WO2023273565A1 - 一种频率可调谐的半导体激光器 - Google Patents

一种频率可调谐的半导体激光器 Download PDF

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Publication number
WO2023273565A1
WO2023273565A1 PCT/CN2022/089079 CN2022089079W WO2023273565A1 WO 2023273565 A1 WO2023273565 A1 WO 2023273565A1 CN 2022089079 W CN2022089079 W CN 2022089079W WO 2023273565 A1 WO2023273565 A1 WO 2023273565A1
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Prior art keywords
phase shifter
laser
waveguide
optical amplifier
semiconductor optical
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PCT/CN2022/089079
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English (en)
French (fr)
Inventor
沈红明
曾理
郭宇耀
周林杰
陆梁军
赵瑞玲
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华为技术有限公司
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Publication of WO2023273565A1 publication Critical patent/WO2023273565A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H01S5/1003—Waveguide having a modified shape along the axis, e.g. branched, curved, tapered, voids
    • H01S5/1014—Tapered waveguide, e.g. spotsize converter
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/02—Structural details or components not essential to laser action
    • H01S5/028—Coatings ; Treatment of the laser facets, e.g. etching, passivation layers or reflecting layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
    • H01S5/068—Stabilisation of laser output parameters
    • H01S5/0683—Stabilisation of laser output parameters by monitoring the optical output parameters
    • H01S5/0687—Stabilising the frequency of the laser
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H01S5/12—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers
    • H01S5/125—Distributed Bragg reflector [DBR] lasers

Definitions

  • the present application relates to the technical field of lasers, in particular to a frequency-tunable semiconductor laser.
  • frequency-modulated lasers can be, for example, distributed feedback (DFB) lasers, which use electrical injection to realize frequency tunability of lasers.
  • DFB distributed feedback
  • the resonant cavity of DFB semiconductor lasers is generally relatively short, the linewidth of emitted laser light is relatively large. , and the thermal effect of the injected current will also bring obvious nonlinear effect of frequency modulation, thereby reducing the signal-to-noise ratio.
  • Frequency-modulated lasers can also use whispering gallery mode optical resonator technology, which can reduce the linewidth of the laser through optical feedback, but the structure of the laser is complex, requiring multiple optical elements for spatial optical coupling, which makes coupling difficult and expensive.
  • the present application provides a frequency-tunable semiconductor laser, which is used to provide a semiconductor laser that is less difficult to couple and can simultaneously output fast frequency modulation, narrow line width, and high-power laser signals.
  • the present application provides a frequency-tunable semiconductor laser, including a first reflective semiconductor optical amplifier and an optical resonant cavity; the first reflective semiconductor optical amplifier is coupled to the optical resonant cavity; the optical resonant The cavity includes: a speckle converter, a first waveguide converter and a first phase shifter; wherein the speckle converter is made of silicon nitride waveguide material, and the first phase shifter is made of silicon waveguide material
  • the first reflective semiconductor optical amplifier is used to inject light into the optical resonant cavity;
  • the mode spot converter is used to convert the spot size output by the first reflective semiconductor optical amplifier into the The spot size of the input of the first waveguide converter;
  • the first waveguide converter including a silicon nitride waveguide and a silicon waveguide, is used to transmit the light beam from the mode spot converter to the first phase shifter ;
  • the first phase shifter is used to control and change the phase of the light beam by changing the refractive index in the optical resonant cavity, so that the laser can output
  • the silicon waveguide has higher modulation efficiency characteristics. Therefore, on the one hand, the first phase shifter is made of silicon waveguide material, and its response time can almost reach the nanosecond (ns) level, so that a small range of fast speed can be realized by changing the current applied to the first phase shifter The frequency is swept, and the corresponding laser power and line width change little.
  • other functional optical elements in the optical resonator of the semiconductor laser provided in the present application except the first phase shifter can be made of silicon nitride waveguide material, so as to ensure the power when transmitting laser signals.
  • the laser designed in this application can satisfy the characteristics of outputting fast frequency modulation, narrow line width, and high power laser signal at the same time, and also has the advantage of less difficulty in coupling.
  • the detection distance and detection accuracy during laser detection can also be improved.
  • the first phase shifter is a PIN phase shifter.
  • the PIN phase shifter includes: an I-type undoped region, a P-type doped region and an N-type doped region.
  • the laser also includes a drive circuit; the anode of the drive circuit is connected to the P-type doped region, and the cathode of the drive circuit is connected to the N-type doped region.
  • the driving circuit is used to inject different driving currents into the first phase shifter, so that the first phase shifter changes the refractive index in the optical resonant cavity.
  • the first phase shifter is a plurality of PIN phase shifters cascaded.
  • Each of the PIN phase shifters includes: an I-type undoped region, a P-type doped region and an N-type doped region.
  • the N-type doped region of the previous-stage PIN phase shifter is connected to the P-type doped region of the subsequent-stage PIN phase shifter.
  • the laser also includes a drive circuit; the anode of the drive circuit is connected to the P-type doped region of the first-stage PIN phase shifter of the first phase shifter, and the cathode of the drive circuit is connected to the first phase shifter.
  • the driving circuit is used to inject different driving currents into the first phase shifter, so that the first phase shifter changes the refractive index in the optical resonant cavity.
  • the optical resonant cavity further includes a second waveguide converter and one or more filters cascaded.
  • Each of said filters is made of silicon nitride waveguide material.
  • the second waveguide converter includes a silicon waveguide and a silicon nitride waveguide, for transmitting the light beam from the first phase shifter made of the silicon waveguide material to the silicon nitride waveguide material.
  • the cascaded one or more filters are used to control the laser to output the frequency-tunable laser signal of a specified wavelength.
  • the optical resonant cavity further includes a second waveguide converter and a distributed Bragg reflector DBR.
  • the DBR is made of silicon nitride waveguide material.
  • the second waveguide converter includes a silicon waveguide and a silicon nitride waveguide, for transmitting the light beam from the first phase shifter made of the silicon waveguide material to the silicon nitride waveguide material.
  • the DBR is used to control the laser to output the frequency-tunable laser signal of a specified wavelength; and transmit the first part of the light beam as a laser signal, and transmit the second part of the light beam to reflected back to the first reflective semiconductor optical amplifier.
  • the laser structure provided in this design can achieve similar technical effects to the former possible design. Moreover, the structure provided by this design can further reduce the number of optical components contained in the laser. Compared with the previous possible design, this design can simplify the structure of the frequency-tunable semiconductor laser and help reduce the obtained the size of the laser.
  • the optical resonant cavity further includes a second phase shifter; the second phase shifter is made of silicon waveguide material.
  • the second phase shifter is located between the first waveguide converter and the first phase shifter, and is used to control the initial phase of the light beam by changing the refractive index in the optical resonant cavity.
  • a third semiconductor optical amplifier is also included.
  • the first reflective semiconductor optical amplifier is further configured to transmit the second partial light beam reflected by the mirror to the third semiconductor optical amplifier.
  • the third semiconductor optical amplifier is configured to provide signal gain for the second part of the light beam before outputting it.
  • the first side of the first reflective semiconductor optical amplifier is coated with an antireflection film, and the second side is coated with a low reflection film.
  • the first side of the first reflective semiconductor optical amplifier is the coupling surface of the first reflective semiconductor optical amplifier and the optical resonant cavity; the second side of the first reflective semiconductor optical amplifier is the coupling surface of the first reflective semiconductor optical amplifier. The face opposite the first side of the reflective semiconductor optical amplifier.
  • An anti-reflection film is coated on the first side and the second side of the third semiconductor optical amplifier.
  • the first side of the third semiconductor optical amplifier is the coupling surface of the third semiconductor optical amplifier and the first reflective semiconductor optical amplifier; the second side of the third semiconductor optical amplifier is the coupling surface of the third semiconductor optical amplifier. The face opposite the first side.
  • the output power of the laser signal output from the second side of the first reflective semiconductor optical amplifier can also be increased through the third semiconductor optical amplifier, and at the same time, it can compensate for the existence of integrated silicon-based functional optical elements in the optical resonant cavity.
  • the problem of transmission loss can improve the detection distance of frequency-modulated lasers.
  • FIG. 1 is a system block diagram of FMCW lidar
  • FIG. 2 is one of the structural schematic diagrams of a frequency-tunable semiconductor laser 102 provided in an embodiment of the present application;
  • FIG. 4 is the second structural schematic diagram of a frequency tunable semiconductor laser 102 provided by the embodiment of the present application.
  • FIG. 5a is a schematic structural diagram of a first phase shifter 2023 provided by an embodiment of the present application.
  • FIG. 5b is a schematic diagram of optical signal transmission of a first phase shifter 2023 provided by the embodiment of the present application.
  • FIG. 5c is a schematic structural diagram of another first phase shifter 2023 provided by the embodiment of the present application.
  • Fig. 6a is the third structural schematic diagram of a frequency tunable semiconductor laser 102 provided by the embodiment of the present application.
  • FIG. 6b is a schematic structural diagram of a filter 2025 provided by an embodiment of the present application.
  • FIG. 7 is the fourth structural schematic diagram of a frequency tunable semiconductor laser 102 provided by the embodiment of the present application.
  • FIG. 8 is the fifth structural schematic diagram of a frequency tunable semiconductor laser 102 provided by the embodiment of the present application.
  • FIG. 9 is the sixth structural schematic diagram of a frequency tunable semiconductor laser 102 provided by the embodiment of the present application.
  • Fig. 10 is the seventh structural schematic diagram of a frequency tunable semiconductor laser 102 provided by the embodiment of the present application.
  • Fig. 11 is the eighth structural schematic diagram of a frequency tunable semiconductor laser 102 provided by the embodiment of the present application.
