Dual-frequency laser generation method and device with dual-stable frequency and power and high-power output

Abstract

The present application belongs to the field of dual-frequency laser technology and precise measurement technology, and particularly relates to a dual-frequency laser generation method and device with frequency and power stability and high power output. In order to solve the problems of low output power and frequency stability of dual-frequency laser and small output power, the present application selects a high-power laser and an optoelectronic device with a high power threshold (rather than an atomic cell which cannot withstand high power) to obtain stronger output power. An acousto-optic modulator is selected as an actuator, and high-precision power modulation technology is used for active feedback to obtain higher power stability. High-stability atomic frequency generation technology, same-attribute transmission line standardization technology, low-noise shielding and optimization technology, and equal-arm optical design technology are combined to ensure that the dual-frequency laser output has higher frequency stability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of dual-frequency laser technology and precise measurement technology, and particularly relates to a dual-frequency laser generation method and device with frequency and power stability and high power output, which is mainly used for pointing measurement and ultra-precise measurement. BACKGROUND

[0002] Remote sensing mapping networks, satellite positioning and navigation systems, and space target monitoring systems have been established in countries all over the world. In these systems, dual-frequency laser interferometric measurement technology is widely used in high-precision mapping, positioning, ultra-precision measurement, and directional measurement fields due to its excellent measurement accuracy and resolution. The power stability and frequency stability of dual-frequency laser directly affect the accuracy and reliability of the measurement results. At present, the generation of dual-frequency laser mainly relies on the following technologies: Zeeman energy level splitting, acousto-optic modulation frequency shifting, birefringence-Zeeman method, and dual-longitudinal-mode frequency locking. In these methods, a helium-neon laser is usually selected as the light source.

[0003] From the aspect of power stability of the dual-frequency laser source, the output light of the helium-neon laser is usually used as the base frequency light, but its spectral line width is about 1.5 GHz, which makes it difficult to operate at a single frequency. Moreover, the helium-neon laser belongs to a gas laser, and its gas characteristics are relatively unstable and are easily affected by environmental temperature and air pressure, which may cause fluctuations in the output power of the laser. In addition, the helium-neon laser has a complex resonant cavity structure, which is more susceptible to external factors, thereby affecting the output stability of the laser. Considering the energy level transition characteristics of helium-neon gas, its output wavelength and power are very sensitive to environmental factors such as temperature changes, which is also a reason for power fluctuations.

[0004] The Zeeman energy level splitting method is the most commonly used method for generating dual-frequency laser in the current market mature commercial products, but whether the longitudinal magnetic field or the transverse magnetic field is applied, it will be affected by the environment and the helium-neon laser itself, resulting in problems such as low output power stability and frequency stability of the dual-frequency laser, and the output power will decrease with the increase of the frequency difference due to the influence of frequency difference locking. The industry generally believes that there is no potential for further development. The birefringence-Zeeman effect dual-frequency laser generation scheme is proposed by a research group of Tsinghua University. This method solves the problem of frequency difference locking, and the optical power is only about 1 mW in the range of 0-40 MHz. Although this method avoids the problem of not being able to achieve large frequency difference output by using only the Zeeman effect to generate dual-frequency laser, it still faces problems such as low optical power, poor frequency stability and power stability. In addition, the laser produced by this method can only output dual-frequency laser with a specific frequency difference, which needs to be customized. The dual-longitudinal-mode frequency locking method produces dual-frequency laser with a frequency difference of 600-1000 MHz. The too high frequency cannot be directly applied to the fields of pointing measurement and ultra-precision measurement, which will lead to large measurement errors.

[0005] No matter which way the dual-frequency laser is generated by the above-mentioned, it is faced with the limitation of helium-neon laser itself, and cannot realize frequency and power double-stable high-power output. The dual-frequency laser interference measurement technology relies on high-stable frequency and power output to ensure the accuracy and reliability of the measurement, because the frequency fluctuation will directly affect the interference signal generated by the beat frequency, and then affect the accurate detection of the micro displacement. In addition, the power stability of the laser is crucial to the measurement range, and the power fluctuation may cause the detection accuracy to decrease. At the same time, the stability of the frequency and power also helps to control the phase and intensity noise, thereby reducing the interference and improving the overall response speed and resolution of the system, which is one of the key factors to realize high-precision interference measurement.

