Coherent focal plane array with shared photodetectors

Abstract

A photonic integrated circuit has a coherent focal plane array architecture that contains an array of coherent detection pixels and in which adjacent pixels in the same row or in the same column share one or more waveguide photodetectors and one or more associated transimpedance amplifiers. For example, a pair of two pixels that share one or more common photodetectors may be situated on separate buses, such that a laser light signal can be toggled between the two pixels using an optical switch. By having one set of photodetectors shared between the two pixels in such a pair, this architecture reduces the average number of components per pixel, therefore allowing for a reduction in pixel pitch.

Description

COHERENT FOCAL PLANE ARRAY WITH SHARED PHOTODETECTORSTECHNICAL FIELD

[0001] The subject matter disclosed herein generally relates to the technical field of special-purpose machines that facilitate three-dimensional (3D) imaging and to the technologies by which such special-purpose devices become improved compared to other special-purpose devices that facilitate 3D imaging. Specifically, the present disclosure addresses systems and methods to facilitate 3D imaging based on light detection and ranging (LIDAR), including Frequency Modulated Continuous Wave (FMCW) LIDAR.BACKGROUND

[0002] Optical ranging systems can bounce light off an object and ascertain the object’s distance by comparing the transmitted and reflected light. Conventional optical ranging systems are large unwieldly systems that require many parts. Such systems can be difficult to integrate into real world applications, such as autonomous vehicle object detection systems.BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Some embodiments are illustrated by way of example and not limitation in the figures of the accompanying drawings.

[0004] FIG. 1 is a diagram illustrating components of an integrated three- dimensional imaging system that is based on frequency modulation LIDAR and includes a coherent focal plane array, according to some example embodiments.

[0005] FIG. 2 is a diagram illustrating components of an integrated three- dimensional imaging system that is based on frequency modulation LIDAR and includesa coherent focal plane array, with a laser source external to a laser frequency modulator, according to some example embodiments.

[0006] FIG. 3 is a diagram illustrating a sensor with a coherent focal plane array of pixels and a multi-channel parallel readout, and with an optical switching block positioned outside the coherent focal plane array, according to some example embodiments.

[0007] FIG. 4 is a diagram illustrating a sensor with a coherent focal plane array of pixels, two symmetrical switching blocks positioned outside the coherent focal plane array, and two parallel readout electronic blocks, according to some example embodiments.

[0008] FIG. 5 is a diagram illustrating an architecture, for a coherent optical pixel array, using a combination of optical switching blocks, with some switching blocks positioned outside the coherent optical pixel array and some switching blocks positioned inside the coherent optical pixel array and embedded between blocks of pixels, according to some example embodiments.

[0009] FIG. 6 is a diagram illustrating a two-dimensional block of pixels in a coherent focal plane array, using a compact embedded switch whose outputs are each connected to a corresponding one-dimensional row of pixels, according to some example embodiments.

[0010] FIG. 7 is a diagram illustrating a two-dimensional block of pixels with pairs of pixels sharing pairs of photodiodes, according to some example embodiments.

[0011] FIG. 8 is a diagram illustrating three different pixel configurations that each may be used in various configurations of shared photodiodes, according to some example embodiments.

[0012] FIG. 9 is a diagram illustrating a row of pixels in which pairs of adjacent pixels share photodiodes and associated TIAs, according to some example embodiments.

[0013] FIG. 10 is a diagram illustrating a top half of a sensor with a coherent focal plane array of pixels, with optical switches positioned outside the coherent focal plane array, according to some example embodiments.

[0014] FIG. 11 is a diagram illustrating a top half of a sensor with a coherent focal plane array, with optical switches both outside the coherent focal plane array and embedded inside the coherent focal plane array, according to some example embodiments.

[0015] FIG. 12 is a diagram illustrating a quadrant of a sensor with a coherent focal plane array, with optical switches both outside the coherent focal plane array and embedded inside the coherent focal plane array, according to some example embodiments.

[0016] FIG. 13 is a diagram illustrating a 1x8 optical switch positioned at the top of the pixel block and compatible with delivery of high optical power into each line of pixels in the pixel block, according to some example embodiments.

[0017] FIG. 14 is a diagram illustrating a monostatic system with a coherent focal plane array, according to some example embodiments.

[0018] FIG. 15 is a diagram illustrating a bistatic system with a coherent focal plane array, according to some example embodiments.

[0019] FIG. 16 is a diagram illustrating a two-dimensional block of pixels with pairs of pixels sharing pairs of photodiodes, according to some example embodiments.

[0020] FIG. 17 is a diagram illustrating a two-dimensional block of pixels with pairs of pixels sharing pairs of photodiodes, according to some example embodiments.

[0021] FIG. 18 is a top view of an example of a shared photodetector.

[0022] FIG. 19 is a sectional view of the example of FIG. 18.DETAILED DESCRIPTION

[0023] Example methods (e.g., algorithms) facilitate providing a coherent focal plane array with a shared photodetector (e.g., a shared photodiode), and example systems (e.g., special-purpose machines configured by special-purpose software) are configured to facilitate provision of a coherent focal plane array with a shared photodetector.Examples merely typify possible variations. Unless explicitly stated otherwise, structures (e.g., structural components, such as modules) are optional and may be combined or subdivided, and operations (e.g., in a procedure, algorithm, or other function) may vary in sequence or be combined or subdivided. In the following description, for purposes of explanation, numerous specific details are set forth to provide a thorough understanding of various example embodiments. It will be evident to one skilled in the art, however, that the present subject matter may be practiced without these specific details.

[0024] A large variety of hardware implementations exist for 3D imaging based on FMCW LIDAR. The overwhelming majority use one or more pairs formed by a FMCW transmitter and a corresponding receiver (e.g., a FMCW transceiver) that provide an outbound modulated laser beam signal and detection of a return signal, respectively. A steering mechanism typically scans the outbound beam over the target, and in most cases, the implementation of the steering is mechanical in nature.

[0025] Recent advances in large scale optoelectronics integration have enabled a different architecture in which very large two-dimensional (2D) arrays of coherent detection pixels are used to establish a one-to-one correspondence between a point on the target to be imaged and a coherent detection pixel. This architecture allows for each pixel to provide the (x, y, z) coordinates of the point on the target, as well as velocity information, reflectivity information, or other information of the target, therefore eliminating the complexity associated with steering a laser beam and enabling fully solid state hardware implementations.

[0026] The most popular material for implementation of coherent focal plane arrays (e.g., focal plane arrays of coherent optical pixels) in photonics (e.g., photonicintegrated circuits) is silicon, a semiconductor material, due to its low cost and the maturity of its manufacturing processes. While successful implementations using silicon photonics and sub-micron silicon nanowires have been demonstrated, the design and manufacturing of coherent focal plane arrays is in its early stages, and a reduction in effective pixel pitch by several folds may be desirable to increase performance and reduce cost and therefore drive further adoption.

[0027] The present subject matter describes an architecture (e.g., for a coherent focal plane array) that contains an array of coherent detection pixels and in which adjacent pixels in the same row or in the same column share one or more waveguide photodetectors (e.g., photodiodes) and one or more associated (e.g., corresponding) transimpedance amplifiers (HAs). For example, two pixels (e.g., two paired pixels) that share one or more common photodetectors may be situated on separate buses, such that light (e.g., a laser light signal) can be toggled between the two pixels using an optical switch. By having one set of detectors (e.g., photodetectors) and corresponding TIAs shared between the two pixels in such a pair, this architecture reduces the average number of components per pixel, therefore allowing for a reduction in pixel pitch. Thus, a coherent focal plane array using (e.g., embodying or configured in accordance with) this architecture may be deemed as a compact coherent focal plane array.

