A low-cost modulation and control device for laser frequency stabilization

Abstract

The application discloses a low-cost modulation and control device for laser frequency stabilization and relates to the fields of optoelectronic technology and precise instrument control. The low-cost modulation and control device for laser frequency stabilization comprises an external cavity semiconductor laser, a polarization beam splitter, an electro-optic modulator, a digital signal processor, a saturated absorption spectrum module and an avalanche photodiode. The low-cost modulation and control device for laser frequency stabilization adopts a full-digital programmable square wave generator to replace a traditional analog oscillator, frequency dynamic adjustment is realized through phase register configuration, an external phase-locked loop or a voltage-controlled tuning circuit is not needed, and the hardware cost is greatly reduced. The square wave generator output signal is limited to binary logic levels, and only a single GPIO pin is needed to drive the electro-optic modulator. Compared with a traditional scheme, the sampling rate requirement of a high-speed data conversion module is eliminated, the PCB area is reduced, and the power consumption density is greatly reduced.

Description

Technical Field

[0001] The present invention relates to the field of photoelectric technology and precision instrument control technology, in particular to a low-cost modulation and control device for laser frequency stabilization. Background Art

[0002] The output frequency of semiconductor lasers is significantly affected by temperature and injection current, resulting in two key defects during free operation:

[0003] A. Linewidth broadening: The typical spectral linewidth is 1-3 nm, which is difficult to meet the precision requirements of cold atom interferometry experiments;

[0004] B. Frequency drift: Temperature fluctuations and injection current fluctuations can cause frequency shifts in the MHz to GHz range.

[0005] To suppress these defects, external-cavity semiconductor lasers use the optical feedback mechanism of the Littrow / Littman structure to compress the linewidth to the order of 0.01 nm. However, such systems still face the following technical bottlenecks:

[0006] Frequency drift: Due to cavity length drift caused by ambient temperature drift and mechanical deformation, the output frequency may shift to GHz within a few hours.

[0007] Mode hopping: Mode contention causes the mode hopping interval to be less than 100 MHz, resulting in discontinuous output spectrum.

[0008] Therefore, external-cavity semiconductor lasers require active frequency stabilization. The modulation spectrum frequency stabilization scheme uses a high-frequency RF source to modulate the electro-optical modulator, so that the saturated absorption spectrum signal passing through the rubidium cell carries the frequency information of the high-frequency RF source. The avalanche diode detects the saturated absorption spectrum carrying the modulation information, which is demodulated by the mixer to obtain a frequency error signal. This signal is fed back to the laser's injection current and PZT via a PID controller, ultimately achieving frequency stabilization.

[0009] The functional modules of a laser frequency stabilization controller include a mixer, phase shifter, RF source, and PID controller. Current FPGA / DSP-based digital frequency stabilization controllers use digital technology to implement the RF source, mixer, phase shifter, and PID controller. Digital RF sources can utilize direct digital synthesis (DDS), which generally offers advantages such as high stability and variable frequency. However, this technology requires a high-precision DAC, whose accuracy is limited by the DAC's precision level and increases costs.

[0010] Analysis of defects in existing technologies:

[0011] Limited oscillator frequency control: In traditional digital-analog hybrid architectures, fixed-frequency oscillators lack dynamic tuning capabilities. If programmable oscillators (such as VCOs) are used to achieve frequency band switching, the circuit complexity will increase significantly (BOM cost increases) and the module package size will increase.

[0012] High-speed signal sampling dependency: To achieve digital processing of modulated signals, a high-speed analog-to-digital converter (ADC) with a sampling rate of 50MS / s or higher is required. This type of device not only has high power consumption density but also forces the system to add multiple stages of signal conditioning circuits (such as anti-aliasing filters and differential drivers), resulting in increased hardware resource consumption.

[0013] Real-time computing resource bottleneck: The mixing algorithm needs to perform complex multiplication and digital filtering, forcing the system to rely on FPGA or high-end DSP for real-time processing, resulting in increased costs.