[0006] In summary, there is an urgent need in the art for a dual-frequency laser generating device and method with high frequency stability and high power stability and high power output. SUMMARY

[0007] In view of the deficiencies of the prior art, the present application provides a dual-frequency laser generating method and device with frequency and power double-stable high-power output. The method and device use the same set of acousto-optic modulators as actuators, and adopt the active feedback type "high-precision power modulation and frequency modulation" technology, so as to realize a high-power dual-frequency laser source with tunable frequency difference and high power stability and high frequency stability. This light source has wide application prospects in the fields of pointing measurement such as surveying, satellite attitude measurement, interstellar exploration, space communication pointing calibration, and ultra-high precision interference displacement (or angle) measurement such as optical lithography positioning, machine tool calibration, micro-electro-mechanical system high-precision measurement, and optical element detection, and has significant advantages compared with the previous dual-frequency laser source generation scheme.

[0008] To achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0009] The present application provides a dual-frequency laser generating device with frequency and power double-stable high-power output, comprising a laser, a high-precision power modulation and frequency modulation system;

[0010] The laser generates laser light, which successively passes through a quarter-wave plate, a half-wave plate and a first polarization beam splitter to form P-polarized light and S-polarized light. The P-polarized light and the S-polarized light pass through the high-precision power modulation and frequency modulation system to form two frequency-shifted light beams. The two frequency-shifted light beams pass through a second polarization beam splitter to form a dual-frequency laser beam with power and frequency double-stable high-power output.

[0011] The high-precision power modulation and frequency modulation system comprises a high-precision power modulation system and a high-precision frequency modulation system.

[0012] The high-precision frequency modulation system comprises a first acousto-optic modulator, a second acousto-optic modulator, a first power amplifier, a second power amplifier and a timing device, a first output end of the timing device is connected with the first acousto-optic modulator through the first power amplifier, and a second output end of the timing device is connected with the second acousto-optic modulator through the second power amplifier.

[0013] The high-precision power modulation system comprises a first acousto-optic modulator, a second acousto-optic modulator, a servo system, a first low-noise photodetector, a second low-noise photodetector, a first power amplifier, a second power amplifier, a first beam splitter and a second beam splitter, an output end of the first low-noise photodetector is connected with the first power amplifier through a first input end and a first output end of the servo system in sequence, and the first power amplifier is connected with the first acousto-optic modulator.

[0014] The two parts in the high-precision power modulation and frequency modulation system jointly control the same set of acousto-optic modulators, and control the power and frequency output of the frequency-shifted light beams.

[0015] Further, the timing device is a high-stability timing device for providing a clock signal, including but not limited to atomic clocks of hydrogen, rubidium and cesium, nuclear clocks.

[0016] Further, the device further comprises a plurality of high-reflection mirrors for reflecting the P-polarized light and the S-polarized light to the first acousto-optic modulator and the second acousto-optic modulator respectively, and reflecting the two frequency-shifted light beams to the second polarization beam splitter.

[0017] The application also provides a frequency and power double-stable high-power output dual-frequency laser generation method, comprising the following steps:

[0018] Step 1, the base frequency light generated by the laser passes through a quarter-wave plate and a half-wave plate, and the polarization state of the laser is adjusted by rotating the half-wave plate, so that the linear polarization direction forms an angle of 45° with the horizontal direction;

[0019] Step 2, the laser beam after polarization adjustment passes through a first polarization beam splitter to form P-polarized light and S-polarized light;

[0020] Step 3: Pass the P-polarized light and the S-polarized light through a high-precision power modulation and frequency modulation system to form two frequency-shifted light beams. The high-precision power modulation and frequency modulation system includes a first acousto-optic modulator, a second acousto-optic modulator, a servo system, a timing device, a first low-noise photodetector, a second low-noise photodetector, a first power amplifier, a second power amplifier, a first beam splitter, and a second beam splitter. The first output end of the timing device is connected to the first acousto-optic modulator via the first power amplifier, and the second output end of the timing device is connected to the second acousto-optic modulator via the second power amplifier; the output end of the first low-noise photodetector is connected to the first power amplifier via the first input end and the first output end of the servo system in sequence, and the first power amplifier is connected to the first acousto-optic modulator. The output end of the second low-noise photodetector is connected to the second power amplifier via the second input end and the second output end of the servo system in sequence, and the second power amplifier is connected to the second acousto-optic modulator.

