Photonic chip and photonic assembly integrating the chip

Abstract

The invention relates to a photonic chip (10) comprising at least one photonic circuit (1) comprising at least one laser source (L) for supplying a first radiation, called local oscillator (LO), to an optical mixer (M) and for supplying an emission radiation (Re) to a coupling device (C), the local oscillator (LO) and the emission radiation (Re) having a predetermined polarization. The coupling device (C) is configured to propagate the emission radiation (Re) in free space in the form of an emission beam from a measurement surface (Sm) and to receive a return reflection beam at this measurement surface (Sm) and to direct the reflection beam towards the optical mixer (M) as a reflection radiation (Rr) having the predetermined polarization. The optical mixer (M) generates a measurement signal (V) by interference pulsing of the local oscillator (LO) and the reflection radiation (Rr). The invention also relates to an optical assembly comprising such a photonic chip.

Description

Technical Field

[0001] This invention relates to photonic chips and photonic components integrating the same. The photonic chips and photonic components are particularly suitable for free-space communication and LiDAR (light detection and ranging) or fiber optic telemetry. Background Technology

[0002] The document “20×20 Focal Plane Switch Array for Optical Beam Steering” by X. Zhang et al., presented at the 2020 Conference on Laser and Electro-Optics (CLEO), San Jose, CA, USA, 2020, describes a two-dimensional device for beam steering consisting of a 20×20 array of microelectromechanical (MEMS) optical switches integrated on a photonic chip made of silicon. These switches are connected to surface couplers, and optical radiation can be selectively propagated from a light source to a selected coupler by choosing the coupler based on its row and column rank. A collimating lens is associated with the integrated device in such a way that the surface couplers are arranged in the focal plane of the lens. Each surface coupler is configured to propagate optical radiation in free space in the form of an emitted beam oriented along a straight line extending from the surface coupler and passing through the center of the lens in the far field. Therefore, an integrated beam steering device that allows for faster steering, has lower power consumption, and a wide field of view is available compared to conventional mechanical solutions. For example, this device could form a component of a LiDAR system.

[0003] Based on the document "Coherent solid-state LiDAR with Siliconphotonic optical phased arrays" by Ch. Poulton et al., Opt. Lett. 42, 4091-4094 (2017), a frequency-modulated continuous-wave (FMCW) LiDAR using an integrated optical phased array to steer the emitted beam is proposed. The component includes a photonic integrated circuit formed on a silicon platform and having a first edge coupler for propagating the beam through the optical phased array in free space. It includes a second edge coupler for receiving the reflected beam on the body of a scene illuminated by the emitted beam.

[0004] Photonic components used in frequency-modulated continuous-wave LiDAR typically employ optical mixers to generate measurement signals through interference pulses between emitted and reflected radiation. The strength of the measurement signal depends on the polarization of these signals. To maximize this strength, the radiation needs to have the same polarization at the mixer's input; if the polarizations of the two radiations are orthogonal, the measurement signal is zero.

[0005] Patent application WO2019161388A1 and publication “Photonic Integrated Circuit-Based FMCWCoherent LiDAR”, JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL.36, NO.19, OCTOBER 1, 2018, propose other frequency-modulated continuous wave LiDAR architectures. As in the previous reference, these architectures also provide two couplers, one for transmitting and one for receiving, which reduces the compactness of the photonic circuitry.

[0006] Furthermore, these architectures implement at least one fiber optic circulator to distinguish between the forward path of the transmitted radiation and the return path of the reflected radiation. To maintain the polarization of the light fields of these radiations, the fiber must also maintain its polarization, which is costly. Finally, these architectures are not robust enough to changes in the polarization of the reflected radiation, which can be linked to the properties of the illuminated subject in the scene, or to the angle of incidence of the beam on that subject. Summary of the Invention

[0007] This invention proposes photonic chips and photonic components for transmitting and receiving light beams in a manner different from existing technologies, aiming to provide a highly integrated solution. In some embodiments, the chips and photonic components are able to illuminate a scene using light beams with two different polarizations while maintaining their compact characteristics.

[0008] Technical solution

[0009] To achieve this objective, the present invention proposes a photonic chip comprising at least one transmitter-receiver circuit, the at least one transmitter-receiver circuit including at least one laser source for providing a first radiation, referred to as a local oscillator, to an optical mixer and for providing emitted radiation to a coupling device, the local oscillator and the emitted radiation having a predetermined polarization. The coupling device is configured to propagate the emitted radiation in the form of an emitted beam from a measurement surface in free space, and to receive a reflected beam returning from the same measurement surface and guide the reflected beam toward the optical mixer as reflected radiation having the predetermined polarization. The optical mixer generates a measurement signal through interference pulses of the local oscillator and the reflected radiation.

[0010] Other advantageous non-limiting features of the invention, obtained individually or in any technically feasible combination:

[0011] -The laser source includes a frequency modulator or is associated with a frequency modulator;

[0012] - The photonic chip includes a power divider optically associated with the laser source, the power divider providing the local oscillator and the emitted radiation;

[0013] - The coupling device of the transceiver circuit includes a first waveguide and a second waveguide, and an edge coupler disposed between the first waveguide and the second waveguide, the edge coupler being optically connected to a polarization beam splitter and a polarization rotator;

[0014] - The coupling device of the transceiver circuit includes a first waveguide and a second waveguide, and a surface coupler with a polarization splitter grating disposed between the first waveguide and the second waveguide.

[0015] - The transceiver circuit includes a first measurement channel and a second measurement channel. The first measurement channel is used to propagate a first emitted beam with a first propagation polarization at the chip output section, and the second measurement channel is used to propagate a second emitted beam with a second propagation polarization orthogonal to the first propagation polarization.

[0016] - The first emitted beam propagates through a first coupling device, and the second emitted beam propagates through a second coupling device that is discrete from the first coupling device;

[0017] - The transceiver circuit includes a first switch and a second switch, the first switch being optically arranged between the laser source and the first coupling device and the second coupling device, and the second switch being optically arranged between the first coupling device, the second coupling device and the mixer;

[0018] -The transceiver circuit includes:

[0019] - A first switch, the first switch being used to selectively connect a first waveguide of the multiplexing coupling device to the laser source or the mixer (M);

[0020] - A second switch, the second switch being used to selectively connect the second waveguide of the multiplexing coupling device to the laser source or the mixer;

[0021] -The photonic chip includes multiple transceiver circuits;

[0022] -The transceiver circuit includes multiple coupling devices;

[0023] - The at least one laser source emits radiation having multiple wavelengths, and the transceiver circuit includes a wavelength demultiplexer for distributing the wavelengths of the radiation toward the coupling device optically connected to the output of the demultiplexer.