[0014] Summary of technical issues: The above defects jointly lead to significant disadvantages in the hybrid architecture in terms of cost control, power efficiency and integration, making it difficult to meet the technical requirements of miniaturized quantum sensing devices for low power consumption, high compactness and low cost. Summary of the Invention

[0015] In response to the shortcomings of the existing technology, the present invention provides a low-cost modulation and control device for laser frequency stabilization, which solves the problem that the hybrid architecture in the existing technology has significant disadvantages in cost control, power consumption efficiency and integration, and is difficult to meet the technical requirements of miniaturized quantum sensing equipment for low power consumption, high compactness and low cost.

[0016] To achieve the above objectives, the present invention is implemented through the following technical solutions: a low-cost modulation and control device for laser frequency stabilization, comprising:

[0017] an external cavity semiconductor laser for emitting an initial laser beam;

[0018] a polarization beam splitter that receives the laser beam and splits the laser beam into a first optical path for modulation and a second optical path for output;

[0019] an electro-optical modulator for receiving the first optical path;

[0020] A digital signal processor having a built-in square wave generator, a 1-bit symbolic mixing algorithm, and a PID controller, wherein the square wave generator drives an electro-optical modulator through a phase register to dynamically adjust the frequency and phase of the laser light in the first optical path;

[0021] Saturation absorption spectroscopy module, which performs absorption spectroscopy on the laser modulated by the electro-optical modulator;

[0022] The avalanche photodiode converts the transmitted light intensity output by the saturated absorption spectroscopy module into a current signal, which is then converted into a voltage signal via a transimpedance amplifier. A 1-bit symbolic mixing algorithm is then used to perform polarity-selective multiplication on the square wave signal and the voltage signal. The demodulated DC error signal is then output to the PID controller, which calculates the frequency adjustment value based on the error signal and transmits it to the electro-optical modulator.

[0023] A fully digital programmable square wave generator replaces the traditional analog oscillator, enabling dynamic frequency adjustment through phase register configuration. This eliminates the need for an external phase-locked loop (PLL) or voltage-controlled tuning circuit, significantly reducing hardware costs. The square wave generator's output signal is limited to binary logic levels, requiring only a single GPIO pin to drive the electro-optical modulator. This eliminates the need for a 16-bit DAC and accompanying anti-aliasing filter in traditional solutions, eliminating the 50 MS / s sampling rate requirement for the high-speed data conversion module's DAC / ADC. This reduces PCB area and significantly lowers power consumption. The digital signal processor's 1-bit symbolic mixing algorithm, based on a 1-bit quantized data stream, significantly reduces computational complexity and real-time operations compared to traditional 32-bit floating-point operations. This allows the system to utilize low-cost DSP chips, reducing processor costs.

[0024] Preferably, a single GPIO pin is connected between the square wave generator and the electro-optical modulator, and an analog-to-digital converter is provided between the digital signal processor and the avalanche photodiode.

[0025] Preferably, the digital signal processor has a built-in timer, and the timer uses a 100 MHz clock as a reference and generates two 50% duty cycle square waves through phase register configuration:

[0026] A main square wave, which is used to drive the electro-optical modulator to perform phase modulation on the first optical path, and the frequency of the main square wave is adjustable;

[0027] A synchronous square wave is used to compensate for the path delay of a square wave signal output from a single GPIO pin through an electro-optical modulator, a saturated absorption spectroscopy module, an avalanche photodiode, and an analog-to-digital converter.

[0028] The digital signal processor's built-in timer uses a 100 MHz clock as a reference and generates two 50% duty cycle square waves through phase register configuration. The frequency of the main square wave is adjustable from 100 kHz to 10 MHz. This drives the electro-optical modulator to phase modulate the laser light in the first optical path. This synchronized square wave is then used for subsequent frequency mixing and demodulation. The square wave signal is output to the electro-optical modulator via a single GPIO pin, replacing a traditional analog oscillator and eliminating the need for high-speed DAC / ADC sampling.

[0029] Preferably, the voltage signal is sampled by a 16-bit ADC at a rate of 10 MS / s, and input into a digital signal processor for real-time processing.

[0030] Preferably, the digital signal processor performs a 1-bit symbolized mixing algorithm as follows:

[0031] When the synchronization square wave is logic 1, the ADC sample value is directly accumulated;

[0032] When the synchronization square wave is logic 0, the sample value after inversion is accumulated.