[0028] Accordingly, a system (e.g., a three-dimensional imaging system) in accordance with the present architecture may be composed of (e.g., exclusively or non- exclusively) a frequency modulated laser source, an ensemble of multiplexing and demultiplexing assemblies, a plurality of optical switches, and a one dimensional or two dimensional focal plane array of coherent transceiver pixels and their associated electronics. In some example embodiments, one or more of these components or functions thereof are integrated monolithically into a single chip. To achieve a very small pixel size that would enable very large arrays of pixels, a material that provides high confinement for one or more optical signals may be desirable. In addition, one or more select active optical functions, such as phase modulation, frequency modulation, amplitude modulation, and detection of an optical signal, may be implements on the single chip, to enable an integrated three-dimensional imaging system.

[0029] A semiconductor optical material has the ability to perform active optical functions, as well as provide a high-index contrast that may be helpful in creating very small circuits, such as when paired with a native oxide cladding. On the other hand, a dielectric optical material may be helpful for passive routing, especially along a transmitter path where optical power is high, as dielectric optical material typically does not suffer negative effects due to early onset of nonlinear absorption and hence is able to sustain much larger light (e.g., laser light) intensities.

[0030] In some example embodiments, a photonic integrated circuit combines a dielectric material for passive optical functions, such as routing, multiplexing, and demultiplexing, and a semiconductor material for active optical functions, such as phase modulation, frequency modulation, and amplitude modulation, and light detection, as well as for dense routing in areas of the photonic integrated circuit with low inwaveguide laser light intensity.

[0031] In some example embodiments, a pixel is made using a semiconductor material to allow for a very small pixel design, while out-of-pixel routing is made using a dielectric material to allow for high intensity.

[0032] In some example embodiments, optical switching is separated into optical phase control, which is to be performed in a semiconductor material, and multiplexing, demultiplexing, and routing, which are to be performed in a dielectric material, with semiconductor-to-dielectric couplers and dielectric-to-semiconductor couplers enabling transitions between the two types of material.

[0033] In some example embodiments, one or more modulators of optical frequency, optical phase, or optical amplitude are made using a semiconductor material, for performing one or more active optical functions. On one or more transmit paths, the photonic integrated circuit may split optical power into multiple parallel channels prior to reaching the active optical sections implemented in the semiconductor material, to avoid onset of nonlinear absorption effects, and then recombined once the one or more active optical functions are accomplished.

[0034] In some example embodiments, the semiconductor material is silicon, with germanium-on-silicon photodetectors (e.g., waveguide photodetectors).

[0035] In some example embodiments, the dielectric material is silicon nitride.

[0036] In some example embodiments, all optical functions, both passive and active, are achieved using (e.g., performed within) the semiconductor material.

[0037] In some example embodiments, the wavelength of the light (e.g., the laser light signal) is larger than 1 micron though lower than 2 microns.

[0038] In some example embodiments, one or more of multiple functions (e.g., passive, active, or any suitable combination thereof) are monolithically integrated into a single photonic integrated circuit (e.g., a single chip).

[0039] FIG. 1 is a diagram illustrating components of an integrated three- dimensional imaging system 100 that is based on frequency modulation LIDAR and includes a coherent focal plane array, according to some example embodiments. In the example embodiments shown in FIG. 1, the imaging system 100 is composed of a modulated optical frequency laser source 102, an optical amplification and splitting module 103, a coherent focal plane array sensor 104, one or more corresponding drivers and control electronics 101 (e.g., for a transmit section of the system), and corresponding signal processor 105 (e.g., a parallel signal processor configured to perform analog-to- digital conversion, Fast Fourier Transforms (FFT), filtering, or other signal processing).

[0040] A frequency modulated optical laser signal is generated by the modulated optical frequency laser source 102. The modulated optical signal may be then split into multiple optical paths and amplified in the optical amplification and splitting module 103 (e.g., an optical amplification and splitting block) and supplied to coherent focal plane array of pixels in the coherent focal plane array sensor 104. Outgoing optical signals from pixels in the coherent focal plane array sensor 104 are directed towards a lens and from there towards a target (e.g., a target object). Incoming return signals from the target is passed through a lens (e.g., the same lens as before) and then coupled back into the pixels in the coherent focal plane array sensor 104, which transforms the optical returnsignals into electrical signals. The electrical signals generated by the coherent focal plane array sensor are sent (e.g., through multiple channels) to the signal processor 105, which performs conversion of each electrical signal from the analog domain to the digital domain. After the conversion from analog to digital, the signal processor 105 performs an FFT or other technique on the digitized electrical signal to extract frequency content of the electrical signal, as well as filtering or any other functions for improving the signal-to-noise ratio or for extracting target-related information from the digitized electrical signal.

[0041] FIG. 2 is a diagram illustrating components of the integrated three- dimensional imaging system 100, which is based on frequency modulation LIDAR and includes a coherent focal plane array, with a laser source 107 (e.g., a fixed frequency laser source) external to an optical frequency modulator 106, according to some example embodiments. The laser source 107 and the optical frequency modulator 106, in combination, may be function like the modulated optical frequency laser source 102, as discussed above with respect to FIG. 1. In the example embodiments shown in FIG. 2, a modulated optical signal is created external to the laser source 107 by externally modulating the light from the laser source 107 using the optical frequency modulator 106. In some example embodiments, the optical frequency modulator 106 is or includes a semiconductor in-phase quadrature single-sideband modulator. The frequency modulated signal generated by the combination of the laser source 107 and the optical frequency modulator 106 is sent to an input of the optical amplification and splitting module 103. In some example embodiments, the frequency modulated optical signal is first split in to multiple parallel paths and then amplified. In alternative example embodiments, the frequency modulated optical signal is first amplified and then split into multiple parallel paths. A plurality of frequency modulated optical signals from the output of the optical amplification and splitting module 103 is then directed to a plurality of p inputs of the coherent focal plane array sensor 104.

[0042] FIG. 3 is a diagram illustrating the coherent focal plane array sensor 104 with a coherent focal plane array 203 of pixels and a multi-channel parallel readout 204, and with an optical switching block 202 positioned outside the coherent focal plane array203, according to some example embodiments. In the example embodiments shown in FIG. 3, a plurality of p optical signals 201 inputted into the coherent focal plane array sensor 104 are directed to one or more inputs of the optical switching block 202 (e.g., an out-of-array optical switching block), which directs the plurality of p optical signals 201 to p outputs of the p times n outputs of the optical switching block 202. The plurality of p optical signals 201 are directed to pixels of the coherent focal plane array 203 of pixels and, in certain example embodiments, for each further split, into q parallel optical signals. The p times q outbound optical signals are sent towards the target, and a p times q plurality of reflected optical signals are received and detected by the pixels in the coherent focal plane array 203 of pixels. The return optical signals are detected by photodetectors (e.g., photodiodes) that are part of the pixels (e.g., according to various example embodiments, such as variants 504, 505, or 506 of pixels, discussed below with respect to FIG. 8), and a plurality of p times q analog electrical signals are generated by the photodetectors. The plurality of p times q electrical analog signals are then directed towards the multi-channel parallel readout 204 and from there to a corresponding signal processor (e.g., signal processor 105).

