A system and method for power stabilization optimization of continuous wave Ti:sapphire lasers based on a three-mirror-mode cleaner.

Abstract

This invention discloses a power stabilization optimization system and method for a continuous-wave Ti:sapphire laser based on a three-mirror mode cleaner. The system includes: the output beam of the Ti:sapphire laser is adjusted by a front-end optical path system; at the input mirror of the mode cleaner, a photodetector at the reflecting end receives optical power fluctuations, converts them into voltage signals, and transmits them to an optical power simulation control unit. The simulation control unit generates a driving voltage for an RF driver based on the power fluctuations, thereby driving an acousto-optic modulator to adjust the diffraction efficiency and stabilize the output power. During power stabilization, the cavity length of the mode cleaner needs to be adjusted using an electro-optic modulator. Compared with ordinary photoelectric feedback methods, this invention uses a mode cleaner instead of ordinary beam splitters, which can reduce photocurrent while maintaining the same noise level, further improving the noise suppression level of the power stabilization system and improving the stability of the output optical power.

Description

Technical Field

[0001] This invention belongs to the field of continuous wave Ti:Sapphire laser power stabilization systems, specifically relating to a continuous wave Ti:Sapphire laser power stabilization optimization system and method based on a three-mirror mode cleaner. Background Technology

[0002] Precision quantum measurements, such as atomic clocks for precise timekeeping, quantum weak magnetic field measurements, and atomic spin gyroscopes, all require high-power, highly stable lasers as pump light sources. Continuous-wave Ti:sapphire lasers are widely used in these research fields due to their advantages, including high beam quality, low noise, narrow linewidth, and strong tuning capability. Ti:sapphire lasers possess a wide radiation spectral range of 700–1000 nm and excellent transverse mode quality. Furthermore, their wavelength can be tuned to correspond to the transition absorption lines of various alkali metal atoms. As a superior laser source, it plays a crucial role in quantum precision measurements.

[0003] Taking inertial measurement as an example, in a laser pump system, the change in the pump light power directly affects the polarizability of the subsequent alkali metal atoms. Changes in the polarizability of alkali metal atoms affect their nuclear spin compensation capability and generate magnetic field fluctuation errors. This influences the pump error and frequency shift error of the longitudinal light, thus affecting the accuracy of the inertial measurement scaling factor. Therefore, suppressing laser power fluctuations is of great significance for improving the long-term stability of inertial measurements.

[0004] Current traditional power stabilization methods primarily involve splitting the laser beam into two beams using a beam splitter. One beam, with lower power, is detected by a photodetector and used for photoelectric feedback, while the other, with higher power, serves as the output laser. Feedback can be achieved through pump source current or temperature, or through external power suppressors such as electro-optic modulators or acousto-optic modulators. This photoelectric feedback method effectively suppresses power fluctuations, but due to the photocurrent threshold limitation of the photodetector, there is still room for optimization in power noise reduction. Summary of the Invention

[0005] To address the issue that in traditional Ti:sapphire laser power stabilization systems, the power feedback loop is limited by the photocurrent detected by the photodetector, leaving room for further optimization of power noise, this invention provides a continuous-wave Ti:sapphire laser power stabilization optimization system and method based on a three-mirror mode cleaner. This system can significantly reduce the feedback photocurrent while further suppressing the laser's frequency domain noise, thereby greatly optimizing the suppression performance of the power stabilization system.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A power stabilization optimization system for a continuous-wave Ti:sapphire laser based on a three-mirror mode cleaner includes an electro-optic modulator, a half-wave plate, a Glan-Taylor prism, an acousto-optic modulator, an aperture stop, a three-mirror mode cleaner, a photodetector, an analog adjustment circuit, a reference voltage generation circuit, and an RF driver.

[0008] The electro-optic modulator is used for adjusting the cavity length of the three-mirror cleaner;

[0009] The half-wave plate is used to adjust the polarization state of the incident laser.

[0010] The Glan-Taylor prism is used to further purify the polarization state of the incident laser.

[0011] The acousto-optic modulator is used to diffract the incident laser to generate 0th-order diffracted light and 1st-order diffracted light;

[0012] The aperture stop is used to intercept first-order diffracted light and allow 0th-order diffracted light to pass through.

[0013] The mold cleaner is used to feed back a portion of the laser power, further reducing the intensity noise of the laser.