[0033] Preferably, the digital signal processor has a built-in accumulator, and the accumulator uses 32-bit fixed-point operation to output a direct current error signal to a PID controller.

[0034] Preferably, the PID controller has a proportional gain Kp=0.5, an integral gain Ki=0.1, and a differential gain Kd=0.01, and outputs an amplitude limiting range of ±5 V, and the PID controller calculates a frequency adjustment amount according to the error signal and outputs a 0-10 V voltage through a 12-bit DAC to a high-voltage amplifier.

[0035] Preferably, the external cavity tuning actuator of the external cavity semiconductor laser is a piezoelectric ceramic, and the high-voltage amplifier linearly converts the control voltage into a 0-100 V drive to the piezoelectric ceramic, adjusts the external cavity length, and realizes precise locking of the laser frequency and the atomic transition line.

[0036] Preferably, the laser modulated by the electro-optic modulator enters a rubidium atom absorption cell of a saturated absorption spectroscopy module, and an error signal is generated through a saturated absorption effect, reflecting the deviation of the laser frequency and the atomic transition line.

[0037] It has the following beneficial effects:

[0038] 1. The low-cost modulation and control device for laser frequency stabilization adopts a fully digital programmable square wave generator 41 to replace a traditional analog oscillator, realizes dynamic frequency adjustment through phase register configuration, does not need an external phase-locked loop or voltage-controlled tuning circuit, and greatly reduces hardware cost. The square wave generator output signal is limited to binary logic level, and only a single GPIO pin is needed to drive the electro-optic modulator. Compared with the traditional scheme requiring a 16-bit DAC and a supporting anti-aliasing filter, the sampling rate requirement of the high-speed data conversion module DAC / ADC≥50 MS / s is eliminated, the PCB area is reduced, and the power consumption density is greatly reduced. The 1-bit symbolized mixing algorithm of the digital signal processor is based on 1-bit quantized data stream, and compared with traditional 32-bit floating-point operation, the calculation complexity and real-time operation amount are greatly reduced, the system can be equipped with a low-cost DSP chip, and the processor cost is reduced.

[0039] 2. This low-cost modulation and control device for laser frequency stabilization uses an external-cavity semiconductor laser to emit an initial laser beam, with its wavelength locked to a target atomic transition line, such as the D2 line of rubidium atoms. The laser light is then split into two paths by polarization beam splitting. The first path is the modulation path and inputs the electro-optical modulator. The second path is the output path, which directly serves as the system output laser voltage signal. The signal is sampled at a rate of 10 MS / s by a 16-bit ADC and input into a digital signal processor for real-time processing. The DSP executes a 1-bit symbolic mixing algorithm. When the synchronous square wave is a logic 1, the ADC sampled values ​​are directly accumulated. When the synchronous square wave is a logic 0, the inverted sampled values ​​are accumulated. The accumulator uses 32-bit fixed-point arithmetic to output the demodulated DC error signal to the PID controller.

[0040] 3. This low-cost modulation and control device for laser frequency stabilization uses a digital signal processor with a built-in timer based on a 100MHz clock. It generates two 50% duty cycle square waves through phase register configuration. The frequency of the main square wave is adjustable from 100kHz to 10MHz, driving an electro-optical modulator to phase modulate the laser light in the first optical path. The synchronized square wave compensates for the square wave signal's path delay from a single GPIO pin through the electro-optical modulator, saturated absorption spectroscopy module, avalanche photodiode, and analog-to-digital converter. The square wave signal is output to the electro-optical modulator via a single GPIO pin, replacing a traditional analog oscillator and eliminating the need for high-speed DAC / ADC sampling.