[0024] - The transceiver circuit includes a plurality of laser sources that respectively emit the plurality of wavelengths, and the transceiver circuit further includes a wavelength division multiplexer for generating radiation having the plurality of wavelengths;

[0025] - The output sections of the demultiplexer are respectively connected to power dividers, which respectively provide local oscillators to the mixer and respectively provide emission radiation to the coupling device (C);

[0026] -The transceiver circuit includes:

[0027] ○ A unidirectional transmitting bus optically connected to the laser source and a receiving bus optically connected to the mixer, wherein the plurality of coupling devices are optically arranged between the unidirectional transmitting bus and the receiving bus;

[0028] ○ A first plurality of transmission elements, the first plurality of transmission elements being arranged between the unidirectional transmitting bus and the plurality of coupling devices to selectively connect the unidirectional transmitting bus to predetermined coupling devices and allow the propagation of the emitted radiation;

[0029] ○ A second plurality of transmission elements, arranged between the plurality of coupling devices and the receiving bus, to selectively connect the predetermined coupling devices to the receiving bus and allow the propagation of the reflected radiation;

[0030] - The transmission element is a filter, each filter being associated with a coupling device, and the filters having the same transmission wavelength range as each other;

[0031] -The transmission element is a switch;

[0032] - The transceiver circuitry includes a bidirectional transmission bus optically arranged between the power divider and the mixer, the bidirectional transmission bus being selectively connected to the coupling device via an optical circulator switch;

[0033] The photonic chip also includes two switches for selectively propagating the emitted radiation in the bidirectional transmission bus either along a first propagation direction or along a second propagation direction opposite to the first propagation direction.

[0034] According to another aspect, the present invention proposes a photonic component comprising at least one photonic chip as described above and at least one Faraday rotator disposed on the measurement surface of the chip to intercept the emitted beam and the reflected beam.

[0035] The photonic component may include a lens for collimating the emitted beam and the reflected beam and / or a polarizer configured to allow the emitted beam and the reflected beam to travel in a single polarization. Attached Figure Description

[0036] Other features and advantages of the invention will become apparent from the following detailed description of the invention with reference to the accompanying drawings, wherein:

[0037] Figure 1a and Figure 1b Two views depicting a first embodiment of a photonic device according to the present invention are shown;

[0038] Figure 2a and Figure 2b Two views depicting a second embodiment of a photonic device according to the present invention are shown;

[0039] Figure 3 The architecture and working principle of the transceiver circuit of the photonic chip according to the present invention are illustrated;

[0040] Figure 4 A first exemplary embodiment of the coupling device is described;

[0041] Figure 5 Another exemplary embodiment of the coupling device is described;

[0042] Figures 6a to 6c Several variations of the improved version of the transceiver circuit are described;

[0043] Figure 7 A block diagram of a chip including multiple transceiver circuits is depicted;

[0044] Figures 8a to 8f Several configurations of transceiver circuits are described to implement wavelength division multiplexing or time division multiplexing to reduce the number of components in the circuit. Detailed Implementation

[0045] In this application, "photonic chip" refers to an integrated circuit based on semiconductor materials formed using standard microelectronics techniques. This chip can be formed from an assembly of individual semiconductor-based components (e.g., laser sources, photodetectors, waveguides, electrical or electronic processing circuits).

[0046] General description of photonic components

[0047] Reference Figure 1a , Figure 1b , Figure 2a and Figure 2b Two embodiments of the photonic component 100 according to the present invention are presented.

[0048] This component 100 includes a photonic chip 10 having a main surface 10a. The measurement surfaces Sm of a plurality of optical coupling devices C are flush with the main surface 10a. As will become apparent in the remainder of this specification, each coupling device C enables the propagation of electromagnetic radiation generated by the chip 10 in free space in the form of an emitted beam at its measurement surface Sm. This emitted beam is reflected by an illuminated subject of a scene arranged in the field of view of the component 100. The same measurement surface Sm of the photonic chip 10 enables the reception of the beam reflected back by the subject. The coupling device C associated with this measurement surface Sm injects and guides this beam in the form of electromagnetic radiation reflected in the photonic chip 10. "Same measurement surface" means that the emitted beam and the received beam are at least partially superimposed on the main surface 10a. A single coupling device C ensures the emission of the beam and the reception of the reflected beam at this surface. The complex fiber optic configuration of the component 100 is not required as in some architectures of the prior art presented in the description of this application.

[0049] Each coupling device C is part of the transceiver circuit 1 of the chip 10, which is described in detail later in this disclosure. The photonic chip 10, which is provided with at least one transceiver circuit 1, is capable of generating an emitted beam and processing a reflected beam to generate an electrical measurement signal V, which represents the distance separating the photonic component 100 from the reflecting body and / or the relative velocity between the component 100 and the body.

[0050] In addition to the photonic chip 10, the photonic assembly 100 also includes at least one collimating lens disposed on the main surface 10a of the photonic chip 10. The measurement surface Sm of the coupling device C is disposed in the focal plane of the lens L. These coupling devices C are designed such that, depending on their position on the main surface 10a, the emitted light beam from the measurement surface Sm travels along a straight line passing through the optical center of the lens L (in...). Figure 1b and Figure 2b (Depicted with dashed lines) Projected into the far field. It can provide, for example... Figure 1b and Figure 2b The single lens L is shown, but multiple lenses may be provided alternatively (e.g., lenses associated with each measurement surface Sm).

