Silicon-based optoelectronic chip and laser radar

Abstract

The invention discloses a silicon-based optoelectronic chip and a laser radar. A silicon-based optoelectronic chip may include a reference light frequency stabilization link, an optical phase lock link, a change-over switch link, and a frequency shift tuning and beat frequency measurement link. The links realize on-chip integration of each device, so that the integration level and the reliability of a voltage stabilization scheme of the seed light source are improved.

Description

Technical Field

[0001] The present application relates generally to laser radar, and specifically to the frequency stabilization of a laser radar seed light source. Background Art

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

[0003] The laser frequency stabilization method currently used includes using a quasi-synchronous digital hierarchy (PDH) frequency stabilization loop based on a gas absorption cell to provide temperature control feedback for lasers operating at a reference wavelength. Lasers of other wavelengths use the reference wavelength as a frequency reference and use an optical phase-locked loop to achieve optical frequency stabilization (Du Juan, Research on Precision Control Technology of Laser Frequency for Spaceborne LiDAR [D], University of Chinese Academy of Sciences, 2018). The seed light source frequency stabilization module currently used includes discrete devices such as phase modulators, PIN-type photodetectors, acousto-optic modulators, magneto-optic switches, and fiber couplers. The size of the frequency stabilization module built with discrete devices is too large. In recent years, research institutions at home and abroad have begun to try to use integrated optoelectronics technology to carry out on-chip integration research of spaceborne LiDAR payloads.

[0004] The reported LiDAR seed light source frequency stabilization chip is manufactured based on the InP platform, with a chip size of 0.9mm×10.7mm. Two sampled grating distributed Bragg reflector (SGDBR) lasers are made on the InP wafer, which are divided into the master laser and the slave laser. Among them, the master laser is stabilized by the PDH frequency stabilization loop composed of a phase modulator, a carbon dioxide absorption cell, a detector and a peripheral circuit, and provides a stable optical reference frequency for the fast-tuned 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 seed light sources including lasers, but the optical frequency stability of the InP-based SGDBR laser is poor and cannot meet the needs of high-precision detection of IPDA LiDAR. In addition, the chip does not take into account the center frequency stability of the lidar pulse light, so it is not sufficient for satellite remote sensing.

[0005] A frequency stabilization solution for a lidar seed light source with high frequency stability and high integration is needed in this field. Summary of the invention

[0006] The present invention is provided in order to realize a frequency stabilization solution for a laser radar seed light source with high frequency stability and high integration.

[0007] According to one invention of the present invention, there is provided a silicon-based optoelectronic chip, which includes: a reference light frequency stabilization link, used for: receiving reference light emitted by a reference laser; providing a feedback control signal for frequency stabilization of the reference laser by an absorption cell method; an optical phase-locking link, used for: receiving a first light emitted by a first laser of a seed light source and a second light emitted by a second laser; respectively combining a portion of the first light and a portion of the second light with a portion of the reference light, and generating a difference frequency signal for optical phase-locking by optical detection; a switching switch link, used for: controlling the light intensity modulation of another portion of the first light and another portion of the second light based on a switching action complementary in the time domain to generate a corresponding first light intensity modulated light and a second light intensity modulated light; combining a portion of the first light intensity modulated light and a portion of the second light intensity modulated light, and polarization splitting the combined light to generate a corresponding first polarized light and a second polarized light; a frequency shift tuning and beat frequency measurement link, used for: single-sideband modulating a portion of the first light to generate frequency-shifted light; combining a portion of the frequency-shifted light with the first polarized light and performing photoelectric detection to generate a signal for monitoring the center frequency of the first laser.

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

[0009] The silicon-based optoelectronic chip as described in any one of the above items, 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 one of the above items, wherein the reference light frequency stabilization link further comprises: a silicon-based PIN-type photodetector, used 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 one of the above items, wherein the silicon-based PIN-type photodetector is a lateral photodetector.

[0012] A silicon-based optoelectronic chip as described in any of the above items, wherein the optical phase-locked link includes: a silicon-based NIP-type photodetector for detecting light that is a combination of a portion of the first light and a portion of the reference light and light that is a combination of a portion of the second light and a portion of the reference light to generate corresponding difference frequency signals.