[0014] The electro-optic modulator, half-wave plate, Glan-Taylor prism, acousto-optic modulator, aperture stop, and three-mirror mode cleaner are sequentially passed through the incident laser.

[0015] The photodetector, analog adjustment circuit, reference voltage generation circuit, and radio frequency driver together constitute a power feedback system, which generates a feedback voltage for laser power feedback.

[0016] Furthermore, the mode cleaner is an optical cavity with a cavity length of 1m, a precision of 1000, a linewidth of 308kHz, and a laser transmittance of 66%, composed of three optical lenses. The three lenses are two plane mirrors for input and output and one concave mirror for laser reflection. The input mirror splits the 0th order diffracted light. The incident laser is reflected at the input mirror, and the light inside the mode cleaner cavity is transmitted at the input mirror. The two beams are directly subtracted. Since the mode cleaner has a certain linewidth, high-frequency noise is preserved, and the feedback photocurrent signal is suppressed. This achieves the effect of suppressing higher amplitude noise under low photocurrent signal and outputting laser at the output mirror.

[0017] Furthermore, the analog adjustment circuit comprises three parts connected in sequence: a differential amplifier circuit, an analog PID adjustment circuit, and a post-amplifier circuit. The differential amplifier circuit is connected to the photodetector and the reference voltage generation circuit. The analog PID adjustment circuit adopts analog parallel PID adjustment. After being amplified and filtered by the post-amplifier, the output is sent to the RF driver. The RF driver is connected to the acousto-optic modulator for power modulation.

[0018] Furthermore, the reference voltage generation circuit includes a main control STM32 microcontroller and a digital-to-analog converter (DAC) circuit. The STM32 controls the DAC circuit to generate a variable reference voltage with a range of 0-5V. The reference voltage generation circuit is compared with the voltage obtained from the photodetector to obtain the feedback error.

[0019] This invention also discloses a method for power stabilization optimization of a continuous-wave Ti:sapphire laser based on a three-mirror mode cleaner, comprising the following steps:

[0020] Step 1: Adjust the output laser of the continuous wave Ti:sapphire laser to normal operating state. As input, it first passes through a half-wave plate and a Glan-Taylor prism to adjust the polarization state to the vertical direction and further purify it before being input into the acousto-optic modulator. Without applying a driving voltage, allow the laser to pass accurately through the aperture stop to ensure that the laser is collimated.

[0021] Step 2: Construct a three-mirror cleaner. The input and output mirrors are both placed at 45°. The laser passes through the center of the input and output mirrors, which are 20cm apart. Adjust the position and angle of the reflector so that the reflected light from the output mirror and the transmitted light from the input mirror coincide in the cavity to form resonance. The distance between the reflector and the center of the input and output mirrors is 40cm. Attach piezoelectric ceramic to the back of the reflector and connect it to the electro-optic modulator through a PDH cavity-locking system.

[0022] Step 3: Connect the photodetector to the subsequent analog control circuit, reference voltage generation circuit, and RF driver. By adjusting the variable resistor, obtain the PID parameters to stabilize the detection voltage at the reference voltage. Generate the driving voltage to the RF driver to control the acousto-optic modulator for diffraction efficiency control and stabilize the laser power.

[0023] The beneficial effects of this invention are as follows:

[0024] This invention reduces the photocurrent of the photodetector while maintaining a low noise level through a mode cleaner, further suppressing power noise in Ti:sapphire lasers and optimizing the performance of the Ti:sapphire laser power stabilization system. It generates a feedback voltage signal for the acousto-optic modulator through analog circuitry, where the analog PID control uses a parallel PID method to achieve complete decoupling of the P / I / D parameters. This invention avoids quantization errors caused by analog-to-digital conversion circuits, improving the accuracy and speed of the power feedback system. The mode cleaner reduces the detector photocurrent while maintaining a constant noise level. Compared to feedback after beam splitting, it can suppress more noise, especially high-frequency noise, at the same photocurrent level, showing broad application prospects in laser stabilization. Attached Figure Description

[0025] Figure 1This is a schematic diagram of the power stabilization optimization system for a continuous wave Ti:sapphire laser based on a three-mirror mode cleaner according to the present invention.

[0026] Figure 2 This is a schematic diagram of the mold cleaner structure used in this invention;

[0027] Figure 3 A schematic diagram illustrating the principle of reducing power noise in a mold cleaner;

[0028] Figure 4 This is a schematic diagram of the analog control and regulation circuit in this invention.