  • FIG. 12 is a ninth structural schematic diagram of a frequency-tunable semiconductor laser 102 provided by an embodiment of the present application.
  • the embodiments of the present application can be applied to various technologies including frequency-tunable semiconductor lasers, such as lidar, optical coherence tomography (optical coherence tomography, OCT) and other technologies.
  • frequency-tunable semiconductor lasers such as lidar, optical coherence tomography (optical coherence tomography, OCT) and other technologies.
  • lidar can be widely used in robotics, autonomous driving, drones and other fields, and can use laser light to measure the distance to target objects.
  • the mainstream lidar ranging method is pulsed time of flight (ToF) lidar.
  • the principle of pulsed ToF lidar is: by emitting a laser pulse signal with high peak power, and measuring the round-trip time of the light pulse emitted from the target object to achieve distance detection.
  • FMCW lidar Compared with pulsed TOF lidar, FMCW lidar has higher sensitivity and ranging accuracy, can realize ultra-long-distance detection (usually greater than 300m), and can resist the interference of sunlight and other lasers and real-time speed measurement. It is a kind of Very promising lidar technology.
  • the principle of FMCW lidar is: using coherent measurement technology, the distance information of the target object is obtained by comparing the difference between the frequency of the reflected signal reflected by the target object and the frequency of the transmitted signal at that moment.
  • FIG. 1 is a system block diagram of an FMCW lidar.
  • the FMCW lidar 100 may include: a signal control 101, a frequency-tunable semiconductor laser 102 (also referred to simply as “frequency-modulated laser”, and “frequency-tunable semiconductor laser” and “frequency-modulated laser” may be used interchangeably in the following embodiments ), a transmitting optical module 103, a scanner 104, a receiving optical module 105, a balance detector 106 and a signal processing system 107.
  • the signal control 101 sends out a control signal, so that the frequency-tunable semiconductor laser 102 emits frequency-modulated continuous laser light.
  • the laser light is divided into two beams through the emitting light module 103, one beam is intrinsic light, and the other beam is signal light.
  • the signal light is irradiated onto the target through the scanner 104 .
  • the signal light reflected from the target is received by the receiving light module 105 and mixed with the intrinsic light on the balance detector 106 to obtain a beat frequency electrical signal.
  • the beat frequency electrical signal output by the balance detector 106 is sent to the signal processing system 107 for analysis, and the 3D point cloud image is output and the speed information of the target is obtained, and then the distance information of the target can be calculated.
  • the DFB semiconductor laser emits laser light, which is coupled to a whispering gallery mode (whispering gallery mode, WGM) resonator through a first optical coupler.
  • WGM whispering gallery mode
  • the DFB semiconductor laser is frequency-locked on the resonant frequency of the WGM resonator through injection, so that the linewidth of the output laser is compressed, so that a laser with a narrower linewidth can be obtained.
  • the frequency of the WGM resonator can be changed rapidly through the electro-optical effect, so that laser frequency modulation can be realized.
  • the prior art has not yet provided a good technical solution for how to realize that the frequency modulation laser can emit laser signals with sufficiently fast frequency modulation rate, sufficiently narrow line width, high optical power and frequency modulation linearity. Therefore, it is of great significance to the development of laser radar, optical communication and other fields to provide a semiconductor laser that can simultaneously output fast frequency modulation, narrow linewidth, and high-power laser signals and has low coupling difficulty.
  • the frequency-modulated laser provided by this application, due to the advantages of silicon nitride waveguide with low loss and high power upper limit, and the characteristics of silicon waveguide that can realize fast frequency modulation, can combine optical components using two waveguides to provide a frequency-tunable semiconductor laser.
  • the frequency-tunable semiconductor laser 102 includes a first reflective semiconductor optical amplifier (reflex semiconductor optical amplifier, RSOA) 201 and an optical resonant cavity 202 .
  • the first RSOA 201 is coupled with an optical resonant cavity 202.
  • the first RSOA 201 is used to inject light beams into the optical resonant cavity. And providing signal gain to the beam before injection can also be understood as performing signal amplification to compensate for the loss generated when the beam oscillates in the optical resonator.
  • An optional implementation manner is that an anti-reflection coating can be coated on the first side of the first RSOA 201, and a high-reflection coating can be coated on the second side.
  • the first side is the coupling surface between the first RSOA 201 and the optical resonant cavity 202, such as the right side of the first RSOA 201 in Figure 2;
  • the second side is the surface opposite to the first side of the first RSOA 201, such as The left side of the first RSOA 201 in FIG. 2 .
  • the light beam can be reflected on the second side and can be transmitted on the first side, so that the first RSOA 201 can inject the light beam into the optical resonant cavity 202 to oscillate through the anti-reflection coating on the first side.
  • the active region of the first RSOA 201 can be implemented using III-V quantum well or quantum dot materials.
  • the optical resonant cavity 202 may specifically include: a mode speckle converter 2021 , a first waveguide converter 2022 and a first phase shifter 2023 .
  • the mode spot converter 2021 may be made of silicon nitride waveguide material
  • the first phase shifter 2023 may be made of silicon waveguide material.
  • the output end of the first RSOA 201 and the input end of the mode-spot converter 2021 may be connected in a butt coupling manner, or may also be coupled in other manners, which are not limited in this application.
  • the mode-speckle converter 2021 can be realized by adopting structures such as an inverted tapered coupler, a suspended waveguide coupler, or a trident coupler.
  • the structure adopted by the mode speckle converter 2021 can be determined according to the actual scene of the output spot size of the first RSOA 201 and the input spot size of the first waveguide converter 2022.
  • the mode spot converter 2021 is used to convert the spot size output by the first RSOA 201 into the spot size input by the first waveguide converter 2022. Or, if the transmission direction of the light beam is from the first waveguide converter 2022 to the first RSOA 201 scenario, the mode spot converter 2021 can also be used to output the spot size of the first waveguide converter 2022, Convert to the spot size of the first RSOA 201 input. In this way, the coupling efficiency between the first RSOA 201 and the optical resonant cavity 202 can be improved, and the loss generated when the light beam resonates between the first RSOA 201 and the optical resonant external cavity 202 can be reduced.
  • the first waveguide converter 2022 includes a silicon nitride waveguide and a silicon waveguide, and is used to transmit the light beam from the mode speckle converter 2021 made of the silicon nitride waveguide material to the silicon
  • the first phase shifter 2023 is made of waveguide material.
  • the transmission direction of the beam is from the first phase shifter 2023 to the speckle converter 2021
  • the beam from the first phase shifter 2023 may be transmitted to the speckle converter 2021 .
  • the mode spot converter 2021 is made of silicon nitride waveguide material and the first phase shifter 2023 is made of silicon waveguide material
  • the light beam has different transmission characteristics on different transmission waveguide materials. In order to realize the light beam can be For signal transmission on two different materials, the first waveguide converter 2022 can be used to realize the conversion.
  • FIG. 3 is a schematic structural diagram of a first waveguide converter 2022 provided by the embodiment of the present application.
  • the first waveguide converter 2022 can be mainly realized by upper and lower waveguides, the upper layer waveguide can be a tapered silicon nitride waveguide, and the lower layer waveguide can be an inverted tapered silicon waveguide.
  • Two-layer waveguides can transmit light through vertical coupling.
  • the light beam enters the first waveguide converter 2022 from the input end of the tapered silicon nitride waveguide in the first waveguide converter 2022 (such as the A end in FIG. 3 ), and is transmitted to the tapered silicon nitride waveguide.
  • the light beam can continue to transmit to the input end of the inverted tapered silicon waveguide (as shown in Figure 3, the C end), and finally from the output end of the inverted tapered silicon waveguide (as shown in Figure 3
  • the D terminal in is output to the first phase shifter 2023.
  • the transmission of the first waveguide converter 2022 the transmission of light beams between optical elements made of different waveguide materials can be realized, so that the laser provided by the application can be designed in combination with the transmission characteristics of different waveguide materials.
  • the first phase shifter 2023 is used to control and change the phase of the light beam by changing the refractive index in the optical resonant cavity 202, so that the laser outputs a laser signal with tunable frequency.
  • the response time of the first phase shifter 2023 made of silicon waveguide material can almost reach the nanosecond (ns) level, so that small-scale fast scanning can be realized by changing the current applied to the first phase shifter 2023 frequency, and the corresponding laser power and linewidth change little.
  • the frequency tunable semiconductor laser 102 provided in this application may further include a driving circuit.
  • FIG. 4 it is a schematic structural diagram of another frequency-tunable semiconductor laser 102 provided by an embodiment of the present application.
  • the frequency tunable semiconductor laser 102 also includes a driver circuit 203 .
  • the driving circuit 203 is used to inject different driving currents into the first phase shifter 2023, so that the first phase shifter 2023 changes the refractive index in the optical resonant cavity.
  • the driving circuit 203 can be realized through the signal control 101 introduced in FIG. 1 , or can also be realized through a separate chip.
  • the first phase shifter 2023 may be a PIN phase shifter formed by etching and doping silicon.
  • FIG. 5 a it is a schematic structural diagram of a first phase shifter 2023 provided by an embodiment of the present application.
  • the PIN phase shifter includes: an I-type undoped region, a P-type doped region and an N-type doped region. Wherein, the I-type undoped region is a silicon waveguide.
  • the specific connection mode of the first phase shifter 2023 and the driving circuit 203 can be that the positive pole of the driving circuit 203 is connected with the P-type doped region of the PIN phase shifter, and the negative pole of the driving circuit 203 is connected with the N-type doped region of the PIN phase shifter. Doped region connections.
  • the PIN phase shifter may be composed of an electro-optic phase shifter whose response time can almost reach the order of ns.
  • the driving current applied to the first phase shifter 2023 by the driving circuit 203 can be changed, so that a fast frequency sweep of a small range of frequencies can be realized, and the corresponding laser power and line width change little.
