Optical coherence imager with shared input-output path and method for sensing coherent light

Abstract

The present disclosure provides an optical coherence imager implemented on a photonic integrated circuit (PIC) that achieves a shared path for transmitting and receiving optical signals by exploiting polarization diversity. The present disclosure also provides an optical coherence imager that includes an array of optical coherence sensing cells to simplify the design and calibration of the imager, and a method for coherent sensing by the optical coherence imager.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of priority to U.S. Provisional Application No. 63 / 147,733, filed February 9, 2021, the entire contents of which are incorporated herein by reference for all purposes.

[0003] Statement regarding federally funded research or development

[0004] This invention was completed with government support granted by the National Science Foundation, grant number 2015160. The government holds certain rights to this invention. Technical Field

[0005] This disclosure relates to an optical coherent imager with a shared input-output path and a method for sensing coherent light. More specifically, this disclosure relates to a photonic integrated circuit with a polarization diversity-based shared input-output path and a method for sensing coherent light. Background Technology

[0006] An optical coherent imager is an active imaging system comprising an array of optical detectors (referred to herein as "sensors") and a light source (typically a coherent light source such as a laser). The light source is used for target illumination and to provide a local oscillator (LO) for optical coherent detection (also known as optical heterodyne detection). Such optical coherent imagers can be used in applications including three-dimensional (3D) frequency-modulated continuous wave (FMCW) lidar (LIDAR) and optical coherence tomography (OCT). The illumination light reflected (or scattered) by the target and received by the imager is referred to herein as the received optical target signal, or simply the target signal.

[0007] Traditionally, to perform optical coherent detection, optical coherent imagers operate by coherently combining the LO (Local Optical Detection) with the target signal in free space using bulk optics prior to detection by the imager's sensor. In contrast, optical coherent imagers with detection sensors based on photonic integrated circuit (PIC) technology allow the mixing of the LO and target signals on a photonic chip (also referred to herein as a PIC chip). More specifically, PIC-based sensors include an array of coherent sensing units that function as active detection pixels in conventional detection arrays, such as charge-coupled devices (CCDs) or complementary metal-oxide-semiconductor (CMOS) image sensors. Instead of performing photodetection directly at the pixel in a conventional detection array, the coherent sensing units of the PIC-based sensor couple the target signal from free space to multiple waveguides on the PIC chip via free-space-to-waveguide couplers. Then, various photonic components implemented on the PIC chip can be used to manipulate and process target signals that behave as waveguide modes in the waveguide, including coherent mixing with the LO using a 2×2 optical coupler and detection by a photodetector. Here, the LO can be introduced into the PIC chip via a coupler to behave as a waveguide mode. With recent advancements in monolithic and heterogeneous integration of lasers on PIC chips, light sources can even be integrated onto the same PIC chip as a PIC-based sensor.

[0008] For target illumination, two methods are typically used in active imagers: (1) full field illumination and (2) limited field illumination using a scanning beam.

[0009] With full-field illumination, the target scene is flooded with illumination light, causing the sensor's entire instantaneous field of view (FOV) to receive optical signals reflected or scattered from the scene. Advantages of the full-field approach include high frame rates and simplified data post-processing output formats, as it allows the sensor to acquire images like a conventional camera. A significant disadvantage of the full-field approach is that the illumination laser power is distributed over a large area, resulting in fewer photons reflected or scattered back to each sensing unit of the imager sensor. Therefore, the full-field approach requires imager sensors with higher sensitivity, which typically necessitates the use of exotic and expensive materials to fabricate the sensors. Furthermore, due to practical factors such as eye safety, the full-field approach may also limit the operation of active imagers within distances limited by the maximum illumination laser power.

[0010] For finite-field illumination using a scanning beam, the laser beam is manipulated using certain scanning mechanisms to scan the target scene. At each scan position, only the imager sensor's finite field of view (FOV) receives the target signal. This finite FOV depends on the spot size of the illumination laser beam and the imager's imaging optics. Because the FOV used in finite-field illumination methods is relatively small, the laser power is concentrated in a smaller area, resulting in the imager sensor receiving more photons at the corresponding FOV. Therefore, given the same illumination laser power, finite-field illumination methods typically allow active imagers to operate over longer distances than full-field illumination methods.

[0011] For optical coherent imagers utilizing PIC-based sensors and operating with a limited-field illumination method, the beam-scanning mechanism can be implemented on the same PIC chip as the sensor to reduce the imager's manufacturing cost. Common beam-scanning mechanisms that can be implemented on a PIC chip include optical phased arrays (OPAs). However, the photonic component used for the beam-scanning mechanism (referred to herein as the "emitter") is typically implemented in a region of the PIC chip separate from the detection region, which includes the free space-to-waveguide coupler of the PIC-based sensor (also referred to herein as the "receiver"). Due to this separation, the transmitter and receiver may require separate optical systems to guide the illumination beam to the target separately and to maximize the coupling of the target signal to the receiver.

[0012] In optical coherent imagers utilizing limited-field illumination, it may be desirable for the transmitter and receiver to share the same optical system for illuminating the target and receiving the target signal, respectively. Even more desirable is that the outgoing probe beam and the incident target signal follow the same optical path. The advantages of such an input-output path-sharing imager include a simplified optical system and simplified calibration between the transmitter and receiver. The simplified optical system can lead to more efficient use of laser power by enabling the imager to supply LO light more specifically to only those coherent sensing units that receive signals from the target during beam scanning.

[0013] References

[0014] 1. US Patent No. 7,006,732B2, filed December 12, 2003, entitled “Polarization Splitting Grating Couplers” by Lawrence C. Gunn, III, Thierry J. Pinguet, Maxime J. Rattier, and Jeremy Witzens.

[0015] 2. Bing Shen, Peng Wang, Randy Polson, and Rajesh Menon, “Integrated metamaterials for efficient and compact free-space-to-waveguide coupling,” Optics Express, Vol. 22, pp. 27175-27182 (2014).

[0016] 3. "Polarization-independent grating couplers for silicon-on-insulator nanophotonic waveguides", Optics Letters, Vol.36, No.6, pp.796-798 (2011).

[0017] 4. “AWide-angle Multi-Octave Broadband Waveplate Based on FieldTransformation Approach,” Scientific Reports, 5, 17532 (2015), p. 17532.

[0018] 5. "Broadband TE Optical Isolators and Circulators in Silicon Photonics Through Ce:YIG Bonding," Journal of Lightwave Technology, Vol. 37, No. 5, p. 1463 (2019) by Paolo Pintus, Duanni Huang, Paul Adrian Morton, Yuya Shoji, Tetsuya Mizumoto, and John E. Bowers. Summary of the Invention

[0019] This disclosure provides an optical coherent imager implemented on a photonic integrated circuit (PIC) that utilizes polarization diversity to achieve a shared path for transmitting and receiving optical signals. This disclosure also provides an optical coherent imager including an array of optical coherent sensing units to simplify imager design and calibration, and a method for performing coherent sensing through the optical coherent imager.

[0020] In one aspect, this disclosure provides an optical coherent sensor comprising a plurality of coherent sensing units and polarization converters disposed on the coherent sensing units. Each coherent sensing unit comprises: a polarization diversity optical coupler capable of guiding an optical signal having a first polarization state to free space and a first waveguide and guiding an optical signal having a first polarization state from free space and the first waveguide, and capable of guiding an optical signal having a second polarization state to free space and a second waveguide and guiding an optical signal having a second polarization state from free space and the second waveguide; one or more 2×2 optical couplers optically coupled to the polarization diversity optical coupler via at least one of the first and second waveguides; and one or more photodetectors optically coupled to the 2×2 optical coupler.

[0021] In one embodiment, the polarization diversity optical coupler includes a first sub-coupler and a second sub-coupler.

[0022] In one embodiment, one of the first and second sub-couplers is polarization-dependent and optimally coupled to an optical signal of a predetermined polarization state, and the other sub-coupler is polarization-independent and optimally coupled to an optical signal of any polarization state.

[0023] In one embodiment, the second sub-coupler is disposed on the first sub-coupler and is perpendicularly separated from the first sub-coupler.

[0024] In one embodiment, the first sub-coupler and the second sub-coupler are disposed on the photonic substrate and are laterally separated from each other.

[0025] In one embodiment, the polarization converter guides the outgoing optical signal from one of the first and second sub-couplers into the optical path in free space, and separates the incident optical signal from the optical path into a first optical signal with a first polarization state and a second optical signal with a second polarization state. One or both of the first and second optical signals are spatially shifted by the polarization converter, such that the first and second optical signals are respectively incident on the first and second sub-couplers.

[0026] In one embodiment, the polarization converter includes at least one polarization-dependent beam splitter.

[0027] In one embodiment, the polarization converter includes one or more polarization transducers that rotate a linearly polarized optical signal by a predetermined angle.

[0028] In one embodiment, at least one polarization converter is a Faraday rotator.

[0029] In one embodiment, the polarization converter includes one or more quarter-wave plates.

[0030] In one embodiment, the polarization diversity optical coupler further includes a third sub-coupler. In one embodiment, the first, second, and third sub-couplers are disposed on a photonic substrate and are laterally separated from each other.

[0031] In one embodiment, the polarization converter guides the outgoing optical signal from one of the first, second, and third sub-couplers into an optical path in free space, and separates the incident optical signal from the optical path into a first optical signal with a first polarization state and a second optical signal with a second polarization state. One or both of the first and second optical signals are spatially shifted by the polarization converter, such that the first and second optical signals are respectively incident on two of the first, second, and third sub-couplers.

[0032] In one embodiment, the polarization diversity optical coupler further includes a fourth sub-coupler.

[0033] In one embodiment, the polarization converter guides the outgoing optical signals from two of the first, second, third, and fourth sub-couplers into an optical path in free space, and separates the incident optical signals from the optical path into a first optical signal with a first polarization state and a second optical signal with a second polarization state. One or both of the first and second optical signals are spatially shifted by the polarization converter, such that the first and second optical signals are respectively incident on two of the first, second, third, and fourth sub-couplers.

[0034] In another aspect, this disclosure provides an optical coherent imager, which includes the aforementioned optical coherent sensor and an imaging optical system including a plurality of lenses, wherein the imaging optical system is configured such that the optical coherent sensor is located near the imaging plane of the imaging optical system.

[0035] In another aspect, this disclosure provides a method for optical coherent imaging, comprising: transmitting one or more outgoing optical signals from an optical coherent imager along one or more optical paths toward one or more targets, the one or more optical paths corresponding to one or more field-of-view positions of the optical coherent imager; receiving one or more incident optical signals reflected from targets illuminated by the outgoing optical signals along the optical paths by the optical coherent imager; converting each incident optical signal into a first optical component having a first polarization state and a second optical component having a second polarization state by a polarization converter of the optical coherent imager, wherein the first polarization state and the second polarization state are orthogonal; and directing the first and second optical components of the incident optical signals to one or more photodetectors of the optical coherent sensor by one or more polarization diversity optical couplers on the optical coherent imager, so as to perform heterodyne detection using local oscillator light at each field-of-view position of the optical coherent imager, thereby determining information about the target at the field-of-view position.

[0036] In one embodiment, emitting an outgoing optical signal includes: generating one or more source optical signals from a light source; converting the source optical signals into outgoing optical signals by a polarization diversity optical coupler, wherein each outgoing optical signal has a first emission polarization state; and emitting the outgoing optical signal from the polarization diversity optical coupler.

[0037] In one embodiment, after emitting an outgoing optical signal from the polarization diversity optical coupler, the method further includes converting each outgoing optical signal from a first emission polarization state to a second emission polarization state by a polarization converter of the optical coherence imager.

[0038] In one embodiment, converting the incident optical signal includes rotating the first polarization state of each incident optical signal by a first predetermined polarization angle and rotating the second polarization state of each incident optical signal by a second predetermined polarization angle.

[0039] In one embodiment, converting the incident optical signal includes spatially shifting at least one of a first component and a second component of each incident optical signal according to a first polarization state and a second polarization state, such that the first component and the second component are respectively incident on a first sub-coupler and a second sub-coupler in each polarization diversity optical coupler. Attached Figure Description

[0040] Those skilled in the art will understand that the accompanying drawings are primarily for illustrative purposes and are not intended to limit the scope of the disclosed subject matter. The drawings are not necessarily drawn to scale; in some cases, various aspects of the disclosed subject matter may be exaggerated or enlarged in the drawings to facilitate understanding of different features.

[0041] Figure 1AA plan view of a coherent sensing unit for transmitting and receiving optical signals based on polarization diversity, according to an embodiment of the present disclosure, is shown.

[0042] Figure 1B A perspective view of a polarization diversity free space to waveguide coupler according to an embodiment of the present disclosure is shown.

[0043] Figure 2 A perspective view of a polarization diversity free space to waveguide coupler according to another embodiment of the present disclosure is shown.

[0044] Figure 3 A perspective view of a polarization diversity free-space to waveguide coupler according to another embodiment of the present disclosure is shown.

[0045] Figure 4A A side view is shown of a polarization separation configuration for internally coupled optical signals according to an embodiment of the present disclosure.

[0046] Figure 4B This shows the use of externally coupled optical signals. Figure 4A A side view of the polarization separation configuration in the image.

[0047] Figure 4C This illustrates the use of internal and external coupling of optical signals. Figure 4A A side view of the polarization separation configuration in the image.

[0048] Figure 5A A perspective view showing a polarization transformation configuration achieved by the Faraday effect according to an embodiment of the present disclosure.

[0049] Figure 5B Show Figure 5A A top view of the polarization state of the optical signal in the image.

[0050] Figure 5C This illustrates a combination according to embodiments of the present disclosure. Figure 5A Polarization transformation configuration and Figure 4C A side view of the polarization transformation separation configuration in the polarization separation configuration.

[0051] Figure 6A A perspective view showing a polarization transformation configuration implemented by a quarter-wave plate according to another embodiment of the present disclosure.

[0052] Figure 6B Show Figure 6A A top view of the polarization state of the optical signal in the image.

[0053] Figure 6C This illustrates a combination according to another embodiment of the present disclosure. Figure 6A Polarization transformation configuration and Figure 4C A side view of the polarization transformation separation configuration in the polarization separation configuration.

[0054] Figure 7A A plan view of a coherent sensing unit for transmitting and receiving optical signals based on polarization diversity, according to another embodiment of the present disclosure, is shown.

[0055] Figure 7B A plan view of a coherent sensing unit for transmitting and receiving optical signals based on polarization diversity, according to yet another embodiment of the present disclosure, is shown.

[0056] Figure 8 A plan view of a coherent sensing unit for transmitting and receiving optical signals based on polarization diversity, according to another embodiment of the present disclosure, is shown.

[0057] Figure 9 A plan view of a coherent sensing unit for transmitting and receiving optical signals based on polarization diversity, according to yet another embodiment of the present disclosure, is shown.

[0058] Figure 10A A top view of a three-waveguide polarization diversity free-space to waveguide coupler according to an embodiment of the present disclosure is shown.

[0059] Figure 10B Show Figure 10A The perspective view of the coupler shown.

[0060] Figure 10C A side view of a polarization transformation separation configuration according to an embodiment of the present disclosure is shown, which is used in conjunction with a three-waveguide polarization diversity free space to waveguide coupler for external coupling of optical signals.

[0061] Figure 10D This illustrates the use of internally coupled optical signals. Figure 10C The side view of the configuration shown.

[0062] Figure 10E Show Figure 10C A top view of the polarization state of the optical signal in the image.

[0063] Figure 10F Show Figure 10D A top view of the polarization state of the optical signal in the image.

[0064] Figure 11A A perspective view of a three-waveguide polarization diversity free-space to waveguide coupler according to another embodiment of the present disclosure is shown.

[0065] Figure 11B A side view of a polarization transformation separation configuration according to another embodiment of the present disclosure is shown, which is used in conjunction with a three-waveguide polarization diversity free space to waveguide coupler for external coupling of optical signals.

[0066] Figure 11C This illustrates the use of internally coupled optical signals. Figure 11B The side view of the configuration shown.

[0067] Figure 11D Show Figure 11B A top view of the polarization state of the optical signal in the image.

[0068] Figure 11E Show Figure 11C A top view of the polarization state of the optical signal in the image.

[0069] Figure 12A A side view of a polarization transformation separation configuration according to another embodiment of the present disclosure is shown, which is used in conjunction with a three-waveguide polarization diversity free space to waveguide coupler for external coupling of optical signals.

[0070] Figure 12B This illustrates the use of internally coupled optical signals. Figure 12A The side view of the configuration shown.

[0071] Figure 12C Show Figure 12A A top view of the polarization state of the optical signal in the image.

[0072] Figure 12D Show Figure 12B A top view of the polarization state of the optical signal in the image.

[0073] Figure 13A A top view of a three-waveguide polarization diversity free-space to waveguide coupler according to another embodiment of the present disclosure is shown.

[0074] Figure 13B Show Figure 13A The perspective view of the coupler shown.

[0075] Figure 13C A side view of a polarization transformation separation configuration according to yet another embodiment of the present disclosure is shown, which is used in conjunction with a three-waveguide polarization diversity free space to waveguide coupler for external coupling of optical signals.

[0076] Figure 13D Show Figure 13C Another side view of the configuration shown.

[0077] Figure 13E This illustrates the use of internally coupled optical signals. Figure 13C The side view of the configuration shown.

[0078] Figure 13F Show Figure 13E Another side view of the configuration shown.

[0079] Figure 13G Show Figure 13C and Figure 13D A top view of the polarization state of the optical signal and its path position in the xy plane.

[0080] Figure 13H Show Figure 13E and Figure 13F A top view of the polarization state of the optical signal and its path position in the xy plane.

[0081] Figure 14 A plan view of a coherent sensing unit for transmitting and receiving optical signals based on polarization diversity, according to an embodiment of the present disclosure, wherein the polarization of the transmitted optical signal is adjustable.

[0082] Figure 15A A top view of a four-waveguide polarization diversity free-space to waveguide coupler according to an embodiment of the present disclosure is shown.

[0083] Figure 15B Show Figure 15A The perspective view of the coupler shown.

[0084] Figure 15C A side view of a polarization transformation separation configuration according to an embodiment of the present disclosure is shown, which is used in conjunction with a four-waveguide polarization diversity free space to waveguide coupler for external coupling of optical signals.

[0085] Figure 15D Show Figure 15C Another side view of the configuration shown.

[0086] Figure 15E Show Figure 15C and Figure 15D A top view of the polarization state of the optical signal and its path position in the xy plane.

[0087] Figure 15F This illustrates the use of internally coupled optical signals. Figure 15C The side view of the configuration shown.

[0088] Figure 15G Show Figure 15F Another side view of the configuration shown.

[0089] Figure 15H Show Figure 15F and Figure 15G A top view of the polarization state of the optical signal and its path position in the xy plane.

[0090] Figure 16A A top view of a four-waveguide polarization diversity free-space to waveguide coupler according to another embodiment of the present disclosure is shown.

[0091] Figure 16B Show Figure 16A The perspective view of the coupler shown.

[0092] Figure 16C A side view of a polarization transformation separation configuration according to another embodiment of the present disclosure is shown, which is used in conjunction with a four-waveguide polarization diversity free space to waveguide coupler for external coupling of optical signals.

[0093] Figure 16D This illustrates the use of internally coupled optical signals. Figure 16C The side view of the configuration shown.

[0094] Figure 16E Show Figure 16C A top view of the polarization state of the optical signal in the image.

[0095] Figure 16F Show Figure 16D A top view of the polarization state of the optical signal in the image.

[0096] Figure 17A A perspective view of a four-waveguide polarization diversity free-space to waveguide coupler according to another embodiment of the present disclosure is shown.

[0097] Figure 17B A side view of a polarization transformation separation configuration according to another embodiment of the present disclosure is shown, which is used in conjunction with a four-waveguide polarization diversity free space to waveguide coupler for external coupling of optical signals.

[0098] Figure 17C This illustrates the use of internally coupled optical signals. Figure 17B The side view of the configuration shown.

[0099] Figure 17D Show Figure 17B A top view of the polarization state of the optical signal in the image.

[0100] Figure 17E Show Figure 17C A top view of the polarization state of the optical signal in the image.

[0101] Figure 18A A plan view of a coherent optical sensor according to an embodiment of the present disclosure is shown.

[0102] Figure 18B A row of coherent sensing units of a coherent sensing array according to an embodiment of the present disclosure is shown.

[0103] Figure 19A A plan view of a coherent optical sensor according to another embodiment of the present disclosure is shown.

[0104] Figure 19B A plan view of a coherent sensing unit group according to an embodiment of the present disclosure is shown.

[0105] Figure 20A A plan view of a coherent optical sensor according to another embodiment of the present disclosure is shown.

[0106] Figure 20B A plan view of a coherent sensing unit group according to another embodiment of the present disclosure is shown.

[0107] Figure 20C A plan view of an optical switch based on a Mach-Zehnder interferometer according to an embodiment of the present disclosure is shown.

[0108] Figure 21A A side view of an optical coherent imager according to an embodiment of the present disclosure is shown.

[0109] Figure 21B Show Figure 21A A close-up view of the imager near the final image plane.

[0110] Figure 21C Show Figure 21B Polarization diagrams of ordinary and extraordinary rays on the final image plane in the field of view of an optical coherent imager.

[0111] Figure 22A A side view of an optical coherent imager according to another embodiment of the present disclosure is shown.

[0112] Figure 22B A side view is shown of light propagating through a polarization-dependent beam splitter that achieves angular displacement and light propagating through a polarization-dependent beam splitter that achieves lateral displacement, according to an embodiment of the present disclosure.

[0113] Figure 23 A flowchart illustrating a method for optical coherent imaging using polarization diversity to achieve a shared path for transmitting and receiving optical signals, according to an embodiment of the present disclosure. Detailed Implementation

[0114] The following detailed description includes systems, methods, techniques, and sequences of instructions illustrating embodiments of the present disclosure. In this description, numerous specific details are set forth for purposes of explanation in order to provide an understanding of various embodiments of the subject matter of the invention. However, it will be apparent to those skilled in the art that embodiments of the subject matter of the invention may be practiced with or without these specific details. Examples of instructions, protocols, structures, and techniques well known to those skilled in the art are not necessarily shown in detail.

[0115] Figure 1A A plan view of a coherent sensing unit 100 for transmitting and receiving optical signals based on polarization diversity, according to an embodiment of the present disclosure, is shown. Multiple coherent sensing units 100 can be used to form a coherent sensor array of an optical coherent imager. Figure 1B This diagram shows a perspective view of the polarization diversity free space of a coherent sensing unit 100 according to an embodiment of the present disclosure, directed to a waveguide coupler 101. The coherent sensing unit 100 can be implemented on a photonic substrate using photonic integrated circuit (PIC) technology. The surface of the photonic substrate can be made of... Figure 1A and Figure 1B The coordinate system shown is represented by the planes spanned by the x and y axes. The photonic components of the coherent sensing unit 100 implemented on the photonic substrate may or may not be covered by a cladding. Such components may or may not be embedded in the cladding. For simplicity, Figure 1A and Figure 1B The photonic substrate and coating are not shown in other figures of this disclosure. Furthermore, in the following description of this disclosure, the target to be detected by the optical coherent imager is considered to be located away from the substrate surface along the positive z-direction, and, where applicable, at any optical component above the substrate surface. For simplicity, the target is not explicitly shown in the figures.

