Silicon-based optoelectronic chips and lidar

Abstract

Silicon-based optoelectronic chips and lidar are disclosed. A silicon-based optoelectronic chip can include a reference light stabilization link, an optical phase-locked link, a switching switch link, and a frequency shift tuning and beat measurement link. These links enable on-chip integration of various devices, thereby improving the integration and reliability of a seed light source stabilization scheme.

Description

TECHNICAL FIELD

[0001] The present application relates generally to lidar, and specifically to frequency stabilization of a lidar seed source. BACKGROUND

[0002] In the field of space-borne room temperature gas lidar, in order to achieve high enough gas detection accuracy, the path integral differential absorption (PIDA) lidar needs a seed light source with high optical frequency stability. The frequency stability of existing lasers cannot directly meet the use requirements of lidar.

[0003] The currently used laser frequency stabilization method includes a pseudo-synchronous digital hierarchy (PDH) frequency stabilization loop based on a gas absorption cell, which provides temperature control feedback for the laser working at the reference wavelength. The lasers working at other wavelengths take the reference wavelength as the frequency reference benchmark, and realize optical frequency stability by means of an optical phase-locked loop (Du Juan, Research on Precise Control Technology of Laser Frequency for Space-borne Lidar[D], University of the Chinese Academy of Sciences, 2018). The currently used seed light source frequency stabilization module includes discrete devices such as a phase modulator, a PIN photodetector, an acousto-optic modulator, a magneto-optic switch, and a fiber coupler. The volume of the frequency stabilization module built using discrete devices is too large. In recent years, domestic and foreign research institutions have begun to try to use integrated optoelectronic technology to carry out on-chip integration research of space-borne lidar payloads.

[0004] The currently reported frequency stabilization chip of lidar seed light source is based on indium phosphide platform, and the chip size is 0.9mm*10.7mm. Two sampled grating distributed Bragg reflector (SGDBR) lasers are made on the indium phosphide wafer, which are divided into master laser and slave laser. The master laser realizes frequency stabilization by means of the PDH frequency stabilization loop composed of a phase modulator, a carbon dioxide absorption cell, a detector and peripheral circuits, and provides a stable optical reference frequency for the fast-tunable slave laser (Stephen M, Klamkin J, Coldren L, et al. Integrated Micro-Photonics for Remote Earth Science Sensing (Impress) Lidar [C] / / IGARSS 2019-2019 IEEE International Geoscience and Remote Sensing Symposium. IEEE, 2019.). The optical chip realizes the on-chip integration of the seed light source including the laser, but the optical frequency stability of the indium phosphide-based SGDBR laser is poor, which cannot meet the demand of high-precision detection of IPDA lidar. In addition, the chip does not consider the central frequency stability of the lidar pulsed light, so it is not enough for satellite remote sensing.

[0005] There is a need in the art for a frequency stabilization scheme of lidar seed light source with high frequency stability and high integration. SUMMARY

[0006] In order to realize the frequency stabilization scheme of lidar seed light source with high frequency stability and high integration, the present application is provided.

[0007] According to one application of the present application, there is provided a silicon-based optoelectronic chip comprising: a reference light stabilization link configured to: receive reference light emitted by a reference laser; provide a feedback control signal for stabilization of the reference laser by an absorption cell method; an optical phase-locked loop link configured to: receive first light emitted by a first laser and second light emitted by a second laser of a seed light source; combine a portion of the first light and a portion of the second light with a portion of the reference light, respectively, and generate beat frequency signals for optical phase-locked by optical detection; a switching link configured to: control optical intensity modulation of another portion of the first light and another portion of the second light based on switching actions that are complementary in time domain, to generate corresponding first and second optical intensity modulated light; combine a portion of the first optical intensity modulated light and a portion of the second optical intensity modulated light, and polarization split the combined light to generate corresponding first and second polarization light; a frequency shift tuning and beat frequency measurement link configured to: single sideband modulate a portion of the first light to generate frequency shift light; combine a portion of the frequency shift light with the first polarization light and photoelectrically detect the combined light to generate a signal for monitoring a center frequency of the first laser.

[0008] The silicon-based optoelectronic chip as described above, wherein the reference light stabilization link comprises: a cascaded phase modulator configured to modulate a portion of the reference light, and the reference light stabilization link is configured to: pass the modulated portion of the reference light through an absorption cell outside the silicon-based optoelectronic chip, and receive a signal input after passing through the absorption cell.

[0009] The silicon-based optoelectronic chip as described in any of the above, wherein the cascaded phase modulator comprises doped silicon waveguides connected in series and comprises lumped electrodes.

