Frequency-modulated continuous wave lidar and its driving method

Abstract

This application provides a frequency-modulated continuous wave (FM-MCW) lidar and a driving method for the FM-MCW lidar. The FM-MCW lidar includes a light source, a transceiver module, a detection module, and a data processing module. The light source includes an active optical chip and a passive optical chip. The active optical chip has a gain region and a phase region. The gain region is used to generate a modulated laser beam based on a received driving signal, and the phase region is used to perform phase compensation on the modulated laser beam based on a received phase compensation signal to increase the modulation bandwidth of the modulated laser beam. The active optical chip provides the phase-compensated modulated laser beam to the passive optical chip, which then outputs it to the transceiver module. This application solves the problem of low measurement accuracy and unstable performance in related technologies' FM-MCW lidar, where the light source cannot achieve high-speed, large-bandwidth frequency modulation while maintaining a narrow linewidth.

Description

Technical Field

[0001] This application relates to the field of lidar, and more specifically, to a frequency modulated continuous wave lidar and a driving method for the frequency modulated continuous wave lidar. Background Technology

[0002] In recent years, LiDAR has been widely used in robotics, space mapping, AR (Augmented Reality) / VR (Virtual Reality) and other fields, and has received widespread attention with the rapid development of autonomous driving technology. Compared with LiDAR that uses time-of-flight methods for ranging, FMCW (Frequency Modulated Continuous Wave) LiDAR can simultaneously measure the distance and velocity of an object, while also possessing advantages such as low power consumption, high resolution, and strong anti-interference capabilities, making it highly competitive in detection fields that require high resolution and high accuracy.

[0003] However, during the use of FMCW lidar, there is a certain contradiction between linewidth and modulation bandwidth. Narrow linewidth is beneficial to improve the measurement sensitivity and detection range of the lidar, but excessively narrow linewidth will limit the modulation bandwidth, thereby affecting the distance resolution and measurement range of the lidar. In addition, there is a conflict between linewidth and modulation bandwidth, which can easily cause the lidar mode to jump.

[0004] It is evident that frequency-modulated continuous wave lidar in related technologies suffers from problems such as low measurement accuracy and unstable performance due to the inability of the light source to achieve high-speed, large-bandwidth frequency modulation while maintaining a narrow linewidth. Summary of the Invention

[0005] This application provides a frequency-modulated continuous wave lidar and a driving method for the frequency-modulated continuous wave lidar, so as to at least solve the problems of low measurement accuracy and unstable performance of the frequency-modulated continuous wave lidar in the related art, which are caused by the inability of the light source to achieve high-speed and large-bandwidth frequency modulation while maintaining narrow linewidth.

[0006] According to one aspect of the embodiments of this application, a frequency-modulated continuous wave lidar is provided, comprising: a light source, a transceiver module, a detection module, and a data processing module. The light source includes an active optical chip and a passive optical chip. The active optical chip is provided with a gain region and a phase region. The gain region is used to generate a modulated laser beam based on a received driving signal. The phase region is used to perform phase compensation on the modulated laser beam based on a received phase compensation signal to increase the modulation bandwidth of the modulated laser beam. The active optical chip provides the phase-compensated modulated laser beam to the passive optical chip, which then outputs it to the transceiver module.

[0007] In an exemplary embodiment, the frequency-modulated continuous wave lidar further includes a driving circuit; wherein the driving circuit is configured to generate the driving signal and provide it to the gain region, wherein the driving signal is a superposition signal of a DC bias signal and a modulation signal; and to generate the phase compensation signal and provide it to the phase region; the gain region is further configured to generate a laser beam according to the DC bias signal and to modulate the laser beam according to the modulation signal to form the modulated laser beam.

[0008] In an exemplary embodiment, the passive optical chip includes: an input end-face modulated beam converter, a wavelength selection feedback module, and an output end-face modulated beam converter; wherein, the phase-compensated modulated laser beam is transmitted to the passive optical chip through the input end-face modulated beam converter, a portion of the phase-compensated modulated laser beam enters the resonant cavity composed of the active optical chip and the passive optical chip after passing through the wavelength selection feedback module to form optical feedback, and another portion of the phase-compensated modulated laser beam is provided to the transceiver module through the output end-face modulated beam converter.

[0009] In an exemplary embodiment, the laser mode selected by the wavelength selection window of the wavelength selection feedback module is located at the center of the wavelength selection window and the center of the gain spectrum of the active optical chip.

[0010] In one exemplary embodiment, the wavelength feedback device in the wavelength selective feedback module includes at least one of the following: a distributed Bragg grating, a microring resonator.

[0011] In one exemplary embodiment, the gain region includes at least one of the following: a Fabry-Perot laser, a multimode reflective semiconductor optical amplifier, a distributed feedback laser, and a distributed Bragg reflector laser.

[0012] In one exemplary embodiment, the gain region is located before the phase region, or the phase region is located before the gain region.

[0013] In an exemplary embodiment, the waveguide extension direction of the active optical chip at the antireflection coating layer may be tilted at an angle of 0° relative to the normal direction of the end face surface, or between 5° and 8°.

[0014] In one exemplary embodiment, the passive optical chip is fabricated using one of the following materials: silicon, silicon nitride, silicon dioxide, or lithium niobate thin film.

[0015] According to another aspect of the embodiments of this application, a driving method for a frequency-modulated continuous wave lidar is provided. The frequency-modulated continuous wave lidar includes: a light source, a transceiver module, a detection module, and a data processing module. The light source includes an active optical chip and a passive optical chip. The active optical chip is provided with a gain region and a phase region. The method includes: applying a driving signal to the gain region to cause the gain region to generate a modulated laser beam based on the driving signal; applying a phase compensation signal to the phase region to cause the phase region to perform phase compensation on the modulated laser beam according to the phase compensation signal to increase the modulation bandwidth of the modulated laser beam; and providing the phase-compensated modulated laser beam to the passive optical chip.

[0016] This application describes a frequency-modulated continuous wave lidar (FMLD) that utilizes an active optical chip combining a gain region and a phase region to achieve high-speed, wide-bandwidth frequency modulation of a laser. The FMLD comprises a light source, a transceiver module, a detection module, and a data processing module. The light source includes an active optical chip and a passive optical chip. The active optical chip contains a gain region and a phase region. The gain region generates a modulated laser beam based on a received drive signal, while the phase region performs phase compensation on the modulated laser beam based on a received phase compensation signal, thereby increasing the modulation bandwidth. The active optical chip then provides the phase-compensated modulated laser beam to the passive optical chip, which outputs it to the transceiver module. This method utilizes a phase region within the laser resonant cavity to alter the light resonance. Phase modulation allows for single-mode output of the laser. Furthermore, controlling the effective length of the phase region controls the overall cavity length of the laser, achieving a larger modulation bandwidth. By placing the phase region within the semiconductor portion of the laser (light source), the effective length of the phase region can be rapidly altered by changing the injection current, thus enabling high-speed control of the overall cavity length. This allows the laser to achieve mode-skipping-free output over a large bandwidth while maintaining its narrow linewidth characteristics. This addresses the issues of low measurement accuracy and unstable performance in frequency-modulated continuous wave lidar, which suffers from the inability to achieve high-speed, large-bandwidth frequency modulation while maintaining a narrow linewidth. The goal is to improve measurement accuracy and enhance the stability of lidar performance. Attached Figure Description