[0051] An optional optical component 20 is also arranged in the optical paths of the emitted and reflected beams. This optical component is positioned on the main surface 10a of the chip 10 and sandwiched between the photonic chip 10 and the lens L. Other arrangements of the optical component 20 are possible, as long as it remains in the optical paths of the emitted and reflected beams. The optical component can be integrated into the chip 10. To distinguish between emitted and reflected radiation in the transceiver circuit 1 of the chip 10, the optical component 20 includes a 45° polarization rotator (e.g., a Faraday rotator) such that, after the propagation of the emitted beam and the return of the reflected beam, the reflected radiation propagating from the main surface 10a of the photonic chip 10 has a polarization orthogonal to the emitted radiation. The polarization rotator is not necessary when the reflected beam naturally has a polarization orthogonal to the emitted beam (e.g., when such polarization rotation is performed during the reflection of the emitted beam on an illuminated subject in the scene).

[0052] In addition to the polarization rotator, the optical component 20 may also include a polarizer arranged downstream of the Faraday rotator along the propagation direction of the emitted beam. This polarizer is configured to allow the emitted and reflected beams to propagate with a single polarization (beam propagation polarization, modified by the Faraday rotator when a reflected beam is present). This particularly prevents parasitic components of the reflected beam with different propagation polarizations from coupling to the photonic chip 10 and propagating in the transceiver circuits 1 of the chip 10 (specifically, towards the laser source contained within these circuits). The use of such a polarizer is preferred when the power of the reflected radiation is greater than 1 / 100th of the power of the emitted radiation.

[0053] In operation, the photonic component 100 can be operated to generate an emitted light beam from a measurement surface Sm associated with a selected transceiver circuit 1, to propagate the beam along a selected direction. By processing the reflected radiation received at the same measurement surface Sm, an electrical signal V representing the distance and / or relative velocity of the subjects arranged along the selected direction can be generated. For this purpose, the photonic chip 10 may include or be electrically associated with control circuitry, thereby enabling selection or operation of one of the transceiver circuits 1 within the transceiver circuitry of the chip 10.

[0054] By continuously scanning or, in some cases, by simultaneously activating the coupling devices C of the photonic chip 10 oriented in multiple directions, relative distance / velocity information of the entire scene can be collected and processed, for example, to depict the entire scene in the form of a point cloud as is well known in itself.

[0055] exist Figure 1a (Front view) and Figure 1bIn the first embodiment (side view), the photonic component 100 is typically strip-shaped, that is, a cuboid with a relatively narrow face and a relatively wide face. The narrow face of the strip corresponds to the main surface 10a of the photonic chip 10. Here, the measurement surface Sm of the coupling device C is aligned in a row on the narrow face of the strip. Figure 1a and Figure 1b A photonic assembly 100 is depicted having five measurement surfaces Sm and thus being able to generate beams in five different directions; however, the photonic assembly 100 can more generally be provided with any number of measurement surfaces Sm (typically between one and 100). By way of illustration, each measurement surface Sm can have a size of about a few square micrometers or even one hundred to several hundred square micrometers, and two of these surfaces Sm can be separated by a distance typically between 3 micrometers and 500 micrometers.

[0056] exist Figure 1a and Figure 1b In the illustrative figures of the first embodiment, each measurement surface Sm of the coupling device is associated with a transceiver circuit 1. To fabricate such a circuit, conventional microelectronic processing steps are applied to a substrate whose main plane corresponds to the wide face of the strip and is therefore perpendicular to the main surface 10a carrying the measurement surface Sm. Each coupling device C may include an edge coupler EC, the end of which is flush with the main surface 10a, forming the measurement surface Sm. The term "edge coupler" refers to any device used to couple a light beam to a waveguide, wherein the waveguide is arranged in the plane of beam propagation. This type of coupler is also specified by the articulation of "in-plane coupler." It can, in particular, be a thermally adiabatic coupler.

[0057] exist Figure 2a and Figure 2b In a second embodiment, the measurement surface Sm of the coupling device C is arranged in a matrix on the relatively wide main surface 10a of the photonic chip 10. This main surface 10a corresponds to the main plane of the substrate on which the chip 10 is manufactured, and in this case, the coupling device C advantageously includes at least one grating coupler GC. "Surface coupler" refers to any device used to couple a light beam to a waveguide, wherein the guide is arranged outside the beam propagation plane and substantially perpendicular to it. This type of coupler is also specified in the art as an "off-plane coupler" or "vertical coupler." It can be, in particular, a surface coupler with a polarization splitter grating.

[0058] In this embodiment, the transceiver circuit 1 advantageously includes a plurality of coupling devices C aligned in a row on the main surface 10a of the chip 10. The chip 10 may include a plurality of transceiver circuits 1 arranged side by side to form a measurement surface Sm on the main surface 10a in a matrix arrangement. The matrix may have any size (e.g., including matrices from 2×2 to 100×100, squares, or rectangles) and may be arranged in rows and columns as shown, or according to any other arrangement (e.g., in the form of poles).

[0059] By way of illustration, each measurement surface Sm can be about a few square micrometers or even a hundred to several hundred square micrometers in size, and the two surfaces of these surfaces Sm can be separated by a distance that is typically between 3 micrometers and 500 micrometers.

[0060] Overall description of the transceiver circuit

[0061] Now refer to Figure 3 The overall working principle of the transceiver circuit 1, which can be integrated into the photonic chip 10 just presented, will now be presented.

[0062] The transceiver circuit 1 provides the transmission of a light beam and the reception of a reflected light beam from the photonic component 100. It implements frequency modulated continuous wave (FMCW) technology to generate a measurement signal V.

[0063] Transceiver circuit 1 includes a laser source L, or is connected to a laser source, which is optically associated with a power divider S. The power divider S provides a first radiation, called local oscillator LO, to a first input of optical mixer M. The power divider S also provides a second radiation, called emitted radiation Re, which is directed toward coupling device C. Note that the divider S does not form a basic element of circuit 1 and other arrangements can be provided, such that the local oscillator LO and emitted radiation Re can be provided, for example, via two separate and synchronized laser sources.

[0064] As already presented, the coupling device C is configured to project emitted radiation Re in the form of an emitted beam in free space onto the measurement surface Sm (e.g., the exposed surface of a surface coupler or edge coupler with a polarization splitter grating). The coupling device C is also configured to receive a reflected beam on the same measurement surface Sm. The coupling device C injects a reflected beam in the form of reflected radiation Rr into the photonic circuit 1, the reflected radiation Rr being directed toward the optical mixer M.