[0010] The silicon-based optoelectronic chip as described in any of the above, wherein the reference light stabilization link further comprises: a silicon-based PIN photodetector configured to detect the signal input after passing through the absorption cell to generate the feedback control signal.

[0011] The silicon-based optoelectronic chip as described in any of the above, wherein the silicon-based PIN photodetector is a lateral photodetector.

[0012] The silicon-based optoelectronic chip as described in any of the above, wherein the optical phase-locked loop link comprises: silicon-based NIP photodetectors configured to detect light for combining a portion of the first light with a portion of the reference light and a portion of the second light with a portion of the reference light, respectively, to generate corresponding beat frequency signals.

[0013] The silicon-based optoelectronic chip of any of the above, wherein the switching link comprises thermo-optic switches for optically modulating the other portion of the first light and the other portion of the second light, respectively.

[0014] The silicon-based optoelectronic chip of any of the above, wherein the thermo-optic switches are M-Z thermo-optic switches.

[0015] The silicon-based optoelectronic chip of any of the above, wherein the switching link further comprises silicon-based PIN photodetectors for detecting optical intensities of the first and second intensity-modulated lights, respectively.

[0016] The silicon-based optoelectronic chip of any of the above, wherein the frequency-shift tuning and beat-frequency measurement link comprises a silicon-based single-sideband modulator for performing the single-sideband modulation.

[0017] The silicon-based optoelectronic chip of any of the above, wherein the silicon-based single-sideband modulator comprises a silicon-based electro-optic phase modulator and a thermo-optic phase shifter.

[0018] The silicon-based optoelectronic chip of any of the above, wherein the frequency-shift tuning and beat-frequency measurement link further comprises a silicon-based PIN photodetector for detecting a portion of the frequency-shifted light to generate a signal for monitoring an operating point of the silicon-based single-sideband modulator.

[0019] The silicon-based optoelectronic chip of any of the above, wherein the first light is Online light and the second light is Offline light.

[0020] According to another aspect of the present application, there is provided a lidar comprising a seed light source and the silicon-based optoelectronic chip of any of the above, the silicon-based optoelectronic chip being coupled with the seed light source.

[0021] The silicon-based optoelectronic chip according to the present application improves the on-chip integration of devices required for frequency stabilization of a seed light source, and can bring several benefits of separating the frequency stabilization module from the seed light source. BRIEF DESCRIPTION OF DRAWINGS

[0022] Embodiments of the present application are described in conjunction with the appended drawings, in which:

[0023] Figure 1 A block diagram of a silicon-based optoelectronic chip according to an embodiment of the present application is shown.

[0024] Figure 2 A circuit structure schematic of a silicon-based optoelectronic chip according to an embodiment of the present application is shown.

[0025] Figure 3A block diagram of a lidar according to embodiments of the application is shown. DETAILED DESCRIPTION

[0026] In the following description, numerous specific details are set forth. However, it is understood that embodiments of the application can be practiced without these specific details. In other instances, well-known circuits, structures and techniques have not been shown in detail in order not to obscure the understanding of this description.

[0027] According to one application of the application, a silicon-based optoelectronic chip is provided.

[0028] Figure 1 A block diagram of a silicon-based optoelectronic chip 100 according to embodiments of the application is shown. The silicon-based optoelectronic chip 100 can be used for frequency stabilization of a lidar seed laser. In Figure 1 In the figure, each link on the silicon-based optoelectronic chip 100 is represented by a bold arrow, and the flow direction and interaction of each signal is represented by a thin line arrow.

[0029] The silicon-based optoelectronic chip 100 can include a reference light frequency stabilization link 110, an optical phase-locked link 130, a switching switch link 150, and a frequency shift tuning and beat frequency measurement link 170. By integrating the devices for frequency stabilization of a seed laser on the silicon-based optoelectronic chip 100, the integration level of the seed laser is effectively improved. At the same time, by designing the frequency stabilization devices to be separate from the seed laser, the challenge of chip heat dissipation by high-power active devices is avoided, and the optoelectronic links on the silicon-based optoelectronic chip 100 according to embodiments of the application can also be used for other lidar light sources, thus also having advantages in terms of power consumption and scalability of the lidar.

[0030] The reference light frequency stabilization link 110 can be used to receive reference light 111 emitted by a reference laser (not shown), and to provide a feedback control signal 112 for frequency stabilization of the reference laser by the absorption cell method. The feedback control signal 112 can be used to stabilize the optical center frequency of the reference light 111 at the center of the carbon dioxide R18 absorption peak.

