Device for improving frequency stabilization precision of cross-saturated absorption spectrum

Abstract

The invention discloses a device for improving frequency stabilization precision of a cross-saturated absorption spectrum. The device comprises a single-frequency laser, a light splitting coupler, an optical frequency comb preparation system, an atom / molecule gas chamber, a frequency discrimination system and a servo system. According to the frequency stabilization system, a single-frequency laser is mainly used as a frequency stabilization object, after laser passes through a light splitting coupler, one light beam serves as output light, the other light beam enters an optical frequency comb preparation system, and the comb tooth frequency interval of the optical frequency comb is matched with the atomic excited state energy level frequency difference. The center frequency of the atom / molecule cross saturated absorption line provides absolute frequency reference; laser passing through the atom / molecule gas chamber carries cross saturation absorption spectrum signals, and error signals are obtained after the signals pass through the frequency discrimination system and fed back to the single-frequency laser through the servo system to achieve frequency stabilization. The comb tooth frequency interval of the optical frequency comb is matched with the atomic excited state energy level frequency difference, so that the interaction efficiency of laser and atoms / molecules is improved, a frequency stabilization error signal with higher precision is obtained, and the laser frequency stabilization performance is effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of laser frequency stabilization technology and relates to a device for improving the frequency stabilization accuracy of cross-saturated absorption spectra. Background Technology

[0002] Single-frequency lasers are lasers that output light in a single longitudinal mode (single frequency). They are characterized by low noise and long coherence length, and have significant application prospects in fields such as precision atomic spectroscopy, coherent lidar, high-power coherent combining, and magnetic field detection. However, simple single-frequency lasers are susceptible to frequency jitter and drift caused by external mechanical vibrations, temperature fluctuations, or internal equipment noise, which limits their application in precision atomic spectroscopy and magnetic field detection.

[0003] Laser frequency locking to the absolute absorption spectral lines of atoms / molecules is one of the fundamental methods for laser frequency stabilization. Saturated absorption spectroscopy is a technique for obtaining high-resolution atomic absorption spectra by eliminating Doppler broadening. Its spectral linewidth is determined by the natural linewidth of the atomic energy levels and the laser intensity. It is a typical method for monitoring atomic and molecular transitions and is widely used for laser frequency stabilization. Cross-saturated absorption spectroscopy is a type of saturated absorption spectroscopy. The difference lies in the fact that, for a specific velocity atom, the pump light and probe light resonate at different energy levels with the atom. That is, the pump light excites the atom to one excited state energy level, while the probe light probes the atom to another excited state energy level. Compared to ordinary saturated absorption spectroscopy, cross-saturated absorption spectroscopy has extremely high spectral resolution, no background detection noise, and can provide additional quantum state information. Therefore, it can be used in research fields such as hyperfine structure measurement, Zeeman / Stark effect, molecular vibration-rotation spectroscopy, quantum information, and quantum optics.

[0004] However, the pump light, probe light, and atomic resonance have different energy levels, and the transition intensities between different energy levels are different. This results in a weak cross-pump-probe effect, which leads to a low intensity of the cross-saturated absorption spectrum and makes it difficult to obtain an effective frequency stabilization error signal, resulting in poor frequency stabilization performance.

[0005] Common methods for enhancing absorption spectroscopy include multiple reflection enhancement in atomic / molecular gas cells, optimizing the power ratio of pump light and probe light, and controlling the laser linewidth to match the absorption spectrum.

[0006] Atom / molecular gas cell multiple reflection enhancement technology enhances the interaction between the laser and atoms / molecules by constructing a reflective device that allows the pump light and probe light to be reflected multiple times within the atomic / molecular gas cell, thereby boosting the signal intensity of the saturated absorption spectrum. For example, a method for achieving saturated absorption spectroscopy based on multiple reflections is disclosed (CN108645816B). However, this method requires both forward-incident pump light and backward-incident absorber light to interact with the atomic / molecular gas, while also requiring precise control of the overlap and matching of the pump and probe light. These requirements pose significant challenges to the design and operation of the reflective device structure and make the system susceptible to environmental disturbances, reducing its robustness and frequency stabilization accuracy.