[0013] The silicon-based optoelectronic chip as described in any one of the above items, wherein the switching switch link comprises: a thermo-optical switch for optically modulating another part of the first light and another part of the second light respectively.

[0014] The silicon-based optoelectronic chip as described in any one of the above items, wherein the thermo-optical switch is an MZ thermo-optical switch.

[0015] The silicon-based optoelectronic chip as described in any one of the above items, wherein the switching switch link further comprises: a silicon-based PIN-type photodetector for detecting the light intensity of the first light intensity modulated light and the second light intensity modulated light respectively.

[0016] The silicon-based optoelectronic chip as described in any one of the above items, wherein the frequency shift tuning and beat frequency measurement link comprises: a silicon-based single sideband modulator, used to perform the single sideband modulation.

[0017] The silicon-based optoelectronic chip as described in any one of the above items, wherein the silicon-based single-sideband modulator comprises: a silicon-based electro-optic phase modulator; and a thermo-optic phase shifter.

[0018] A silicon-based optoelectronic chip as described in any of the above items, wherein the frequency shift tuning and beat frequency measurement link further includes: a silicon-based PIN-type photodetector, used to detect a portion of the frequency-shifted light to generate a signal for monitoring the operating point of the silicon-based single-sideband modulator.

[0019] The silicon-based optoelectronic chip as described in any one of the above items, wherein the first light is online light, and the second light is offline light.

[0020] According to another aspect of the present invention, a laser radar is provided, which includes a seed light source and a silicon-based optoelectronic chip as described in any one of the above items, wherein the silicon-based optoelectronic chip is coupled to the seed light source.

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

[0022] Embodiments of the present invention are described with reference to the accompanying drawings, in which:

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

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

[0025] Figure 3A block diagram of a laser radar according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0026] In the following description, numerous specific details are set forth. However, it should be understood that embodiments of the present invention may be practiced without these specific details. In other instances, well-known circuits, structures, and techniques are not shown in detail to avoid obscuring the understanding of this description.

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

[0028] Figure 1 FIG. 1 is a block diagram of a silicon-based optoelectronic chip 100 according to an embodiment of the present invention. The silicon-based optoelectronic chip 100 can be used for frequency stabilization of a laser radar seed light source. Figure 1 Bold arrows are used to indicate various links on the silicon-based optoelectronic chip 100 , and thin arrows are used to indicate the flow direction and interaction of various signals.

[0029] The silicon-based optoelectronic chip 100 may include a reference light frequency stabilization link 110, an optical phase-locked link 130, a switching link 150, and a frequency shift tuning and beat frequency measurement link 170. By integrating the frequency stabilization device for the seed light source on the silicon-based optoelectronic chip 100, the integration of the seed light source is effectively improved. At the same time, by designing the frequency stabilization device to be separated from the seed light source, the challenge of high-power active devices to chip heat dissipation is avoided. At the same time, the optoelectronic link on the silicon-based optoelectronic chip 100 according to an embodiment of the present invention can also be used for other laser radar light sources, so it also has advantages in power consumption and scalability of laser radar.

[0030] The reference light frequency stabilization link 110 can be used to receive a reference light 111 emitted by a reference laser (not shown), and provide a feedback control signal 112 for stabilizing the reference laser frequency through an 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 frequency stabilization link 110 may 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 frequency stabilization link 110 may be used to pass the modulated light 113 through an absorption cell (e.g., a carbon dioxide gas absorption cell, not shown) outside the silicon-based optoelectronic chip 100, and receive a signal 114 after passing through the absorption cell. By adopting a cascaded phase modulator, the modulation depth is effectively improved. In some embodiments, the above-mentioned cascaded phase modulator may include a silicon-doped waveguide connected in series and include a lumped electrode. Using a silicon-doped waveguide and a lumped electrode, a silicon-based phase modulator with high modulation depth and high bandwidth (e.g., up to 1 GHz) can be realized.

[0032] In some embodiments, the reference light frequency stabilization link 110 may 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 may be a lateral photodetector. The use of a silicon-based PIN photodetector further facilitates the integration of photodetection devices on silicon-based optoelectronic chips.