  • FIG. 5 b is a schematic diagram of optical signal transmission of a first phase shifter 2023 provided by an embodiment of the present application.
  • the first phase shifter 2023 can receive the light beam from two directions.
  • the first direction may be the direction of the light beam emitted by the first RSOA 201
  • the second direction may be the direction of the light beam reflected by the mirror described in the subsequent embodiments.
  • the light beam can be transmitted in the silicon waveguide in the I-type undoped region, while the P-type doped region and the N-type doped region are controlled by the driving current of the driving circuit 203 to realize the frequency tuning of the output laser signal.
  • the length of the PIN phase shifter shown in FIG. 5a can be designed to be longer, for example, it can be designed to be greater than 1 millimeter (mm).
  • the first phase shifter 2023 can also be composed of multiple PIN phase shifters cascaded to obtain a longer length of the first phase shifter 2023, wherein each PIN phase shifter is as Figure 5a and Figure 5b show the structure and principle of optical signal transmission.
  • FIG. 5c it is a schematic structural diagram of another first phase shifter 2023 provided by the embodiment of the present application.
  • the N-type doped region of the previous PIN phase shifter is connected to the P-type doped region of the subsequent PIN phase shifter; for example, the PIN phase shifter of the previous stage
  • the N-type doped region and the P-type doped region of the subsequent PIN phase shifter can be connected through conductive metal electrodes.
  • the anode of the driving circuit 203 can be connected to the P-type doped region of the first stage PIN phase shifter of the first phase shifter 2023, and the driving circuit 203
  • the negative electrode of the first phase shifter 2023 can be connected to the N-type doped region in the last stage PIN phase shifter in the first phase shifter 2023 .
  • the driving circuit 203 is configured to inject different driving currents into the first phase shifter 2023 so that the first phase shifter 2023 changes the refractive index in the optical resonant cavity 202 .
  • the length of a PIN phase shifter or cascaded multiple PIN phase shifters can be designed to be greater than 1 millimeter (mm), and at this time, a PIN phase shifter or cascaded multiple PIN phase shifters constitute
  • the first phase shifter 2023 has the advantages of low loss and high phase shifting precision.
  • the driving voltage of the entire first phase shifter can be increased through the cascaded structure, which is equivalent to improving the voltage resolution that each PIN phase shifter can obtain, thereby reducing transmission loss. , can also improve the phase shifting accuracy.
  • the wavelength of the output laser signal can be further realized.
  • FIG. 6 a it is a schematic structural diagram of another frequency-tunable semiconductor laser 102 provided by an embodiment of the present application.
  • the optical resonant cavity 202 may also include a second waveguide converter 2024 and one or more cascaded filters 2025 (Fig. 6a takes two cascaded filters as an example , that is, the first filter 2025a and the second filter 2025b are described as an example).
  • each of the filters 2025 that is, the first filter 2025a and the second filter 2025b can be made of silicon nitride waveguide material, and the first phase shifter 2023 is made of silicon waveguide material, so the second waveguide conversion can be adopted
  • the device 2024 realizes the signal transmission of the light beam on two different waveguide materials.
  • the difference from the first waveguide converter 2022 is that, in the direction of the first RSOA 201 injection beam, the first waveguide converter 2022 is a converter from a silicon nitride waveguide material to a silicon waveguide material, and the second waveguide converter 2024 is a silicon Converter from waveguide material to silicon nitride waveguide material.
  • the second waveguide converter 2024 includes a silicon waveguide and a silicon nitride waveguide, and is used to convert the light beam from the silicon waveguide material to the
  • the first phase shifter 2023 is transmitted to the first filter 2025a made of the silicon nitride waveguide material.
  • the cascaded one or more filters 2025 are used to control the laser to output the frequency-tunable laser signal of a specified wavelength, so that the frequency of the laser signal output by the laser can be tuned.
  • one or more filters 2025 in cascade are assumed to include a first filter 2025a and a second filter 2025b, and the first filter 2025a and the second filter 2025b may be micro-ring filters . Since the two microring filters are different, the wavelength tunability of the output laser signal can be realized based on the vernier effect in optics. Alternatively, in another optional implementation manner, the laser may also be implemented by using other types of filters, and the number of selected filters may be determined according to actual requirements, which is not limited in this application.
  • wavelength tunability can also be realized by integrating a thermo-optic phase shifter on the filter 2025 .
  • FIG. 6 b it is a schematic structural diagram of a filter 2025 provided by an embodiment of the present application.
  • the optical resonant cavity 202 may further include a mirror 2026 based on the structure shown in FIG. 6 a .
  • the mirror 2026 can be made of silicon nitride waveguide material.
  • the reflector 2026 is configured to transmit a first part of the light beam and output it as a laser signal, and reflect a second part of the light beam back to the first RSOA 201. In this way, the reflected light beam can be repeatedly oscillated in the frequency-tunable semiconductor laser 102 shown in FIG. Transmission output.
  • the start-up condition of the frequency tunable semiconductor laser 102 is expressed as the laser signal can be output when the gain of the laser signal in the frequency tunable semiconductor laser 102 is greater than the loss in the frequency tunable semiconductor laser 102 .
  • the wavelength of the output laser signal can be tuned.
  • another implementation mode It can also be implemented by using a distributed Bragg reflector (distributed bragg reflector, DBR).
  • DBR distributed bragg reflector
  • the optical resonant cavity 202 also includes a second waveguide converter 2024 and a distributed Bragg reflector DBR 2027; the DBR 2027 is made of a grating etched from a silicon nitride waveguide material.
  • the second waveguide converter 2024 includes a silicon waveguide and a silicon nitride waveguide, and is used to transmit the light beam from the first phase shifter 2023 made of the silicon waveguide material to the nitride
  • the first filter 2025a is made of silicon waveguide material.
  • the DBR 2027 is used to control the laser to output the frequency-tunable laser signal of a specified wavelength; and transmit the first part of the light beam as a laser signal, and transmit the second part of the light beam The light beam is reflected back to the first RSOA 201.
  • the structure of the frequency-tunable semiconductor laser provided in the third embodiment can achieve similar technical effects to that of the second embodiment.
  • the structure provided by Embodiment 3 can further reduce the number of optical elements contained in the frequency-modulated laser, which makes the structure of the frequency-modulated laser more simplified compared with Embodiment 2, and helps to reduce the size of the obtained frequency-modulated laser.
  • the present application also provides an embodiment.
  • the initial phase of the laser signal can be adjusted by the second phase shifter. Accurate, so as to help reduce the loss of the first phase shifter to generate the laser signal.
  • the optical resonator 202 may further include a second phase shifter 2028; the second phase shifter 2028 may be made of silicon waveguide material.
  • the second phase shifter 2028 is located between the first waveguide converter 2022 and the first phase shifter 2023, and is used to control and adjust the initial phase of the light beam by changing the refractive index in the optical resonant cavity, And output the adjusted light beam to the first phase shifter 2023 .
  • the second phase shifter 2028 can adjust the initial phase of the light beam by adjusting the driving current applied to the second phase shifter 2028 through a thermo-optic phase shifter, so as to achieve the best power output and reduce the loss.
  • the line width of the output laser signal can be reduced and the power of the output laser signal can be increased.
  • the thermo-optic phase shifter does not need doped regions, and the transmission of the light beam can be realized by heating the silicon waveguide, and it has the advantage of low loss.
  • the light beam transmitted to the first phase shifter can be at a better phase position, thereby reducing the transmission loss of the light beam in the first phase shifter, thereby ensuring The signal power of the laser signal output by the laser.
  • Figure 9 shows the structure of the frequency-modulated laser introduced in Embodiment 1, and the second phase shifter 2028 involved in Embodiment 4 can also be applied to Embodiment 2 or Embodiment 3. , which will not be repeated here.
  • the present application further provides an embodiment, which can realize the regulation of the output direction of the output laser signal.
  • FIG. 10 it is a schematic structural diagram of another frequency tunable semiconductor laser 102 provided by the embodiment of the present application.
  • the frequency tunable semiconductor laser 102 also includes a second SOA 204 and an optical phased array (optical phase array, OPA) scanner 206.
  • OPA optical phase array
  • the OPA scanner 206 can be made of silicon nitride waveguide material.
  • the second SOA 204 is used to receive the laser signal output by the optical resonator 202, and inject the output laser signal into the OPA scanner 206 after providing signal gain.
  • the second SOA 204 may adopt a U-shaped semiconductor optical amplifier, as in the structure shown in FIG. 10 .
  • the output power of the output laser signal can be increased through the second SOA 204, and at the same time, the transmission loss problem existing in the integration of silicon-based functional optical elements in the optical resonator 202 can be compensated, thereby improving the detection distance of the frequency-modulated laser.
  • the OPA scanner 206 is configured to regulate the output direction of the laser signal after providing signal gain. It should be noted that, under the design of this embodiment, the output direction of the laser signal can be adjusted based on the OPA scanner 206, and the target can be scanned. Therefore, if the frequency-tunable semiconductor laser 102 provided in this embodiment is used, compared with the FMCW lidar 100 shown in FIG. The frequency-tunable semiconductor laser 102 realizes the scanning of the target.
  • the OPA scanner 206 may also be an optical element independent of the frequency-tunable semiconductor laser 102 . It can be understood that after the frequency-tunable semiconductor laser 102 outputs a laser signal, the direction of the laser signal can be regulated by the OPA scanner 206 . Alternatively, it may also be implemented in an integrated manner as described in the above embodiments, which is not limited in this application.
  • the detection distance of the frequency-modulated laser can be improved.
  • the present application also provides a structure of a frequency-tunable semiconductor laser, using a third semiconductor optical amplifier to provide signal gain.