[0029] The attached figures are labeled as follows: 1. Continuous wave Ti:Sapphire laser; 2. Electro-optic modulator; 3. Half-wave plate; 4. Glan-Taylor prism; 5. Acousto-optic modulator; 6. Aperture stop; 7. Input mirror; 8. Photodetector; 9. Analog control circuit; 10. Reference voltage generation circuit; 11. Radio frequency driver; 12. Output mirror; 13. Reflector; 14. Piezoelectric ceramic. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0031] like Figure 1As shown, the continuous-wave Ti:sapphire laser power stabilization optimization system based on a three-mirror mode cleaner of the present invention includes an electro-optic modulator 2, a half-wave plate 3, a Glan-Taylor prism 4, an acousto-optic modulator 5, an aperture stop 6, an input mirror 7, a photodetector 8, an analog control circuit 9, a reference voltage generation circuit 10, an RF driver 11, an output mirror 12, a reflector 13, and a piezoelectric ceramic 14. The continuous-wave Ti:sapphire laser 1 generates the incident laser for the subsequent stabilization system, which is incident on the electro-optic modulator 2. The electro-optic modulator 2 is connected to the piezoelectric ceramic 14 via a PDH cavity-locking method, controlling the voltage of the piezoelectric ceramic 14 for cavity length adjustment of the three-mirror mode cleaner. After passing through the half-wave plate 3 and the Glan-Taylor prism 4, the polarization direction of the incident laser becomes vertical and the polarization state is further purified before entering the acousto-optic modulator 5. The acousto-optic modulator 5 separates the incident laser into 0th-order diffracted light and 1st-order diffracted light based on the Bragg diffraction principle. The light is filtered by aperture stop 6, which intercepts useless first-order diffracted light. The 0th-order diffracted light enters the input mirror 7 through the central aperture. The input mirror 7 is a plane mirror with a reflectivity of 99.6%. The output mirror 12 is also a plane mirror with a reflectivity of 99.6%. The input mirror 7, output mirror 12, reflector 13, and piezoelectric ceramic 14 together constitute a three-mirror mode cleaner. After passing through the three-mirror mode cleaner, the laser is split into two beams. The first beam reflected by the input mirror 7 is used as the inner beam for power feedback, and the second beam transmitted from the output mirror 12 is used for subsequent laser applications. The photodetector 8 detects the reflected beam and converts the optical power into an electrical signal. The reference voltage generation circuit 10 uses an SMT32 as the main control unit to control a high-precision digital-to-analog converter circuit to generate a reference voltage. The analog control circuit 9 includes a differential amplifier circuit, an analog PID circuit, a post-amplifier and filter circuit, which differentially amplifies the voltage signal of the photodetector 8 and the reference voltage. The analog PID circuit adopts a parallel PID structure, which can achieve decoupling adjustment of P / I / D parameters. After post-amplifier filtering, a feedback voltage signal is generated to the RF driver 11, which in turn controls the acousto-optic driver to control the diffraction efficiency, thereby changing the power of the 0th order diffracted light and achieving stable power control.

[0032] This invention stabilizes laser power using an acousto-optic modulator 5. The acousto-optic modulator 5 mainly consists of a piezoelectric transducer and an acousto-optic medium. When the transducer is driven by an externally generated electrical signal of a specific frequency, it generates an ultrasonic signal of the same frequency, which is transmitted to the acousto-optic medium (transparent crystal). This causes a change in refractive index within the medium. When the laser beam passes through the acousto-optic medium (transparent crystal), it interacts with the medium, changing the direction of light propagation, i.e., producing diffraction. Changing the electrical signal adjusts the diffraction efficiency, thereby changing the laser power.

[0033] like Figure 2The diagram shows the structure of a three-mirror cleaner. Within the laser wavelength range of 770-800nm, the input mirror 7 is a fused silica lens with a 99.6% laser reflectivity at an incident angle of 45°, coated with a high-reflectivity film on the left and an anti-reflection film on the right. The output mirror 12 is also a fused silica lens with a 99.6% laser reflectivity at an incident angle of 45°, coated with a high-reflectivity film on the left and an anti-reflection film on the right. The reflecting mirror 13 is a fused silica lens with a radius of curvature of 1m and a 99.99% laser reflectivity at an incident angle of 45°, with a frosted back and a high-reflectivity film. The cavity length of the three-mirror cleaner is approximately 1m, the distance between the plane mirrors is 20cm, the distance between the plane mirrors and the concave mirror is 40cm, the precision is 1000, the laser transmittance is 66%, and the linewidth is 308kHz.

