Laser radar, linear sweep-frequency laser and control method of linear sweep-frequency laser

Abstract

The invention provides a linear frequency sweeping laser, which comprises a light source and an outer cavity coupled with the light source, and is characterized in that the light source and the outer cavity form a resonant cavity, and the resonant cavity is provided with a plurality of longitudinal modes; the outer cavity comprises a tuning assembly and a band-pass filter, the band-pass filter is configured to select light corresponding to one longitudinal mode from a plurality of longitudinal modes and output the light from the laser to form output laser, and the frequency of the output laser is matched with the frequency of the selected longitudinal mode; the tuning assembly is configured to enable the frequency of the output laser to periodically and continuously change by adjusting the multiple longitudinal modes; the laser is configured to feed back and adjust working parameters of the laser according to the light intensity of the output laser, so that the frequency of the output laser is kept within a preset frequency range. The laser disclosed by the invention is an external cavity laser with a frequency modulation function, can be used for an FMCW laser radar, can work based on a feedback mechanism, and feeds back and adjusts the working parameters of the laser according to the light intensity of the output laser, so that the frequency of the output laser is kept within a preset frequency range.

Description

Technical Field

[0001] The present disclosure generally relates to the field of laser radar, and in particular to a linear frequency-sweeping laser, a control method for a linear frequency-sweeping laser, and a laser radar. Background Art

[0002] Frequency Modulated Continuous Wave (FMCW) lidar is a technology used in high-precision ranging. Its basic principle is that the transmitted wave is a high-frequency continuous wave, and its frequency changes over time according to a preset waveform rule, such as a triangular wave. The received echo frequency has the same change rule as the transmitted frequency, and both conform to the preset waveform. The time difference between the two can be used to calculate the target distance.

[0003] Linear frequency-sweep laser is the core technology of FMCW LiDAR, which can usually be divided into two categories: external modulation and direct modulation. Because of the high insertion loss of the modulator and the low side-mode suppression ratio (SMSR), the external modulation technology cannot use the semiconductor optical amplifier (SOA) as the subsequent amplifier, which is not conducive to the chip-based LiDAR. The most common light source for direct modulation is the distributed feedback laser (DFB). Although it has made great progress in recent years, DFB can achieve narrow linewidth (for example, less than 100kHz), but for ultra-long detection distance (for example, greater than 200m), there is still a gap. For FMCW LiDAR, the most promising development direction is the narrow-linewidth external cavity laser (ECDL) with frequency modulation function. Different from DFB lasers which are naturally mode-hopping free, external cavity lasers have mode-hopping characteristics. There have been some studies on the cavity longitudinal mode locking technology of external cavity lasers, but they are all focused on ordinary steady-state single-frequency external cavity lasers. FMCW-related frequency-modulated external cavity lasers have not yet been seen.

[0004] Therefore, how to design an external cavity laser suitable for FMCW lidar with better performance (such as frequency modulation, wide wavelength tuning, single-mode stable output, narrow linewidth, low loss, high side mode suppression ratio, long detection distance, high integration, etc.) is a need for continuous improvement in the lidar field.

[0005] The contents of the background technology section are merely the technologies known to the inventors and do not necessarily represent the prior art in the field. Summary of the invention

[0006] In view of one or more of the problems in the prior art, the present disclosure provides a linear frequency-sweeping laser. The laser disclosed in the present disclosure is an external cavity laser with a frequency modulation function, which can be used for FMCW laser radar and can work based on a feedback mechanism. According to the light intensity of the output laser, the operating parameters of the laser are adjusted by feedback, so that the frequency of the output laser is kept within a preset frequency range, thereby reducing or even eliminating the risk of mode hopping. The laser includes:

[0007] A light source and an external cavity coupled to the light source, wherein the light source and the external cavity form a resonant cavity having a plurality of longitudinal modes;

[0008] Wherein, the external cavity includes a bandpass filter and a tuning component;

[0009] The bandpass filter is configured to: select light corresponding to one of the longitudinal modes from the plurality of longitudinal modes and output it from the laser to form an output laser, wherein the frequency of the output laser matches the frequency of the selected longitudinal mode;

[0010] The tuning component is configured to: make the frequency of the output laser change periodically and continuously by adjusting the multiple longitudinal modes;

[0011] The laser is configured to feedback-adjust the working parameters of the laser according to the light intensity of the output laser so that the frequency of the output laser is maintained within a preset frequency range.

[0012] According to one aspect of the present disclosure, the operating parameters include the frequencies of the multiple longitudinal modes and / or the passband range of the bandpass filter.

[0013] According to one aspect of the present disclosure, the laser is configured to: feedback-adjust the frequencies of the multiple longitudinal modes according to the light intensity of the output laser, and / or feedback-adjust the passband range of the bandpass filter according to the light intensity of the output laser, so that the center frequency of the selected longitudinal mode matches the peak value of the bandpass filter, so that the frequency of the output laser is maintained within the preset frequency range.

[0014] According to one aspect of the present disclosure, the bandpass filter includes a broadband filter and a comb-shaped narrowband filter.

[0015] According to one aspect of the present disclosure, the broadband filter includes one of a grating and a filter; the comb-type narrowband filter includes one of a microring resonant cavity, a Fabry-Perot resonant cavity and a grating Fabry-Perot resonant cavity.

[0016] According to one aspect of the present disclosure, the tuning component includes a first phase shifter, and the first phase shifter is configured to adjust the frequencies of the multiple longitudinal modes so that any longitudinal mode of the multiple longitudinal modes changes periodically and continuously around its center frequency.

[0017] According to one aspect of the present disclosure, the first phase shifter comprises a lithium niobate phase shifter.

[0018] According to one aspect of the present disclosure, the tuning component further includes an injection current adjustment unit, which is configured to: change the injection current of the laser to adjust the frequencies of the multiple longitudinal modes so that any longitudinal mode among the multiple longitudinal modes changes periodically and continuously around its center frequency.

[0019] According to one aspect of the present disclosure, the laser is configured to: feedback-adjust the operating parameters of the laser according to the variation period of the light intensity of the output laser, so that the frequency of the output laser is maintained within the preset frequency range, specifically including: when the variation period of the light intensity and the preset frequency modulation period do not satisfy a first preset relationship, feedback-adjust the operating parameters of the laser, so that the frequency of the output laser is maintained within the preset frequency range.

[0020] According to one aspect of the present disclosure, the first preset relationship includes: the variation period of the light intensity is half of the preset frequency modulation period.

[0021] According to one aspect of the present disclosure, the laser is also configured to: feedback-adjust the operating parameters of the laser according to the first-order frequency intensity and the second-order frequency intensity of the light intensity of the output laser, so that the frequency of the output laser remains within the preset frequency range, specifically including: when the first-order frequency intensity and the second-order frequency intensity of the light intensity do not satisfy a second preset relationship, feedback-adjust the operating parameters of the laser, so that the frequency of the output laser remains within the preset frequency range.

[0022] According to one aspect of the present disclosure, the second preset relationship includes: the first-order frequency intensity of the light intensity is less than the second-order frequency intensity.

[0023] According to one aspect of the present disclosure, a second phase shifter is provided in the comb-shaped narrowband filter, and the second phase shifter is configured to adjust the resonant frequency of the comb-shaped narrowband filter to adjust the passband range of the comb-shaped narrowband filter.

[0024] According to one aspect of the present disclosure, the second phase shifter includes one or more of a lithium niobate phase shifter, a thermo-optical phase shifter, an electro-optical phase shifter, and a piezoelectric ceramic.

[0025] According to one aspect of the present disclosure, the resonant cavity further includes an oblique waveguide, and the oblique waveguide is disposed at an interface of the external cavity close to the light source to reduce reflection of light at the interface.

[0026] According to one aspect of the present disclosure, the light source comprises a semiconductor gain device.

[0027] The present disclosure also provides a control method for a linear frequency-sweeping laser, wherein the laser comprises a light source and an external cavity coupled to the light source, the light source and the external cavity forming a resonant cavity; the resonant cavity has a plurality of longitudinal modes; the external cavity comprises a bandpass filter and a tuning component; the control method comprises:

[0028] S11: selecting light corresponding to one of the longitudinal modes from the plurality of longitudinal modes through the bandpass filter and outputting the light from the laser to form an output laser, wherein the frequency of the output laser matches the frequency of the selected longitudinal mode;

[0029] S12: adjusting the multiple longitudinal modes by the tuning component so that the frequency of the output laser changes periodically and continuously;

[0030] S13: collecting the light intensity of the output laser of the laser; and

[0031] S14: According to the light intensity of the output laser of the laser, feedback is performed to adjust the working parameters of the laser so that the frequency of the output laser is maintained within a preset frequency range.