[0017] Figure 1This is a structural block diagram of an optional frequency-modulated continuous wave lidar according to an embodiment of this application;

[0018] Figure 2 This is a structural block diagram of another optional frequency-modulated continuous wave lidar according to an embodiment of this application;

[0019] Figure 3 This is a schematic diagram showing the extension direction of an optional active optical chip waveguide structure according to an embodiment of this application;

[0020] Figure 4 This is a structural block diagram of another optional frequency-modulated continuous wave lidar according to an embodiment of this application;

[0021] Figure 5 This is a structural block diagram of an optional passive optical chip according to an embodiment of this application;

[0022] Figure 6 This is a schematic diagram of an optional frequency-modulated continuous wave lidar according to an embodiment of this application;

[0023] Figure 7 This is a structural block diagram of another optional frequency-modulated continuous wave lidar according to an embodiment of this application;

[0024] Figure 8 This is a schematic diagram of an optional connection method between a passive optical chip and an optical fiber module according to an embodiment of this application;

[0025] Figure 9 This is a schematic diagram of an optional phase region modulation bandwidth increase according to an embodiment of this application;

[0026] Figure 10 This is a schematic diagram of an optional passive optical chip according to an embodiment of this application;

[0027] Figure 11 This is a schematic diagram of another optional passive optical chip according to an embodiment of this application;

[0028] Figure 12 This is a schematic flowchart of an optional driving method for a frequency-modulated continuous wave lidar according to an embodiment of this application. Detailed Implementation

[0029] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0030] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0031] According to one aspect of the embodiments of this application, a frequency-modulated continuous wave lidar (i.e., FMCW lidar) is provided. The principle of FMCW lidar is that the carrier frequency (or phase) of the light source changes periodically over time. Coherent detection measures the modulation frequency difference between the echo signal and the transmitted signal of the detected object due to distance delay, as well as the Doppler frequency difference caused by relative velocity, thereby reflecting the distance and velocity information of the target object. This places high demands on the performance parameters and integration of the laser, such as emission power, linewidth, and frequency modulation capability. The frequency modulation capability of the laser is closely related to the performance parameters of the lidar. A wide tunable range (modulation bandwidth) determines the minimum distance at which the radar can distinguish targets in a single measurement, i.e., the radar's range resolution. The linewidth of the laser affects the radar's coherence length and measurement resolution; a narrower linewidth helps achieve a longer coherence length and higher measurement accuracy. Furthermore, the modulation rate of the laser also affects the radar's measurement rate, i.e., the frequency at which the radar refreshes the measurement results. A higher modulation rate can improve the measurement rate.

[0032] For the aforementioned lidar, commonly used semiconductor lasers, such as DFB (Distributed Feedback) and DBR (Distributed Bragg Reflector) lasers, typically have linewidths on the order of hundreds of kHz. This presents limitations for the higher measurement accuracy requirements of FMCW lidar. Furthermore, traditional semiconductor lasers may exhibit nonlinearity during frequency modulation (i.e., the modulation process may be nonlinear, leading to harmonics and phase noise in the modulated output signal), resulting in large measurement errors and low accuracy. Compared to commonly used semiconductor lasers, external cavity lasers offer advantages such as narrow linewidth and high frequency stability, which helps improve the detection accuracy of lidar. An external cavity laser integrates an internal laser emitting medium and one or more external optical elements (e.g., gratings) within the laser itself. It can use an external feedback mechanism (e.g., using mirrors) to partially reflect the light emitted from the laser medium back into the laser medium, forming one or more optical feedback paths. This external feedback mechanism enhances the laser's mode selection capability, resulting in more stable and monochromatic laser output.

[0033] However, there is a certain trade-off between the modulation bandwidth and linewidth of external cavity lasers. Narrow linewidth is beneficial for improving the measurement sensitivity and detection range of lidar, but excessively narrow linewidth limits the modulation bandwidth, thus affecting the range resolution and measurement range of the lidar. Furthermore, during operation, external cavity lasers experience a conflict between linewidth and modulation bandwidth, commonly known as longitudinal mode hopping. This occurs when the laser jumps from one longitudinal mode to another during tuning, leading to instability in output power, linewidth performance, and other characteristics, thus affecting the performance and stability of the lidar. Therefore, for external cavity lasers, achieving high-speed, wide-bandwidth frequency modulation while maintaining a narrow linewidth, to realize high-resolution, long-range detection FMCW lidar applications, is a problem that needs to be overcome.

[0034] To address this mode hopping, related technologies typically involve inserting tunable optical filters into the laser resonator to control the laser's single-mode output. However, this approach relies on mechanical movement to control the output mode selection, which is unsuitable for FMCW lidar with high integration requirements. Considering the need for integration, using low-loss waveguides or high-Q-value (i.e., quality factor, used to describe the energy storage capacity of a microring resonator; a high Q-value means the microring resonator can store light energy for a longer period with minimal loss and can have a narrow-band frequency response) microring resonators to increase the effective cavity length of the laser, thereby narrowing the linewidth and reducing mode hopping, has become a commonly used solution in recent years. However, this approach typically uses piezoelectric ceramics or thermal modulation of silicon-based waveguides for frequency modulation, which has limitations in modulation rate and affects the ranging performance of FMCW lidar. Furthermore, this method requires precise control of the waveguide or microring length, placing high demands on design and manufacturing precision.

[0035] It is evident that frequency-modulated continuous wave lidar in related technologies suffers from problems such as low measurement accuracy and unstable performance because the light source used cannot achieve high-speed, large-bandwidth frequency modulation of the laser while maintaining a narrow linewidth.

[0036] To at least partially address the aforementioned issues, this embodiment provides a frequency-modulated continuous wave (FMCW) lidar. A phase modulation region (i.e., a phase region) is added to the laser resonant cavity to alter the resonant phase of the light, thereby achieving single-mode output. Simultaneously, by controlling the effective length of the phase region, the overall cavity length of the laser can be controlled, achieving a larger modulation bandwidth. Secondly, since the modulation rate of a laser is limited by the physical constraints of the modulation method and materials, for narrow-linewidth external cavity lasers integrated from III-V semiconductor materials and silicon-based external cavities used in FMCW lidar, placing the phase region within the semiconductor portion of the external cavity laser allows for rapid response of charge carriers to current changes. Because the charge carriers in the semiconductor material can respond quickly to current changes, the effective length of the phase region can be rapidly altered by changing the injected current. This enables high-speed control of the overall cavity length of the laser, allowing for mode-hopping-free output over a large bandwidth while maintaining the narrow linewidth characteristic. Furthermore, applying a periodic current to the seed source (active optical chip) in the semiconductor portion to frequency modulate the laser achieves high-speed, high-bandwidth frequency modulation, suitable for the requirements of FMCW lidar.