[0033] The optical phase-locked link 130 may include a 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 may receive lights 131 and 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 frequency stabilization link 110, generate a difference frequency signal 135 for optical phase locking through optical detection, and combine a portion of the light 132 with a portion 116 of the reference light received in the reference light frequency stabilization link 110, generate a difference frequency signal 136 for optical phase locking through optical detection. Lights 131 and 132 respectively use the reference light 111 as a frequency reference, thereby achieving their own optical frequency stabilization with the aid of an optical phase-locked loop.

[0034] In some embodiments, light 131 may be offline light, and light 132 may be online light. In alternative embodiments, light 131 may be online light, and light 132 may be offline light. Here, online light and offline light refer to two lasers of a seed light source (e.g., continuous light generated by distributed feedback (DFB), whose wavelengths may be 1572.024 nm and 1572.085 nm, respectively).

[0035] In some embodiments, the optical phase-locked link 130 may include two corresponding NIP-type photodetectors, one of which is used to detect a light beam formed by combining a portion of the light 131 with a portion of the reference light 115 received in the reference light frequency stabilization link 110 to generate a difference frequency signal 135, and the other is used to detect a light beam formed by combining a portion of the light 132 with a portion of the reference light 116 received in the reference light frequency stabilization link 110 to generate a difference frequency signal 136. The use of silicon-based NIP-type photodetectors further facilitates the integration of photodetection devices on silicon-based optoelectronic chips.

[0036] The switching link 150 can be used to control the light intensity modulation of a portion 133 of the light 131 and a portion 134 of the light 132 based on switching actions complementary in the time domain to generate corresponding light intensity modulated lights 151 and 152. The switching link 150 can also be used to combine the light intensity modulated lights 151 and 152 and perform polarization splitting to generate corresponding polarized light 155.

[0037] In some embodiments, a portion 153 of light 133 and a portion 154 of light 134 in switch link 150 may be used for monitoring.

[0038] In some embodiments, the switching link 150 may include a thermo-optic switch for optically modulating the light 133, 134, respectively. Using a thermo-optic switch instead of a conventional magneto-optic switch may further facilitate the integration of the device on a silicon-based chip. In some embodiments, the thermo-optic switch may be a Mach-Zehnder (MZ) thermo-optic switch.

[0039] In some embodiments, the switch link 150 may include silicon-based PIN photodetectors for respectively detecting the light 151 and 152 with light intensity modulated. The use of silicon-based PIN photodetectors further facilitates the integration of photodetection devices on silicon-based optoelectronic chips.

[0040] The frequency shift tuning and beat frequency measurement link 170 can be used to perform single sideband modulation on a portion 137 of the light 132 to generate a frequency shifted light 171. The frequency shift tuning and beat frequency 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 photoelectric detection to generate a signal 173 for monitoring the center frequency of the laser that emits the light 132. The 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 an offline light, and the light 132 can be an online light. This is because the online light of the seed light source has a higher precision, and frequency stabilization of the seed light source based on the light can obtain more accurate results. Of course, those skilled in the art can also use the online light for the light 131 and the offline light for the light 132 to stabilize the frequency of the seed light source based on the offline light.

[0041] In some embodiments, the frequency shift tuning and beat frequency measurement link 170 may include a silicon-based single sideband modulator for performing the above-mentioned single sideband modulation. The use of a silicon-based single sideband modulator further facilitates the integration of modulation devices on a silicon-based optoelectronic chip. In some embodiments, the silicon-based single sideband modulator may include a silicon-based electro-optic phase modulator and a thermo-optic phase shifter. The use of a silicon-based electro-optic phase modulator to replace an acousto-optic modulator helps to further facilitate the integration of devices on a silicon-based chip.

[0042] In some embodiments, the frequency shift tuning and beat frequency measurement link 170 may include a silicon-based PIN-type photodetector for detecting a portion of the frequency shift light 171 to generate a signal 174 for monitoring the operating point of the silicon-based single-sideband modulator. The use of a silicon-based PIN-type photodetector further facilitates the integration of photodetection devices on silicon-based optoelectronic chips.

[0043] Figure 2 A schematic diagram of the circuit structure of a silicon-based optoelectronic chip 200 according to an embodiment of the present invention 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 may include end face couplers 201 - 1 to 201 - 7 for receiving external signals into the silicon-based optoelectronic chip 200 or transmitting signals in the silicon-based optoelectronic chip 200 to the outside.