[0007] Optimizing the power ratio of pump and probe beams in frequency stabilization not only enhances the interaction between the laser and atomic / molecular gases by controlling the relative intensity of the pump and probe beams in the spectral frequency stabilization process, but also avoids signal degradation caused by power broadening. This can be used to obtain an optimized frequency stabilization signal-to-noise ratio, such as the disclosed all-fiber link saturated absorption spectral frequency stabilization device (CN118263767A). However, this method requires separate control of the laser intensity of the pump and probe beams. On the one hand, it requires the introduction of two laser intensity control devices, which increases the complexity of the frequency stabilization system. On the other hand, the intensity control method can only improve the frequency stabilization error signal intensity to a limited extent and is difficult to improve the effect of cross-pump-probe interaction.

[0008] The method of adjusting the laser linewidth to match the absorption spectrum width achieves matching between the laser linewidth and the error signal spectrum width, thereby capturing the signal of the interaction between atoms / molecules and the laser to the maximum extent and obtaining a higher zero-crossing slope of the error signal. This effectively enhances the accuracy of the frequency stabilization error signal and improves the frequency stabilization performance, as exemplified by a device and method for improving laser frequency stabilization accuracy (CN116780328A). However, this method is only applicable to pump-probe interactions between the laser and atomic / molecular gases at the same energy level, and it is difficult to achieve the same effect for cross-pump-probe interactions at different energy levels.

[0009] In summary, current common methods for enhancing absorption spectroscopy are insufficient to effectively improve the cross-pumping-probe interaction between lasers and atomic / molecular gases. Therefore, there is an urgent need to study a device and method to improve the frequency stabilization accuracy of cross-saturated absorption spectra, thereby promoting the development and application of novel frequency-stabilized lasers. Summary of the Invention

[0010] The purpose of this invention is to propose a device for improving the frequency stabilization accuracy of cross-saturated absorption spectra, thereby further expanding the application fields of frequency-stabilized lasers. By utilizing an optical frequency comb fabrication system, the frequency spacing of the comb teeth is matched to the frequency difference of the excited state energy levels of atoms, enhancing the signal of the interaction between atoms / molecules and the laser. This results in a higher zero-crossing slope of the error signal, effectively improving the accuracy of the frequency stabilization error signal and thus enhancing the frequency stabilization performance.

[0011] The objective of this invention is achieved by at least one of the following technical solutions.

[0012] A device for improving the frequency stabilization accuracy of cross-saturated absorption spectra includes a single-frequency laser, a beam splitter, an optical frequency comb fabrication system, an atomic / molecular gas cell, a frequency discrimination system, and a servo system;

[0013] The single-frequency laser is connected to a beam splitter coupler. After passing through the beam splitter coupler, the laser outputs two beams. One beam is used as the output of the frequency-stabilized laser for back-end applications, while the other beam enters the optical frequency comb fabrication system to fabricate the optical frequency comb. The frequency spacing of the optical frequency comb teeth matches the frequency difference of the excited state energy levels of the atoms. The output of the optical frequency comb is sent to the atomic / molecular gas cell. The laser passing through the atomic / molecular gas cell carries a cross-saturated absorption spectrum signal. The cross-saturated absorption spectrum signal is processed by a frequency discrimination system to obtain an error signal, which is then fed back to the single-frequency laser through a servo system to achieve frequency stabilization.

[0014] Furthermore, the gain medium of the single-frequency laser includes optical fiber, solid, semiconductor, or gas, and the operating mode of the single-frequency laser is continuous, pulsed, or quasi-continuous operation.

[0015] Furthermore, the splitting ratio of the beam splitter is any value between 1:99 and 99:1.

[0016] Furthermore, the optical frequency comb fabrication system uses intensity modulation, phase modulation, or a combination of both to generate the optical frequency comb teeth.

[0017] Furthermore, the modulation signals of the optical frequency comb fabrication system include sine waves, triangular waves, and time-frequency transformation signals. By adjusting the comb tooth control parameters, the frequency interval of the optical frequency comb teeth is matched with the frequency difference of the excited state energy levels of atoms, thereby improving the efficiency of laser-atomic / molecular interaction.

[0018] Furthermore, the atomic / molecular gas chamber contains one or more gases selected from He, Rb, K, Cs, CH4, H2O, CO2, and CH3Cl.