[0043] FIG. 4 is a diagram illustrating the coherent focal plane array sensor 104 with a coherent focal plane array 203 of pixels, two symmetrical optical switching blocks 202 positioned outside the coherent focal plane array 203, and two multi-channel parallel readouts 204 (e.g., multi-channel parallel readout electronic blocks), according to some example embodiments.

[0044] In the example embodiments shown in FIG. 4, a plurality of 2p optical signals 201 inputted into the coherent focal plane array sensor 104 are provided to the optical switching blocks 202 (e.g., two out-of-array optical switching blocks) and subsequently to the coherent focal plane array 203 of pixels, which may have one or more optional in-array switches. In some example embodiments, the coherent focal plane array 203 of pixels has two times p times n times q pixels where p is the number of parallel input channels (e.g., for receiving the optical signals 201), n is the number of switching outputs for each switch in the out-of-array and in-array switches, and q is the number of pixels to which each output of the optical switches provides lightcontemporaneously (e.g., simultaneously). In certain example embodiments, the signals from the 2xpxnxq coherent focal plane array 203 of pixels are provided to two parallel readout blocks (e.g., multi-channel parallel readouts 204), which may have p x q channels each.

[0045] FIG. 5 is a diagram illustrating an architecture, for a coherent optical pixel array, using a combination of optical switching blocks, with some switching blocks positioned outside the coherent optical pixel array and some switching blocks positioned inside the coherent optical pixel array and embedded between blocks of pixels, according to some example embodiments. In the example embodiments shown in FIG. 5, the plurality of p parallel optical signals is directed into p optical switches 301 situated outside a coherent focal plane array 302 of pixels (e.g., an array of coherent detection pixels). The optical signals exiting one of the n outputs of the optical switches 301 are directed to the input of an optical switch 303 that is embedded inside the coherent focal plane array 203 of pixels.

[0046] FIG. 6 is a diagram illustrating a two-dimensional block of pixels in a coherent focal plane array, using a compact embedded switch whose outputs are each connected to a corresponding one-dimensional row of pixels, according to some example embodiments. In the example embodiments shown in FIG. 6, an optical switch 303 has a folded architecture 401 to reduce its footprint and therefore reduce gaps between subsequent (e.g., downstream) pixel blocks. The outputs of the folded optical switch 303 are connected to optical buses 403 that distribute optical signal into individual optical pixels 404 (e.g., coherent optical pixels). In some example embodiments, control electronics 402 for the optical switch 303, and optionally one or more other optical switches, is placed at the top of the block of pixels. In certain example embodiments, the input to the next block of pixels is directed horizontally between the blocks.

[0047] FIG. 7 is a diagram illustrating a two-dimensional block 500 of pixels with pairs of pixels sharing pairs of photodiodes, according to some example embodiments. In the example embodiments shown in FIG. 7, an optical signal inputted into the block 500 of pixels is toggled between two adjacent optical buses 501 with odd pixels (e.g.,pixel 405) being supplied with light (e.g., one or more optical signals, such as laser light signals) by one optical bus 501, while even pixels (e.g., pixels 404 and 406) are supplied with light by the other optical bus 501 (also referenced as optical bus 403). The light from the optical bus 403 supplying the even pixels (e.g., pixels 404 and 406) may be split by one or more optical couplers 503, and a portion of the light is directed to the even pixels (e.g., pixels 404 and 406).

[0048] The two optical buses 501 may be connected (e.g., upstream, by an optical switch 303) and may receive light from two different outputs of a shared optical switch (e.g., optical switch 303). In one mode (e.g., one switch position) of the switch 303, the top optical bus 501 is provided with light (e.g., one or more optical signals) and in turn provides light to the even pixels (e.g., pixel 406). In another mode (e.g., another switch position) of the switch 303, the lower optical bus 501 is provided with light and in turn provides light to the odd pixels (e.g., pixel 405).

[0049] In some example embodiments, one side of a photodiode 502 is connected to an odd pixel (e.g., pixel 405) while the other side of the same photodiode 502 is connected to an even pixel (e.g., pixel 406). Since the odd pixels (e.g., pixel 405) and the even pixels (e.g., pixel 406) are connected to separate optical signal buses 501, which are not simultaneously provided with light (e.g., optical signals), or are otherwise configured to be mutually exclusive, the photodiodes (e.g., photodiode 502) will read, detect, receive, or otherwise process return signals for odd pixels (e.g., pixel 405) when their corresponding optical bus (e.g., optical bus 403) is provided with light, and the photodiodes (e.g., photodiode 502) will read, detect, receive, or otherwise process return signals from the even pixels (e.g., pixel 406) when their corresponding optical bus is provided with light.

[0050] In certain example embodiments, two adjacent optical signal buses 501 receive light from the outputs of two different optical switches (e.g., similar to optical switch 303) or from two different optical outputs of the same optical switch (e.g., optical switch 303), which may result in undersampling the pixels (e.g., sampling only every other pixel). In various example embodiments, one or more rows of pixels with sharedphotodiodes are combined with one or more rows without shared photodiodes (e.g., rows with only one pixel per one photodiode pair).

[0051] In a compact design, the signal buses 501 may extend along the rows of pixels.

[0052] FIG. 8 is a diagram illustrating three different pixel configurations that each may be used in various configurations of shared photodiodes, according to some example embodiments. In particular, FIG. 8 shows three (3) variants of a pixel architecture for an array of optical pixels (e.g., coherent pixels, detection pixels, or any suitable combination thereof), including one variant that is based on a transverse mode multiplexer and two other variants that are based on polarization mode multiplexing between outbound and inbound optical signals.

[0053] In one variant, the inputted optical signal is directed into the pixel though a coupler 512 and then split (e.g., by a splitter 515) into two portions. A first portion is directed towards a coupler 510, then towards one or more grating couplers 511, and then further towards the target (e.g., the target object). A second portion is directed towards a coupler 513 and then towards one or more photodetectors 514. The return signal reflected from the target is coupled back into the pixel through one or more grating couplers 511 and directed towards a coupler 510, then towards another coupler 513, and then further towards one or more photodetectors 514, where the return signal is mixed with a local oscillator signal. An output signal proportional to the difference in frequency between the return signal and the local oscillator signal is generated by the one or more photodetectors 514.

[0054] In one variant, the inputted optical signal is directed into the pixel though a coupler 522 and then split (e.g., by a splitter 525) into two portions. A first portion is directed towards a coupler 520, then towards one or more grating couplers 521, and then further towards the target (e.g., the target object). A second portion is directed towards a polarization rotator 527, then a coupler 523, and then one or more photodetectors 524. The return signal reflected from the target is coupled back into the pixel through one or more grating couplers 521 and directed towards the coupler 520, then towards anothercoupler 523, and then further towards one or more photodetectors 524, where the return signal is mixed with a local oscillator signal. An output signal proportional to the difference in frequency between the return signal and the local oscillator signal is generated by the one or more photodetectors 524.

[0055] In another variant, the inputted optical signal is directed into the pixel though a coupler 532 and then split (e.g., by a splitter 535) into two portions. A first portion is directed towards a circulator 530, then towards a grating coupler 531, and then further towards the target (e.g., the target object). A second portion is directed towards a coupler 533 and then towards one or more photodetectors 534. The return signal reflected from the target is coupled back into the pixel through the grating coupler 531 and directed towards the circulator 530, then towards the coupler 533, and then further towards one or more photodetectors 534, where the return signal is mixed with a local oscillator signal. An output signal proportional to the difference in frequency between the return signal and the local oscillator signal is generated by the one or more photodetectors 534.