  • FIG. 11 it is a schematic structural diagram of another frequency tunable semiconductor laser 102 provided by the embodiment of the present application.
  • the frequency tunable semiconductor laser 102 also includes a third semiconductor optical amplifier SOA 205.
  • the first side of the first RSOA 201 can be coated with an anti-reflection film, and the second side can be coated with a low-reflection film, wherein the anti-reflection film means a film that can increase light transmission, and the low-reflection film Indicates a film with a certain reflective ability, such as a low-reflective film with a reflective ability of 30%.
  • the first side of the first RSOA 201 can be the coupling surface of the first RSOA 201 and the optical resonant cavity 202; the second side of the first RSOA 201 is the coupling surface of the first RSOA 201. The face opposite the first side.
  • Both the first side and the second side of the third SOA 205 may be coated with an anti-reflection film.
  • the first side of the third SOA 205 is the coupling plane between the third SOA 205 and the first RSOA 201; the second side of the third SOA 205 is the plane opposite to the first side of the third SOA 205. It should be noted that the first side and the second side are mainly used to distinguish different sides and can be used interchangeably.
  • the reflectivity of the reflector 2026 can be set to be greater than 95%, so that the reflector 2026 can reflect the light beam back to the first RSOA 201 along the emitted path through the reflector 2026, assuming that the second part of the light beam in the light beam is reflection. It should be noted that since there is usually no reflective mirror 2026 with a reflectivity of 100%, there may also be a first part of the light beam that is transmitted and output in the light beam.
  • the first RSOA 201 can also be used to transmit part of the second partial light beam reflected back by the reflector 2026 to the Another part of the third SOA can be reflectively injected into the optical resonant cavity 202 to continue to oscillate. Then, the third SOA is used to provide signal gain to the light beam transmitted through the low reflection film on the second side of the first RSOA 201 and then output it.
  • the output power of the output laser signal can be increased through the third SOA 205, and at the same time, the transmission loss problem existing in the integration of silicon-based functional optical elements in the optical resonator can be compensated, so that the detection distance of the frequency-modulated laser can be improved.
  • the present application also provides an implementation manner that can improve the linearity characteristic of the frequency-tunable semiconductor laser 102 .
  • the optical resonant cavity 202 may further include a frequency detection unit 2029 .
  • the frequency detection unit 2029 may include an auxiliary Mach-Zehnder interferometer (auxiliary mach-zehnder interferometer, AMZI) and a balanced photodetector (balanced photodetectors, BPD), and the BPD may be made of doped silicon waveguide material.
  • the frequency detection unit 2029 is configured to perform linear detection on the laser signal output by the optical resonant cavity 202 to obtain a linear detection result.
  • the driving circuit 203 may inject different driving currents into the first phase shifter according to the linearity detection result.
  • AMZI can be made of silicon nitride waveguide material, and the transmission loss based on silicon nitride waveguide is small, so it helps to reduce the power loss caused by using AMZI, so as to ensure the output laser signal power through the frequency detection unit 2029 .
  • the laser provided by this application has the characteristics of low loss and guaranteed output power by combining the silicon nitride waveguide in the optical resonator, and the silicon waveguide has the characteristics of fast modulation, which can provide A semiconductor laser that can satisfy fast frequency modulation, narrow linewidth and high power at the same time is of great significance to the development of lidar, optical communication and other fields.
  • the integration of the laser provided by the present application is simple, and also has the advantages of small size and low integration cost.
  • the application of the laser device provided by the present application can improve the detection distance and accuracy. For example, if the laser is applied to the laser radar technology, the point cloud density obtained by the laser radar detection can be improved.