[0019] Furthermore, the gas pressure in the atomic / molecular gas chamber is any value within the range of 0.01 Pa to 10 MPa, and the length of the gas chamber is any value within the range of 0.001 m to 100 m.

[0020] Furthermore, the frequency discrimination system uses cross-saturation spectral signals including one or more of the following: cross-saturation absorption spectrum based on cross-saturation absorption lines, polarization spectrum, frequency modulation spectrum, or modulation transfer spectrum.

[0021] Furthermore, the frequency discrimination system includes a photodetector, a bandpass filter, and a lock-in amplifier. The cross-saturated absorption spectrum signal is converted into an electrical signal by the photodetector. The electrical signal passes through the bandpass filter to reduce interference from other signals, and is then transmitted to the lock-in amplifier to output an error signal for the laser frequency fluctuation.

[0022] Furthermore, the servo system includes a proportional-integral-derivative (PID) controller, a signal adder, and a high-voltage amplifier. The error signal is transmitted to the PID controller for processing and then transmitted to the single-frequency laser through the signal adder and the high-voltage amplifier to achieve closed-loop locking and improve the laser frequency stabilization performance.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] This invention primarily uses a single-frequency laser as the target for frequency stabilization. After passing through a beam splitter, one beam of laser light is output, while the other enters an optical frequency comb fabrication system. The frequency interval of the optical frequency comb teeth matches the frequency difference of the excited state energy levels of atoms. The optical frequency comb outputs to an atomic / molecular gas cell. The laser light passing through the atomic / molecular gas cell carries a cross-saturated absorption spectrum signal. After passing through a frequency discrimination system, an error signal is obtained and fed back to the single-frequency laser through a servo system to achieve frequency stabilization. By matching the frequency interval of the optical frequency comb teeth to the frequency difference of the excited state energy levels of atoms, the interaction efficiency between the laser and atoms / molecules is improved, and a higher precision frequency stabilization error signal is obtained, thereby effectively improving the laser frequency stabilization performance.

[0025] This invention, utilizing a beam splitter, ensures that only the frequency-stabilized laser is modulated by an optical frequency comb under the initial laser conditions. Through an optical frequency comb fabrication system, the frequency spacing of the comb teeth matches the frequency difference of the excited-state energy levels of atoms, enhancing the frequency-stabilized signal of the cross-saturated absorption spectrum of the interaction between atoms / molecules and the laser. This results in a higher zero-crossing slope for the error signal, effectively improving the accuracy of the frequency stabilization error signal and achieving higher frequency stabilization performance than under the original laser conditions. Furthermore, this technology can be superimposed on other technologies and is expected to break through existing limits in frequency stabilization performance. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following description is provided with accompanying drawings of the relevant technical solutions in the embodiments of the present invention or the prior art. It should be understood that the accompanying drawings described below are only for the purpose of clearly illustrating some embodiments of the technical solutions of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a diagram of a device for improving the frequency stabilization accuracy of cross-saturated absorption spectra, as shown in the embodiment.

[0028] Figure 2 The image shows the initial laser and the modulated optical frequency comb diagram for this embodiment.

[0029] Figure 3 The image shows a comparison of the initial laser and optical frequency comb frequency stabilization error signals in the example.

[0030] Figure 4 The diagram shows the frequency stabilization result of the optical frequency comb in the example.

[0031] Figure reference numerals: 1-Single-frequency laser, 2-Optical splitter coupler, 3-Optical frequency comb preparation system, 4-Atom / molecular gas cell, 5-Frequency discrimination system, 6-Servo system. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be noted that the scope of protection of the present invention is not limited to the scope described in the embodiments.