[0056] In some example embodiments, one or more of the photodetectors 514, 524, and 534 have associated corresponding TIAs located in their proximity. In alternative example embodiments, one or more of the TIAs may be located in elsewhere (e.g., a different location).

[0057] FIG. 9 is a diagram illustrating a row of pixels in which pairs of adjacent pixels share photodiodes and associated TIAs, according to some example embodiments. In the example embodiments shown in FIG. 9, one or more pixels are polarization multiplexing pixels. In one mode (e.g., one switch position) of an external optical switch (e.g., switch 303) that provides light (e.g., one or more optical signals) to the row, light is provided to the lower optical bus 501, through the optical coupler 503 (e.g., an optical tap coupler) on the lower optical bus, and then to one or more odd pixels. Light travels towards the coupler 510 (e.g., a first multiplexer coupler) that splits the light into two portions to be outcoupled by one or more grating couplers 511 and sent towards the target (e.g., the target object). Light returning from the target is coupled back into therow of pixels by the same one or more grating couplers 511 and sent towards the coupler 513 (e.g., a second multiplexing coupler) which mixes it with local oscillator signal that has been previously tapped from the lower optical bus 501. The mixed signals are directed from the output of the coupler 513 to the first input of one or more photodetectors 514 (e.g., photodiodes).

[0058] Similarly (e.g., symmetrically), in another mode (e.g., another switch position) of the external optical switch (e.g., switch 303), light is provided to the upper optical bus 501, through the optical coupler 503 (e.g., an optical tap coupler) on the upper optical bus, and then to one or more even pixels. Light travels towards the coupler 510 (e.g., a first multiplexer coupler) that splits the light into two portions to be outcoupled by one or more grating couplers 511 and sent towards the target (e.g., the target object). Light returning from the target is coupled back into the row of pixels by the same one or more grating couplers 511 and sent towards the coupler 513 (e.g., a second multiplexing coupler) which mixes it with local oscillator signal that has been previously tapped from the upper optical bus 501. The mixed signals are directed from the output of the coupler 513 to the second input of one or more photodetectors 514 (e.g., photodiodes).

[0059] FIG. 10 is a diagram illustrating a top half of a sensor with a coherent focal plane array of pixels (e.g., coherent focal plane array 203), with optical switches positioned outside the coherent focal plane array, according to some example embodiments. In the example embodiments shown in FIG. 10, the optical switching block 202 (e.g., an out-of-array optical switching block) is composed of a plurality p of parallel channels followed by a plurality of cascaded switching layers 601 (e.g., configured as an optical switch). Optical signals provided as outputs of the optical switching block 202 are routed directly into one or more array blocks 602 of pixels within the coherent focal plane array 203 of pixels.

[0060] FIG. 11 is a diagram illustrating a top half of a sensor with a coherent focal plane array of pixels (e.g., coherent focal plane array 203), with optical switches both outside the coherent focal plane array and embedded inside the coherent focal planearray, according to some example embodiments. In the example embodiments shown in FIG. 11, the optical switching block 202 is split into two with a plurality of switching layers 601 (e.g., each configured as an optical switch) residing outside the coherent focal plane array 203 of pixels, while another plurality of switching layers 603 (e.g., each configured as an optical switch) resides inside the coherent focal plane array 203 of pixels.

[0061] FIG. 12 is a diagram illustrating a quadrant of a sensor with a coherent focal plane array of pixels (e.g., coherent focal plane array 203), with optical switches both outside the coherent focal plane array and embedded inside the coherent focal plane array, according to some example embodiments. In the example embodiments shown in FIG. 12, a half of an optical switching block (e.g., a left half of the optical switching block 202 includes a plurality of switching layers 601 (e.g., each configured as an optical switch) residing outside the coherent focal plane array 203 of pixels. Accordingly, FIG. 12 illustrate a portion (e.g., a left half) of the half sensor shown in FIG. 12.

[0062] FIG. 13 is a diagram illustrating a 1x8 optical switch 702 positioned at the top of the pixel block and compatible with delivery of high optical power into each line of pixels in the pixel block, according to some example embodiments. In the example embodiments shown in FIG. 13, switches are embedded inside the pixel array and are positioned at the top and along a two-dimensional block array of pixels. Each output of the 1x8 optical switch 702 may be connected to a corresponding Ixq pixel line. In some example embodiments, a frequency modulated optical signal, provided by a switch positioned outside the pixel array or directly from the source of the frequency modulated optical signal, is directed through an input 701 (e.g., an input waveguide) to the input of the 1x8 optical switch 702. The frequency modulated optical signal is then directed by the 1x8 optical switch 702 to one of a plurality of optical outputs 703 (e.g., output waveguides) and further into a corresponding Ixq linear pixel line 704. In various example embodiments, a Ixn switch may be used to direct light to n rows of q pixels.

[0063] FIG. 14 is a diagram illustrating a monostatic system 800 with a coherent focal plane array of pixels (e.g., coherent focal plane array 203), according to someexample embodiments. In the example embodiments shown in FIG. 14, a photonic integrated circuit 801 includes a coherent focal plane array of pixels and may use a monostatic architecture for one or more pixels (e.g., for each pixel). In a monostatic architecture, outbound optical signals from the photonic integrated circuit 801 travel towards a diffractive or refractive optical element 802 (e.g., a lens) and then further towards a target 805 (e.g., a target object). A reflected return signal from the target 805 is passed through the diffractive or refractive optical element 802 and then coupled back into the photonic integrated circuit 801, where one or more characteristics of the reflected return signal are measured (e.g., by one or more photodetectors in the photonic integrated circuit 801).

[0064] FIG. 15 is a diagram illustrating a bistatic system 900 with a coherent focal plane array of pixels (e.g., coherent focal plane array 203), according to some example embodiments. In the example embodiments shown in FIG. 15, a transmit photonic integrated circuit 901 and a receive photonic integrated circuit 904 are separate.Outbound optical signals from the transmit photonic integrated circuit 901 travel towards a diffractive or refractive optical element 902 (e.g., a lens) and then further towards a target 905 (e.g., a target object). A reflected return signal from the target 905 is passed through a refractive or diffractive optical element 903 (e.g., a lens) and then coupled back into the receive photonic integrated circuit 904 (e.g., through a corresponding optical coupler).

[0065] In some example embodiments, the receive photonic integrated circuit 904 includes a coherent focal plane array of pixels (e.g., coherent focal plane array 203, which may be configured to transform a received optical signal into an electrical signal and further transmit the electrical signal to a signal processor, for measuring one or more characteristics of the target (e.g., distance to the target, reflectivity of the target, other characteristics, or any suitable combination thereof).

[0066] In some example embodiments, the transmitter and receiver parts of the bistatic system are physically separated. In certain example embodiments, a data signal may be encoded into the outbound optical signals by the transmit photonic integratedcircuit 901 and ultimately received by the receive photonic integrated circuit 904 situated at a considerable physical distance away from the transmit photonic integrated circuit 901. In certain example embodiments, the transmit photonic integrated circuit 901 uses a switching architecture (e.g., as described above with respect to FIGS. 5, 10, 11, or 12) to transmit high power to an outcoupler (e.g., an output coupler or other coupler suitable for outbound optical signals) and into free space. Accordingly, such a switched transmit / receive architecture (e.g., a switched transmit / receive configuration) may be used for long-range free space communication.