[0065] Therefore, the mixer M receives the local oscillator LO and the reflected radiation Rr (which have a single predetermined polarization p, such as...) Figure 3(symbolized in the image), which results in pulses being interferometrically applied to one or more photodetectors to generate an electrical measurement signal V. As is well known per se and reviewed in Ch. Poulton's document presented in the introductory section, the average frequency of this measurement signal represents the distance separating the photonic component 100 of integrated circuit 1 from the body of the reflected emission beam. The electrical measurement signal can also be processed to determine the relative velocity of the body. To allow this operation, the laser source L includes or is associated with a frequency modulator, for example, by modulating its ramp or triangular frequency. This modulation can be achieved by controlling the injection current of the source L or by using an optical phase modulator.

[0066] As already mentioned, transceiver circuit 1 is associated with a control circuit, which may or may not be integrated into chip 10, and in all cases provides electrical signals to transceiver circuit 1 (and in particular to the laser source L) to allow its operation. The control circuit can also be connected to transceiver circuit 1 to receive measurement signals (or multiple measurement signals) V and perform conversion processing operations, thereby enabling distance and / or velocity measurements to be established.

[0067] In all cases, transceiver circuit 1 is manufactured according to conventional photonics technology, for example, from a silicon-on-insulator substrate. Radiation propagating in the circuit (such as radiation emitted by a laser source L, emitted radiation Re, reflected radiation Rr, and local oscillator LO) is guided between various elements of circuit 1 via waveguides.

[0068] A key feature of the photonic chip 10 disclosed herein is that it utilizes a single measurement surface Sm of the coupling device C to emit an emitted beam and receive a reflected beam. This feature allows for the formation of a particularly compact chip 10 and photonic assembly 100, and the use of the same optical component 20 and / or a single collimating lens / lens block L to process the emitted and reflected beams.

[0069] As already mentioned, this characteristic may require proper isolation of the following in the coupling device C: firstly, the emitted radiation Re intended to be directed toward the measurement surface Sm, and secondly, the reflected radiation Rr directed toward the optical mixer M. Depending on the required level of isolation for the system, this isolation can be achieved in several ways.

[0070] Therefore, according to Figure 4In the first example depicted, the coupling device C implements an edge coupler EC and includes a polarization beamsplitter PBS that receives emitted radiation Re from a distributor S or a laser source L via a first waveguide Ga. The polarization beamsplitter PBS is first optically connected to the coupler EC and then optically connected to a polarization rotator PR. It is known that the polarization beamsplitter PBS splits the radiation incident upon it into two radiation beams with orthogonal polarization. The polarization rotator is connected to a second waveguide Gb to propagate reflected radiation toward a mixer M.

[0071] exist Figure 4 In this way, the polarizations TE and TM of the radiation propagating in the coupler C are symbolized. The emitted radiation Re in this paper has a predetermined polarization TE that matches one of the orthogonal sharding polarizations of the polarization beam splitter PBS. Therefore, the radiation is transmitted to the coupler EC with little or no attenuation.

[0072] At the output of chip 10, the emitted beam emitted in free space from the emitting surface Sm of coupler EC has a propagation polarization Pa (related to, but not necessarily the same as, a predetermined polarization TE), and undergoes a first rotation of 45° in polarization by first passing through the Faraday rotator 20a of optical component 20, to have a modified propagation polarization Pa+45. The reflected beam (which is assumed here to have the same polarization Pa+45 as the emitted beam after it has passed through optical component 20) undergoes a second rotation of 45° in polarization on its return path by passing through the Faraday rotator 20a of optical component 20 again, to adopt a polarization Pb that is therefore orthogonal to the propagation polarization before being projected onto the measurement surface. The reflected radiation Rr guided by coupler EC has a polarization TM that is orthogonal to the polarization TE of emitted radiation Re. Therefore, the reflected radiation Rr is guided toward the channel of polarization beam splitter PBS that is separated from the channel receiving emitted radiation Re. Then, the reflected radiation Rr is guided toward the polarization rotator PR, so that the reflected radiation Rr can be returned to its original predetermined polarization TE (that is, the polarization TE of the emitted radiation Re) by applying a 90° rotation. Thus, the reflected radiation Rr has the same polarization as the local oscillator LO, so that they can be significantly processed by the mixer M and a measurement V can be established.

[0073] It should be noted that Figure 4 The coupling device C can be used in a reverse configuration, in which the emitted radiation Re propagates via the second waveguide Gb on the second input of the coupling device C, and the reflected radiation propagates via the first waveguide Ga on the first input of the coupling device C. In this reverse configuration, the emitted beam has a [propagation direction] at the chip output. Figure 4 The "standard" configuration presented in the image has orthogonal propagation polarization Pb.

[0074] Figure 5A second example of the coupling device C is depicted, this time implementing a surface coupler GC. In the depicted example, the surface coupler GC is a coupler with a polarization splitter grating, enabling the coupling of the two components Pa, Pb of the electromagnetic field of a beam reflected in a free-space optical device to two types of radiation Re, Rr guided by two separate waveguides Ga, Gb. The guided radiation Re, Rr have the same polarization TE. In contrast, the coupler GC enables the combination of the two radiations Re, Rr propagating in the waveguides Ga, Gb of the photonic chip 10 into a free-space emitted beam with two perpendicular components. Figure 5 In the example case, only the emitted radiation Re propagates along the first waveguide Ga towards the coupler Gc; therefore, the emitted beam essentially has only one polarization component Pa. As for the reflected radiation, it propagates along the second waveguide Gb.

[0075] Of course, this coupling device can be about Figure 4 The reverse configuration described is used to achieve the same effect of changing the polarization of the emitted beam.

[0076] In this second example, the Faraday rotator 20a and polarizer 20b serve the same function as previously described.

[0077] As already noted, and when the coupling device C is an edge coupler EC or a surface coupler GC, if the reflected beam naturally has a polarization orthogonal to the emitted beam, then the optical component 20 does not need to include a Faraday rotator 20a, which may be caused by reflection from the illuminated target T of the scene.