[0041] 4. This low-cost modulation and control device for laser frequency stabilization uses modulated laser light to enter a rubidium atomic absorption cell, generating an error signal through the saturated absorption effect, reflecting the deviation between the laser frequency and the atomic transition line. The avalanche photodiode converts the transmitted light intensity into a current signal, which is then converted into a voltage signal by a transimpedance amplifier. PID parameter configuration: proportional gain Kp = 0.5, integral gain Ki = 0.1, differential gain Kd = 0.01, output limit range ±5 V to prevent overdrive. The PID controller calculates the frequency adjustment amount based on the error signal and outputs a 0-10 V voltage to the high-voltage amplifier through a 12-bit DAC. The high-voltage amplifier linearly converts the control voltage into 0-100 V to drive the piezoelectric ceramic of the external cavity semiconductor laser, adjusts the external cavity length, and achieves precise locking of the laser frequency and the atomic transition line. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0043] Figure 1 Fig. 1 is a schematic diagram of the overall structure of the present application;

[0044] Figure 2 Fig. 2 is a schematic diagram of the structure of the digital signal processor of the present application;

[0045] Figure 3 Fig. 3 is a schematic diagram of the implementation flow of the digital signal processor of the present application.

[0046] In the figure: 1, external cavity semiconductor laser; 11, piezoelectric ceramic; 2, polarization beam splitter; 3, electro-optic modulator; 4, digital signal processor; 41, square wave generator; 42, PID controller; 43, timer; 44, single GPIO pin; 45, accumulator; 5, saturated absorption spectroscopy module; 6, avalanche photodiode. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application is described clearly and completely. Obviously, the described embodiments are part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0048] In order to better understand the above technical scheme, the above technical scheme will be described in detail below in combination with the drawings in the specification and specific embodiments.

[0049] The embodiments of the present application disclose a low-cost modulation and control device for laser frequency stabilization. According to the accompanying drawings and specific embodiments, the device comprises: Figure 1-2 as shown, including:

[0050] The external cavity semiconductor laser 1 is used to emit an initial laser beam;

[0051] The polarization beam splitter 2 receives the laser beam and divides the laser beam into a first light path for modulation and a second light path for output;

[0052] The electro-optic modulator 3 is used to receive the first light path;

[0053] The digital signal processor 4 is built-in square wave generator 41, 1-bit symbolization mixing algorithm and PID controller 42, and the square wave generator 41 drives the electro-optic modulator 3 to dynamically adjust the frequency and phase of the first light path laser through the phase register;

[0054] The saturated absorption spectroscopy module 5 absorbs the spectroscopy of the laser modulated by the electro-optic modulator 3;

[0055] The avalanche photodiode 6 converts the transmitted light intensity output by the saturated absorption spectroscopy module 5 into a current signal, which is then converted into a voltage signal via a transimpedance amplifier. A 1-bit symbolic mixing algorithm is then used to perform polarity-selective multiplication on the square wave signal and the voltage signal, and the demodulated DC error signal is output to the PID controller 42. The PID controller 42 calculates the frequency adjustment amount based on the error signal and transmits it to the electro-optical modulator 3.

[0056] A fully digital programmable square wave generator 41 replaces the traditional analog oscillator. Dynamic frequency adjustment is achieved through phase register configuration, eliminating the need for an external phase-locked loop (PLL) or voltage-controlled tuning circuit, significantly reducing hardware costs. The output signal of square wave generator 41 is limited to binary logic levels, requiring only a single GPIO pin 44 to drive the electro-optical modulator 3. This eliminates the need for a 16-bit DAC and accompanying anti-aliasing filter in traditional solutions, eliminating the need for a sampling rate of ≥50 MS / s for the high-speed data conversion module DAC / ADC. This reduces PCB area and significantly reduces power consumption. The 1-bit symbolic mixing algorithm in digital signal processor 4, based on a 1-bit quantized data stream, significantly reduces computational complexity and real-time operations compared to traditional 32-bit floating-point operations. This allows the system to utilize a low-cost DSP chip, reducing processor costs.

[0057] PID parameter configuration: proportional gain Kp = 0.5, integral gain Ki = 0.1, differential gain Kd = 0.01, and output limiting range ±5 V to prevent overdrive. PID controller 42 calculates the frequency adjustment based on the error signal and outputs a 0-10 V voltage to the high-voltage amplifier via a 12-bit DAC. The high-voltage amplifier linearly converts the control voltage to 0-100 V to drive the piezoelectric ceramic 11 of the external-cavity semiconductor laser 1, adjusting the external cavity length to achieve precise locking of the laser frequency with the atomic transition line.