[0067] In various example embodiments, some or all of the photodiodes in the receiver part are shared between adjacent pixels, and transmission of optical signals by the coherent focal plane array in the transmitter part is synchronized with activation of the pixels in the receiver part or with the local oscillator and readout. In some example embodiments, odd pixels are illuminated on the transmitter part, and the corresponding odd pixels on the receiver part are activated and read in one cycle. In the following cycle, even pixels are illuminated on the transmitter part, and the corresponding even pixels on the receiver part are activated and read.

[0068] Although FIG. 15 illustrates a side-by-side configuration for the bistatic system 900, other example embodiments of the bistatic system 900 may use a polarization beam splitter to combine the transmitter and receiver paths and obtain complete overlap of the outbound and inbound optical paths.

[0069] FIG. 16 is a diagram illustrating a two-dimensional block 1000 of pixels with pairs of pixels sharing pairs of photodiodes, according to some example embodiments. In the example embodiments shown in FIG. 16, an optical signal inputted into the block 1000 of pixels is toggled between two sets of optical buses 1001, 1002 with a first set of pixels 1010 being supplied with the frequency modulated laser signal by one set optical buses 1001 and a second set of pixels 1011 are supplied with the frequency modulated laser signal by the other set of optical buses 1002.

[0070] The two optical buses 1001, 1002 may be connected (e.g., upstream, by an optical switch 303) and may receive light from two different outputs of a shared opticalswitch (e.g., optical switch 303). In one mode (e.g., one switch position) of the switch 303, the first set of optical buses 1001 is provided with light (e.g., one or more optical signals) and in turn provides light to the first set of pixels 1010. In another mode (e.g., another switch position) of the switch 303, the second set of optical buses 1002 is provided with light and in turn provides light to the second set of pixels 1011.

[0071] Just as in previous embodiments, pairs of pixels 1010, 1011 from the first and second set share photodiodes 1020. One terminal (i.e., input) of a photodiode 1020 is connected to a pixel 1010 of the first set while the other terminal (i.e., input) of a photodiode 1020 is connected to a pixel 1011 of the second set. Since the first set of pixels 1010 and the second set of pixels 1011 are connected to separate sets of optical buses 1001, 1002, which are not simultaneously provided with light (e.g., optical signals), or are otherwise configured to be mutually exclusive, the photodiodes 1020 will read, detect, receive, or otherwise process return signals for first pixels 1010 when their corresponding optical set of optical buses 1001 is provided with light, and the photodiodes 1020 will read, detect, receive, or otherwise process return signals from the second set of pixels 1011 when their corresponding second set of optical buses 1002 is provided with light.

[0072] In the embodiments of the type shown in FIG. 16, again, a first set of optical pixels 1010 is interleaved among a second set of optical pixels 1011 and vice versa. However, in contrast to the previous examples, where the first and second sets of optical pixels are alternatingly interleaved, i.e., where (except for the borders of the block) each pixel of the first set has two neighboring pixels of the second set and vice versa, in the embodiment of Fig. 16, each pixel of the first set has (except for the borders of the block 1000) one neighboring pixel of the first set and one neighboring pixel of the second set, and vice versa.

[0073] FIG. 17 is a diagram illustrating another two-dimensional block 1000 of pixels with pairs of pixels sharing pairs of photodiodes, according to some example embodiments. It illustrates that there may be more than two sets of optical buses and more than two sets of optical pixels. In the example embodiments shown in FIG. 17, anoptical signal inputted into the block 1000 of pixels is toggled between three or more sets of optical buses 1001, 1002, 1003 with a first set of pixels 1010 being supplied with light (e.g., one or more optical signals, such as laser light signals) by the first set optical buses1001, a second set of pixels 1011 are supplied with light by the second set of optical buses 1002, and a third set of pixels 1012 are supplied with light by the third set of optical buses 1003 (etc. if there are more than three sets),

[0074] The first, second, and third sets of pixels 1010, 1011, 1012 and buses 1001,1002, 1003 are alternatingly and in interleaved manner arranged in the block 1000.

[0075] The switch may in this case be configured to alternately toggle the frequency modulated laser signal between the first, second, and third optical buses 1001, 1002, 1003.

[0076] FIGs. 18 and 19 illustrate an example of embodiments of a shared photodetector 1100. The shown example is a silicon-germanium photodiode. Such photodiodes comprise a p-n-junction 1101 formed by n- and p-doped regions 1102, 1103 of silicon. A germanium absorber 1104 with a bandgap matched to absorb light of the frequency modulated laser signal is connected to one or both of the doped regions 1102,1103. A lightguide 1105 extends along absorber 1104. To simplify design, lightguide 1105 may be of silicon.

[0077] Light traveling along lightguide 1105 is evanescently coupled into absorber1104, where it is absorbed and generates electron-hole pairs and therefore a current through p-n-junction 1101.

[0078] Examples of silicon-germanium photodiodes are, e.g., described in S. Lischke et al., "Ultra-fast germanium photodiode with 3-dB bandwidth of 265 GHz", Nature Photonics, Vol. 15 (2021), 925 - 931 (https: / / doi.org / 10.1038 / s41566-021-00893- w) or B. Wang et al., "High-speed Si-Ge avalanche photodiodes", PhotoniX (2022) 3:8, (https: / / photonix. springeropen, com / arti cl es / 10.1186 / s43074-022-00052-6).

[0079] In contrast to conventional designs of such photodiodes, though, the lightguide 1105 is to carry light to the photodiode from both its sides 1106a, 1106b, thereby providing separate input ports for both optical pixels connected to it.

[0080] In other words, the sides 1106a, 1106b form first and second inputs of the photodiode.

[0081] The light is absorbed as it travels along the p-n-j unction, thereby preventing an undesired coupling between the two optical pixels. In the example of FIGs. 18, 19, most of the light is absorbed by the germanium absorber 1104.

[0082] Using a germanium absorber allows detecting light of long wavelengths. Alternatively, if shorter wavelengths are used, doped silicon may be used as an absorber and SiO2 or SiN may be used for light guide 1105.

[0083] Hence, the photodetector 1100 connected to a first optical pixel of the first set of optical pixels and to a second optical pixel of the second set of optical pixels may comprise a p-n-j unction 1101 and a waveguide 1105 extending along the p-n-j unction 1101. The first optical pixel is connected to feed light from first side 1106a into the waveguide 1105 while the second optical pixel is connected to feed light from the second side 1006b into the waveguide 1105.

[0084] The photodetector 1100 may further comprise a germanium absorber 1104 extending along the waveguide 1105 to absorb light traveling in the waveguide 1105. The germanium absorber 1104 is electrically connected to the p-n-j unction 1101.

[0085] A coherent focal plane array sensor may, in some embodiments, be defined as a sensor having a focal plane array of optical pixels and being adapted to send out a frequency-modulated laser signal to a target, to receive returning light, and to measure the frequency shift between the present laser signal (i.e., the local oscillator signal) and the returning light by means of coherent interference. This frequency shift is a measure of the distance to the target.

[0086] The optical pixels may be adapted to generate an interference signal between the local oscillator signal and the returning light.

[0087] The frequency-modulated laser source may be adapted to generate a laser signal having varying optical frequency, i.e., varying optical wavelength. For good spatial resolution, the frequency is swept continuously. In this context, "continuously" includes quasi-continuous sweeping in at least 100, or even at least 1000, steps.