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Abstract

一种频率可调谐的半导体激光器，用于提供一种耦合难度较低、且可同时满足快速调频、窄线宽、高功率的激光器。该激光器包括耦合的第一反射式半导体光放大器和光学谐振腔。光学谐振腔包括：由氮化硅波导材料制成的模斑转换器、第一波导转换器和由硅波导材料制成的第一移相器。第一反射式半导体光放大器，用于为光学谐振腔注入光束；模斑转换器，用于将第一反射式半导体光放大器输出的光斑尺寸，转换为第一波导转换器输入的光斑尺寸；第一波导转换器，包括氮化硅波导和硅波导，用于将光束从模斑转换器传输到第一移相器中；第一移相器，用于通过改变光学谐振腔内的折射率，控制改变光束的相位。

Description

一种频率可调谐的半导体激光器
相关申请的交叉引用
本申请要求在2021年06月29日提交中华人民共和国知识产权局、申请号为202110724813.5、申请名称为“一种频率可调谐的半导体激光器”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及激光器技术领域，尤其涉及一种频率可调谐的半导体激光器。
背景技术
频率可调谐的半导体激光器作为一种重要的光电器件，可应用于激光雷达、光通信等领域。例如，在激光雷达领域中，调频连续波(frequency modulated continuous wave，FMCW)激光雷达技术凭借具有更高的灵敏度和测距精度的优势，近年来受到越来越广泛的关注。而，FMCW激光雷达技术中最核心的便是频率可调谐的半导体激光器(可简称为“调频激光器”)。
目前，调频激光器例如可以是分布式反馈(distributed feedback，DFB)激光器，采用电注入的方式实现激光器的频率可调谐，但是由于DFB半导体激光器的谐振腔一般比较短，导致发射激光的线宽较大，并且，注入电流的热效应也会带来明显的调频非线性效应，从而降低了信噪比。调频激光器还可以使用回音壁模式的光学谐振腔技术，能够通过光反馈降低激光器的线宽，但是存在激光器结构复杂，需要多个光学元件进行空间光耦合，导致耦合难度较大，成本较高。
因此，提供一种可以同时满足快速调频、窄线宽、高功率以及耦合难度低的半导体激光器，对激光雷达、光通信等领域的发展具有重要意义。
发明内容
本申请提供一种频率可调谐的半导体激光器，用于提供一种耦合难度较低、且可以同时满足输出快速调频、窄线宽、高功率激光信号的半导体激光器。
第一方面，本申请提供一种频率可调谐的半导体激光器，包括第一反射式半导体光放大器和光学谐振腔；所述第一反射式半导体光放大器与所述光学谐振腔耦合；所述光学谐振腔包括：模斑转换器、第一波导转换器和第一移相器；其中，所述模斑转换器由氮化硅波导材料制成，所述第一移相器由硅波导材料制成；所述第一反射式半导体光放大器，用于为所述光学谐振腔注入光束；所述模斑转换器，用于将所述第一反射式半导体光放大器输出的光斑尺寸，转换为所述第一波导转换器输入的光斑尺寸；所述第一波导转换器，包括氮化硅波导和硅波导，用于将所述光束从所述模斑转换器传输到所述第一移相器中；所述第一移相器，用于通过改变光学谐振腔内的折射率，控制改变所述光束的相位，以使所述激光器输出频率可调谐的激光信号。
通过本申请提供的半导体激光器，在实现频率可调谐的光学谐振腔中，由于氮化硅波 导在传输光束时具有损耗低以及可以保障激光信号的输出功率的特性，硅波导具有较高的调制效率的特性。因此，一方面通过硅波导材料制成第一移相器，其响应时间几乎可以达到纳秒(ns)量级，从而可以通过改变施加在第一移相器上的电流来实现小范围的快速扫频，并且对应的激光功率和线宽变化不大。另一方面，本申请提供的半导体激光器的光学谐振腔中除第一移相器之外的其他功能光学元件可以采用氮化硅波导材料制成，从而可以保障传输激光信号时的功率等。可以理解，通过本申请设计的激光器，可以同时满足输出快速调频、窄线宽、高功率的激光信号特性，并且还具有耦合难度小的优势。进一步的，通过采用本申请设计的激光器，还可以提升激光探测时的探测距离和探测准确性。
在一种可能的设计中，所述第一移相器为PIN移相器。所述PIN移相器包括：I型不掺杂区域、P型掺杂区域和N型掺杂区域。所述激光器还包括驱动电路；所述驱动电路的正极连接在所述P型掺杂区域上，所述驱动电路的负极连接在所述N型掺杂区域上。所述驱动电路，用于为所述第一移相器注入不同的驱动电流，以使所述第一移相器改变光学谐振腔内的折射率。
基于以上第一移相器的设计，通过硅波导材料制成的电光移相器的响应时间很快，从而可以通过改变施加在第一移相器上的电流来实现小范围的快速扫频，并且对应的激光功率和线宽变化不大。此外，还可以设计PIN移相器的长度较长，从而使得第一移相器工作在较小载流子浓度的条件下，减小传输激光信号过程中的损耗。
在另一种可能的设计中，所述第一移相器为级联的多个PIN移相器。每个所述PIN移相器包括：I型不掺杂区域、P型掺杂区域和N型掺杂区域。所述级联的多个PIN移相器中，前一级PIN移相器的N型掺杂区域与后一级PIN移相器的P型掺杂区域连接。所述激光器还包括驱动电路；所述驱动电路的正极连接在所述第一移相器第一级PIN移相器的P型掺杂区域上，所述驱动电路的负极连接在所述第一移相器中的最后一级PIN移相器中的N型掺杂区域上。所述驱动电路，用于为所述第一移相器注入不同的驱动电流，以使所述第一移相器改变光学谐振腔内的折射率。
基于以上第一移相器的设计，一方面通过增加第一移相器的长度，从而使得第一移相器工作在较小载流子浓度的条件下，减小传输光束过程中的损耗。另一方面，通过级联结构能够提高整个第一移相器的驱动电压，相当于可提高每个PIN移相器能够获得的电压分辨率，进而可以提高移相精度。
在一种可能的设计中，所述光学谐振腔还包括第二波导转换器和级联的一个或多个滤波器。各所述滤波器由氮化硅波导材料制成。所述第二波导转换器，包括硅波导和氮化硅波导，用于将所述光束从所述硅波导材料制成的所述第一移相器传输到所述氮化硅波导材料制成的所述第一级滤波器中。所述级联的一个或多个滤波器，用于控制所述激光器输出指定波长的所述频率可调谐的激光信号。
在该设计中，本申请提供的半导体激光器除了可以实现频率可调谐的基础上，还可以进一步实现输出波长可调谐的激光信号。并且，滤波器同样可以采用氮化硅波导材料制成，可以保障输出激光信号时，降低产生激光信号过程中的损耗，从而可以保障输出的激光信号的功率。
在一种可能的设计中，所述光学谐振腔还包括反射镜。所述反射镜由氮化硅波导材料制成。所述反射镜，用于将所述光束中的第一部分光束透射输出为激光信号，并将所述光束中的第二部分光束反射回所述第一反射式半导体光放大器。
在该设计中，通常激光信号的输出需要光束在半导体激光器中进行多次反射，且达到激光可以输出的信号阈值时进行输出。本申请实施时，反射镜同样可以采用氮化硅波导材料制成。基于氮化硅波导材料制成的反射镜，可以保障输出激光信号时，降低产生激光信号过程中的损耗，从而可以保障输出的激光信号的功率。
在另一种可能的设计中，所述光学谐振腔还包括第二波导转换器和分布式布拉格反射器DBR。所述DBR由氮化硅波导材料制成。所述第二波导转换器，包括硅波导和氮化硅波导，用于将所述光束从所述硅波导材料制成的所述第一移相器传输到所述氮化硅波导材料制成的所述第一级滤波器中。所述DBR，用于控制所述激光器输出指定波长的所述频率可调谐的激光信号；以及将所述光束中的第一部分光束透射输出为激光信号，并将所述光束中的第二部分光束反射回所述第一反射式半导体光放大器。
在该设计中提供的激光器结构与前一种可能的设计可以达到相近的技术效果。并且，该设计提供的结构还可以进一步减少激光器中包含的光学元件数量，相比于前一种可能的设计，该设计可以使得频率可调谐的半导体激光器的结构更加简化，有助于减小得到的激光器的尺寸。
在一种可能的设计中，所述光学谐振腔还包括第二移相器；所述第二移相器由硅波导材料制成。所述第二移相器位于所述第一波导转换器与所述第一移相器之间，用于通过改变光学谐振腔内的折射率，控制所述光束的初始相位。
该设计中，通过第二移相器可以实现对激光信号初始相位的调整，使得光学谐振腔的纵模波长与滤波器的波长对准，进而可以实现最佳功率输出，减少传输损耗。这样，通过第二移相器可以对初始相位的调整，结合第一移相器可以进行快速调频，从而可以减小输出的激光信号的线宽，并且提高输出的激光信号的功率。因此，本申请提供的激光器可以同时满足输出可以快速调频、窄线宽和高功率的激光信号，从而可提升探测的距离和准确性。
在一种可能的设计中，还包括第二半导体光放大器和光学相控阵扫描器。所述第二半导体光放大器，用于接收所述光学谐振腔输出的激光信号，并为所述输出的激光信号提供信号增益之后，注入到所述光学相控阵扫描器上。所述光学相控阵扫描器，用于对提供信号增益之后的所述激光信号的输出方向进行调控。
该设计中，通过第二半导体光放大器可以提高输出的激光信号的输出功率，同时可补偿在光学谐振腔中集成硅基功能光学元件所存在的传输损耗问题，从而可以提升激光器的探测距离。以及，若采用该设计提供的激光器，还可以结合采用光学相控阵扫描器实现激光雷达中包含的发射光模组以及扫描器的功能，因此通过该设计下的激光器还可以实现对目标物的扫描，从而可以扩展激光器的功能，以及简化应用激光器的光设备的结构，例如，无需再在激光雷达中集成发射光模组和扫描器。
在一种可能的设计中，还包括第三半导体光放大器。所述第一反射式半导体光放大器，还用于将所述反射镜反射回的所述第二部分光束传输给所述第三半导体光放大器。所述第三半导体光放大器，用于为所述第二部分光束提供信号增益后进行输出。
在该设计中，通过第三半导体光放大器可以提高输出的激光信号的输出功率，同时可以补偿在光学谐振腔中集成硅基功能光学元件所存在的传输损耗问题，从而可以提升调频激光器的探测距离。
在另一种可能的设计中，所述第一反射式半导体光放大器的第一侧面镀有增透膜、第 二侧面镀有低反射膜。所述第一反射式半导体光放大器的第一侧面为所述第一反射式半导体光放大器与所述光学谐振腔的耦合面；第一反射式半导体光放大器的第二侧面为与所述第一反射式半导体光放大器的第一侧面相对的面。所述第三半导体光放大器的第一侧面和第二侧面上镀有增透膜。第三半导体光放大器的第一侧面为所述第三半导体光放大器与所述第一反射式半导体光放大器的耦合面；第三半导体光放大器的第二侧面为与所述第三半导体光放大器的第一侧面相对的面。
在该设计中，通过第三半导体光放大器也可以提高从第一反射式半导体光放大器的第二侧面输出的激光信号的输出功率，同时可以补偿在光学谐振腔中集成硅基功能光学元件所存在的传输损耗问题，从而可以提升调频激光器的探测距离。