[0058] According to the attached Figure 3 As shown, a single GPIO pin 44 is connected between the square wave generator 41 and the electro-optical modulator 3 , and an analog-to-digital converter is provided between the digital signal processor 4 and the avalanche photodiode 6 .

[0059] The digital signal processor 4 has a built-in timer 43, and the timer 43 uses a 100 MHz clock as a reference and generates two 50% duty cycle square waves through the phase register configuration:

[0060] A main square wave, which is used to drive the electro-optical modulator 3 to perform phase modulation on the first optical path, and the frequency of the main square wave is adjustable;

[0061] The synchronous square wave is used to compensate for the path delay of the square wave signal output from the single GPIO pin 44 through the electro-optic modulator 3, the saturated absorption spectrum module 5, the avalanche photodiode 6 and the analog-to-digital converter.

[0062] The built-in timer 43 in the digital signal processor 4 generates two 50% duty cycle square waves based on a 100 MHz clock through phase register configuration. The frequency of the main square wave is adjustable, and the adjustment range is specifically 100 kHz-10 MHz. The electric-optical modulator 3 is driven to perform phase modulation on the laser in the first optical path. The synchronous square wave is used to compensate for the path delay of the square wave signal from the single GPIO pin 44 output, through the electric-optical modulator 3, the saturated absorption spectrum module 5, the avalanche photodiode 6, and the analog-to-digital converter. The square wave signal is output to the electric-optical modulator 3 through the single GPIO pin 44, replacing the traditional analog oscillator, and eliminating the need for high-speed sampling of DAC / ADC.

[0063] The voltage signal is sampled at a rate of 10 MS / s by a 16-bit ADC and input to the digital signal processor 4 for real-time processing.

[0064] The digital signal processor 4 performs a 1-bit symbolization mixing algorithm as follows:

[0065] When the synchronous square wave is logic 1, the ADC sample value is directly accumulated.

[0066] When the synchronous square wave is logic 0, the sample value after inversion is accumulated.

[0067] The digital signal processor 4 is built-in with an accumulator 45, and the accumulator 45 uses 32-bit fixed-point operation to output a direct current error signal to the PID controller 42.

[0068] The voltage signal is sampled at a rate of 10 MS / s by a 16-bit ADC and input to the digital signal processor 4 for real-time processing. The digital signal processor 4 performs a 1-bit symbolization mixing algorithm. When the synchronous square wave is logic 1, the ADC sample value is directly accumulated. When the synchronous square wave is logic 0, the sample value after inversion is accumulated. The accumulator 45 uses 32-bit fixed-point operation to output a demodulated direct current error signal to the PID controller 42.

[0069] The proportional gain Kp of the PID controller 42 is 0.5, the integral gain Ki is 0.1, and the differential gain Kd is 0.01. The output amplitude range is ±5 V. The PID controller 42 calculates the frequency adjustment amount according to the error signal and outputs a 0-10 V voltage to the high-voltage amplifier through a 12-bit DAC.

[0070] The external cavity tuning actuator of the external cavity semiconductor laser 1 is a piezoelectric ceramic 11. The high-voltage amplifier linearly converts the control voltage to a 0-100 V drive voltage to drive the piezoelectric ceramic 11, adjust the external cavity length, and achieve precise locking of the laser frequency and the atomic transition line.

[0071] The modulated laser enters the rubidium atomic absorption cell of the saturated absorption spectroscopy module 5, and an error signal is generated through the saturated absorption effect, reflecting the deviation of the laser frequency from the atomic transition line.

[0072] The workflow is as follows:

[0073] Step 1: Optical beam splitting and initial modulation

[0074] Laser output: The external cavity semiconductor laser 1 emits an initial laser beam, with the wavelength locked to the target atomic transition line, such as the rubidium D2 line;

[0075] Polarization beam splitting: The laser is split into two paths by the polarization beam splitter 2:

[0076] The first light path is the modulation path, which inputs the electro-optic modulator 3;

[0077] The second light path is the output path: directly as the system output laser;

[0078] Step 2: Digital square wave driving phase modulation

[0079] Square wave generation: The digital signal processor 4 has a built-in timer 43 with a 100 MHz clock as the reference, and generates two square waves with a 50% duty cycle through phase register configuration:

[0080] The main square wave, with a frequency that can be adjusted within the range of 100 kHz-10 MHz, drives the electro-optic modulator 3 to perform phase modulation on the first light path laser.