[0116] PIC chips feature various common photonic waveguide designs, including but not limited to ridge waveguides, rib waveguides, buried waveguides, and slot waveguides. According to some embodiments, the waveguide of the coherent sensing unit 100 of this disclosure can be based on… Figure 1A and Figure 1B The coordinate system in the illustrated embodiment is fabricated with a dimension along the z-direction smaller than that in the xy-plane, and is configured to support various waveguide modes, including but not limited to transverse electric (TE) modes, transverse magnetic (TM) modes, and both TE and TM modes. Here, a TE mode can refer to a waveguide mode having a dominant conductive field component transverse to the mode's propagation direction and the surface of the photonic substrate on which the waveguide is located, while a TM mode can refer to a waveguide mode having a dominant magnetic field component transverse to the mode's propagation direction and the surface of the photonic substrate on which the waveguide is located. Those skilled in the art should be familiar with such common waveguide designs and the various modes supported by these waveguides.

[0117] refer to Figure 1A Light source signal E S Waveguide 121 can be provided to coherent sensing unit 100, while local oscillator (LO)E LO The light source signal E can be provided to the coherent sensing unit 100 via waveguide 123. S and LO E LOThe light sources may or may not originate from the same source. The light sources may or may not be implemented on the same PIC chip including the coherent sensing unit 100. According to some embodiments, E is generated by coupling in the waveguide of the PIC chip including the coherent sensing unit 100. S and E LO The proper design of the system and method for the light source (or multiple light sources) can enable the light source signal E S In waveguide 121, it manifests as the basic TE mode and can enable LO E LO In waveguide 123, it manifests as a basic TE mode. Such a design is well known to those skilled in the art. According to other embodiments, the light source signal E can be intentionally made to... S In waveguide 121, this manifests as a TM mode or TE mode in addition to the basic TE mode. Similarly, according to some embodiments, LO E can be intentionally made LO In waveguide 123, it manifests as either a TM mode or a TE mode in addition to the basic TE mode.

[0118] exist Figure 1A In this design, the polarization diversity free space to waveguide coupler 101 (hereinafter referred to as coupler 101 for simplicity) can be used simultaneously as a transmitter and a receiver. It is a dual waveguide coupler connected to waveguides 121 and 122. The primary function of waveguide 121 is to guide the signal light to coupler 101, while the primary function of waveguide 122 is to receive the inner coupled light from coupler 101, although, according to some embodiments, the inner coupled light from coupler 101 can also be guided to waveguide 121. Therefore, with respect to coupler 101, waveguide 121 can be considered as the outer coupled waveguide, and waveguide 122 can be considered as the inner coupled waveguide. The distinguishing feature of the polarization diversity free space to waveguide coupler 101 is that when the incident optical signal (…) reaches coupler 101… Figure 1A E in in The polarization state of the output optical signal from coupler 101 and the output optical signal from coupler 101 Figure 1A E in the middle out When the polarization states of the incident optical signal are orthogonal, the incident optical signal can be internally coupled and guided to the internally coupled waveguide. Figure 1A Waveguide 122 in the middle), this inner coupled waveguide is different from the outer coupled waveguide ( Figure 1A (waveguide 121 in the text). Here and below, free space can refer to vacuum, air, the region above the surface of a coupler, or any homogeneous medium having a boundary with a length scale much larger (e.g., at least 10 times) than the wavelength of the optical signal propagating therein.

[0119] As a transmitter, coupler 101 can transmit the light source signal E from waveguide 121. SAs the emitted optical signal E out Coupled into free space, the emitted optical signal E out It can be used for target illumination in optical coherent imagers. The output optical signal E from coupler 101... out Propagates in directions outside the xy plane (i.e., E) out The propagation direction has a non-zero z-component, and the polarization is determined by the design of coupler 101. According to some embodiments, the polarization can be one of a pair of orthogonal linear polarizations, where the coordinate system can be... Figure 1A and Figure 1B The coordinate systems defined by the x-axis, y-axis, and z-axis shown may be the same or different. According to other embodiments, polarization may be a pair of orthogonal polarizations instead of one of a pair of linear polarizations, such as, but not limited to, right circular polarization and left circular polarization, and two orthogonal elliptic polarizations.

[0120] As a receiver, coupler 101 can transmit the incident optical signal E in Coupled to the coherent sensing unit 100. Incident optical signal E in Essentially, it is an optical signal from the previously described target (or target signal). The incident optical signal E coupled by coupler 101 in It can be guided to one or both of waveguides 121 and 122, depending on the incident optical signal E. in The polarization state of the incident optical signal E coupled to waveguides 121 and 122. in The polarization component depends on the design of coupler 101. According to some embodiments, it is related to the emitted optical signal E. out Orthogonally polarized incident optical signal E in The first polarization component can be used as the internally coupled optical signal E in(wg)1 It is guided to waveguide 122 and interacts with the incident optical signal E. in The first polarized orthogonal incident optical signal E in The second polarization component can be used as the internally coupled optical signal E in(wg)2 It is guided to waveguide 121. The following will refer to... Figure 1B Further details are provided regarding the two polarization components internally coupled to coupler 101. Internally coupled optical signal E in(wg)1 This can be processed by the remaining circuitry of the coherent sensing unit 100. Figure 1A In the middle, the internally coupled optical signal E in(wg)2 In relation to the light source signal E S The propagation direction is opposite to that of the optical signal E. According to some embodiments, the internally coupled optical signal E... in(wg)2It can be left unattended without affecting other parts of the PIC chip, including the coherent sensing unit 100. According to some embodiments, such as, but not limited to… Figure 7A In the embodiment shown, the internally coupled optical signal E in(wg)2 It can be processed by some other parts of the PIC chip, including the sensing unit 700.

[0121] exist Figure 1A Although coupler 101 is depicted as a single entity, it may comprise a single photonic component or multiple photonic components. In some aspects, coupler 101 may be implemented as a polarization-splitting free-space-to-waveguide coupler. Examples of polarization-splitting free-space-to-waveguide couplers include, but are not limited to, the polarization-splitting grating coupler described in U.S. Patent No. 7,006,732, “Polarization Splitting Grating Couplers,” and the metamaterial-based polarization-splitting free-space-to-waveguide coupling described in Optics Express 22, 27175-27182 (2014). Other examples of polarization-splitting free-space to waveguide couplers may include, but are not limited to, polarization-splitting free-space to waveguide couplers implemented through plasmonic effects or photonic micro / nanostructures or both. Other embodiments of coupler 101 are described below. Figure 2 and Figure 3 As shown in the figure. According to some embodiments, coupler 101 may also include any one of a TE-TM mode converter, a splitter, and a combiner. In some aspects, coupler 101 may include a single layer of photonic material. In other aspects, coupler 101 may include multiple layers of photonic material, wherein the photonic materials of different layers may be the same or different.

[0122] refer to Figure 1B According to some embodiments, the light source signal E propagates toward coupler 101. S This can be represented as a transverse electrical (TE) mode in waveguide 121. As an example, Figure 1B The light source signal E in S The dominant conductive field component along the x-direction propagates in the negative y-direction. Coupler 101 can then convert the light source signal E... S Coupled into free space to generate an outgoing optical signal E out The emitted optical signal Eout Polarization is performed according to the polarization determined by the design of coupler 101. For example, the emitted optical signal E out You can follow Figure 1B The x-direction is linearly polarized. In some cases, the emitted optical signal E out It can propagate in a direction perpendicular to the substrate surface. For example, as... Figure 1B E shown out It propagates in the z-direction. In other cases, the emitted optical signal E out It can propagate in a direction not perpendicular to the substrate surface, that is, E out It can propagate relative to the substrate surface in the direction of the tilt angle.

[0123] like Figure 1B As shown, the incident optical signal E in It may include one or both of the following two orthogonal polarization components: the first polarization component E in1 Second polarization component E in2 It should be understood that when the incident optical signal E in Includes only the first polarization component E in1 At that time, the second polarization component E in2 The amplitude is zero, and vice versa. Coupler 101 can be designed such that the first polarization component E in1 It can be like an internally coupled optical signal E in(wg)1 Thus, it is internally coupled and guided to waveguide 122, where the first polarization component E in1 With the emitted optical signal E out The polarizations are orthogonal. Similarly, coupler 101 can be designed such that the second polarization component E in2 It can be like an internally coupled optical signal E in(wg)2 Thus, it is internally coupled and guided to waveguide 121, and the internally coupled optical signal E in(wg)2 In relation to the light source signal E S It propagates in the opposite direction to the propagation direction. It is internally coupled and guided to the first polarization component E of waveguide 122. in1 With the emitted optical signal E out The polarizations are orthogonal, while the inner coupling and the second polarization component E is guided to waveguide 121. in2 With the first polarization E in1 Orthogonal. Second polarization E in2 It can be used with the emitted optical signal E out The polarizations can be the same or different (to achieve a scaling factor), because the emitted optical signal E out and incident optical signal E in It can propagate in the same or different directions. The incident optical signal E is coupled to waveguides 121 and 122. inThe specific polarization component depends on the design of coupler 101.

[0124] According to some embodiments, coupler 101 can be designed to optimally couple optical signals according to a preferred polarization base, referred to as the coupled polarization base. According to some embodiments, one component of the coupled polarization base can be related to the emitted optical signal E output by coupler 101. out Their polarizations are the same. For example... Figure 1B As shown, for example, the coupled polarization base can be a linear polarization base (e.g., x-polarization and y-polarization), and coupler 101 can internally couple the incident optical signal E. in The first linear polarization component E in1 (e.g., polarized along the y-direction), and guided to waveguide 122, where the first linear polarization component E in1 The emitted optical signal E with linear polarization out The polarization (e.g., the x-direction) is orthogonal and lies in a plane (e.g., the yz plane) parallel to the first component (i.e., the y-direction) of the coupled polarization base. Similarly, according to the linear polarization base, coupler 101 can internally couple the incident optical signal E. in The second linear polarization component E in2 (for example, along) Figure 1B (in the xz plane of the image), and guide it to waveguide 121, where the second linear polarization component E in2 The emitted optical signal E is located at a point with linear polarization. out The second polarization E lies in a plane (i.e., the xz plane) parallel to the polarization (i.e., the x-direction) and the second component (i.e., the x-direction) of the coupled polarization base, and the second polarization E in2 With the first polarization E in1 Orthogonal.

[0125] Coupler 101 can couple the incident optical signal component E from free space. in1 To generate an internally coupled optical signal E in waveguide 122. in(wg)1 According to some embodiments, the internally coupled optical signal E in(wg)1 This can be represented as a TE mode in waveguide 122. As an example, the internally coupled optical signal E... in(wg)1 With the main conductive field component along the y direction towards Figure 1B The signal propagates in the positive x-direction. Similarly, coupler 101 can couple the incident optical signal component E from free space. in2 To generate an internally coupled optical signal E in waveguide 121. in(wg)2 According to some embodiments, the internally coupled optical signal E in(wg)2 This can be represented as a TE mode in waveguide 121. As an example, the internally coupled optical signal E... in(wg)2With the main conductive field component along the x-direction towards Figure 1B It propagates in the positive y-direction.

[0126] In some respects, the internally coupled optical signal E in waveguide 122 in(wg)1 (If present) it can manifest as a single waveguide mode. According to some embodiments, the single waveguide mode can be a basic TE mode. According to other embodiments, the single waveguide mode can be a basic TM mode. According to further embodiments, the single waveguide mode can be a mode other than a basic TE mode or a basic TM mode. In other aspects, the internally coupled optical signal E in waveguide 122... in(wg)1 (If it exists) it can be represented as a combination of multiple waveguide modes.

[0127] Similarly, in some respects, the internally coupled optical signal E in waveguide 121 in(wg)2 (If present) it can manifest as a single waveguide mode. According to some embodiments, the single waveguide mode can be a basic TE mode. According to other embodiments, the single waveguide mode can be a basic TM mode. According to further embodiments, the single waveguide mode can be a mode other than a basic TE mode or a basic TM mode. In other aspects, the internally coupled optical signal E in waveguide 121... in(wg)2 (If it exists) it can be represented as a combination of multiple waveguide modes.

[0128] Although coupler 101 is designed to separate the orthogonal polarization components of the optical signal into two separate waveguides 121 and 122, cross-coupling is not uncommon in some embodiments of coupler 101. For example, see reference... Figure 1B Even if the incident optical signal E in It can be along with E out The polarization is orthogonal to the linear polarization of the polarization base and lies in a plane parallel to the first component of the linear polarization base (e.g., the incident optical signal is E). in1 Besides being guided to waveguide 122, E in In addition to the parts, E can also be included. in The non-zero portion is guided to waveguide 121. Similarly, for some embodiments, even if the incident optical signal E in It can be along the line located with E out The polarization of the signal is linearly polarized in a plane parallel to the second component of the linear polarization basis (e.g., the incident optical signal is E). in2 Besides being guided to waveguide 121, E in In addition to the part, E in The non-zero portion can also be guided to waveguide 122. Furthermore, in some embodiments, in addition to being coupled to free space by coupler 101 as the outgoing optical signal E, out E SApart from the part in waveguide 121, E S The non-zero portion can propagate directly to waveguide 122 through coupler 101. Such cross-coupling can be considered a design flaw of coupler 101. According to some embodiments, coupler 101 can be designed to maximize the coupling of each polarization component to its intended waveguide while minimizing cross-coupling.

[0129] According to some embodiments, the incident optical signal E in It can be coupled to coupler 101 at a spatial location on the surface of coupler 101, which is related to the emitted optical signal E emitted from coupler 101. out Even if E has the same spatial location, out and E in Drawn in Figure 1B At different spatial locations on the surface of the coupler 101. According to other embodiments, the incident optical signal E in It can be coupled to coupler 101 at a spatial location on the surface of coupler 101, which is different from the emitted optical signal E emitted from coupler 101. out Spatial location.

[0130] In some respects, coupler 101 can transmit the outgoing optical signal E out It is emitted into free space, and simultaneously the incident optical signal E is emitted. in It is coupled to the coherent sensing unit 100. In other aspects, the coupler 101 can couple the emitted optical signal E... out It is launched into free space, and the incident optical signal E is transmitted at different times. in It is coupled to the coherent sensing unit 100. Typically, the optical signal E in and E out It can propagate in the same or different directions, although Figure 1B Optical signal E in in and E out They are depicted as propagating in different directions.

[0131] Return to reference Figure 1A Component 102 is a 2×2 optical coupler that mixes the internally coupled optical signal E from waveguide 122. in(wg)1 And LO E from Waveguide 123 LOThe mixed signal is then split and directed to waveguides 124 and 125. Embodiments of the 2×2 optical coupler 102 include, but are not limited to, directional couplers and multi-mode interferometers (MMIs). The mixing and splitting ratio of the 2×2 optical coupler 102 depends on the design of the coupler 102. In some aspects, the 2×2 optical coupler 102 can have a 50 / 50 splitting ratio. In other aspects, the 2×2 optical coupler 102 can have a splitting ratio other than 50 / 50.

[0132] In some respects, the internally coupled optical signal E propagating in waveguide 122 in(wg)1 LO E propagating in waveguide 123 LO They can exhibit the same waveguide mode. In other aspects, the internally coupled optical signal E propagating in waveguide 122... in(wg)1 LO E propagating in waveguide 123 LO It can manifest as different waveguide modes. According to some embodiments, when the internally coupled optical signal E propagates in waveguide 122... in(wg)1 LO E propagating in waveguide 123 LO When manifested as different waveguide modes, the 2×2 optical coupler 102 may additionally include one or more mode converters at one or two of its input ports (i.e., waveguides 122 and 123) to couple the internally coupled optical signal E propagating in waveguide 122. in(wg)1 LO E propagating in waveguide 123 LO One or both of these conversions manifest as the same waveguide mode. According to other embodiments, the 2×2 optical coupler 102 may not include such a mode converter and can still mix, split, and guide the internally coupled optical signal E propagating in waveguide 122. in(wg)1 LO E propagating in waveguide 123 LO These manifest as different waveguide modes.

[0133] exist Figure 1A In this context, component 103 is a square-law photodetector (responding to the power of an optical signal proportional to the square of its electric field) that receives and detects optical signals from waveguide 124. Similarly, in Figure 1AIn this configuration, component 104 is a square-law photodetector that receives and detects optical signals from waveguide 125. According to some embodiments, the 2×2 optical coupler 102 may be a 50 / 50 2×2 optical coupler, and coupler 102, together with photodetectors 103 and 104, can form a balanced optical heterodyne detection setup. According to some embodiments, one of photodetectors 103 and 104 may be omitted from the coherent sensing unit 100, wherein the other remaining photodetector, together with coupler 102 (which may or may not be a 50 / 50 coupler), can form a single-detector optical heterodyne detection setup.

[0134] According to some embodiments, photodetectors 103 and 104 can be configured as a single combined photodetector having two optical inputs connected to waveguides 124 and 125. A combined photodetector with two optical inputs can measure any one or more of the intensity, sum of intensity, and difference of intensity of optical signals from the two inputs.

[0135] According to some embodiments, photodetectors 103 and 104 can be connected to an output electronic circuit that includes electronic components, such as, but not limited to, any one or more of a transimpedance amplifier (TIA), transistor, diode, resistor, capacitor, and electrical switch for processing the electrical output of photodetectors 103 and 104. This output electronic circuit... Figure 1A Not shown in the image.

[0136] exist Figure 1A In this context, the coherent sensing unit 100 may include components not explicitly shown, including but not limited to any one or more electro-optical components and thermo-optical components for phase, amplitude, frequency, wavelength and time control.

[0137] Figure 2A perspective view of a polarization diversity free-space to waveguide coupler 200 according to another embodiment of this disclosure is shown. Coupler 200 includes two sub-couplers 201 and 202 implemented on different layers of a PIC chip. According to some embodiments, one of the two sub-couplers 201 or 202 may be designed to optimally couple an optical signal having a specific polarization state, while the other sub-coupler may be designed to optimally couple an optical signal having a corresponding orthogonal polarization state. For example, sub-coupler 201 may be designed to optimally couple an incident or emitted optical signal E1 linearly polarized along a specific direction (e.g., along the x-direction), while sub-coupler 202 may be designed to optimally couple an incident or emitted optical signal E2 linearly polarized along a direction orthogonal to the polarization of E1 (e.g., along the y-direction). Sub-couplers 201 and 202 may be aligned or may not be aligned to the same xy position.

[0138] refer to Figure 2 Sub-coupler 201 can be a free-space to waveguide coupler, such as, but not limited to, a grating coupler, which can be optimally coupled to an optical signal E1 polarized according to polarization (e.g., linear polarization along the x-direction) and minimally coupled to an optical signal E2 polarized according to polarization orthogonal to the polarization of E1 (e.g., linear polarization along the y-direction). Similarly, sub-coupler 202 can be a free-space to waveguide coupler, such as, but not limited to, a grating coupler, which can be optimally coupled to an optical signal E2 polarized according to polarization (e.g., linear polarization along the y-direction) and minimally coupled to an optical signal E1 polarized according to polarization orthogonal to the polarization of E2 (e.g., linear polarization along the x-direction). Sub-couplers 201 and 202 may or may not be the same design. Typically, a pair of orthogonally polarized optical signals E1 and E2 that are optimally coupled to one of the sub-couplers 201 and 202 and minimally coupled to the other sub-coupler can be any of a pair of orthogonal linear polarizations, right circular polarizations and left circular polarizations, or a pair of orthogonal elliptic polarizations.

[0139] exist Figure 2 For illustrative purposes, orthogonal optical signals E1 and E2 are plotted at different spatial locations on the surfaces of sub-couplers 201 and 202. Typically, sub-coupler 201 can be optimally coupled to optical signal E1 and minimally coupled to E2 at the same or different spatial locations on its surface. Similarly, typically, sub-coupler 202 can be optimally coupled to optical signal E2 and minimally coupled to E1 at the same or different spatial locations on its surface.

[0140] exist Figure 2In the diagram, optical signals E1 and E2 are depicted propagating along a direction perpendicular to the plane of the substrate surface (i.e., along the z-direction). Typically, optical signals E1 and E2 can propagate along directions that are either perpendicular to or not perpendicular to the plane of the substrate surface. Furthermore, optical signals E1 and E2 can propagate along different directions, although... Figure 2 In the diagram, optical signals E1 and E2 are plotted as propagating in the same direction.

[0141] exist Figure 2 In this design, the cross-coupling between sub-couplers 201 and 202 can be minimized by selecting an appropriate vertical spacing 299 between them. The vertical spacing 299 can be formed by placing a photonic material layer (or air gap) with a thickness of 50 nanometers to 5 millimeters between sub-couplers 201 and 202. Typically, the selection of spacing 299 can depend on a combination of factors, including but not limited to PIC technology, manufacturing process, the photonic material used between sub-couplers 201 and 202, the wavelength of signal E1, the wavelength of signal E2, the design of sub-coupler 201, and the design of sub-coupler 202.

[0142] According to some embodiments, sub-coupler 201 may include a single layer of photonic material. According to other embodiments, sub-coupler 201 may include multiple layers of photonic material, wherein the photonic materials of different layers may be the same or different. Similarly, according to some embodiments, sub-coupler 202 may include a single layer of photonic material. According to other embodiments, sub-coupler 202 may include multiple layers of photonic material, wherein the photonic materials of different layers may be the same or different.

[0143] According to some embodiments, in order to Figure 1A Used in the coherent sensing unit 100, Figure 2 The sub-coupler 201 in the middle can be used as a transmitter, while Figure 2 Sub-coupler 202 can be used as a receiver, wherein sub-coupler 201, acting as a transmitter, is farther from the target, while sub-coupler 202, acting as a receiver, is closer to the target. In this case, Figure 2 Waveguide 221 in the middle can be with Figure 1A The waveguide 121, which serves as the external coupling waveguide, is the same as, or equivalently connected to, the waveguide 121, which serves as the external coupling waveguide, while Figure 2 Waveguide 222 in the middle can be with Figure 1A The waveguide 122 serving as the inner coupling waveguide is the same as, or equivalently connected to, the waveguide 122 serving as the inner coupling waveguide. According to other embodiments, in order to... Figure 1A Used in the coherent sensing unit 100, Figure 2 The sub-coupler 201 in the middle can be used as a receiver, while Figure 2Sub-coupler 202 can be used as a transmitter, wherein sub-coupler 201, acting as a receiver, is farther from the target, while sub-coupler 202, acting as a transmitter, is closer to the target. In this case, Figure 2 Waveguide 221 in the middle can be with Figure 1A The waveguide 122, which serves as the inner coupling waveguide, is the same as or equivalent to the waveguide 122, which serves as the inner coupling waveguide, and Figure 2 Waveguide 222 in the middle can be with Figure 1A The waveguide 121, which serves as the external coupling waveguide, is the same as or equivalent to the waveguide 121, which serves as the external coupling waveguide.

[0144] Figure 3 This diagram shows a perspective view of a polarization diversity free-space to waveguide coupler 300 according to another embodiment of the present disclosure. Coupler 300 includes two sub-couplers 301 and 302, which are implemented as two separate couplers on the same layer of a PIC chip. According to some embodiments, one of the two sub-couplers may be designed to be optimally coupled to an optical signal having a polarization state, while the other sub-coupler may be designed to be optimally coupled to an optical signal having a different polarization state. According to some embodiments, the two polarization states may be orthogonal to each other. According to other embodiments, the two polarization states may be non-orthogonal to each other. For example, sub-coupler 301 may be designed to be optimally coupled to an optical signal E1 linearly polarized along the x-direction, while sub-coupler 302 may be designed to be optimally coupled to an optical signal E2 linearly polarized along the y-direction.