[0088] Throughout this specification, plural instances may implement components, operations, or structures described as a single instance. Although individual operations of one or more methods are illustrated and described as separate operations, one or more of the individual operations may be performed concurrently, and nothing requires that the operations be performed in the order illustrated. Structures and their functionality presented as separate components and functions in example configurations may be implemented as a combined structure or component with combined functions. Similarly, structures and functionality presented as a single component may be implemented as separate components and functions. These and other variations, modifications, additions, and improvements fall within the scope of the subject matter herein.

[0089] Some portions of the subject matter discussed herein may be presented in terms of algorithms or symbolic representations of operations on data stored as bits or binary digital signals within a memory (e.g., a computer memory or other machine memory). Such algorithms or symbolic representations are examples of techniques used by those of ordinary skill in the data processing arts to convey the substance of their work to others skilled in the art. As used herein, an “algorithm” is a self-consistent sequence of operations or similar processing leading to a desired result. In this context, algorithms and operations involve physical manipulation of physical quantities.Typically, but not necessarily, such quantities may take the form of electrical, magnetic, or optical signals capable of being stored, accessed, transferred, combined, compared, or otherwise manipulated by a machine. It is convenient at times, principally for reasons of common usage, to refer to such signals using words such as “data,” “content,” “bits,” “values,” “elements,” “symbols,” “characters,” “terms,” “numbers,” “numerals,” or the like. These words, however, are merely convenient labels and are to be associated with appropriate physical quantities.

[0090] Unless specifically stated otherwise, discussions herein using words such as “accessing,” “processing,” “detecting,” “computing,” “calculating,” “determining,” “generating,” “presenting,” “displaying,” or the like refer to actions or processes performable by a machine (e.g., a computer) that manipulates or transforms data represented as physical (e.g., electronic, magnetic, or optical) quantities within one or more memories (e.g., volatile memory, non-volatile memory, or any suitable combination thereof), registers, or other machine components that receive, store, transmit, or display information. Furthermore, unless specifically stated otherwise, the terms “a” or “an” are herein used, as is common in patent documents, to include one or more than one instance. Finally, as used herein, the conjunction “or” refers to a nonexclusive “or,” unless specifically stated otherwise.

[0091] The following enumerated descriptions describe various examples of methods, machine-readable media, and systems (e.g., machines, devices, or other apparatus) discussed herein. Any one or more features of an example, taken in isolation or combination, should be considered as being within the disclosure of this application.

[0092] In the following some examples are summarized.

[0093] A first example provides a light detection and ranging (LIDAR) sensor system comprising: a laser source configured to generate a frequency modulated laser signal; and a coherent focal plane array sensor comprising: a photonic integrated circuit comprising an optical switch configured to alternately toggle the frequency modulated laser signal between a first optical bus and a second optical bus, the first optical bus supplying the frequency modulated laser signal to a first set of optical pixels interleaved among a second set of optical pixels, the second optical bus supplying the frequency modulated laser signal to the second set of optical pixels interleaved among the first set of optical pixels.

[0094] In the first example, a first optical pixel among the first set of optical pixels and a second optical pixel among the second set of optical pixels may be both optically coupled to a same shared photodetector.

[0095] In the first example, the photonic integrated circuit further may further comprise a photodetector with a first side and a second side, the first side of the photodetector being optically coupled to a first optical pixel among the first set of optical pixels supplied by (i.e., fed with light by) the first optical bus, the second side of the photodetector being optically coupled to a second optical pixel among the second set of optical pixels supplied (i.e., fed with light by) by the second optical bus.

[0096] In the first example, the photonic integrated circuit further comprises a photodetector with a first input and a second input, the first input of the photodetector being optically coupled to a first optical pixel among the first set of optical pixels supplied by the first optical bus, the second input of the photodetector being optically coupled to a second optical pixel among the second set of optical pixels supplied by the second optical bus.

[0097] In the first example, a first optical pixel among the first set of optical pixels supplied by the first optical bus may be located adjacent to a second optical pixel among the second set of optical pixels supplied by the second optical bus.

[0098] In the first example, the first set of optical pixels supplied by the first optical bus may comprise odd pixels in a row of pixels within a coherent focal plane array of pixels; and the second set of optical pixels supplied by the second optical bus may comprise even pixels in the row of pixels with the coherent focal plane array of pixels.

[0099] In the first example, the optical switch, in a first mode of operation, may supply the frequency modulated laser signal to the first optical bus and not to the second optical bus, the first optical bus suppling the frequency modulated laser signal to the first set of optical pixels and not to the second set of optical pixels; and the optical switch, in a second mode of operation, may supply the frequency modulated laser signal to the second optical bus and not to the first optical bus, the second optical bus suppling thefrequency modulated laser signal to the second set of optical pixels and not to the first set of optical pixels.

[0100] The first example may further comprise a LIDAR chip comprising a FMCW LIDAR transceiver implemented on a photonic integrated circuit, the photonic integrated circuit comprising: an optical switch configured to alternately toggle a frequency modulated laser signal between a first optical bus and a second optical bus, the first optical bus supplying the frequency modulated laser signal to a first set of optical pixels interleaved among a second set of optical pixels, the second optical bus supplying the frequency modulated laser signal to the second set of optical pixels interleaved among the first set of optical pixels.

[0101] In the first example, a first optical pixel among the first set of optical pixels and an optical pixel among the second set of optical pixels may be both optically coupled to a same shared photodetector.

[0102] In the first example, the first optical bus may supply the frequency modulated laser signal to a first set of optical couplers configured to supply the frequency modulated laser signal to the first set of optical pixels interleaved among the second set of optical pixels; and the second optical bus may supply the frequency modulated laser signal to a second set of optical couplers configured to supply the frequency modulated laser signal to the second set of optical pixels interleaved among the first set of optical pixels.

[0103] In the first example, the photonic integrated circuit may further comprise a photodetector with a first input and a second input, the first input of the photodetector being optically coupled to a first optical pixel among the first set of optical pixels supplied by the first optical bus, the second input of the photodetector being optically coupled to a second optical pixel among the second set of optical pixels supplied by the second optical bus.

[0104] Further, in the system, a first optical pixel among the first set of optical pixels supplied by the first optical bus may be located adjacent to a second optical pixel among the second set of optical pixels supplied by the second optical bus.

[0105] Further, in the system, the first set of optical pixels supplied by the first optical bus may comprise odd pixels in a row of pixels within a coherent focal plane array of pixels; and the second set of optical pixels supplied by the second optical bus may comprise even pixels in the row of pixels with the coherent focal plane array of pixels.Further, in the system, the optical switch, in a first mode of operation, may supply the frequency modulated laser signal to the first optical bus and not to the second optical bus, the first optical bus suppling the frequency modulated laser signal to the first set of optical pixels and not to the second set of optical pixels; and the optical switch, in a second mode of operation, may supply the frequency modulated laser signal to the second optical bus and not to the first optical bus, the second optical bus suppling the frequency modulated laser signal to the second set of optical pixels and not to the first set of optical pixels.

[0106] A second example provides a photonic integrated circuit comprising an optical switch configured to alternately toggle a frequency modulated laser signal between a first optical bus and a second optical bus, the first optical bus supplying the frequency modulated laser signal to a first set of optical pixels interleaved among a second set of optical pixels, the second optical bus supplying the frequency modulated laser signal to the second set of optical pixels interleaved among the first set of optical pixels.

[0107] In the second example, a first optical pixel among the first set of optical pixels and a second optical pixel among the second set of optical pixels may be both optically coupled to a same shared photodetector.