[0081] The synchronization square wave is used to compensate for the path delay of the square wave signal from the single GPIO pin 44 output, through the electro-optic modulator 3, saturated absorption spectroscopy module 5, avalanche photodiode 6, and analog-to-digital converter.

[0082] Modulation execution: The square wave signal is output to the electro-optic modulator 3 through the single GPIO pin 44, replacing the traditional analog oscillator and eliminating the need for high-speed sampling of DAC / ADC.

[0083] Step 3: Saturated absorption spectroscopy detection

[0084] Spectral modulation: The modulated laser enters the rubidium atomic absorption cell, and an error signal is generated through the saturated absorption effect, reflecting the deviation of the laser frequency from the atomic transition line.

[0085] Optical signal conversion: The avalanche photodiode 6 converts the transmitted light intensity into an electric current signal, which is converted into a voltage signal by a transimpedance amplifier.

[0086] Step 4: 1-bit quantization and mixed-frequency demodulation

[0087] Digital sampling: The voltage signal is sampled at a rate of 10 MS / s by a 16-bit ADC and input into a digital signal processor 4 for real-time processing.

[0088] Symbolic mixing: Digital signal processor 4 performs a 1-bit symbolic mixing algorithm:

[0089] When the synchronous square wave is logic 1, the ADC sampling values ​​are directly accumulated.

[0090] When the synchronous square wave is logic 0, the inverted sample values ​​are accumulated.

[0091] Error signal extraction: The accumulator 45 uses 32-bit fixed-point arithmetic to output the demodulated DC error signal to the PID controller 42 in the range of [-2³¹, 2³¹-1].

[0092] Step 5: PID closed-loop control and frequency locking

[0093] PID parameter configuration: proportional gain Kp = 0.5, integral gain Ki = 0.1, differential gain Kd = 0.01, output limit range ±5 V to prevent overdrive.

[0094] Correction value generation: The PID controller 42 calculates the frequency adjustment value based on the error signal and outputs a 0-10 V voltage to the high-voltage amplifier through a 12-bit DAC.

[0095] External cavity tuning: The high-voltage amplifier linearly converts the control voltage into 0-100 V to drive the piezoelectric ceramic 11 of the external cavity semiconductor laser 1, adjusts the external cavity length, and achieves precise locking of the laser frequency and the atomic transition line.

[0096] A fully digital programmable square wave generator 41 replaces the traditional analog oscillator. Dynamic frequency adjustment is achieved through phase register configuration, eliminating the need for an external phase-locked loop (PLL) or voltage-controlled tuning circuit, significantly reducing hardware costs. The output signal of square wave generator 41 is limited to binary logic levels, requiring only a single GPIO pin 44 to drive the electro-optical modulator 3. This eliminates the need for a 16-bit DAC and accompanying anti-aliasing filter in traditional solutions, eliminating the need for a sampling rate of ≥50 MS / s for the high-speed data conversion module DAC / ADC. This reduces PCB area and significantly reduces power consumption. The 1-bit symbolic mixing algorithm in digital signal processor 4, based on a 1-bit quantized data stream, significantly reduces computational complexity and real-time operations compared to traditional 32-bit floating-point operations. This allows the system to utilize a low-cost DSP chip, reducing processor costs.

[0097] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting; it is not intended to exclude myriad other embodiments of the present application that other inventors can develop based on the description herein. A person of ordinary skill in the art will recognize that elements from the various embodiments can be combined to form additional embodiments. It is intended that the specification and examples be considered as exemplary only, with the true scope of the application being indicated by the following claims.

[0098] The foregoing is considered as illustrative only of the principles of the application. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the application to the exact construction and practice described. Accordingly, all such variations are intended to be included within the scope of the present application as defined in the following claims, along with the full scope of equivalents to which such claims are entitled.

