Linearity Correction System for Dual Micro-Ring Resonator Semiconductor Lasers

Abstract

This invention discloses a linearity correction system for a dual-microring resonant cavity semiconductor laser, belonging to the field of laser correction. It corrects the nonlinear frequency signal output by the dual-microring resonant cavity semiconductor laser driven by a standard triangular wave modulation signal to obtain a pre-distortion waveform. This waveform is then amplified proportionally and output as three driving signals, which are applied to the dual-microring modulator and phase shifter integrated within the dual-microring resonant cavity semiconductor laser. The output nonlinear frequency signal is then corrected again. Through multiple rounds of correction, the dual-microring resonant cavity semiconductor laser outputs a frequency-modulated linear continuous triangular wave frequency signal, thus completing the linearity correction of the dual-microring resonant cavity semiconductor laser. This system can be used for high-precision laser ranging and effectively solves the frequency modulation nonlinearity problem of dual-microring resonant cavity semiconductor lasers under wide frequency sweeps, reducing measurement errors caused by the laser itself.

Description

Technical Field

[0001] This invention relates to the field of laser correction technology, and in particular to a linearity correction system for a dual-micro-ring resonant cavity semiconductor laser. Background Technology

[0002] Frequency Modulated Continuous Wave (FMCW) lidar employs coherent detection rather than direct detection. It detects the beat frequency of the transmitted and echo signals by frequency modulation of the laser in the time domain, simultaneously detecting the target's range and velocity. Compared to traditional Time-of-Flight (TOF) lidar, FMCW lidar offers advantages such as stronger resistance to environmental interference and the ability to achieve longer-range detection, attracting widespread attention from industry and academia.

[0003] The silicon-based integration of lidar is an inevitable trend for the future. Therefore, frequency-modulated continuous-wave (FMW) lasers in lidar light sources will inevitably continue to advance towards silicon photonic integration. The miniaturization and integration of lidar will inevitably require integrated micro-lasers. Dual-microring resonant cavity semiconductor lasers are a type of laser manufactured using silicon photonic integration technology. They are characterized by their small size and wide tunable range, and their tuning is mainly controlled by micro-ring modulators and phase shifters. Integrating dual-microring resonant cavity semiconductor lasers manufactured using silicon photonic integration technology with the entire FMW system will significantly reduce the cost and size of existing lidar systems. However, the linear frequency-modulated signal generated by an FMW lidar system is usually not perfectly linear. This causes the nonlinear signal generated by the FMW to severely broaden the spectral bandwidth of the beat frequency signal, affecting the final ranging accuracy.

[0004] If a laser has nonlinear effects, it will lead to a reduction in the overall accuracy and resolution of the lidar. For dual-micro-ring resonator type semiconductor lasers used in FMCW lidar, even if a linear drive is applied, its output is not linear, but has a nonlinear frequency output. Therefore, how to solve the inherent nonlinearity of dual-micro-ring resonator type semiconductor lasers is the focus of current industry research. Summary of the Invention

[0005] This invention provides a linearity correction system for a dual-micro-ring resonant cavity semiconductor laser, which solves the problems in the prior art where the spectrum measured by FMCW lidar is difficult to distinguish and the target position cannot be identified due to the nonlinearity of the laser when the dual-micro-ring resonant cavity semiconductor laser is used for a wide frequency sweep.

[0006] This invention provides a linearity correction system for a dual-microring resonator semiconductor laser. The dual-microring resonator semiconductor laser includes a first microring resonator, a second microring resonator, and a phase shifter. The linearity correction system includes:

[0007] A temperature controller, connected to a dual-microring resonant cavity semiconductor laser, is used to maintain a constant temperature of the dual-microring resonant cavity semiconductor laser so that the output wavelength of the dual-microring resonant cavity semiconductor laser does not skip modes;

[0008] The optical transmission path has its input end connected to the dual-micro-ring resonant cavity semiconductor laser to generate two optical signals. The first optical signal is sent to the lidar transmitter, and the second optical signal is sent to the non-equidistant MZI (Mach-Zehnder Interferometer) structure.

[0009] The non-equidistant MZI structure is used to mix the received optical signal after different delays to generate a beat frequency optical signal.

[0010] A balanced photodetector, wherein the input end of the balanced photodetector is connected to the output end of the non-equidistant MZI structure, is used to convert the beat-frequency optical signal into a beat-frequency electrical signal.