[0108] In the second example, the photonic integrated circuit may further comprise a photodetector with a first side and a second side, the first side of the photodetector being optically coupled to a first optical pixel among the first set of optical pixelssupplied by the first optical bus, the second side of the photodetector being optically coupled to a second optical pixel among the second set of optical pixels supplied by the second optical bus.

[0109] In the second example, the photonic integrated circuit further may comprise a photodetector with a first input and a second input, the first input of the photodetector being optically coupled to a first optical pixel among the first set of optical pixels supplied by the first optical bus, the second input of the photodetector being optically coupled to a second optical pixel among the second set of optical pixels supplied by the second optical bus.

[0110] In the second example, a first optical pixel among the first set of optical pixels supplied by the first optical bus may be located adjacent to a second optical pixel among the second set of optical pixels supplied by the second optical bus.

[0111] In the second example, the optical switch, in a first mode of operation, may supply the frequency modulated laser signal to the first optical bus and not to the second optical bus, the first optical bus suppling the frequency modulated laser signal to the first set of optical pixels and not to the second set of optical pixels; and the optical switch, in a second mode of operation; may supply the frequency modulated laser signal to the second optical bus and not to the first optical bus, the second optical bus suppling the frequency modulated laser signal to the second set of optical pixels and not to the first set of optical pixels.

[0112] In a third example, a method of operating a light detection and ranging (LIDAR) sensor may be provided, the method comprising: generating a frequency modulated laser signal; alternately toggling the frequency modulated laser signal between a first optical bus and a second optical bus, the first optical bus supplying the frequency modulated laser signal to a first set of optical pixels interleaved among a second set of optical pixels, the second optical bus supplying the frequency modulated laser signal to the second set of optical pixels interleaved among the first set of optical pixels; andperforming ranging of a target object based on the alternately toggled frequency modulated laser signal reflected back from a target object and received by the first and second sets of optical pixels.

[0113] In the third example, the first optical bus may supply the frequency modulated laser signal to a first set of optical couplers configured to supply the frequency modulated laser signal to the first set of optical pixels interleaved among the second set of optical pixels; and the second optical bus may supply the frequency modulated laser signal to a second set of optical couplers configured to supply the frequency modulated laser signal to the second set of optical pixels interleaved among the first set of optical pixels.

[0114] In the third example, a first optical pixel among the first set of optical pixels and a second optical pixel among the second set of optical pixels may be both optically coupled to a same shared photodetector.

[0115] In the third example, a first optical pixel among the first set of optical pixels supplied by the first optical bus may be located adjacent to a second optical pixel among the second set of optical pixels supplied by the second optical bus.

[0116] In the third example, the first set of optical pixels supplied by the first optical bus may comprise odd pixels in a row of pixels within a coherent focal plane array of pixels; and the second set of optical pixels supplied by the second optical bus may comprise even pixels in the row of pixels with the coherent focal plane array of pixels.

[0117] In examples where pixels of the first and of the second set of pixels are arranged alternatingly along a row and connected to first and second optical buses, respectively, the first and the second optical buses may extend along the row of pixels.

[0118] In examples having a photodetector connected to first and second optical pixels, for a particularly compact design, the photodetector may comprise a p-n-junction and a waveguide extending along the p-n-junction. The first optical pixel may beconnected to feed light from a first side into the waveguide and the second optical pixels may be connected to feed light from a second side into the waveguide.

[0119] The photodetector may further comprise a germanium absorber extending along the waveguide and being electrically connected to the p-n-j unction.

[0120] In all embodiments, for a compact, robust design, a pixel may be adapted for emission, reception, and coherent analysis of the reflected signal, such as shown in the examples of FIG. 8, comprise an arrangement of one or more couplers (couplers 511, 521, 531) adapted to couple out light from the photonic integrated circuit for emitting it towards a target and for receiving light reflected from the target and to couple it into the photonic integrated circuit. It may further comprise a mixer (such as the couplers 513, 523, 533 of FIG. 8) that generates an optical output signal, or, for better signal -to-noise ratio, a pair of complementary optical output signals, from the interference between the local oscillator signal from the light source and the returning light, with the output signal(s) of the mixer being fed to the photodetectors (514, 524, 534 of Fig. 8).

[0121] In some embodiments, there may be exactly two sets of buses and exactly two sets of optical pixels per block, which simplifies switching. In other embodiments, there may be more than two sets of buses and more than two sets of pixels per block, which allows to direct more light power to one set.

Claims

CLAIMS1. A light detection and ranging (LIDAR) sensor system comprising: a laser source configured to generate a frequency modulated laser signal; and a coherent focal plane array sensor comprising: a photonic integrated circuit comprising an optical switch configured to alternately toggle the frequency modulated laser signal between a first optical bus and a second optical bus, the first optical bus supplying the frequency modulated laser signal to a first set of optical pixels interleaved among a second set of optical pixels, the second optical bus supplying the frequency modulated laser signal to the second set of optical pixels interleaved among the first set of optical pixels.

2. The LIDAR sensor system of claim 1 , wherein: a first optical pixel among the first set of optical pixels and a second optical pixel among the second set of optical pixels are both optically coupled to a same shared photodetector.

3. The LIDAR sensor system of claim 1, wherein: the photonic integrated circuit further comprises a photodetector with a first side and a second side, the first side of the photodetector being optically coupled to a first optical pixel among the first set of optical pixels supplied by the first optical bus, the second side of the photodetector being optically coupled to a second optical pixel among the second set of optical pixels supplied by the second optical bus.

4. The LIDAR sensor system of claim 1 , wherein: the photonic integrated circuit further comprises a photodetector with a first input and a second input, the first input of the photodetector being optically coupled to a first optical pixel among the first set of optical pixelssupplied by the first optical bus, the second input of the photodetector being optically coupled to a second optical pixel among the second set of optical pixels supplied by the second optical bus.

5. The LIDAR sensor system of any of the claims 2 to 4, wherein the photodetector comprises a p-n-junction, a waveguide extending along the p-n-junction, wherein the first optical pixel is connected to feed light from a first side into the waveguide and the second optical pixels is connected to feed light from a second side into the waveguide.

6. The LIDAR sensor system of claim 5, wherein the photodetector further comprises a germanium absorber extending along the waveguide and being electrically connected to the p-n-junction.

7. The LIDAR sensor system of any of the preceding claims, wherein: a first optical pixel among the first set of optical pixels supplied by the first optical bus is located adjacent to a second optical pixel among the second set of optical pixels supplied by the second optical bus.

8. The LIDAR sensor system of any of the preceding claims, wherein: the first set of optical pixels supplied by the first optical bus comprises odd pixels in a row of pixels within a coherent focal plane array of pixels; and the second set of optical pixels supplied by the second optical bus comprises even pixels in the row of pixels with the coherent focal plane array of pixels.

9. The LIDAR sensor system of claim 8 wherein the first and the second optical buses extend along the row of pixels.

10. The LIDAR sensor system of any of the preceding claims, wherein: the optical switch, in a first mode of operation, supplies the frequency modulated laser signal to the first optical bus and not to the second optical bus, the first optical bus suppling the frequency modulated laser signal to the first set of optical pixels and not to the second set of optical pixels; and the optical switch, in a second mode of operation; supplies the frequency modulated laser signal to the second optical bus and not to the first optical bus, the second optical bus suppling the frequency modulated laser signal to the second set of optical pixels and not to the first set of optical pixels.