[0034] like Figure 3 The diagram illustrates the principle behind mode cleaners for reducing power noise. Mode cleaners can be combined with conventional photoelectric feedback to further reduce power noise; this method is known as optical AC coupling (OAC). In the diagram, the OAC cavity represents the three-mirror mode cleaner used, and the PD (photoelectric detector) is the photodetector. The principle behind mode cleaners reducing power noise is that they can reduce the photocurrent of the inner-loop detector without reducing sensitivity to power fluctuations. Specifically, this manifests as a low-pass filter for transmitted light and a high-pass filter for reflected light. The changes in laser light after passing through the mode cleaner can be studied using the transfer function.

[0035] The input laser consists of a carrier laser and power fluctuations, which can be approximated as white noise, forming a noise sideband. Within the resonant cavity linewidth, the carrier and noise sidebands propagate. A portion of the cavity field leaks into the transmission field, while another portion enters the reflection field. The reflection field then consists of two laser beams: light directly reflected from the input mirror and light leaking from the cavity into the reflection field. The combination of these two laser beams attenuates the current-carrying laser within the resonant cavity linewidth, while the noise sideband outside the linewidth maintains its original height. Therefore, the DC power detected at the detector at the reflection end is reduced, achieving what is equivalent to detecting the total optical power incident on the resonator, while significantly reducing the actual optical power on the detector. This reduces the average power of the photodetector while maintaining the power noise level. However, if the same average power is maintained at the photodetector, the noise sensitivity both within and outside the resonant cavity linewidth increases by approximately an order of magnitude, with the increase being particularly pronounced outside the linewidth.

[0036] Preferably, the reference voltage generation circuit 10 includes a main control STM32 and a digital-to-analog converter circuit. The STM32 controls the digital-to-analog converter circuit to generate a variable reference voltage with a voltage range of 0-5V.

[0037] An important factor affecting the intensity of the reflected light leakage field is called the impedance factor. The magnitude of the impedance factor is called impedance matching. Impedance matching can be used to represent the degree of reduction of the incident optical carrier in the reflection field and is an important parameter of the mode cleaner. By calculating the impedance matching factor a at the resonance frequency:

[0038] ;

[0039] where, represents the voltage value of the reflected laser at the input mirror, represents the voltage value of the incident laser at the input mirror, and R1 and R2 represent the reflectivities of the input mirror and the output mirror, and R L represents the internal cavity loss affected by the three cavity mirrors.

[0040] The effects of different impedance matching factors on the mode cleaner are different. According to the positive and negative of the impedance matching, the mode cleaner can be divided into three states: over-coupling, under-coupling, and impedance matching.

[0041] In the case of over-coupling, that is, -1 < a < 0, the carriers leaked by the mode cleaner are less than the directly reflected carriers. In the case of under-coupling, 0 < a < 1, the carriers leaked by the mode cleaner are greater than the directly reflected carriers. When the impedance is matched, a = 0.

[0042] To construct a high-finesse mode cleaner, it is required that the cavity mirrors have low loss. Since the impedance matching factor a has a strong correlation with the cavity mirror loss, it is necessary to finely control the cavity mirror parameters. The impedance matching factor should be kept close to 0 to ensure that the carriers in the reflection field are greatly attenuated.

[0043] The mode cleaner needs to use the PDH cavity locking method to precisely match with the laser. The working principle of PDH cavity locking can be divided into the following steps: First, determine the mode cleaner as the reference cavity. When the laser frequency exactly matches the resonance frequency of the cavity, a resonance-enhanced signal will be generated in the cavity; then, apply a phase modulation signal to the laser. This modulation is usually performed with a triangular wave or other waveforms with a frequency of dozens of kilohertz; place a photodetector at the reflection end of the resonant cavity. The detected reflected light and the phase modulation frequency of the laser are phase-demodulated through a mixer. The role of the mixer is to multiply the two input signals on both sides. The purpose is to select and eliminate the redundant cosine or sine terms in the frequency domain according to specific applications, analyze the phase change of the reflected light, combine the modulation signal, and then filter out all high frequencies and direct currents through a low-pass filter. The specific phase difference information can be extracted. This phase difference is proportional to the frequency offset of the cavity; electro-optic modulator 2 performs modulation, and finally, a feedback system is constructed using the phase difference information to transmit the feedback voltage to the piezoelectric ceramic 14 located on the resonant cavity, forming a closed loop. The cavity length control element adjusts based on this signal until the error approaches zero to maintain the resonance of the resonant cavity.