[0021] Step 4: Pass the two frequency-shifted light beams through a second polarization beam splitter to form a dual-frequency laser beam with high-power output that is both power- and frequency-stable.

[0022] The high-precision power and frequency modulation system consists of two parts. The high-precision frequency modulation component, which uses a high-precision timing device to provide a clock signal, drives a piezoelectric transducer through a power amplifier to generate acoustic waves, which drive the acousto-optic medium to form a movable grating that is stationary relative to the speed of light, thereby diffracting light of different frequencies. The dielectric grating formed by the acoustic waves is more uniform and stable, ensuring the frequency stability of the generated dual-frequency laser light source, reaching internationally leading standards. The high-precision power modulation component, on the other hand, converts the optical signal into an electrical signal via a low-noise photodetector, which is then fed into a servo system for feedback control of the laser output power, ensuring the power stability of the dual-frequency laser light source.

[0023] Furthermore, the high-precision power modulation in step 3 is achieved by the direct relationship between the diffraction efficiency of the first-order diffracted light of the AOM and the radio frequency power. The diffraction efficiency of the first-order diffracted light is linearly related to the radio frequency power, and the relationship is: η = fP1. Where f represents the slope in the linear region, P1 represents the magnitude of the radio frequency power; when the incident laser power before the AOM is X in When , the first-order diffraction light power is: X out =ηX in ±X fluctuation Among them, X fluctuation is the fluctuation size of the light field; the voltage signal received by the detector is: V PD =GRX out , G is the photoelectric conversion efficiency of the photodetector, and R is the percentage of feedback sampling. The collected voltage signal is compared with a preset high-precision voltage Vset By comparison, the signal difference is ΔV = V PD -V set After the servo system control circuit, the error signal generated is:

[0024]

[0025] Among them, P (proportional), I (integral), and D (differential) are the parameters of feedback control, x offset The initial voltage feedback parameter is set; the error signal is fed back to the optical modulator in real time, and by controlling the RF power applied to the AOM driver (power amplifier, piezoelectric transducer), a stable laser power output is achieved. This process constitutes the function of a complete feedback control system.

[0026] Furthermore, the high-precision frequency modulation method in step 3 specifically provides a stable clock reference through an atomic frequency generator to ensure that stray light is minimized during the acousto-optic frequency shifting process. The physical relationship can be expressed as follows:

[0027] Assume that the light field expression of the incident light is:

[0028]

[0029] The dual-frequency laser is generated by the dual-acousto-optic modulation method, and its noise mainly considers the noise introduced by the signal source. Delay noise introduced during signal transmission Noise introduced by the power amplifier during signal amplification The piezoelectric transducer of the acousto-optic modulator converts the electrical signal into sound waves, and the noise introduced by the diffraction process of light through the acoustic medium wait;

[0030] The ultrasonic field propagates in the direction perpendicular to the acousto-optic crystal, and noise in amplitude, frequency, phase, etc. is superimposed, and its expression is:

[0031]

[0032] The light field is modulated using the ultrasonic field, which is expressed as:

[0033]

[0034] In the high-precision frequency modulation system, only the frequency ω0+ω1+ω2+ω3+ω3+ω4 and phase

[0035] Regarding the phase part: the present invention ensures that the optical paths of the two orthogonal polarized lasers in the dual-frequency laser are the same by using an '8'-shaped equal-arm design to ensure that the optical paths of the two orthogonal polarized lasers are as similar as possible, and uses radio frequency devices with the same electrical characteristics to ensure that the phase delays of the two orthogonal polarized lasers during frequency shifting are as consistent as possible, thereby reducing the phase difference between the two polarized light beams.