[0032] According to one aspect of the present disclosure, the operating parameters include a passband range of the bandpass filter and / or frequencies of the multiple longitudinal modes.

[0033] According to one aspect of the present disclosure, step S14 includes: feedback-adjusting the frequencies of the multiple longitudinal modes according to the light intensity of the output laser of the laser, and / or feedback-adjusting the passband range of the bandpass filter according to the light intensity of the output laser, so that the center frequency of the selected longitudinal mode matches the peak value of the bandpass filter, so that the frequency of the output laser is maintained within the preset frequency range.

[0034] According to one aspect of the present disclosure, the bandpass filter includes a broadband filter and a comb-shaped narrowband filter.

[0035] According to one aspect of the present disclosure, the broadband filter includes one of a grating and a filter; the comb-type narrowband filter includes one of a microring resonant cavity, a Fabry-Perot resonant cavity and a grating Fabry-Perot resonant cavity.

[0036] According to one aspect of the present disclosure, the tuning component includes a first phase shifter, and step S14 includes: adjusting the frequencies of the multiple longitudinal modes by the first phase shifter so that any longitudinal mode among the multiple longitudinal modes changes periodically and continuously around its center frequency.

[0037] According to one aspect of the present disclosure, the first phase shifter comprises a lithium niobate phase shifter.

[0038] According to one aspect of the present disclosure, the tuning component includes an injection current adjustment unit, and step S14 includes: changing the injection current of the laser through the injection current adjustment unit to adjust the frequencies of the multiple longitudinal modes so that any longitudinal mode among the multiple longitudinal modes changes periodically and continuously near its center frequency.

[0039] According to one aspect of the present disclosure, step S14 includes: feedback-adjusting the operating parameters of the laser according to the variation cycle of the light intensity of the output laser so that the frequency of the output laser remains within the preset frequency range, specifically including: when the variation cycle of the light intensity and the preset frequency modulation cycle do not satisfy a first preset relationship, feedback-adjusting the operating parameters of the laser so that the frequency of the output laser remains within the preset frequency range.

[0040] According to one aspect of the present disclosure, the first preset relationship includes: the variation period of the light intensity is half of the preset frequency modulation period.

[0041] According to one aspect of the present disclosure, step S14 further includes: feedback-adjusting the operating parameters of the laser according to the first-order frequency intensity and the second-order frequency intensity of the light intensity of the output laser, so that the frequency of the output laser remains within the preset frequency range, specifically including: when the first-order frequency intensity and the second-order frequency intensity of the light intensity do not satisfy a second preset relationship, feedback-adjusting the operating parameters of the laser, so that the frequency of the output laser remains within the preset frequency range.

[0042] According to one aspect of the present disclosure, the second preset relationship includes: the first-order frequency intensity of the light intensity is less than the second-order frequency intensity.

[0043] According to one aspect of the present disclosure, a second phase shifter is provided in the comb-shaped narrowband filter, and step S14 includes: adjusting the resonant frequency of the comb-shaped narrowband filter by the second phase shifter to adjust the passband range of the comb-shaped narrowband filter.

[0044] According to one aspect of the present disclosure, the second phase shifter includes one or more of a lithium niobate phase shifter, a thermo-optical phase shifter, an electro-optical phase shifter, and a piezoelectric ceramic.

[0045] According to one aspect of the present disclosure, the resonant cavity further includes an oblique waveguide, and the oblique waveguide is disposed at an interface of the external cavity close to the light source to reduce reflection of light at the interface.

[0046] According to one aspect of the present disclosure, the light source comprises a semiconductor gain device.

[0047] The present disclosure also provides a laser radar, comprising:

[0048] a transmitting device, comprising a laser as described above, configured to emit a laser beam;

[0049] A spectroscopic device configured to split the laser beam into a detection light and a local oscillator light, wherein the detection light is emitted to the outside of the laser radar;

[0050] A frequency mixing device configured to receive the echo light reflected by the detection light on the obstacle and the local oscillation light, and output a beat frequency signal;

[0051] a detection device configured to receive the beat frequency signal; and

[0052] A processing device is coupled to the detection device and is configured to calculate obstacle information based on the beat frequency signal.

[0053] According to one aspect of the present disclosure, the laser radar can execute the control method as described above.

[0054] In summary, the linear frequency sweeping laser, control method and laser radar of the present invention are introduced in detail. The laser of the present invention is an external cavity laser with a frequency modulation function, which can be used for FMCW laser radar, and the laser of the present invention can work based on a feedback mechanism. According to the light intensity of the output laser, the working parameters of the laser are adjusted by feedback to keep the frequency of the output laser within a preset frequency range.

[0055] Furthermore, the laser disclosed in the present invention can feedback-adjust the operating parameters of the laser according to the variation period of the light intensity of the output laser, and / or according to the first-order frequency intensity and the second-order frequency intensity of the output laser, so that the center frequency of the selected longitudinal mode matches the peak value of the bandpass filter, so that the frequency of the output laser is maintained within a preset frequency range.

[0056] Furthermore, the laser disclosed in the present invention can modulate the frequencies of multiple longitudinal modes through a tuning component, so that the frequency of the output laser changes periodically and continuously. The tuning component can be a lithium niobate phase shifter, thereby achieving rapid frequency modulation.

[0057] Furthermore, the laser disclosed in the present invention can effectively reduce or even avoid the real-time optical phase-locked loop by introducing a pre-distortion signal into the voltage signal of the first phase shifter and / or the second phase shifter, reduce nonlinearity, reduce cost and technical complexity, and facilitate the output laser to present a better linear frequency sweeping effect.

[0058] Furthermore, the laser disclosed in the present invention utilizes the periodic variation law of the output laser for feedback modulation, that is, utilizes the AC signal of the output laser for feedback modulation. Compared with directly utilizing the power of the output laser for modulation, it has a higher signal-to-noise ratio and is more conducive to matching the center frequency of the selected longitudinal mode with the peak value of the bandpass filter.

[0059] Furthermore, the laser disclosed in the present invention can reduce the difficulty of bandwidth matching by using a grating as a broadband filter and an MRR as a comb-shaped narrowband filter, which is beneficial for matching the center frequency of the longitudinal mode with the peak of the bandpass filter, thereby reducing or even eliminating the risk of mode hopping and allowing the laser to operate stably.

[0060] The laser disclosed in the present invention can be frequency modulated and can achieve single-mode stable output. It has better detection performance such as wide wavelength tuning range, narrow line width, low loss, high side mode suppression ratio, long detection distance, and high integration, and is suitable for FMCW laser radar. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the embodiments of the present disclosure, they are used to explain the present disclosure and do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0062] Figure 1 A schematic diagram of a linearly swept laser according to an embodiment of the present disclosure is shown;

[0063] Figure 2 A schematic diagram showing the formation of output laser according to an embodiment of the present disclosure is shown;

[0064] Figure 3 A schematic diagram showing a bandpass filter and its working principle according to an embodiment of the present disclosure is shown;

[0065] Figure 4 A schematic diagram showing the matching of the center frequency of the longitudinal mode with the peak value of the bandpass filter according to an embodiment of the present disclosure;

[0066] Figure 5 A schematic diagram showing a curve of frequency variation of output laser light over time according to an embodiment of the present disclosure is shown;

[0067] Figure 6 A schematic diagram showing the mismatch between the center frequency of the longitudinal mode and the peak value of the bandpass filter according to an embodiment of the present disclosure;

[0068] Figure 7 A schematic diagram showing a linear frequency modulation process of a laser when the center frequency of a longitudinal mode matches the peak value of a bandpass filter according to an embodiment of the present disclosure is shown;

[0069] Figure 8 A schematic diagram of the spectrum of the output laser when the center frequency of the longitudinal mode matches the peak value of the bandpass filter according to one embodiment of the present disclosure is shown;

[0070] Fig. 9A schematic diagram showing a linear frequency modulation process of a laser when the center frequency of a longitudinal mode is mismatched with the peak value of a bandpass filter according to an embodiment of the present disclosure is shown;

[0071] Fig.10 A schematic diagram of the spectrum of the output laser when the center frequency of the longitudinal mode according to an embodiment of the present disclosure is mismatched with the peak value of the bandpass filter is shown;

[0072] Figure 11-Figure 14 A schematic diagram showing a specific structure of a laser according to some embodiments of the present disclosure is shown;

[0073] Fig.15 A flow chart showing a method for controlling a linear frequency swept laser according to an embodiment of the present disclosure; and

[0074] Fig.16 A schematic diagram of a laser radar according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0075] In the following, only certain exemplary embodiments are described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present disclosure. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0076] In the description of the present disclosure, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present disclosure and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present disclosure. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present disclosure, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0077] In the description of the present disclosure, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or can communicate with each other; it can be directly connected, or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.

