PDH-based double-parameter frequency stabilization method and system

Abstract

The invention discloses a PDH-based double-parameter frequency stabilization method and system, and relates to the technical field of laser frequency stabilization, and the method comprises the following steps: 1, enabling a laser to be subjected to frequency stabilization to emit laser, outputting the laser through an optical isolator, and carrying out the polarization splitting of the laser through a half-wave plate 1 and a PBS 1; the optical path structure is simple, common optical elements are orderly arranged according to functions, the building and debugging difficulty is reduced, loss errors are reduced, the overall performance stability is improved, the PZT rapidly adjusts the shape to compensate for the cavity length change of the F-P cavity based on feedback, the resonant frequency rapidly restabilizes, the environmental interference is overcome, the environmental adaptability is enhanced, and the optical path structure is suitable for multiple scenes and does not need complex environmental control. Double-parameter frequency stabilization and a real-time monitoring feedback mechanism are combined, frequency stabilization can still be performed when environmental interference is serious, the performance reduction risk is reduced, the operation reliability and stability are improved, the maintenance cost and environmental requirements are reduced, and an efficient, reliable and economical solution is provided for the laser frequency stabilization technology.

Description

Technical Field

[0001] The invention relates to the technical field of laser frequency stabilization, and in particular to a method and system for PDH dual-parameter frequency stabilization. Background Art

[0002] In laser frequency stabilization technology, it is usually necessary to compare the laser frequency to be stabilized with a stable reference frequency to measure the difference between the two and obtain a frequency discrimination signal. Subsequently, the laser frequency to be stabilized is locked to the reference frequency through feedback adjustment. This technology is an important means to ensure the stability of the laser frequency. However, the existing laser frequency stabilization technology has some significant disadvantages.

[0003] A common reference frequency is the atomic and molecular energy level transition frequency. A frequency-stabilized laser that uses this frequency as a reference can ensure excellent frequency stability. However, its reference frequency is limited to a specific energy level transition frequency, so the reference frequency is relatively fixed and lacks flexibility.

[0004] Another reference frequency is the resonant frequency of the resonant cavity, which mainly depends on the cavity length. The selection of this reference frequency is more flexible and can effectively supplement the gap in the frequency locking range based on the atomic and molecular energy level transition frequency. In particular, the frequency stabilization technology based on the resonant frequency of the FP resonant cavity has received widespread attention in practical applications. This technology mainly uses an electro-optical phase modulator (EOM) to phase modulate the laser, and then injects it into the optical resonant cavity. The laser reflected back by the cavity is collected by the detector and demodulated with the modulation signal of the EOM to obtain an error signal. The laser frequency can be adjusted by the error signal to stabilize the laser frequency at the resonant frequency of the resonant cavity. By changing the cavity length of the resonant cavity, its resonant frequency can be changed, so that the laser can be locked at different frequencies.

[0005] However, as a high-fineness resonant cavity, the cavity length of the FP cavity is easily affected by external environmental factors such as vibration and temperature. The fluctuations of these external factors will cause changes in the resonant frequency, thereby affecting the stability of the laser frequency. Although some measures can be taken to reduce the impact of these factors, it is still a technical challenge to completely eliminate their impact. Therefore, the traditional frequency stabilization technology based on the resonant frequency of the FP resonant cavity has certain shortcomings in environmental adaptability.

[0006] In summary, the existing laser frequency stabilization technology has obvious shortcomings in the selection of reference frequency and environmental adaptability. In order to overcome these shortcomings, it is necessary to propose a new frequency stabilization method and technical solution to improve the stability and environmental adaptability of the laser frequency. Summary of the invention

[0007] The purpose of the present invention is to make up for the deficiencies of the prior art and provide a method and system based on PDH dual-parameter frequency stabilization. The optical path structure of the present invention is simple, and common optical elements are arranged in order according to function, so as to realize multi-function and non-redundant design, reduce the difficulty of construction and debugging, reduce loss error, and improve the overall performance stability. PZT can adjust the shape quickly based on feedback to compensate for the change of FP cavity length, so that the resonant frequency can be quickly stabilized, overcome environmental interference, enhance environmental adaptability, be suitable for multiple scenarios and do not require complex environmental control, and combine dual-parameter frequency stabilization with real-time monitoring feedback mechanism. The system has strong robustness and can still stabilize the frequency when the environmental interference is serious, reduce the risk of performance degradation, improve the reliability and stability of operation, reduce maintenance costs and environmental requirements, and provide an efficient, reliable and economical solution for laser frequency stabilization technology.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions: On the one hand, a method for frequency stabilization based on PDH dual parameters comprises the following steps:

