wherein the at least one electro-optical component is a polarization beam splitter.

15. The module of claim 1, wherein the electro-optical reception matrix includes, for each input, at least one coupler and at least one photodetector.

16. The module of claim 15, wherein the at least one coupler is at least one of a directional coupler or a multimode interferometer.

17. The module of claim 15, wherein the at least one photodetector is a balanced photodetector.

18. The module of claim 15, wherein each electro-optical reception matrix input is split before the at least one coupler to generate complex I-Q demodulation.

19. The module of claim 15, wherein the electro-optical reception matrix further includes, for each input, at least one resistor connected to the photodetector.

20. The module of claim 19, wherein the at least one resistor is connected on a lower side of the photodetector power supply or on a higher side of the photodetector power supply.

21. The module of claim 19, wherein the electro-optical reception matrix is further configured to generate a plurality of electronic control signals, one for each of the plurality of interference signals.

22. The module of claim 19, wherein the electro-optical reception matrix is further configured to provide the plurality of electronic control signal outputs to a monitoring unit connected to the optical distribution matrix.

23. The module of claim 22, wherein the monitoring unit is configured to, based on the plurality of electronic control signal outputs, provide a feedback signal to the optical distribution matrix to tune the selective distribution of the optical output signal generated by the light source to the plurality of transmitting optical waveguides.

24. The module of claim 22, wherein the monitoring unit is configured to determine leakage signals associated with the at least one photodetector of each of the electro- optical reception matrix inputs, based on the plurality of electronic control signals.

25. The module of claim 22, wherein the monitoring unit is configured to determine an ambient light level, based on the plurality of electronic control signals.

26. The module of claim 25, wherein multiple ambient light levels are measured and grouped to form a two-dimensional image.

27. The module of claim 22, wherein the monitoring unit is configured to mitigate blooming effects, based on the plurality of electronic control signals.

28. The module of claim 1, wherein the electro-optical reception matrix includes at least one trans-impedance amplifier and summing all of the plurality of electronic signal outputs comprises at least one of: short circuiting the plurality of electronic signal outputs currents into the at least one transimpedance amplifier to provide a summed voltage signal to the at least one output; converting the plurality of electronic signal outputs currents into a plurality of electronic signal outputs voltages using the at least one trans-impedance amplifier and summing electronic signal outputs voltages to provide a summed voltage signal to the at least one output; or, a combination thereof.

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