[0078] In the present disclosure, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0079] The disclosure below provides many different embodiments or examples to realize different structures of the present disclosure. In order to simplify the disclosure of the present disclosure, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present disclosure. In addition, the present disclosure can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplicity and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present disclosure provides various specific examples of processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0080] Exemplary embodiments of the present disclosure are described below in conjunction with the accompanying drawings. It should be understood that the exemplary embodiments described herein are only used to illustrate and explain the present disclosure, and are not used to limit the present disclosure.

[0081] Figure 1 A schematic diagram of a linear frequency swept laser 100 according to an embodiment of the present disclosure is shown. Figure 1 As shown, the laser 100 includes a light source 10 and an external cavity 20 coupled to the light source 10, wherein the light source 10 and the external cavity 20 constitute a resonant cavity 30, and the resonant cavity 30 has a plurality of longitudinal modes (refer to Figure 2); the external cavity 20 includes a bandpass filter 21 and a tuning component 22; the bandpass filter 21 is configured to select light corresponding to one of the longitudinal modes from the plurality of longitudinal modes and output from the laser 100 to form an output laser Light, wherein the frequency of the output laser Light (i.e., the lasing frequency) matches the frequency of the selected longitudinal mode (refer to Figure 2 ); the tuning component 22 is configured to adjust the plurality of longitudinal modes so that the frequency of the output laser Light changes periodically and continuously (reference Figure 5 , which will be described in detail later); the laser 100 is configured to feedback adjust the operating parameters of the laser 100 according to the light intensity of the output laser Light, so that the frequency of the output laser Light is maintained within a preset frequency range (refer to Figure 5 , which will be described in detail later). The laser disclosed in the present invention is an external cavity laser with a frequency modulation function, which can be used for FMCW laser radar. The laser disclosed in the present invention is described in detail below.

[0082] In the laser disclosed in the present invention, the light source 10 is used to generate photons and perform signal gain. Optionally, the light source 10 may include a pump source (Pump Source) and a semiconductor gain device SOA (Semiconductor Optical Amplifier, SOA). The pump source can be coupled to the semiconductor gain device SOA to inject photons into the semiconductor gain device SOA. The semiconductor gain device SOA can be used to amplify the optical signal emitted by the pump source. Integrating the pump source and the semiconductor gain device into the light source is beneficial to improving the integration of the laser and realizing chip design. Optionally, the semiconductor gain device SOA can adopt a reflective semiconductor gain device RSOA (Reflective Semiconductor Optical Amplifier, RSOA).

[0083] In the laser disclosed in the present invention, the external cavity 20 can be a discrete device external cavity or a chip external cavity. The discrete device external cavity can be, for example, a fiber grating external cavity, a grating external cavity, etc., which is easy to disassemble; the chip external cavity can be, for example, a silicon-based external cavity, a thin-film lithium niobate external cavity, etc., which is conducive to improving the integration of the laser. In specific applications, a suitable external cavity can be designed according to actual conditions.

[0084] In the laser disclosed in the present invention, the external cavity 20 and the light source 10 can be directly coupled or indirectly coupled to form a resonant cavity 30. The light emitted by the light source 10 can resonate in the resonant cavity 30 to generate multiple longitudinal modes (i.e., resonance peaks). The bandpass filter 21 can select light corresponding to one of the longitudinal modes from the multiple longitudinal modes to output from the laser to form an output laser Light. The frequency of the output laser Light matches the frequency of the selected longitudinal mode. For example, the frequency of the output laser Light is equal to the frequency of the selected longitudinal mode. Figure 2 , the transmission spectrum of the bandpass filter 21 is relatively narrow, and the light corresponding to the longitudinal mode matching the peak value (hereinafter referred to as the peak value) of the transmission spectrum of the bandpass filter 21 has the highest transmittance. Through mode competition, the light corresponding to the longitudinal mode matching the peak value of the bandpass filter 21 successfully competes to be emitted from the laser to form the output laser Light, while the light corresponding to other longitudinal modes fails to compete and is suppressed, thereby achieving frequency (or wavelength) selection. Therefore, the bandwidth of the bandpass filter 21 can be relatively narrow, which is conducive to forming a single-frequency stable output laser Light, so that the laser can operate stably at a single frequency.

[0085] Figure 3 A schematic diagram showing a bandpass filter 21 and its working principle according to an embodiment of the present disclosure is shown, referring to Figure 3 The bandpass filter 21 includes a broadband filter 21-1 (Wideband Filter) and a comb narrowband filter 21-2 (CombNarrowband Filter), and the broadband filter 21-1 and the comb narrowband filter 21-2 are combined to form the bandpass filter 21. Optionally, the broadband filter 21-1 includes one of a grating and a filter; the comb narrowband filter 21-2 includes one of a microring resonator (MRR), a Fabry-Perot resonator (FP resonator) and a grating Fabry-Perot resonator (grating FP resonator), and the specific situation will be described in detail in the specific structure of the laser later.

[0086] In the laser disclosed in the present invention, the tuning component 22 is used for frequency modulation. By adjusting multiple longitudinal modes, the frequency of the output laser Light changes periodically and continuously, thereby realizing linear frequency sweeping. Specifically, the tuning component 22 can make the multiple longitudinal modes move back and forth within a certain frequency range (i.e., change periodically and continuously). Figure 4Taking one of the longitudinal modes as an example, the tuning component 22 can make the longitudinal mode change continuously and periodically within the frequency range of [f1, f2] with the center frequency f0 as the reference, and the change period is T (that is, the frequency modulation period is T). Other longitudinal modes are similar, and they all change continuously and periodically near their respective center frequencies. In other words, the tuning component 22 can adjust the frequencies of multiple longitudinal modes so that any of the multiple longitudinal modes changes continuously and periodically near its center frequency. Since the frequency of the output laser Light is equal to the frequency of the selected longitudinal mode, the center frequency of the output laser Light is equal to the center frequency of the selected longitudinal mode. When the selected longitudinal mode changes continuously and periodically within the frequency range of [f1, f2] with its center frequency f0 as the reference and T as the period, the center frequency of the output laser Light also changes continuously within the frequency range of [f1, f2] with f0 as the center frequency and T as the period. Linear frequency sweeping can be achieved. More intuitively, refer to Figure 5 The frequency variation curve of the output laser Light is shown. In this embodiment, the linear frequency modulation mode of the output laser Light is triangular wave linear frequency modulation. Although not shown in the figure, it can be understood that the frequency variation curve of the output laser Light can also be other waveforms.

[0087] In the present disclosure, the frequency (or wavelength) of the output laser Light can be modulated according to the requirements. Assuming that the required wavelength of the output laser Light is 1550nm, the tuning component 22 can be linearly modulated near the wavelength 1550nm, so that the output laser Light changes periodically and continuously within a preset frequency range, for example, within a frequency range of [1549.997, 1550.003]. The change curve can be referred to Figure 5 As shown. It should be noted that this embodiment only takes the wavelength of 1550nm as an example for introduction. Other wavelengths (or frequencies) are similar and will not be described here. Therefore, compared with a single-frequency laser, the laser disclosed in the present invention has a frequency modulation function, a wider tunable range, and can be flexibly tuned according to demand, with strong dynamic adjustment capability, and is suitable for FMCW laser radar.

[0088] According to one embodiment of the present disclosure, the tuning component 22 includes a first phase shifter PS1 (Phase Shifter, see Fig.11 ), the first phase shifter PS1 is configured to adjust the frequencies of the multiple longitudinal modes so that any longitudinal mode among the multiple longitudinal modes changes periodically and continuously near its center frequency.