[0009] Step 1: The frequency-stabilized laser (1) emits laser light, which is then outputted by the optical isolator (2) and then polarized by a half-wave plate (3) and a PBS (4). One path is used for frequency monitoring through an optical collimator (18), and the other path is inputted through a 45° laser reflector (6) and a 45° laser reflector (7) to a half-wave plate (8) and a PBS (9) for polarization splitting again.

[0010] Step 2: After the light beam is split again in step 1, it passes through a quarter wave plate (10) and then enters the FP cavity (11). The reflected carrier and the modulated sideband of the FP cavity (11) pass through the quarter wave plate (10) again, and after a phase delay of π / 2, it is reflected by PBS 2 (9) into PD 1 (13) to obtain the beat frequency signal of the reflected carrier and the modulated sideband;

[0011] Step 3: The direct digital frequency synthesizer (17) generates a demodulated signal (16) of the same path, which is phase-shifted and connected to the mixer (15) and the beat signal received by PD-1 (13) for demodulation, and a feedback signal is obtained after further circuit operation processing;

[0012] Step 4: Use the feedback signal obtained in step 3 to adjust the laser and PZT respectively to perform dual parameter frequency stabilization, wherein the collimator (18) optical fiber output laser and the frequency monitor (19) and the computer (20) constitute a laser frequency short-time monitoring system, and the optical collimator (18) optical fiber output laser and the reference laser (21), PD 2 (22), and the frequency counter (23) constitute a laser frequency long-time monitoring system.

[0013] Furthermore, in step one, the laser light emitted by the laser to be stabilized (1) is output after passing through the optical isolator (2). The optical isolator (2) controls the propagation direction of the laser light through a combination of internal optical elements, including a polarizer to select the polarization direction and a Faraday rotator to achieve non-reciprocal rotation, so as to isolate the interference of reflected light and ensure the stability and unidirectionality of the laser output.

[0014] Furthermore, in step 2, the quarter wave plate (10) causes the reflected carrier and the modulation sideband to produce phase changes when the laser enters and leaves the FP cavity (11). Based on the difference in refractive index for light of different polarization directions, the different optical paths produce phase differences. The phase difference affects the reflection and transmission characteristics of the laser in the FP cavity (11), and after being reflected by PBS 2 (9), it enters PD 1 (13) to form a beat frequency signal.

[0015] Furthermore, in step three, the demodulation signal (16) generated by the direct digital frequency synthesizer (17) has adjustable parameters, which is generated by the frequency division and phase accumulation operation of the internal digital circuit, and after being phase-shifted by the phase shift circuit, it is mixed and demodulated with the beat frequency signal received by the PD-1 (13) in the mixer (15). The mixer (15) uses nonlinear elements to multiply to generate multiple frequency component output signals, and the feedback signal is obtained through circuit operation processing such as filtering.

[0016] Furthermore, in step 4, the feedback signal is used to adjust the laser frequency and PZT. When the laser frequency is adjusted, the feedback signal is transmitted to the drive circuit, and the drive circuit changes the internal working parameters of the laser by changing the injection current, adjusting the working temperature, etc. When the PZT is adjusted, the feedback signal is transmitted to the drive circuit, and the drive circuit applies a voltage to the PZT to deform it and change the cavity length of the FP cavity (11), thereby realizing dual-parameter frequency stabilization.