[0011] The data processing module is used to perform analog-to-digital conversion on the beat frequency electrical signal, calculate the frequency and phase of the beat frequency optical signal, calculate the chirp frequency and linearity of the output optical signal of the dual micro-ring resonant cavity semiconductor laser based on the frequency and phase, calculate the desired linear frequency modulated continuous wave frequency line, calculate the error value between the ideal frequency modulation and the actual frequency modulation curve, and superimpose the error value with the actual frequency modulation curve after scaling within a preset range to generate a predistorted waveform.

[0012] A proportional amplifier circuit is included, with its input connected to the output of the data processing module. Its three outputs are connected to the first microring resonator, the second microring resonator, and the phase shifter of the dual-microring resonant cavity semiconductor laser, respectively. This circuit amplifies the pre-distorted waveform according to a set ratio, generating three output voltages. These three output voltages are then applied to the first microring resonator, the second microring resonator, and the phase shifter of the dual-microring resonant cavity semiconductor laser, respectively. This causes the first and second microring resonators to form a filter structure with a vernier effect. By adjusting the phase shifter, the first microring resonator, and the second microring resonator, alignment with the resonant wavelength exhibiting the vernier effect is achieved, enabling mode selection and generating a frequency-modulated linear continuous triangular wave signal.

[0013] In one embodiment of the present invention, the optical transmission path includes:

[0014] An optical isolator, wherein the input end of the optical isolator is connected to the output end of the dual-micro-ring resonant cavity semiconductor laser;

[0015] The first optical beam splitter has its input end connected to the output end of the optical isolator. The first output end is the laser radar transmitter. The first optical beam splitter is used to split the laser emitted by the dual micro-ring resonant cavity semiconductor laser.

[0016] In one embodiment of the present invention, the non-equilateral MZI structure includes:

[0017] The second optical beam splitter receives the second optical signal from the first optical beam splitter and is used to split the received optical signal into two optical signals.

[0018] The first optical attenuator receives the first optical signal from the second optical beam splitter at its input terminal.

[0019] The delay line receives the second optical signal from the second optical beam splitter at its input end and is used to apply a delay to the second optical signal.

[0020] The second optical attenuator has its input terminal connected to the output terminal of the delay line, and is used to receive the delayed second optical signal.

[0021] An optical mixer is provided, wherein the first input terminal of the optical mixer is connected to the output terminal of the first optical attenuator, the second input terminal is connected to the output terminal of the second optical attenuator, and the output terminal is connected to the input terminal of the balanced photodetector. By jointly adjusting the first optical attenuator and the second optical attenuator, the light intensity of the two output lights is matched, and the two optical signals are mixed to generate a beat frequency optical signal.

[0022] In one embodiment of the present invention, the data processing module includes:

[0023] An analog-to-digital converter, the input of which is connected to the output of the balanced photodetector, is used to convert the beat frequency electrical signal into a digital signal;

[0024] A data processing unit, whose input is connected to the output of the analog-to-digital converter, performs a Hilbert transform on the beat frequency digital signal to obtain a transformed complex signal. Based on the characteristic of the Hilbert transform having a 90-degree phase shift filter, the phase change curve of the beat frequency digital signal is obtained using the quotient of the imaginary and real parts of the complex signal. Using the constant proportional relationship between the phase change curve and the original chirped frequency curve of the frequency-modulated continuous wave, the chirped frequency curve of the dual-microring resonant cavity semiconductor laser is calculated. The corresponding desired linear frequency-modulated continuous wave frequency line is calculated using the chirped frequency curve. The frequency modulation nonlinearity of the emitted signal of the dual-microring resonant cavity semiconductor laser is calculated based on the relationship between the obtained actual frequency modulation curve and the ideal linear frequency-modulated continuous wave frequency. The error value between the ideal frequency modulation and the actual frequency modulation curve is calculated. The error value, after being scaled within a preset range, is superimposed on the actual frequency modulation curve to generate the pre-distortion waveform.

[0025] A digital-to-analog converter (DAC) is provided, with its input terminal connected to the output terminal of the data processing unit and its output terminal connected to the input terminal of the proportional amplifier circuit. The DAC is used to convert the digital signal from the data processing unit into an electrical signal and output it to the proportional amplifier circuit.