[0145] refer to Figure 3 Sub-coupler 301 can be a free-space to waveguide coupler, such as, but not limited to, a grating coupler, which can be optimally coupled to an optical signal E1 polarized according to a specific polarization (e.g., linear polarization along the x-direction) and minimally coupled to an optical signal having a polarization orthogonal to the polarization of E1 (e.g., linear polarization along the y-direction). Similarly, sub-coupler 302 can be a free-space to waveguide coupler, such as, but not limited to, a grating coupler, which can be optimally coupled to an optical signal E2 polarized according to a specific polarization (e.g., linear polarization along the y-direction) and minimally coupled to an optical signal having a polarization orthogonal to the polarization of E2 (e.g., linear polarization along the x-direction). Sub-couplers 301 and 302 can be the same design or different designs.

[0146] According to other embodiments, one of the sub-couplers 301 and 302 can be designed to optimally couple to an optical signal having a polarization state, while the other sub-coupler can be a polarization-independent free space-to-waveguide coupler, designed to optimally couple to an optical signal having any polarization state. An example of a polarization-independent free space-to-waveguide coupler is described in "Polarization-independent grating couplers for silicon-on-insulator nanophotonic waveguides," Optics Letters Vol.36, No.6, p.796 (2011) . Reference Figure 3 On the one hand, sub-coupler 301 can be a free space-to-waveguide coupler, such as, but not limited to, a grating coupler, which can be optimally coupled to an optical signal E1 polarized according to one polarization (e.g., linear polarization along the x-direction) and minimally coupled to an optical signal having a polarization orthogonal to the polarization of E1 (e.g., linear polarization along the y-direction). On the other hand, sub-coupler 302 can be a polarization-independent free space-to-waveguide coupler, which can be optimally coupled to an optical signal E2 having any polarization, wherein the optical signal E2 can be orthogonal to the optical signal E1 or not.

[0147] exist Figure 3 In this design, cross-coupling between sub-couplers 301 and 302 can be minimized by selecting an appropriate lateral spacing 399 between the sub-couplers. The lateral spacing 399 can be formed by placing sub-couplers 301 and 302 on the same substrate surface but separated by a distance of 50 nanometers to 5 millimeters. Typically, the selection of the lateral spacing 399 can depend on a combination of factors, including but not limited to PIC technology, manufacturing process, photonic material used for the medium between sub-couplers 301 and 302, the wavelength of signal E1, the wavelength of signal E2, the design of coupler 301, and the design of coupler 302.

[0148] According to some embodiments, sub-coupler 301 may include a single layer of photonic material. According to other embodiments, sub-coupler 301 may include multiple layers of photonic material, wherein the photonic materials of different layers may be the same or different. Similarly, according to some embodiments, sub-coupler 302 may include a single layer of photonic material. According to other embodiments, sub-coupler 302 may include multiple layers of photonic material, wherein the photonic materials of different layers may be the same or different.

[0149] exist Figure 3In the diagram, optical signals E1 and E2 are depicted propagating along a direction perpendicular to the plane of the substrate surface (i.e., along the z-direction). Typically, optical signals E1 and E2 can propagate along directions that are either perpendicular to or not perpendicular to the plane of the substrate surface. Furthermore, optical signals E1 and E2 can propagate along different directions, although... Figure 3 In the diagram, optical signals E1 and E2 are plotted as propagating in the same direction.

[0150] According to some embodiments, in order to Figure 1A Used in the coherent sensing unit 100, Figure 3 The sub-coupler 301 in the middle can be used as a transmitter, while Figure 3 The neutron coupler 302 can be used as a receiver. In such a case, Figure 3 Waveguide 321 in the middle can be with Figure 1A The waveguide 121, which serves as the external coupling waveguide, is the same as, or equivalently connected to, the waveguide 121, which serves as the external coupling waveguide, while Figure 3 Waveguide 322 in the middle can be with Figure 1A The waveguide 122, which serves as the inner coupling waveguide, is the same as or equivalent to the waveguide 122, which serves as the inner coupling waveguide.

[0151] Figure 4A A side view is shown of a polarization separation configuration for internally coupled optical signals according to an embodiment of the present disclosure. Figure 4B This shows the use of externally coupled optical signals. Figure 4A A side view of the polarization separation configuration in the image. Figure 4C This illustrates the use of internal and external coupling of optical signals. Figure 4A A side view of the polarization separation configuration in the image. (See image for reference.) Figure 4A , Figure 4B and Figure 4C The polarization separation configuration shown can be used with Figure 3 The polarization diversity free space in the waveguide coupler 300 is used together to guide the optical signal E1 (coupled with sub-coupler 301) and the optical signal E2 (coupled with sub-coupler 302) to propagate along a common optical path in free space, wherein the common optical path is located between the optical component 401 and the target.

[0152] like Figure 4AThe polarization separation configuration shown includes a polarization-dependent beamsplitter 401. According to some embodiments, the polarization-dependent beamsplitter 401 may be a birefringent beamshifter. According to some embodiments, the birefringent beamshifter may be made of one or more materials, such as, but not limited to, calcite crystal, barium α-borate crystal, yttrium vanadate crystal, or rutile crystal. Birefringent beamshifters are well known in the art. According to other embodiments, the polarization-dependent beamsplitter 401 may be a polarization-dependent beamsplitter other than a birefringent beamshifter, such as, but not limited to, a birefringent wedge, a polarization beamsplitter, a polarization-dependent grating, or a polarization-dependent superlens.

[0153] According to some embodiments, the polarization-dependent beam splitter 401 may be a component separate from the PIC chip, which includes, for example, Figure 4A The polarization diversity free space to waveguide coupler 300 is shown. According to other embodiments, the polarization-dependent beamsplitter 401 may be attached to the surface of a PIC chip including the coupler 300. According to a further embodiment, the polarization-dependent beamsplitter 401 may be within or part of the PIC chip including the coupler 300.

[0154] For optical signal reception, according to Figure 4A In the embodiment described, the incident optical signal E in The polarization-correlated beam splitter 401 can reach the target. The polarization-correlated beam splitter 401 can split the incident optical signal E in The beam splits into two optical signals, E1 and E2, whose polarizations are orthogonal to each other. The splitting of the optical signals can depend on the polarization of the incident optical signal. One of the optical signals, E1 and E2, is an ordinary ray (o-ray), and the other is an extraordinary ray (e-ray). For example, optical signal E1 can be an o-ray, while optical signal E2 can be an e-ray. It should be understood that, in addition to their common usage in the case of birefringent beam splitters, the terms o-ray and e-ray used herein generally refer to two orthogonally polarized rays split by the polarization-dependent beam splitter 401, where the splitting is defined by the characteristics of the polarization-dependent beam splitter.

[0155] The polarization of optical signals E1 and E2 depends on the dielectric constant of the material of the polarization-dependent beam splitter 401, the orientation of the optical axis 498, and the incident optical signal E. in The angle of incidence. In this embodiment, the incident optical signal E inThe incident angle is close to the normal to the surface of the polarization-dependent beam splitter 401. Thus, the polarization-dependent beam splitter 401 can be manufactured and the optical axis 498 can be oriented such that when exiting and leaving the polarization-dependent beam splitter 401, the o-ray (E1) is polarized along the x-direction and the e-ray (E2) is polarized along the y-direction.

[0156] According to some embodiments, o-ray and e-ray (e.g., Figure 4A The optical signals E1 and E2 in the incident optical signal beam splitter 401 can be laterally displaced upon exiting the beam splitter 401. This lateral displacement can depend on any one or more factors, including but not limited to geometry (e.g., shape and thickness), the dielectric constant of the material, the orientation of the optical axis 498 of the beam splitter 401, and the incident optical signal E1. in The wavelength and angle of incidence. For the incident optical signal E in With near-normal incidence, o-ray E1 can propagate along a first optical path with a first lateral displacement (e.g., E1 continues with the incident optical signal E with zero lateral displacement). in The path, such as Figure 4A As shown in the diagram), e-ray E2 can travel along a path relative to... Figure 4A The incident optical signal E shown in The path has a second optical path propagation with a second lateral displacement of 499, wherein the second optical path of e-ray E2 is different from the first optical path of o-ray E1, and the second lateral displacement of e-ray E2 is different from the first lateral displacement of o-ray E1.

[0157] According to some embodiments, optical signals E1 and E2 can be incident on sub-couplers 301 and 302 at an angle close to normal incidence, such as... Figure 4A As shown in the diagram. According to other embodiments, optical signals E1 and E2 can be incident on sub-couplers 301 and 302 at angles different from the normal incidence angle. For incident optical signal E... in The polarization and propagation directions of o-ray E1 and e-ray E2, regardless of the incident angle and the properties of polarization-dependent beam splitter 401 (e.g., its geometry, dielectric constant, and optical axis orientation), can be determined by Maxwell's equations.

[0158] According to some embodiments, sub-coupler 301 can be configured to optimally couple with o-ray E1 based on the polarization and propagation direction of o-ray E1, wherein the polarization and propagation direction of o-ray E1 can be preset. Similarly, according to some embodiments, sub-coupler 302 can be configured to optimally couple with e-ray E2 based on the polarization and propagation direction of e-ray E2, wherein the polarization and propagation direction of e-ray E2 can be preset. For example, as Figure 4A As shown, the incident optical signal E in The incident angle can be close to the normal to the surface of the polarization-dependent beam splitter 401, and the optical axis 498 can be oriented at a certain angle in the yz plane. Thus, sub-coupler 301 can be configured to optimally couple with o-ray E1, which propagates along the z-direction and is polarized along the x-direction, while sub-coupler 302 can be configured to optimally couple with e-ray E2, which propagates along the z-direction and is polarized along the y-direction. The lateral spacing 399 between sub-couplers 301 and 302 can be determined by combining information about the lateral spacing 499 between o-ray E1 and e-ray E2.

[0159] According to other embodiments, sub-coupler 301 may not be configured to optimally couple with o-ray E1 based on the polarization of o-ray E1. That is, the optimal polarization for coupling with sub-coupler 301 may not be the same as the polarization of o-ray E1. Similarly, according to other embodiments, sub-coupler 302 may not be configured to optimally couple with e-ray E2 based on the polarization of e-ray E2. That is, the optimal polarization for coupling with sub-coupler 302 may not be the same as the polarization of e-ray E2. According to a further embodiment, sub-coupler 301 may not be configured to optimally couple with o-ray E1 based on the propagation direction of o-ray E1. Similarly, according to a further embodiment, sub-coupler 302 may not be configured to optimally couple with e-ray E2 based on the propagation direction of e-ray E2.

[0160] According to some embodiments, sub-coupler 301 may be a polarization-independent coupler and may be configured to optimally couple with o-ray E1 based solely on the propagation direction of o-ray E1. Similarly, according to some embodiments, sub-coupler 302 may be a polarization-independent coupler and may be configured to optimally couple with e-ray E2 based solely on the propagation direction of e-ray E2.

[0161] For example Figure 4B The optical signal transmission shown herein, wherein the optical signal E1 emitted from the sub-coupler 301 can be based on the polarization of the o-ray defined by the polarization-dependent beam splitter 401 (e.g., as shown in the figure). Figure 4B The linear polarization along the x-direction shown in the diagram is polarized, and the optical signal E2 emitted from the sub-coupler 302 can be polarized according to the polarization of the e-ray defined by the polarization-dependent beam splitter 410 (e.g., as shown in the diagram). Figure 4BThe optical signal is polarized (linearly polarized along the y-direction as shown). The propagation of the optical signal through the polarization-dependent beam splitter 401 is reversible. Therefore, after passing through the polarization-dependent beam splitter 401, the optical signals E1 and E2 can be combined to generate the outgoing optical signal E. out The emitted optical signal E out The optical path along the upper surface away from the polarization-dependent beam splitter 401 (e.g., as...) Figure 4B The path shown propagates with zero lateral displacement, continuing the path of optical signal E1, where optical signals E1 and E2 are coherent with each other, and the outgoing optical signal E... out The polarization is determined by the polarization, amplitude, and relative phase of the optical signals E1 and E2.

[0162] According to some embodiments, the optical signals E1 and E2 emitted and departing from the polarization-dependent beam splitter 401 may not completely overlap in space. This may result in the emitted optical signal E out Spatial polarization variation. According to some embodiments, the polarization-correlated beam splitter 401 and sub-couplers 301 and 302 can be configured such that the spatial overlap between optical signals E1 and E2 can produce an outgoing optical signal E with a dominant (i.e., greater than 50%) polarization state. out .

[0163] Polarization-dependent beam splitter 401 can be used together with coupler 300 to transmit and receive optical signals, wherein one of the sub-couplers 301 and 302 can be used to transmit the outgoing optical signal E. out The other sub-coupler in sub-couplers 301 and 302 can be used to receive the incident optical signal E. in Optical signal E out and E in It can propagate along the common optical path located between optical component 401 and the target. For example... Figure 4C As shown, on the one hand, the optical signal E1 emitted from the sub-coupler 301 can be polarized according to the polarization of the o-ray defined by the polarization-dependent beam splitter 401. After passing through the polarization-dependent beam splitter 401, the optical signal E1 can generate the emitted optical signal E. out Among them, optical signals E1 and E out The polarizations are the same. For example, if the optical signal E1 emitted from sub-coupler 301 is polarized along the o-ray polarization of polarization-dependent beam splitter 401 (i.e., linearly polarized along the x-direction), then the emitted optical signal E out It can exit and leave from the polarization-dependent beam splitter 401 with the same polarization as the optical signal E1 (i.e., along the x-direction), and along an optical path away from the polarization-dependent beam splitter 401 (e.g., as...). Figure 4CThe path shown is the path of the optical signal E1 that continues to propagate without lateral displacement.

[0164] On the other hand, according to some embodiments, the incident optical signal E in It can be polarized according to the polarization of the e-ray defined by the polarization-dependent beam splitter 401, and along the path of the emitted optical signal E. out The same optical path but propagating in opposite directions. After passing through the polarization-correlated beam splitter 401, the incident optical signal E... in An optical signal E2 can be generated that can be coupled to the sub-coupler 302, wherein the optical signal E in The polarization is the same as that of E2. For example, as... Figure 4C As shown, an incident optical signal E, linearly polarized along the y-direction, is incident in a direction perpendicular to the upper surface of the polarization-dependent beam splitter 401. in An optical signal E2, linearly polarized along the y-direction and coupled to sub-coupler 302, can be generated, wherein the optical signal E2 is laterally shifted by polarization-correlated beam splitter 401. For example... Figure 4C As shown, the emitted optical signal E out and incident optical signal E in The polarizations of the incident optical signals E1 and E2 are orthogonal to each other, and the polarizations of the optical signals E1 and E2 are perpendicular to each other. In one embodiment, when the incident optical signal E in The polarization and emitted optical signal E out When the polarizations are not orthogonal, the incident optical signal E in It can be split into o-ray and e-ray, where the o-ray can be coupled to sub-coupler 301, and the e-ray can be coupled to sub-coupler 302, such as... Figure 4A As shown in the embodiments.

[0165] In some embodiments, the functions of subcouplers 301 and 302 can be interchanged, so that the emitted optical signal can be e-ray E2 instead of o-ray E1, such as... Figure 4C As shown in the image.

[0166] like Figure 4C As shown, the coupled polarization base can be formed by the polarization of a pair of optical signals optimally coupled to sub-couplers 301 and 302. According to some embodiments, the coupled polarization base can be the same as the polarization of the o-ray and e-ray corresponding to the polarization-dependent beam splitter 401. According to other embodiments, the coupled polarization base can be different from the polarization of the o-ray and e-ray corresponding to the polarization-dependent beam splitter 401.

[0167] According to some embodiments, the difference between the polarization of the coupled polarization base and the polarization of the o-ray and e-ray corresponding to the polarization-dependent beam splitter 401 can be minimized through appropriate design of the optical coherent imager. Such appropriate design may include optical components (e.g., one or more lenses) to ensure that the incident and emitted optical signals propagate along directions close to normal incidence on the surface of the polarization-dependent beam splitter 401. Such appropriate design may also include optical components (e.g., one or more lenses) to ensure that the incident and emitted optical signals couple with subcouplers 301 and 302 at incident angles close to the optimal coupling directions of subcouplers 301 and 302.

[0168] refer to Figure 4C When the coupled polarization base may differ from the polarization of the o-ray and e-ray corresponding to the polarization-dependent beam splitter 401, the optical signal externally coupled to the coupler 300 can generate two outgoing optical signals from the polarization-dependent beam splitter 401, where the two outgoing optical signals correspond to the o-ray and e-ray, respectively. In this case, the optical signal E1 emitted by the sub-coupler 301 can generate a signal that is consistent with the outgoing optical signal E. out The same emitted o-ray and along the same path as the emitted optical signal E out The outgoing e-ray (not shown) propagates along different optical paths. For optical coherent imagers that use polarization diversity to achieve a shared path for transmitting and receiving optical signals, the outgoing e-ray can be ignored in this case because the input optical signal sharing the same optical path as the outgoing e-ray may not be coupled to the inner coupler 302, such as... Figure 4C As shown in the image.

[0169] According to some embodiments, Figure 4C One or both of the sub-couplers 301 and 302 in the design can be polarization-independent free space-to-waveguide couplers. Using polarization-independent free space-to-waveguide couplers allows for optimal coupling of the incident optical signal E. in It is independent of the polarization of the o-ray and e-ray corresponding to the polarization-dependent beam splitter 401.

[0170] In certain cases of optical coherent sensing, the optical signal reflected by the target has the same dominant polarization component as the optical signal illuminating the target. Such cases include, but are not limited to, specular reflection and light reflection from glossy target surfaces. To optimize the received signal, a polarization transformation mechanism may therefore be desirable to use with a coherent sensing unit that utilizes polarization diversity for external and internal coupling of the optical signal.

[0171] Figure 5AA perspective view of a polarization transformation configuration 510 implemented via the Faraday effect according to an embodiment of the present disclosure is shown. The polarization transformation configuration 510 is arranged for coupling optical signals internally and externally to coupler 101, and includes a Faraday rotator 501 and an optional polarization rotator 502. Figure 5B Show Figure 5A A top view of the polarization state of the optical signal in the image.

[0172] exist Figure 5A In this context, the Faraday rotator 501 is an optical component positioned between the target and the polarization diversity free space to the waveguide coupler 101. The Faraday rotator 501 can be configured to rotate a linearly polarized optical signal by an angle (e.g., 45 degrees). Figure 5A As shown, for example, coupler 101 can emit an optical signal E1 that is linearly polarized along the x-direction. Faraday rotator 501 can then rotate the polarization of the optical signal E1 by 45 degrees to generate an optical signal E2 that is linearly polarized along a direction at a 45-degree angle relative to the x-direction.

[0173] exist Figure 5A In this configuration, an optional polarization rotator 502 (referred to herein as a polarization rotator for simplicity) is positioned between the target and the Faraday rotator 501. Examples of the polarization rotator 502 may include, but are not limited to, a quartz rotator. Figure 5A In this configuration, the polarization rotator 502 can be configured to further rotate the polarization of the optical signal E2 by an angle. For example... Figure 5A As shown, for example, polarization rotator 502 rotates the polarization of an optical signal E2 that is linearly polarized along a direction at a 45-degree angle relative to the x-direction by 45 degrees to generate an optical signal E3 that is linearly polarized along the y-direction.

[0174] Polarization rotator 502 is a reciprocal optical component, meaning that the polarization rotation of polarization rotator 502 does not depend on the propagation direction of the optical signal. According to Figure 5A Polarization rotator 502 can rotate the polarization of the incident optical signal E4, which has the same linear polarization as E3, by an angle (e.g., 45 degrees) to produce an optical signal E5 with the same polarization as E2. In contrast, Faraday rotator 501 is a non-reciprocal optical component. Due to the anti-propagation direction of E5 relative to E2, Faraday rotator 501 can rotate the polarization of the optical signal E5 by an angle (e.g., 45 degrees) to produce a polarization along a direction orthogonal to the polarization of the optical signal E1 (i.e., according to...). Figure 5AThe optical signal E6 is linearly polarized in the y-direction. According to some embodiments, since the influence of the propagation path length of the optical signal within the Faraday rotator 501 and the magnetic field strength along the propagation path on the polarization rotation can compensate for each other, the angular rotation achieved by the Faraday rotator 501 is insensitive to the angle of incidence of the optical signal onto the Faraday rotator 501. The operating principle of the Faraday rotator is well known to those skilled in the art.

[0175] According to some embodiments, an optional polarization rotator 502 can be used to transform the polarization of E3 to one of the polarization basis components defined by coupler 101. As an example, Figure 5A The polarization base defined by coupler 101 is linearly polarized along the x and y directions. According to other embodiments, the optional polarization rotator 502 may be a quartz rotator, which, when used in conjunction with the Faraday rotator 501, can be used to achieve broadband polarization rotation. Conventional polarization rotators, such as quartz rotators, are sensitive to the incident angle of the incident optical signal. According to some embodiments, the polarization rotator 502 may be a polarization rotator capable of accepting incident optical signals with a large angular range while maintaining the desired phase shift. Examples of such wide-angle polarization rotators include, but are not limited to, artificial photonic structures designed using field transformation methods, as described in "A Wide-angle Multi-Octave Broadband Waveplate Based on Field Transformation Approach," Scientific Reports, 5, 17532 (2015), p. 17532.

[0176] According to some embodiments, the components of the polarization transformation configuration 510 can be manifested as separate components, such as... Figure 5A As shown in the diagram. According to other embodiments, some or all of the components in the polarization transformation configuration 510 may be represented as a single combined component. Furthermore, according to some embodiments, the polarization transformation configuration 510 may be an optical component separate from the PIC chip including the polarization diversity free space to waveguide coupler 101, such as… Figure 5A As shown in the diagram. According to other embodiments, some or all components of the polarization transformation configuration 510 may be attached to the surface of the PIC chip including coupler 101. According to a further embodiment, some or all components of the polarization transformation configuration 510 may be within or part of the PIC chip including coupler 101.

[0177] exist Figure 5AFor illustrative purposes, the propagation paths of the internally coupled optical signals E1, E2, and E3, and the propagation paths of the externally coupled optical signals E4, E5, and E6 are clearly plotted. Typically, the propagation paths of the internally coupled and externally coupled signals can be spatially different or spatially identical. Furthermore, in... Figure 5A For illustrative purposes, optical signals E1, E2, E3, E4, E5, and E6 are depicted as propagating along the z-direction and incident normally at coupler 101, Faraday rotator 501, and polarization rotator 502. Typically, the propagation direction of the optical signals can be incident normally relative to these components, or at an angle of incidence different from normal incidence.

[0178] Figure 5C A side view is shown of a polarization transformation separation configuration used with coupler 300 according to an embodiment of the present disclosure, wherein, Figure 5A The polarization transformation configuration 510 and Figure 4C The polarization separation configuration is combined. For example... Figure 5C As shown, the polarization-dependent beam splitter 401 is disposed between the coupler 300 (including sub-couplers 301 and 302) and the polarization transformation configuration 510 (including Faraday rotator 501 and polarization rotator 502). Figure 5C The polarization-dependent beam splitter 401 can be used to enable optical signals coupled to sub-couplers 301 and 302 to propagate along a common optical path, wherein the common optical path is located between the polarization-dependent beam splitter 401 and the target. For example, as... Figure 5C As shown, sub-coupler 301 can output optical signal E1 into free space, wherein E1 is along the direction defined by sub-coupler 301 (e.g., Figure 5C Linear polarization (in the x-direction). According to Figure 5C And refer to Figure 4C and Figure 5A On one hand, optical signal E1 can generate optical signal E3, which is linearly polarized along a direction orthogonal to E1 (e.g., the y-direction). On the other hand, incident optical signal E4, which has the same polarization as E3 and propagates along the same optical path as the outgoing optical signal E3 but in the opposite direction, can generate optical signal E6, which is linearly polarized along a direction orthogonal to the polarization of E1 (i.e., the y-direction) and spatially separated from the path of E1, through polarization rotator 502, Faraday rotator 501, and polarization-dependent beam splitter 401, such that optical signal E6 can be coupled to sub-coupler 302.