[0078] As already noted, if the reflected beam may have parasitic polarization components (especially those orthogonal to the modified polarization Pa+45), a polarizer 20b, consistent with the modified polarization Pa+45, can be added downstream of the Faraday rotator 20a into the optical component 20 along the propagation direction of the emitted beam. This blocks the parasitic components at the input of the transceiver circuit 1 and thus prevents them from coupling to the laser source L. This maintains the appropriate stability of the source.

[0079] Multi-polarization transceiver circuit

[0080] Figure 6a Presented Figure 3 The block diagram depicts an improved version of the photonic circuit 1. In this version, two orthogonal polarizations are used to form the photonic circuit 1, which has two separate measurement channels based on the two orthogonal polarizations respectively.

[0081] The photonic circuit 1 in the figure includes, according to Figure 3The block diagram shows a laser source L, a power divider S, a first mixer M, and a first coupling device C optically connected to each other. The first mixer M and the first coupling device C form a first measurement channel for generating a first measurement signal V. The photonic circuit 1 also includes a second mixer M' and a second coupling device C', which are separate from the first coupling device C and optically linked together to form a second measurement channel for generating a second measurement signal V'.

[0082] The power divider S has two separate channels, allowing a first emitted radiation Re to be directed toward a first coupler C and a first local oscillator LO to be directed toward a first mixer M in the first channel via two separate waveguides. A second emitted radiation K' to be directed toward a second coupler C' and a second local oscillator LO' to be directed toward a second mixer M' in the second channel via two other separate waveguides. These radiations Re, Re', LO, and LO' all have the same first polarization TE.

[0083] At the output of the first coupling device C of chip 10, and similarly to that disclosed with respect to the foregoing figures, the propagation polarization Pa of the first emitted beam is rotated by 45° by the first Faraday rotator 20a. The polarization Pa+45 of the reflected beam is also rotated by 45° by the first Faraday rotator 20a, such that when it is projected onto the measurement surface Sm of chip 10, it has a modified propagation polarization Pb at the output of chip 10 that is orthogonal to the propagation polarization Pa of the emitted beam. This polarization component Pb is coupled to the chip through the first coupling device C and directed toward the first mixer M to reflect radiation Rr having the same first polarization TE as the first emitted radiation Re.

[0084] For the second coupling device C', it is configured to propagate a second emitted beam with a propagating polarization Pb orthogonal to the polarization Pa of the first emitted beam at the output of the chip 10. This polarization Pb is rotated by 45° by the second Faraday rotator 20a'. The polarization Pb+45 of the second reflected beam is rotated by 45° by the second Faraday rotator 20a', such that when it is projected onto the measurement surface Sm of the chip 10, it has a modified polarization Pa orthogonal to the propagating polarization Pb of the second emitted beam. This polarization component Pa is coupled to the chip 10 through the second coupling device C and guided toward the second mixer M' to reflect radiation Rr' having the same first polarization TE as the second emitted radiation Re'.

[0085] As can be seen, the transceiver circuit in Figure 6 can emit two transmit beams with orthogonal polarization, and define different measurement channels for each of these polarizations.

[0086] exist Figure 6bIn the depicted variant, the first emitted radiation Re and the second emitted radiation Re' are generated alternately (rather than simultaneously) over time via the first switch SW1, allowing light from the source L to be alternately directed to either the first coupling device C or the second coupling device C'. This implementation advantageously allows the use of only a single mixer M, which is synchronously connected to either the first coupling device C or the second coupling device C' via the second switch SW2, thereby enabling the selective directing of either the first reflected radiation Rr or the second reflected radiation Rr' toward this single mixer M. The order of the optical switches SW1 and SW2 can be controlled by the control circuitry of chip 10.

[0087] exist Figure 6c In the depicted variant, each measurement channel in the measurement channel shares not only the mixer M but also the coupling device. The transceiver circuit 1 actually has two measurement channels, but uses a single time-division multiplexing coupling device C”. A first switch SW1’ is arranged between the laser source L (via power divider S), the mixer M, and the first input of the coupling device C” associated with the first waveguide Ga. The first switch SW1’ allows the first input of the coupler (first waveguide Ga) to be optically connected to either the divider S or the mixer M. A second switch SW2’ is arranged between the power divider S, the mixer M, and the second input of the multiplexing coupling device C” associated with the second waveguide Gb. The second switch SW2’ allows the second input of the multiplexing coupling device C” (second waveguide Gb) to be optically connected to either the laser source L (via the divider S) or the mixer M.

[0088] By switching switches SW1' and SW2', a first configuration is adopted to enable the emission of a beam with a first polarization Pa. Figure 6c The bottom portion of the coupler can propagate the emitted radiation Re from the distributor S to the first input of the multiplexing coupler C”, and propagate the reflected radiation from the second input of the multiplexing coupler C” towards the mixer M. In this configuration, the coupler C” is configured to emit an emitted beam with a first polarization Pa.

[0089] By switching switches SW1' and SW2' to the second configuration ( Figure 6c The emitted radiation Re propagates from the distributor S to the second input of the multiplexing coupler C”, and the reflected radiation Rr propagates from the first input of the multiplexing coupler C” toward the mixer M. In this second configuration, the coupler C” is configured to emit an emitted beam having a second polarization Pb perpendicular to the first polarization Pa.

[0090] This variant advantageously allows two measurement channels to be formed with only a single mixer M and a single multiplexing coupling device C”, which enables a reduction in the size of the transceiver circuit 1 and thus the size of the chip 10 while providing chip 10 with polarization diversity interrogation. In this example, the order of the optical switches SW1' and SW2' can also be controlled by the control circuitry of the chip 10.

[0091] exist Figures 6a to 6c In the example, the coupling devices C, C', and C" can be similarly combined according to... Figure 4 The configuration of the edge coupler EC or according to Figure 5 The surface coupler GC is configured as follows. By observing these figures, it will be understood that, depending on whether the emitted radiation Re is presented on one input portion of the input portion of the coupler C via the first waveguide Ga or on another input portion of the input portion of the coupler C via the second waveguide Gb, the coupler will emit an emitted beam with a first polarization Pa or a second polarization Pb orthogonal to the first polarization Pa.