[0026] The linearity correction system for a dual-microring resonant cavity semiconductor laser, as described in this invention, integrates a dual-microring modulator and a phase shifter within the laser. In the initial stage, the laser is driven by a standard triangular wave modulation signal. Due to the nonlinearity of the laser's output frequency signal, a pre-distortion waveform is obtained by correcting this nonlinear frequency signal. This pre-distortion waveform is then amplified proportionally and output as three driving signals, which are applied to the integrated dual-microring modulator and phase shifter within the laser. This process further corrects the nonlinear frequency signal output by the laser. Through multiple rounds of correction, the laser outputs a frequency-modulated linear continuous triangular wave frequency signal, thus completing the linearity correction. This system can be used for high-precision laser ranging and effectively solves the frequency modulation nonlinearity problem inherent in dual-microring resonant cavity semiconductor lasers under wide-range frequency sweeps, reducing measurement errors caused by the laser itself.

[0027] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0028] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0029] Figure 1 This is a schematic diagram illustrating the basic principle of frequency-modulated linear continuous wave lidar ranging according to an embodiment of the present invention.

[0030] Figure 2 A comparison diagram of frequency-modulated nonlinear continuous wave lidar ranging provided according to an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of a linearity correction system for a dual-micro-ring resonator semiconductor laser according to an embodiment of the present invention.

[0032] Figure 4 A proportional amplifier circuit diagram provided according to an embodiment of the present invention;

[0033] Figure 5 This is a structural diagram of a linearity correction system for a dual-micro-ring resonator semiconductor laser according to an embodiment of the present invention;

[0034] Figure 6 A flowchart of a nonlinear correction method provided according to an embodiment of the present invention. Detailed Implementation

[0035] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0036] like Figure 1 (a) is a frequency-modulated triangular wave waveform, which shows the standard frequency-time relationship as a triangular wave changes over time; Figure 1 (b) is the time-domain amplitude plot of the frequency modulation signal, showing the relationship between the amplitude of the frequency modulation signal and time; and Figure 1 (c) shows the frequency-modulated triangular wave waveforms and corresponding beat frequency signals before and after the time delay, illustrating the frequency-time relationship before and after the time delay, as well as the beat frequency signal-time relationship after the self-heterodyne. The beat frequency signal f is generated after the local oscillator light and the echo signal interfere in the coupler and are converted into an electrical signal by a balanced photodetector. beat for:

[0037] f beat (t)=γτ

[0038] Where γ is the modulation slope of the frequency-modulated triangular wave, and τ is the delay time of the echo signal, calculated from the optical path length and velocity of the echo signal. This can be achieved by... Figure 1 It can be seen that under linear frequency modulation, the output beat frequency signal is a constant over a period of time, and the ramp segment of the beat frequency signal is mainly caused by the sudden turning point of the linear frequency modulation triangular wave near the extreme point.

[0039] like Figure 2 The image shows a comparison of lidar ranging methods using nonlinear frequency-modulated continuous waves. Figure 2 (a) is a graph showing the time-frequency relationship between the local signal and the received signal after the delay. Figure 2 Figure (b) shows the time-frequency relationship between the local signal and the received signal after beat frequency modulation. It can be seen that the modulation slope is nonlinear, resulting in instability and non-constancy of the beat frequency signal, which significantly impacts measurement accuracy. To address this problem, this invention proposes a linearity correction system for a dual-micro-ring resonant cavity semiconductor laser.

[0040] Specifically, Figure 3 This is a schematic diagram of a linearity correction system for a dual-micro-ring resonant cavity semiconductor laser according to an embodiment of the present invention.

[0041] The dual-microring resonator semiconductor laser 100 contains three thermally tunable modules: a first microring resonator 101, a second microring resonator 102, and a phase shifter 103. When the dual-microring resonator semiconductor laser 100 receives a driving voltage, the three internal thermally tunable modules heat up and generate optical signals based on the thermo-optical effect of the materials. The two microring resonators form a filter structure with a vernier effect, enabling a wide range of tunable laser output. By adjusting the phase shifter and the two microring resonators, alignment with the resonant wavelength exhibiting the vernier effect is achieved, mode selection is realized, and a continuously tunable output wavelength is generated, thereby enabling the joint modulation of the optical signal.

[0042] like Figure 3 As shown, the linearity correction system 10 for a dual-micro-ring resonator semiconductor laser includes: a temperature controller 200, an emission optical path 300, a non-equilateral MZI structure 400, a balanced photodetector 500, a data processing module 600, and a proportional amplifier circuit 700.