[0031] In some embodiments, the reference light stabilization link 110 can include a cascaded phase modulator (e.g., a cascaded carrier-depletion phase modulator) for modulating a portion of the received reference light 111 to generate modulated light 113. The reference light stabilization link 110 can be configured to pass the modulated light 113 through an absorption cell (e.g., a carbon dioxide gas absorption cell, not shown) external to the silicon-based optoelectronic chip 100 and receive a signal 114 after passing through the absorption cell. By employing a cascaded phase modulator, the modulation depth is effectively increased. In some embodiments, the cascaded phase modulator described above can include silicon-doped waveguides connected in series and include lumped electrodes. Using silicon-doped waveguides and lumped electrodes, a silicon-based phase modulator with high modulation depth and high bandwidth (e.g., up to 1 GHz) can be achieved.

[0032] In some embodiments, the reference light stabilization link 110 can include a silicon-based PIN photodetector (e.g., a germanium-silicon PIN photodetector) for detecting the signal 114 after passing through the absorption cell and generating a feedback control signal 112 based thereon. In some embodiments, the silicon-based PIN photodetector can be a lateral photodetector. Employing a silicon-based PIN photodetector further facilitates the integration of photodetector devices on a silicon-based optoelectronic chip.

[0033] The optical phase-locked link 130 can include one link for each of the lights emitted by the two lasers (not shown) of the seed light source. Specifically, the optical phase-locked link 130 can receive the lights 131, 132 emitted by the two lasers of the seed light source, respectively, combine a portion of the light 131 with a portion 115 of the reference light received in the reference light stabilization link 110, generate a beat signal 135 for optical phase-locked detection, and combine a portion of the light 132 with a portion 116 of the reference light received in the reference light stabilization link 110, generate a beat signal 136 for optical phase-locked detection. The lights 131, 132 each take the reference light 111 as a frequency reference, thereby achieving optical frequency stabilization of themselves by means of an optical phase-locked loop.

[0034] In some embodiments, the light 131 can be an Offline light and the light 132 can be an Online light. In alternative embodiments, the light 131 can be an Online light and the light 132 can be an Offline light. Here, the Online light and the Offline light refer to continuous lights respectively generated by the two lasers (e.g., Distributed Feedback (DFB)) of the seed light source, which can have wavelengths of 1572.024 nm and 1572.085 nm, respectively.

[0035] In some embodiments, the optical phase-locked link 130 can include two respective NIP photodetectors, one of which is used to detect light that is a combination of a portion of the light 131 and a portion 115 of the reference light received in the reference light stabilization link 110 to produce a beat frequency signal 135, and the other of which is used to detect light that is a combination of a portion of the light 132 and a portion 116 of the reference light received in the reference light stabilization link 110 to produce a beat frequency signal 136. The use of silicon-based NIP photodetectors further facilitates the integration of photodetector devices on silicon-based optoelectronic chips.

[0036] The switching link 150 can be used to control the optical intensity modulation of the portion 133 of the light 131 and the portion 134 of the light 132 to produce corresponding optically intensity modulated light 151, 152 based on switching actions that are complementary in the time domain. The switching link 150 can also be used to combine and polarization split the optically intensity modulated light 151, 152 to produce corresponding polarized light 155.

[0037] In some embodiments, the portion 153 of the light 133 and the portion 154 of the light 134 in the switching link 150 can be used for monitoring.

[0038] In some embodiments, the switching link 150 can include thermo-optic switches for optical modulation of the light 133, 134, respectively. The use of thermo-optic switches in place of traditional magneto-optic switches can further facilitate the integration of devices on silicon-based chips. In some embodiments, the thermo-optic switches can be Mach-Zehnder (M-Z) thermo-optic switches.

[0039] In some embodiments, the switching link 150 can include silicon-based PIN photodetectors for detecting the optically intensity modulated light 151, 152, respectively. The use of silicon-based PIN photodetectors further facilitates the integration of photodetector devices on silicon-based optoelectronic chips.

[0040] The frequency-shifted tuning and beat-note measurement link 170 can be used to perform single-sideband modulation on a portion 137 of the light 132 to produce frequency-shifted light 171. The frequency-shifted tuning and beat-note measurement link 170 can also be used to combine a portion 172 of the polarized light 155 corresponding to the light 132 and a portion of the frequency-shifted light 171, and perform photodetection to produce a signal 173 for monitoring the center frequency of the laser emitting the light 132. This signal 173 can be further provided to the optical parametric oscillator as a basis for feedback control of the seed light source for frequency stabilization. In some embodiments, the light 131 can be Offline light, and the light 132 can be Online light. This is because the Online light of the seed light source is more accurate, and based on this light, the seed light source is stabilized to achieve more accurate results. Of course, one skilled in the art can also use the light Online light for the light 131 and Offline for the light 132 to stabilize the seed light source based on the Offline light.