[0037] Figure 1 This is a schematic diagram of an optional frequency-modulated continuous wave lidar according to an embodiment of this application, as shown below. Figure 1As shown, the aforementioned frequency-modulated continuous wave lidar may include: a light source 10, a transceiver module 20, a detection module 30, and a data processing module 40. The light source 10 generates a modulated laser beam to be emitted and transmits it to the transceiver module 20; it may be the aforementioned external cavity laser. The transceiver module 20 emits the modulated laser beam as a detection signal into the target space, receives the echo signal reflected back by the target object within the target space, and transmits the echo signal to the detection module 30 (a mixing detection module). The detection module 30 mixes the local oscillator signal of the detection signal with the echo signal to convert it into an electrical signal, and transmits the converted electrical signal to the data processing module 40. The data processing module 40 analyzes the frequency difference or phase difference of the converted electrical signal to obtain the required distance information, velocity information, etc. This embodiment does not limit the specific parameters.

[0038] In this embodiment, the light source 10 can be a narrow linewidth light source, which may include an active optical chip 11 and a passive optical chip 12. The active optical chip 11 and the passive optical chip 12 are docked and coupled. The docking and coupling technology may include, but is not limited to, coupling enhancement materials, optimized waveguide design, and adjustment of the optical characteristics of the coupling end face. Optionally, the light source 10 may also include an optical fiber module, which can be used to transmit the modulated laser beam between the passive optical chip and the transceiver module. The optical fiber module may be an output optical fiber or an optical fiber array. In addition, different modules of the frequency-modulated continuous wave lidar can also be connected by optical fibers to improve the efficiency and reliability of signal transmission.

[0039] Here, an active optical chip refers to a semiconductor chip containing active optical elements. When a bias current is applied to it, it can generate laser light. That is, an active optical chip can generate and modulate laser signals. A passive optical chip refers to a chip that does not contain active optical elements. It does not generate laser signals, but it may contain waveguides, optical fibers, or other structures. It can be used to guide laser signals to be transmitted between the active optical chip and other components. In addition, passive optical chips can also be used to process laser signals, such as filtering, splitting, combining, or isolating different laser signals.

[0040] The active optical chip 11 can integrate a gain region 111 and a phase region 112. The gain region 111 and the phase region 112 can each be provided with driving electrodes to connect to an external driving circuit (outside the active optical chip). Here, the gain region 111 refers to the region in the active optical chip 11 used to generate light waves, and the phase region 112 refers to the region in the active optical chip 11 used to regulate the phase of the light waves. Through the driving electrodes provided in the gain region 111 and the phase region 112 respectively, the external driving circuit can independently control the current input of both, improving the modulation flexibility.

[0041] Optionally, the gain region 111 can be used to generate a modulated laser beam based on a received driving signal. The gain region 111 may include a medium capable of generating optical gain through stimulated emission, thereby being excited by the received driving signal to generate a laser beam. By modulating the generated laser beam, a modulated laser beam is obtained. The phase region 112 can be used to perform phase compensation on the modulated laser beam generated by the gain region 111 based on a received phase compensation signal, so as to increase the modulation bandwidth of the modulated laser beam. Here, the phase compensation of the modulated laser beam can be based on the electro-optic effect. The electro-optic effect refers to the phenomenon that the refractive index of a material changes with the applied electric field. Through the electro-optic effect, based on the phase compensation signal applied to the phase region 112, the electric field can be changed, thereby changing the phase of the modulated laser beam in the phase region 112.

[0042] It should be noted that during high-speed, wide-bandwidth frequency modulation, the current in gain region 111 (controlled by the received drive signal) can change periodically, causing modulation of the laser frequency. Here, phase region 112 can synchronously adjust the applied injection current (controlled by the received phase compensation signal) in accordance with the current change in gain region 111, changing the phase of the light wave in phase region 112 to compensate for the phase difference caused by frequency changes, ensuring the continuous and stable laser mode (laser wavelength) and avoiding mode jumps. In addition, the dynamic phase compensation of phase region 112 also helps to maintain the narrow linewidth of the laser output (i.e., light source 10). In a laser, a narrow linewidth means a higher coherence length and more accurate measurement capability. By narrowing the laser linewidth, the linewidth of the output laser can be kept stable even under wide-bandwidth modulation.

[0043] It should be noted that the phase region is a phase modulation region added to the semiconductor seed source region of the external cavity laser used in FMCW lidar. By controlling the injection current in the phase region to change the effective length of the phase region, the overall cavity length of the external cavity laser can be adjusted to achieve a larger modulation bandwidth. Combined with the modulation method of the seed source injection current, high-speed frequency modulation is achieved.

[0044] Optionally, in this embodiment, as Figure 2As shown, the transceiver module 20 may include a laser emitting module 21 and a return light receiving module 22. The laser emitting module 21 receives the provided modulated laser beam and emits the modulated laser beam provided by the passive optical chip 12 as a detection signal into the space under test. The return light receiving module 22 receives the echo signal reflected back by the target object in the space under test (i.e., receives the reflected light wave). Here, the laser emitting module 21 can be used to convert the laser signal generated by the light source 10 into a form suitable for propagation and guide it to the space under test. For example, the laser signal can be focused into a laser beam and irradiated onto the target object using an optical system. The return light receiving module 22 may include an optical receiving device, which can be used to receive the echo signal reflected back by the target object in the space under test and send the echo signal to the detection module 30 for further signal processing.

[0045] According to the embodiments provided in this application, a frequency-modulated continuous wave lidar includes: a light source, a transceiver module, a detection module, and a data processing module. The light source includes an active optical chip and a passive optical chip. The active optical chip has a gain region and a phase region. The gain region is used to generate a modulated laser beam based on a received driving signal, and the phase region is used to perform phase compensation on the modulated laser beam based on a received phase compensation signal to increase the modulation bandwidth of the modulated laser beam. The active optical chip provides the phase-compensated modulated laser beam to the passive optical chip, which then outputs it to the transceiver module. This solves the problem of low measurement accuracy and unstable performance in related technologies' frequency-modulated continuous wave lidars, which cannot achieve high-speed, large-bandwidth frequency modulation of the laser while maintaining a narrow linewidth. This improves measurement accuracy and enhances the stability of the lidar performance.

[0046] In one exemplary embodiment, the gain region may include a semiconductor laser, which may include at least one of the following: a Fabry-Perot laser, a multimode reflective semiconductor optical amplifier, a distributed feedback laser, and a distributed Bragg reflector laser. For different application scenarios, different gain region components can be selected by comprehensively considering factors such as the laser's linewidth, modulation bandwidth, output power, cost, and fabrication difficulty. For example, for applications requiring extremely high frequency stability and resolution, such as frequency-modulated continuous-wave lidar systems for autonomous vehicles, a distributed feedback laser or a distributed Bragg reflector laser can be selected because they can provide narrow linewidth and high frequency stability laser output, while achieving high-speed, wide-bandwidth frequency modulation through dynamic control of the phase region. For cost-sensitive scenarios or scenarios requiring high power output, a multimode reflective semiconductor optical amplifier or a Fabry-Perot laser can be selected.

[0047] This embodiment demonstrates how selecting appropriate gain region components based on the characteristics of different semiconductor lasers and usage requirements can improve the performance of a frequency-modulated continuous wave lidar system.

[0048] In one exemplary embodiment, the positions of gain region 111 and phase region 112 can be interchanged. For different application requirements, the phase positions of gain region 111 and phase region 112 can be different; that is, gain region 111 can be located before phase region 112, or phase region 112 can be located before gain region 111. When gain region 111 is located before phase region 112, the light wave is first amplified in gain region 111 and then enters phase region 112 for phase adjustment or cavity length control. This is suitable for applications requiring high output power because the light wave has already acquired sufficient gain before entering phase region 112, and even if phase region 112 causes significant loss to the light wave, the laser can still maintain high output power. When phase region 112 is located before gain region 111, the phase of the light wave can be pre-modulated before amplification through gain region 111. This arrangement facilitates frequency modulation before signal amplification, enabling finer frequency control.