[0036] For the frequency part: an atomic frequency generator is used to provide a highly stable clock reference, making the center frequency of the output signal more stable and the bandwidth narrower, ensuring that the frequency noise f1 (ω1=2πf1) of the output signals of different frequencies is consistent. Transmission lines of the same material, length, and thickness are used (standardization technology for transmission lines with the same properties) to ensure that the frequency noise f2 (ω2=2πf2) introduced by the transmission delay of the two signals is as similar as possible. Power amplifiers and acousto-optic modulators with similar electrical characteristics are selected (low-noise shielding and optimization technology) to ensure that the noise f3 (ω3=2πf3) introduced during the signal amplification process and the noise f4 (ω4=2πf4) introduced by the conversion of electrical signals into sound waves and the diffraction of light through acoustic media are as similar as possible.

[0037] The frequency of two polarized lights is shifted by acousto-optic modulation, and the frequency components are expressed as:

[0038] f AOM1 =f aom1 +f1+f2+f3+f4+...

[0039] f AOM2 =f aom2 +f1'+f2'+f3'+f4'+...

[0040] where f AOM1 、f AOM2 are the frequencies of the first-order diffracted light output by the two AOMs, f aom1 、f aom2 They represent the frequencies of the fundamental frequency light f0 after frequency shifting by the acousto-optic modulator, f1 and f1' represent the frequency noise introduced by the output signals of signal sources with different frequencies, f2 and f2' represent the frequency noise introduced by the different transmission delays of the two signals, and f3, f3', f4 and f4' represent the noise introduced by the acousto-optic modulator and piezoelectric transducer with different electrical characteristics during the signal amplification process of the two signals, as well as the noise introduced by the conversion of electrical signals into sound waves and the diffraction of light through acoustic media.

[0041] After the two polarized light beams beat each other, they can be expressed as:

[0042] f beat =|(f aom1 -f aom2 )+(f1-f1')+(f2-f2')+(f3-f3')+(f4-f4')...|

[0043] After the two modulated polarized light beams beat, they can partially cancel out the frequency noise sources, namely (f1-f1'), (f2-f2'), (f3-f3'), and (f4-f4'). Because the frequency modulation system designed by the present invention introduces less noise during the frequency shift process, the noise cancellation after the beat frequency subtraction is purer, and the frequency noise of the output dual-frequency laser is lower, thereby ensuring the frequency stability of the dual-frequency laser output.

[0044] The laser uses a high-power laser and optoelectronic devices that can withstand a higher power threshold (rather than an atomic gas chamber that cannot withstand high power), achieving a stronger output power than a helium-neon dual-frequency laser. This type of laser can provide a new option for dual-frequency preparation solutions. Its laser power output is more stable than that of helium-neon gas lasers, and its power can reach hundreds of milliwatts (mW) or even watts (W). This ensures that the generated dual-frequency laser light source has better power stability and higher output power, reaching international leading indicators.

[0045] Compared with the prior art, the present invention has the following advantages:

[0046] (1) High frequency stability: Most existing dual-frequency solutions use helium-neon gas lasers, which have a relatively wide linewidth (about 1.5GHz), affecting the frequency stability of the output laser. The present invention uses the "high-precision power modulation and frequency modulation system" solution and key technologies such as optical path equal arm design to improve the frequency stability of the dual-frequency laser light source. The frequency modulation part of the high-precision power modulation and frequency modulation system uses atomic clocks, atomic nuclear clocks and other atomic frequency generation technologies to provide clock references, ensuring that the frequency stability theory of the dual-frequency laser light source is similar to that of the atomic clock. This is also one of the important factors for the high frequency stability of the developed dual-frequency laser light source. The frequency stability of the dual-frequency laser light source currently achieved is improved by 1 to 2 orders of magnitude compared to the existing technology.