在一种可能的设计中，所述光学谐振腔还包括频率检测单元。所述频率检测单元，用于对所述光学谐振腔输出的激光信号进行线性检测，得到线性检测结果。所述驱动电路为所述第一移相器注入不同的驱动电流时，具体用于根据所述线性检测结果为所述第一移相器注入不同的驱动电流。
在该设计中，通过对输出的激光信号进行线性检测，并根据得到的线性检测结果及时地调整驱动电路注入的驱动电流，以及时进行非线性补偿，从而可以输出具有较好的线性特性的激光信号。
第二方面，本申请实施例还提供一种光设备，包括如以上第一方面中任一可能的设计中的频率可调谐的半导体激光器。其中，所述频率可调谐的半导体激光器可用于输出频率可调谐的激光信号。
附图说明
图1为FMCW激光雷达的系统框图；
图2为本申请实施例提供的一种频率可调谐的半导体激光器102的结构示意图之一；
图3为本申请实施例提供的一种第一波导转换器2022的结构示意图；
图4为本申请实施例提供的一种频率可调谐的半导体激光器102的结构示意图之二；
图5a为本申请实施例提供的一种第一移相器2023的结构示意图；
图5b为本申请实施例提供的一种第一移相器2023的光信号传输示意图；
图5c为本申请实施例提供的另一种第一移相器2023的结构示意图；
图6a为本申请实施例提供的一种频率可调谐的半导体激光器102的结构示意图之三；
图6b为本申请实施例提供的一种滤波器2025的结构示意图；
图7为本申请实施例提供的一种频率可调谐的半导体激光器102的结构示意图之四；
图8为本申请实施例提供的一种频率可调谐的半导体激光器102的结构示意图之五；
图9为本申请实施例提供的一种频率可调谐的半导体激光器102的结构示意图之六；
图10为本申请实施例提供的一种频率可调谐的半导体激光器102的结构示意图之七；
图11为本申请实施例提供的一种频率可调谐的半导体激光器102的结构示意图之八；
图12为本申请实施例提供的一种频率可调谐的半导体激光器102的结构示意图之九。
具体实施方式
本申请实施例可以应用于包含频率可调谐的半导体激光器的多种技术中，例如激光雷 达、光学相干断层扫描(optical coherence tomography，OCT)等技术中。
以激光雷达技术作为示例，激光雷达可以广泛应用于机器人、自动驾驶、无人机等领域，可以利用激光来测量与目标物体之间的距离。目前，主流的激光雷达测距方法为脉冲飞行时间(time of flight，ToF)激光雷达。脉冲ToF激光雷达的原理为：通过发射高峰值功率的激光脉冲信号，测量从目标物体发射回来的光脉冲往返时间来实现距离探测。
相比脉冲TOF激光雷达，FMCW激光雷达具有更高的灵敏度和测距精度，可实现超远距离探测(通常可以大于300m)，且能够抗太阳光和其他激光的干扰和实时测速，是一种非常有潜力的激光雷达技术。FMCW激光雷达的原理为：采用相干测量技术，通过比较目标物体反射回来的反射信号频率与该时刻发射信号频率的差值来得到目标物体的距离信息。
例如，图1为FMCW激光雷达的系统框图。FMCW激光雷达100可以包括：信号控制101、频率可调谐的半导体激光器102(也可以简称为“调频激光器”，以下实施例中“频率可调谐的半导体激光器”和“调频激光器”可被互相替换使用)、发射光模组103、扫描器104、接收光模组105、平衡探测器106和信号处理系统107。其中，信号控制101发出控制信号，使得频率可调谐的半导体激光器102发出频率调制的连续激光。激光经过发射光模组103被分为两束，一束为本征光，另一束为信号光。信号光经过扫描器104照射到目标物上。从目标物反射回来的信号光通过接收光模组105接收，且与本征光在平衡探测器106上进行混频，得到拍频电信号。最后，平衡探测器106输出的拍频电信号发送到信号处理系统107上进行分析，输出3D点云图像以及得到目标物的速度信息，进而可以计算得到目标物的距离信息。
基于以上对激光雷达的原理的介绍，可以得到在应用调频激光器的技术领域中，为了得到更准确的探测结果，对调频激光器的要求非常高。例如，对激光雷达来说，为了实现较长的探测距离和足够高的点云密度，需要调频激光器可以发射具有足够快的调频速率、足够窄的线宽、较高的光功率和调频线性度的激光。
目前，现有技术中存在通过为分布式反馈(distributed feedback laser，DFB)半导体激光器直接注入变换的电流，基于变换的电流改变DFB半导体激光器腔体内的折射率，从而实现DFB半导体激光器可以发射具有较快调频速率的激光。然而，由于DFB半导体激光器的谐振腔一般比较短，从而导致采用该技术方案发射的激光的线宽比较大。并且，基于电流注入的方式具有热效应，热效应会带来较为明显的非线性效应，从而会降低探测信号的信噪比。
现有技术中还存在另一种技术方案为，DFB半导体激光器发出激光，通过第一光学耦合器耦合到回音壁模式(whispering gallery mode，WGM)谐振器中。DFB半导体激光器发射的激光中，只有满足WGM谐振器的谐振模式的激光才能耦合进WGM谐振器。这样，DFB半导体激光器通过注入式锁频在WGM谐振器的谐振频率上，使得输出激光的线宽得到压缩，从而可以获得具有较窄线宽的激光。且通过电光效应可以快速改变WGM谐振器频率，从而可以实现激光调频。然而，该技术方案的结构复杂，需要多个光学元件进行空间光耦合，因此存在耦合难度大，集成的成本高的缺陷。并且，WGM谐振器反馈注入锁频的效率受限于反馈回DFB半导体激光器的激光比例，因此也无法实现激光的高功率输出。
有鉴于此，如何实现调频激光器可以发射具有足够快的调频速率、足够窄的线宽、较高的光功率和调频线性度的激光信号，现有技术中尚未提供一种较好的技术方案。因此， 提供一种可以同时满足输出快速调频、窄线宽、高功率的激光信号且耦合难度较低的半导体激光器，对激光雷达、光通信等领域的发展具有重要意义。本申请提供的调频激光器，由于氮化硅波导具有损耗低、功率上限高等优势，以及硅波导可以实现快速调频的特性，从而可以结合采用两种波导的光学元件来提供一种频率可调谐的半导体激光器。
下面将结合附图并采用多个实施例对本申请作进一步地详细描述。
需要说明的是，在本申请的各个实施例中，如果没有特殊说明以及逻辑冲突，不同的实施例之间的术语和/或描述具有一致性、且可以相互引用，不同的实施例中的技术特征根据其内在的逻辑关系可以组合形成新的实施例。本申请中，“至少一个”是指一个或者多个，“多个”是指两个或两个以上。可以理解的是，在本申请中涉及的各种数字编号仅为描述方便进行的区分，并不用来限制本申请的实施例的范围。上述各过程的序号的大小并不意味着执行顺序的先后，各过程的执行顺序应以其功能和内在逻辑确定。术语“第一”、“第二”等是用于分区别类似的对象，而不必用于描述特定的顺序或先后次序。
此外，术语“包括”和“具有”以及他们的任何变形，意图在于覆盖不排他的包含，例如，包含了一系列步骤或单元。方法、系统、产品或设备不必限于清楚地列出的那些步骤或单元，而是可包括没有清楚地列出的或对于这些过程、方法、产品或设备固有的其它步骤或单元。
实施例一
参阅图2，为本申请实施例提供的一种频率可调谐的半导体激光器102的结构示意图。该频率可调谐的半导体激光器102包括第一反射式半导体光放大器(reflex semiconductor optical amplifier，RSOA)201和光学谐振腔202。第一RSOA 201与光学谐振腔202耦合。
其中，第一RSOA 201，用于为所述光学谐振腔注入光束。并且在注入之前为光束提供信号增益，也可以理解为进行信号放大，以补偿光束在光学谐振腔中振荡时产生的损耗。一种可选的实施方式为，可以在第一RSOA 201的第一侧面上镀增透膜，在第二侧面上镀高反膜。其中，第一侧面为第一RSOA 201与光学谐振腔202的耦合面，如图2中第一RSOA 201的右侧面；第二侧面为与第一RSOA 201的第一侧面相对的面，如图2中第一RSOA 201的左侧面。可以理解，光束在第二侧面上可以被反射，在第一侧面上可以被透射，这样第一RSOA 201可以通过第一侧面上的增透膜将光束注入到光学谐振腔202中进行振荡。并且，第一RSOA 201的有源区可以采用III-V量子阱或量子点材料实现。
接下来，所述光学谐振腔202具体可以包括：模斑转换器2021、第一波导转换器2022和第一移相器2023。其中，所述模斑转换器2021可由氮化硅波导材料制成，所述第一移相器2023可由硅波导材料制成。
示例性的，第一RSOA 201的输出端与模斑转换器2021的输入端可以采用对接耦合的方式进行连接，或者还可以采用其他方式进行耦合，本申请不进行限定。
其中，模斑转换器2021可以采用倒锥形耦合器、悬空波导耦合器或三叉戟耦合器等结构实现。实现时可以根据第一RSOA 201的输出光斑尺寸与第一波导转换器2022的输入光斑尺寸的实际场景，来确定模斑转换器2021采用的结构。
实施时，所述模斑转换器2021，用于将所述第一RSOA 201输出的光斑尺寸，转换为第一波导转换器2022输入的光斑尺寸。或者，若光束的传输方向为从第一波导转换器2022到第一RSOA 201的场景下，所述模斑转换器2021，还可以用于将所述第一波导转换器2022输出的光斑尺寸，转换为所述第一RSOA 201输入的光斑尺寸。这样可以提高第一RSOA  201与光学谐振腔202的耦合效率，减少光束在第一RSOA 201与光学谐振外腔202之间进行谐振时产生的损耗。
实施时，所述第一波导转换器2022，包括氮化硅波导和硅波导，用于将所述光束从所述氮化硅波导材料制成的所述模斑转换器2021传输到所述硅波导材料制成的所述第一移相器2023中。或者，若光束的传输方向为从第一移相器2023到模斑转换器2021的场景下，可将来自第一移相器2023的光束传输给模斑转换器2021。可以理解，由于模斑转换器2021采用氮化硅波导材料制成，第一移相器2023采用硅波导材料制成，光束在不同的传输波导材料上具有不同的传输特性，为了实现光束可以在两种不同的材料上的信号传输，因此可以采用第一波导转换器2022来实现转换。
示例性的，参阅图3，为本申请实施例提供的一种第一波导转换器2022的结构示意图。该示例中，第一波导转换器2022主要可以由上下两层波导实现，上层波导可以为锥形氮化硅波导，下层波导可以为倒锥形硅波导。两层波导可以通过垂直耦合方式进行光传输。实施时，光束从第一波导转换器2022中的锥形氮化硅波导的输入端(如图3中的A端)进入第一波导转换器2022中，在传输至锥形氮化硅波导的输入端(如图3中的B端)时，光束可以继续传输至倒锥形硅波导的输入端(如图3中的C端)，最后从倒锥形硅波导的输出端(如图3中的D端)输出给第一移相器2023。这样，通过第一波导转换器2022的传输，可以实现光束在不同波导材料制成的光学元件之间的传输，从而可以实现结合不同波导材料的传输特征设计本申请提供的激光器。