[0049] By configuring the relative positions of the gain region and phase region according to usage requirements, the flexibility and stability of the frequency modulated continuous wave lidar system can be improved through this embodiment.

[0050] In one exemplary embodiment, one end of the active optical chip 11 and the passive optical chip 12 is coated with an antireflection film, while the other end may be coated with a high-reflection film or left uncoated. In the scenario where one end of the active optical chip 11 is coated with an antireflection film and the other end is uncoated, the modulated laser beam can also be output from the uncoated end. Both ends of the passive optical chip 12 are coated with antireflection films. Optionally, the waveguide extension direction of the active optical chip's waveguide structure at the antireflection film layer can be tilted at an angle of 0° relative to the normal direction of the end face surface, or between 5° and 8°.

[0051] As an optional implementation, the waveguide extension direction of the active optical chip 11 at the antireflection coating layer can be tilted at an angle of 0° relative to the normal direction of the end face surface. This can simplify the manufacturing process, improve production efficiency, and reduce beam divergence and coupling loss caused by changes in waveguide direction.

[0052] As another alternative implementation, considering that even with an antireflection coating, light of certain wavelengths may still be reflected at the end face, in order to reduce light reflection at the end face, a tilted waveguide design can be implemented. That is, the tilt angle of the waveguide extension direction of the active optical chip's waveguide structure at the antireflection coating layer relative to the normal direction of the end face surface can be greater than 0°.

[0053] Here, for the tilted waveguide design, the reflectivity reduction effect needs to be considered, while the manufacturing difficulty of the lidar also needs to be taken into account. For too small a tilt angle, the reflectivity reduction effect is not significant, and too small an angle may also increase the complexity of the manufacturing process, for example, requiring higher alignment accuracy. On the other hand, for too large a tilt angle, the reflectivity reduction effect may be better; however, it may exceed the receiving angle range of the passive optical chip, leading to a decrease in coupling efficiency. To achieve a balance between reflectivity reduction effect and manufacturing difficulty and cost, a suitable tilt angle can be determined experimentally, for example, it can be located between 5° and 8°.

[0054] For example, such as Figure 3 As shown on the left, in the active optical chip's waveguide structure, the waveguide extension direction at the antireflection coating layer can be tilted at an angle of 0° relative to the normal direction of the end face surface, or, as shown... Figure 3 As shown on the right, the waveguide extension direction of the active optical chip at the antireflection coating layer can be tilted at an angle between 5° and 8° relative to the normal direction of the end face surface.

[0055] In this embodiment, by designing the tilt angle of the waveguide extension direction at the antireflection coating layer relative to the normal direction of the end face surface in the optical waveguide structure of the active optical chip, the overall performance and stability of the system can be improved.

[0056] In one exemplary embodiment, optical chips made of different materials can be selected as passive optical chips to meet different performance requirements. The passive optical chip is fabricated using one of the following materials: silicon, silicon nitride, silicon dioxide, or lithium niobate thin film. In addition to the above materials, other materials can also be selected as the fabrication materials for the passive optical chip in the aforementioned frequency-modulated continuous wave lidar.

[0057] Here, the passive optical chip fabricated using silicon can be a silicon waveguide-based optical chip. Silicon waveguide-based optical chips can utilize the high refractive index and excellent waveguide properties of silicon to guide light waves propagation within the chip, exhibiting good transparency and low absorption loss. However, silicon-based waveguides have significant bending losses, which may require additional design considerations for applications demanding high-precision waveguide bending and bifurcation.

[0058] Passive optical chips fabricated using silicon nitride can be based on silicon nitride waveguides. Silicon nitride, a wide-bandgap material, provides excellent transparency for optical signals ranging from the visible to the infrared spectrum. Silicon nitride waveguides exhibit low bending loss and good optical field confinement, making them suitable for high-precision wavelength-selective feedback devices. Furthermore, they allow for seamless integration with silicon waveguides.

[0059] Passive optical chips fabricated using silicon dioxide can be based on silicon dioxide waveguides. Silicon dioxide waveguides possess excellent optical performance and low loss rates. The manufacturing process for silicon dioxide waveguide-based optical chips is mature and relatively low-cost. Furthermore, they exhibit good mechanical strength and thermal stability, making them suitable for constructing long-distance, low-loss optical transmission lines. However, silicon dioxide waveguides have relatively low integration density. For FMCW lidar systems requiring high integration, it may be necessary to combine them with chips made from other materials.

[0060] Here, the passive optical chip fabricated using lithium niobate thin film can be an optical chip based on a lithium niobate thin film waveguide. Lithium niobate is a nonlinear optical material exhibiting electro-optic and photoelastic effects, and can be used to fabricate optical modulators and optical switches. Optical chips based on lithium niobate thin film waveguides have unique advantages in modulation and frequency selection, enabling high-speed and efficient optical modulation, suitable for optical communication and optical signal processing. They can achieve low-loss, high-speed phase modulation, suitable for precise control of laser output frequency in FMCW lidar systems. Furthermore, lithium niobate material also has good temperature stability, maintaining high-precision optical wave modulation over a wide temperature range.

[0061] In this embodiment, various factors such as integration level, cost, optical loss, temperature stability, and compatibility with the system's operating wavelength can be comprehensively considered to configure a suitable passive optical chip for the aforementioned frequency-modulated continuous wave lidar, thereby achieving narrow linewidth output and large bandwidth modulation of the laser and improving the overall performance of the lidar system.

[0062] This embodiment demonstrates how selecting suitable materials to fabricate passive optical chips based on usage requirements can improve system stability and overall performance.

[0063] In one exemplary embodiment, such as Figure 4 As shown, the frequency-modulated continuous wave lidar also includes a drive circuit 50. The drive circuit 50, connected to the gain region 111, generates a drive signal and provides it to the gain region 111. The drive signal is a superposition of a DC bias signal and a modulation signal. Here, the DC bias signal provides a bias current to the gain region 111, while the modulation signal modulates the laser beam generated by the gain region 111, thereby generating the aforementioned modulated laser light. Correspondingly, the gain region 111 is also used to generate a laser beam based on the DC bias signal and to modulate the laser beam based on the modulation signal to form a modulated laser beam. The drive circuit 50, connected to the phase region 112, generates a phase compensation signal and provides it to the phase region 112.

[0064] Optionally, the driving circuit 50 may include a gain region driving circuit and a phase region driving circuit. When the gain region driving circuit applies an operating current to the gain region 111, the gain region generates a modulated laser beam. Simultaneously, the phase region driving circuit applies a current to the phase region 112 for phase compensation. The phase-compensated modulated laser beam is then transmitted from the light source chip 11 to the passive optical chip 12. Compared to using the same driving circuit to drive both the gain region and the phase region, using different driving circuits to drive the gain region and the phase region separately improves the convenience of circuit driving and reduces signal interference.

[0065] In this embodiment, the driving circuit provides a driving signal that superimposes a DC bias signal and a modulation signal to the gain region, and provides a phase compensation signal to the phase region, which can improve the convenience of laser beam generation.