[0092] Photonic chip including multiple transceiver circuits

[0093] Figure 7 A block diagram of a chip 10 including multiple transceiver circuits 1 is shown. In order to... Figure 7 For readability, each transceiver circuit in the transceiver circuitry described here has a single measurement channel, but it is entirely conceivable to integrate circuit 1 with two measurement channels in chip 10, which can be configured according to the information just mentioned. Figures 6a to 6c The described contents are activated sequentially or simultaneously. The laser source L of each transceiver circuit in the transceiver circuitry of chip 10 can be selected such that all (or some) of the laser sources emit radiation with the same wavelength. Alternatively, however, the laser sources L emit radiation with different wavelengths or more precisely, wavelengths included in different ranges. This avoids or limits optical coupling that may occur between the two transceiver circuits 1. The transceiver circuit 1 includes a coupling device C configured (by means of a collimating lens L of the photonic assembly 100 that chip 10 is intended to form) to emit emission beams oriented in different directions, as already presented in the description of the photonic assembly 100. Since chip 10 includes multiple transceiver circuits 1, the chip provides multiple measurement signals V that can be used by control circuitry (not shown).

[0094] Figure 7 The chip 10 can also be used to form the "strip-shaped" photonic component 100 of the first embodiment or the "surface-mount" photonic component 100 of the second embodiment, as shown in the bottom portion of the figure.

[0095] Transceiver circuit for wavelength division multiplexing

[0096] Figure 8a A transceiver circuit 1 is depicted, which combines the previously described operating principles, but more specifically, is suitable for forming a "surface-mounted" photonic assembly, according to which the measuring surface Sm is arranged to occupy the plane, for example, in the form of a matrix.

[0097] according to Figure 8a The multiple transceiver circuits 1 depicted are arranged side-by-side in the photonic chip 10, such as... Figure 7 As shown at the bottom. Each transceiver circuit 1 includes, advantageously according to Figure 5 The arrangement consists of multiple coupling devices C, where the coupler GC is a surface type with a polarization splitter grating. Figure 8a The transceiver circuit 1 includes a laser source L whose operating frequency can be modulated over a wide frequency range, for example, via a frequency modulation block FM. The transceiver circuit 1 also includes a power divider S, which enables the generation of emitted radiation Re and local oscillator LO; and a mixer M, which enables the generation of a measurement signal V by interference pulses of local oscillator LO and reflected radiation Rr.

[0098] Transceiver circuit 1 also includes a unidirectional transmit bus BE, which is optically connected to the power divider S to distribute the transmitted radiation Re to the coupler C. Transceiver circuit 1 also includes a receive bus BR, which collects the reflected radiation Rr provided by the coupler C and directs the reflected radiation Rr toward the mixer M. The coupler C is arranged between the unidirectional transmit bus BE and the receive bus BR, and is connected via filters F1 and F2 respectively. Figure 8a ) or optical switches SW1, SW2 ( Figure 8d These filters or optical switches are connected to these buses. They are typically designated as "transmission elements".

[0099] Reference Figure 8a The described implementation, termed "wavelength division multiplexing," involves placing multiple transmit filters F1, each associated with a coupler device C, between the unidirectional transmit bus BE and the coupler device C. The transmit filters F1 allow the unidirectional transmit bus BE to be selectively connected to the coupler device C and permit the emitted radiation Re to propagate to the device C.

[0100] Similarly, multiple receiving filters F2, each associated with a coupler C, are arranged between the coupler C and the receiving bus BR. The receiving filters F2 allow the receiving bus BR to be selectively coupled to the coupler C, thereby allowing reflected radiation to propagate toward the mixer M.

[0101] Transmitting filter F1 and receiving filter F2 are bandpass filters, meaning that when radiation has a wavelength that is included within the transmission wavelength range specific to the filter, these filters can transmit the radiation between the filter input and the filter output. When radiation has a wavelength outside this range, the radiation is blocked and does not transmit between the filter input and output.

[0102] To allow the selective connection of a coupler C to both the unidirectional transmit bus BE and the receive bus BR, the transmit filter F1 and receive filter F2 associated with a single coupler C have the same transmission wavelength range. Conversely, the transmit filter F1 and receive filter F2 associated with different couplers C have different transmission wavelength ranges.

[0103] Preferably, the transmission wavelength range of the filter is distributed over a wide range of wavelengths of radiation emitted by the laser source L, and together cover the wide range without overlapping.

[0104] Depending on the wavelength of the emitted radiation Re, the radiation will propagate in one of the coupling devices C, with a transmit filter F1 for this coupling device having a transmission wavelength range covering the wavelength of the emitted radiation Re. A receive filter F2 associated with this coupling device C has the same transmission wavelength range as the transmit filter F1, and the reflected radiation Rr has a wavelength substantially the same as the emitted radiation Re. This reflected radiation Rr will be transmitted by the receive filter F2 to the mixer M via the receive bus BR.

[0105] Therefore, by selecting the wavelength of the emitted radiation Re, the coupling device C that will be activated to emit the emitted beam can be selected from all the coupling devices C in the transceiver circuit 1.

[0106] The wavelength of the emitted radiation Re can be selected in different ways. According to a first method, a master filter can be provided in the frequency modulation block FM. The master filter FM is then configured, for example by a control device, to filter the radiation emitted by the FM block such that the emitted light radiation Re has a wavelength extending within a range that matches (or is narrower than) the transmission wavelength range of one of the filters F1 and F3. By configuring the master filter FM, the coupler C that will be activated to propagate the emitted beam is selected from all the couplers C of the transceiver circuit 1.

[0107] Figure 8bA first variant of circuit 1 that also implements wavelength division multiplexing is depicted. This first variant includes a frequency modulation block FM that generates radiation R(R(l1), R(l2), R(ln)) with multiple wavelengths and a laser source L. This radiation is injected into the input section De of a wavelength demultiplexer D having multiple output sections Ds(l1), Ds(l2), Ds(ln) to provide radiation R(l1), R(l2), R(ln) with specific wavelengths l1, l2, and ln, respectively.

[0108] Each output Ds of the demultiplexer D is optically linked to a power divider S that provides local oscillators LO(l1), LO(l2), LO(ln) and emitted radiation Re(l1), Re(l2), Re(ln). The wavelengths of the local oscillators LO and emitted radiation Re from the same divider S are, of course, the same. Each emitted radiation Re is directed toward the first input of the coupling device C, and the reflected radiation Rr from the device C is directed toward a mixer M dedicated to that coupling device C. The mixer M also receives the local oscillator from the power divider S to provide the measurement signal V.