[0179] According to some embodiments, the components of polarization transformation configuration 510 and polarization-dependent beam splitter 401 can be implemented as separate components, such as... Figure 5CAs shown in the diagram. According to other embodiments, some or all of the components in the polarization transformation configuration 510 and the polarization-dependent beamsplitter 401 may be represented as a single combined component. Furthermore, according to some embodiments, the polarization transformation configuration 510 and the polarization-dependent beamsplitter 401 may be optical components separate from the PIC chip including the polarization diversity free space-to-waveguide coupler 300, such as… Figure 5C As shown in the diagram. According to other embodiments, some or all components of the polarization transformation configuration 510 and the polarization-dependent beam splitter 401 may be attached to the surface of the PIC chip including the coupler 300. According to a further embodiment, some or all components of the polarization transformation configuration 510 and the polarization-dependent beam splitter 401 may be within or part of the PIC chip including the coupler 300.

[0180] exist Figure 5C For illustrative purposes, optical signals E1, E3, E4, and E6 are depicted as propagating along the z-direction and incident normally at coupler 300, polarization-dependent beam splitter 401, Faraday rotator 501, and polarization rotator 502. Typically, the propagation direction of the optical signals can be incident normally relative to these components, or at an angle of incidence different from normal incidence.

[0181] Figure 6A A perspective view showing a polarization transformation configuration implemented by a quarter-wave plate 601 according to another embodiment of the present disclosure. In this embodiment, polarization transformation is achieved by the phase delay of the quarter-wave plate. Figure 6A In this context, the quarter-wave plate 601 is an optical component disposed between the target and the polarization diversity free space to the waveguide coupler 101. The quarter-wave plate 601 can be configured to transform a linearly polarized optical signal into a circularly polarized optical signal through appropriate orientation of its optical axis. For example, as... Figure 6A As shown, the quarter-wave plate 601 can transform the optical signal E1, which is linearly polarized along the x-direction, into the optical signal E2, which is circularly polarized to the right relative to the propagation direction (positive z-direction) of E2. Figure 6B Show Figure 6A A top view of the polarization state of the optical signal in the image.

[0182] like Figure 6A As shown, optical signal E3 has a circular polarization in the same direction as E2, but propagates in the opposite direction to E2 (i.e., E2 and E3 actually have opposite cycloid polarization). A quarter-wave plate 601 can be used to transform optical signal E3 to produce optical signal E4 that is linearly polarized along a direction orthogonal to the polarization of E1. For example, as... Figure 6AAs shown, the quarter-wave plate 601 transforms the optical signal E3, which is circularly polarized to the left relative to the propagation direction (negative z-direction), into an optical signal E4, which is linearly polarized along the y-direction.

[0183] According to some embodiments, the quarter-wave plate 601 may be a component separate from the PIC chip, including the polarization diversity free space-to-waveguide coupler 101, such as... Figure 6A As shown in the diagram. According to other embodiments, the quarter-wave plate 601 may be attached to the surface of the PIC chip including the coupler 101. According to a further embodiment, the quarter-wave plate 601 may be within the PIC chip including the coupler 101 or a portion thereof.

[0184] exist Figure 6A For illustrative purposes, the propagation paths of the internally coupled optical signals E1 and E2, and the externally coupled optical signals E3 and E4, are clearly plotted. Typically, the propagation paths of the internally coupled and externally coupled signals can be spatially different or spatially identical. Furthermore, in... Figure 6A For illustrative purposes, optical signals E1, E2, E3, and E4 are depicted as propagating along the z-direction and incident normally on coupler 101 and quarter-wave plate 601. Typically, the propagation direction of the optical signals can be incident normally relative to these components or at an angle of incidence different from normal incidence.

[0185] Figure 6C A side view is shown of a polarization transformation separation configuration for use with coupler 300 according to another embodiment of the present disclosure, wherein, Figure 6A Polarization transformation configuration and Figure 4C The polarization separation configuration is combined. For example... Figure 6C As shown, the polarization-dependent beam splitter 401 is disposed between the coupler 300 (including sub-couplers 301 and 302) and the quarter-wave plate 601. Figure 6C The polarization-dependent beam splitter 401 can be used to enable optical signals coupled to sub-couplers 301 and 302 to propagate along a common optical path, wherein the common optical path is located between the polarization-dependent beam splitter 401 and the target. For example, as... Figure 6C As shown, sub-coupler 301 can output optical signal E1 into free space, wherein E1 is along a direction defined by the design of sub-coupler 301 (e.g., Figure 6C Linear polarization (in the x-direction). According to Figure 6C And refer to Figure 4C and Figure 6AOn one hand, the optical signal E1 can generate an optical signal E2 that is circularly polarized to the right relative to the polarization direction of E2 (e.g., along the positive z-direction). On the other hand, the incident optical signal E3 has a circular polarization in the same direction of polarization rotation as E2, and propagates along the same optical path as the outgoing optical signal E2 but in the opposite direction (i.e., E3 is circularly polarized to the left relative to its propagation direction). The incident optical signal E3, through the quarter-wave plate 601 and the polarization-correlated beam splitter 401, can generate an optical signal E2 that is circularly polarized to the right relative to the polarization direction of E1 (i.e., ...). Figure 6C The optical signal E4 is linearly polarized in the y-direction and spatially separated from the path of E1, so that the optical signal E4 can be coupled to the sub-coupler 302.

[0186] According to some embodiments, the quarter-wave plate 601 and the polarization-dependent beam splitter 401 can be implemented as separate components, such as... Figure 6C As shown in the diagram. According to other embodiments, the quarter-wave plate 601 and the polarization-dependent beamsplitter 401 can be presented as a single combined component. Furthermore, according to some embodiments, the quarter-wave plate 601 and the polarization-dependent beamsplitter 401 can be optical components separate from the PIC chip including the polarization diversity free space-to-waveguide coupler 300, such as… Figure 6C As shown in the diagram. According to other embodiments, one or both of the quarter-wave plate 601 and the polarization-dependent beam splitter 401 may be attached to the surface of the PIC chip including the coupler 300. According to a further embodiment, one or both of the quarter-wave plate 601 and the polarization-dependent beam splitter 401 may be within or part of the PIC chip including the coupler 300.

[0187] exist Figure 6C For illustrative purposes, optical signals E1, E2, E3, and E4 are depicted as propagating along the z-direction and incident normally on coupler 300, polarization-dependent beam splitter 401, and quarter-wave plate 601. Typically, the propagation direction of the optical signals can be incident normally relative to these components or at an angle of incidence different from normal incidence.

[0188] In some applications of optical coherent sensing, a target may reflect or scatter the optical signal illuminating the target, causing the returned optical signal to be polarized with a polarization substantially different from that of the illuminating optical signal. To optimize the received signal, it is desirable for the coherent sensing unit to be able to detect the incident optical signal having any polarization state.

[0189] Figure 7A A plan view of a coherent sensing unit 700 for transmitting and receiving optical signals based on polarization diversity, according to another embodiment of the present disclosure, is shown. Figure 7A The coherent sensing unit 700 in the middle is similar to Figure 1AThe coherent sensing unit 100 in the middle. According to Figure 1A In an embodiment of the coherent sensing unit 100, the main difference between the coherent sensing unit 700 and the coherent sensing unit 100 is that the coherent sensing unit 700 can also process the incident optical signal E coupled by the coupler 101 and guided to the waveguide 121. in The amount.

[0190] More specifically, see reference Figure 7A The light source signal E is transmitted through waveguide 731. S Provided to the coherent sensing unit 700, and the local oscillator (LO)E is connected via waveguide 734. LO Provided to the coherent sensing unit 700. Figure 7A In this context, component 705 is a 2×2 optical coupler. Since there is no signal input from waveguide 733, the 2×2 optical coupler 705 can be used as a split coupler, which splits the light source signal E from waveguide 731. S Split and E S A portion of it, as an optical signal E1, is guided through waveguide 721 to the polarization diversity free space and then to waveguide coupler 701. S A portion can also be transmitted to waveguide 732. E transmitted to waveguide 732 S Part of it can be used for other purposes (e.g., such as...) Figure 7B (as in the coherent sensing unit 710), or it can simply be considered as a loss. In the latter case, E transmitted to waveguide 732 S The portion may need to be appropriately attenuated to avoid any back reflection. E is transmitted to waveguides 721 and 732 respectively. S The specific factor depends on the splitting ratio and loss of the 2×2 optical coupler 705. According to some embodiments, the 2×2 optical coupler 705 can be a 50 / 50 2×2 optical coupler. According to other embodiments, the 2×2 optical coupler 705 can have a splitting ratio other than 50 / 50.

[0191] exist Figure 7A In the diagram, the polarization diversity free space to waveguide coupler 701 (referred to as coupler 701 in this paper for simplicity) is similar to... Figure 1A The coupler 101 of the coherent sensing unit 100 in the middle serves as both a transmitter and a receiver. It is a dual waveguide coupler connected to waveguides 721 and 722.

[0192] As a transmitter, reference Figure 7A Coupler 701 can couple the optical signal E1 from waveguide 721 into free space as the output optical signal E. out It can be used for target illumination in optical coherent imagers. The output optical signal E from coupler 701 is...out Propagates in directions outside the xy plane (i.e., E) out The propagation direction has a non-zero z component, and is polarized by the polarization defined by the design of coupler 701.

[0193] As a receiver, reference Figure 7A Coupler 701 can convert the incident optical signal E in It is coupled to the coherent sensing unit 700. The incident optical signal E coupled by the coupler 701 in It can be guided to one or both of waveguides 721 and 722, depending on the incident optical signal E. in The polarization state. The incident optical signal E coupled to waveguides 721 and 722. in The polarization component depends on the design of coupler 701. According to some embodiments, it is related to the emitted optical signal E. out Orthogonally polarized incident optical signal E in The polarization component can be guided to waveguide 722 as an internally coupled optical signal E2, and is coupled with the incident optical signal E2 guided to waveguide 722. in The incident optical signal E with orthogonal polarization components in The polarization component can be guided to waveguide 721 as an internally coupled optical signal E3. The internally coupled optical signal E3 propagates in the opposite direction to the propagation direction of the optical signal E1. Since there is no signal input from waveguide 732, the 2×2 optical coupler 705 can be used as a split coupler, which splits the internally coupled optical signal E3 from waveguide 721 and guides a portion of E3 as an optical signal E4 through waveguide 733 to the 2×2 optical coupler 712. A portion of E3 can also be passed to waveguide 731 and, in conjunction with the light source signal E1, propagates to the optical signal E21. S The propagation direction is opposite to that of the waveguide 731. According to some embodiments, the E3 component in waveguide 731 can be left unattended without affecting other parts of the PIC chip, including the sensing unit 700. The portions of E3 transmitted to waveguides 731 and 733 respectively depend on the splitting ratio and loss of the 2×2 optical coupler 705.

[0194] exist Figure 7A Although coupler 701 is depicted as a single entity, it typically includes a single photonic component or multiple photonic components. According to some embodiments, similar to... Figure 1A and Figure 1B The coupler 101 shown, and coupler 701, can be implemented via a polarization-splitter free space to waveguide coupler. According to other embodiments, coupler 701 can be... Figure 2Coupler 200 is implemented in the form of waveguides 221 and 222, which may be identical to waveguides 721 and 722 (i.e., waveguide 721 is waveguide 221 and waveguide 722 is waveguide 222, or waveguide 721 is waveguide 222 and waveguide 722 is waveguide 221). According to a further embodiment, coupler 701 may be implemented by... Figure 3 Coupler 300 is used to implement waveguides 721 and 722, wherein waveguides 321 and 322 can be the same as waveguides 721 and 722 (i.e., waveguide 721 is waveguide 321 and waveguide 722 is waveguide 322, or waveguide 721 is waveguide 322 and waveguide 722 is waveguide 321). According to a further embodiment, coupler 701 is implemented by coupler 300. Figure 4C The polarization-correlated beam splitter 401 can be used with the coherent sensing unit 700 to enable the emitted optical signal E out and incident optical signal E in It can propagate along a common optical path, which is located between the polarization-dependent beamsplitter 401 and the target. According to some embodiments, it is similar to... Figure 1A and Figure 1B Coupler 101 and coupler 701 may also include any of the TE-TM mode converters, splitters and combiners.

[0195] Furthermore, according to some embodiments, Figure 5A and Figure 5C The Faraday rotator 501 and optional polarization rotator 502 shown can be used with coupler 701 to rotate the polarization of the outgoing and incoming optical signals. According to some embodiments, Figure 6A and Figure 6C The quarter-wave plate 601 shown can be used with the coupler 701 to transform the emitted optical signal into a linearly polarized, circularly polarized, or elliptically polarized optical signal according to the polarization of the emitted optical signal.

[0196] exist Figure 7A In the middle, component 706 is a shunt coupler, which connects the L from waveguide 734. O Split the path and connect L O A portion is guided to waveguide 723 as a LO E LO,1 And guide a portion of the LO to waveguide 735 as LO E LO,2 The portions of the LO transmitted to waveguides 723 and 735, respectively, depend on the split ratio and loss of the splitter coupler 706. According to some embodiments, the splitter coupler 706 may be a 50 / 50 splitter coupler. According to other embodiments, the splitter coupler 706 may have a split ratio other than 50 / 50.

[0197] exist Figure 7AIn this configuration, component 702 is a 2×2 optical coupler that mixes the internally coupled optical signal E2 from waveguide 722 and the LO signal E from waveguide 723. LO,1 The mixed signal is then split and directed to waveguides 724 and 725. According to some embodiments, the 2×2 optical coupler 702 may be similar to the 2×2 optical coupler 102 of the coherent sensing unit 100 in FIG1.

[0198] exist Figure 7A In this context, component 703 is a square-law photodetector that receives and detects optical signals from waveguide 724. Similarly, in... Figure 7A In this context, component 704 is a square-law photodetector that receives and detects optical signals from waveguide 725. According to some embodiments, photodetectors 703 and 704 may be similar to photodetectors 103 and 104 of the coherent sensing unit 100 in FIG1.

[0199] According to some embodiments, photodetectors 703 and 704 can be connected to an output electronic circuit that includes electronic components, such as, but not limited to, any one or more of a transimpedance amplifier (TIA), transistor, diode, resistor, capacitor, and electrical switch for processing the electrical output of photodetectors 703 and 704. This output electronic circuit... Figure 7A Not shown in the image.

[0200] exist Figure 7A In this configuration, component 712 is a 2×2 optical coupler that mixes the internally coupled signal E4 from waveguide 733 and the LO E from waveguide 735. LO,2 Furthermore, the mixed signal is split and directed to waveguides 736 and 737.

[0201] exist Figure 7A In this context, component 713 is a square-law photodetector that receives and detects optical signals from waveguide 736. Similarly, in... Figure 7A In this embodiment, component 714 is a square-law photodetector that receives and detects optical signals from waveguide 737. According to some embodiments, photodetectors 713 and 714 may be similar to photodetectors 703 and 704.

[0202] According to some embodiments, photodetectors 713 and 714 can be connected to an output electronic circuit that includes electronic components, such as, but not limited to, any one or more of a transimpedance amplifier (TIA), transistor, diode, resistor, capacitor, and electrical switch for processing the electrical output of photodetectors 713 and 714. This output electronic circuit... Figure 7ANot shown. According to some embodiments, the output electronic circuitry connected to photodetectors 713 and 714 can form a single electronic circuit with the output electronic circuitry connected to photodetectors 703 and 704. According to other embodiments, the output electronic circuitry connected to photodetectors 713 and 714 can be separate from the output electronic circuitry connected to photodetectors 703 and 704.

[0203] According to some embodiments, the coherent sensing unit 700 may include components not explicitly shown, including but not limited to any one or more electro-optical components and thermo-optical components, for any one or more of phase, amplitude, frequency, wavelength and time control.

[0204] Figure 7B A plan view of a coherent sensing unit 710 for transmitting and receiving optical signals based on polarization diversity, according to yet another embodiment of the present disclosure, is shown. Figure 7B The coherent sensing unit 710 in the middle is similar to Figure 7A The coherent sensing unit 700 is described above. The main difference between coherent sensing unit 700 and coherent sensing unit 710 is that in coherent sensing unit 710, waveguide 734 is connected to waveguide 732, enabling LO E... LO The light source signal E transmitted to waveguide 732 S Part of it.

[0205] Figure 8 A plan view of a coherent sensing unit 800 for transmitting and receiving optical signals based on polarization diversity, according to another embodiment of the present disclosure, is shown. Figure 8 The coherent sensing unit 800 in the middle is similar to Figure 7A The coherent sensing unit 700 is described in the coherent sensing unit 800. The main difference between the coherent sensing unit 800 and the coherent sensing unit 700 is that the coherent sensing unit 800 uses an optical circulator 805 instead of the 2×2 optical coupler 705 in the coherent sensing unit 700 to guide the flow of optical signals. Examples of the optical circulator 805 may include, but are not limited to, optical circulators based on heterogeneous Ce:YIG / silicon waveguides in a Mach-Zehnder interferometer (MZI) configuration as described in "Broadband TE Optical Isolators and Circulators in Silicon Photonics Through Ce:YIG Bonding," Journal of Lightwave Technology, Vol. 37, No. 5, p. 1463 (2019)).

[0206] according to Figure 8 In the embodiment described, optical circulator 805 is a three-port optical circulator that routes optical signals in a circumferential direction. More specifically, optical circulator 805 can route optical signals in a clockwise direction: optical signals input from waveguide 731 are guided to waveguide 721, optical signals input from waveguide 721 are guided to waveguide 733, and optical signals input from waveguide 733 are guided to waveguide 731.

[0207] exist Figure 8 In the middle, the optical circulator 805 is coupled to waveguides 721, 731, and 733. Then it can be... Figure 8 The waveguide 732 of the coherent sensing unit 700 in Figure 7 is omitted. The optical circulator 805 can route the light source signal E in the waveguide 731. S An optical signal E1 is generated in waveguide 721. The inner-coupled optical signal E3 received by coupler 701 can be guided through waveguide 721 to optical circulator 805, whereby optical circulator 805 can route the inner-coupled optical signal E3 to waveguide 733 to generate optical signal E4.

[0208] According to some embodiments, a four-port optical circulator, such as a four-port optical circulator implemented based on a four-port MZI, can be used instead of the three-port optical circulator used for optical circulator 805, and the waveguide 732 of the coherent sensing unit 700 in FIG7 can be retained in Figure 8 In the coherent sensing unit 800, a four-port optical circulator can be coupled to waveguides 721, 731, 732, and 733, wherein the four-port optical circulator routes optical signals from waveguide 731 to waveguide 721, from waveguide 721 to waveguide 733, from waveguide 733 to waveguide 732, and from waveguide 732 to waveguide 731.

[0209] exist Figure 8 In the coherent sensing unit 800, an optical circulator 805 is used instead of the 2×2 optical coupler 705 in the coherent sensing unit 700. Ideally, this can prevent the light source signal E from being transmitted to the waveguide 732. S The advantages of some of the losses are lost. Nevertheless, the insertion loss (>10dB) of the most advanced on-chip optical circulators may still be too high to exert an advantage over the use of 2×2 optical couplers 705 in the configuration of the coherent sensing unit 700.

[0210] Figure 9A plan view of a coherent sensing unit 900 for transmitting and receiving optical signals based on polarization diversity, according to yet another embodiment of this disclosure, is shown. The coherent sensing unit 900 is similar to coherent sensing units 700, 710, and 800, which detect incident optical signals having any polarization state. The main difference between the coherent sensing unit 900 and the coherent sensing units 100, 700, 710, and 800 is that the coherent sensing unit 900 includes a polarization diversity free space-to-waveguide coupler that guides an internally coupled optical signal having any polarization state to a waveguide different from the waveguide carrying the outgoing optical signal.

[0211] More specifically, see reference Figure 9 The light source signal E is transmitted through waveguide 921. S Provided to the coherent sensing unit 900, and the local oscillator (LO)E is connected via waveguide 934. LO Provided to the coherent sensing unit 900.

[0212] exist Figure 9 In this context, the polarization diversity free space to waveguide coupler 901 (referred to as coupler 901 for simplicity) is a three-waveguide coupler connected to waveguides 921, 922, and 933. Coupler 901 can be used as both a transmitter and a receiver.

[0213] As a transmitter, reference Figure 9 Coupler 901 can couple the outgoing optical signal E1 from waveguide 921 (which is essentially the same as the light source signal E1). S (Same) as the emitted optical signal E out Coupled into free space, the emitted optical signal E out It can be used for target illumination in optical coherent imagers. The output optical signal E from coupler 901 out Propagates in directions outside the xy plane (i.e., E) out The propagation direction has a non-zero z component, and the polarization state is defined by the design of coupler 901.

[0214] As a receiver, coupler 901 can convert the incident optical signal E in It is coupled to the coherent sensing unit 900. The incident optical signal E coupled by the coupler 901 in It can be guided to one or both of waveguides 922 and 933, depending on the incident optical signal E. in The polarization state. The incident optical signal E coupled to waveguides 922 and 933. in The polarization component depends on the design of coupler 901. According to some embodiments, it is related to the emitted optical signal E. out Orthogonally polarized incident optical signal E inThe polarization component can be guided to waveguide 922 as an internally coupled optical signal E2, and is coupled with the incident optical signal E2 guided to waveguide 922. in The incident optical signal E with orthogonal polarization components in The polarization component can be guided to waveguide 933 as an internally coupled optical signal E3.

[0215] exist Figure 9 Although coupler 901 is depicted as a single entity, it typically includes a single photonic component or multiple photonic components. Embodiments of coupler 901 are described in further detail below. Figure 10A , Figure 11A and Figure 13A As shown in the figure. According to some embodiments, similar to Figure 1A and Figure 1B Coupler 101 and coupler 901 may also include any of the TE-TM mode converters, splitters and combiners.

[0216] exist Figure 9 In the middle, shunting coupler 906 pairs the LO E from waveguide 934. LO Split the circuit and use a portion of the LO as LO E. LO,1 Guided to waveguide 923, and using a portion of the LO as LO E LO,2 The signal is guided to waveguide 935. The portions of the LO transmitted to waveguides 923 and 935, respectively, depend on the splitting ratio and loss of splitter coupler 906. According to some embodiments, splitter coupler 906 may be a 50 / 50 splitter coupler. According to other embodiments, splitter coupler 906 may have a splitting ratio other than 50 / 50.

[0217] exist Figure 9 In this configuration, component 902 is a 2×2 optical coupler that mixes the internally coupled optical signal E2 from waveguide 922 and the LO E from waveguide 923. LO,1 The mixed signal is then split and directed to waveguides 924 and 925. According to some embodiments, the 2×2 optical coupler 902 can be similar to... Figure 7A The coherent sensing unit 700 contains a 2×2 optical coupler 702.