11. The LIDAR sensor system of any of the preceding claims wherein each optical pixel comprises an arrangement of one or more couplers adapted to couple out light from the photonic integrated circuit for emitting it towards a target and to receive returning light to couple it into the photonic integrated circuit, and a mixer adapted to generate at least one optical output signal from an interference between a local oscillator signal from the laser source and the returning light.

12. A frequency modulated continuous wave (FMCW) light detection and ranging (LIDAR) system comprising: a LIDAR chip comprising a FMCW LIDAR transceiver implemented on a photonic integrated circuit, the photonic integrated circuit comprising: an optical switch configured to alternately toggle a frequency modulated laser signal between a first optical bus and a second optical bus, the first optical bus supplying the frequency modulated laser signal to a first set of optical pixels interleaved among a second setof optical pixels, the second optical bus supplying the frequency modulated laser signal to the second set of coherent pixels interleaved among the first set of optical pixels.

13. The FMCW LIDAR system of claim 12, wherein: a first optical pixel among the first set of optical pixels and a second optical pixel among the second set of optical pixels are both optically coupled to a same shared photodetector.

14. The FMCW LIDAR system of claim 13, wherein: the photonic integrated circuit further comprises a photodetector with a first input and a second input, the first input of the photodetector being optically coupled to a first optical pixel among the first set of optical pixels supplied by the first optical bus, the second input of the photodetector being optically coupled to a second optical pixel among the second set of optical pixels supplied by the second optical bus.

15. The LIDAR sensor system of any of the claims 13 or 14, wherein the photodetector comprises a p-n-junction, a waveguide extending along the p-n-junction, wherein the first optical pixel is connected to feed light from a first side into the waveguide and the second optical pixels is connected to feed light from a second side into the waveguide.

16. The LIDAR sensor system of claim 15, wherein the photodetector further comprises a germanium absorber extending along the waveguide and being electrically connected to the p-n-j unction.

17. The FMCW LIDAR system of any of the claims 13 to 16, wherein: the first optical bus supplies the frequency modulated laser signal to a first set of optical couplers configured to supply the frequency modulated laser signal to the first set of optical pixels interleaved among the second set of optical pixels; and the second optical bus supplies the frequency modulated laser signal to a second set of optical couplers configured to supply the frequency modulated laser signal to the second set of optical pixels interleaved among the first set of optical pixels.

18. The FMCW LIDAR system of any of the claims 13 to 17, wherein: a first optical pixel among the first set of optical pixels supplied by the first optical bus is located adjacent to a second optical pixel among the second set of optical pixels supplied by the second optical bus.

19. The FMCW LIDAR system of any of the claims 13 to 18, wherein: the first set of optical pixels supplied by the first optical bus comprises odd pixels in a row of pixels within a coherent focal plane array of pixels; and the second set of optical pixels supplied by the second optical bus comprises even pixels in the row of pixels with the coherent focal plane array of pixels.

20. The FMCW LIDAR system of any of the claims 13 to 19, wherein: the optical switch, in a first mode of operation, supplies the frequency modulated laser signal to the first optical bus and not to the second optical bus, thefirst optical bus suppling the frequency modulated laser signal to the first set of optical pixels and not to the second set of optical pixels; and the optical switch, in a second mode of operation; supplies the frequency modulated laser signal to the second optical bus and not to the first optical bus, the second optical bus suppling the frequency modulated laser signal to the second set of optical pixels and not to the first set of optical pixels.

21. A photonic integrated circuit comprising: an optical switch configured to alternately toggle a frequency modulated laser signal between a first optical bus and a second optical bus, the first optical bus supplying the frequency modulated laser signal to a first set of optical pixels interleaved among a second set of optical pixels, the second optical bus supplying the frequency modulated laser signal to the second set of coherent pixels interleaved among the first set of optical pixels.

22. The photonic integrated circuit of claim 21, wherein: a first optical pixel among the first set of optical pixels and a second optical pixel among the second set of optical pixels are both optically coupled to a same shared photodetector.

23. The photonic integrated circuit of claim 21, wherein: the photonic integrated circuit further comprises a photodetector with a first side and a second side, the first side of the photodetector being optically coupled to a first optical pixel among the first set of optical pixels supplied by the first optical bus, the second side of the photodetector being optically coupled to a second optical pixel among the second set of optical pixels supplied by the second optical bus.

24. The photonic integrated circuit of claim 21, wherein: the photonic integrated circuit further comprises a photodetector with a first input and a second input, the first input of the photodetector being optically coupled to a first optical pixel among the first set of optical pixels supplied by the first optical bus, the second input of the photodetector being optically coupled to a second optical pixel among the second set of optical pixels supplied by the second optical bus.

25. The LIDAR sensor system of any of the claims 22 to 24, wherein the photodetector comprises a p-n-junction, a waveguide extending along the p-n-junction, wherein the first optical pixel is connected to feed light from a first side into the waveguide and the second optical pixels is connected to feed light from a second side into the waveguide.

26. The LIDAR sensor system of claim 25, wherein the photodetector further comprises a germanium absorber extending along the waveguide and being electrically connected to the p-n-junction.

27. The photonic integrated circuit of any of the claims 21 to 26, wherein: a first optical pixel among the first set of optical pixels supplied by the first optical bus is located adjacent to a second optical pixel among the second set of optical pixels supplied by the second optical bus.

28. The photonic integrated circuit of any of the claims 21 to 27, wherein: the optical switch, in a first mode of operation, supplies the frequency modulated laser signal to the first optical bus and not to the second optical bus, the first optical bus suppling the frequency modulated laser signal to the first set of optical pixels and not to the second set of optical pixels; andthe optical switch, in a second mode of operation; supplies the frequency modulated laser signal to the second optical bus and not to the first optical bus, the second optical bus suppling the frequency modulated laser signal to the second set of optical pixels and not to the first set of optical pixels.

29. A method of operating a light detection and ranging (LIDAR) sensor, the method comprising: generating a frequency modulated laser signal; alternately toggling the frequency modulated laser signal between a first optical bus and a second optical bus, the first optical bus supplying the frequency modulated laser signal to a first set of optical pixels interleaved among a second set of optical pixels, the second optical bus supplying the frequency modulated laser signal to the second set of coherent pixels interleaved among the first set of optical pixels; and performing ranging of a target object based on the alternately toggled frequency modulated laser signal reflected back from a target object and received by the first and second sets of optical pixels.

30. The method of claim 29, wherein: the first optical bus supplies the frequency modulated laser signal to a first set of optical couplers configured to supply the frequency modulated laser signal to the first set of optical pixels interleaved among the second set of optical pixels; and the second optical bus supplies the frequency modulated laser signal to a second set of optical couplers configured to supply the frequency modulated laser signal to the second set of optical pixels interleaved among the first set of optical pixels.

31. The method of any of the claims 29 or 30, wherein: a first optical pixel among the first set of optical pixels and a second optical pixel among the second set of optical pixels are both optically coupled to a same shared photodetector.

32. The method of any of the claims 29 to 31, wherein: a first optical pixel among the first set of optical pixels supplied by the first optical bus is located adjacent to a second optical pixel among the second set of optical pixels supplied by the second optical bus.

33. The method of any of the claims 29 to 32, wherein: the first set of optical pixels supplied by the first optical bus comprises odd pixels in a row of pixels within a coherent focal plane array of pixels; and the second set of optical pixels supplied by the second optical bus comprises even pixels in the row of pixels with the coherent focal plane array of pixels.

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