具体实施时，所述第一移相器2023，用于通过改变光学谐振腔202内的折射率，控制改变所述光束的相位，以使所述激光器输出频率可调谐的激光信号。通过硅波导材料制成的第一移相器2023，其响应时间几乎可以达到纳秒(ns)量级，从而可以通过改变施加在第一移相器2023上的电流来实现小范围的快速扫频，并且对应的激光功率和线宽变化不大。可以理解，基于氮化硅波导具有损耗低、功率上限高的优势，再结合由硅波导材料制成的移相器，可以实现对光束进行快速调频，因此通过本申请提供的频率可调谐的半导体激光器可以同时满足快速调频、窄线宽、高功率以及耦合难度低的特性。
基于上述设计，本申请提供的频率可调谐的半导体激光器102还可以包括驱动电路。参阅图4，为本申请实施例提供的另一种频率可调谐的半导体激光器102的结构示意图。频率可调谐的半导体激光器102还包括驱动电路203。所述驱动电路203用于为所述第一移相器2023注入不同的驱动电流，以使所述第一移相器2023改变光学谐振腔内的折射率。其中，驱动电路203可以通过图1中介绍到的信号控制101实现，或者也可以通过单独的芯片实现等。
一种可能的实现方式中，第一移相器2023可以为由硅刻蚀并掺杂形成的PIN移相器。参阅图5a，为本申请实施例提供的一种第一移相器2023的结构示意图。PIN移相器包括：I型不掺杂区域、P型掺杂区域和N型掺杂区域。其中，I型不掺杂区域为硅波导。并且，第一移相器2023与驱动电路203的具体连接方式可以为，驱动电路203的正极与PIN移相器的P型掺杂区域连接，驱动电路203的负极与PIN移相器的N型掺杂区域连接。可选的，PIN移相器可以是由响应时间几乎可以达到ns量级的电光移相器组成。
本申请实施时，可以改变通过驱动电路203施加在第一移相器2023上的驱动电流，从而可以实现小范围频率的快速扫频，并且对应的激光功率和线宽变化不大。例如，参阅图5b，为本申请实施例提供的一种第一移相器2023的光信号传输示意图。并且由于光束 在光学谐振腔中进行振荡，因此第一移相器2023可以从两个方向接收光束。例如第一方向可以为第一RSOA 201出射光束的方向，第二方向可以为后续实施例中介绍到的反射镜反射回来的光束方向。光束可以在I型不掺杂区域的硅波导进行传输，同时P型掺杂区域和N型掺杂区域接收驱动电路203的驱动电流的控制，以实现对输出的激光信号的频率进行调谐。
此外，通过增加第一移相器的长度，还可以使得第一移相器工作在较小载流子浓度的条件下，减小传输光束过程中的损耗。因此，一种实现方式中，可以将图5a示出的PIN移相器的长度设计为较长的长度，如可以设计为大于1毫米(mm)。
另一种可能的实现方式中，第一移相器2023还可以通过级联的多个PIN移相器组成，以得到较长长度的第一移相器2023，其中每个PIN移相器如图5a和图5b示出的结构和光信号传输原理。参阅图5c，为本申请实施例提供的另一种第一移相器2023的结构示意图。级联的多个PIN移相器中，前一级PIN移相器的N型掺杂区域与后一级PIN移相器的P型掺杂区域连接；例如，前一级PIN移相器的N型掺杂区域与后一级PIN移相器的P型掺杂区域可以通过导电的金属电极进行连接。在图5c示出的第一移相器2023中，驱动电路203的正极可以连接在所述第一移相器2023第一级PIN移相器的P型掺杂区域上，所述驱动电路203的负极可以连接在所述第一移相器2023中的最后一级PIN移相器中的N型掺杂区域上。所述驱动电路203，用于为所述第一移相器2023注入不同的驱动电流，以使所述第一移相器2023改变光学谐振腔202内的折射率。
可选的，一个PIN移相器或者级联的多个PIN移相器的长度可以设计为大于1毫米(mm)，此时通过一个PIN移相器或者级联的多个PIN移相器构成的第一移相器2023具有损耗低和移相精度高的优势。
基于以上第一移相器的设计，通过级联结构能够提高整个第一移相器的驱动电压，相当于提高了每个PIN移相器能够获得的电压分辨率，进而在减小传输损耗时，还可以提高移相精度。
实施例二
在通过实施例一介绍到的内容可以实现频率可调谐的半导体激光器102的频率可调谐的基础上，进一步还可以实现输出的激光信号波长的可调谐。
示例性的，可以通过增加滤波器来实现波长的可调谐。参阅图6a，为本申请实施例提供的又一种频率可调谐的半导体激光器102的结构示意图。所述光学谐振腔202在实施例一介绍的结构的基础上，还可以包括第二波导转换器2024和级联的一个或多个滤波器2025(图6a以级联的两个滤波器为示例，即第一滤波器2025a和第二滤波器2025b为例进行说明)。
其中，各所述滤波器2025，即第一滤波器2025a和第二滤波器2025b可由氮化硅波导材料制成，第一移相器2023由硅波导材料制成，因此可以采用第二波导转换器2024实现光束在两种不同的波导材料上的信号传输。与第一波导转换器2022不同之处为，在第一RSOA 201注入光束方向上，第一波导转换器2022为氮化硅波导材料到硅波导材料的转换器，第二波导转换器2024为硅波导材料到氮化硅波导材料的转换器。
基于图6a示出的频率可调谐的半导体激光器102的结构，所述第二波导转换器2024，包括硅波导和氮化硅波导，用于将所述光束从所述硅波导材料制成的所述第一移相器2023传输到所述氮化硅波导材料制成的所述第一滤波器2025a中。所述级联的一个或多个滤波 器2025，用于控制所述激光器输出指定波长的所述频率可调谐的激光信号，从而可以实现激光器输出的激光信号的频率可调谐。
示例性，如图6a所示，级联的一个或多个滤波器2025假设包括第一滤波器2025a和第二滤波器2025b，第一滤波器2025a和第二滤波器2025b可以为微环滤波器。由于两个微环滤波器不同，可以基于光学中的游标效应实现输出的激光信号的波长可调谐。或者，另一种可选的实施方式中，激光器还可以采用其他类型的滤波器实现，且选用滤波器的数量可以根据实际需求确定，本申请对此不进行限定。
实施时还可以通过在滤波器2025上集成热光移相器实现波长可调谐。参阅图6b，为本申请实施例提供的一种滤波器2025的结构示意图。通过分别调节各级滤波器2025上的热光移相器的驱动电流的大小，进而可实现激光器输出不同指定波长的激光信号。
参阅图7，为本申请实施例提供的又一种频率可调谐的半导体激光器102的结构示意图。所述光学谐振腔202在基于图6a示出的结构上，还可以包括反射镜2026。所述反射镜2026可由氮化硅波导材料制成。所述反射镜2026，用于将所述光束中的第一部分光束透射输出为激光信号，并将所述光束中的第二部分光束反射回所述第一RSOA 201。这样，被反射回的光束可以在图7示出的频率可调谐的半导体激光器102中进行反复振荡，并在光束达到频率可调谐的半导体激光器102的起振条件时，通过反射镜2026的输出端透射输出。其中频率可调谐的半导体激光器102的起振条件表示为激光信号在频率可调谐的半导体激光器102中的增益大于在该频率可调谐的半导体激光器102中的损耗时，激光信号可以进行输出。
实施例三
在通过实施例一介绍到的内容可以实现频率可调谐的半导体激光器102的频率可调谐的基础上，实现输出的激光信号波长的可调谐除了实施例二的实施方式之外，另一种实施方式还可以采用分布式布拉格反射器(distributed bragg reflector，DBR)来实现。
参阅图8，为本申请实施例提供的另一种频率可调谐的半导体激光器102的结构示意图。所述光学谐振腔202还包括第二波导转换器2024和分布式布拉格反射器DBR 2027；所述DBR 2027由氮化硅波导材料刻蚀的光栅制成。
实施时，所述第二波导转换器2024，包括硅波导和氮化硅波导，用于将所述光束从所述硅波导材料制成的所述第一移相器2023传输到所述氮化硅波导材料制成的所述第一滤波器2025a中。所述DBR 2027，用于控制所述激光器输出指定波长的所述频率可调谐的激光信号；以及将所述光束中的第一部分光束透射输出为激光信号，并将所述光束中的第二部分光束反射回所述第一RSOA 201。
实施例三提供的频率可调谐的半导体激光器的结构与实施例二可以达到相近的技术效果。并且，实施例三提供的结构还可以进一步减少调频激光器中包含的光学元件的数量，相比于实施例二使得调频激光器的结构更加简化，有助于减小得到的调频激光器的尺寸。
实施例四
在前述几个实施例的基础上，本申请还提供一种实施例，在对光束通过第一移相器进行调频处理之前，还可以先通过第二移相器对激光信号的初始相位进行对准，从而可以有助于减少第一移相器对产生激光信号产生的损耗。
参阅图9，为本申请实施例提供的再一种频率可调谐的半导体激光器102的结构示意图。所述光学谐振腔202还可以包括第二移相器2028；所述第二移相器2028可由硅波导 材料制成。所述第二移相器2028位于所述第一波导转换器2022与所述第一移相器2023之间，用于通过改变光学谐振腔内的折射率，控制调节所述光束的初始相位，并将调整后的所述光束输出给所述第一移相器2023。
可选的，第二移相器2028可以通过热光移相器，通过调节施加在第二移相器2028上的驱动电流，实现对光束初始相位的调整，进而可以实现最佳功率输出，减少损耗。这样，通过第二移相器2028对光束初始相位的调整，结合第一移相器2023对光束进行快速调频，从而可以减小输出的激光信号的线宽，并且提高输出的激光信号的功率。其中，热光移相器相比于电光移相器，无需掺杂区域，通过对硅波导进行加热，可以实现光束的传输，并且存在损耗低的优势。并且，通过热光移相器实现初始相位的调整之后，可以使得传输至第一移相器的光束处于较佳的相位位置，从而可以降低光束在第一移相器中的传输损耗，进而保障激光器输出的激光信号的信号功率。
需要说明的是，图9示出的是以实施例一所介绍的调频激光器的结构进行介绍的，该实施例四中涉及的第二移相器2028也可以适用于实施例二或实施例三中，在此不再赘述。
实施例五
基于前述实施例一至实施例四中的任一实施例，本申请还提供一种实施例，可以实现对输出的激光信号的输出方向进行调控。
参阅图10，为本申请实施例提供的再一种频率可调谐的半导体激光器102的结构示意图。所述频率可调谐的半导体激光器102还包括第二SOA 204和光学相控阵(optical phase array，OPA)扫描器206。其中，所述OPA扫描器206可由氮化硅波导材料制成。
实施时，所述第二SOA 204，用于接收所述光学谐振腔202输出的激光信号，并对所述输出的激光信号提供信号增益之后，注入到所述OPA扫描器206上。可选的，第二SOA 204可以采用U型半导体光放大器，如图10所示出的结构。通过第二SOA 204可以提高输出的激光信号的输出功率，同时补偿在光学谐振腔202中集成硅基功能光学元件所存在的传输损耗问题，从而可以提升调频激光器的探测距离。