[0089] According to another embodiment of the present disclosure, the tuning component 22 further includes an injection current adjustment unit CS (Current Shifter, see Fig.11), the injection current adjustment unit CS is configured to change the injection current of the laser to adjust the frequencies of multiple longitudinal modes so that any longitudinal mode among the multiple longitudinal modes changes periodically and continuously near its center frequency.

[0090] In order to ensure that the laser can stably output laser light within the preset frequency range, it is necessary to ensure that the preset frequency range is within the passband range of the bandpass filter, and the bandpass filter has a high transmittance for light within the preset frequency range and a low transmittance for light outside the preset frequency range, so that the light within the preset frequency range can be successfully lasered out through the competition mode. In addition, it is also necessary to ensure that the center frequency of the selected longitudinal mode matches the peak value of the bandpass filter (refer to Figure 2 , Figure 3 , Figure 4 ) to ensure that during the linear frequency sweep process, the transmittance of the light corresponding to the selected longitudinal mode is the highest, so that the light corresponding to the selected longitudinal mode can be output stably.

[0091] However, during the long-term operation of the laser, due to changes in device parameters or operating parameters, or due to the influence of other parameters, the center frequency of the longitudinal mode may mismatch with the peak value of the bandpass filter (refer to Figure 6 ), that is, the center frequency of the longitudinal mode is offset from the peak of the bandpass filter. Once the mismatch reaches a certain degree, the laser output frequency will be unstable or even mode hopping will occur, which will have an adverse effect on the detection performance of the laser radar. Figure 6 , assuming that the center frequency of the selected longitudinal mode A expected to be output is f0, and the center frequency of the other longitudinal mode B is f0'. The center frequency f0 of longitudinal mode A has a certain offset from the peak of the bandpass filter. In the case of no frequency modulation, the longitudinal mode A corresponding to the frequency f0 has the highest transmittance, so it can be emitted from the laser, that is, the output frequency of the laser is f0 at this time. According to the design requirements of frequency modulation, the output frequency of the laser changes slightly around f0. As can be seen from the figure, in the case of frequency modulation, when the center frequency of longitudinal mode A is modulated from f0 to f2, the center frequency of longitudinal mode B is synchronously modulated from f0' to f2'. At this time, the transmittance of longitudinal mode B with a frequency of f2' is already higher than the transmittance of longitudinal mode A with a frequency of f2. According to mode competition, longitudinal mode A with a frequency of f2 is suppressed, and longitudinal mode B with a frequency of f2' will be emitted from the laser. At this time, the output frequency of the laser undergoes a longitudinal mode jump, that is, a mode hop occurs. Therefore, in FMCW applications, in order to ensure that the laser can operate stably for a long time, the center frequency of the selected longitudinal mode needs to match the peak of the bandpass filter, that is, the frequency modulation center of the laser needs to be locked at the peak of the bandpass filter to overcome or alleviate the problem of laser instability or even mode hopping.

[0092] To this end, the present disclosure further proposes a feedback mechanism that can control the frequency modulation center of the laser to be locked at the peak of the bandpass filter. Taking the triangular wave linear frequency modulation as an example, the preset frequency modulation period is T, the preset frequency modulation range is [f1, f2], and the process of the frequency increasing from f1 to f2 and then decreasing to f1 is one frequency modulation period T. Figure 7 As shown in (a), when the center frequency f0 of the longitudinal mode matches the peak of the bandpass filter, when the frequency increases from f1 to f0, the corresponding light transmittance gradually increases from b to a; when the frequency increases from f0 to f2, the corresponding light transmittance gradually decreases from a to b; when the frequency decreases from f2 to f0, the corresponding light transmittance gradually increases from b to a; when the frequency decreases from f0 to f1, the corresponding light transmittance gradually decreases from a to b. It can be seen that within one frequency modulation period T, the corresponding light transmittance undergoes a process of increasing from b to a and then decreasing to b twice. Refer to Figure 7 As shown in (c), the output laser light intensity (output power) corresponds to the transmittance, and also experiences two processes of increasing from P1 to P2 and then decreasing to P1. The output laser light intensity (power) also shows periodic changes, with a change period of T'. By comparison Figure 7 It can be seen from (b) and (c) that when the longitudinal mode center frequency f0 matches the peak value of the bandpass filter, the variation period T' of the output laser light intensity (power) and the frequency modulation period T satisfy a first preset relationship, wherein the first preset relationship includes that the variation period T' of the output laser light intensity (power) is half of the preset frequency modulation period T, i.e., T'=1 / 2T. In other words, the preset frequency modulation period T is twice the variation period T' of the output laser light intensity (power), i.e., T=2T'. Figure 8 , a spectrum analysis is performed on the light intensity (power) of the output laser. When the longitudinal mode center frequency f0 matches the peak value of the bandpass filter, the first-order frequency intensity (i.e., the first-order frequency AC signal intensity, the intensity corresponding to the frequency of 100 in the figure) and the second-order frequency intensity (i.e., the second-order frequency AC signal intensity, the intensity corresponding to the frequency of 200 in the figure) of the light intensity (power) of the output laser satisfy a second preset relationship, and the second preset relationship includes that the first-order frequency intensity of the light intensity (power) of the output laser is less than the second-order frequency intensity.

[0093] The above embodiment introduces the variation law of the light intensity (power) of the output laser in the frequency modulation process, when the longitudinal mode center frequency matches the peak value of the bandpass filter, that is, the variation period T' of the light intensity (power) of the output laser satisfies the first preset relationship with the frequency modulation period T, and the first-order frequency intensity and the second-order frequency intensity of the light intensity (power) of the output laser satisfy the second preset relationship. When other conditions remain unchanged, in the frequency modulation process, if the longitudinal mode center frequency mismatches the peak value of the bandpass filter, the periodic variation of the light intensity (power) of the output laser will change, which is described in detail below.

[0094] Reference Fig. 9 As shown in (a), during the frequency modulation process, if the longitudinal mode center frequency and the peak value of the bandpass filter are mismatched, the relative positions of the two are offset. At this time, the light transmittance corresponding to the longitudinal mode center frequency f0 is not the maximum value. Therefore, in a frequency modulation period T where the frequency increases from f1 to f2 via f0 and then decreases from f2 to f1 via f0, the corresponding light transmittance decreases from b to c after passing through the maximum value a, and then from c to b after passing through the maximum value a (where b is not equal to c). Refer to Fig. 9 As shown in (c), the light intensity (power P) of the output laser corresponds to the transmittance, which decreases from P1 to P3 via the maximum value P2, and then increases from P3 to P2 via P1 and then decreases to P1 (P1≠P3). Fig. 9 It can be seen from (b) and (c) that when the longitudinal mode center frequency f0 is mismatched with the peak value of the bandpass filter, the variation period T' of the output laser light intensity (power) and the frequency modulation period T no longer satisfy the first preset relationship, that is, the variation period T' of the output laser light intensity (power) is no longer half of the preset frequency modulation period T, that is, T'≠1 / 2T, or T≠2T'. And in this embodiment, the variation period T' of the output laser light intensity (power) is equal to the frequency modulation period T, that is, T'=T. It should be understood that this embodiment is only an exemplary description and does not constitute a limitation of the present disclosure. In addition, refer to Fig.10 , a spectrum analysis is performed on the light intensity (power) of the output laser. When the longitudinal mode center frequency f0 is mismatched with the peak value of the bandpass filter, the first-order frequency intensity of the light intensity (power) of the output laser is significantly enhanced, and the first-order frequency intensity and the second-order frequency intensity of the light intensity (power) of the output laser no longer satisfy the second preset relationship, that is, the first-order frequency intensity of the light intensity (power) of the output laser is no longer less than the second-order frequency intensity.

[0095] Figures 7 to 10 The embodiments of the invention respectively introduce different variation rules of the intensity (power) of the output laser in the frequency modulation process under different conditions of matching and mismatching of the center frequency of the longitudinal mode with the peak value of the bandpass filter. The present disclosure proposes a linear frequency sweeping laser, which adjusts the working parameters of the laser by feedback according to the intensity (power) of the output laser, so that the center frequency of the selected longitudinal mode matches the peak value of the bandpass filter, so that the frequency of the output laser is kept within a preset frequency range.

[0096] According to an embodiment of the present disclosure, the laser can feedback-adjust the operating parameters of the laser according to the variation cycle of the light intensity of the output laser, so that the frequency of the output laser is maintained within a preset frequency range. Specifically, when the variation cycle T' of the light intensity of the output laser does not satisfy the first preset relationship with the preset frequency modulation cycle T, that is, when the variation cycle T' of the light intensity is not equal to half of the preset frequency modulation cycle T, the operating parameters of the laser are feedback-adjusted so that the frequency of the output laser is maintained within the preset frequency range.