[0043] Temperature controller 200 is connected to dual microring resonator semiconductor laser 100 and is used to keep the temperature of dual microring resonator semiconductor laser 100 constant so that the output wavelength of dual microring resonator semiconductor laser 100 does not skip modes.

[0044] Specifically, the temperature controller 200 can control the operating environment temperature of the dual-micro-ring resonant cavity semiconductor laser 100, stabilizing the laser's temperature changes. By changing the temperature of the temperature controller 200 integrated on the surface of the dual-micro-ring resonant cavity semiconductor laser 100, the output wavelength of the laser can be effectively adjusted. Setting a constant temperature for the temperature controller 200 can effectively prevent mode hopping caused by internal temperature changes during power-on tuning.

[0045] The transmitting optical path 300 is connected to the dual micro-ring resonant cavity semiconductor laser 100 to generate two optical signals. The first optical signal is sent to the lidar transmitter, and the second optical signal is sent to the non-equidistant MZI structure 400.

[0046] The non-equilateral MZI structure 400 is used to mix the received optical signal after different delays to generate a beat frequency optical signal.

[0047] The input terminal of the balanced photodetector 500 is connected to the output terminal of the non-equidistant MZI structure 400, and is used to convert the beat frequency optical signal into a beat frequency electrical signal.

[0048] The data processing module 600 is used to calculate the frequency and phase of the optical signal after frequency beating by performing analog-to-digital conversion on the electrical signal after frequency beating, calculate the chirp frequency and linearity of the output optical signal of the dual micro-ring resonant cavity semiconductor laser based on the frequency and phase, and then calculate the desired linear frequency modulated continuous wave frequency line, calculate the error value between the ideal frequency modulation and the actual frequency modulation curve, and superimpose the error value with the actual frequency modulation curve after scaling within a preset range to generate a predistorted waveform.

[0049] The data processing module 600 includes a pre-distortion processing module, which can perform data calculations and processing.

[0050] A proportional amplifier circuit 700 has its input terminal connected to the output terminal of the data processing module 600. Its three output terminals are respectively connected to the first microring resonator 101, the second microring resonator 102, and the phase shifter 103 of the dual-microring resonant cavity semiconductor laser 100. This circuit amplifies the pre-distorted waveform according to a set ratio, obtaining three output voltages. These three output voltages are then applied to the first microring resonator, the second microring resonator, and the phase shifter of the dual-microring resonant cavity semiconductor laser, respectively. This causes the first microring resonator 101 and the second microring resonator 102 to form a filter structure with a vernier effect. By adjusting the phase shifter 103, the first microring resonator 101, and the second microring resonator 102, alignment with the resonant wavelength exhibiting the vernier effect is achieved, enabling mode selection and generating a frequency-modulated linear continuous triangular wave frequency signal.

[0051] The proportional amplifier circuit 700 includes a single analog voltage signal input from the data processing module 600 and three proportionally adjustable output signals, which are then output to the input of a dual-micro-ring resonator semiconductor laser, consisting of two micro-ring resonators and a phase shifter. The proportional amplifier circuit provides drive voltages to the three thermally tuned devices of the laser. Under the control of the external drive voltage, the laser, through the combined tuning of the internal thermally tuned devices, completes the output of the optical signal.

[0052] The tunable wide-range wavelength output of the dual-microring resonator semiconductor laser is mainly controlled by internally integrated thermally tuned components, namely the first microring resonator, the second microring resonator, and the phase shifter. Each of these components can individually or jointly achieve tunable continuous output of the laser's wavelength. By designing a proportional amplifier circuit, the dual microring resonators and phase shifter of the laser are driven to have different applied voltage ratios, achieving a wide-range tunable wavelength output with narrow linewidth and no mode-hopping phenomenon.

[0053] Furthermore, such as Figure 4 The diagram shows the circuit diagram of a proportional amplifier circuit. This circuit can achieve single-channel voltage input and proportional output of multiple voltages. The proportional amplifier circuit receives the voltage control signal from the previous stage, adjusts the value of the adjustable output resistor, and controls the proportional relationship of the three output voltages. These voltages are then applied to the first micro-ring resonator, the second micro-ring resonator, and the phase shifter of the laser, respectively, driving the laser to generate an optical signal. Furthermore, adjusting the value of the adjustable output resistor and controlling the proportional relationship of the three output voltages is to ensure that the thermally tuned devices inside the laser, when driven by voltage, can collectively generate a continuously tunable frequency-modulated signal without mode-hopping. The voltage proportional relationship of these thermally tuned devices can be obtained through actual experimental testing.