[0041] In some embodiments, the frequency-shifted tuning and beat-note measurement link 170 can include a silicon-based single-sideband modulator for performing the single-sideband modulation described above. The use of a silicon-based single-sideband modulator further facilitates the integration of the modulating device on a silicon-based optoelectronic chip. In some embodiments, the silicon-based single-sideband modulator can include a silicon-based electro-optic phase modulator and a thermo-optic phase shifter. The use of a silicon-based electro-optic phase modulator in place of an acousto-optic modulator facilitates further integration of the device on a silicon-based chip.

[0042] In some embodiments, the frequency-shifted tuning and beat-note measurement link 170 can include a silicon-based PIN photodetector for detecting a portion of the frequency-shifted light 171 to produce a signal 174 for monitoring the operating point of the silicon-based single-sideband modulator. The use of a silicon-based PIN photodetector further facilitates the integration of the photodetecting device on a silicon-based optoelectronic chip.

[0043] Figure 2 A circuit structure schematic diagram of a silicon-based optoelectronic chip 200 according to an embodiment of the present application is shown. The silicon-based optoelectronic chip 200 can be used for frequency stabilization of a laser radar seed light source.

[0044] The silicon-based optoelectronic chip 200 can include end-face couplers 201-1 to 201-7 for receiving signals from outside the silicon-based optoelectronic chip 200 or transmitting signals from the silicon-based optoelectronic chip 200 to outside.

[0045] The silicon-based optoelectronic chip 200 can include directional couplers 202-1 to 202-6 for splitting received light by a predetermined ratio.

[0046] The silicon-based optoelectronic chip 200 can include multi-mode interference (MMI) couplers 203-1 to 203-5 for beam combining and mixing of received light beams.

[0047] The silicon-based optoelectronic chip 200 can include a cascaded phase modulator 204. In some embodiments, the cascaded phase modulator 204 can be a cascaded carrier-depletion silicon-based electro-optic phase modulator. In some embodiments, the cascaded phase modulator 204 can include (e.g., two) doped silicon waveguides connected in series and include lumped electrodes. As such, a silicon-based phase modulator with high modulation depth and high bandwidth (e.g., up to 1 GHz) can be achieved. As an example, the modulation region of the cascaded phase modulator 204 can be cascaded by two doped silicon waveguides with a length of 0.3 mm in optical path, although the scope of the application is not limited in this respect. As an example, the cascaded phase modulator 204 can employ a lumped G-S-G copper electrode design, where "G" represents ground and "S" represents signal, although the scope of the application is not limited in this respect.

[0048] The silicon-based optoelectronic chip 200 can include tunable optical attenuators 205-1, 205-2 for attenuating the optical intensity of received light.

[0049] The silicon-based optoelectronic chip 200 can include thermo-optic switches 206-1, 206-2. The use of thermo-optic switches 206-1, 206-2 in place of traditional magneto-optic switches can further facilitate device integration on a silicon-based chip. In some embodiments, the thermo-optic switches 206-1, 206-2 can be M-Z thermo-optic switches. As an example, the thermo-optic switches 206-1, 206-2 can employ an MZI structure, the output intensity of the thermo-optic switches 206-1, 206-2 can be controlled by a direct current level, and the switching frequency can be up to 5 kHz with an extinction ratio higher than 10 dB.

[0050] The silicon-based optoelectronic chip 200 can include NIP-type photodetectors 207-1, 207-2 for detecting received optical signals.

[0051] The silicon-based optoelectronic chip 200 can include PIN-type photodetectors 208-1 to 208-5 for detecting received optical signals. In some embodiments, the PIN-type photodetectors 208-1 to 208-5 can be germanium-silicon PIN-type photodetectors. In some embodiments, the PIN-type photodetectors 208-1 to 208-5 can be germanium-silicon lateral-type photodetectors. As an example, the PIN-type photodetectors 208-1 to 208-5 can employ a G-S copper electrode design, although the scope of the application is not limited in this respect. As an example, the detector length of the PIN-type photodetectors 208-1 to 208-5 can be 20 μιη, although the scope of the application is not limited in this respect.