[0097] According to another embodiment of the present disclosure, the laser can also feedback-adjust the operating parameters of the laser according to the first-order frequency intensity and the second-order frequency intensity of the light intensity of the output laser, so that the frequency of the output laser is maintained within a preset frequency range. Specifically, when the first-order frequency intensity and the second-order frequency intensity of the light intensity of the output laser do not satisfy the second preset relationship, that is, when the first-order frequency intensity of the light intensity is not less than the second-order frequency intensity, the operating parameters of the laser are feedback-adjusted so that the frequency of the output laser is maintained within the preset frequency range.

[0098] In the present disclosure, the operating parameters of the laser may include the frequencies of multiple longitudinal modes. The laser may feedback-adjust the frequencies of the multiple longitudinal modes according to the light intensity (power) of the output laser, so that the center frequency of the selected longitudinal mode matches the peak value of the bandpass filter, so that the frequency of the output laser remains within a preset frequency range. As described above, the tuning component 22 may be used for frequency modulation, so the frequencies of the multiple longitudinal modes may be feedback-adjusted by the tuning component 22. As described above, the tuning component 22 includes a first phase shifter PS1 (Phase Shifter, see Fig.11 ), according to one embodiment of the present disclosure, the frequencies of multiple longitudinal modes can be adjusted by the first phase shifter PS1 so that the center frequency of the selected longitudinal mode matches the peak value of the bandpass filter, so that the frequency of the output laser is maintained within a preset frequency range. Optionally, the first phase shifter PS1 includes a lithium niobate phase shifter. The lithium niobate phase shifter has a stable first-order linear electro-optic effect, introduces less nonlinearity during the frequency modulation process, is suitable for the FMCW tuning mechanism, and can achieve fast frequency modulation. Optionally, the first phase shifter PS1 may also include one or more of a thermo-optic phase shifter, an electro-optic phase shifter, and a piezoelectric ceramic. According to another embodiment of the present disclosure, the tuning component 22 also includes an injection current adjustment unit CS (Current Shifter, refer to Fig.11 ), the injection current of the laser can be changed by the injection current adjustment unit CS to adjust the frequencies of the multiple longitudinal modes so that the center frequency of the selected longitudinal mode matches the peak value of the bandpass filter, so that the frequency of the output laser is maintained within a preset frequency range.

[0099] In the present disclosure, the operating parameters of the laser also include the passband range of the bandpass filter. The laser can adjust the passband range of the bandpass filter by feedback according to the light intensity (power) of the output laser, so that the center frequency of the selected longitudinal mode matches the peak value of the bandpass filter, so that the frequency of the output laser is kept within the preset frequency range. According to one embodiment of the present disclosure, the second phase shifter PS2 (refer to Fig.11), the resonant frequency of the comb-shaped narrowband filter 21-2 can be adjusted by the second phase shifter PS2 to adjust the passband range of the comb-shaped narrowband filter 21-2. Specifically, the second phase shifter PS can reversely track the movement of multiple longitudinal modes by changing the resonant frequency of the comb-shaped narrowband filter 21-2, so that the center frequency of the selected longitudinal mode matches the peak value of the bandpass filter, so that the frequency of the output laser is kept within the preset frequency range.

[0100] As mentioned above, the bandpass filter 21 includes a broadband filter 21-1 and a comb-shaped narrowband filter 21-2. The bandwidth of the comb-shaped narrowband filter 21-2 is narrower. In a specific embodiment of the present disclosure, the free spectral range of the comb-shaped narrowband filter 21-2 is fsr=C / (2nπR), and the longitudinal mode spacing is C / (2nL), n is the refractive index, C is the speed of light in a vacuum, 2πR is the ring length of the microring resonator (MRR), and L is the cavity length of the resonator. The ratio of the two is greater than one order of magnitude. Therefore, the second phase shifter PS2 is set in the comb-shaped narrowband filter 21-2, which is conducive to spectrum movement and has lower power consumption, which is conducive to achieving a larger adjustment range and faster adjustment speed. The present disclosure does not limit the specific device of the second phase shifter. Optionally, the second phase shifter includes one or more of a lithium niobate phase shifter, a thermo-optical phase shifter, an electro-optical phase shifter, and a piezoelectric ceramic. In this embodiment, the second phase shifter can be set in the comb-shaped narrowband filter 21-2, but the present disclosure is not limited thereto. Alternatively, the second phase shifter may also be provided in the broadband filter 21 - 1 , which is within the protection scope of the present disclosure.

[0101] In a specific embodiment of the present disclosure, the mismatch between the longitudinal mode center frequency and the bandpass filter can be determined by detecting the first-order frequency intensity of the periodic signal of the light intensity (power) of the output laser of the laser, and the size and direction of the feedback amount can be calculated, and then the relative position of the longitudinal mode center frequency and the peak value of the bandpass filter can be fed back to match the longitudinal mode center frequency with the peak value of the bandpass filter, wherein the feedback direction can be determined by the phase of the first-order frequency.

[0102] In order to make the output laser of the laser present a better linear frequency sweep effect, optionally, a pre-distortion signal can be introduced into the voltage signal loaded on the first phase shifter and / or the second phase shifter, wherein the pre-distortion signal can be calibrated in advance. The laser disclosed in the present invention works based on a feedback mechanism, and the working parameters of the laser are adjusted by feedback, so that the laser can always be at the working point when initially calibrated during operation, that is, the longitudinal mode center frequency can be maintained to match the peak value of the bandpass filter, thereby maintaining the long-term effectiveness of the pre-distortion signal, reducing or even avoiding a real-time optical phase-locked loop (Optical PhaseLock Loop, OPLL), reducing nonlinearity, and reducing costs and technical complexity.

[0103] The above embodiments respectively introduce two ways of feedback-adjusting the working parameters of the laser, one of which is feedback-adjusting the frequencies of multiple longitudinal modes, which can be specifically feedback-adjusted through the first phase shifter or the current adjustment unit in the tuning component; the other is feedback-adjusting the passband range of the bandpass filter, which can specifically be adjusted through the second phase shifter in the comb narrowband filter to adjust the resonant frequency of the comb narrowband filter to adjust the passband range of the comb narrowband filter, thereby adjusting the passband range of the bandpass filter. In addition, the frequencies of multiple longitudinal modes and the passband range of the bandpass filter can also be adjusted in parallel. By adjusting the frequencies of multiple longitudinal modes and / or the passband range of the bandpass filter, feedback adjustment of the working parameters of the laser can be achieved, so that the center frequency of the selected longitudinal mode matches the peak value of the bandpass filter, so that the frequency of the output laser remains within the preset frequency range.

[0104] As mentioned above, in the laser of the present disclosure, the broadband filter 21-1 includes one of a grating and a filter; the comb narrowband filter 21-2 includes one of a microring resonator (MRR), a Fabry-Perot resonator (FP resonator) and a grating Fabry-Perot resonator (grating FP resonator). The following introduces some specific structures of the laser of the present disclosure.

[0105] Fig.11 The specific structure of a laser according to an embodiment of the present disclosure is shown. In this embodiment, the broadband filter 21-1 includes a grating, and the comb-shaped narrowband filter 21-2 includes a microring resonant cavity. The bandwidth matching of the grating and the microring resonant cavity can be equivalent to a bandpass filter, and the second phase shifter PS2 can be set in the microring resonant cavity.

[0106] In some existing laser schemes, the bandpass filter includes two microring resonators, and the bandwidth of the microring resonator is relatively narrow, so it is difficult to completely match the peak values ​​of the two microring resonators, and the process requirements are relatively high when used for narrowband filters. In the laser scheme disclosed in the present invention, the bandpass filter can include one grating and one microring resonator, the bandwidth of the grating is relatively wide, and the bandwidth of the microring resonator is relatively narrow, so the bandwidth matching difficulty of the broadband filter and the comb-shaped narrowband filter can be reduced, and it is easy to achieve matching of the longitudinal mode center frequency with the peak value of the bandpass filter, and the manufacturing difficulty can also be reduced.