[0017] On the other hand, a system based on PDH dual-parameter frequency stabilization includes:

[0018] Laser emission and light splitting module: comprising a laser to be stabilized (1), an optical isolator (2), a half wave plate 1 (3), a PBS 1 (4), a half wave plate 2 (5), a 45° laser reflector 1 (6), a 45° laser reflector 2 (7), a half wave plate 3 (8) and a PBS 2 (9), for emitting laser light and performing multiple polarization splitting;

[0019] The frequency modulation and monitoring module comprises a quarter wave plate (10), an FP cavity (11), a PD-1 (13), a direct digital frequency synthesizer (17), a mixer (15) and a demodulation signal (16), and is used to perform frequency modulation on the laser, obtain a beat frequency signal and perform demodulation to obtain a feedback signal;

[0020] Feedback adjustment module: comprising a driving circuit board (12), a servo controller (14) and a PZT, and used for adjusting the laser and the PZT respectively according to the feedback signal;

[0021] The frequency monitoring system includes a short-time laser frequency monitoring system, which is composed of an optical collimator (18), a frequency monitor (19) and a computer (20), and a long-time laser frequency monitoring system, which is composed of an optical collimator (18), a reference laser (21), PD II (22) and a frequency counter (23).

[0022] Furthermore, in the laser emission and light splitting module, the optical isolator (2) cooperates with the laser to be stabilized (1), the input port of the optical isolator (2) is aligned with the output port of the laser to be stabilized (1), the internal polarizer and Faraday rotator are arranged to realize unidirectional transmission of laser, the half wave plate (3) and the PBS (4) are arranged in sequence, the half wave plate (3) rotates to adjust the polarization state to match the light splitting characteristics of the PBS (4), and then the 45° laser reflector (6) and the 45° laser reflector (7) change the light propagation direction, the half wave plate (8) and the PBS (9) are polarized and split again, and the optical elements work together to realize laser light splitting.

[0023] Furthermore, in the frequency modulation and monitoring module, a quarter wave plate (10) is located in the incident and outgoing optical paths of the FP cavity (11). Its special optical structure causes a phase difference in the laser polarization component to change the reflection and transmission characteristics in the cavity to generate reflected light. A direct digital frequency synthesizer (17) generates a demodulation signal (16) through an internal digital circuit and a clock signal source, which is mixed and demodulated in a mixer (15) with the beat signal received by PD-1 (13). The nonlinear element of the mixer (15) is multiplied to generate a mixed signal, which is processed by a subsequent circuit to obtain a feedback signal.

[0024] Furthermore, in the feedback adjustment module, the internal microprocessor of the servo controller (14) runs the algorithm program, the storage unit stores data, the communication interface transmits data with the driving circuit board (12), the signal amplification circuit of the driving circuit board (12) amplifies the signal, and the power driving circuit provides voltage to the PZT to deform it to adjust the cavity length of the FP cavity (11), and adjust the laser working parameters at the same time. The various components of the frequency monitoring system cooperate, the optical collimator (18) collimates the laser, the frequency monitor (19) monitors the frequency and transmits data to the computer (20), the reference laser (21) and the monitored laser act on PD II (22) to generate a frequency difference signal, which is processed by the frequency counter (23) to provide data support for the system.

[0025] Compared with the prior art, the method and system based on PDH dual-parameter frequency stabilization have the following beneficial effects:

[0026] 1. The optical path structure of the present invention is relatively simple, and is mainly composed of common optical elements such as a laser to be stabilized, an optical isolator, various wave plates, a PBS, a reflector and an FP cavity. The optical path connection is clear and the optical elements are arranged in sequence according to functional requirements, realizing functions such as laser emission, light splitting, frequency modulation and monitoring. There is no complex redundant optical path design, which reduces the difficulty of optical path construction and debugging, and also reduces the additional loss and error introduced by the complexity of the optical path, thereby improving the overall performance and stability of the system.

[0027] Second, the PZT in the present invention can quickly adjust its own deformation according to the feedback signal, thereby accurately compensating for the change in cavity length. This dynamic adjustment capability enables the resonant frequency of the FP cavity to quickly return to a stable state, effectively overcoming the interference of environmental factors on the resonant frequency of the resonant cavity, so that the system can still maintain good frequency stability performance under complex and changeable environmental conditions, greatly improving the environmental adaptability of the system, and is suitable for a variety of actual working scenarios, without the need for complex environmental control equipment to maintain a stable working environment.