[0054] The linearity correction system for the dual-microring resonant cavity semiconductor laser of this invention amplifies the corrected pre-distortion waveform through a proportional amplifier circuit to obtain three driving signals. These three driving signals are then used to power the dual-microring resonant cavity semiconductor laser, achieving a frequency-modulated linear continuous triangular wave frequency signal at the laser output. Specifically, a temperature controller is used to stabilize the laser's output wavelength to prevent mode hopping. After passing through the emission optical path, the output light is split into two beams: one beam is used for the laser radar's transmitter, and the other beam passes through a non-equidistant MZI structure. In the non-equilateral MZI structure, the optical signal received by the second optical beam splitter is mixed after different delays to generate a beat-frequency optical signal. The beat-frequency optical signal is then converted into a beat-frequency electrical signal by a balanced photodetector, processed by the data processing module, and re-output to generate a predistorted waveform for the proportional amplifier circuit. After amplification of the predistorted waveform by the proportional amplifier circuit, three driving signals are obtained to drive the dual microring resonator and phase shifter of the dual microring resonator semiconductor laser. The two microring modulators form a filter structure with a vernier effect, which can obtain a wide range of tunable laser output. By adjusting the phase shifter and the two microring modulators, the laser can be aligned with the resonant wavelength with the vernier effect, thereby achieving mode selection and generating a frequency-modulated linear continuous triangular wave frequency signal, realizing nonlinear correction.

[0055] like Figure 5 As shown, in a specific embodiment of the present invention, the optical transmission path 300 includes:

[0056] Optical isolator 301, the input terminal of which is connected to the output terminal of dual micro-ring resonant cavity semiconductor laser 200;

[0057] The first optical beam splitter 302 has its input end connected to the output end of the optical isolator 301. The first output end is the laser radar transmitter. The first optical beam splitter 302 is used to split the laser emitted by the dual micro-ring resonant cavity semiconductor laser 200.

[0058] like Figure 5 As shown, in a specific embodiment of the present invention, the non-equilateral MZI structure 400 includes:

[0059] The second optical beam splitter 401 receives the second optical signal from the first optical beam splitter 302 and is used to split the received optical signal into two optical signals.

[0060] The first optical attenuator 402 receives the first optical signal from the second optical beam splitter 401 at its input end.

[0061] Delay line 403, the input end of delay line 403 receives the second optical signal from the second optical beam splitter 401, and is used to apply a delay to the second optical signal;

[0062] The second optical attenuator 404 has its input terminal connected to the output terminal of the delay line 403, and is used to receive the delayed second optical signal.

[0063] Optical mixer 405 has its first input terminal connected to the output terminal of the first optical attenuator 402, its second input terminal connected to the output terminal of the second optical attenuator 404, and its output terminal connected to the input terminal of the balanced photodetector 500. By jointly adjusting the first optical attenuator 402 and the second optical attenuator 404, the light intensity of the two output lights is matched, and the two optical signals are mixed to generate a beat frequency optical signal.

[0064] Specifically, the non-equilateral MZI structure receives the optical signal emitted by the laser and generates a coherent optical signal. The input light is split into two by a second optical beam splitter. One beam passes through a first optical attenuator and is output, while the other beam passes through a delay line and a second optical attenuator before being output. By jointly adjusting the first and second attenuators, the output light intensities of the two beams are matched. Then, the two beams are combined into a single output beam after passing through an optical mixer to form a beat frequency optical signal, which is then sent to a balanced photodetector.

[0065] like Figure 5 As shown, in a specific embodiment of the present invention, the data processing module 600 includes:

[0066] Analog-to-digital converter 601, whose input terminal is connected to the output terminal of balanced photodetector 500, is used to convert the beat frequency electrical signal into a digital signal;