[0107] like Fig.11As shown, in this embodiment, the grating (broadband filter 21-1) can also constitute the first cavity mirror M1 of the resonant cavity. Optionally, the semiconductor gain device SOA includes a reflective semiconductor gain device RSOA. Optionally, a high-reflection film or a reflector can be provided on the side of the semiconductor gain device SOA away from the external cavity 20 to constitute the second cavity mirror M2 of the resonant cavity. Optionally, the light source 10 may include a pump source, which may be coupled to the semiconductor gain device SOA and inject photons into the semiconductor gain device SOA. The semiconductor gain device SOA is used to amplify the optical signal emitted by the pump source, which is beneficial to improve the integration of the laser and realize chip design. Optionally, the resonant cavity may include an oblique waveguide OW (Oblique Waveguide), which may be provided at the interface of the external cavity 20 close to the light source 10 to reduce the reflection of light at the interface, reduce or even eliminate the interference of the FP effect, and is beneficial to improve the anti-interference ability and signal-to-noise ratio of the laser. Optionally, the resonant cavity may also include a straight waveguide SW (Straight Waveguide), which may be connected to the oblique waveguide OW. Optionally, a tuning component 22 may be disposed at the straight waveguide SW to change the frequency of the longitudinal mode, thereby achieving linear frequency modulation of the output laser.

[0108] Fig.12 The specific structure of the laser according to another embodiment of the present disclosure is shown. In this embodiment, the broadband filter 21-1 includes a filter plate, and the comb-shaped narrowband filter 21-2 includes a micro-ring resonant cavity. The bandwidth matching of the filter plate and the micro-ring resonant cavity is equivalent to a bandpass filter. In other words, Fig.11 The grating in can be replaced by a filter. Optionally, the filter can be arranged between the semiconductor gain device SOA and the external cavity 20. Optionally, optical elements OE (Optical Element) can be respectively arranged on the side of the filter close to the semiconductor gain device SOA and the side away from the semiconductor gain device SOA for light path modulation. It should be noted that the present disclosure does not limit the specific surface shape and number of the optical elements, which can be flexibly set according to actual needs. Optionally, the resonant cavity also includes a loop mirror, which can be the first cavity mirror M1 of the resonant cavity.

[0109] Fig.13The specific structure of the laser according to another embodiment of the present disclosure is shown. In this embodiment, the broadband filter 21-1 includes a grating, the comb narrowband filter 21-2 includes a grating FP resonant cavity, and is used in conjunction with a polarization beam splitter (Polarization Beam Splitter, PBS) and two quarter-wave plates (quarter-wave plates). Among them, the grating FP resonant cavity includes a first grating G1 and a second grating G2, and the second phase shifter PS2 can be arranged between the first grating G1 and the second grating G2. Optionally, the first quarter-wave plate Q1 and the second quarter-wave plate Q2 can be arranged on both sides of the grating FP resonant cavity. Optionally, the polarization beam splitter PBS can be arranged between the semiconductor gain device SOA and the first quarter-wave plate Q1. Optionally, the polarization beam splitter PBS can be arranged at the oblique waveguide OW between the semiconductor gain device SOA and the first quarter-wave plate Q1 to further suppress the reflection of light. Optionally, the grating (broadband filter 21-1) can be arranged on the right side of the second quarter-wave plate Q2, and the grating can constitute the first cavity mirror M1 of the resonant cavity. Optionally, the tuning component 22 may be disposed between the polarization beam splitter PBS and the first quarter wave plate Q1 .

[0110] Reference Fig.13 , the polarization beam splitter PBS only allows P light to pass through, and the light injected into the external cavity is modulated by the polarization beam splitter PBS and only allows P light to pass through. After the first quarter wave plate Q1 acts, the phase is rotated by 45 degrees, and resonance occurs in the resonance cavity formed by the first grating G1 and the second grating G2, and a comb-shaped narrow-band resonance peak is output from the right side of the second grating G2. Since the first grating G1 and the second grating G2 both have high reflectivity, in order to reduce or even avoid the unwanted light reflected back to the semiconductor gain device SOA at the first grating G1 and the second grating G2, this part of the reflected light can be suppressed or even blocked by the first quarter wave plate Q1 and the polarization beam splitter PBS. Specifically, the light reflected at the first grating G1 and the second grating G2 is phase-rotated by 45 degrees after the first quarter wave plate Q1 acts, and becomes S light, which cannot pass through the polarization beam splitter PBS, so this part of the reflected light can be suppressed or even blocked. It should be understood that the light reflected by the grating (i.e., the first cavity mirror M1) in the broadband filter 21-1 can be reflected back to the semiconductor gain device SOA. This is because the round-trip optical path passes through the quarter-wave plate four times, and the phase is still P light after rotation, so it can return to the semiconductor gain device SOA through the polarization beam splitter PBS. It should be noted that the grating in the broadband filter 21-1 in this embodiment can also be replaced by a filter, which is within the protection scope of the present disclosure.

[0111] Fig.14 The specific structure of the laser according to another embodiment of the present disclosure is shown. Fig.13Compared with the embodiment of the present invention, in this embodiment, the comb narrowband filter 21-2 includes an FP resonant cavity, the FP resonant cavity includes a first reflector R1 and a second reflector R2, and the second phase shifter PS2 can be arranged between the first reflector R1 and the second reflector R2. Optionally, the first reflector R1 and the second reflector R2 can also be replaced by a reflective film. It should be understood that the grating in the broadband filter 21-1 can be replaced by a filter.

[0112] Figure 11-Figure 14 The embodiments of the present invention introduce some implementation methods of the laser. It should be noted that the specific structure of the laser is not limited to this. In actual use, some components can be added or reduced according to needs, and even in the above Figure 11-Figure 14 The embodiments of the present invention are combined and implemented, all of which are within the protection scope of the present disclosure.

[0113] The laser 100 of the present disclosure is introduced in detail above. The present disclosure also provides a control method 200 of a linear frequency swept laser 100, wherein the laser 100 includes a light source 10 and an external cavity 20 coupled to the light source 10, the light source 10 and the external cavity 20 constitute a resonant cavity 30; the resonant cavity 30 has multiple longitudinal modes; the external cavity 20 includes a bandpass filter 21 and a tuning component 22.

[0114] Fig.15 A flow chart of a control method 200 according to an embodiment of the present disclosure is shown. Fig.15 As shown, the control method 200 includes steps S11-S14. In step S11, light corresponding to one of the longitudinal modes is selected from the plurality of longitudinal modes by the bandpass filter 21 and output from the laser 100 to form an output laser, and the frequency of the output laser matches the frequency of the selected longitudinal mode. In step S12, the plurality of longitudinal modes are adjusted by the tuning component 22 so that the frequency of the output laser changes periodically and continuously. In step S13, the light intensity of the output laser of the laser 100 is collected. In step S14, the operating parameters of the laser 100 are adjusted according to the light intensity of the output laser of the laser 100 so that the frequency of the output laser is kept within a preset frequency range.

[0115] According to an embodiment of the present disclosure, the operating parameters include the passband range of the bandpass filter 21 and / or the frequencies of the multiple longitudinal modes.

[0116] According to one embodiment of the present disclosure, step S14 includes: feedback-adjusting the passband range of the bandpass filter 21 according to the light intensity of the output laser of the laser 100, and / or feedback-adjusting the frequencies of the multiple longitudinal modes according to the light intensity of the output laser, so that the center frequency of the selected longitudinal mode matches the peak value of the bandpass filter 21, so that the frequency of the output laser is maintained within the preset frequency range.

[0117] According to an embodiment of the present disclosure, the bandpass filter 21 includes a broadband filter 21 - 1 and a comb-shaped narrowband filter 21 - 2 .

[0118] According to one embodiment of the present disclosure, the broadband filter 21-1 includes one of a grating and a filter; the comb narrowband filter 21-2 includes one of a microring resonator (MRR), a Fabry-Perot resonator (FP resonator) and a grating Fabry-Perot resonator (grating FP resonator).

[0119] According to an embodiment of the present disclosure, the tuning component 22 includes a first phase shifter PS1, and the step S14 includes: adjusting the frequencies of the multiple longitudinal modes by the first phase shifter PS1 so that any longitudinal mode among the multiple longitudinal modes changes periodically and continuously around its center frequency.

[0120] According to an embodiment of the present disclosure, the first phase shifter PS1 includes a lithium niobate phase shifter.