[0033] like Figure 1As shown, this embodiment of a device for improving the frequency stabilization accuracy of cross-saturated absorption spectra includes a single-frequency laser 1, a beam splitter 2, an optical frequency comb fabrication system 3, an atomic / molecular gas cell 4, a frequency discrimination system 5, and a servo system 6. The single-frequency laser 1 is connected to the beam splitter 2, and the single-frequency laser 1 is used as the target for frequency stabilization. After passing through the beam splitter 2, the laser outputs two beams. One beam (beam b) serves as the output of the frequency-stabilized laser for downstream applications (such as precision atomic spectroscopy, coherent lidar, high-power coherent combining, magnetic field detection, etc.), while the other beam (beam a) is used for laser frequency stabilization. The laser used for frequency stabilization enters the optical frequency comb fabrication system 3 to fabricate the optical frequency comb. The optical frequency comb fabrication system 3 includes an arbitrary waveform generator, a signal amplifier, and a polarization-maintaining phase modulator. The frequency interval of the optical frequency comb teeth matches the frequency difference of the excited state energy levels of the atoms, and the optical frequency comb is output to the atomic / molecular gas cell 4. The laser passing through the atomic / molecular gas cell 4 carries the cross-saturated absorption spectral signal, and the atomic / molecular gas cell... The center frequency of the cross-saturated absorption spectral lines of atoms / molecules in the molecular gas cell 4 provides an absolute frequency reference. An optical frequency comb passes through the atomic / molecular gas cell 4 to obtain a cross-saturated absorption spectral signal. This cross-saturated absorption spectral signal is then processed by the frequency discrimination system 5 to obtain an error signal. The frequency discrimination system 5 includes a photodetector, a bandpass filter, and a lock-in amplifier. In the frequency discrimination system 5, the cross-saturated absorption spectral signal is converted into an electrical signal by the photodetector. This electrical signal passes through the bandpass filter to reduce interference from other signals and is then transmitted to the lock-in amplifier to output the error signal. The error signal is then fed back to the single-frequency laser 1 through the servo system 6 to achieve frequency stabilization. The servo system 6 includes a proportional-integral-differential controller, a signal adder, and a high-voltage amplifier. In the servo system 6, the error signal is transmitted to the proportional-integral-differential controller for processing and then applied to the piezoelectric ceramic of the single-frequency laser 1 through the signal adder and the high-voltage amplifier to achieve tuning of the single-frequency laser 1.

[0034] In one specific embodiment, the gain medium of the single-frequency laser 1 includes optical fiber, solid, semiconductor or gas, and the operating mode of the single-frequency laser 1 is continuous, pulsed or quasi-continuous operation.

[0035] In one specific embodiment, the splitting ratio of the beam splitter 2 is any value between 1:99 and 99:1.

[0036] In one specific embodiment, the optical frequency comb preparation system 3 uses intensity modulation, phase modulation, or a combination of both to generate the optical frequency comb teeth.

[0037] In one specific embodiment, the modulation signal of the optical frequency comb preparation system 3 includes a sine wave, a triangular wave, and a time-frequency conversion signal. By adjusting the comb tooth control parameters, the frequency interval of the optical frequency comb teeth is matched with the frequency difference of the excited state energy level of the atom, thereby improving the interaction efficiency between the laser and atoms / molecules.

[0038] In one specific embodiment, the atomic / molecular gas chamber 4 contains one or more gases selected from He, Rb, K, Cs, CH4, H2O, CO2, and CH3Cl.

[0039] In one specific embodiment, the gas pressure in the atomic / molecular gas chamber 4 is any value within the range of 0.01 Pa to 10 MPa, and the length of the gas chamber is any value within the range of 0.001 m to 100 m.

[0040] In one specific embodiment, the frequency discrimination system 5 uses a cross-saturation spectral signal that includes one or more of the following: cross-saturation absorption spectrum based on cross-saturation absorption lines, polarization spectrum, frequency modulation spectrum, or modulation transfer spectrum.

[0041] In one specific embodiment, the frequency discrimination system 5 includes a photodetector, a bandpass filter, and a lock-in amplifier. The cross-saturated absorption spectrum signal is converted into an electrical signal by the photodetector. The electrical signal passes through the bandpass filter to reduce interference from other signals and is then transmitted to the lock-in amplifier to output an error signal for the laser frequency fluctuation.

[0042] In one specific embodiment, the servo system 6 includes a proportional-integral-derivative controller, a signal adder, and a high-voltage amplifier. The error signal is transmitted to the proportional-integral-derivative controller for processing, and then transmitted to the single-frequency laser through the signal adder and the high-voltage amplifier to achieve closed-loop locking and improve the laser frequency stabilization performance.