[0052] The silicon-based optoelectronic chip 200 can include a silicon-based single sideband modulator 209 for performing single sideband modulation on the received light to generate frequency-shifted light. In some embodiments, the silicon-based single sideband modulator 209 can include a silicon-based electro-optic phase modulator and a thermo-optic phase shifter. The use of a silicon-based electro-optic phase modulator in place of an acousto-optic modulator facilitates further integration of the device on a silicon-based chip. As an example, the silicon-based single sideband modulator 209 can include two 1x2 MMI couplers, two M-Z carrier-depletion silicon-based electro-optic modulators, and three thermo-optic phase shifters, although the scope of the application is not limited in this respect. As an example, the silicon-based single sideband modulator 209 can employ a G-S-G-S-G-S-G-S-G coplanar waveguide electrode design, and the coplanar waveguide electrode ends include eight titanium nitride matching resistors, although the scope of the application is not limited in this respect. As an example, the titanium nitride matching resistors can have a resistance of 52 Ω and a size of 144.3 μιη x 30 μιη, the purpose of this design being to ensure impedance matching while preventing the input signal of large voltage swing from causing the titanium nitride metal to fuse, although the scope of the application is not limited in this respect.

[0053] The silicon-based optoelectronic chip 200 can include a polarization beam splitter 210 for splitting the received light according to polarization mode.

[0054] The connection relationship of the elements of the silicon-based optoelectronic chip 200 is described below according to channel division.

[0055] In some embodiments, the silicon-based optoelectronic chip 200 can include a reference light modulation channel, an absorption cell signal detection channel, an Offline emission channel, an Online emission channel, an Offline beat frequency detection channel, an Online beat frequency detection channel, and an Online pulsed light beat frequency detection channel.

[0056] The reference light modulation channel can include an end-face coupler 201-2, a directional coupler 202-2, a cascaded phase modulator 204, and an end-face coupler 201-3. The end-face coupler 201-2 is connected to the input end of the directional coupler 202-2, 90% of the light at the output end of the directional coupler 202-2 is connected to the input end of the cascaded phase modulator 204, and the output end of the cascaded phase modulator 204 is connected to the end-face coupler 201-3.

[0057] The absorption cell signal detection channel can include an end-face coupler 201-5 and a PIN photodetector 208-1. The end-face coupler 201-5 is connected to the input end of the PIN photodetector 208-1.

[0058] The offline transmission channel can include an end-face coupler 201-1, a directional coupler 202-1, a thermo-optic switch 206-1, a directional coupler 202-5, a PIN photodetector 208-3, an MMI coupler 203-5, a polarization beam splitter 210, and an end-face coupler 201-6. The end-face coupler 201-1 is connected to the input end of the directional coupler 202-1, 90% intensity light at the output end of the directional coupler 202-1 is connected to the thermo-optic switch 206-1, the thermo-optic switch 206-1 is connected to the input end of the directional coupler 202-5, 10% intensity light at the output end of the directional coupler 202-5 is connected to the input end of the PIN photodetector 208-3, 90% intensity light is connected to the input end of the MMI coupler 203-5, the MMI coupler 203-5 is connected to the input end of the polarization beam splitter 210, and the TE mode output end of the polarization beam splitter 210 is connected to the end-face coupler 201-6.

[0059] The offline beat frequency detection channel can include an end-face coupler 201-1, a directional coupler 202-1, an MMI coupler 203-2, an end-face coupler 201-2, a directional coupler 202-2, an MMI coupler 203-3, an adjustable optical attenuator 205-1, and a NIP photodetector 207-1. The waveguide end of the end-face coupler 201-1 is connected to the input end of the directional coupler 202-1, 10% intensity light at the output end of the directional coupler 202-1 is connected to one input end of the MMI coupler 203-3, the end-face coupler 201-2 is connected to the input end of the directional coupler 202-2, 10% intensity light at the output end of the directional coupler 202-2 is connected to the input end of the MMI coupler 203-2, one output end of the MMI coupler 203-2 is connected to the other input end of the MMI 203-3, the output end of the MMI coupler 203-3 is connected to the input end of the adjustable optical attenuator 205-1, the output end of VOA1 of the adjustable optical attenuator 205-1 is connected to the input end of the NIP photodetector 207-1.

[0060] The online beat frequency detection channel can include an end face coupler 201-4, an MMI coupler 203-1, a directional coupler 202-3, an MMI coupler 203-2, an end face coupler 201-2, a directional coupler 202-2, an MMI coupler 203-4, an adjustable optical attenuator 205-2, and a NIP type photoelectric detector 207-2. The waveguide end of the end face coupler 201-4 is connected to the input end of the MMI coupler 203-1, one output end of the MMI coupler 203-1 is connected to the input end of the directional coupler 202-3, 10% intensity light of the output end of the directional coupler 202-3 is connected to one input end of the MMI coupler 203-4, the waveguide end of the end face coupler 201-2 is connected to the input end of the directional coupler 202-2, 10% intensity light of the output end of the directional coupler 202-2 is connected to the input end of the MMI coupler 203-2, the other output end of the MMI coupler 203-2 is connected to the other input end of the MMI coupler 203-4, the output end of the MMI coupler 203-4 is connected to the input end of the VOA of the adjustable optical attenuator 205-2, and the VOA output end of the adjustable optical attenuator 205-2 is connected to the input end of the NIP type photoelectric detector 207-2.