[0218] exist Figure 9 In this context, component 903 is a square-law photodetector that receives and detects optical signals from waveguide 924. Similarly, in... Figure 9 In this context, component 904 is a square-law photodetector that receives and detects optical signals from waveguide 925. According to some embodiments, photodetectors 903 and 904 can be similar to... Figure 7A The photodetectors 703 and 704 of the coherent sensing unit 700 in the middle.

[0219] exist Figure 9 In, similar to Figure 7A The coherent sensing unit 700 contains a 2×2 optical coupler 712, which is a 2×2 optical coupler that mixes the internally coupled optical signal E3 from waveguide 933 and the LO E from waveguide 935. LO,2 The mixed signal is then split and directed to waveguides 936 and 937.

[0220] exist Figure 9 In this context, component 913 is a square-law photodetector that receives and detects optical signals from waveguide 936. Similarly, in... Figure 9 In this context, component 914 is a square-law photodetector that receives and detects optical signals from waveguide 937. According to some embodiments, photodetectors 913 and 914 can be similar to... Figure 7A The photodetectors 713 and 714 in the coherent sensing unit 700.

[0221] Figure 10A A top view of a three-waveguide polarization diversity free-space to waveguide coupler 1000 according to an embodiment of the present disclosure is shown. Figure 10B Show Figure 10A A perspective view of the coupler 1000 shown. Figure 10B Additionally, the polarized outgoing optical signal and incoming optical signal E coupled to subcouplers 1001 and 1002 are shown. 10 E 23 and E 33 .like Figure 10A As shown by the dashed lines, coupler 1000 includes two sub-couplers 1001 and 1002. According to some embodiments, sub-coupler 1001 can be configured as follows: Figure 1B The polarization diversity free space to waveguide coupler 101 shown is as follows: Figure 2 The polarization diversity free space to waveguide coupler 200 shown is implemented, while the sub-coupler 1002 can be implemented by a free space to waveguide coupler coupled to a single waveguide, including but not limited to grating couplers. According to other embodiments, the sub-coupler 1002 can be implemented by a polarization-independent free space to waveguide coupler.

[0222] Reference Figure 10A On one hand, waveguide 921 is connected to sub-coupler 1001 as an external coupling waveguide, and waveguide 922 is connected to sub-coupler 1001 as a first internal coupling waveguide. On the other hand, waveguide 933 is connected to sub-coupler 1002 as a second internal coupling waveguide. Here, waveguides 921, 922, and 933 are connected to... Figure 9 The waveguides 921, 922 and 933 in the coherent sensing unit 900 shown are the same.

[0223] like Figure 10A and Figure 10B As shown, a primary function of the sub-coupler 1001 is to couple optical signals used for target illumination to the outside of the transmitter. The optical signal E1 in the waveguide 921 can be coupled externally into free space via the sub-coupler 1001 as the emitted optical signal E. 10 Similar to Figure 1B Coupler 101 in the middle emits optical signal E 10 Polarized according to the design of sub-coupler 1001. For example, as Figure 10B As shown in, the optical signal E 10 It is linearly polarized along the x-direction.

[0224] like Figure 10A and Figure 10B As shown, another primary function of the sub-coupler 1001 is to act as a receiver to couple the incident optical signal into the coherent sensing unit 900, wherein the polarization state of the incident optical signal is orthogonal to the polarization of the emitted optical signal. This has a polarization state similar to that of the emitted optical signal E. 10 Orthogonally polarized incident optical signal E 23 Internal coupling is achieved by sub-coupler 1001 to generate an internally coupled optical signal E2 in waveguide 922. Similar to coupler 101 in Figure 1, the incident optical signal E2 is optimally internally coupled by sub-coupler 1001. 23 The polarization is determined based on the design of the sub-coupler 1001. For example, as... Figure 10B As shown, the optimally coupled optical signal E 23 Linear polarization along the y-direction.

[0225] like Figure 10A and Figure 10B As shown, the primary function of sub-coupler 1002 is to act as a receiver to couple the incident optical signal into the coherent sensing unit 900, wherein the polarization state of the incident optical signal is orthogonal to the polarization of the incident optical signal coupled to the waveguide 922 by sub-coupler 1001. It has a polarization state similar to that of the optical signal E. 23 The incident optical signal E with orthogonal polarization 33 Internal coupling is achieved by sub-coupler 1002 to generate an internally coupled optical signal E3 in waveguide 933. Similar to sub-coupler 1001, the incident optical signal E3 is optimally internally coupled by sub-coupler 1002. 33 The polarization is determined based on the design of the sub-coupler 1002. For example, as... Figure 10B As shown, the optimally coupled optical signal E 33 Linear polarization along the x-direction, which is consistent with the emitted optical signal E 10 They have the same polarization.

[0226] Figure 10C A side view of a polarization transformation separation configuration 1010 according to an embodiment of the present disclosure is shown. This polarization transformation separation configuration is used in conjunction with a three-waveguide polarization diversity free space to waveguide coupler for external coupling of optical signals. Figure 10D This illustrates the use of internally coupled optical signals. Figure 10C The side view of configuration 1010 shown. Polarization transformation separation configuration 1010 causes the incident optical signal E reaching coupler 1000 to... 23 and E 33 and the emitted optical signal E emitted by coupler 1000 10 It can propagate along a common optical path, which is located between configuration 1010 and the target. The polarization transformation separation configuration 1010 includes a Faraday rotator 1051, an optional polarization rotator 1052, and a polarization-dependent beam splitter 1041, such as... Figure 10C and Figure 10D As shown. For illustrative purposes, Figure 10E Show Figure 10C A top view of the polarization state of the optical signal. Similarly, Figure 10F Show Figure 10D A top view of the polarization state of the optical signal in the image.

[0227] For optical signal transmission, such as Figure 10B and Figure 10C As shown, sub-coupler 1001 of coupler 1000 can externally couple the optical signal E1 from waveguide 921 to generate optical signal E. 10 Optical signal E 10 According to the design of sub-coupler 1001, it is linearly polarized (e.g., linearly polarized along the x-direction) and propagates out of sub-coupler 1001 (e.g., towards the positive z-direction) into free space. Figure 10C and Figure 10E As shown, the Faraday rotator 1051 can convert the optical signal E 10 The polarization is rotated by an angle (e.g., 45 degrees) to generate the optical signal E. 11 (For example, E) 11 Linear polarization along a direction at a 45-degree angle relative to the x-direction. Similar to... Figure 5C The optional polarization rotator 1052 of the polarization rotator 502 in the middle can further polarize E 11 The polarization is rotated by an angle (e.g., 45 degrees) to generate the optical signal E. 12 (For example, E) 12 Linear polarization along the y-direction). Similar to... Figure 4C The polarization-dependent beamsplitter 1041 of the polarization-dependent beamsplitter 401 can be configured such that the optical signal E passes through the polarization-dependent beamsplitter 1041. 12(Based on the configuration of the polarization-dependent beam splitter 1041, which can be represented as o-ray) it can produce light along the desired optical path (e.g., along the path with E). 12 Optical signal E propagating along the same optical path without lateral displacement 13 According to some embodiments, the optical signal E 13 It can be used with E 12 The same polarization (i.e., linear polarization along the y-direction). Optical signal E 13 Then it can be used for target illumination. Similar to... Figure 5A and Figure 5C In some embodiments, the polarization rotator 502, optionally polarization rotator 1052, may function to enable the optical signal for target illumination emitted from polarization-dependent beam splitter 1041 to travel in the same direction as one of the polarization basis components defined by coupler 1000 (e.g., according to...). Figure 10C The optical signal E in the embodiment 10 (Polarization orthogonal) polarization.

[0228] According to some embodiments, the optional polarization rotator 1052 in the polarization transformation separation configuration 1010 can be omitted, resulting in a polarization rotator that is consistent with the optical signal E. 11 The emitted optical signal with the same polarization state can be used for target illumination. In such a case, it may be necessary to configure a polarization-dependent beam splitter 1041, for example, by adjusting the output optical signal E. 11 The polarization direction is aligned with the optical axis of the polarization-correlated beam splitter 1041 so that the optical signal E 11 It can be used as propagation along the expected optical path (e.g., continuing E without lateral displacement). 11 A single optical signal (the path of the polarization-dependent beamsplitter) is emitted from the polarization-dependent beamsplitter 1041. According to some embodiments, the polarization-dependent beamsplitter 1041 can be configured relative to the sub-coupler 1001 such that, depending on the configuration of the polarization-dependent beamsplitter 1041, the optical signal E... 11 It can be represented as o-ray.

[0229] For optical signal reception, from the target, along with... Figure 10C Optical signal E in 13 Incident optical signals propagating along the same but opposite light paths may include one or both of the two incident optical signal components, whose polarization is related to... Figure 10D The incident optical signal E shown 20 and E 30 The polarizations are the same, where the optical signal E 20 Along with optical signal E 13 The polarizations are linearly polarized in the same direction, and the optical signal E 30 Along with optical signal E 20The polarization is orthogonal to the linear polarization direction. For example, such as... Figure 10D As shown, E 20 Linear polarization along the y-direction, E 30 Linear polarization along the x-direction.

[0230] refer to Figure 10D and Figure 10F Incident optical signal E 20 A polarization-dependent beam splitter 1041 can be used to generate beams with polarization correlation. Figure 10C E in 12 Optical signals E with the same polarization (i.e., linearly polarized along the y-direction) 21 Among them, optical signal E 21 This can be represented as the o-ray relative to the polarization-dependent beam splitter 1041. Given optical propagation reciprocity, the polarization rotator 1052 can then convert the E... 21 The polarization is rotated by an angle (e.g., 45 degrees) to produce a polarization along the same direction as the polarization. Figure 10C Optical signal E in 11 Optical signals E with linear polarization in the same direction as the polarization 22 However, due to the optical signal E 22 The propagation direction and optical signal E 11 The propagation directions are opposite, therefore the Faraday rotator 1051, which violates the reciprocity of optical propagation, can convert the optical signal E... 22 The polarization is rotated by an angle (e.g., 45 degrees) to produce a polarization signal E with the same polarization as the optical signal E. 10 The optical signal E with orthogonal linear polarization (i.e., along the y-direction) 23 Optical signal E 23 It can then be internally coupled via sub-coupler 1001 to generate an internally coupled optical signal E2 that is guided to waveguide 922, such as Figure 10B As shown in the image.

[0231] refer to Figure 10D and Figure 10F Due to the optical signal E 30 Along with E 20 The polarization is linearly polarized in orthogonal directions, and the optical signal E is obtained through a polarization-correlated beam splitter 1041. 30 It can generate optical signal E 31 The optical signal E 31 Along with optical signal E 21 The light paths propagate in different spatial directions, and with respect to E. 21 Polarization is determined by orthogonal polarization. According to... Figure 10D In the embodiment described, the incident optical signal E 31 Linearly polarized along the x-direction, and along the direction of the optical signal E 21Light propagation in the same direction, but laterally shifted towards the negative x-direction. For example... Figure 10D As shown in, the optical signal E 31 This can be represented as an e-ray with respect to the polarization-dependent beam splitter 1041. The polarization rotator 1052 can then convert the e-ray... 31 The polarization is rotated by an angle (e.g., 45 degrees) to produce a polarization along the same path as the optical signal E. 22 The optical signal E with orthogonal polarization direction is linearly polarized. 32 The Faraday rotator 1051 can convert the optical signal E 32 The polarization is rotated by an angle (e.g., 45 degrees) to produce a polarization signal E with the same polarization as the optical signal E. 23 The optical signal E with orthogonal linear polarization (i.e., along the x-direction) 33 Optical signal E 33 It can then be internally coupled via sub-coupler 1002 to generate an internally coupled optical signal E3 that is guided to waveguide 933, such as Figure 10B As shown in the image.

[0232] According to some embodiments described above, the optional polarization rotator 1052 can be omitted, resulting in a polarization rotator with E... 11 Optical signals with the same polarization can be used for target illumination. Therefore, signals from the target, along with... Figure 10C Optical signal E in 11 Incident optical signals propagating along the same but opposite light paths can include those having the same characteristics as... Figure 10D The optical signal E shown 22 and E 32 One or both of the two incident optical signal components with the same polarization, wherein the optical signal E 22 Along with optical signal E 11 The polarizations are linearly polarized in the same direction, and the optical signal E 32 Along with optical signal E 22 The polarization directions are linearly polarized and orthogonal. In this case, according to the optical signal E... 11 The polarization-dependent beam splitter 1041, configured with the polarization direction, can generate a beam with E 11 Optical signals E with the same optical path but opposite direction 22 The optical path, and the optical signal E 32 It can propagate along a different optical path in space, which is shifted differently from the case with polarization rotator 1052. For example, the incident optical signal E 32 It can now propagate along the following optical path, which is connected to the optical signal E. 22 The directions are the same, but the orientation toward the xy plane is no longer as shown. Figure 10DThe negative x-direction is laterally shifted. To compensate for the different directions of the lateral displacement, the position of the sub-coupler 1002 on the substrate surface may need to be adjusted accordingly.

[0233] According to some embodiments, the components of the polarization transformation separation configuration 1010 can be manifested as separate components, such as... Figure 10C As shown in the diagram. According to other embodiments, some or all of the components in the polarization transformation separation configuration 1010 may be represented as a single combined component. Furthermore, according to some embodiments, the polarization transformation separation configuration 1010 may be an optical component separate from the PIC chip including the polarization diversity free space to waveguide coupler 1000, such as… Figure 10C As shown in the diagram. According to other embodiments, some or all components of the polarization transformation separation configuration 1010 may be attached to the surface of the PIC chip including the coupler 1000. According to a further embodiment, some or all components of the polarization transformation separation configuration 1010 may be within or part of the PIC chip including the coupler 1000.

[0234] exist Figure 10B , Figure 10C and Figure 10D For illustrative purposes, the optical signal is depicted as propagating along the z-direction and incident normally on coupler 1000, polarization-dependent beam splitter 1041, Faraday rotator 1051, and polarization rotator 1052. Typically, the propagation direction of the optical signal can be incident normally relative to these components or at an angle of incidence different from normal incidence.

[0235] Figure 11A A perspective view of a three-waveguide polarization diversity free space to waveguide coupler 1100 according to another embodiment of this disclosure is shown. Figure 11A As shown by the dashed lines, the three-waveguide polarization diversity free-space to waveguide coupler 1100 (referred to herein as coupler 1100 for simplicity) comprises three sub-couplers 1101, 1102, and 1103. According to some embodiments, each of sub-couplers 1101, 1102, and 1103 can be implemented using a free-space to waveguide coupler coupled to a single waveguide, including but not limited to a grating coupler. According to other embodiments, each of sub-couplers 1102 and 1103 can be implemented using a polarization-independent free-space to waveguide coupler.

[0236] refer to Figure 11A Waveguide 921 is connected to sub-coupler 1101 as an external coupling waveguide, waveguide 922 is connected to sub-coupler 1102 as a first internal coupling waveguide, and waveguide 933 is connected to sub-coupler 1103 as a second internal coupling waveguide. Here, Figure 11AWaveguides 921, 922, and 933 in the middle and Figure 9 The waveguides 921, 922 and 933 of the coherent sensing unit 900 are the same.

[0237] like Figure 11A As shown, the main function of sub-coupler 1101 is to couple optical signals from outside the transmitter for target illumination. The optical signal E1 in waveguide 921 is coupled externally into free space through sub-coupler 1101, serving as the emitted optical signal E. 01 Emitted optical signal E 01 Polarization is achieved according to the design of sub-coupler 1101. For example, as... Figure 11A As shown in, the optical signal E 01 It is linearly polarized along the x-direction.

[0238] like Figure 11A As shown, the primary function of sub-coupler 1102 is to act as a receiver to couple the incident optical signal into the receiver. Figure 9 In the coherent sensing unit 900, the polarization state of the incident optical signal is orthogonal to the polarization of the emitted optical signal. (Reference) Figure 11A It has the characteristics of the emitted optical signal E 01 Orthogonally polarized incident optical signal E 24 Internal coupling can be achieved through sub-coupler 1102 to generate an internally coupled optical signal E2 in waveguide 922. The incident optical signal E2 is optimally internally coupled via sub-coupler 1102. 24 The polarization is determined based on the design of the sub-coupler 1102. As an example, the optimally coupled optical signal E... 24 Linear polarization along the y-direction, such as Figure 11A As shown in the image.

[0239] like Figure 11A As shown, the primary function of sub-coupler 1103 is to act as a receiver to couple the incident optical signal into the receiver. Figure 9 In the coherent sensing unit 900, the polarization state of the incident optical signal is orthogonal to the polarization of the incident optical signal coupled to the waveguide 922 by the sub-coupler 1102. (Reference) Figure 11A It has optical signal E 24 Orthogonally polarized incident optical signal E 34 Internally coupled via sub-coupler 1103 to generate an internally coupled optical signal E3 in waveguide 933. The incident optical signal E3 is optimally coupled by sub-coupler 1103. 34 The polarization is determined based on the design of the sub-coupler 1104. For example, the optimally coupled optical signal E... 34 Linear polarization along the x-direction, such as Figure 11A As shown in the image.

[0240] Figure 11B A side view of a polarization transformation separation configuration 1110 according to another embodiment of the present disclosure is shown. This polarization transformation separation configuration 1110 is used in conjunction with a three-waveguide polarization diversity free space to waveguide coupler 1100 for external coupling of optical signals. Figure 11C This illustrates the use of internally coupled optical signals. Figure 11B The side view of configuration 1110 shown. Figure 11B and Figure 11C As shown, configuration 1110 causes the incident optical signal E reaching coupler 1100 to... 24 and E 34 and the emitted optical signal E emitted by coupler 1100 01 It can propagate along a common optical path, which is located between configuration 1110 and the target. The polarization transformation separation configuration 1110 includes a Faraday rotator 1151, an optional polarization rotator 1152, and polarization-dependent beam splitters 1141 and 1142, such as... Figure 11B and Figure 11C As shown. For illustrative purposes, Figure 11D Show Figure 11B A top view of the polarization state of the optical signal. Similarly, Figure 11E Show Figure 11C A top view of the polarization state of the optical signal in the image.

[0241] Figure 11B and Figure 11C The polarization transformation separation configuration 1110 in the middle is similar to Figure 10C and Figure 10D The polarization transformation separation configuration is 1010. The main difference between configuration 1110 and configuration 1010 is that, as... Figure 11B and Figure 11C The configuration 1110 shown has an additional polarization-dependent beamsplitter 1142, which is positioned between the Faraday rotator 1151 and the polarization diversity free space-to-waveguide coupler 1100. More specifically, Figure 11B and Figure 11C Component 1141 is a polarization-dependent beam splitter, which is similar to... Figure 10C and Figure 10D The polarization-dependent beam splitter 1041 in the example. Figure 11B and Figure 11C Component 1152 is an optional polarization rotator, which is similar to... Figure 10C and Figure 10D The polarization rotator 1052 in the middle. Figure 11B and Figure 11C Component 1151 is a Faraday rotator, which is similar to Figure 10C and Figure 10D Faraday rotator 1051 in the middle.

[0242] refer to Figure 11A and Figure 11B The sub-coupler 1101 of coupler 1100 can transmit the optical signal E 01 The output is sent to free space. According to some embodiments, the additional polarization-dependent beam splitter 1142 in configuration 1110 can be configured such that the optical signal E... 01 It can be laterally shifted in the xy plane to generate a signal with the same characteristics as the optical signal E. 01 Optical signals E with the same polarization 10 Among them, optical signal E 01 This can be represented as an e-ray relative to the polarization-dependent beam splitter 1142. For example... Figure 11B As shown in, the optical signal E 01 Linearly polarized along the x-direction, and the emitted optical signal is shifted towards the positive x-direction. Similar to... Figure 10C The polarization transformation separation configuration 1010, and the Faraday rotator 1151, polarization rotator 1152, and polarization-dependent beam splitter 1141 in the polarization transformation separation configuration 1110 can transform... Figure 11B Optical signal E in 10 To generate optical signal E 13 .like Figure 11B As shown in, the optical signal E 13 Along with optical signal E 01 The direction is orthogonal to the direction (i.e., along the y-direction) and linearly polarized.

[0243] For optical signal reception, from the target, along with... Figure 11B Optical signal E in 13 Incident optical signals propagating along the same but opposite light paths can include those having the same characteristics as the incident optical signal E. 20 and E 30 One or both of the two incident optical signal components with the same polarization, such as Figure 11C As shown in the figure, the optical signal E 20 Along with optical signal E 13 The polarizations are linearly polarized in the same direction, and the optical signal E 30 Along with optical signal E 20 The polarization is orthogonal to the linear polarization direction. For example, such as... Figure 11C As shown, E 20 Linear polarization along the y-direction, E 30 Linear polarization along the x-direction. Similar to polarization transformation separation configuration 1010, the polarization-dependent beam splitter 1141, polarization rotator 1152, and Faraday rotator 1151 in polarization transformation separation configuration 1110 can transform... Figure 11C Optical signal E in 20 To produce with Figure 11B Optical signal E in 10 The optical signal E with orthogonal polarization 23 .like Figure 11B and Figure 11C As shown, the additional polarization-dependent beam splitter 1142 in configuration 1110 is configured such that the optical signal E 23 It can generate optical signal E 24 It has the same as Figure 11B Optical signal E in 01 The polarizations are orthogonal and propagate along the optical path to reach sub-coupler 1102. That is, the optical signal E 24 This can be represented as the o-ray relative to the polarization-dependent beam splitter 1142. Optical signal E 24 It can then be internally coupled via sub-coupler 1102 to generate an internally coupled optical signal E2 that is guided to waveguide 922, such as Figure 11A As shown in the image.

[0244] Similarly, the polarization-dependent beam splitter 1141, polarization rotator 1152, and Faraday rotator 1151 in the polarization transformation separation configuration 1110 can transform... Figure 11C Optical signal E in 30 To produce with Figure 11C Optical signal E in 23 The optical signal E with orthogonal polarization 33 Due to the configuration of the additional polarization-dependent beam splitter 1142, the optical signal E 33 It can be laterally shifted in the xy plane to generate a signal with the same characteristics as the optical signal E. 24 The optical signal E with orthogonal polarization 34 Its method is similar to that of generating optical signal E 10 Optical signal E 01 Same, but in opposite directions. For example... Figure 11C As shown in, the optical signal E 33 Linearly polarized along the x-direction and shifted towards the negative x-direction to produce an optical signal E that is also linearly polarized along the x-direction. 34 Similar to optical signal E 01 Optical signal E 33 This can be represented as the e-ray relative to the polarization-dependent beam splitter 1142. Optical signal E 34 It can then be internally coupled via sub-coupler 1103 to generate an internally coupled optical signal E3 that is guided to waveguide 933, such as Figure 11A As shown in the image.

[0245] According to some embodiments, the optional polarization rotator 1152 in the polarization transformation separation configuration 1110 can be omitted, resulting in a polarization rotator that is consistent with the optical signal E.11 The emitted optical signal with the same polarization state can be used for target illumination. Similar to omitting the optional polarization rotator 1052 in polarization transformation separation configuration 1010, omitting the polarization rotator 1152 in polarization separation configuration 1110 may require consideration of the optical signal E. 11 The polarization direction of the polarization-dependent beam splitter 1141 may be reconfigured, for example by orienting the optical axis of the polarization-dependent beam splitter 1141. The positions of one or both of the sub-couplers 1102 and 1103 may also need to be adjusted accordingly on the substrate surface to compensate for the different orientations of the optical axis of the polarization-dependent beam splitter 1141.