[0028] 3. The present invention adopts a dual-parameter frequency stabilization and real-time monitoring feedback mechanism. The entire system is more robust to environmental changes. Even when the external environment is severely disturbed, the system can maintain the relative stability of the laser frequency through its own adjustment mechanism, reducing the risk of system performance degradation or even failure due to environmental factors, improving the reliability and stability of the system operation, and reducing the system maintenance cost and requirements for the working environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 is a schematic diagram of the structure of this method;

[0031] Figure 2 This is a schematic diagram of the functional implementation of this method.

[0032] The invention comprises: a laser to be frequency-stabilized (1); an optical isolator (2); a half-wave plate (1) (3); a PBS (1) (4); a half-wave plate (2) (5); a 45° laser reflector (1) (6); a 45° laser reflector (2) (7); a half-wave plate (3) (8); a PBS (2) (9); a quarter-wave plate (10); an FP cavity (11); a driving circuit board (12); a PD (1) (13); a servo controller (14); a mixer (15); a demodulated signal (16); a direct digital frequency synthesizer (17); an optical collimator (18); a frequency monitor (19); a computer (20); a reference laser (21); a PD (2) (22); and a frequency counter (23). DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] 1. System Construction

[0035] Laser emission and spectrometer module:

[0036] The laser to be stabilized (1) is a suitable laser type, such as a semiconductor laser, which can output a laser beam with a certain frequency and power, and the optical isolator (2) is tightly connected to the output port of the laser to be stabilized (1), ensuring that the optical elements such as the polarizer and the Faraday rotator inside the optical isolator (2) are in normal working state, so as to achieve effective control of the unidirectional transmission of the laser and prevent the reflected light from affecting the laser performance;

[0037] like Figure 1As shown, a half wave plate (3) is installed on the optical path after the optical isolator (2). By precisely adjusting its angle, the polarization state of the laser is changed to match the spectral characteristics of the subsequent PBS (4). The PBS (4) divides the laser into two paths based on its selective transmission and reflection principle for light in different polarization directions. One path leads to an optical collimator (18). The optical collimator (18) is used to collimate the laser output from the optical fiber into a parallel beam for subsequent frequency monitoring. The other path of laser passes through a 45° laser reflector (1). After the propagation direction is changed by 45° laser reflector 1 (6) and 45° laser reflector 2 (7), the polarization splitting operation is performed again at half wave plate 3 (8) and PBS 2 (9). When installing 45° laser reflector 1 (6) and 45° laser reflector 2 (7), it is necessary to ensure that their reflection surfaces are flat and the angles are precise to ensure the accuracy of the laser reflection path. Half wave plate 3 (8) also further controls the polarization state of the laser by adjusting the angle. PBS 2 (9) performs splitting again to prepare for the subsequent laser to enter the FP cavity (11).

[0038] Frequency modulation and monitoring module:

[0039] like Figure 1 As shown, a quarter wave plate (10) is placed on a beam path after the light is split by PBS II (9), and is located on the incident and outgoing light paths of the FP cavity (11). The optical structure of the quarter wave plate (10) should ensure that it produces a phase difference of π / 2 for the two perpendicular polarization components of the laser. This phase difference will affect the reflection and transmission characteristics of the laser in the FP cavity (11). The FP cavity (11) uses two parallel reflectors with high reflectivity to form a resonant cavity structure. Its cavity length and other parameters should be designed and adjusted according to the required resonant frequency. After the reflected carrier and the modulated sideband interact with each other in the FP cavity (11), they pass through the quarter wave plate (10) again, and the phase relationship is further changed. Then, they are reflected by PBS II (9) and enter PD I (13). As a photoelectric detector, PD I (13) should have a high photoelectric conversion efficiency and response speed to accurately convert the optical signal into an electrical signal, thereby obtaining the beat frequency signal of the reflected carrier and the modulated sideband.