[0066] In one exemplary embodiment, such as Figure 5 As shown, the passive optical chip 12 includes an input end-face modulated beam converter 121, a wavelength selection feedback module 122, and an output end-face modulated beam converter 123. The phase-compensated modulated laser beam is transmitted to the passive optical chip 12 through the input end-face modulated beam converter 121. Part of the phase-compensated modulated laser beam passes through the wavelength selection feedback module 122 and enters the resonant cavity formed by the active optical chip 11 and the passive optical chip 12 to form optical feedback. The other part of the phase-compensated modulated laser beam is provided to the transceiver module through the output end-face modulated beam converter.

[0067] The input end-face mode converter 121 can be used to appropriately convert the mode characteristics of light waves (e.g., a modulated laser beam after phase compensation) during transmission from the active optical chip 11 to the passive optical chip 12, ensuring that the light waves can be efficiently coupled into other components. Here, mode refers to the light field distribution when the light wave is in contact with the surface of a material or device, and is usually used to describe the mode and size characteristics of the light wave. The wavelength selection feedback module 122 can be used to selectively feed back light waves of a portion of the wavelength. The output end-face mode converter 123 can be located at the output end of the passive optical chip, and can convert the light waves output by the laser into a mode suitable for transmission to the fiber optic module or other components of the aforementioned lidar system. The aforementioned mode converter may include optical elements, such as lenses, fiber couplers, etc., which are not limited in this embodiment.

[0068] The waveguide extension direction of the input end-face mode converter can be aligned with the waveguide extension direction of the end of the active optical chip coated with an antireflection film. The waveguide is the channel through which light waves propagate within the chip; its extension direction determines the propagation path. Light waves generated by the active chip can be coupled into the waveguide of the passive optical chip via the input end-face mode converter to continue their optical path in the laser resonant cavity. By aligning the waveguide extension direction of the input end-face mode converter with that of the waveguide at the end of the active chip coated with an antireflection film, good mode matching can be maintained during propagation. That is, the propagation direction of the light wave does not need to change significantly during propagation, thereby reducing beam divergence and coupling losses caused by mode mismatch, ensuring efficient transmission of light waves between the two chips.

[0069] Optionally, the wavelength selection feedback module 122 may include a wavelength selection feedback device and an optical transmission waveguide. The wavelength selection feedback device can be used to select a specific wavelength of light from the laser resonant cavity. When the wavelength of the light wave matches the resonance condition constructed internally by the wavelength selection feedback device, the light wave is significantly amplified and reflected back to the laser resonant cavity, while light waves that do not match the resonance condition are attenuated. The selected wavelength range can be adjusted by adjusting or selecting the parameters of the wavelength selection feedback device. The optical transmission waveguide can be used to guide the light wave from the active optical chip 11 to the wavelength selection feedback device, or it can be used to redirect part of the reflected light wave back to the active optical chip 11, forming a loop optical path, i.e., the laser resonant cavity. The optical transmission waveguide can be a straight waveguide, a phase shifter, a coupler, or other types of waveguide structures; this embodiment is not limited to any of these.

[0070] In this embodiment, light waves (e.g., modulated laser beams after phase compensation) can be transmitted to the passive optical chip 12 via the input end-face mode converter 121. After passing through the wavelength selection feedback module 122, a portion of the light waves enters the resonant cavity composed of the active optical chip 11 and the passive optical chip 12 to form optical feedback. Here, the resonant cavity composed of the active optical chip 11 and the passive optical chip 12 can be a laser resonant cavity formed between the gain region 111 of the active optical chip 11 and the wavelength selection feedback module 122 of the passive optical chip 12. Within the laser resonant cavity, only light waves that meet specific conditions can exist stably within the cavity; these conditions are called resonance conditions. Within the resonant cavity, light waves reflect back and forth multiple times along the cavity axis, forming standing waves. These standing waves can form specific modes, i.e., longitudinal modes. These longitudinal modes are equally spaced, and each longitudinal mode represents a frequency (i.e., the frequency at which the light wave in the cavity satisfies the resonance conditions; here, the resonance conditions refer to the phase of the light wave traveling back and forth once within the cavity being an integer multiple of 2π), such as... Figure 6 As shown in 61.

[0071] The wavelength selection feedback module 122 can provide a wavelength selection window. The longitudinal modes of the light wave selected by this window are dominant in mode competition and are resonantly enhanced in the resonant cavity, forming laser output. That is, through reflection and selection mechanisms, the longitudinal modes matching the window frequency within the cavity can be enhanced, while other longitudinal modes are weakened, ensuring that the output laser frequency is stable within a narrow range, i.e., narrow linewidth output. Figure 6 As shown in 62, longitudinal modes within the wavelength selection window are enhanced by reflection, while other longitudinal modes are weakened by loss. Simultaneously, gain region 111 itself also possesses a gain spectral line, as shown... Figure 6 As shown in 63, longitudinal modes within the gain spectral line are enhanced, while longitudinal modes outside the spectral line are lost. The longitudinal modes selected by the wavelength selection window 62 and the gain spectral line 63 are dominant in mode competition, and after resonance enhancement, they form a stable single-mode laser output.

[0072] Optionally, another portion of the phase-compensated modulated laser beam is provided to the fiber optic module via the output end face mode converter 123. A portion of the light wave is connected to the laser emitting module for distance detection, while the other portion of the light wave, together with the reflected light wave received by the return light receiving module, is input to the detection module for beat frequency and converted into an electrical signal. The corresponding distance and velocity quantities are then calculated by the data processing module.

[0073] For example, such as Figure 7 As shown, the lidar includes a light source 10 (laser, e.g., an external cavity laser), a transceiver module 20, a detection module 30, a data processing module 40, and a driving circuit 50. The light source 10 includes an active optical chip 11, a passive optical chip 12, and an optical fiber module 13. The active optical chip 11 includes a gain region 111 and a phase region 112. The passive optical chip 12 includes an input end-face mode converter 121, a wavelength selection feedback module 122, and an output end-face mode converter 123. The wavelength selection feedback module 122 includes an optical transmission waveguide 1221 and a wavelength selection feedback device 1222. The transceiver module 20 includes a laser emission module 21 and a return light receiving module 22. The driving circuit 50 includes a gain region driving circuit 51 and a phase region driving circuit 52.

[0074] During ranging, a high-speed periodic modulation current can be applied to the gain region via a driving circuit (e.g., gain region driving circuit 51). The effective refractive index of the gain region changes periodically, which in turn periodically alters the overall cavity length of the laser, causing the output laser frequency to change periodically at high speed. Simultaneously, a corresponding current is applied to the phase region via a driving circuit (e.g., phase region driving circuit 52) ​​for phase compensation, ensuring the laser always achieves maximum modulation bandwidth during ranging, meeting the high-speed, high-bandwidth modulation requirements of frequency-modulated continuous wave lidar. The output laser can be emitted as a frequency-modulated light wave by the laser emission module and received by the light wave reflected from the object by the return light receiving module. These, along with the laser output light wave, are input to the detection module and converted into electrical signals. The data processing module then processes the data to obtain the corresponding distance and velocity information. This modulation scheme meets the high-speed, high-bandwidth frequency modulation requirements of frequency-modulated continuous wave lidar. Furthermore, the wavelength selection feedback module increases the effective cavity length of the laser and reduces its linewidth, achieving narrow-linewidth laser output and improving the detection accuracy of the frequency-modulated continuous wave lidar.