[0047] (2) The laser light source has high power and good power stability: The present invention uses high-power lasers and acousto-optic devices with a high power threshold (rather than atomic gas chambers that cannot withstand high power), and obtains a stronger output power than the helium-neon dual-frequency laser. Its power can reach hundreds of watts and milliwatts or even watts (He-Ne lasers are usually a few milliwatts), and a dual-frequency laser light source can be used to achieve simultaneous measurement of multiple axes and dimensions. When used with high-precision power modulation, another advantage is better power stability, reducing errors introduced by power fluctuations, reducing the difficulty of detector acquisition, and improving measurement accuracy. In terms of economic benefits, multiple devices sharing a set of laser light sources will greatly save costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1Schematic diagram of a dual-frequency laser generating device with dual-stable frequency and power and high-power output according to the present invention;

[0049] Figure 2 This is a flow chart of the dual-frequency laser generation method with dual-stable frequency and power and high-power output according to the present invention;

[0050] Figure 3 This is a graph showing the results of the dual-frequency laser frequency stability evaluation of the present invention;

[0051] Figure 4 This is a graph showing the results of the dual-frequency laser power stability evaluation of the present invention;

[0052] Among them, there are laser-1, quarter-wave plate-2, first half-wave plate-3, first polarization beam splitter-4, high-reflection mirror-5, high-precision power modulation and frequency modulation system-6, first acousto-optic modulator-61, second acousto-optic modulator-62, servo system-63, timing device-64, first low-noise photodetector-65, second low-noise photodetector-66, first power amplifier-67, second power amplifier-68, first beam splitter 69, second beam splitter 610, and second polarization beam splitter-7. DETAILED DESCRIPTION

[0053] In order to further illustrate the technical solution of the present invention, the present invention is further described below through examples.

[0054] like Figure 1 As shown, a dual-frequency laser generating device with dual-stable frequency and power and high-power output in this embodiment includes a laser 1, a high-precision power modulation and frequency modulation system 6;

[0055] The laser 1 generates laser light, which passes through a quarter-wave plate 2, a half-wave plate 3, and a first polarization beam splitter 4 in sequence to form P-polarized light and S-polarized light. The P-polarized light and S-polarized light pass through a high-precision power modulation and frequency modulation system 6 to form two frequency-shifted light beams. The two frequency-shifted light beams pass through a second polarization beam splitter 7 to form a dual-frequency laser beam with dual-stabilization of power and frequency and high-power output.

[0056] The high-precision power modulation and frequency modulation system 6 includes a first acousto-optic modulator 61, a second acousto-optic modulator 62, a servo system 63, a timing device 64, a first low-noise photodetector 65, a second low-noise photodetector 66, a first power amplifier 67, a second power amplifier 68, a first beam splitter 69 and a second beam splitter 610; the first output end of the timing device 64 is connected to the input end of the first power amplifier 67, the output end of the first power amplifier 67 is connected to the input end of the first acousto-optic modulator 61, the P-polarized light passes through the first acousto-optic modulator 61 to the first beam splitter 69, and is divided into two beams of frequency-shifted P-polarized light, one beam of frequency-shifted P-polarized light is detected by the first low-noise photodetector 65, the output end of the first low-noise photodetector 65 is connected to the first input end of the servo system 63 The first output end of the servo system 63 is connected to the input end of the first power amplifier 67, and the other beam of frequency-shifted P polarized light passes through the second polarization beam splitter 7; the second output end of the timing device 64 is connected to the input end of the second power amplifier 67, and the output end of the second power amplifier 68 is connected to the input end of the second acousto-optic modulator 62. The S polarized light passes through the second acousto-optic modulator 62 to the second beam splitter 610 and is divided into two beams of frequency-shifted S polarized light. One beam of frequency-shifted S polarized light is detected by the second low-noise photodetector 66, and the output end of the second low-noise photodetector 66 is connected to the second input end of the servo system 63. The second output end of the servo system 63 is connected to the input end of the second power amplifier 68, and the other beam of frequency-shifted S polarized light passes through the second polarization beam splitter 7.