[0061] The online transmission channel can include an end face coupler 201-4, an MMI coupler 203-1, a directional coupler 202-3, a thermo-optic switch 206-2, a directional coupler 202-6, a PIN type photoelectric detector 208-4, an MMI coupler 203-5, a polarization beam splitter 210, and an end face coupler 201-6. The waveguide end of the end face coupler 201-4 is connected to the input end of the MMI coupler 203-1, one output end of the MMI coupler 203-1 is connected to the input end of the directional coupler 202-3, 90% intensity light of the output end of the directional coupler 202-3 is connected to the input end of the thermo-optic switch 206-2, the output end of the thermo-optic switch 206-2 is connected to the input end of the directional coupler 202-6, 10% intensity light of the output end of the directional coupler 202-6 is connected to the PIN type photoelectric detector 208-4, 90% intensity light of the output end of the directional coupler 202-6 is connected to the other input end of the MMI coupler 203-5, the output end of the MMI coupler 203-5 is connected to the input end of the polarization beam splitter 210, and the TE mode output end of the polarization beam splitter 210 is connected to the waveguide end of the end face coupler 201-6.

[0062] The online pulse light beat frequency monitoring channel can include an end face coupler 201-4, an MMI coupler 203-1, a silicon-based single sideband modulator 209, a directional coupler 202-4, a PIN photodetector 208-2, a PIN photodetector 208-5, an MMI coupler 203-4, and an end face coupler 201-7. The waveguide end of the end face coupler 201-4 is connected to the input end of the MMI coupler 203-1, another output of the MMI coupler 203-1 is connected to the input end of the silicon-based single sideband modulator 209, the output end of the silicon-based single sideband modulator 209 is connected to the input end of the directional coupler 202-4, 10% intensity light of the output end of the directional coupler 202-4 is connected to the input end of the PIN photodetector 208-5, 90% intensity light of the output end of the directional coupler 202-4 is connected to one input end of the MMI coupler 203-4, the waveguide end of the end face coupler 201-7 is connected to another input end of the MMI coupler 203-4, and the output end of the MMI coupler 203-4 is connected to the input end of the PIN photodetector 208-2.

[0063] The basic working principle of the silicon-based optoelectronic chip 200 is described below according to link division, which is consistent with the above description of the silicon-based optoelectronic chip 200. Figure 1 The description of each link is consistent with the above description.

[0064] The silicon-based optoelectronic chip 200 can include a reference light frequency stabilization link, an optical phase-locked link, a switching switch link, and a frequency shift tuning and beat frequency measurement link.

[0065] The working principle of the reference light stable frequency link is as follows: the continuous light of 1572.018 nm generated by a DFB laser is taken as the reference light 220, which is coupled into the silicon-based optoelectronic chip 200 through the end face coupler 201-2. The light is split into two light beams with a light intensity ratio of 90:10 through the directional coupler 202-2, 90% of the light intensity enters the cascaded phase modulator 204, and 10% of the light intensity enters the MMI coupler 203-2. The collective electrode of the cascaded phase modulator 204 is inputted with an electrical signal with a frequency in the range of 100-200 MHz to make phase modulation on the reference light 220. The modulated reference light is coupled into the optical fiber through the end face coupler 201-3 to leave the silicon-based optoelectronic chip, forming a signal 221. The signal 221 passes through the carbon dioxide gas absorption cell 222 outside the silicon-based optoelectronic chip 200, the signal 223 passing through the carbon dioxide gas absorption cell 222 passes through the optical fiber coupling to enter the end face coupler 201-5, thereby entering the silicon-based optoelectronic chip 200, and is finally received and detected by the PIN photodetector 208-1. The photoelectric signal generated by the PIN photodetector 208-1 can be used for the temperature feedback control signal of the reference laser emitting the reference light 220 after a series of processing such as mixing and low-pass filtering, and finally the optical center frequency of the reference light 220 is stabilized at the center of the carbon dioxide R18 absorption peak.