所述OPA扫描器206，用于对提供信号增益之后的所述激光信号的输出方向进行调控。需要说明的是，在该实施例的设计下，基于OPA扫描器206可以实现调控激光信号的输出方向，并且可以进行对目标物的扫描。因此，若采用该实施方式提供的频率可调谐的半导体激光器102，相比于图1示出的FMCW激光雷达100，可以采用OPA扫描器206实现发射光模组103以及扫描器104的功能，通过频率可调谐的半导体激光器102实现对目标物的扫描。
此外，需要说明的是，OPA扫描器206也可以是与频率可调谐的半导体激光器102相互独立的光学元件。可以理解为，频率可调谐的半导体激光器102输出激光信号之后，可以通过OPA扫描器206实现对激光信号方向的调控。或者，也可以是如上实施例介绍的集成方式实现，本申请对此不进行限定。
实施例六
为了补偿在光学谐振腔中集成硅基功能光学元件所存在的传输损耗问题，从而可以提升调频激光器的探测距离。除了实施例五示出的实施方式之外，另一种实施方式中，本申请还提供一种频率可调谐的半导体激光器的结构，采用第三半导体光放大器为光学谐振腔中输出的激光信号提供信号增益。
参阅图11，为本申请实施例提供的又一种频率可调谐的半导体激光器102的结构示意 图。该频率可调谐的半导体激光器102还包括第三半导体光放大器SOA 205。
在该实施方式中，所述第一RSOA 201的第一侧面可镀有增透膜、第二侧面可镀有低反射膜，其中，增透膜表示可以增加透光量的膜，低反射膜表示具有一定反射能力的膜，例如反射能力为30％的低反射膜。如图11所示，第一RSOA 201的第一侧面可以为所述第一RSOA 201与所述光学谐振腔202的耦合面；第一RSOA 201的第二侧面为与所述第一RSOA 201的第一侧面相对的面。所述第三SOA 205的第一侧面和第二侧面上可均镀有增透膜。第三SOA 205的第一侧面为所述第三SOA 205与所述第一RSOA 201的耦合面；第三SOA 205的第二侧面为与所述第三SOA 205的第一侧面相对的面。需要说明的是，第一侧面和第二侧面主要是用于区分不同的侧面，可以被互相替换使用。
可选的，可以设置反射镜2026的反射率大于95％，以实现反射镜2026可以将光束通过反射镜2026沿发射来的路径反射回第一RSOA 201中，假设光束中的第二部分光束被反射。需要说明的是，由于通常不存在反射率为100％的反射镜2026，因此光束中还可能会存在第一部分光束被透射输出。
基于以上第一RSOA 201的第二侧面上的低反射膜的设计，所述第一RSOA 201还可以用于将所述反射镜2026反射回的所述第二部分光束中的部分传输给所述第三SOA，另一部分可以反射注入到光学谐振腔202中继续进行振荡。然后，所述第三SOA用于对通过第一RSOA 201的第二侧面上的低反射膜透射的光束提供信号增益之后输出。这样，通过第三SOA 205可以提高输出的激光信号的输出功率，同时补偿在光学谐振腔中集成硅基功能光学元件所存在的传输损耗问题，从而可以提升调频激光器的探测距离。
实施例七
基于前述实施例一至实施例六介绍到的内容，本申请还提供了一种可以提高频率可调谐的半导体激光器102的线性特性的实施方式。
参阅图12，为本申请实施例提供的再一种频率可调谐的半导体激光器102的结构示意图。所述光学谐振腔202还可以包括频率检测单元2029。可选的，频率检测单元2029可以包括辅助的马赫-曾德尔干涉仪(auxiliary mach-zehnder interferometer，AMZI)和平衡光电探测器(balanced photodetectors，BPD)，BPD可由掺杂的硅波导材料制成。
实施时，所述频率检测单元2029，用于对所述光学谐振腔202输出的激光信号进行线性检测，得到线性检测结果。相应地，所述驱动电路203可以根据所述线性检测结果为所述第一移相器注入不同的驱动电流。
此外，AMZI可由氮化硅波导材料制成，基于氮化硅波导的传输损耗较小，因此有助于减小采用AMZI引起的功率损耗，从而保障通过频率检测单元2029输出的激光信号功率。
通过以上几种可能的实施例可以得到，本申请提供的激光器通过在光学谐振腔中结合氮化硅波导具有损耗低和保障输出功率的特性，以及硅波导具有可以实现快速调制的特性，可以提供一种可以同时满足快速调频、窄线宽以及高功率的半导体激光器，对激光雷达、光通信等领域的发展具有重要意义。并且，本申请提供的激光器的集成简单，还具有尺寸小、集成化成本低的优势。以及，应用本申请提供的激光器的设备，可以提升探测的距离和精度，例如假设激光器应用于激光雷达技术中，可以提高激光雷达探测得到的点云密度。
尽管结合具体特征及其实施例对本申请进行了描述，显而易见的，在不脱离本申请的精神和范围的情况下，可对其进行各种修改和组合。相应地，本说明书和附图仅仅是所附 权利要求所界定的方案进行示例性说明，且视为已覆盖本申请范围内的任意和所有修改、变化、组合或等同物。
显然，本领域的技术人员可以对本申请进行各种改动和变型而不脱离本发明的精神和范围。这样，倘若本申请实施例的这些修改和变型属于本申请权利要求及其等同技术的范围之内，则本申请也意图包含这些改动和变型在内。

Claims (11)

  1. 一种频率可调谐的半导体激光器，其特征在于，包括第一反射式半导体光放大器和光学谐振腔；所述第一反射式半导体光放大器与所述光学谐振腔耦合；
    所述光学谐振腔包括：模斑转换器、第一波导转换器和第一移相器；其中，所述模斑转换器由氮化硅波导材料制成，所述第一移相器由硅波导材料制成；
    所述第一反射式半导体光放大器，用于为所述光学谐振腔注入光束；
    所述模斑转换器，用于将所述第一反射式半导体光放大器输出的光斑尺寸，转换为所述第一波导转换器输入的光斑尺寸；
    所述第一波导转换器，包括氮化硅波导和硅波导，用于将所述光束从所述模斑转换器传输到所述第一移相器中；
    所述第一移相器，用于通过改变光学谐振腔内的折射率，控制改变所述光束的相位，以使所述激光器输出频率可调谐的激光信号。
  2. 根据权利要求1所述的激光器，其特征在于，所述第一移相器为PIN移相器；所述PIN移相器包括：I型不掺杂区域、P型掺杂区域和N型掺杂区域；
    所述激光器还包括驱动电路；所述驱动电路的正极连接在所述P型掺杂区域上，所述驱动电路的负极连接在所述N型掺杂区域上；
    所述驱动电路，用于为所述第一移相器注入不同的驱动电流，以使所述第一移相器改变光学谐振腔内的折射率。
  3. 根据权利要求1所述的激光器，其特征在于，所述第一移相器为级联的多个PIN移相器；每个所述PIN移相器包括：I型不掺杂区域、P型掺杂区域和N型掺杂区域；
    所述级联的多个PIN移相器中，前一级PIN移相器的N型掺杂区域与后一级PIN移相器的P型掺杂区域连接；
    所述激光器还包括驱动电路；所述驱动电路的正极连接在所述第一移相器第一级PIN移相器的P型掺杂区域上，所述驱动电路的负极连接在所述第一移相器中的最后一级PIN移相器中的N型掺杂区域上；
    所述驱动电路，用于为所述第一移相器注入不同的驱动电流，以使所述第一移相器改变光学谐振腔内的折射率。
  4. 根据权利要求1至3中任一项所述的激光器，其特征在于，所述光学谐振腔还包括第二波导转换器和级联的一个或多个滤波器；各所述滤波器由氮化硅波导材料制成；
    所述第二波导转换器，包括硅波导和氮化硅波导，用于将所述光束从所述硅波导材料制成的所述第一移相器传输到所述氮化硅波导材料制成的所述第一级滤波器中；
    所述级联的一个或多个滤波器，用于控制所述激光器输出指定波长的所述频率可调谐的激光信号。
  5. 根据权利要求4所述的激光器，其特征在于，所述光学谐振腔还包括反射镜；所述反射镜由氮化硅波导材料制成；
    所述反射镜，用于将所述光束中的第一部分光束透射输出为激光信号，并将所述光束中的第二部分光束反射回所述第一反射式半导体光放大器。
  6. 根据权利要求1至3中任一项所述的激光器，其特征在于，所述光学谐振腔还包括第二波导转换器和分布式布拉格反射器DBR；所述DBR由氮化硅波导材料制成；
    所述第二波导转换器，包括硅波导和氮化硅波导，用于将所述光束从所述硅波导材料制成的所述第一移相器传输到所述氮化硅波导材料制成的所述第一级滤波器中；
    所述DBR，用于控制所述激光器输出指定波长的所述频率可调谐的激光信号；以及将所述光束中的第一部分光束透射输出为激光信号，并将所述光束中的第二部分光束反射回所述第一反射式半导体光放大器。
  7. 根据权利要求4至6中任一项所述的激光器，其特征在于，所述光学谐振腔还包括第二移相器；所述第二移相器由硅波导材料制成；
    所述第二移相器位于所述第一波导转换器与所述第一移相器之间，用于通过改变光学谐振腔内的折射率，控制所述光束的初始相位。
  8. 根据权利要求1至7中任一项所述的激光器，其特征在于，还包括第二半导体光放大器和光学相控阵扫描器；
    所述第二半导体光放大器，用于接收所述光学谐振腔输出的激光信号，并为所述输出的激光信号提供信号增益之后，注入到所述光学相控阵扫描器上；
    所述光学相控阵扫描器，用于对提供信号增益之后的所述激光信号的输出方向进行调控。
  9. 根据权利要求5所述的激光器，其特征在于，还包括第三半导体光放大器；
    所述第一反射式半导体光放大器，还用于将所述反射镜反射回的所述第二部分光束传输给所述第三半导体光放大器；
    所述第三半导体光放大器，用于为所述第二部分光束提供信号增益后进行输出。
  10. 根据权利要求9所述的激光器，其特征在于，所述第一反射式半导体光放大器的第一侧面镀有增透膜、第二侧面镀有低反射膜；所述第一反射式半导体光放大器的第一侧面为所述第一反射式半导体光放大器与所述光学谐振腔的耦合面；第一反射式半导体光放大器的第二侧面为与所述第一反射式半导体光放大器的第一侧面相对的面；
    所述第三半导体光放大器的第一侧面和第二侧面上镀有增透膜；第三半导体光放大器的第一侧面为所述第三半导体光放大器与所述第一反射式半导体光放大器的耦合面；第三半导体光放大器的第二侧面为与所述第三半导体光放大器的第一侧面相对的面。
  11. 根据权利要求2或3所述的激光器，其特征在于，所述光学谐振腔还包括频率检测单元；
    所述频率检测单元，用于对所述光学谐振腔输出的激光信号进行线性检测，得到线性检测结果；
    所述驱动电路为所述第一移相器注入不同的驱动电流时，具体用于：根据所述线性检测结果为所述第一移相器注入不同的驱动电流。
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