[0045] The silicon-based optoelectronic chip 200 may include directional couplers 202 - 1 ˜ 202 - 6 for splitting the received light in a predetermined ratio.

[0046] The silicon-based optoelectronic chip 200 may include multi-mode interference (MMI) couplers 203 - 1 ˜ 203 - 5 for combining and mixing the received multiple light beams.

[0047] The silicon-based optoelectronic chip 200 may include a cascaded phase modulator 204. In some embodiments, the cascaded phase modulator 204 may be a cascaded carrier-depleted silicon-based electro-optical phase modulator. In some embodiments, the cascaded phase modulator 204 may include (for example, two) doped silicon waveguides connected in series and include lumped electrodes. Thus, a silicon-based phase modulator with high modulation depth and high bandwidth (for example, up to 1 GHz) may be achieved. As an example, the modulation region of the cascaded phase modulator 204 may be formed by cascading two doped silicon waveguides with a length of 0.3 mm on an optical path, but the scope of the present invention is not limited thereto. As an example, the cascaded phase modulator 204 may adopt a lumped GSG copper electrode design, where "G" represents a ground line and "S" represents a signal line, but the scope of the present invention is not limited thereto.

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

[0049] The silicon-based optoelectronic chip 200 may include thermo-optic switches 206-1 and 206-2. Using thermo-optic switches 206-1 and 206-2 to replace traditional magneto-optic switches can further promote the integration of devices on silicon-based chips. In some embodiments, the thermo-optic switches 206-1 and 206-2 may be MZ thermo-optic switches. As an example, the thermo-optic switches 206-1 and 206-2 may adopt an MZI structure, and the output intensity of the thermo-optic switches 206-1 and 206-2 may be controlled by a DC level, the switching frequency may reach 5kHz, and the extinction ratio may be higher than 10dB.

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

[0051] The silicon-based optoelectronic chip 200 may 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 may be germanium silicon PIN-type photodetectors. In some embodiments, the PIN-type photodetectors 208-1 to 208-5 may be germanium silicon lateral photodetectors. As an example, the PIN-type photodetectors 208-1 to 208-5 may adopt a GS copper electrode design, but the scope of the present invention is not limited thereto. As an example, the detector length of the PIN-type photodetectors 208-1 to 208-5 may be 20 μm, but the scope of the present invention is not limited thereto.

[0052] The silicon-based optoelectronic chip 200 may 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 may include a silicon-based electro-optic phase modulator and a thermo-optic phase shifter. The use of a silicon-based electro-optic phase modulator to replace the acousto-optic modulator helps to further promote the integration of devices on silicon-based chips. As an example, the silicon-based single sideband modulator 209 may include two 1×2MMI couplers, two MZ carrier-depleted silicon-based electro-optic modulators, and three thermo-optic phase shifters, but the scope of the present invention is not limited to this. As an example, the silicon-based single sideband modulator 209 may adopt a GSGSGSGSSG copper traveling wave electrode design, and the end of the traveling wave electrode includes 8 titanium nitride matching resistors, but the scope of the present invention is not limited to this. As an example, the resistance value of the titanium nitride matching resistor may be 52Ω and the size may be 144.3μm×30μm. The purpose of this design is to ensure impedance matching under the premise of preventing the titanium nitride metal from fusing due to a large voltage swing input signal, but the scope of the present invention is not limited to this.

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

[0054] The connection relationship of the various components of the silicon-based optoelectronic chip 200 is described below based on channel division.

[0055] In some embodiments, the silicon-based optoelectronic chip 200 may 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 pulse light beat frequency detection channel.

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

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

[0058] The offline transmission channel may include an end coupler 201 - 1 , a directional coupler 202 - 1 , a thermo-optic switch 206 - 1 , a directional coupler 202 - 5 , a PIN-type photodetector 208 - 3 , an MMI coupler 203 - 5 , a polarization beam splitter 210 , and an end coupler 201 - 6 . The end face coupler 201-1 is connected to the input end of the directional coupler 202-1, 90% of the intensity of 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% of the intensity of light at the output end of the directional coupler 202-5 is connected to the input end of the PIN photodetector 208-3, 90% of the intensity of 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 may include an end coupler 201-1, a directional coupler 202-1, an MMI coupler 203-2, an end coupler 201-2, a directional coupler 202-2, an MMI coupler 203-3, an adjustable optical attenuator 205-1, and a NIP type photodetector 207-1. The waveguide end of the end coupler 201-1 is connected to the input end of the directional coupler 202-1, 10% of the intensity of 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 coupler 201-2 is connected to the input end of the directional coupler 202-2, 10% of the intensity of 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, and the output end of VOA1 of the adjustable optical attenuator 205-1 is connected to the input end of the NIP type photodetector 207-1.