[0121] According to an embodiment of the present disclosure, wherein the tuning component includes an injection current adjustment unit CS, the step S14 includes: changing the injection current of the laser 100 by the injection current adjustment unit CS to adjust the frequencies of the multiple longitudinal modes so that any longitudinal mode among the multiple longitudinal modes changes periodically and continuously near its center frequency.

[0122] According to an embodiment of the present disclosure, the step S14 includes: according to the variation period T' of the light intensity of the output laser, feedback-adjusting the working parameters of the laser 100 so that the frequency of the output laser is maintained within the preset frequency range, specifically including: when the variation period T' of the light intensity does not satisfy a first preset relationship with the preset frequency modulation period T, feedback-adjusting the working parameters of the laser 100 so that the frequency of the output laser is maintained within the preset frequency range.

[0123] According to an embodiment of the present disclosure, the first preset relationship includes: the variation period T' of the light intensity is half of the preset frequency modulation period T.

[0124] According to an embodiment of the present disclosure, the step S14 further includes: feedback-adjusting the operating parameters of the laser 100 according to the first-order frequency intensity and the second-order frequency intensity of the light intensity of the output laser, so that the frequency of the output laser remains within the preset frequency range, specifically including: when the first-order frequency intensity and the second-order frequency intensity of the light intensity do not satisfy the second preset relationship, feedback-adjusting the operating parameters of the laser 100, so that the frequency of the output laser remains within the preset frequency range.

[0125] According to an embodiment of the present disclosure, the second preset relationship includes: the first-order frequency intensity of the light intensity is less than the second-order frequency intensity.

[0126] According to an embodiment of the present disclosure, a second phase shifter PS2 is provided in the comb-shaped narrowband filter 21-2, and the step S14 includes: adjusting the resonant frequency of the comb-shaped narrowband filter 21-2 by the second phase shifter PS2 to adjust the passband range of the comb-shaped narrowband filter 21-2.

[0127] According to an embodiment of the present disclosure, the second phase shifter PS2 includes one or more of a lithium niobate phase shifter, a thermo-optical phase shifter, an electro-optical phase shifter, and a piezoelectric ceramic.

[0128] According to an embodiment of the present disclosure, the resonant cavity 30 further includes an oblique waveguide OW, and the oblique waveguide OW is disposed at an interface of the external cavity 20 close to the light source 10 to reduce reflection of light at the interface.

[0129] According to an embodiment of the present disclosure, the light source 10 includes a semiconductor amplifier SOA.

[0130] In addition, the present disclosure also relates to a laser radar 300, Fig.16 A schematic diagram of a laser radar 300 according to an embodiment of the present disclosure is shown. Fig.16 As shown, the laser radar 300 includes a transmitting device 310, a spectrometer 320, a mixing device 330, a detection device 340 and a processing device 350. The transmitting device 310 includes the laser 100 as described above, configured to transmit a laser beam L; the spectrometer 320 is configured to split the laser beam L into a detection light L1 and a local oscillator light L2, and the detection light L1 is emitted to the outside of the laser radar 300; the mixing device 330 is configured to receive the echo light L1' and the local oscillator light L2 reflected by the detection light L1 on the obstacle OB, and output a beat signal L3; the detection device 340 is configured to receive the beat signal L3; the processing device 350 is coupled to the detection device 340, and is configured to calculate obstacle information according to the beat signal L3.

[0131] In some embodiments of the present disclosure, the laser radar 300 may execute the control method 200 as described above.

[0132] In summary, the linear frequency sweeping laser, control method and laser radar of the present invention are introduced in detail. The laser of the present invention is an external cavity laser with a frequency modulation function, which can be used for FMCW laser radar, and the laser of the present invention can work based on a feedback mechanism. According to the light intensity of the output laser, the working parameters of the laser are adjusted by feedback to keep the frequency of the output laser within a preset frequency range.

[0133] Furthermore, the laser disclosed in the present invention can feedback-adjust the operating parameters of the laser according to the variation period of the light intensity of the output laser, and / or according to the first-order frequency intensity and the second-order frequency intensity of the output laser, so that the center frequency of the selected longitudinal mode matches the peak value of the bandpass filter, so that the frequency of the output laser is maintained within a preset frequency range.

[0134] Furthermore, the laser disclosed in the present invention can modulate the frequencies of multiple longitudinal modes through a tuning component, so that the frequency of the output laser changes periodically and continuously. The tuning component includes a lithium niobate phase shifter, thereby achieving rapid frequency modulation.

[0135] Furthermore, the laser disclosed in the present invention can effectively reduce or even avoid the real-time optical phase-locked loop by introducing a pre-distortion signal into the voltage signal of the first phase shifter and / or the second phase shifter, reduce nonlinearity, reduce cost and technical complexity, and facilitate the output laser to present a better linear frequency sweeping effect.

[0136] Furthermore, the laser disclosed in the present invention utilizes the periodic variation law of the output laser for feedback modulation, that is, utilizes the AC signal of the output laser for feedback modulation. Compared with directly utilizing the power of the output laser for modulation, it has a higher signal-to-noise ratio and is more conducive to matching the center frequency of the selected longitudinal mode with the peak value of the bandpass filter.

[0137] Furthermore, in the laser disclosed in the present invention, the broadband filter includes a grating, and the comb-shaped narrowband filter includes a microring resonant cavity, which can reduce the difficulty of bandwidth matching and facilitate the matching of the center frequency of the longitudinal mode with the peak of the bandpass filter, thereby reducing or even eliminating the risk of mode hopping and enabling the laser to operate stably.

[0138] The laser disclosed in the present invention can be frequency modulated and can achieve single-mode stable output. It has better detection performance such as wide wavelength tuning range, narrow line width, low loss, high side mode suppression ratio, long detection distance, and high integration, and is suitable for FMCW laser radar.

[0139] The present disclosure also provides a computer-readable storage medium, including computer-executable instructions stored thereon, and when the executable instructions are executed by a processor, the control method 200 of the laser radar 300 as described above is implemented.

[0140] In some embodiments, a computer-readable storage medium may be any tangible medium containing or storing a program, which may be used by an instruction execution system, device, or device or used in combination therewith. The computer-readable storage medium may be any combination of one or more computer-readable media. The computer-readable storage medium may be, for example, but not limited to, an electrical, magnetic, optical, or semiconductor form or device, and more specific examples (a non-exhaustive list) include: an electrical connection with one or more wires, a portable computer hard disk, a hard disk, a random access memory (RAM), a non-volatile random access memory (NVRAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above.

[0141] In addition, the present disclosure also provides a computer device (not shown), including a memory and a processor, wherein the memory is configured to store computer executable instructions, and the executable instructions implement the control method 200 as described above when executed by the processor.

[0142] In some embodiments, the processor / processing device may include a central processing unit (CPU), and may also include other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The present disclosure does not limit this and it depends on the specific circumstances.

[0143] It should be noted that although several modules of the laser radar are mentioned in the above detailed description, this division is not mandatory. In fact, according to the embodiments of the present disclosure, the features and functions of two or more modules described above can be implemented in one module. Conversely, the features and functions of one module described above can be further divided into multiple modules to be embodied.

[0144] It should be noted that this specification provides method operation steps as described in the embodiments or schematic diagrams, but more or fewer operation steps may be included based on conventional or non-creative labor. The order of steps listed in the embodiments is only one way of executing the order of many steps and does not represent the only execution order. When the actual system or device product is executed, it can be executed in the order or in parallel according to the method shown in the embodiments or flowcharts.

[0145] Finally, it should be noted that the above is only an exemplary embodiment of the present disclosure and is not intended to limit the present disclosure. Although the present disclosure is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A linear frequency-sweeping laser, the laser comprising: A light source and an external cavity coupled to the light source, wherein the light source and the external cavity form a resonant cavity having a plurality of longitudinal modes; Wherein, the external cavity includes a bandpass filter and a tuning component; The bandpass filter is configured to: select light corresponding to one of the longitudinal modes from the plurality of longitudinal modes and output it from the laser to form an output laser, wherein the frequency of the output laser matches the frequency of the selected longitudinal mode; The tuning component is configured to: make the frequency of the output laser change periodically and continuously by adjusting the multiple longitudinal modes; The laser is configured to feedback-adjust the working parameters of the laser according to the light intensity of the output laser so that the frequency of the output laser is maintained within a preset frequency range. 2 . The laser according to claim 1 , wherein the operating parameters include the frequencies of the plurality of longitudinal modes and / or the passband range of the bandpass filter.