[0109] Therefore, in this example, the demultiplexer D distributes wavelength components of radiation R with multiple wavelengths toward the coupling device C.

[0110] Figure 8c Another variation of transceiver circuit 1 that also implements wavelength division multiplexing is depicted. This second variation includes a power divider S, a coupling device C, and a mixer M, which can be combined to process radiation with specific wavelengths l1, l2, and lm from the outputs Ds(l1), Ds(l2), and Ds(ln) of the wavelength division multiplexer.

[0111] In this variant, the demultiplexer is a multiplexer-demultiplexer DM having multiple multiplexed inputs Me1, Me2, Men, each multiplexed input connected to a laser source L1, L2, Ln that continuously emits radiation with specific wavelengths l1, l2, ln. The demultiplexer has a multiplexed output Ms, from which continuous wave radiation is obtained by combining the continuous wave radiation presented on the multiplexed inputs Me1, Me2, Men. This radiation is directed toward a modulation block FM, which itself directs the generated radiation R(l1), R(l2), R(ln) to the demultiplexed input De of the multiplexer-demultiplexer DM.

[0112] In this example, transceiver circuit 1 includes multiple laser sources L1, L2, Ln that emit according to multiple different wavelengths l1, l2, ln. Transceiver circuit 1 also includes a multiplexer, which is combined here with a radiation distribution demultiplexer R to generate radiation R with multiple wavelengths.

[0113] Transceiver circuit for time-division multiplexing

[0114] Figure 8d Depicting having with Figure 8a The example architecture is similar to that of transceiver circuit 1, which is a so-called "time division multiplexing" implementation. Figure 8a In the example, filters F1 and F2 that connect coupler C to buses BE and BR are replaced here by switches SW1 and SW2. Switches SW1 and SW2 associated with coupler C can be commanded to close for a predetermined time period (e.g., via the controller of chip 10) to selectively connect coupler C to buses BE and BR during this time period. And during this time period, switches SW1 and SW2 associated with other couplers C can be commanded to open to disconnect these other couplers from buses BE and BR. By appropriately controlling the timing of switches SW1 and SW2 in transceiver circuit 1, coupler C can be continuously activated to emit a transmitted beam, receive a reflected beam, and generate a measurement signal V by means of mixer M. For this purpose, switch SW2 connecting coupler C to the receiving bus BR can remain closed for a duration sufficient to allow the emitted and reflected beams to propagate to the target and be received on the measurement surface of chip 10.

[0115] Figure 8e Depicting Figure 8d This is a highly advantageous variant of the time-division multiplexing implementation described herein. In this variant, a single bidirectional transmission bus BT distributes the emitted radiation Re from the power divider S to multiple coupling devices C. The same bidirectional transmission bus BT collects reflected radiation Rr from multiple of these coupling devices. An optical circulator switch SW allows each coupling device of circuit 1 to be selectively associated with the bidirectional transmission bus BT. As in the previous example, only one switch in the switch SW closes over time on each coupling device, thereby effectively time-division multiplexing the use of the coupling devices. Furthermore, the optical circulator switch SW in this example allows the emitted radiation Re to be directed from the bidirectional transmission bus to the input of the coupling device, and the reflected radiation Rr to be directed from another input of the coupling device to the bidirectional transmission bus BT, allowing it to continue its propagation.

[0116] The end of the bidirectional transmission bus opposite to the end that injects transmitted radiation Re through the frequency modulation block FM is optically connected to the mixer M to generate a measurement signal V, as in the aforementioned example of transceiver circuit 1.

[0117] Figure 8f Will Figure 8d The architecture of time-division multiplexing transceiver circuits and Figure 6cThe architecture is combined to share specific components of the circuit to provide two measurement channels to transceiver circuit 1 according to different polarizations. The figure shows the bidirectional transmission bus BT, laser source L, frequency modulation block FM, power divider M, and the module formed by coupler C and optical circulator switch SW, which are arranged in accordance with... Figure 8d The configuration is the same as the previous one. Switches SW1 and SW2 are also provided, which allow emitted radiation (and received radiation) to propagate in opposite directions depending on their configuration.

[0118] By switching switches SW1 and SW2, a first configuration can be used to emit a beam with a first polarization Pa. Figure 8f The top portion of the coupler (selected by one of the optical circulator switches SW) propagates the emitted radiation Re from the distributor at the first input of the coupler C. Reflected radiation Rr from the second input of the coupler C can propagate towards the mixer M. In this configuration, the selected coupler C is configured to emit an emitted beam with a first polarization Pa.

[0119] By following the second configuration ( Figure 8f The bottom portion of the switch SW1 and SW2 is switched, and the emitted radiation Re propagates from the distributor S to the second input of the coupling device C selected by one of the optical circulator switches SW. The reflected radiation Rr propagates from the first input of the coupling device C toward the mixer M. In this second configuration, the coupling device C is configured to emit an emitted beam with a second polarization Pb perpendicular to the first polarization Pa.

[0120] In other words, the two switches SW1 and SW2 allow the emitted radiation Re to be selectively propagated in the bidirectional transmission bus BT along a first propagation direction or a second propagation direction opposite to the first propagation direction. Depending on the propagation direction of this radiation, an emitted beam with a first polarization Pa or a second polarization Pb perpendicular to the first polarization Pa is emitted through the coupling device C associated with the bidirectional transmission bus via the optical circulator switch SW.

[0121] Of course, the present invention is not limited to the described embodiments, and variations may be added without departing from the scope of the invention as defined by the claims.