[0043] Example 2

[0044] This embodiment provides a device for improving the frequency stabilization accuracy of cross-saturated absorption spectra, comprising a single-frequency laser 1, a beam splitter 2, an optical frequency comb fabrication system 3, an atomic / molecular gas cell 4, a frequency discrimination system 5, and a servo system 6; the single-frequency laser 1 is a 1083nm single-frequency fiber laser, and the atomic / molecular gas cell 4 uses a gas cell that is... 4 The He atom gas chamber, the frequency discrimination system 5 uses a stable absorption spectrum of D. 12 Cross-saturated absorption spectrum.

[0045] The 1083nm single-frequency fiber laser is connected to the beam splitter 2. Using the 1083nm single-frequency fiber laser as the frequency stabilization target, the laser outputs two beams after passing through the beam splitter 2. One beam serves as the output of the frequency-stabilized laser for downstream applications, while the other beam is used for laser frequency stabilization. The laser used for frequency stabilization enters the optical frequency comb fabrication system 3 to fabricate the optical frequency comb. The optical frequency comb fabrication system 3 is implemented by a laser linewidth control device, which includes an arbitrary waveform generator, a signal amplifier, and a polarization-maintaining phase modulator. The frequency spacing of the optical frequency comb teeth matches the frequency difference of the atomic excited-state energy levels, and the optical frequency comb is output to the... 4 He atom gas chamber, after the aforementioned 4 The laser in the He atom gas cell carries a cross-saturated absorption spectral signal. 4 The center frequencies of the atomic / molecular cross-saturated absorption spectral lines in the He atomic gas cell provide an absolute frequency reference; the optical frequency comb passes through the aforementioned... 4 The He atom gas cell obtains a cross-saturated absorption spectrum signal, and the cross-saturated absorption spectrum signal can be used to obtain an error signal through the frequency discrimination system 5.

[0046] The frequency discrimination system 5 includes a photodetector, a bandpass filter, and a lock-in amplifier. In the frequency discrimination system 5, the cross-saturated absorption spectrum signal is converted into an electrical signal by the photodetector. The electrical signal passes through the bandpass filter to reduce interference from other signals and is then transmitted to the lock-in amplifier to output an error signal. The error signal is fed back to the single-frequency laser 1 through the servo system 6 to achieve frequency stabilization. The servo system 6 includes a proportional-integral-derivative controller, a signal adder, and a high-voltage amplifier. In the servo system 6, the error signal is transmitted to the proportional-integral-derivative controller for processing and is applied to the piezoelectric ceramic of the single-frequency laser 1 through the signal adder and the high-voltage amplifier to achieve tuning of the single-frequency laser 1.

[0047] In this embodiment, the initial laser is as follows: Figure 2 As shown in (a), the energy level frequency difference between the excited states of the D1 and D2 transition spectral lines is 2.291 GHz. The optical frequency comb fabrication system 3 uses a 2.291 GHz sine wave to phase modulate the laser, and the result of the modulated optical frequency comb is as follows. Figure 2 (b). For example Figure 3 As shown, when using the initial laser for frequency stabilization, the error signal slope is 2.9 mV / MHz; when using an optical frequency comb for frequency stabilization, the error signal slope increases to 5.2 mV / MHz. After using the initial laser for frequency stabilization, the frequency drift is ±150 kHz, and the root mean square of the frequency drift is 59.9 kHz. Figure 4 The initial laser frequency stabilization result shown in (a) is as follows: Figure 4(b) shows the frequency stabilization results using an optical frequency comb. After frequency stabilization using an optical frequency comb, the frequency drift decreased to ±65kHz, and the root mean square frequency drift decreased to 23.1kHz, significantly improving the frequency stabilization performance.

[0048] In summary, this invention uses a single-frequency laser 1 as the target for frequency stabilization. After passing through the beam splitter 2, one beam is output, while the other enters the optical frequency comb preparation system 3. The frequency interval of the optical frequency comb teeth matches the frequency difference of the excited state energy levels of atoms. The optical frequency comb outputs to the atomic / molecular gas cell 4. The laser passing through the atomic / molecular gas cell 4 carries a cross-saturated absorption spectrum signal. After passing through the frequency discrimination system 5, the signal obtains an error signal, which is then fed back to the single-frequency laser through the servo system 6 to achieve frequency stabilization. This invention mainly uses the optical frequency comb to enhance the interaction between atoms / molecules and the laser, effectively improving the zero-crossing slope of the frequency stabilization error signal, thereby improving the frequency stabilization performance.