[0075] For different application scenarios, considering factors such as the laser output beam mode, power requirements, and the overall consideration of coupling efficiency and cost-effectiveness, different output end-face modulus converter connection schemes can be selected. Optionally, the output end-face modulus converter 123 can be directly connected to the fiber optic module 13, or the output end-face modulus converter 123 can be connected to the fiber optic module 13 through a lens; or the output end-face modulus converter 123 can be connected to a gain device. Direct connection of the output end-face modulus converter to the fiber optic module is suitable for situations where the laser output beam and the fiber optic module are well matched or where low coupling loss is required, thereby reducing the use of additional optical components and lowering system costs. Connection of the output end-face modulus converter to the fiber optic module through a lens is suitable for situations where the laser output beam and the fiber optic module are mismatched. Beam shaping and focusing through the lens can significantly improve the module coupling efficiency of the beam from the laser to the fiber. Here, the lens can expand or contract the beam to match its mode with the fiber mode field, reducing losses during coupling. In addition, the use of the lens can also improve the mechanical stability and alignment accuracy of the system. Output mode converters connected to gain devices (e.g., fiber amplifiers, semiconductor amplifiers, etc.) can be used when the output power of the laser may not be sufficient to meet the system requirements. They can amplify the power of the light wave while maintaining the narrow linewidth characteristics of the laser, thus meeting the system's demand for a high-power laser source.

[0076] For example, such as Figure 8 As shown in (a), the output surface mode converter 123 of the passive optical chip 12 can be directly connected to the fiber optic module 13; or, as shown in (a), Figure 8As shown in (b), the output end-face mode converter 123 is connected to the fiber optic module 13 via lens 141; or, as shown in (b), Figure 8 As shown in (c), the output end face mode converter 123 connects to the gain device 142 to realize high-power laser output.

[0077] In this embodiment, an active optical chip combining the gain region and the phase region is used to enable the laser to achieve high-speed, wide-bandwidth frequency modulation, while a passive optical chip with a wavelength-selective feedback module is used to significantly reduce the laser linewidth, thus achieving a narrow-linewidth light source and high-speed, wide-bandwidth frequency modulation that meet the requirements of frequency-modulated continuous wave lidar.

[0078] In one exemplary embodiment, the laser mode selected by the wavelength selection window of the wavelength selection feedback module is located at the center of the wavelength selection window and the center of the gain spectrum of the active optical chip.

[0079] Here, the laser mode refers to the specific vibration state of the light wave within the laser resonant cavity. It determines the frequency, intensity distribution, and spatial distribution pattern of the laser output. The laser mode can include longitudinal modes; that is, in this embodiment, the laser mode selected by the wavelength selection window can correspond to the aforementioned longitudinal modes. Similar to the previous embodiments, the wavelength selection feedback module 122 can provide a wavelength selection window to selectively enhance or weaken the passing light wave, thereby enabling the laser mode located at the center of the gain spectrum within the wavelength selection window to obtain maximum gain.

[0080] Correspondingly, the gain region of an active optical chip can have a gain spectral line, which represents the wavelength range that the gain medium can effectively amplify. At certain wavelengths, the gain medium can amplify the light more effectively. The peak value on the gain spectral line can correspond to the specific wavelength range that the gain medium can amplify. In other words, when the laser mode is at the center of the gain spectral line, the light wave can obtain the maximum gain and the highest output power.

[0081] Frequency-modulated continuous-wave lidar requires the laser output frequency to change periodically and linearly to meet ranging requirements. The laser output frequency can be periodically fine-tuned by applying a periodically varying drive current to the gain region via the drive electrodes. In this case, the laser's longitudinal modes and the gain lines in the gain region will shift in frequency with the magnitude of the drive current. If the frequency shift exceeds the width of the wavelength selection window, the laser mode originally in the center of the window may no longer be selected, while other longitudinal modes may gain more gain. When the gain of other longitudinal modes exceeds the gain of the original longitudinal mode, the laser output will jump from one longitudinal mode to another, such as... Figure 9As shown on the left, the laser's output frequency jumps at this point, causing instability in the laser's performance and affecting its ranging capabilities. Within the mode-hopping-free range, the range of laser output frequency variation with current is called the modulation bandwidth. A larger modulation bandwidth is beneficial for improving the ranging accuracy of the lidar.

[0082] Similar to the previous embodiments, in order to obtain a larger modulation bandwidth, after the light wave is generated in the gain region, a specific current can be applied to the phase region through the driving electrode to change the overall cavity length, so that the laser mode is always located at the center of the gain spectrum of the wavelength selection feedback module, and at the center of the gain spectrum of the gain region, such as... Figure 9 As shown on the right, the laser output power is at its highest at this time, and it also has the largest modulation bandwidth.

[0083] In this embodiment, by precisely positioning the laser mode at the center of the wavelength selection window and the gain spectrum of the active optical chip, mode jumps can be avoided when the laser is subjected to high-speed, wide-bandwidth modulation, thus maintaining the continuity and linearity of the laser frequency modulation.

[0084] In one exemplary embodiment, different parts of the wavelength selective feedback module 122 can be configured as needed. Depending on different application requirements, different wavelength feedback devices can be selected, including at least one of the following: distributed Bragg gratings (DBRs) and microring resonators. Optionally, the wavelength selective feedback module can be designed to have multiple DBRs, multiple microring resonators, or at least one DBR and at least one microring resonator, selecting different wavelength feedback devices through a switching mechanism to achieve more flexible wavelength selection and modulation capabilities.

[0085] A distributed Bragg grating is a periodic optical element composed of alternating layers of materials with different refractive indices. The refractive index differences between these layers cause light waves of specific wavelengths to be reflected, while light waves of other wavelengths are transmitted. Its working principle is based on Bragg reflection, that is, when light waves propagate in a multilayer medium, if the Bragg condition is met (i.e., the difference in the reflection path of the light wave in the medium is an integer multiple of the wavelength), strong reflection will occur. By using a distributed Bragg grating, light of specific wavelengths can be effectively reflected, thereby improving the wavelength selectivity and output power of the laser.

[0086] A microring resonator is a ring structure composed of tiny optical waveguides, typically on the order of micrometers. When light propagates within the microring, a strong resonance occurs if the resonance condition is met (i.e., the path length of the light wave within the ring is an integer multiple of its wavelength). This resonance, generated through the ring structure, produces a high Q-value, enhancing light of a specific wavelength while suppressing other wavelengths. Optionally, this selectivity can be adjusted by the size and refractive index of the microring. Microring resonators allow for the precise selection and filtering of specific wavelengths. Furthermore, microring resonators can be used in applications such as optical switches, optical modulators, and optical sensors.

[0087] Optionally, the optical transmission waveguide in the wavelength selection feedback module 122 may include at least one of the following: a straight waveguide; a first phase shifter; a Y-branch; a directional coupler; a multimode interference coupler; a Sagnac ring; or a Sagnac ring with a second phase shifter.

[0088] A straight waveguide is a type of optical wave transmission structure that transmits light through direct beams, reducing bending losses and making it suitable for simple and low-loss optical path designs.