[0044] A mode cleaner is essentially an optical resonant cavity with specific impedance matching. The relationship between impedance matching and the transfer function of the mode cleaner can be studied through the transfer function.

[0045] The transfer function of an optical resonant cavity can be expressed as:

[0046] ;

[0047] in, The transfer function represents the resonant cavity, f represents the frequency, and i is the imaginary unit. The bandwidth, referred to as the mode cleaner, is the frequency value at which the amplitude attenuates to 3dB.

[0048] The transfer function of the mode cleaner from the incident field to the reflected field. It can be represented as follows:

[0049] ;

[0050] ;

[0051] Here, g is called the optical AC coupling gain factor, which, without considering mode matching, is inversely proportional to the impedance matching factor a. At low frequencies, the transfer function gain is 1. Starting at |g|, the transfer function gain increases, indicating that the detection sensitivity begins to increase. At high frequencies, the gain approaches |g|, while the phase depends on the sign of g. The power-to-noise ratio limit after passing through the resonant cavity can be expressed as:

[0052] ;

[0053] Where e represents the electron charge. Represents photocurrent, Power noise representing the spectrum.

[0054] like Figure 4 The diagram shows the analog control and adjustment process. The AIN signal is the voltage signal detected by the laser. DEMP_V is the reference voltage generated by the reference voltage circuit 10. After being isolated by the voltage follower, it is connected to the input of the differential amplifier circuit. The output is the error signal ERR. The parallel PID includes proportional, integral, and derivative circuits from top to bottom. The derivative circuit uses RC differentiation, and the gain can be adjusted. After passing through a subsequent amplification and filtering circuit, the PID_OUT signal is generated and output to the RF driver to modulate the acousto-optic modulator.

[0055] The adjustment process of the present invention includes the following steps:

[0056] Step 1: Adjust the output laser of the continuous wave Ti:sapphire laser 1 to normal operating state. As the input laser, it first passes through the half-wave plate 3 and the Glan-Taylor prism 4 to adjust the polarization state to the vertical direction and further purify it. Then, it is input into the acousto-optic modulator 5. Without applying a driving voltage, the laser is allowed to pass accurately through the aperture stop 6 to ensure that the laser is in a collimated state.

[0057] Step 2: Construct a three-mirror cleaner. Input mirror 7 and output mirror 12 are both placed at 45°. The laser passes through the center of input mirror 7 and output mirror 12, which are 20cm apart. Adjust the position and angle of reflector 13 so that the reflected light from output mirror 12 and the transmitted light from input mirror 7 resonate within the cavity. The distance between reflector 13 and the centers of input mirror 7 and output mirror 12 is 40cm. Attach piezoelectric ceramic 14 to the back of reflector 13 and connect it to electro-optic modulator 2 via a PDH cavity-locking system.

[0058] Step 3: Connect the photodetector 8 to the subsequent analog control circuit 9, reference voltage generation circuit 10, and RF driver 11. By adjusting the variable resistor, obtain the PID parameters to stabilize the detection voltage at the reference voltage, generate the driving voltage to the RF driver to control the acousto-optic modulator for diffraction efficiency control, and stabilize the laser power.

[0059] The above three steps achieve automatic stabilization of laser power.