[0049] Although embodiments of the apparatus of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

[0050] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the above embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A device for improving the frequency stabilization accuracy of cross-saturated absorption spectra, characterized in that, It includes a single-frequency laser (1), a beam splitter (2), an optical frequency comb fabrication system (3), an atomic / molecular gas cell (4), a frequency discrimination system (5), and a servo system (6); Among them, the single-frequency laser (1) is connected to the beam splitter (2). After the laser passes through the beam splitter (2), it outputs two laser beams. One beam is used as the output of the frequency stabilizer laser for back-end applications, and the other beam enters the optical frequency comb preparation system (3) to realize the preparation of the optical frequency comb. The frequency interval of the optical frequency comb teeth matches the frequency difference of the excited state energy level of the atom. The optical frequency comb is output to the atom / molecular gas cell (4). The laser passing through the atom / molecular gas cell (4) carries the cross-saturated absorption spectrum signal. The cross-saturated absorption spectrum signal is obtained by the frequency discrimination system (5) and fed back to the single-frequency laser (1) through the servo system (6) to realize frequency stabilization.

2. The device for improving the frequency stabilization accuracy of cross-saturated absorption spectra according to claim 1, characterized in that: The gain medium of the single-frequency laser (1) includes optical fiber, solid, semiconductor or gas, and the operating mode of the single-frequency laser (1) is continuous, pulsed or quasi-continuous operation.

3. The device for improving the frequency stabilization accuracy of cross-saturated absorption spectra according to claim 1, characterized in that: The splitting ratio of the beam splitter (2) is any value between 1:99 and 99:

1.

4. The device for improving the frequency stabilization accuracy of cross-saturated absorption spectra according to claim 1, characterized in that: The optical frequency comb preparation system (3) uses intensity modulation, phase modulation or a combination of both to generate optical frequency comb teeth.

5. The device for improving the frequency stabilization accuracy of cross-saturated absorption spectra according to claim 1, characterized in that: The modulation signals in the optical frequency comb preparation system (3) include sine waves, triangular waves, and time-frequency conversion signals. By adjusting the comb tooth control parameters, the frequency interval of the optical frequency comb teeth is matched with the frequency difference of the excited state energy level of the atom, thereby improving the efficiency of the interaction between the laser and atoms / molecules.

6. The device for improving the frequency stabilization accuracy of cross-saturated absorption spectra according to claim 1, characterized in that: The atomic / molecular gas chamber (4) contains one or more gases selected from He, Rb, K, Cs, CH4, H2O, CO2, and CH3Cl.

7. The device for improving the frequency stabilization accuracy of cross-saturated absorption spectra according to claim 1, characterized in that: The gas pressure in the atomic / molecular gas chamber (4) is any value in the range of 0.01 Pa to 10 MPa, and the length of the gas chamber is any value in the range of 0.001 m to 100 m.

8. The device for improving the frequency stabilization accuracy of cross-saturated absorption spectra according to claim 1, characterized in that: The frequency discrimination system (5) uses cross-saturated spectral signals including one or more of the following: cross-saturated absorption spectrum based on cross-saturated absorption spectral lines, polarization spectrum, frequency modulation spectrum, or modulation transfer spectrum.

9. The device for improving the frequency stabilization accuracy of cross-saturated absorption spectra according to claim 1, characterized in that: The frequency discrimination system (5) includes a photodetector, a bandpass filter and a lock-in amplifier. The cross-saturated absorption spectrum signal is converted into an electrical signal by the photodetector. The electrical signal passes through the bandpass filter to reduce interference from other signals and is then transmitted to the lock-in amplifier to output an error signal for the laser frequency fluctuation.

10. The method for improving the frequency stabilization accuracy of cross-saturated absorption spectra according to claim 1, characterized in that: The servo system (6) includes a proportional-integral-derivative controller, a signal adder, and a high-voltage amplifier. The error signal is transmitted to the proportional-integral-derivative controller for processing and then transmitted to the single-frequency laser (1) through the signal adder and the high-voltage amplifier to achieve closed-loop locking and improve the laser frequency stabilization performance.

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