[0246] Similar to polarization transformation separation configuration 1010, according to some embodiments, the components of polarization transformation separation configuration 1110 can be manifested as separate components, such as... Figure 11B As shown in the diagram. According to other embodiments, some or all of the components in the polarization transformation separation configuration 1110 may be represented as a single combined component. Furthermore, according to some embodiments, the polarization transformation separation configuration 1110 may be an optical component separate from the PIC chip including the polarization diversity free space to waveguide coupler 1100, such as… Figure 11B As shown in the diagram. According to other embodiments, some or all components of the polarization transformation separation configuration 1110 may be attached to the surface of the PIC chip including the coupler 1100. According to a further embodiment, some or all components of the polarization transformation separation configuration 1110 may be within or part of the PIC chip including the coupler 1100.

[0247] exist Figure 11A , Figure 11B and Figure 11C For illustrative purposes, the optical signal is depicted as propagating along the z-direction and incident normally at coupler 1100, polarization-dependent beam splitters 1141 and 1142, Faraday rotator 1151, and polarization rotator 1152. Typically, the propagation direction of the optical signal may be incident normally relative to these components or at an angle of incidence different from normal incidence.

[0248] Figure 12A A side view of a polarization transformation separation configuration 1210 according to another embodiment of the present disclosure is shown, which is used in conjunction with a three-waveguide polarization diversity free space to waveguide coupler 1100 for external coupling of optical signals. Figure 12B This illustrates the use of internally coupled optical signals. Figure 12A The side view of configuration 1210 shown. Configuration 1210 enables the incident optical signal E to reach coupler 1100. 24 and E 34 and the emitted optical signal E emitted by coupler 1100 01It can propagate along a common optical path, which is located between configuration 1210 and the target. For example... Figure 12A and Figure 12B As shown, the polarization transformation separation configuration 1210 includes a Faraday rotator 1251, an optional polarization rotator 1252, polarization-correlated beam splitters 1241 and 1242, and an optional quarter-wave plate 1261. For illustrative purposes, Figure 12C Show Figure 12A A top view of the polarization state of the optical signal. Similarly, Figure 12D Show Figure 12B A top view of the polarization state of the optical signal in the image.

[0249] Figure 12A and Figure 12B The polarization transformation separation configuration 1210 in the middle is Figure 11B and Figure 11C A modified embodiment of the polarization transformation separation configuration 1110. The main modifications of configuration 1210 relative to configuration 1110 include the following: (1) the polarization rotator 1252 (if present) in configuration 1210 is configured to achieve polarization rotation in a direction opposite to the rotation direction achieved by the polarization rotator 1152 in configuration 1110; (2) the polarization-dependent beam splitter 1241 in configuration 1210 is configured by orienting the optical axis of 1241, for example, to achieve lateral displacement (if present) in a direction opposite to the lateral displacement achieved by the polarization-dependent beam splitter 1242 in the presence of an optional polarization rotator 1252; and (3) configuration 1210 includes an additional quarter-wave plate 1261 disposed between the polarization-dependent beam splitter 1241 and the target. Therefore, the polarization-dependent beam splitter 1242 in configuration 1210 is similar to the polarization-dependent beam splitter 1142 in configuration 1110, and the Faraday rotator 1251 in configuration 1210 is similar to the Faraday rotator 1151 in configuration 1110.

[0250] On the one hand, refer to Figure 12B , and like Figure 11C Compared to the corresponding optical path in configuration 1110 shown, modifications (1) and (2) in configuration 1210 described above can result in optical signal E 20 E 21 E 22 E 23 and E 24 The optical path has the same characteristics as the optical signal E. 30 E 31 E 32 E 33 and E 34The path length of the optical path is similar to the path length. Modifying (1) and (2) thus allows for minimizing the optical signals E reaching sub-couplers 1102 and 1103, respectively. 24 and E 34 The advantages of the phase difference between them. (Reference) Figure 12A If an optional polarization rotator 1252 is available, the above modifications (1) and (2) can also make the optical signal E 13 It can be emitted at a position and orientation on the surface of polarization-dependent beamsplitter 1241, which is similar to the optical signal E on the surface of subcoupler 1101. 01 The emission position and direction. Therefore, modifying (1) and (2) can have another advantage, namely, by using the emitted optical signal from the sub-coupler 1101 in the coupler 1100, it is possible to achieve the installation of the polarization transformation separation configuration 1210 and the simplified optical alignment of the coupler 1100.

[0251] On the other hand, reference Figure 12A and Figure 12C The above modification (3) enables the use of circularly polarized optical signals E 1C Used for target illumination. More specifically, the quarter-wave plate 1261 can transform the linearly polarized optical signal E. 13 To generate a circularly polarized optical signal E for target illumination. 1C .like Figure 12A and 12C As shown in, the optical signal E 13 Linearly polarized along the x-direction, and the optical signal E 1C It is circularly polarized to the right relative to its propagation direction. For optical signal reception, the incident optical signal from the target can be decomposed based on any two orthogonal polarizations. For example... Figure 12B and Figure 12D As shown, the incident optical signal propagating from the target toward the negative z-direction can include two polarization components E. 2C and E 3C One or two of them, wherein one of them is circularly polarized to the right relative to its direction of propagation, and the other of them is circularly polarized to the left relative to its direction of propagation. For example... Figure 12B and Figure 12D As shown, relative to the negative z-direction, E 2C It is right-circularly polarized, E 3C It is left-circularly polarized. For example... Figure 12B As shown, the quarter-wave plate 1261 can transform the optical signal E 2C To generate a linearly polarized optical signal E 20 And transform the optical signal E 3C To produce with E 20 Orthogonally polarized optical signal E 30.like Figure 12B and Figure 12D As shown, E 20 Linear polarization along the x-direction, E 30 Linear polarization along the y-direction. In some respects, using a circularly polarized optical signal instead of a linearly polarized optical signal for target illumination achieved by modifying (3) can have the advantage of minimizing the odds of significant signal loss due to certain characteristics of the target or its surface. Such significant signal loss may occur, for example, but not limited to, when the target surface preferentially reflects linearly polarized light that happens to be orthogonal to the linearly polarized illumination optical signal. A circularly polarized illumination optical signal always includes a pair of orthogonal linearly polarized components, in which case the loss of reflected optical signal can be avoided.

[0252] According to some embodiments, the optional polarization rotator 1252 in the polarization transform separation configuration 1210 can be omitted. Similar to omitting the optional polarization rotator 1152 from the polarization transform separation configuration 1110, omitting the polarization rotator 1252 in the polarization transform separation configuration 1210 may require reconfiguring the polarization-dependent beam splitter 1241 and the quarter-wave plate 1261, for example, by adjusting the polarization rotator 1252 according to the optical signal E. 11 The polarization direction is used to orient the optical axes of the polarization-dependent beam splitter 1241 and the quarter-wave plate 1261. In order to compensate for the different orientations of the optical axes of the polarization-dependent beam splitter 1241 and the quarter-wave plate 1261, the positions of one or both of the sub-couplers 1102 and 1103 may also need to be adjusted accordingly on the substrate surface.

[0253] Similar to polarization transformation separation configuration 1110, according to some embodiments, the components of polarization transformation separation configuration 1210 can be manifested as separate components, such as... Figure 12A As shown in the diagram. According to other embodiments, some or all of the components in the polarization transformation separation configuration 1210 may be represented as a single combined component. Furthermore, according to some embodiments, the polarization transformation separation configuration 1210 may be an optical component separate from the PIC chip, including the polarization diversity free space to waveguide coupler 1100, such as… Figure 12A As shown in the diagram. According to other embodiments, some or all components of the polarization transformation separation configuration 1210 may be attached to the surface of the PIC chip including the coupler 1100. According to a further embodiment, some or all components of the polarization transformation separation configuration 1210 may be within or part of the PIC chip including the coupler 1100.

[0254] exist Figure 12A and Figure 12BFor illustrative purposes, the optical signal is depicted as propagating along the z-direction and incident normally on coupler 1100, polarization-correlated beam splitters 1241 and 1242, Faraday rotator 1251, polarization rotator 1252, and quarter-wave plate 1261. Typically, the propagation direction of the optical signal can be incident normally relative to these components or at an angle of incidence different from normal incidence.

[0255] Figure 13A A top view of a three-waveguide polarization diversity free-space to waveguide coupler 1300 according to another embodiment of the present disclosure is shown. Figure 13B Show Figure 13A A perspective view of the coupler 1300 shown. Furthermore, Figure 13B The polarized outgoing optical signal and incident optical signal E, coupled to sub-couplers 1301, 1302 and 1303 respectively, are shown. 01 E 24 and E 34 .like Figure 13A and Figure 13B As shown by the dashed lines, the three-waveguide polarization diversity free-space to waveguide coupler 1300 (referred to herein as coupler 1300 for simplicity) comprises three sub-couplers 1301, 1302, and 1303. According to some embodiments, each of sub-couplers 1301, 1302, and 1303 can be implemented using a free-space to waveguide coupler coupled to a single waveguide, including but not limited to a grating coupler. According to other embodiments, each of sub-couplers 1302 and 1303 can be implemented using a polarization-independent free-space to waveguide coupler. Coupler 1300 is as follows: Figure 11A A modified embodiment of the coupler 1100 shown. Figure 13A and Figure 13B The sub-coupler 1301 of the coupler 1300 is similar to Figure 11A The sub-coupler 1101 of the coupler 1100 in the middle. Figure 13A and Figure 13B The sub-coupler 1302 of the coupler 1300 is similar to Figure 11A The sub-coupler 1102 of the coupler 1100 in the middle. Figure 13A and Figure 13B The sub-coupler 1303 of the coupler 1300 is similar to Figure 11A The sub-coupler 1103 of coupler 1100. Comparing coupler 1300 and coupler 1100, the spatial arrangement of the sub-couplers of coupler 1300 is... Figure 9 Some embodiments of the coherent sensing unit 900 may be advantageous (e.g., more compact).

[0256] Figure 13CA side view of a polarization transformation separation configuration 1310 according to yet another embodiment of the present disclosure is shown. This polarization transformation separation configuration 1310 is used in conjunction with a three-waveguide polarization diversity free space to waveguide coupler 1300 for external coupling of optical signals. Figure 13D Show Figure 13C Another side view of configuration 1310 shown. Figure 13E This illustrates a method for internally coupled optical signals, such as... Figure 13C The side view of configuration 1310 shown. Figure 13F Show Figure 13E Another side view of configuration 1310 shown. (As shown) Figure 13C and Figure 13E As shown, configuration 1310 enables the incident optical signal E reaching coupler 1300. 24 and E 34 and the emitted optical signal E emitted by coupler 1300 01 It can propagate along a common optical path, which is located between configuration 1310 and the target.

[0257] For the purpose of explanation, Figure 13G Show Figure 13C and Figure 13D A top view of the polarization state of the optical signal and its path position in the xy plane. Figure 13G The illustration also shows a top view of coupler 1300, indicating the positions of sub-couplers 1301, 1302, and 1303 in the xy plane, as... Figure 13G A reference for the path position of the optical signal in the image. Similarly, Figure 13H Show Figure 13E and Figure 13F A top view of the polarization state of the optical signal and its path position in the xy plane. Figure 13H The path location on the mid-xy plane can be referenced. Figure 13G The illustration shows the positions of sub-couplers 1301, 1302, and 1303.

[0258] according to Figure 13C , Figure 13D , Figure 13E and Figure 13F The polarization transformation separation configuration 1310 includes a Faraday rotator 1351, an optional polarization rotator 1352, polarization-correlated beam splitters 1341 and 1342, and an optional quarter-wave plate 1361.

[0259] Figure 13C , Figure 13D , Figure 13E and Figure 13F The polarization transformation separation configuration 1310 shown is Figure 11B and Figure 11CA modified embodiment of the polarization transformation separation configuration 1110. The main modifications of configuration 1310 relative to configuration 1110 include the following: (1) the polarization-dependent beam splitter 1341 of configuration 1310 is configured, for example but not limited to, by orienting the optical axis of polarization-dependent beam splitter 1341 in such a way that a lateral displacement (if any) is achieved in a direction on the xy plane, which is perpendicular to the lateral displacement achieved by polarization-dependent beam splitter 1342 in the presence of an optional polarization rotator 1352; and (2) configuration 1310 includes an additional quarter-wave plate 1361 disposed between polarization-dependent beam splitter 1341 and the target. Therefore, the polarization-dependent beam splitter 1342 configured 1310 is similar to the polarization-dependent beam splitter 1142 configured 1110, the Faraday rotator 1351 configured 1310 is similar to the Faraday rotator 1151 configured 1110, and the polarization rotator 1352 configured 1310 is similar to the polarization rotator 1152 configured 1110.

[0260] More specifically, in the polarization transformation separation configuration 1310, the polarization-dependent beam splitter 1342 achieves lateral displacement (if any) along the x-direction, such as... Figure 13C and Figure 13E As shown in the diagram, the polarization-dependent beam splitter 1341 achieves lateral displacement (if any) along the y-direction, as... Figure 13D and Figure 13F As shown in the diagram. This contrasts with polarization transformation separation configurations 1110 and 1210, where the polarization-dependent beam splitter in either configuration achieves lateral displacement (if any) along the x-direction.

[0261] Similar to Figure 12A and Figure 12B The polarization transformation separation configuration 1210 in the reference Figure 13E and Figure 13F , and like Figure 11C Compared to the corresponding optical path in configuration 1110 shown, the modification (1) in configuration 1310 described above can result in the optical signal E 20 E 21 E 22 E 23 and E 24 The path length of the optical path and the optical signal E 30 E 31 E 32 E 33 and E 34 The path lengths of the optical paths are similar. For example... Figure 13E and Figure 13F The optical signal E shown 2C and E 3CEach of the elements experiences a lateral displacement as it propagates from the quarter-wave plate 1361 through the polarization-dependent beam splitter 1341, polarization rotator 1352, Faraday rotator 1351, and polarization-dependent beam splitter 1342 to the coupler 1300. Therefore, modification (1) can minimize the optical signals E reaching the sub-couplers 1302 and 1303, respectively. 2C and E 3C The advantages of the phase difference between them.

[0262] On the other hand, similar to Figure 12A and Figure 12B Configuration 1210, see reference. Figure 13C and Figure 13D In configuration 1310, the above modification (2) can also be used to utilize the circularly polarized optical signal E. 1C Used for target illumination.

[0263] According to some embodiments, the optional polarization rotator 1352 in the polarization transformation separation configuration 1310 can be omitted. Similar to omitting the optional polarization rotator 1252 from the polarization transformation separation configuration 1210, omitting the polarization rotator 1352 in the polarization separation configuration 1310 may require reconfiguring the polarization-dependent beam splitter 1341 and the quarter-wave plate 1361, for example, by adjusting the polarization-dependent beam splitter 1341 according to the optical signal E. 11 The polarization direction is used to orient the optical axes of the polarization-dependent beam splitter 1341 and the quarter-wave plate 1361. The positions of one or both of the sub-couplers 1302 and 1303 may also need to be adjusted accordingly on the substrate surface to compensate for the different orientations of the optical axes of the polarization-dependent beam splitter 1341 and the quarter-wave plate 1361.

[0264] Similar to polarization transformation separation configuration 1110, according to some embodiments, components of polarization transformation separation configuration 1310 can be manifested as separate components, such as... Figure 13C As shown in the diagram. According to other embodiments, some or all of the components in the polarization transformation separation configuration 1310 may be represented as a single combined component. Furthermore, according to some embodiments, the polarization transformation separation configuration 1310 may be an optical component separate from the PIC chip including the polarization diversity free space to waveguide coupler 1300, such as… Figure 13C As shown in the diagram. According to other embodiments, some or all components of the polarization transformation separation configuration 1310 may be attached to the surface of the PIC chip including the coupler 1300. According to a further embodiment, some or all components of the polarization transformation separation configuration 1310 may be within or part of the PIC chip including the coupler 1300.

[0265] exist Figure 13B , Figure 13C , Figure 13D , Figure 13Eand Figure 13F For illustrative purposes, the optical signal is depicted as propagating along the z-direction and incident normally on coupler 1300, polarization-correlated beam splitters 1341 and 1342, Faraday rotator 1351, polarization rotator 1352, and quarter-wave plate 1361. Typically, the propagation direction of the optical signal can be incident normally relative to these components or at an angle of incidence different from normal incidence.

[0266] In respectively Figure 1A , Figure 7A , Figure 7B , Figure 8 and Figure 9 The coherent sensing units 100, 700, 710, 800, and 900 shown can generate emitted optical signals with fixed polarization for target illumination. In some applications of optical coherent sensing, it may be desirable for the polarization state of the illumination optical signal to be dynamically adjustable.

[0267] Figure 14 A plan view of a coherent sensing unit 1400 for transmitting and receiving optical signals based on polarization diversity according to an embodiment of the present disclosure is shown, wherein the polarization of the transmitted optical signal is adjustable. The coherent sensing unit 1400 is similar to coherent sensing units 700, 710, 800, and 900 for detecting incident optical signals having any polarization state. The main difference between the coherent sensing unit 1400 and the coherent sensing unit 900 is that the coherent sensing unit 1400 includes a polarization diversity free space-to-waveguide coupler, which, in addition to guiding an internally coupled optical signal having any polarization state to a different waveguide than the waveguide carrying the outgoing optical signal, can also be used for external coupling of an outgoing optical signal having any polarization state.

[0268] More specifically, see reference Figure 14 Light source signal E S1 and E S2 At least one of them is provided to the coherent sensing unit 1400. Light source signal E S1 and E S2 The light source signal E is guided to the coherent sensing unit 1400 via waveguides 1421 and 1431, respectively. According to some embodiments, the light source signal E... S1 and E S2 They can originate from the same light source. In such a case, from E S1 and E S2 The generated emitted optical signals can be coherently combined to form a single optical signal. According to other embodiments, the light source signal E... S1 and E S2The light sources can be different. One or both of waveguides 1421 and 1431 can be connected to an optional phase shifter used to adjust the relative phase between the optical signals in waveguides 1421 and 1431. As an example, in Figure 14 In the middle, waveguide 1431 can be connected to phase shifter 1451, which will phase-shift the light source signal E. S2 The optical signal E4 is guided to waveguide 1432. According to some embodiments, phase shifter 1451 may be, but is not limited to, an electro-optic phase shifter or a thermo-optic phase shifter. Local oscillator (LO)E LO It is provided to the coherent sensing unit 1400 through waveguide 1434.

[0269] exist Figure 14 In this context, the polarization diversity free space to waveguide coupler 1401 (referred to as coupler 1401 for simplicity) is a four-waveguide coupler connected to waveguides 1421, 1422, 1432, and 1433. Coupler 1401 can be used as both a transmitter and a receiver.

[0270] As a transmitter, reference Figure 14 Coupler 1401 can couple the optical signal E1 from waveguide 1421 (which is essentially the same as the light source signal E) S1 The optical signal E4 from waveguide 1432 is coupled into free space as one or more outgoing optical signals, which can be used for target illumination in an optical coherent imager. The outgoing optical signal output by coupler 1401 propagates in a direction outside the xy plane (i.e., E...). out The propagation direction has a non-zero z-component. The emitted optical signal is polarized with a polarization state defined by the design of coupler 1401. According to some embodiments, the emitted optical signal generated by optical signal E1 can be orthogonally polarized relative to the emitted optical signal generated by optical signal E4. In some embodiments, where optical signals E1 and E4 are coherent, the emitted optical signal can manifest as a single emitted optical signal E with a polarization state defined by the design of coupler 1401 and the amplitude and relative phase of optical signals E1 and E4. out .

[0271] As a receiver, coupler 1401 can convert the incident optical signal E in The incident optical signal E is coupled to the coherent sensing unit 1400. in It can be guided to one or both of waveguides 1422 and 1433, depending on the incident optical signal E. in The polarization state. The incident optical signal E coupled to waveguides 1422 and 1433. inThe polarization component depends on the design of coupler 1401. According to some embodiments, the optical signal E1 is non-zero, and the polarization component is related to the output optical signal E generated by the optical signal E1. out The incident optical signal E with orthogonal polarization components in The polarization component can be guided into waveguide 1422 as an internally coupled optical signal E2, and interacts with the incident optical signal E2 guided into waveguide 1422. in The incident optical signal E with orthogonal polarization components in The polarization component can be guided to waveguide 1433 as an internally coupled optical signal E3. According to other embodiments, the optical signal E4 is non-zero, and the emitted optical signal E3 generated by the optical signal E4 is... out The incident optical signal E with orthogonal polarization components in The polarization component can be guided into waveguide 1433 as an internally coupled optical signal E3, and interacts with the incident optical signal E3 guided into waveguide 1433. in The incident optical signal E with orthogonal polarization components in The polarization component can be guided to waveguide 1422 as an internally coupled optical signal E2.

[0272] exist Figure 14 Although coupler 1401 is depicted as a single entity, it typically includes a single photonic component or multiple photonic components. Embodiments of coupler 1401 will be described below. Figure 15A , Figure 16A and Figure 17A As shown in the figure. According to some embodiments, similar to Figure 1A and Figure 1B Coupler 101 and coupler 1401 may also include any of the TE-TM mode converters, splitters and combiners.

[0273] exist Figure 14 In the middle, shunting coupler 1406 pairs the LO E from waveguide 1434. LO Split the circuit and use a portion of the LO as LO E. LO,1 Guided to waveguide 1423, a portion of the LO is used as LO E. LO,2 The signal is guided to waveguide 1435. The portions of the LO transmitted to waveguides 1423 and 1435, respectively, depend on the splitting ratio and loss of splitter coupler 1406. According to some embodiments, splitter coupler 1406 may be a 50 / 50 splitter coupler. According to other embodiments, splitter coupler 1406 may have a splitting ratio other than 50 / 50.

[0274] exist Figure 14In this configuration, component 1402 is a 2×2 optical coupler that mixes the internally coupled optical signal E2 from waveguide 1422 and the LO signal E from waveguide 1423. LO,1 The mixed signal is then split and directed to waveguides 1424 and 1425. According to some embodiments, the 2×2 optical coupler 1402 can be similar to... Figure 9 The coherent sensing unit 900 in the middle has a 2×2 optical coupler 902.

[0275] exist Figure 14 In this context, component 1403 is a square-law photodetector that receives and detects optical signals from waveguide 1424. Similarly, in... Figure 14 In this context, component 1404 is a square-law photodetector that receives and detects optical signals from waveguide 1425. According to some embodiments, photodetectors 1403 and 1404 can be similar to... Figure 9 The photodetectors 903 and 904 of the coherent sensing unit 900 in the middle.

[0276] exist Figure 14 In, similar to Figure 9 The coherent sensing unit 900 in the middle has a 2×2 optical coupler 912. Component 1412 is a 2×2 optical coupler that mixes the internally coupled optical signal E3 from waveguide 1433 and the LO E from waveguide 1435. LO,2 The mixed signal is then split and directed to waveguides 1436 and 1437.

[0277] exist Figure 14 In this context, component 1413 is a square-law photodetector that receives and detects optical signals from waveguide 1436. Similarly, in... Figure 14 In this context, component 1414 is a square-law photodetector that receives and detects optical signals from waveguide 1437. According to some embodiments, photodetectors 1413 and 1414 can be similar to... Figure 9 The photodetectors 913 and 914 of the coherent sensing unit 900 in the middle.