[0089] A phase shifter is a device that can change the phase of an optical wave. In a waveguide, a phase shifter can be used to modulate the phase of an optical signal, thereby achieving precise control of the optical wave phase. The first phase shifter can be one of the following: a thermally modulated phase shifter based on a silicon waveguide, a thermally modulated phase shifter based on a silicon nitride waveguide, a positive and negative electro-optic phase shifter based on a silicon waveguide, a positive intrinsic negative electro-optic phase shifter based on a silicon waveguide, a thermally modulated phase shifter based on a lithium niobate thin-film waveguide, or an electro-optic phase shifter based on a lithium niobate thin-film waveguide.

[0090] Y-branching is an optical path splitting and combining technique that can split a light wave into two paths or combine two light waves into one. For wavelength selective feedback modules, Y-branching can be used to split and mix light waves. For example, Y-branching can be used to split the light wave output from a laser into two paths, one of which is reflected back to the resonant cavity, while the other is detected or transmitted through subsequent modules.

[0091] A directional coupler is a device that can proportionally distribute light waves to two or more output ports, suitable for precise distribution and mixing of light waves. In this embodiment, the directional coupler can be used to achieve effective distribution and feedback of light waves by adjusting the coupling length and gap, thereby optimizing the output performance of the laser.

[0092] Multimode interference couplers can be used to utilize the interference effect of light in multimode waveguides to achieve the splitting and combining of light waves and wavelength selection. For example, by precisely controlling the size and shape of the waveguide, a multimode interference coupler can be used to achieve efficient selection and feedback of light of a specific wavelength, thereby improving the resolution and stability of the lidar system.

[0093] A Sagnac ring is an optical path structure that utilizes the Sagnac effect to achieve bidirectional optical signal interference and wavelength selection. In this embodiment, the Sagnac ring can be used as a wavelength-selective feedback structure. This structure improves the modulation performance and stability of the laser by transmitting the optical signal bidirectionally within the ring and using the interference effect for wavelength selection.

[0094] Optionally, a phase shifter can be added to the Sagnac ring to achieve precise adjustment of the broadcast phase within the ring, further optimizing wavelength selection and feedback effects. That is, a Sagnac ring with a second phase shifter can be configured. The second phase shifter can be one of the following: a thermally modulated phase shifter based on a silicon waveguide, a thermally modulated phase shifter based on a silicon nitride waveguide, a positive and negative electro-optic phase shifter based on a silicon waveguide, a positive intrinsic negative electro-optic phase shifter based on a silicon waveguide, a thermally modulated phase shifter based on a lithium niobate thin-film waveguide, or an electro-optic phase shifter based on a lithium niobate thin-film waveguide.

[0095] For example, such as Figure 10 As shown, Figure 10 This is one option for the passive optical chip 12 and the fiber optic module 13. The wavelength selection feedback device 1222 uses a distributed Bragg grating 1222A. The distributed Bragg grating 1222A can be designed to control the reflectivity and transmittance of the light wave, as well as the corresponding grating bandwidth. The optical transmission waveguide 1221 can be adopted as follows: Figure 10 The straight waveguide 1221A shown in (a) is... Figure 10 Phase shifter 1221B shown in (b) Figure 10 The directional coupler 1221C shown in (c) is... Figure 10 The multimode interference coupler 1221D, etc., is shown in (d) in the figure.

[0096] The wavelength selection window of the distributed Bragg grating 1222A is as follows: Figure 10 As shown in (e), a portion of the light wave located within the wavelength selection window is reflected back, forming a resonant cavity with the active optical chip 11. The longitudinal mode selected by the distributed Bragg grating is dominant in mode competition, ultimately forming a single-mode laser output. The bandwidth of the wavelength selection window of the distributed Bragg grating can be expressed as:

[0097]

[0098] Where κ=πΔn / λ0 is the grating coupling coefficient, and λ0=2n eff ×Λ0 is the Bragg wavelength, n eff The effective refractive index is Δn, where Δn is the grating refractive index difference, and n g The effective refractive index is L, and the grating length is L. The bandwidth of the gain spectrum determines the modulation bandwidth of the laser to a certain extent.

[0099] For example, such as Figure 11 As shown, Figure 11 Another option for the passive optical chip 12 and fiber optic module 13 is to use a microring resonator 1222B as the wavelength selection feedback device 1222. The reflectivity of the microring resonator and the bandwidth of the wavelength selection window can be adjusted by changing the coupling coefficient between the straight waveguide and the ring resonator. The optical transmission waveguide 1221 can be used as follows: Figure 11 The straight waveguide 1221A shown in (a) is as follows: Figure 11 Phase shifter 1221B shown in (b) is as follows: Figure 11 The directional coupler 1221C shown in (c) is as follows: Figure 11 The multimode interference coupler 1221D shown in (d) is as follows: Figure 11 The Sagnac mirror 1221E shown in (e) is as follows: Figure 11 (f) The Sagnac reflector 1221F with a phase shifter, etc. When the optical transmission waveguide is a straight waveguide or a phase shifter, the microring resonator reflects part of the light through Rayleigh scattering, forming a resonant cavity with the active optical chip 11. The wavelength selection window of the microring resonator selects the corresponding longitudinal mode to form a single-mode laser output. When the optical transmission waveguide is a directional coupler, a multimode interference coupler, or a Sagnac reflector, the light is transmitted through the microring resonator and reflected by the directional coupler, multimode interference coupler, or Sagnac reflector to form a resonant cavity with the active optical chip. The wavelength selection window of the microring resonator selects the corresponding longitudinal mode to form a single-mode laser output.

[0100] In this embodiment, by configuring wavelength feedback devices and optical transmission waveguide structures in the wavelength selection feedback module, precise wavelength selection and feedback control of the laser output light can be achieved, thereby improving the overall resolution and stability of the system.

[0101] In an exemplary embodiment, the waveguide extension direction of the input end face mode converter is consistent with the waveguide extension direction of one end of the active optical chip coated with antireflection film.

[0102] In this embodiment, the waveguide is the channel through which light waves are transmitted inside the chip. Its extension direction determines the transmission path of the light waves. The light waves generated by the active optical chip can be coupled into the waveguide of the passive optical chip through the input end face mode converter to continue their optical path in the laser resonant cavity.

[0103] Optionally, the waveguide extension direction of the input end face mode converter can be consistent with the waveguide extension direction of one end of the active optical chip coated with antireflection film. Thus, the light wave can maintain good mode matching during transmission. That is, the propagation direction of the light wave does not need to change significantly during propagation, thereby reducing beam divergence and coupling loss caused by mode mismatch, and ensuring efficient transmission of light waves between the two chips.

[0104] By setting a consistent reporting extension direction, the efficiency and stability of optical wave transmission can be improved and energy loss reduced through this embodiment.

[0105] It should be noted that the above modules can be implemented by software or hardware. For the latter, they can be implemented in the following ways, but are not limited to: all the above modules are located in the same processor; or, the above modules are located in different processors in any combination.

[0106] According to another aspect of the embodiments of this application, a driving method for a frequency-modulated continuous wave lidar is provided. Optionally, in this embodiment, the driving method for the frequency-modulated continuous wave lidar described above can be applied to any of the frequency-modulated continuous wave lidars in the foregoing embodiments, as has been described before, and will not be repeated here.