Claims

1. A photonic component (100) comprising at least one photonic chip (10) and at least one optical component (20). - The photonic chip includes at least one transceiver circuit (1), the at least one transceiver circuit (1) including at least one laser source (L) for providing a first radiation called a local oscillator (LO) to an optical mixer (M) and for providing emitted radiation (Re) to a coupling device (C), the local oscillator (LO) and the emitted radiation (Re) having a predetermined polarization, the coupling device (C) being configured to propagate the emitted radiation (Re) in the form of an emitted beam from a measurement surface (Sm) in free space, and to receive a reflected beam returning from the same measurement surface (Sm) and guide the reflected beam toward the optical mixer (M) as reflected radiation (Rr) having the predetermined polarization, the optical mixer (M) generating a measurement signal (V) through interference pulses of the local oscillator (LO) and the reflected radiation (Rr); - The optical component (20) is provided with a Faraday rotator (20a) arranged on the measurement surface (Sm) of the chip (10) to intercept the emitted beam and the reflected beam. The optical component is also provided with a polarizer (20b) arranged downstream of the Faraday rotator along the propagation direction of the emitted beam and configured to allow the emitted beam and the reflected beam to be transmitted with a single polarization that matches the polarization applied to the emitted beam by the Faraday rotator.

2. The photonic component (100) according to claim 1, wherein, The laser source (L) includes or is associated with a frequency modulator (FM).

3. The photonic component (100) according to claim 1 or 2, wherein, The photonic chip includes a power divider (S) optically associated with the laser source (L), the power divider providing the local oscillator (LO) and the emitted radiation (Re).

4. The photonic component (100) according to claim 1 or 2, wherein, The coupling device (C) of the transceiver circuit (1) includes a first waveguide (Ga) and a second waveguide (Gb) and an edge coupler (EC) disposed between the first waveguide and the second waveguide, the edge coupler being optically connected to a polarization beam splitter (PBS) and a polarization rotator (PR).

5. The photonic component (100) according to claim 1 or 2, wherein, The coupling device (C) of the transceiver circuit (1) includes a first waveguide (Ga) and a second waveguide (Gb) and a surface coupler with a polarization splitter grating (GC) disposed between the first waveguide and the second waveguide.

6. The photonic component (100) according to claim 1 or 2, wherein, The transceiver circuit (1) includes a first measurement channel and a second measurement channel. The first measurement channel is used to propagate a first emission beam with a first propagation polarization (Pa) at the chip output section, and the second measurement channel is used to propagate a second emission beam with a second propagation polarization (Pb) orthogonal to the first propagation polarization (Pa).

7. The photonic component (100) according to claim 6, wherein, The first emitted beam propagates through a first coupling device (C), and the second emitted beam propagates through a second coupling device (C') that is separate from the first coupling device (C).

8. The photonic component (100) according to claim 7, wherein, The transceiver circuit (1) includes a first switch (SW1) and a second switch. The first switch (SW1) is optically arranged between the laser source (L) and the first coupling device (C) and the second coupling device (C'), and the second switch is optically arranged between the first coupling device (C), the second coupling device (C') and the mixer.

9. The photonic component (100) according to claim 6, wherein, The transceiver circuit (1) includes: - First switch (SW1'), the first switch (SW1') is used to selectively connect the first waveguide (Ga) of the multiplexing coupling device (C'') to the laser source (L) or the mixer (M); - Second switch (SW2'), the second switch (SW2') is used to selectively connect the second waveguide (Gb) of the multiplexing coupling device (C) to the laser source (L) or the mixer (M).

10. The photonic component (100) according to claim 1 or 2, wherein, The photonic chip includes multiple transceiver circuits (1).

11. The photonic component (100) according to claim 1, wherein, The transceiver circuit (1) includes multiple coupling devices (C).

12. The photonic component (100) according to claim 11, wherein, The at least one laser source (L) emits radiation (R) having multiple wavelengths (l1, l2, ln), and wherein the transceiver circuit (1) includes a wave demultiplexer (D) for distributing the wavelengths of the radiation toward the coupling device (C) optically connected to the output of the demultiplexer (D) (Ds(l1), Ds(l2), Ds(ln)).

13. The photonic component (100) according to claim 12, wherein, The transceiver circuit (1) includes multiple laser sources (L1, L2, Ln) that respectively emit the multiple wavelengths (l1, l2, ln), and the transceiver circuit (1) also includes a wavelength division multiplexer (DM) for generating the radiation (R) having the multiple wavelengths.

14. The photonic component (100) according to claim 12 or 13, wherein, The outputs (Ds(l1), Ds(l2), Ds(ln)) of the demultiplexer (D) are respectively connected to the power divider (S), which provides local oscillators (LO(l1), LO(l2), LO(ln)) to the mixer (M) and provides emission radiation (Re(l1), Re(l2), Re(ln)) to the coupling device (C).

15. The photonic component (100) according to claim 11, wherein, The transceiver circuit (1) includes: - A unidirectional transmit bus (BE) optically connected to the laser source (L) and a receive bus (BR) optically connected to the mixer (M), wherein the plurality of coupling devices (C) are optically arranged between the unidirectional transmit bus (BE) and the receive bus (BR). - A first plurality of transmission elements (F1, SW1) arranged between the unidirectional transmit bus (BE) and the plurality of coupling devices (C) to selectively connect the unidirectional transmit bus (BE) to a predetermined coupling device (C) and allow the propagation of the emitted radiation (Re); - A second plurality of transmission elements (F2, SW2) are arranged between the plurality of coupling devices (C) and the receiving bus (BR) to selectively connect the predetermined coupling devices (C) to the receiving bus (BR) and allow the propagation of the reflected radiation (Rr).

16. The photonic component (100) according to claim 15, wherein, The transmission elements are filters (F1, F2), each of which is associated with a coupling device (C), and the filters (F1, F2) have the same transmission wavelength range.

17. The photonic component (100) according to claim 15, wherein, The transmission elements are switches (SW1, SW2).

18. The photonic component (100) according to claim 11, wherein, The transceiver circuit (1) includes a bidirectional transmission bus (BT) arranged optically between the power divider (S) and the mixer (M), the bidirectional transmission bus (BT) being selectively connected to the coupling device (C) via an optical circulator switch (SW).

19. The photonic component (100) according to claim 18, wherein, The photonic chip also includes two switches (SW1, SW2) for selectively propagating the emitted radiation in the bidirectional transmission bus (BT) along a first propagation direction or along a second propagation direction opposite to the first propagation direction.

20. The photonic assembly (100) according to claim 1 or 2, the photonic assembly (100) further comprising a lens (L) for collimating the emitted beam and the reflected beam.

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