[0060] The online beat frequency detection channel may include an end coupler 201-4, an MMI coupler 203-1, a directional coupler 202-3, an MMI coupler 203-2, an end coupler 201-2, a directional coupler 202-2, an MMI coupler 203-4, an adjustable optical attenuator 205-2, and a NIP type photodetector 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% of the intensity of light at 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% of the intensity of light at 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 photodetector 207-2.

[0061] The online transmission channel may include an end coupler 201-4, an MMI coupler 203-1, a directional coupler 202-3, a thermo-optical switch 206-2, a directional coupler 202-6, a PIN photodetector 208-4, an MMI coupler 203-5, a polarization beam splitter 210, and an end coupler 201-6. The waveguide end of the end 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% of the intensity of light at the output end of the directional coupler 202-3 is connected to the input end of the thermo-optical switch 206-2, the output end of the thermo-optical switch 206-2 is connected to the input end of the directional coupler 202-6, 10% of the intensity of light at the output end of the directional coupler 202-6 is connected to the PIN-type photodetector 208-4, 90% of the intensity of light at 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 110, and the TE mode output end of the polarization beam splitter 210 is connected to the waveguide end of the end coupler 201-6.

[0062] The online pulse light beat frequency monitoring channel may include an end 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 coupler 201-7. The waveguide end of the end coupler 201-4 is connected to the input end of the MMI coupler 203-1, the other 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% of the intensity of light at the output end of the directional coupler 202-4 is connected to the input end of the PIN-type photodetector 208-5, 90% of the intensity of light at 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 coupler 201-7 is connected to the other 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-type photodetector 208-2.

[0063] The following describes the basic working principle of the silicon-based optoelectronic chip 200 according to the link division. Figure 1 The links described are consistent.