[0040] The direct digital frequency synthesizer (17) generates a demodulated signal (16) according to preset frequency control parameters through an internal digital circuit and a clock signal source. The frequency, phase and other parameters of the demodulated signal (16) should have a certain correlation and matching with the modulation signal of the laser to be stabilized after a series of previous operations. The generated demodulated signal (16) is subjected to a phase shift operation by a phase shift circuit. The network structure composed of capacitors, inductors and other components in the phase shift circuit should be accurately adjusted to achieve accurate change of the phase of the demodulated signal (16). The demodulated signal after phase shift is connected to a mixer (15). The mixer circuit composed of nonlinear components such as diodes or transistors in the mixer (15) should be in a normal working state. The demodulated signal after phase shift is multiplied with the beat frequency signal received by the PD-1 (13) by utilizing nonlinear characteristics to generate a mixed signal containing multiple frequency components such as sum frequency and difference frequency. After subsequent filtering, amplification and other circuit processing, an error signal related to the frequency deviation is extracted from these mixed signals, and further processed to obtain a feedback signal.

[0041] Feedback Regulation Module:

[0042] like Figure 1 As shown, the microprocessor inside the servo controller (14) runs a specially written control algorithm program. The program should be designed according to the system's requirements for frequency stabilization and the characteristics of the feedback signal. The storage unit should pre-store the algorithm program, control parameters and relevant data during the system operation process, such as the initially set frequency reference value, etc. The communication interface should ensure stable and reliable data transmission between the drive circuit board (12). The signal amplifier circuit in the drive circuit board (12) amplifies the control command signal from the servo controller (14). The amplification factor should be reasonably set according to the signal strength required for PZT and laser driving. The power drive circuit provides a suitable voltage signal to the PZT based on the amplified signal, so that the PZT produces a corresponding deformation to adjust the cavity length of the FP cavity (11). At the same time, the drive circuit board (12) should also have the function of adjusting the working parameters of the laser, such as changing the laser frequency by controlling the driving current of the laser.

[0043] Frequency Monitoring System:

[0044] like Figure 1As shown, in the laser frequency short-time monitoring system, the optical collimator (18) collimates the laser output from the optical fiber into a parallel beam and transmits it to the frequency monitor (19). The frequency monitor (19) should work based on a suitable optical interference principle or other frequency measurement principle, such as using a Michelson interferometer structure or a heterodyne interferometer measurement principle to monitor the laser frequency in real time. The monitored data is transmitted to a computer (20) via a data line. The computer (20) runs a special monitoring software, which should have data acquisition, processing, display and storage functions, and analyzes the data transmitted by the frequency monitor (19) to realize the monitoring of the short-time stability performance of the laser frequency.

[0045] In the laser frequency long-term monitoring system, the optical collimator (18) also collimates the laser and then acts on PD 2 (22) together with the reference laser (21). The reference laser (21) should have a stable frequency characteristic, and a laser with a stable atomic transition frequency can be selected as a reference source. PD 2 (22) detects the frequency difference signal between the laser and the reference laser (21), and the frequency counter (23) counts and analyzes the frequency difference signal. Through long-term counting and statistics, the long-term stability performance of the laser frequency is monitored, providing data support for the evaluation and optimization of the frequency stabilization effect of the entire system.

[0046] 2. Frequency Stabilization Operation Process

[0047] like Figure 2 As shown, after the frequency-stabilized laser (1) is started, a laser beam is emitted, and the laser passes through the optical isolator (2). The optical isolator (2) prevents the reflected light from being transmitted in the reverse direction, thereby ensuring that the laser is output unidirectionally to the half-wave plate 1 (3) and the PBS 1 (4);

[0048] After polarization splitting, one path of the laser light enters the optical collimator (18) for subsequent frequency monitoring, and the other path of the laser light is split again by passing through a 45° laser reflector 1 (6), a 45° laser reflector 2 (7), a half wave plate 3 (8) and a PBS 2 (9), and one beam of the light enters a quarter wave plate (10) and then enters the FP cavity (11);

[0049] In the FP cavity (11), the laser is reflected and transmitted, and the reflected carrier and the modulated sideband pass through the quarter-wave plate (10) again and are reflected by the PBS II (9) and enter the PD I (13), and the PD I (13) generates a beat frequency signal of the reflected carrier and the modulated sideband;

[0050] At the same time, the direct digital frequency synthesizer (17) generates a demodulation signal (16), which is mixed and demodulated with the beat frequency signal of PD-1 (13) in the mixer (15) after phase shifting, and a feedback signal is obtained after circuit operation processing;

[0051] The feedback signal is transmitted to a servo controller (14), and the servo controller (14) analyzes and processes the signal according to an algorithm program, generates a control instruction, and transmits the control instruction to a driving circuit board (12) through a communication interface;

[0052] The driving circuit board (12) adjusts the laser frequency by adjusting the laser driving current and other working parameters according to the control instruction, and applies voltage to the PZT to deform the PZT to adjust the cavity length of the FP cavity (11), thereby realizing dual-parameter frequency stabilization.