[0066] The working principle of the optical phase-locked link is as follows: two DFB lasers of the seed light source generate continuous light of 1572.024 nm and 1572.085 nm as Online light 231 and Offline light 230, respectively. Offline light 230 is coupled into end-face coupler 201-4 through an optical fiber and enters silicon-based optoelectronic chip 200, and is split into two beams of equal light intensity by MMI coupler 203-1. One of the beams is split into two beams with a light intensity ratio of 90:10 by directional coupler 202-3, 90% of the intensity of the light enters thermo-optic switch 206-2, and 10% of the intensity of the light enters MMI coupler 103-4. Offline light 230 is coupled into end-face coupler 201-1 through an optical fiber and enters silicon-based optoelectronic chip 200, and is split into two beams with a light intensity ratio of 90:10 by directional coupler 202-1, 90% of the intensity of the light enters thermo-optic switch 206-1, and 10% of the intensity of the light enters MMI coupler 203-3. MMI coupler 203-2 splits it into two beams of equal light intensity, which enter MMI coupler 203-3 and MMI coupler 203-4, respectively. Because there is a certain wavelength difference between reference light 220 and Online light 231 and Offline light 230, when reference light 220 and Online light 231 and Offline light 230 enter NIP photodetector 207-1, a difference frequency signal with a frequency of about 760 MHz is generated, and when reference light 220 and Online light 231 and Online light 231 enter NIP photodetector 207-2, a difference frequency signal with a frequency of about 8.08 GHz is generated. The above-mentioned difference frequency signals generated by NIP photodetectors 207-1 and 207-2 provide the feedback information required for laser temperature control for the optical phase-locked loop, thereby realizing the stability of the optical frequency of the laser. In some embodiments, adjustable optical attenuators 105-1 and 105-2 are respectively connected in front of NIP photodetectors 107-1 and 107-2, and the purpose is to adjust the photoelectric signal to a suitable intensity to ensure that the signal can be linearly amplified by the transimpedance amplifier circuit.

[0067] The working principle of switching the optical link is as follows: the Online light 231 and the Offline light 230 need to pass through the thermo-optic switch 206-1, 206-2 respectively, and are split into two light paths with a light intensity ratio of 90:10 by the corresponding directional coupler 202-5, 202-6. The 10% intensity light enters the PIN photodetector 208-3 for monitoring. The 90% intensity light enters the MMI coupler 203-5, and only the TE mode light is reserved after passing through the biased beam splitter 210, and is further coupled by the end face coupler 201-6 as the signal 240 and output to the outside of the silicon-based optoelectronic chip 200 through the optical fiber. As an example, the thermo-optic switch 206-1, 206-2 can realize the switching modulation of light intensity by inputting a direct current square wave with an interval of 200 μs, and the switching actions of the thermo-optic switch 206-1, 206-2 can be complementary in the time domain to realize the alternate output of the two light signals.

[0068] The working principle of the frequency shift tuning and beat frequency measurement link is as follows: the other path of the Online light split by the MMI coupler 203-1 passes through the silicon-based single sideband modulator 209. The modulated Online light contains multiple harmonic components in frequency, of which the first order (i.e. +1 or -1) harmonic occupies most of the light intensity, and the modulation frequency is 400 MHz, that is, the Online frequency-shifted light. In some embodiments, the silicon-based single sideband modulator 209 can be built according to the architecture of an optical IQ modulator, and single sideband modulation can be realized by controlling the bias voltage of three thermo-optic phase shifters and traveling wave electrodes. The working point of the single sideband modulation needs to be feedback controlled, so a directional coupler 202-4 can be cascaded at the output end of the silicon-based single sideband modulator 209, which allocates 10% intensity light signal to the PIN photodetector for working point monitoring of the silicon-based single sideband modulator 209, and makes 90% intensity light signal enter the input end of the MMI coupler 103-4. When the value of the light signal of the PIN photodetector single output section is lower than a certain threshold, it is considered that the silicon-based single sideband modulator 209 is in normal working state. The Online light emitted by the above-mentioned Online emission channel passes through the optical parametric oscillator compression and amplification to become Online pulsed light, and the center frequency of the Online pulsed light can drift. Therefore, the signal 250 corresponding to the Online light needs to be split from the signal 240, and enters the silicon-based optoelectronic chip 200 through the end face coupler 201-7 to input to the other input end of the MMI coupler 203-4. The Online frequency-shifted light and the Online pulsed light are combined to enter the NIP photodetector 208-2, and the photoelectric signal generated contains a direct current component and a 400 MHz and harmonic component, thereby realizing the monitoring of the center frequency of the Online pulsed light.

[0069] It is noted that the elements of the silicon-based optoelectronic chip 200 described above, the way they are connected, the parameter settings, etc. are merely exemplary and a person skilled in the art is able to use various alternative implementations based on the working principles of the described links.