[0060] The contents not described in detail in this specification are prior art known to those skilled in the art. Those skilled in the art will readily understand that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A power stabilization optimization system for a continuous-wave Ti:sapphire laser based on a three-mirror mode cleaner, characterized in that, Includes electro-optic modulators, half-wave plates, Glan-Taylor prisms, acousto-optic modulators, aperture diaphragms, three-mirror mode cleaners, photodetectors, analog adjustment circuits, reference voltage generation circuits, and radio frequency drivers. The electro-optic modulator is used for adjusting the cavity length of the three-mirror cleaner; The half-wave plate is used to adjust the polarization state of the incident laser. The Glan-Taylor prism is used to further purify the polarization state of the incident laser. The acousto-optic modulator is used to diffract the incident laser to generate 0th-order diffracted light and 1st-order diffracted light; The aperture stop is used to intercept first-order diffracted light and allow 0th-order diffracted light to pass through. The mold cleaner is used to feed back a portion of the laser power, further reducing the power noise of the laser. The electro-optic modulator, half-wave plate, Glan Taylor prism, acousto-optic modulator, aperture stop, and three-mirror mode cleaner are sequentially passed through the incident laser. The photodetector, analog adjustment circuit, reference voltage generation circuit, and radio frequency driver together constitute a power feedback system, which generates a feedback voltage for laser power feedback. The three-mirror mold cleaner is an optical cavity composed of three optical lenses: two plane mirrors for input and output, and one concave mirror for laser reflection. The concave mirror is fitted with piezoelectric ceramic for cavity length locking. Within the laser wavelength range of 770-800nm, the input mirror is a fused silica lens with a laser reflectivity of 99.6% at an incident angle of 45°, the output mirror is a fused silica lens with a laser reflectivity of 99.6% at an incident angle of 45°, and the reflector is a fused silica lens with a radius of curvature of 1m and a laser reflectivity of 99.99% at an incident angle of 45°. The cavity length of the mold cleaner is approximately 1m, the distance between the plane mirrors is 20cm, the distance between the plane mirrors and the concave mirror is 40cm, the precision is 1000, the laser transmittance is 66%, and the linewidth is 308kHz.

2. The power stabilization optimization system for a continuous-wave Ti:sapphire laser based on a three-mirror mode cleaner according to claim 1, characterized in that, The electro-optic modulator controls the piezoelectric ceramic voltage of the mold cleaner via PDH cavity locking to adjust the cavity length of the three-mirror mold cleaner.

3. The power stabilization optimization system for a continuous-wave Ti:sapphire laser based on a three-mirror mode cleaner according to claim 1, characterized in that, The half-wave plate adjusts the polarization direction of the incident laser to the vertical direction.

4. The power stabilization optimization system for a continuous-wave Ti:sapphire laser based on a three-mirror mode cleaner according to claim 1, characterized in that, The acousto-optic modulator is connected to the radio frequency driver, and modulates and controls the relative power of the 0th-order diffracted light and the 1st-order diffracted light according to the driving voltage of the radio frequency driver.

5. The power stabilization optimization system for a continuous-wave Ti:sapphire laser based on a three-mirror mode cleaner according to claim 1, characterized in that, The analog adjustment circuit includes a differential amplifier circuit, an analog PID adjustment circuit, and a post-amplifier circuit connected in sequence. The differential amplifier circuit is connected to the photodetector and the reference voltage generation circuit. The analog PID adjustment circuit adopts analog parallel PID adjustment. After being amplified and filtered by the post-amplifier, the output is sent to the radio frequency driver. The radio frequency driver is connected to the acousto-optic modulator.

6. The power stabilization optimization system for a continuous-wave Ti:sapphire laser based on a three-mirror mode cleaner according to claim 1, characterized in that, The reference voltage generation circuit includes a main control STM32 and a digital-to-analog converter circuit. The STM32 controls the digital-to-analog converter circuit to generate a variable reference voltage with a voltage range of 0-5V.

7. The method for optimizing the power stability of a continuous-wave Ti:sapphire laser based on a three-mirror mode cleaner, according to any one of claims 1-6, is characterized in that... Includes the following steps: Step 1: Adjust the output laser of the continuous wave Ti:sapphire laser to normal operating state. As input, it first passes through a half-wave plate and a Glan-Taylor prism to adjust the polarization state to the vertical direction and further purify it before being input into the acousto-optic modulator. Without applying a driving voltage, allow the laser to pass accurately through the aperture stop to ensure that the laser is collimated. Step 2: Construct a three-mirror cleaner. The input and output mirrors are both placed at 45°. The laser passes through the center of the input and output mirrors, which are 20cm apart. Adjust the position and angle of the reflector so that the reflected light from the output mirror and the transmitted light from the input mirror coincide in the cavity to form resonance. The distance between the reflector and the center of the input and output mirrors is 40cm. Attach piezoelectric ceramic to the back of the reflector and connect it to the electro-optic modulator through a PDH cavity-locking system. Step 3: Connect the photodetector to the subsequent analog control circuit, reference voltage generation circuit, and RF driver. By adjusting the variable resistor, obtain the PID parameters to stabilize the detection voltage at the reference voltage. Generate the driving voltage to the RF driver to control the acousto-optic modulator for diffraction efficiency control and stabilize the laser power.

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