[0067] The data processing unit 602, whose input terminal is connected to the output terminal of the analog-to-digital converter 601, is used to perform Hilbert transform on the beat frequency digital signal to obtain the transformed complex signal. Based on the characteristic of the Hilbert transform having a 90-degree phase shift filter, the phase change curve of the beat frequency digital signal is obtained by using the quotient of the imaginary part and the real part of the complex signal. Using the constant proportional relationship between the phase change curve and the original chirped frequency curve of the frequency-modulated continuous wave, the chirped frequency curve of the dual-micro-ring resonant cavity semiconductor laser is calculated based on the phase change curve. The corresponding desired linear frequency-modulated continuous wave frequency line is calculated through the chirped frequency curve. The frequency modulation nonlinearity of the emitted signal of the dual-micro-ring resonant cavity semiconductor laser is calculated based on the relationship between the obtained actual frequency modulation curve and the ideal linear frequency-modulated continuous wave frequency. The error value between the ideal frequency modulation and the actual frequency modulation curve is calculated. After scaling the error value within a preset range, it is superimposed on the actual frequency modulation curve to generate a predistorted waveform.

[0068] The digital-to-analog converter 603 has its input terminal connected to the output terminal of the data processing unit 602 and its output terminal connected to the input terminal of the proportional amplifier circuit 700. It is used to convert the digital signal of the data processing unit 602 into an electrical signal and output it to the proportional amplifier circuit 700.

[0069] like Figure 6 The diagram illustrates the processing flow of the data processing module in an embodiment of the present invention.

[0070] S100: Perform a Hilbert transform on the obtained beat frequency signal to obtain the transformed complex signal;

[0071] S101: The phase curve of the beat frequency signal is calculated based on the complex signal above, which reflects the original frequency change of the laser. The two have a certain proportionality constant. The Hilbert transform and phase curve of the beat frequency signal within a selected complete period are calculated, and the frequency modulation linearity is calculated through the phase curve.

[0072] S102: Based on the phase curve, calculate the expression form of the desired ideal linear frequency modulated continuous wave signal, obtain the curve of the actual frequency modulated continuous wave signal output frequency of the laser changing with time and the relationship between the frequency of the ideal linear frequency modulated continuous wave and time, and calculate the error value between the two.

[0073] S103: Determine whether to continue nonlinear correction based on the relationship between the desired frequency modulation nonlinearity and the assumed threshold. If the set threshold requirement is not met, the error value is scaled accordingly and superimposed on the actual frequency modulation continuous wave drive signal to complete the nonlinear correction compensation of the original drive signal. If the set threshold requirement is met, the nonlinear correction of the laser ends.

[0074] S104: Using an iterative update method, repeat steps S100 to S103 until a predistortion drive waveform that meets the set threshold requirements is obtained.

[0075] The linearity correction system for a dual-microring resonator semiconductor laser proposed in this invention, in the initial stage, drives the dual-microring resonator semiconductor laser with a standard triangular wave modulation signal. Due to the nonlinear output frequency signal of the dual-microring resonator semiconductor laser, a pre-distortion waveform is obtained by correcting the nonlinear frequency signal output by the dual-microring resonator semiconductor laser. The pre-distortion waveform is then amplified proportionally and output as three driving signals, which are applied to the dual-microring modulator and phase shifter integrated inside the dual-microring resonator semiconductor laser for driving. The nonlinear frequency signal output by the dual-microring resonator semiconductor laser is then corrected again. Through multiple rounds of correction, the dual-microring resonator semiconductor laser outputs a frequency-modulated linear continuous triangular wave frequency signal, thus completing the linearity correction of the dual-microring resonator semiconductor laser. This invention can be used for high-precision laser ranging and can effectively solve the frequency modulation nonlinearity problem of dual-microring resonator semiconductor lasers under wide-range frequency sweeps, reducing the measurement error caused by the laser itself.

[0076] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0077] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "N" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0078] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or N executable instructions for implementing custom logic functions or processes, and the scope of preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