[0053] During the frequency stabilization process, the laser frequency short-time monitoring system and the laser frequency long-time monitoring system work continuously. The frequency monitor (19) in the laser frequency short-time monitoring system monitors the laser frequency in real time, and the data is transmitted to the computer (20) for short-time performance analysis. The PD 2 (22) in the laser frequency long-time monitoring system detects the frequency difference signal between the laser and the reference laser (21), and the frequency counter (23) counts and analyzes it to provide a basis for the long-term frequency stabilization performance evaluation of the system. By continuously adjusting the laser frequency and the FP cavity length, the system output laser frequency remains stable.

[0054] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A method for frequency stabilization based on PDH dual parameters, characterized in that: The method comprises the following steps: Step 1: The frequency-stabilized laser (1) emits laser light, which is then outputted by the optical isolator (2) and then polarized by a half-wave plate (3) and a PBS (4). One path is used for frequency monitoring through an optical collimator (18), and the other path is inputted through a 45° laser reflector (6) and a 45° laser reflector (7) to a half-wave plate (8) and a PBS (9) for polarization splitting again. Step 2: After the light beam is split again in step 1, it passes through a quarter wave plate (10) and then enters the FP cavity (11). The reflected carrier and the modulated sideband of the FP cavity (11) pass through the quarter wave plate (10) again, and after a phase delay of π / 2, it is reflected by PBS 2 (9) into PD 1 (13) to obtain the beat frequency signal of the reflected carrier and the modulated sideband; Step 3: The direct digital frequency synthesizer (17) generates a demodulated signal (16) of the same path, which is phase-shifted and connected to the mixer (15) and the beat signal received by PD-1 (13) for demodulation, and a feedback signal is obtained after further circuit operation processing; Step 4: Use the feedback signal obtained in step 3 to adjust the laser and PZT respectively to perform dual parameter frequency stabilization, wherein the collimator (18) optical fiber output laser and the frequency monitor (19) and the computer (20) constitute a laser frequency short-time monitoring system, and the optical collimator (18) optical fiber output laser and the reference laser (21), PD 2 (22), and the frequency counter (23) constitute a laser frequency long-time monitoring system.

2. The method for frequency stabilization based on PDH dual parameters according to claim 1, characterized in that: In step one, the laser light emitted by the laser to be stabilized (1) is output after passing through an optical isolator (2). The optical isolator (2) controls the propagation direction of the laser light through a combination of internal optical elements, including a polarizer to select the polarization direction and a Faraday rotator to achieve non-reciprocal rotation, so as to isolate the interference of reflected light and ensure the stability and unidirectionality of the laser output.

3. The method for frequency stabilization based on PDH dual parameters according to claim 1, characterized in that: In step 2, the quarter wave plate (10) causes the reflected carrier and the modulated sideband to produce phase changes when the laser enters and leaves the FP cavity (11). The difference in refractive index for light in different polarization directions causes different optical paths to produce phase differences. The phase difference affects the reflection and transmission characteristics of the laser in the FP cavity (11), and after being reflected by PBS 2 (9), it enters PD 1 (13) to form a beat frequency signal.

4. The method for frequency stabilization based on PDH dual parameters according to claim 1, characterized in that: In step three, the demodulation signal (16) generated by the direct digital frequency synthesizer (17) has adjustable parameters. It is generated through the frequency division and phase accumulation operation of the internal digital circuit, and after being phase-shifted by the phase shift circuit, it is mixed and demodulated with the beat signal received by the PD-1 (13) in the mixer (15). The mixer (15) uses nonlinear elements to multiply to generate multiple frequency component output signals, and the feedback signal is obtained through circuit operation processing such as filtering.