Claims

1. A low-cost modulation and control device for laser frequency stabilization, characterized in that: include: An external cavity semiconductor laser (1) for emitting an initial laser beam; A polarization beam splitter (2) receives a laser beam and splits the laser beam into a first optical path for modulation and a second optical path for output; an electro-optical modulator (3) for receiving a first optical path; A digital signal processor (4) having a built-in square wave generator (41), a 1-bit symbolic frequency mixing algorithm, and a PID controller (42), wherein the square wave generator (41) drives the electro-optical modulator (3) through a phase register to dynamically adjust the frequency and phase of the laser light in the first optical path; a saturation absorption spectrum module (5) for performing absorption spectrum analysis on the laser light modulated by the electro-optical modulator (3); An avalanche photodiode (6) converts the transmitted light intensity output by the saturated absorption spectrum module (5) into a current signal, and converts it into a voltage signal through a transimpedance amplifier. Then, a 1-bit symbolic mixing algorithm is used to perform polarity-selective multiplication on the square wave signal and the voltage signal, and the demodulated DC error signal is output to a PID controller (42). The PID controller (42) calculates a frequency adjustment amount based on the error signal and outputs it to the electro-optical modulator (3).

2. A low-cost modulation and control device for laser frequency stabilization according to claim 1, characterized in that: A single GPIO pin (44) is connected between the square wave generator (41) and the electro-optical modulator (3), and an analog-to-digital converter is provided between the digital signal processor (4) and the avalanche photodiode (6).

3. A low-cost modulation and control device for laser frequency stabilization according to claim 2, characterized in that: The digital signal processor (4) has a built-in timer (43), and the timer (43) uses a 100 MHz clock as a reference and generates two 50% duty cycle square waves through phase register configuration: A main square wave, which is used to drive the electro-optical modulator (3) to perform phase modulation on the first optical path, and the frequency of the main square wave is adjustable; A synchronous square wave is used to compensate for the path delay of a square wave signal output from a single GPIO pin (44) through an electro-optical modulator (3), a saturated absorption spectroscopy module (5), an avalanche photodiode (6) and an analog-to-digital converter.

4. A low-cost modulation and control device for laser frequency stabilization according to claim 1, characterized in that: The voltage signal is sampled at a rate of 10 MS / s by a 16-bit ADC and input into a digital signal processor (4) for real-time processing.

5. A low-cost modulation and control device for laser frequency stabilization according to claim 1, characterized in that: The digital signal processor (4) executes the 1-bit symbolic mixing algorithm as follows: When the synchronous square wave is logic 1, the ADC sampling value is directly accumulated; When the synchronous square wave is logic 0, the inverted sample values ​​are accumulated.

6. A low-cost modulation and control device for laser frequency stabilization according to claim 1, characterized in that: The digital signal processor (4) has a built-in accumulator (45), and the accumulator (45) uses 32-bit fixed-point arithmetic to output a DC error signal to the PID controller (42).

7. A low-cost modulation and control device for laser frequency stabilization according to claim 1, characterized in that: The PID controller (42) has a proportional gain Kp=0.5, an integral gain Ki=0.1, a differential gain Kd=0.01, and an output limit range of ±5 V. The PID controller (42) calculates a frequency adjustment amount based on an error signal and outputs a 0-10 V voltage to a high-voltage amplifier through a 12-bit DAC.

8. A low-cost modulation and control device for laser frequency stabilization according to claim 7, characterized in that: The external cavity tuning actuator of the external cavity semiconductor laser (1) is set as a piezoelectric ceramic (11), and the high voltage amplifier linearly converts the control voltage into 0-100 V to drive the piezoelectric ceramic (11), adjusts the external cavity length, and realizes precise locking of the laser frequency and the atomic transition line.

9. A low-cost modulation and control device for laser frequency stabilization according to claim 1, characterized in that: The laser modulated by the electro-optic modulator (3) enters the rubidium atomic absorption cell of the saturation absorption spectrum module (5), and generates an error signal through the saturation absorption effect, reflecting the deviation between the laser frequency and the atomic transition line.

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