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

[0065] The working principle of the reference light frequency stabilization link is as follows: the continuous light of 1572.018nm generated by a DFB laser is used as the reference light 220, which is coupled to the end coupler 201-2 through the optical fiber and enters the silicon-based optoelectronic chip 200. The light is split into two paths of light with an intensity ratio of 90:10 through the directional coupler 202-2. The light with 90% intensity enters the cascade phase modulator 204, and the light with 10% intensity enters the MMI coupler 203-2. An electrical signal with a frequency in the range of 100 to 200MHz is input to the lumped electrode of the cascade phase modulator 204 to perform phase modulation on the reference light 220. The modulated reference light is coupled to the optical fiber through the end coupler 201-3 and leaves the silicon-based optoelectronic chip to form a signal 221. The signal 221 passes through the carbon dioxide gas absorption cell 222 outside the silicon-based optoelectronic chip 200, and the signal 223 passing through the carbon dioxide gas absorption cell 222 is coupled to the end coupler 201-5 through the optical fiber, thereby entering the silicon-based optoelectronic chip 200, and finally being received and detected by the PIN-type photodetector 208-1. The photoelectric signal generated by the PIN-type photodetector 208-1 can be used as a temperature feedback control signal of the reference laser that emits the reference light 220 after a series of processing such as frequency mixing and low-pass filtering, so that the optical center frequency of the reference light 220 is finally 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 1572.024nm and 1572.085nm as online light 231 and offline light 230 respectively. Offline light 230 is coupled to the end coupler 201-4 through the optical fiber and enters the silicon-based optoelectronic chip 200, and is split into two beams of equal intensity by the MMI coupler 203-1. One of the beams is split into two beams of light with an intensity ratio of 90:10 via the directional coupler 202-3, and the light with 90% intensity enters the thermo-optical switch 206-2, and the light with 10% intensity enters the MMI coupler 103-4. The Offline light 230 is coupled to the end coupler 201-1 through the optical fiber and enters the silicon-based optoelectronic chip 200. It is split into two light beams with a light intensity ratio of 90:10 through the directional coupler 202-1. The light with 90% intensity enters the thermo-optical switch 206-1, and the light with 10% intensity enters the MMI coupler 203-3. The MMI coupler 203-2 splits it into two light beams with equal light intensity, which enter the MMI coupler 203-3 and the MMI coupler 203-4 respectively. Since there is a certain wavelength difference between the reference light 220 and the Online light 231 and the Offline light 230, a difference frequency signal with a frequency of about 760MHz is generated when the reference light 220, the Online light 231 and the Offline light 230 enter the NIP photodetector 207-1, and a difference frequency signal with a frequency of about 8.08GHz is generated when the reference light 220, the Online light 231 and the Online light 231 enter the NIP photodetector 207-2. The difference frequency signal generated by the NIP type photodetectors 207-1 and 207-2 provides the feedback information required for the laser temperature control for the optical phase-locked loop, thereby achieving the stability of the laser optical frequency. In some embodiments, the NIP type photodetectors 107-1 and 107-2 are respectively connected to adjustable optical attenuators 105-1 and 105-2, the purpose of which 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 the switched optical link is as follows: Online light 231 and Offline light 230 need to pass through the thermo-optical switches 206-1 and 206-2 respectively, and are split into two paths of light with a light intensity ratio of 90:10 by the corresponding directional couplers 202-5 and 202-6. Light with 10% intensity enters the PIN photodetector 208-3 for monitoring. Light with 90% intensity enters the MMI coupler 203-5, and only the TE mode light is retained after passing through the bias beam splitter 210, which is further coupled by the end face coupler 201-6 and output as a signal 240 to the outside of the silicon-based optoelectronic chip 200 through the optical fiber. As an example, the thermo-optical switches 206-1 and 206-2 can realize the switching modulation of the light intensity by inputting a DC square wave with an interval of 200μs, and the switching actions of the thermo-optical switches 206-1 and 206-2 can be complementary in the time domain to realize the alternating output of the two optical signals.

[0068] The working principle of the frequency shift tuning and beat frequency measurement link is as follows: another path of the online light separated 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, among which the first-order (i.e., +1 or -1) subharmonic occupies most of the light intensity, and the modulation frequency is 400MHz, which becomes the online frequency shift light. In some embodiments, the silicon-based single-sideband modulator 209 can be built according to the architecture of the optical IQ modulator, and the single-sideband modulation is realized by controlling the bias voltage of the three thermo-optical phase shifters and the traveling wave electrode. The working point of the single-sideband modulation needs to be feedback controlled, so the directional coupler 202-4 can be cascaded at the output end of the silicon-based single-sideband modulator 209. The directional coupler 202-4 distributes the optical signal with 10% intensity to the PIN-type photodetector for monitoring the working point of the silicon-based single-sideband modulator 209, and allows the optical signal with 90% intensity to enter the input end of the MMI coupler 103-4. When the value of the optical signal of a single output segment of the PIN-type photodetector is lower than a certain threshold, it can be considered that the silicon-based single-sideband modulator 209 is in normal working condition. The online light emitted by the above-mentioned online transmission channel is compressed and amplified by the optical parametric oscillator to become an online pulse light, and the center frequency of the online pulse light may drift. Therefore, it is necessary to separate the signal 250 corresponding to the online light from the signal 240, so that it enters the silicon-based optoelectronic chip 200 through the end coupler 201-7 to be input to the other input end of the MMI coupler 203-4. The online frequency-shifted light is combined with the online pulse light and enters the NIP-type photodetector 208-2. The generated photoelectric signal contains a DC component and 400MHz and its harmonic components, thereby realizing the monitoring of the center frequency of the online pulse light.

[0069] It is worth noting that the various components of the silicon-based optoelectronic chip 200 , their connection methods, parameter settings, etc. described above are only exemplary, and those skilled in the art can use various alternative implementation methods based on the working principles of the various links described.

[0070] According to another aspect of the present invention, a laser radar is provided.