5. The method for frequency stabilization based on PDH dual parameters according to claim 1, characterized in that: In step 4, the feedback signal is used to adjust the laser frequency and PZT. When the laser frequency is adjusted, the feedback signal is transmitted to the drive circuit, and the drive circuit changes the internal working parameters of the laser by changing the injection current, adjusting the working temperature, etc. When the PZT is adjusted, the feedback signal is transmitted to the drive circuit, and the drive circuit applies a voltage to the PZT to deform it and change the cavity length of the FP cavity (11), thereby realizing dual-parameter frequency stabilization.

6. A system based on PDH and dual parameter frequency stabilization, comprising the method for PDH dual parameter frequency stabilization according to any one of claims 1 to 5, characterized in that: The system includes: Laser emission and light splitting module: comprising a laser to be stabilized (1), an optical isolator (2), a half wave plate 1 (3), a PBS 1 (4), a half wave plate 2 (5), a 45° laser reflector 1 (6), a 45° laser reflector 2 (7), a half wave plate 3 (8) and a PBS 2 (9), for emitting laser light and performing multiple polarization splitting; The frequency modulation and monitoring module comprises a quarter wave plate (10), an FP cavity (11), a PD-1 (13), a direct digital frequency synthesizer (17), a mixer (15) and a demodulation signal (16), and is used to perform frequency modulation on the laser, obtain a beat frequency signal and perform demodulation to obtain a feedback signal; Feedback adjustment module: comprising a driving circuit board (12), a servo controller (14) and a PZT, and used for adjusting the laser and the PZT respectively according to the feedback signal; The frequency monitoring system includes a short-time laser frequency monitoring system, which is composed of an optical collimator (18), a frequency monitor (19) and a computer (20), and a long-time laser frequency monitoring system, which is composed of an optical collimator (18), a reference laser (21), PD II (22) and a frequency counter (23).

7. A system based on PDH dual parameter frequency stabilization according to claim 6, characterized in that: In the laser emission and light splitting module, an optical isolator (2) cooperates with a laser to be stabilized (1), an input port of the optical isolator (2) is aligned with an output port of the laser to be stabilized (1), an internal polarizer and a Faraday rotator are arranged to realize unidirectional laser transmission, a half wave plate (3) and a PBS (4) are arranged in sequence, the half wave plate (3) rotates to adjust the polarization state to match the light splitting characteristics of the PBS (4), a 45° laser reflector (6) and a 45° laser reflector (7) subsequently change the light propagation direction, a half wave plate (8) and a PBS (9) are polarized and split again, and each optical element works in coordination to realize laser light splitting.

8. A system based on PDH dual parameter frequency stabilization according to claim 6, characterized in that: In the frequency modulation and monitoring module, a quarter wave plate (10) is located in the incident and outgoing optical paths of the FP cavity (11). Its special optical structure causes a phase difference in the laser polarization component to change the reflection and transmission characteristics in the cavity to generate reflected light. A direct digital frequency synthesizer (17) generates a demodulation signal (16) through an internal digital circuit and a clock signal source, which is mixed and demodulated in a mixer (15) with a beat signal received by a PD-1 (13). The nonlinear elements of the mixer (15) are multiplied to generate a mixed signal, which is processed by a subsequent circuit to obtain a feedback signal.

9. A system based on PDH dual parameter frequency stabilization according to claim 6, characterized in that: In the feedback adjustment module, the internal microprocessor of the servo controller (14) runs the algorithm program, the storage unit stores data, the communication interface transmits data with the driving circuit board (12), the signal amplification circuit of the driving circuit board (12) amplifies the signal, and the power driving circuit provides voltage to the PZT to deform it to adjust the cavity length of the FP cavity (11), and adjust the laser working parameters at the same time. The various components of the frequency monitoring system cooperate, the optical collimator (18) collimates the laser, the frequency monitor (19) monitors the frequency and transmits data to the computer (20), the reference laser (21) and the monitored laser act on PD II (22) to generate a frequency difference signal, which is processed by the frequency counter (23) to provide data support for the system.

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