[0107] Taking the frequency-modulated continuous wave lidar driving method in this embodiment as an example, the frequency-modulated continuous wave lidar includes: a light source, a transceiver module, a detection module and a data processing module. The light source includes an active optical chip and a passive optical chip. The active optical chip is provided with a gain region and a phase region. Figure 12 This is a schematic flowchart of an optional driving method for a frequency-modulated continuous wave lidar according to an embodiment of this application, as shown below. Figure 12 As shown, the process of this method may include the following steps:

[0108] Step S1202: Apply a driving signal to the gain region so that the gain region generates a modulated laser beam based on the driving signal;

[0109] Step S1204: Apply a phase compensation signal to the phase region so that the phase region performs phase compensation on the modulated laser beam according to the phase compensation signal, thereby increasing the modulation bandwidth of the modulated laser beam.

[0110] Step S1206: The phase-compensated modulated laser beam is provided to the passive optical chip.

[0111] In this embodiment, the same or similar methods as in the previous embodiments can be used to apply a driving signal to the gain region, a phase compensation signal to the phase region, and a modulated laser beam after phase compensation to the passive optical chip. As has been described before, it will not be repeated here.

[0112] The embodiments provided in this application apply a driving signal to the gain region so that the gain region generates a modulated laser beam based on the driving signal; a phase compensation signal is applied to the phase region so that the phase region performs phase compensation on the modulated laser beam according to the phase compensation signal, thereby increasing the modulation bandwidth of the modulated laser beam; the modulated laser beam after phase compensation is provided to the passive optical chip, which solves the problem of low measurement accuracy and unstable performance of frequency-modulated continuous wave lidar in related technologies due to the inability to achieve high-speed and large-bandwidth frequency modulation of the laser while maintaining a narrow linewidth, thereby improving the measurement accuracy and thus improving the stability of lidar performance.

[0113] In one exemplary embodiment, the frequency-modulated continuous wave lidar further includes a driving circuit. Applying a driving signal to the gain region includes: generating a driving signal through the driving circuit and providing it to the gain region, wherein the driving signal is a superposition signal of a DC bias signal and a modulation signal. Applying a phase compensation signal to the phase region includes: generating a phase compensation signal through the driving circuit and providing it to the phase region. The method further includes: generating a laser beam through the gain region according to the DC bias signal, and modulating the laser beam according to the modulation signal to form a modulated laser beam.

[0114] In one exemplary embodiment, the passive optical chip includes: an input end-face modulated beam converter, a wavelength selection feedback module, and an output end-face modulated beam converter. After providing the phase-compensated modulated laser beam to the passive optical chip, the method further includes: transmitting the phase-compensated modulated laser beam to the passive optical chip via the input end-face modulated beam converter, wherein a portion of the phase-compensated modulated laser beam passes through the wavelength selection feedback module and enters a resonant cavity composed of an active optical chip and a passive optical chip to form optical feedback, and another portion of the phase-compensated modulated laser beam passes through the output end-face modulated beam converter and is provided to a transceiver module.

[0115] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to this application. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to this application.

[0116] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods according to the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM (Read-Only Memory) / RAM (Random Access Memory), magnetic disk, optical disk), and includes several instructions to cause a terminal device (which may be a mobile phone, computer, server, or network device, etc.) to execute the methods described in the various embodiments of this application.

[0117] Obviously, those skilled in the art should understand that the modules or steps of this application described above can be implemented using general-purpose computing devices. They can be centralized on a single computing device or distributed across a network of multiple computing devices. They can be implemented using computer-executable program code, and thus can be stored in a storage device for execution by a computing device. In some cases, the steps shown or described can be performed in a different order than those presented here, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Thus, this application is not limited to any particular combination of hardware and software.

[0118] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the principles of this application should be included within the protection scope of this application.

Claims

1. A frequency modulated continuous wave lidar, characterized in that, include: The system comprises a light source, a transceiver module, a detection module, and a data processing module. The light source includes both active and passive optical chips. The active optical chip is provided with a gain region and a phase region. The gain region is used to generate a modulated laser beam based on the received driving signal. The phase region is used to perform phase compensation on the modulated laser beam based on the received phase compensation signal to increase the modulation bandwidth of the modulated laser beam. The active optical chip provides the phase-compensated modulated laser beam to the passive optical chip, which then outputs it to the transceiver module.

2. The frequency-modulated continuous wave lidar of claim 1, wherein, The frequency-modulated continuous wave lidar also includes a driving circuit; wherein... The driving circuit is configured to generate the driving signal and provide it to the gain region, wherein the driving signal is a superposition signal of a DC bias signal and a modulation signal; and to generate the phase compensation signal and provide it to the phase region. The gain region is also used to generate a laser beam according to the DC bias signal and to modulate the laser beam according to the modulation signal to form the modulated laser beam.

3. The frequency-modulated continuous wave lidar according to claim 1, characterized in that, The passive optical chip includes: an input end-face mode converter, a wavelength selection feedback module, and an output end-face mode converter; wherein... The phase-compensated modulated laser beam is transmitted to the passive optical chip through the input end face modulated spot converter. Part of the phase-compensated modulated laser beam enters the resonant cavity composed of the active optical chip and the passive optical chip after passing through the wavelength selection feedback module to form optical feedback. The other part of the phase-compensated modulated laser beam is provided to the transceiver module through the output end face modulated spot converter.

4. The frequency-modulated continuous wave lidar according to claim 3, characterized in that, The laser mode selected by the wavelength selection window of the wavelength selection feedback module is located at the center of the wavelength selection window and the center of the gain spectrum of the active optical chip.

5. The frequency-modulated continuous wave lidar according to claim 3, characterized in that, The wavelength feedback device in the wavelength selective feedback module includes at least one of the following: a distributed Bragg grating, or a microring resonator.

6. The frequency-modulated continuous wave lidar according to claim 1, characterized in that, The gain region includes at least one of the following: a Fabry-Perot laser, a multimode reflective semiconductor optical amplifier, a distributed feedback laser, and a distributed Bragg reflector laser.

7. The frequency-modulated continuous wave lidar according to claim 1, characterized in that, The gain region is located before the phase region, or the phase region is located before the gain region.

8. The frequency-modulated continuous wave lidar according to claim 1, characterized in that, The waveguide extension direction of the active optical chip at the antireflection coating layer can be tilted at an angle of 0° relative to the normal direction of the end face surface, or between 5° and 8°.

9. The frequency-modulated continuous wave lidar according to claim 1, characterized in that, The passive optical chip is made of one of the following materials: silicon, silicon nitride, silicon dioxide, or lithium niobate thin film.

10. A driving method for a frequency-modulated continuous wave lidar, characterized in that, The frequency-modulated continuous wave lidar includes: a light source, a transceiver module, a detection module, and a data processing module. The light source includes an active optical chip and a passive optical chip, and the active optical chip has a gain region and a phase region. The method includes: A driving signal is applied to the gain region so that the gain region generates a modulated laser beam based on the driving signal; A phase compensation signal is applied to the phase region so that the phase region performs phase compensation on the modulated laser beam according to the phase compensation signal, thereby increasing the modulation bandwidth of the modulated laser beam; The phase-compensated modulated laser beam is provided to the passive optical chip.

Images