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

[0072] The laser radar 300 may include a seed light source 310 and a silicon-based optoelectronic chip 330 coupled thereto. The silicon-based optoelectronic chip 330 may be a combination of the above Figure 1 The silicon-based optoelectronic chip 100 described herein or in combination Figure 2 The silicon-based optoelectronic chip 200 described above. The laser radar 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 embodiments, implementations and aspects described above have been described to allow easy understanding of the invention and do not limit the invention. On the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims, the scope of which should be given the broadest interpretation to cover all such modifications and equivalent structures as permitted under the law.

Claims

1. A silicon-based optoelectronic chip, comprising: Reference optical frequency stabilization link for: receiving a reference light emitted by a reference laser; Providing a feedback control signal for frequency stabilization of the reference laser by an absorption cell method; an optical phase-locked link, for: receiving a first light emitted by a first laser of a seed light source and a second light emitted by a second laser; respectively combining a portion of the first light and a portion of the second light with a portion of the reference light, and generating a difference frequency signal for optical phase locking through optical detection; Switch link for: Controlling light intensity modulation of another portion of the first light and another portion of the second light based on switching actions complementary in the time domain to generate corresponding first light intensity modulated light and second light intensity modulated light; Combining a portion of the first light intensity modulated light and a portion of the second light intensity modulated light, and performing polarization splitting on the combined light to generate corresponding first polarized light and second polarized light; Frequency shift tuning and beat frequency measurement links for: performing single sideband modulation on a portion of the first light to generate frequency-shifted light; A portion of the frequency-shifted light is combined with the first polarized light and photoelectrically detected to generate a signal for monitoring the center frequency of the first laser.

2. The silicon-based optoelectronic chip according to claim 1, characterized in that: The reference optical frequency stabilization link comprises: A cascaded phase modulator is used to modulate a portion of the reference light, and the reference light frequency stabilization link is used to: A portion of the modulated reference light is passed through an absorption cell outside the silicon-based optoelectronic chip, and a signal input after passing through the absorption cell is received.

3. The silicon-based optoelectronic chip according to claim 2, characterized in that: The cascaded phase modulator comprises doped silicon waveguides connected in series and includes lumped electrodes.

4. The silicon-based optoelectronic chip according to claim 2, characterized in that: The reference optical frequency stabilization link also includes: The silicon-based PIN type photodetector is used to detect the signal input after passing through the absorption cell to generate the feedback control signal.

5. The silicon-based optoelectronic chip according to claim 4, characterized in that: The silicon-based PIN-type photodetector is a lateral-type photodetector.

6. The silicon-based optoelectronic chip according to claim 1, characterized in that: The optical phase-locked link comprises: A silicon-based NIP type photodetector is used to detect light formed by combining a portion of the first light with a portion of the reference light and light formed by combining a portion of the second light with a portion of the reference light to generate corresponding difference frequency signals.

7. The silicon-based optoelectronic chip according to claim 1, characterized in that: The switching link comprises: A thermo-optical switch for optically modulating another portion of the first light and another portion of the second light, respectively.

8. The silicon-based optoelectronic chip according to claim 7, characterized in that: The thermo-optical switch is an MZ thermo-optical switch.

9. The silicon-based optoelectronic chip according to claim 7, characterized in that: The switching link further comprises: Silicon-based PIN-type photodetectors for detecting the light intensities of the first light-intensity modulated light and the second light-intensity modulated light, respectively.

10. The silicon-based optoelectronic chip according to claim 1, characterized in that: The frequency shift tuning and beat frequency measurement link includes: A silicon-based single sideband modulator is used to perform the single sideband modulation.

11. The silicon-based optoelectronic chip according to claim 10, characterized in that: The silicon-based single sideband modulator comprises: Silicon-based electro-optic phase modulators; and Thermo-optical phase shifter.

12. The silicon-based optoelectronic chip according to claim 10, characterized in that: The frequency shift tuning and beat frequency measurement link also includes: A silicon-based PIN-type photodetector is used to detect a portion of the frequency-shifted light to generate a signal for monitoring the operating point of the silicon-based single-sideband modulator.

13. The silicon-based optoelectronic chip according to claim 10, characterized in that: The first light is Online light, and the second light is Offline light.

14. A laser radar, comprising: Seed light source; as well as The silicon-based optoelectronic chip according to any one of claims 1 to 13, coupled to the seed light source.

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