3. The laser according to claim 2 is configured to: feedback-adjust the passband range of the bandpass filter according to the light intensity of the output laser, and / or feedback-adjust the frequencies of the multiple longitudinal modes according to the light intensity of the output laser, so that the center frequency of the selected longitudinal mode matches the peak value of the bandpass filter, so that the frequency of the output laser is maintained within the preset frequency range.

4. The laser according to any one of claims 1 to 3, wherein the bandpass filter comprises a broadband filter and a comb-shaped narrowband filter.

5. The laser according to claim 4, wherein the broadband filter comprises one of a grating and a filter; and the comb narrowband filter comprises one of a microring resonator, a Fabry-Perot resonator and a grating Fabry-Perot resonator.

6. The laser according to any one of claims 1 to 3, wherein the tuning component comprises a first phase shifter, wherein the first phase shifter is configured to adjust the frequencies of the plurality of longitudinal modes so that any longitudinal mode of the plurality of longitudinal modes changes continuously and periodically around its center frequency.

7. The laser of claim 6, wherein the first phase shifter comprises a lithium niobate phase shifter.

8. The laser according to any one of claims 1-3, wherein the tuning component further comprises an injection current adjustment unit, wherein the injection current adjustment unit is configured to: change the injection current of the laser to adjust the frequencies of the multiple longitudinal modes so that any longitudinal mode among the multiple longitudinal modes changes periodically and continuously around its center frequency.

9. The laser according to any one of claims 1 to 3, wherein the laser is configured to: according to the variation period of the light intensity of the output laser, feedback adjust the operating parameters of the laser so that the frequency of the output laser is maintained within the preset frequency range, specifically comprising: When the variation period of the light intensity does not satisfy a first preset relationship with the preset frequency modulation period, the operating parameters of the laser are adjusted by feedback to keep the frequency of the output laser within the preset frequency range.

10. The laser according to claim 9, wherein the first preset relationship comprises: The variation period of the light intensity is half of the preset frequency modulation period.

11. The laser according to any one of claims 1 to 3, wherein the laser is further configured to: according to the first-order frequency intensity and the second-order frequency intensity of the light intensity of the output laser, feedback adjust the operating parameters of the laser so that the frequency of the output laser is maintained within the preset frequency range, specifically comprising: When the first-order frequency intensity and the second-order frequency intensity of the light intensity do not satisfy the second preset relationship, the operating parameters of the laser are adjusted by feedback to keep the frequency of the output laser within the preset frequency range.

12. The laser according to claim 11, wherein the second preset relationship comprises: The first-order frequency intensity of the light intensity is less than the second-order frequency intensity.

13. The laser according to claim 4, wherein a second phase shifter is provided in the comb-shaped narrowband filter, and the second phase shifter is configured to adjust the resonant frequency of the comb-shaped narrowband filter to adjust the passband range of the comb-shaped narrowband filter. 14 . The laser according to claim 13 , wherein the second phase shifter comprises one or more of a lithium niobate phase shifter, a thermo-optical phase shifter, an electro-optical phase shifter, and a piezoelectric ceramic.

15. The laser according to any one of claims 1 to 3, wherein the resonant cavity further comprises an oblique waveguide, wherein the oblique waveguide is disposed at an interface of the external cavity close to the light source to reduce reflection of light at the interface.

16. The laser of any one of claims 1-3, wherein the light source comprises a semiconductor gain device.

17. A control method for a linear frequency-sweeping laser, wherein the laser comprises a light source and an external cavity coupled to the light source, the light source and the external cavity forming a resonant cavity; the resonant cavity has a plurality of longitudinal modes; the external cavity comprises a bandpass filter and a tuning component; the control method comprises: S11: selecting light corresponding to one of the longitudinal modes from the plurality of longitudinal modes through the bandpass filter and outputting the light from the laser to form an output laser, wherein the frequency of the output laser matches the frequency of the selected longitudinal mode; S12: adjusting the multiple longitudinal modes by the tuning component so that the frequency of the output laser changes periodically and continuously; S13: collecting the light intensity of the output laser of the laser; and S14: According to the light intensity of the output laser of the laser, feedback is performed to adjust the working parameters of the laser so that the frequency of the output laser is maintained within a preset frequency range. 18 . The control method according to claim 17 , wherein the operating parameters include the frequencies of the plurality of longitudinal modes and / or the passband range of the bandpass filter.

19. The control method according to claim 18, wherein the step S14 comprises: The passband range of the bandpass filter is feedback-adjusted according to the light intensity of the output laser of the laser, and / or the frequencies of the multiple longitudinal modes are feedback-adjusted according to the light intensity of the output laser, so that the center frequency of the selected longitudinal mode matches the peak value of the bandpass filter, so that the frequency of the output laser is maintained within the preset frequency range.

20. The control method according to any one of claims 17 to 19, wherein the bandpass filter comprises a broadband filter and a comb-type narrowband filter.

21. The control method according to claim 20, wherein the broadband filter comprises one of a grating and a filter; and the comb narrowband filter comprises one of a microring resonant cavity, a Fabry-Perot resonant cavity and a grating Fabry-Perot resonant cavity.

22. The control method according to any one of claims 17 to 19, wherein the tuning component comprises a first phase shifter, and the step S14 comprises: The frequencies of the plurality of longitudinal modes are adjusted by the first phase shifter so that any longitudinal mode among the plurality of longitudinal modes changes periodically and continuously near its center frequency.

23. The control method of claim 22, wherein the first phase shifter comprises a lithium niobate phase shifter.

24. The control method according to any one of claims 17 to 19, wherein the tuning component comprises an injection current adjustment unit, and the step S14 comprises: The injection current of the laser is changed by the injection current adjustment unit to adjust the frequencies of the multiple longitudinal modes, so that any longitudinal mode among the multiple longitudinal modes changes periodically and continuously near its central frequency.

25. The control method according to any one of claims 17 to 19, wherein the step S14 comprises: According to the variation cycle of the light intensity of the output laser, feedback-adjusting the working parameters of the laser so that the frequency of the output laser is maintained within the preset frequency range, specifically including: when the variation cycle of the light intensity and the preset frequency modulation cycle do not satisfy a first preset relationship, feedback-adjusting the working parameters of the laser so that the frequency of the output laser is maintained within the preset frequency range.

26. The control method according to claim 25, wherein the first preset relationship comprises: The variation period of the light intensity is half of the preset frequency modulation period.

27. The control method according to any one of claims 17 to 19, wherein the step S14 further comprises: According to the first-order frequency intensity and the second-order frequency intensity of the light intensity of the output laser, the working parameters of the laser are feedback-adjusted so that the frequency of the output laser is maintained within the preset frequency range, specifically including: when the first-order frequency intensity and the second-order frequency intensity of the light intensity do not satisfy the second preset relationship, the working parameters of the laser are feedback-adjusted so that the frequency of the output laser is maintained within the preset frequency range.

28. The control method according to claim 27, wherein the second preset relationship comprises: The first-order frequency intensity of the light intensity is less than the second-order frequency intensity.

29. The control method according to claim 20, wherein a second phase shifter is provided in the comb-shaped narrowband filter, and the step S14 comprises: The resonant frequency of the comb-type narrowband filter is adjusted by the second phase shifter to adjust the passband range of the comb-type narrowband filter. 30 . The control method according to claim 29 , wherein the second phase shifter comprises one or more of a lithium niobate phase shifter, a thermo-optical phase shifter, an electro-optical phase shifter, and a piezoelectric ceramic.

31. The control method according to any one of claims 17 to 19, wherein the resonant cavity further comprises an oblique waveguide, and the oblique waveguide is arranged at an interface of the external cavity close to the light source to reduce reflection of light at the interface.

32. The control method according to any one of claims 17 to 19, wherein the light source comprises a semiconductor gain device.

33. A laser radar, comprising: An emitting device, comprising a laser according to any one of claims 1 to 16, configured to emit a laser beam; A spectroscopic device configured to split the laser beam into a detection light and a local oscillator light, wherein the detection light is emitted to the outside of the laser radar; A frequency mixing device configured to receive the echo light reflected by the detection light on the obstacle and the local oscillation light, and output a beat frequency signal; a detection device configured to receive the beat frequency signal; and A processing device is coupled to the detection device and is configured to calculate obstacle information based on the beat frequency signal.

34. The laser radar according to claim 33 can execute the control method according to any one of claims 17-32.

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