[0057] As a further improvement of this embodiment, the device further includes a plurality of highly reflective mirrors 5 for reflecting the P-polarized light and the S-polarized light to the first acousto-optic modulator 61 and the second acousto-optic modulator 62, respectively, and reflecting the two frequency-shifted light beams to the second polarization beam splitter 7.

[0058] The laser 1 of this embodiment is a non-planar ring cavity laser (NPRO), which is a high-power solid-state laser. The timing device 64 is a highly stable timing device for providing a clock signal, and is a rubidium atomic clock.

[0059] like Figure 2 As shown, a dual-frequency laser generation method with dual-stable frequency and power and high-power output in this embodiment, based on the device, includes the following steps:

[0060] Step 1: After the laser light generated by laser 1 passes through quarter wave plate 2, the polarization state of the laser light is adjusted by rotating half wave plate 3;

[0061] Step 2, passing the polarization-adjusted laser beam through a first polarization beam splitter 4 to form P-polarized light and S-polarized light;

[0062] Step 3: The P-polarized light and the S-polarized light are subjected to high-precision power modulation and high-precision frequency modulation by the first acousto-optic modulator 61 and the second acousto-optic modulator 62 in the high-precision power modulation and frequency modulation system 6 to form two frequency-shifted light beams.

[0063] Step 4: The two frequency-shifted light beams are passed through a second polarization beam splitter 7 to form a dual-frequency laser beam with dual-stabilization of power and frequency and high-power output.

[0064] The high-precision power modulation of this embodiment is achieved through the direct relationship between the diffraction efficiency of the first-order diffracted light of the first AOM 61 and the second AOM 62 and the RF power, specifically:

[0065] The diffraction efficiency of the first-order diffraction light is linearly related to the RF power, and the relationship is:

[0066] η=fP1

[0067] Where f represents the slope in the linear region, and P1 represents the magnitude of the RF power;

[0068] When the incident laser power before the first AOM 61 and the second AOM 62 is X in When , the first-order diffraction light power is:

[0069] X out =ηX in ±X fluctuation

[0070] Among them, X fluctuation is the fluctuation size of the light field;

[0071] The voltage signals collected by the first low-noise photodetector 65 and the second low-noise photodetector 66 are:

[0072] V PD =GRX out

[0073] Wherein, G is the photoelectric conversion efficiency of the first low-noise photodetector 65 and the second low-noise photodetector 66, and R is the percentage of feedback sampling;

[0074] The collected voltage signal is compared with a preset high precision voltage V set By comparison, the signal difference is:

[0075] ΔV=V PD -V set ;

[0076] After the servo system 63 controls the circuit, the error signal generated is:

[0077]

[0078] Among them, P, I, and D are the parameters of feedback control, x offset is the initial voltage feedback parameter to be set;

[0079] The respective error signals are fed back to the first AOM 61 and the second AOM 62 in real time, thereby achieving stable output of laser power.

[0080] The specific process of high-precision frequency modulation in this embodiment is as follows:

[0081] Assume that the light field expression of the incident light is:

[0082] The noise introduced by the signal source is:

[0083] The delay noise introduced during signal transmission is:

[0084] The noise introduced by the first power amplifier 67 and the second power amplifier 68 during the signal amplification process is:

[0085] The electrical signal is converted into sound waves, and the noise introduced by the diffraction process of light through the acoustic medium is:

[0086] The noise superposition of the ultrasonic field is:

[0087] The light field is modulated using the ultrasonic field, which is expressed as:

[0088]

[0089] Consider only the frequencies ω0+ω1+ω2+ω3+ω3+ω4 and the phases

[0090] For the frequency part: the two polarized lights are shifted in frequency by acousto-optic modulation, and the frequency component is expressed as:

[0091] f AOM1 =f aom1 +f1+f2+f3+f4+...

[0092] f AOM2 =f aom2 +f1'+f2'+f3'+f4'+...