[0278] Figure 15A A top view of a four-waveguide polarization diversity free space to waveguide coupler 1500 (referred to herein as coupler 1500 for simplicity) according to an embodiment of the present disclosure is shown. Figure 15B Show Figure 15A Perspective view of the coupler 1500 shown. Figure 15B Additionally, the polarized outgoing optical signal and incident optical signal E coupled to sub-couplers 1501, 1502, 1503, and 1504 are shown respectively. 01 E 24 E 34 and E 04 .like Figure 15AAs shown by the dashed lines, coupler 1500 includes four sub-couplers 1501, 1502, 1503, and 1504. According to some embodiments, each of sub-couplers 1501, 1502, 1503, and 1504 can be implemented as a free-space to waveguide coupler coupled to a single waveguide, which includes, but is not limited to, a grating coupler. According to some embodiments, each of sub-couplers 1502 and 1503 can be implemented as a polarization-independent free-space to waveguide coupler. Coupler 1500 is as follows... Figure 13A A modified embodiment of the coupler 1300 shown adds a connection to Figure 14 The waveguide 1432 of the coherent sensing unit 1400 in the middle has a sub-coupler 1504.

[0279] Figure 15C A side view of a polarization transformation separation configuration 1510 according to an embodiment of the present disclosure is shown. This polarization transformation separation configuration is used in conjunction with a four-waveguide polarization diversity free space to waveguide coupler 1500 for external coupling of optical signals. Figure 15F This illustrates a method for internally coupled optical signals, such as... Figure 15C The side view of configuration 1510 shown. Configuration 1510 enables the incident optical signal E to reach coupler 1500. 24 and E 34 and the emitted optical signal E emitted by coupler 1500 01 and E 04 It can propagate along a common optical path, which is located between configuration 1510 and the target. Figure 15D Show Figure 15C Another side view of configuration 1510 shown. Figure 15G Show Figure 15F Another side view of configuration 1510 shown. Figure 15C , Figure 15D , Figure 15F and Figure 15G The diagram illustrates an embodiment of the optical path and polarization state generated by optical signals E1 and E4, and the incident optical signals E2 and E3. For simplicity, waveguides 1421, 1422, 1432, and 1433 are... Figure 15C , Figure 15D , Figure 15F and Figure 15G It is not explicitly shown in the text.

[0280] For the purpose of explanation, Figure 15E Show Figure 15C and Figure 15D A top view of the polarization state of the optical signal and its path position in the xy plane. Figure 15EAn additional illustration shows a top view of coupler 1500, indicating the positions of sub-couplers 1501, 1502, 1503, and 1504 in the xy-plane, as... Figure 15E A reference for the path position of the optical signal in the image. Similarly, Figure 15H Show Figure 15F and Figure 15G A top view of the polarization state of the optical signal and its path position on the xy plane. Figure 15H The illustration shows a top view of coupler 1500, indicating the positions of sub-couplers 1501, 1502, 1503, and 1504 in the xy-plane, as... Figure 15H The reference for the path position of the optical signal in the image.

[0281] Figure 15C , Figure 15D , Figure 15F and Figure 15G The polarization transformation separation configuration 1510 shown is... Figure 13C , Figure 13D , Figure 13E and Figure 13F The polarization transformation separation configuration 1310 shown is substantially the same, except that the quarter-wave plate 1361 used to generate the circularly polarized outgoing optical signal for target illumination is omitted. The coherent sensing unit 1400, operating with the coupler 1500 and the polarization transformation separation configuration 1510, can generate outgoing optical signals with any polarization state (including linear, circular, or elliptical polarization) for target illumination by adjusting the amplitude and relative phase of the optical signals E1 and E4 in waveguides 1421 and 1432. According to some embodiments, in order to generate an outgoing optical signal with a specific polarization state using the polarization transformation separation configuration 1510, the sub-couplers 1501, 1502, 1503, and 1504 of the coupler 1500 may need to be designed and configured to maximize the outgoing optical signal E1. 13 and E 43 Spatial overlap, such as Figure 15C , Figure 15D and Figure 15E As shown, to minimize the effect from the optical signal E 13 and E 43 Spatial variation of the polarization of the combined emitted optical signal.

[0282] exist Figure 15B , Figure 15C , Figure 15D , Figure 15F and Figure 15GFor illustrative purposes, the optical signal is depicted as propagating along the z-direction and incident normally on coupler 1500, polarization-dependent beam splitters 1541 and 1542, Faraday rotator 1551, and polarization rotator 1552. Typically, the propagation direction of the optical signal can be incident normally relative to these components or at an angle of incidence different from normal incidence.

[0283] Figure 16A A top view of a four-waveguide polarization diversity free space to waveguide coupler 1600 (referred to herein as coupler 1600 for simplicity) according to another embodiment of the present disclosure is shown. Figure 16B Show Figure 16A Perspective view of the coupler 1600 shown. Figure 16B Additionally, the polarized outgoing optical signal and incoming optical signal E coupled to subcouplers 1601 and 1602 are shown. 10 E 40 E 23 and E 33 .like Figure 16A As shown by the dashed lines, coupler 1600 includes two sub-couplers 1601 and 1602. According to some embodiments, each of sub-couplers 1601 and 1602 can be coupled via, as shown in... Figure 1B The polarization diversity free space to waveguide coupler 101 shown is as follows: Figure 2 The polarization diversity free space to waveguide coupler 200 shown is implemented as illustrated. Coupler 1600 is as follows: Figure 10A A modified embodiment of the coupler 1000 shown, wherein the additional waveguide 1432 is connected to Figure 16A The sub-coupler 1602 of the coupler 1600 is used for external coupling of the optical signal E4.

[0284] exist Figure 16B In the middle, for illustrative purposes, the emitted optical signal E 10 and incident optical signal E 23 It is plotted as being coupled to sub-coupler 1601 at different spatial locations. Typically, the emitted optical signal E 10 and incident optical signal E 23 In some embodiments, the sub-coupler 1601 can be coupled at the same spatial location, or in other embodiments, it can be coupled at different spatial locations. Similarly, the emitted optical signal E 40 and incident optical signal E 33 According to some embodiments, the subcoupler 1602 can be coupled at the same spatial location, or according to other embodiments, the subcoupler 1602 can be coupled at different spatial locations.

[0285] Figure 16CA side view of a polarization transformation separation configuration 1610 according to another embodiment of the present disclosure is shown. This polarization transformation separation configuration 1610 is used in conjunction with a four-waveguide polarization diversity free space to waveguide coupler 1600 for external coupling of optical signals. Figure 16D This illustrates the use of internally coupled optical signals. Figure 16C The side view of configuration 1610 shown is for illustrative purposes. Figure 16E Show Figure 16C A top view of the polarization state of the optical signal in the image, and Figure 16F Show Figure 16D A top view of the polarization state of the optical signal. The polarization transformation separation configuration 1610 is basically the same as... Figure 10C and Figure 10D The polarization transformation separation configuration 1010 shown is the same. Figure 16C , Figure 16D , Figure 16E and Figure 16F The diagram illustrates an embodiment of the optical path and polarization state for the outgoing optical signals generated by optical signals E1 and E4, and the incident optical signals generated by optical signals E2 and E3. For simplicity, waveguides 1421, 1422, 1432, and 1433 are shown in... Figure 16C and Figure 16D It is not explicitly shown in the text.

[0286] exist Figure 16B , Figure 16C and Figure 16D For illustrative purposes, the optical signal is depicted as propagating along the z-direction and incident normally on coupler 1600, polarization-dependent beam splitter 1641, Faraday rotator 1651, and polarization rotator 1652. Typically, the propagation direction of the optical signal can be incident normally relative to these components or at an angle of incidence different from normal incidence.

[0287] Figure 17A A perspective view of a four-waveguide polarization diversity free space to waveguide coupler 1700 (referred to herein as coupler 1700 for simplicity) according to another embodiment of the present disclosure is shown. Figure 17A The polarized outgoing optical signal and incoming optical signal E coupled to subcouplers 1701, 1702 and 1703 are also shown. 01 E 04 E 24 and E 34 .like Figure 17A As shown by the dashed lines, coupler 1700 includes three sub-couplers 1701, 1702, and 1703. According to some embodiments, sub-coupler 1701 can be configured to... Figure 1B The polarization diversity free space to waveguide coupler 101 shown is as follows: Figure 2The polarization diversity free space to waveguide coupler 200 shown is implemented, while each of the sub-couplers 1702 and 1703 can be implemented as a free space to waveguide coupler coupled to a single waveguide, including but not limited to a grating coupler. According to other embodiments, each of the sub-couplers 1702 and 1703 can be implemented as a polarization-independent free space to waveguide coupler. Coupler 1700 is as follows: Figure 11A A modified embodiment of the coupler 1100 shown, wherein the additional waveguide 1432 is connected to Figure 17A The sub-coupler 1701 of the coupler 1700 is used to externally couple optical signal E4 in addition to externally coupling optical signal E1 from waveguide 1421.

[0288] exist Figure 17A In the middle, for illustrative purposes, the emitted optical signal E 01 and emitted optical signal E 04 It is depicted as being coupled to sub-coupler 1701 at different spatial locations. According to some embodiments, the emitted optical signal E... 01 and emitted optical signal E 04 Coupled with sub-coupler 1701 at the same spatial location to ensure maximum spatial overlap of the two emitted optical signals. According to other embodiments, the emitted optical signal E... 01 and emitted optical signal E 04 It can be coupled to subcoupler 1701 at different spatial locations.

[0289] Figure 17B A side view of a polarization transformation separation configuration 1710 according to another embodiment of the present disclosure is shown. This polarization transformation separation configuration 1710 is used in conjunction with a four-waveguide polarization diversity free space to waveguide coupler 1700 for external coupling of optical signals. Figure 17C This illustrates the use of internally coupled optical signals. Figure 17B The side view of configuration 1710 shown is for illustrative purposes. Figure 17D Show Figure 17B A top view of the polarization state of the optical signal in the image, and Figure 17E Show Figure 17C A top view of the polarization state of the optical signal. The polarization transformation separation configuration 1710 is essentially the same as... Figure 11B and Figure 11C The polarization transformation separation configuration 1110 shown is the same. Figure 17B , Figure 17C , Figure 17D and Figure 17EThe diagram illustrates an embodiment of the optical path and polarization state for the emitted optical signals E1 and E4, and the incident optical signals E2 and E3. The polarization transformation separation configuration 1710, used in conjunction with coupler 1700, ensures that signal E... 01 E 10 E 11 E 12 and E 13 The optical path length is basically the same as the signal E 04 E 40 E 41 E 42 and E 43 The optical path lengths are the same, so the optical signal E 13 and E 43 The polarization of the coherently combined optical signal is essentially the same as that from the optical signal E. 01 and E 04 The coherent combined optical signals have the same polarization. For simplicity, waveguides 1421, 1422, 1432, and 1433 are... Figure 17B and Figure 17C It is not explicitly shown in the text.

[0290] exist Figure 17A , Figure 17B and Figure 17C For illustrative purposes, the optical signal is depicted as propagating along the z-direction and incident normally at coupler 1700, polarization-correlated beam splitters 1741 and 1742, Faraday rotator 1751, and polarization rotator 1752. Typically, the propagation direction of the optical signal can be incident normally relative to these components or at an angle of incidence different from normal incidence.

[0291] Figure 18A A plan view of a coherent optical sensor 1800 according to an embodiment of the present disclosure is shown. The coherent optical sensor 1800 includes a coherent sensing array 1810 and optical routing circuitry 1820 and 1830 implemented on a PIC chip.

[0292] exist Figure 18A In the middle, the optical routing circuit 1820 is used to transmit LO E LO Routing to the coherent sensing array 1810. For example, Figure 18A The optical routing circuit 1820 in the middle will LO E LO Routing to different rows of the coherent sensing array 1810. The optical routing circuit 1820 includes an optical waveguide network, wherein LO E LO The flow is controlled by multiple optical switches in the network. As an example, in Figure 18AIn the optical routing circuit 1820, there are optical switches 1821, 1822 and 1823, which may be, but are not limited to, optical switches based on Mach-Zehnder interferometer (MZI) or optical switches based on MEMS.

[0293] Understandably, other implementations of the optical routing circuit 1820 are also possible. For example, Figure 18A The optical routing circuit 1820 in the circuit can be in the form of a binary tree. The optical switch receives the input LO E. LO Directed to one or more output ports of the switch. According to some embodiments, Figure 18A The optical switch 1821 in the middle can control the LOE in waveguide 1824 LO Guided to one or both of waveguides 1825 and 1826.

[0294] The optical routing circuit 1830 is used to convert the light source signal E S The routing is directed to the coherent sensing array 1810. According to some embodiments, the optical routing circuit 1830 may present a structure similar to that of the optical routing circuit 1820. In one embodiment, the optical routing circuit 1830 may be in the form of a binary tree including optical switches 1831, 1832, and 1833. According to other embodiments, the optical routing circuit 1830 may present a structure different from that of the optical routing circuit 1820.

[0295] exist Figure 18A In this embodiment, the coherent sensing array 1810 includes an array of coherent sensing units 1801. In one embodiment, the coherent sensing array 1810 includes 24 coherent sensing units 1801 arranged in a 4×6 rectangular format (i.e., 4 rows and 6 columns). Figure 18B A row of six coherent sensing units is shown in a coherent sensing array 1810 according to an embodiment of the present disclosure.

[0296] exist Figure 18A In the coherent sensing array 1810, each coherent sensing unit 1801 is connected to two waveguides, which serve as the optical input ports of the coherent sensing unit. According to some embodiments, the coherent sensing unit 1801 can be as follows: Figure 1A The coherent sensing unit 100 shown is illustrated. According to other embodiments, the coherent sensing unit 1801 may be as follows: Figure 7A The coherent sensing unit 700 shown is illustrated. According to other embodiments, the coherent sensing unit 1801 may be as follows: Figure 8 The coherent sensing unit 800 shown is illustrated. According to a further embodiment, the coherent sensing unit 1801 may be as follows: Figure 9 The coherent sensing unit 900 shown is illustrated.

[0297] exist Figure 18AIn the middle, the two waveguides connected to the coherent sensing unit 1801 can be used to transmit the light source signal E S and LO E LO Guided into the sensing unit 1801. For example, refer to Figure 18B Waveguide 1843 can be used to transmit the light source signal E S The signal is directed to the coherent sensing unit 1801, which is connected to... Figure 18B Waveguides 1843 and 1844 are used in the design, with waveguide 1844 potentially being used to connect LO E. LO The signal is guided to the same coherent sensing unit. A splitter coupler can be used in the coherent sensing array 1810 to direct the light source signal E to the same coherent sensing unit. S and LO E LO They are assigned to different coherent sensing units 1801. For example... Figure 18B As shown, shunt couplers 1811, 1812, 1813, 1814, and 1815 can be used to split the light source signal E. S The signal is distributed to six coherent sensing units 1801. The shunt couplers 1811, 1812, 1813, 1814, and 1815 can have the same or different shunting ratios. This is based on the distribution of the light source signal E... S In some embodiments where the data is evenly distributed among the six coherent sensing units 1801, shunt coupler 1811 may have a sharding ratio of 5:1, shunt coupler 1812 may have a sharding ratio of 4:1, shunt coupler 1813 may have a sharding ratio of 3:1, shunt coupler 1814 may have a sharding ratio of 2:1, and shunt coupler 1815 may have a sharding ratio of 1:1. Similarly, according to... Figure 18B In the embodiments described, shunt couplers 1851, 1852, 1853, 1854, and 1855 can be used to connect LO E LO The signals are distributed to six coherent sensing units 1801, wherein shunt couplers 1851, 1852, 1853, 1854, and 1855 are similar to shunt couplers 1811, 1812, 1813, 1814, and 1815, which can distribute LO E LO The LO E can be evenly distributed among the six coherent sensing units 1801, or it can be non-uniformly distributed. LO It is allocated to six coherent sensing units 1801.

[0298] Figure 18A The coherent optical sensor 1800 may also include a laser source, electrical control circuitry, and electrical readout circuitry, which are not explicitly shown in the figures.

[0299] Figure 19AA plan view of a coherent optical sensor 1900 according to another embodiment of the present disclosure is shown. The coherent optical sensor 1900 includes an array of coherent sensing units 1901 coupled to a light source signal E via an optical routing circuit in an H-tree topology. S For example, such as Figure 19A The coherent optical sensor 1900 shown is a three-level H-tree with eight coherent sensing units 1901. The H-tree optical routing circuit in the coherent optical sensor 1900 is composed of a network of waveguides coupled to multiple optical switches 1902. Figure 19A The optical switch 1902 in the middle can be similar to Figure 18A The optical switches 1821, 1822, 1823, 1831, 1832 and 1833 of the coherent optical sensor 1800.

[0300] like Figure 19A As shown, each of the coherent sensing units 1901 can be coupled to the light source signal E S A single waveguide is provided to the coherent sensing unit. The light source signal E S It can be used as a light source signal for target illumination and a source of noise (LO) for heterodyne detection in the coherent sensing unit 1901. According to some embodiments, each coherent sensing unit 1901 can be as follows: Figure 7B The coherent sensing unit 710 shown is illustrated. According to other embodiments, each coherent sensing unit 1901 may be as follows: Figure 1A The coherent sensing unit 100 shown, as Figure 7A The related sensing unit 700 shown, such as Figure 8 The related sensing unit 800 shown or as Figure 9 The coherent sensing unit 900 shown herein includes a splitter coupler that can be used to split the light source signal E supplied to each coherent sensing unit 1901. S The signal is split into two streams: the light source signal E, which is used as the source signal. S Part of and LO E used as a coherent sensing unit LO E S As part of [the system / mechanism]. According to a further embodiment, each coherent sensing unit 1901 may be as follows: Figure 19B The coherent sensing unit group 1910 shown is illustrated. Figure 19A The coherent optical sensor 1900 may also include a laser source, electrical control circuitry, and electrical readout circuitry, which are not explicitly shown in the figures.

[0301] Figure 19B A plan view of a coherent sensing unit group 1910 according to an embodiment of the present disclosure is shown. In one embodiment, the coherent sensing unit group 1910 includes a plurality of coherent sensing units 1911 arranged in an H-tree topology. For example, Figure 19BThe coherent sensing unit group 1910 in the diagram is represented as a two-level H-tree with four coherent sensing units 1911. Figure 19B In the middle, component 1913 can be used to control the light source signal E. S A shunt coupler is used to split the light source signal E. S A portion of the signal is supplied to each coherent sensing unit 1911 of the coherent sensing unit group 1910. According to some embodiments, the splitting ratio of the shunt coupler 1913 may be 50 / 50 to distribute the source signal evenly to all coherent sensing units 1911 of the coherent sensing unit group 1910. Figure 19B In this context, component 1912 is a shunt coupler, which can be used to split the light source signal E supplied to each coherent sensing unit 1911. S The branch is used as the light source signal E. S A portion of the light source signal E and the LO as a coherent sensing unit S Part of it. The shunting ratio of the shunting coupler 1912 can be 50 / 50 or not.

[0302] exist Figure 19B In this context, each of the coherent sensing units 1911 can be as follows: Figure 1A The coherent sensing unit 100 shown, as Figure 7A The coherent sensing unit 700 shown, as Figure 8 The coherent sensing unit 800 shown or as Figure 9 The coherent sensing unit 900 shown is illustrated.

[0303] Figure 20A A plan view of a coherent optical sensor 2000 according to another embodiment of the present disclosure is shown. The coherent optical sensor 2000 includes a sensing region 2010 and optical routing circuitry 2020 and 2030 implemented on a PIC chip. According to some embodiments, the sensing region 2010 includes a plurality of coherent sensing unit groups 2001. Each coherent sensing unit group 2001 includes a plurality of coherent sensing units that emit outgoing optical signals for target illumination, wherein the polarization of the outgoing optical signals is adjustable.

[0304] exist Figure 20A In the middle, the optical routing circuit 2020 can be used to connect the local oscillator E LO Routing to the coherent sensing unit group 2001 in the sensing area 2010. According to some embodiments, the optical routing circuit 2020 may be similar to the optical routing circuit 1820 of the coherent optical sensor 1800. Figure 20A In the middle, the optical routing circuit 2030 can be used to convert the source light E SThe signal is routed to the coherent sensing unit group 2001 in the sensing area 2010. According to some embodiments, the optical routing circuit 2030 may be similar to the optical routing circuit 1830 of the coherent optical sensor 1800.

[0305] Figure 20B A plan view of a coherent sensing unit group 2001 according to another embodiment of the present disclosure is shown. The coherent sensing unit group 2001 includes a plurality of coherent sensing units 2002 that emit outgoing optical signals with adjustable polarization for target illumination. For illustrative purposes, the coherent sensing unit group 2001... Figure 20B The image is drawn as including four coherent sensing units 2002. Each coherent sensing unit 2002 includes components for internal coupling LO E. LO The system comprises one input waveguide and two input waveguides for internal coupling of source light, wherein the amplitude and relative phase of the source light in the two waveguides determine the polarization state of the emitted optical signal emitted from the coherent sensing unit 2002. According to some embodiments, the coherent sensing unit 2002 may be composed of, for example... Figure 14 The coherent sensing unit 1400 shown is used to implement this.

[0306] like Figure 20B As shown, each coherent sensing unit group 2001 includes multiple shunt couplers 2051, 2052, and 2053 to connect LO E LO Each coherent sensing unit 2002 is assigned to the coherent sensing unit group 2001. According to some embodiments, shunt couplers 2051, 2052, and 2053 may be similar to shunt couplers 1851, 1852, 1853, 1854, and 1855, which can transmit LO E LO Each coherent sensing unit 2002 can be uniformly distributed to the coherent sensing unit group 2001, or it can be non-uniformly distributed.

[0307] like Figure 20B As shown, each coherent sensing unit group 2001 may include an optical switch 2021, which switches the source light E S It is divided into two parts. Source Light E S The two parts can then be distributed to each coherent sensing unit 2002 via a split coupler. For example, source light E S A portion of the light source can be distributed to the coherent sensing unit 2002 via split couplers 2011, 2012, and 2013. According to some embodiments, split couplers 2011, 2012, and 2013 can be similar to split couplers 1811, 1812, 1813, 1814, and 1815, which can distribute the source light source E... SEach coherent sensing unit 2002 can be uniformly distributed among the coherent sensing unit groups 2001, or it can be non-uniformly distributed. Similarly, the source light E S A portion of the signal can be distributed to each coherent sensing unit 2002 via shunting couplers 2014, 2015, and 2016, similar to shunting couplers 2011, 2012, and 2013. According to some embodiments, the coherent sensing unit group 2001 may include waveguide crossovers 2022 to allow optical signals to cross each other with minimal loss and crosstalk within a compact PIC layout.

[0308] Figure 20C A plan view of an optical switch 2021 based on a Mach-Zehnder interferometer according to an embodiment of the present invention is shown. The optical switch 2021, as a Mach-Zehnder interferometer, includes a phase shifter 2031 to control the output portion of the optical switch 2021. According to some embodiments, the phase shifter 2031 may be an electro-optic phase shifter or a thermo-optic phase shifter.

[0309] Figure 20A The coherent optical sensor 2000 may include a laser source (not explicitly shown), electrical control circuitry, and electrical readout circuitry. Furthermore, Figure 20B The coherent sensing unit group 2001 may include electrical control circuitry and electrical readout circuitry, which are not explicitly shown.

[0310] Figure 21A A side view of an optical coherent imager 2100 according to an embodiment of the present disclosure is shown. The optical coherent imager 2100 includes a coherent optical sensor 2101, a polarization transformation separation assembly 2102, and an imaging optical system 2103. The optical coherent imager 2100 may also include other components, including but not limited to those shown for simplicity. Figure 21A Any or more of the laser source, electronic controller, electronic interface, and digital signal processor not explicitly shown in the document.