[0070] According to another aspect of the present application, a lidar is provided.

[0071] Figure 3 A block diagram of a lidar 300 according to an embodiment of the present application is shown.

[0072] The lidar 300 can comprise a seed light source 310 and a silicon-based optoelectronic chip 330 coupled thereto. The silicon-based optoelectronic chip 330 can be the silicon-based optoelectronic chip 100 described above in connection with Figure 1 the silicon-based optoelectronic chip 200 described above in connection with Figure 2 The lidar 300 can achieve frequency stabilization of the seed light source 310 based on various feedback control signals generated by the silicon-based optoelectronic chip 330.

[0073] The above described embodiments, implementations and aspects have been described in order to allow easy understanding of the present application and do not limit the present application. On the contrary, the application is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims, which scope should be accorded the broadest interpretation so as to encompass all such modifications and equivalent structure as is permitted under the law.

Claims

1. A silicon-based optoelectronic chip comprising: a reference light stabilization link configured to: receive a reference light emitted by a reference laser; and provide a feedback control signal for frequency stabilization of the reference laser by an absorption cell method; and an optical phase-locked loop link configured to: receive a first light emitted by a first laser and a second light emitted by a second laser of a seed light source; combine a portion of the first light and a portion of the second light with a portion of the reference light, respectively, and generate a beat frequency signal for optical phase-locked by optical detection; and a switching link configured to: control optical intensity modulation of another portion of the first light and another portion of the second light based on switching actions that are complementary in time domain, to generate corresponding first and second optical intensity modulated lights; combine a portion of the first optical intensity modulated light and a portion of the second optical intensity modulated light, and polarization split the combined light to generate corresponding first and second polarization lights; and a frequency shift tuning and beat frequency measurement link configured to: single sideband modulate a portion of the first light to generate a frequency shifted light; combine a portion of the frequency shifted light with the first polarization light and photoelectrically detect the combined light to generate a signal for monitoring a center frequency of the first laser. 2.The silicon-based optoelectronic chip of claim 1, wherein: the reference light stabilization link comprises: a cascaded phase modulator configured to modulate a portion of the reference light, and the reference light stabilization link is configured to:

3. The silicon-based optoelectronic chip of claim 2, wherein, pass the modulated portion of the reference light through an absorption cell outside the silicon-based optoelectronic chip, and receive a signal input after passing through the absorption cell. the cascaded phase modulator comprises doped silicon waveguides connected in series and comprises lumped electrodes. 4.The silicon-based optoelectronic chip of claim 2, wherein: the reference light stabilization link further comprises: a silicon-based PIN photodetector configured to detect the signal input after passing through the absorption cell to generate the feedback control signal. 5.The silicon-based optoelectronic chip of claim 4, wherein: the silicon-based PIN photodetector is a lateral photodetector. 6.The silicon-based optoelectronic chip of claim 1, wherein: the optical phase-locked loop link comprises: silicon-based NIP photodetectors configured to detect light for combining a portion of the first light with a portion of the reference light and light for combining a portion of the second light with a portion of the reference light, respectively, to generate corresponding beat frequency signals. 7.The silicon-based optoelectronic chip of claim 1, wherein: the switching link comprises: thermo-optic switches configured to modulate the other portion of the first light and the other portion of the second light, respectively. 8.The silicon-based optoelectronic chip of claim 7, wherein: the thermo-optic switches are M-Z thermo-optic switches. 9.The silicon-based optoelectronic chip of claim 7, wherein: the switching link further comprises: a silicon-based PIN photodetector for detecting the optical intensity of the first and second intensity-modulated light, respectively.

10. The silicon-based optoelectronic chip of claim 1, wherein: the frequency-shifted tuning and beat-note measurement link comprises: a silicon-based single-sideband modulator for performing the single-sideband modulation.

11. The silicon-based optoelectronic chip of claim 10, wherein: the silicon-based single-sideband modulator comprises: a silicon-based electro-optic phase modulator; and a thermo-optic phase shifter.

12. The silicon-based optoelectronic chip of claim 10, wherein: the frequency-shifted tuning and beat-note measurement link further comprises: a silicon-based PIN photodetector for detecting a portion of the frequency-shifted light to generate a signal for monitoring an operating point of the silicon-based single-sideband modulator.

13. The silicon-based optoelectronic chip of claim 10, wherein: the first light is Online light and the second light is Offline light.

14. A lidar comprising: a seed light source; and the silicon-based optoelectronic chip of any one of claims 1-13 coupled with the seed light source.

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