Claims

1. A linearity correction system for a dual-microring resonator semiconductor laser, wherein the dual-microring resonator semiconductor laser comprises a first microring resonator, a second microring resonator, and a phase shifter, characterized in that, include: A temperature controller, connected to a dual-microring resonant cavity semiconductor laser, is used to maintain a constant temperature of the dual-microring resonant cavity semiconductor laser so that the output wavelength of the dual-microring resonant cavity semiconductor laser does not skip modes; The optical transmission path has its input end connected to the dual-micro-ring resonant cavity semiconductor laser to generate two optical signals. The first optical signal is sent to the lidar transmitter, and the second optical signal is sent to the non-equidistant MZI structure. The non-equidistant MZI structure is used to mix the received optical signal after different delays to generate a beat frequency optical signal. A balanced photodetector, wherein the input end of the balanced photodetector is connected to the output end of the non-equidistant MZI structure, is used to convert the beat-frequency optical signal into a beat-frequency electrical signal. The data processing module is used to perform analog-to-digital conversion on the beat frequency electrical signal, calculate the frequency and phase of the beat frequency optical signal, calculate the chirp frequency and linearity of the output optical signal of the dual micro-ring resonant cavity semiconductor laser based on the frequency and phase, calculate the desired linear frequency modulated continuous wave frequency line, calculate the error value between the ideal frequency modulation and the actual frequency modulation curve, and superimpose the error value with the actual frequency modulation curve after scaling within a preset range to generate a predistorted waveform. A proportional amplifier circuit is included, with its input connected to the output of the data processing module. Its three outputs are connected to the first microring resonator, the second microring resonator, and the phase shifter of the dual-microring resonant cavity semiconductor laser, respectively. This circuit amplifies the pre-distorted waveform according to a set ratio, generating three output voltages. These three output voltages are then applied to the first microring resonator, the second microring resonator, and the phase shifter of the dual-microring resonant cavity semiconductor laser, respectively. This causes the first and second microring resonators to form a filter structure with a vernier effect. By adjusting the phase shifter, the first microring resonator, and the second microring resonator, alignment with the resonant wavelength exhibiting the vernier effect is achieved, enabling mode selection and generating a frequency-modulated linear continuous triangular wave signal.

2. The linearity correction system for a dual-micro-ring resonator semiconductor laser according to claim 1, characterized in that, The optical transmission path includes: An optical isolator, wherein the input end of the optical isolator is connected to the output end of the dual-micro-ring resonant cavity semiconductor laser; The first optical beam splitter has its input end connected to the output end of the optical isolator, and its first output end is the laser radar transmitter. The first optical beam splitter is used to split the laser emitted by the dual micro-ring resonant cavity semiconductor laser.

3. The linearity correction system for a dual-micro-ring resonator semiconductor laser according to claim 2, characterized in that, The non-equilateral MZI structure includes: The second optical beam splitter receives the second optical signal from the first optical beam splitter and is used to split the received optical signal into two optical signals. The first optical attenuator receives the first optical signal from the second optical beam splitter at its input terminal. The delay line receives the second optical signal from the second optical beam splitter at its input end and is used to apply a delay to the second optical signal. The second optical attenuator has its input terminal connected to the output terminal of the delay line and is used to receive the delayed second optical signal. An optical mixer is provided, wherein the first input terminal of the optical mixer is connected to the output terminal of the first optical attenuator, the second input terminal is connected to the output terminal of the second optical attenuator, and the output terminal is connected to the input terminal of the balanced photodetector. By jointly adjusting the first optical attenuator and the second optical attenuator, the light intensity of the two output lights is matched, and the two optical signals are mixed to generate a beat frequency optical signal.

4. The linearity correction system for a dual-micro-ring resonator semiconductor laser according to claim 1, characterized in that, The data processing module includes: An analog-to-digital converter, the input of which is connected to the output of the balanced photodetector, is used to convert the beat frequency electrical signal into a digital signal; A data processing unit, whose input is connected to the output of the analog-to-digital converter, performs a Hilbert transform on the beat frequency digital signal to obtain a transformed complex signal. Based on the characteristic of the Hilbert transform having a 90-degree phase shift filter, the phase change curve of the beat frequency digital signal is obtained using the quotient of the imaginary and real parts of the complex signal. Using the constant proportional relationship between the phase change curve and the original chirped frequency curve of the frequency-modulated continuous wave, the chirped frequency curve of the dual-microring resonant cavity semiconductor laser is calculated. The corresponding desired linear frequency-modulated continuous wave frequency line is calculated using the chirped frequency curve. The frequency modulation nonlinearity of the emitted signal of the dual-microring resonant cavity semiconductor laser is calculated based on the relationship between the obtained actual frequency modulation curve and the ideal linear frequency-modulated continuous wave frequency. The error value between the ideal frequency modulation and the actual frequency modulation curve is calculated. The error value, after being scaled within a preset range, is superimposed on the actual frequency modulation curve to generate the pre-distortion waveform. A digital-to-analog converter (DAC) is provided, with its input terminal connected to the output terminal of the data processing unit and its output terminal connected to the input terminal of the proportional amplifier circuit. The DAC is used to convert the digital signal from the data processing unit into an electrical signal and output it to the proportional amplifier circuit.

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