[0311] Figure 21A The coherent optical sensor 2101 is a sensor that includes a plurality of coherent sensing units disclosed herein. According to some embodiments, the coherent optical sensor 2101 may be located in... Figure 18A , Figure 19A and Figure 20A One of the coherent optical sensors 1800, 1900, and 2000 is shown. An outgoing optical signal for target illumination is emitted from the coherent optical sensor 2101. The outgoing optical signals emitted from different coherent sensing units of the coherent optical sensor 2101 via the imaging optical system 2103 can generate illumination beams at different field-of-view positions, such that each field-of-view position corresponds to a coherent sensing unit of the coherent optical sensor. Figure 21ADetails of the imaging optical system 2103 are shown for illustrative purposes only. Other optical arrangements may be used for the imaging optical system 2103. Depending on the specific design of the coherent sensing unit used in the coherent optical sensor 2101, the polarization transformation separation component 2102 may be, according to some embodiments, Figure 4C , Figure 5A , Figure 5C , Figure 6A , Figure 6C , Figure 10C , Figure 11B , Figure 12A , Figure 13C , Figure 15C , Figure 16C and Figure 17B One of the configurations shown. The polarization transformation separation component 2102 can be used to enable the outgoing optical signal for target illumination emitted from the coherent optical sensor 2101 and the incident optical signal (i.e., the target signal) received by the coherent optical sensor 210 to propagate along a common optical path, wherein the common optical path is located between the component 2102 and the target 2104.

[0312] exist Figure 21A In the diagram, ray 2171 illustrates an example optical path at one field-of-view position of the optical coherent imager 2100, and ray 2172 illustrates an example optical path at another field-of-view position of the optical coherent imager 2100. The imaging optical system 2103 may have at least one image plane. The polarization transformation separation component 2102 may be positioned close to the image plane of the imaging optical system 2103. For example, in... Figure 21A In the imaging optical system 2103, the polarization transformation separation component 2102 is positioned close to the coherent optical sensor 2101, which is positioned at the final image plane 2161 of the imaging optical system 2103.

[0313] Figure 21B Show Figure 21A A close-up view of the imager 2100 near the final image plane 2161. For illustrative purposes, in Figure 21B In the process, the polarization transformation separation component 2102 can be characterized as follows: Figure 6C The polarization transformation separation configuration is shown. (As shown) Figure 21B As shown, for each field-of-view position of the optical coherent imager 2100, the incident optical signals from the target that share a common optical path with respect to the outgoing optical signals can be spatially spaced on the final image plane by the polarization-correlated beam splitter 401. Figure 21BIn the diagram, spatial spacing 2198 is the spatial spacing between the incident and outgoing rays 2171 achieved by polarization-correlated beam splitter 401, and spatial spacing 2199 is the spatial spacing between the incident and outgoing rays 2172 achieved by polarization-correlated beam splitter 401. According to some embodiments, the imaging optical system 2103 may have image spatial telecenty, which makes the spatial spacing of polarization-correlated beam splitter 401 uniform across the field of view of optical coherent imager 2100. The spatial spacing 2198 of rays 2171 can therefore be similar to the spatial spacing 2199 of rays 2172. Furthermore, the angular subtense 2188 of rays 2171 can also be similar to the angular subtense 2189 of rays 2172. In this configuration, the polarization diversity free-space to waveguide couplers of the coherent sensing units in the coherent optical sensor 2101 can be designed to optimally couple with the optical signal based on a common incident angle (e.g., normal incident), a common opposing angle, and (if applicable) a common spacing between the sub-couplers. According to other embodiments, where the imaging optics system 2103 may not have image spatial telecenty, each polarization diversity free-space to waveguide coupler of the coherent sensing units in the coherent optical sensor 2101 can be individually designed to optimally couple with the optical signal, according to the specifications of the polarization transformation separation assembly 2102 and the imaging optics system 2103.

[0314] Figure 21C Shown in Figure 21B The polarization diagrams of example ordinary rays (o-rays) and extraordinary rays (e-rays) in the field of view of the optical coherent imager relative to the polarization-correlated beam splitter 401 on the coherent optical sensor 2101 are shown. Figure 21C In the diagram, polarization 2191 shows an example of o-ray polarization, and polarization 2192 shows an example of e-ray polarization. As an example, according to... Figure 21B The orientation of the optical axis 498 in the xz plane is such that the o-ray polarization is a linear polarization with a dominant component along the y-direction, while the e-ray polarization is a linear polarization with a dominant component along the x-direction. According to some embodiments, the imaging optics system 2103 is precisely telecentric in the image space, and both the o-ray and e-ray polarizations can be uniform across the field of view of the optically coherent imager. According to other embodiments, for example... Figure 21CIn the embodiments shown, when the imaging optics system 2103 is not exactly at the telecentric of the image space, the polarization of the o-ray and e-ray may deviate from uniformity. According to some embodiments, the polarization diversity free space to waveguide couplers of the coherent sensing units in the coherent optical sensor 2101 can be designed where non-uniformity is ignored. According to other embodiments, each polarization diversity free space to waveguide coupler of the coherent sensing units in the coherent optical sensor 2101 can be individually designed to optimally couple with the optical signal according to the variation in polarization of the o-ray and e-ray in the field of view of the imaging optics system 2103.

[0315] Figure 22A A side view of an optical coherent imager 2200 according to another embodiment of the present disclosure is shown. The optical coherent imager 2200 includes a coherent optical sensor 2201, an imaging optics system 2203, and a polarization transformation separation assembly having components arranged together with the optical components of the imaging optics system 220. As illustrated, the polarization transformation separation assembly includes polarization correlation beam splitters 2241 and 2242, a Faraday rotator 2251, a polarization rotator 2252, and a quarter-wave plate 2261. This polarization transformation separation assembly is similar to... Figure 12A and Figure 12B The polarization transformation separation configuration 1210 differs from configuration 1210 in that the use of a polarization-dependent beam splitter 2241 achieves angular displacement instead of the lateral displacement achieved by the polarization-dependent beam splitter 2241 in configuration 1210. According to some embodiments, the polarization-dependent beam splitter 2241 may be a birefringent wedge. Figure 22A In the diagram, ray 2271 shows an example optical path at one field of view position of the optical coherent imager 2200, and ray 2272 shows an example optical path at another field of view position of the optical coherent imager 2200.

[0316] Figure 22B A side view is shown of light rays propagating through a polarization-dependent beam splitter 2241 that achieves angular displacement, and light rays propagating through a polarization-dependent beam splitter 2242 that achieves lateral displacement, according to an embodiment of the present disclosure. Reference Figure 22B The polarization-dependent beam splitter 2242 can produce a lateral displacement of the incident light, which depends on the polarization of the light. For example, in Figure 22B In this configuration, when light passes through the polarization-dependent beam splitter 2242, the x-polarization and y-polarization components of the light are laterally shifted with different displacements. Conversely, the polarization-dependent beam splitter 2241 can produce an angular displacement of the incident light, which depends on the polarization of the light. For example, in... Figure 22B In the process, when light passes through the polarization-dependent beam splitter 2241, the x-polarization component and y-polarization component of the light are angularly shifted at different angles.

[0317] Return to reference Figure 22AThe polarization-correlated beam splitter 2242 is positioned close to the image plane of the imaging optics system 2203, while the polarization-correlated beam splitter 2241 is positioned close to the focal plane of the imaging optics system 2203. The angular displacement of the polarization-correlated beam splitter 2241 on the focal plane can effectively generate a lateral displacement on the image plane. The use of the polarization-correlated beam splitter 2241 offers the advantage of greater flexibility in positioning optical components within the imaging optics system 2203, including but not limited to polarization-correlated beam splitters 2241 and 2242, Faraday rotator 2251, polarization rotator 2252, and quarter-wave plate 2261.

[0318] like Figure 22A As shown, the Faraday rotator 2251, polarization rotator 2252, and quarter-wave plate 2261 can be positioned in the imaging optical system 2203 at locations where the angle of incidence of the light is relatively small (i.e., close to normal incidence). According to some embodiments, for certain applications of optical coherent imaging, some polarization-dependent components may have greater performance tolerances than others. For example, the Faraday rotator 2251, which tolerates different angles of incidence, can be positioned anywhere between the polarization rotator 2252 and the polarization-dependent beam splitter 2242. As another example, the quarter-wave plate 2261 can be positioned where the angle of incidence of the light varies significantly at different field-of-view locations. The quarter-wave plate 2261 can transform linearly polarized outgoing optical signals at normal incidence into circularly polarized optical signals, and transform outgoing optical signals linearly polarized at an angle of incidence different from normal incidence into elliptically polarized optical signals. Therefore, the variation in the incident angle on the quarter-wave plate 2261 at different field-of-view positions may essentially result in differently elliptically polarized light for illumination at different target scene locations, which may not pose a significant problem for related applications of optical coherent imaging. Furthermore, some embodiments of the coherent optical sensor 2201, such as... Figure 20A The coherent optical sensor 2000 shown can achieve dynamic polarization adjustment, which can alleviate the problem of different elliptically polarized light used for illumination of different target scene locations.

[0319] exist Figure 22A In this configuration, the components of the polarization conversion separation assembly are disposed separately from the optical components of the imaging optical system 2203. According to some embodiments, one or more components of the polarization conversion separation assembly may be disposed together with the optical components of the imaging optical system 2203.

[0320] Figure 23 A flowchart illustrating a method for optical coherent imaging using polarization diversity to achieve a shared path for transmitting and receiving optical signals, according to an embodiment of the present disclosure.

[0321] In step 2301, source light is generated from the light source.

[0322] In step 2303, the source light is guided through a waveguide circuit to one or more polarization diversity free space-to-waveguide couplers in the coherent optical sensors of the optical coherent imager. According to some embodiments, guiding the source light through the waveguide circuit can be achieved by controlling an electro-optic switch or a thermo-optic switch in the waveguide circuit using a control system. According to some embodiments, the selection of the polarization diversity free space-to-waveguide coupler to which the source light is guided can be determined by the location of the target scene to be illuminated. More specifically, each target scene location corresponds to a field-of-view location of the optical coherent imager, which in turn corresponds to a polarization diversity free space-to-waveguide coupler in the coherent optical sensors of the optical coherent imager.

[0323] In step 2305, for each selected polarization diversity free space-to-waveguide coupler (referred to herein as a coupler for simplicity) to which the source light is guided, the source light is coupled from outside the coupler into free space to produce outgoing light with a first polarization. Here, free space can refer to vacuum, air, a region above the surface of the coupler, or any homogeneous medium having a length scale much larger than (e.g., at least 10 times) the wavelength of the optical signal propagating therein. According to some embodiments, the polarization diversity free space-to-waveguide coupler can be configured to... Figure 1B Coupler 101 shown and described, regarding Figure 2 Coupler 200 shown and described, regarding Figure 3 Coupler 300 shown and described, regarding Figure 10A Coupler 1000 shown and described, regarding Figure 11A Coupler 1100 shown and described, regarding Figure 13A Coupler 1300 shown and described, regarding Figure 15A Coupler 1500 shown and described, regarding Figure 16A The coupler 1600 shown and described, or about Figure 17A The coupler 1700 shown and described is implemented.

[0324] In step 2307, for the outgoing light emitted from the selected polarization diversity free space to the waveguide coupler, the first polarization of the outgoing light can be transformed to a second polarization via a polarization transformation configuration. The second polarization may be the same as or different from the first polarization. The second polarization may be any of linear polarization, circular polarization, or elliptic polarization. According to some embodiments, the polarization transformation can be achieved by an optical component or a combination of optical components, including but not limited to a Faraday rotator, a polarization rotator, and a quarter-wave plate.

[0325] In step 2307, according to some embodiments, the optical path of the emitted light may be additionally shifted laterally or angularly, or both laterally and angularly. The displacement can be achieved by at least one of, for example, but not limited to, optical path displacement components of a polarization-dependent beam splitter. According to some embodiments, the polarization transformation and optical path displacement operations can be achieved by a combination of optical components including, but not limited to, Faraday rotators, polarization rotators, quarter-wave plates, and polarization-dependent beam splitters. According to some embodiments, such operations can be achieved by, but not limited to... Figure 4C , Figure 5A , Figure 5C , Figure 6A , Figure 6C , Figure 10C , Figure 11B , Figure 12A , Figure 13C , Figure 15C , Figure 16C and Figure 17B This is achieved by at least one of the configurations shown. According to some embodiments, the configuration for such operation may or may not be configured together with other optical components of the imaging optics system. For example, refer to... Figure 22A The polarization transformation configuration with optical path displacement includes components 2241, 2242, 2251, 2252 and 2261 disposed together with the optical components (lenses) of the imaging optical system 2203.

[0326] In step 2309, the transformed outgoing light is guided to one or more targets located at the field of view of the optical coherent imager, the field of view corresponding to the polarization diversity free space-to-waveguide coupler selected according to step 2303. According to some embodiments, the transformed outgoing light can be guided to the target, wherein an additional imaging optics system is positioned between the selected coupler and the target.

[0327] In step 2311, the target may reflect or scatter the transformed outgoing light used to illuminate it. The reflected or scattered light from the target may be received by an optical coherent imager at the imager's field of view, which corresponds to the selected polarization diversity free space-to-waveguide coupler described in step 2309. According to some embodiments, the reflected or scattered light may be received using an additional imaging optics system disposed between the selected coupler and the target. According to some embodiments, the optical imaging system may be the same as the imaging optics system in step 2309.

[0328] In step 2313, the received light reflected or scattered from the target can be transformed using the same polarization transformation configuration as described in step 2307. At each field-of-view location of the imager described in step 2311, the received light may include one or both of a component having a third polarization that is the same as the second polarization of the transformed outgoing light and a fourth polarization that is orthogonal to the third polarization component. At each field-of-view location, the polarization transformation configuration may transform the third polarization of the received light to a fifth polarization that is orthogonal to the first polarization of the outgoing light at that location. Similarly, the polarization transformation configuration may transform the fourth polarization of the received light to a sixth polarization that is orthogonal to the first polarization of the transformed received light. According to some embodiments, at each field-of-view location, the optical path of at least one polarization component of the received light may be additionally shifted by the same optical path shifting component described in step 2307. According to some embodiments, the shifted polarization component of the received light may be one or both of the third and fourth polarizations.

[0329] In step 2315, one or more polarization diversity free space to waveguide couplers can be used to couple the transformed received light from free space to an inner coupling waveguide. According to some embodiments, these polarization diversity free space to waveguide couplers may be the same set of couplers among those used in step 2305 to emit the outgoing polarized light. For each polarization diversity free space to waveguide coupler, at least one inner coupling waveguide that receives some or all of the transformed received light through the coupler is different from the waveguide that guides the source light to the coupler according to step 2303 (i.e., the outer coupling waveguide).

[0330] More specifically, on one hand, according to some embodiments, a polarization diversity free space to waveguide coupler can couple the fifth polarization of the transformed received light, orthogonal to the first polarization of the outgoing light emitted from the coupler, to at least one waveguide different from the outer coupling waveguide. This can be achieved by designing a polarization diversity free space to waveguide coupler that couples the fifth polarization of the transformed received light to an inner coupling waveguide different from the outer coupling waveguide. According to some embodiments, this can be achieved by optical path shifting of the third polarization of the received light, such that the first polarization of the transformed received light can reach the coupler at a spatial location different from the spatial location of the outgoing light emitted from the coupler.

[0331] On the other hand, according to some embodiments, a polarization diversity free space-to-waveguide coupler can couple the transformed received light to at least one waveguide, different from the outer coupling waveguide, with a sixth polarization orthogonal to the fifth polarization of the transformed received light. This can be achieved by optical path displacement of the fourth polarization of the received light, such that the sixth polarization of the transformed received light reaches the coupler at a spatial location different from the spatial location of the emitted light from the coupler. According to some embodiments, the optical path displacements of the third and fourth polarizations of the received light can be achieved using the same optical path displacement components described in step 2313.

[0332] In step 2317, the inner-coupled received light in the inner-coupled waveguide can be detected by a detector positioned near the waveguide coupler in the polarization diversity free space of the inner-coupled transformed received light. The detector can be arranged as a heterodyne detection setup to perform heterodyne detection using local oscillator light provided to the heterodyne detection setup.

[0333] In step 2319, the detected signal can be processed to extract information about the target. The signal processing can be performed by a signal processing unit, which may or may not be part of an optical coherent imager. According to some embodiments, the target information may include, but is not limited to, the target's coordinates and the reflectivity of the target surface. According to some embodiments, the target information may include the distance between the target and the optical coherent imager. According to some embodiments, the target information may include the target's velocity information. According to some embodiments, the distance and velocity information can be obtained by modulating the source light in step 2301 according to the FMCW LIDAR method, and the distance and velocity information can be extracted by performing a Fourier transform on the detected signal.

[0334] For the purposes of describing and defining this disclosure, it should be noted that degree terms (e.g., “substantially,” “slightly,” “approximately,” “comparable,” etc.) may be used herein to indicate the degree of inherent uncertainty attributable to any quantitative comparison, value, measurement, or other representation. Such degree terms may also be used herein to indicate the extent to which a quantitative representation may vary relative to a claimed reference without causing a change in the fundamental function of the subject matter under discussion (e.g., about 10% or less). Unless otherwise stated herein, any numerical values ​​appearing in this disclosure are considered to have been modified to a certain degree (e.g., “approximately”) to reflect their inherent uncertainty.

[0335] Although various embodiments of the present disclosure have been described in detail herein, those skilled in the art will readily understand modifications and other embodiments without departing from the spirit and scope of the present disclosure as set forth in the appended claims.

Claims

1. An optical coherent sensor, comprising a plurality of coherent sensing units and a polarization converter disposed on the coherent sensing units, wherein, Each of the coherent sensing units includes: Polarization diversity optical couplers, which can: Guiding an optical signal having a first polarization state into free space and a first waveguide, and guiding an optical signal having the first polarization state from said free space and the first waveguide; The optical signal having a second polarization state is guided into the free space and the second waveguide, and the optical signal having the second polarization state is guided from the free space and the second waveguide, wherein the first polarization state and the second polarization state are orthogonal; The incident optical signal is separated into a first optical component having the first polarization state and a second optical component having the second polarization state; Guide the first optical component to the first waveguide; and Guide the second optical component to the second waveguide; One or more 2×2 optical couplers, optically coupled to the polarization diversity optical coupler via at least one of the first and second waveguides; and One or more photodetectors, optically coupled to the 2×2 optical coupler.

2. The optical coherence sensor according to claim 1, wherein, The polarization diversity optical coupler includes a first sub-coupler and a second sub-coupler.

3. The optical coherence sensor according to claim 2, wherein, One of the first and second sub-couplers is polarization-dependent and is optimally coupled to an optical signal of a predetermined polarization state, and the other of the first and second sub-couplers is polarization-independent and is optimally coupled to an optical signal of any polarization state.

4. The optical coherence sensor according to claim 2, wherein, The second sub-coupler is disposed on the first sub-coupler and is perpendicularly separated from the first sub-coupler.

5. The optical coherence sensor according to claim 2, wherein, The first sub-coupler and the second sub-coupler are disposed on the photonic substrate and are laterally separated from each other.

6. The optical coherence sensor according to claim 5, wherein, The polarization converter guides the outgoing optical signal from one of the first and second sub-couplers into the optical path in the free space, and separates the incident optical signal from the optical path into a first optical component having the first polarization state and a second optical component having the second polarization state. One or both of the first and second optical components are spatially shifted by the polarization converter, such that the first optical component and the second optical component are respectively incident on the first and second sub-couplers.

7. The optical coherence sensor according to claim 2, wherein, The polarization converter includes at least one polarization-dependent beam splitter.

8. The optical coherence sensor according to claim 1, wherein, The polarization converter includes one or more polarization transducers that rotate a linearly polarized optical signal by a predetermined angle.

9. The optical coherence sensor according to claim 8, wherein, At least one of the polarization converters is a Faraday rotator.

10. The optical coherence sensor according to claim 1, wherein, The polarization converter includes one or more quarter-wave plates.

11. The optical coherence sensor according to claim 2, wherein, The polarization diversity optical coupler also includes a third sub-coupler.

12. The optical coherence sensor according to claim 11, wherein, The first sub-coupler, the second sub-coupler, and the third sub-coupler are disposed on the photonic substrate and are laterally separated from each other.

13. The optical coherent sensor according to claim 11, wherein, The polarization converter guides the outgoing optical signal from one of the first, second, and third sub-couplers into an optical path in free space, and separates the incident optical signal from the optical path into a first optical component having the first polarization state and a second optical component having the second polarization state. One or both of the first and second optical components are spatially shifted by the polarization converter, such that the first and second optical components are respectively incident on two of the first, second, and third sub-couplers.

14. The optical coherence sensor according to claim 11, wherein, The polarization diversity optical coupler also includes a fourth sub-coupler.

15. The optical coherence sensor according to claim 14, wherein, The polarization converter guides the outgoing optical signals from two of the first, second, third, and fourth sub-couplers into an optical path in free space, and separates the incident optical signals from the optical path into a first optical component having the first polarization state and a second optical component having the second polarization state. One or both of the first and second optical components are spatially shifted by the polarization converter, such that the first and second optical components are respectively incident on two of the first, second, third, and fourth sub-couplers.

16. An optical coherent imager, comprising the optical coherent sensor according to claim 1 and an imaging optical system including a plurality of lenses, wherein, The imaging optical system is configured such that the optical coherence sensor is located near the image plane of the imaging optical system.

17. A method for optical coherent imaging, implemented based on the optical coherent imager according to claim 16, the method comprising: One or more outgoing optical signals are emitted from the optical coherent imager along one or more optical paths toward one or more targets, and the one or more optical paths correspond to one or more field-of-view positions of the optical coherent imager, wherein different coherent sensing units correspond to different field-of-view positions; The optical coherence imager receives one or more incident optical signals reflected from the target illuminated by the outgoing optical signal along the optical path; The polarization converter of the optical coherent imager converts each of the incident optical signals into a first optical component having a first polarization state and a second optical component having a second polarization state, wherein the first polarization state and the second polarization state are orthogonal. as well as One or more polarization diversity optical couplers on the optical coherent imager guide the first and second optical components of the incident optical signal to one or more photodetectors of the optical coherent imager, so as to perform heterodyne detection using local oscillator light at each field-of-view location of the optical coherent imager, thereby determining information about the target at the field-of-view location.

18. The method according to claim 17, wherein, The emission of the emitted optical signal includes: Generate one or more source optical signals from a light source; The source optical signal is converted into the emitted optical signal via the polarization diversity optical coupler, wherein each emitted optical signal has a first emission polarization state; and The emitted optical signal is emitted from the polarization diversity optical coupler.

19. The method of claim 18, further comprising, after transmitting the outgoing optical signal from the polarization diversity optical coupler, transforming each of the outgoing optical signals from the first transmission polarization state to the second transmission polarization state via the polarization converter of the optical coherence imager.

20. The method of claim 17, wherein, Converting the incident optical signal includes rotating the first polarization state of each of the incident optical signals by a first predetermined polarization angle and rotating the second polarization state of each of the incident optical signals by a second predetermined polarization angle.

21. The method according to claim 19, wherein, Converting the incident optical signal includes spatially shifting at least one of a first component and a second component of each of the incident optical signals according to the first polarization state and the second polarization state, such that the first component and the second component are respectively incident on the first sub-coupler and the second sub-coupler of each of the polarization diversity optical couplers.

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