[0093] Among them, f AOM1 、f AOM2 f represents the frequency of the first-order diffracted light output by the first low-noise photodetector 65 and the second low-noise photodetector 66, respectively.aom1 、f aom2 represents the frequency of the fundamental frequency light f0 after frequency shift, f1 and f1' represent the frequency noise introduced by the output signals of signal sources with different frequencies, f2 and f2' represent the frequency noise introduced by the different transmission delays of the two signals, f3 and f3' represent the noise introduced by the two electrical signals during the signal amplification process through the first power amplifier 67 and the second power amplifier 68 with different electrical characteristics, respectively, and f4 and f4' represent the noise introduced by the light diffraction process through the acoustic medium after the two electrical signals are converted into acoustic waves through the piezoelectric transducers in the first acousto-optic modulator 61 and the second acousto-optic modulator 62 with different electrical characteristics, respectively.

[0094] Regarding the phase part: the present invention ensures that the optical paths of the two orthogonally polarized lasers in the dual-frequency laser are the same by using an '8'-shaped equal-arm design to ensure that the optical paths of the two orthogonally polarized lasers are as similar as possible, and uses radio frequency devices with the same electrical characteristics to ensure that the phase delays of the two orthogonally polarized lasers during frequency shifting are as consistent as possible, thereby reducing the phase difference between the two polarized light beams.

[0095] After the two polarized beams beat each other, the dual-frequency laser beam is expressed as:

[0096] f beat =|(f aom1 -f aom2 )+(f1-f1')+(f2-f2')+(f3-f3')+(f4-f4')...|.

[0097] Based on the above technical solution, the frequency results of the dual-frequency laser of the present invention are as follows Figure 3 .from Figure 3 It can be clearly observed that the frequency stability of the dual-frequency laser of the present invention is measured by a frequency meter, and the measurement results are analyzed by Allan variance. After calculation, the theoretical Allan variance is: σ y (τ)≈2.75×10 -11 .

[0098] The results of the power stability evaluation of the dual-frequency laser of the present invention are as follows Figure 4 . Figure 4 The middle left figure shows the output power of the He-Ne dual-frequency laser, and the right figure shows the output power of the dual-frequency laser of the present invention. It can be clearly observed from the figures that the power stability of the dual-frequency laser of the present invention is one order of magnitude higher than the output power stability of the existing He-Ne dual-frequency laser on the market, and the output power is higher.

[0099] The foregoing shows and describes the principal features and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the present invention is defined by the appended claims, not the foregoing description, and all variations that come within the meaning and range of equivalents of the claims are intended to be embraced therein.

[0100] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A dual-frequency laser generating device with dual-stable frequency and power and high-power output, characterized in that: It includes a laser (1), a high-precision power modulation and frequency modulation system (6); The laser (1) generates laser light, which passes through a quarter-wave plate (2), a half-wave plate (3), and a first polarization beam splitter (4) in sequence to form P-polarized light and S-polarized light. The P-polarized light and the S-polarized light pass through a high-precision power modulation and frequency modulation system (6) to form two frequency-shifted light beams. The two frequency-shifted light beams pass through a second polarization beam splitter (7) to form a dual-frequency laser beam with dual-stabilization of power and frequency and high-power output. The high-precision power modulation and frequency modulation system (6) comprises a first acousto-optic modulator (61), a second acousto-optic modulator (62), a servo system (63), a timing device (64), a first low-noise photodetector (65), a second low-noise photodetector (66), a first power amplifier (67), a second power amplifier (68), a first beam splitter (69) and a second beam splitter (610); a first output end of the timing device (64) is connected to an input end of the first power amplifier (67), an output end of the first power amplifier (67) is connected to an input end of the first acousto-optic modulator (61), the P-polarized light passes through the first acousto-optic modulator (61) to the first beam splitter (69), and is divided into two frequency-shifted P-polarized lights, one of which is detected by the first low-noise photodetector (65), and the output end of the first low-noise photodetector (65) is connected to the output end of the servo system (63). The first input end is connected, the first output end of the servo system (63) is connected to the input end of the first power amplifier (67), and the other frequency-shifted P-polarized light passes through the second polarization beam splitter (7); the second output end of the timing device (64) is connected to the input end of the second power amplifier (67), the output end of the second power amplifier (68) is connected to the input end of the second acousto-optic modulator (62), the S-polarized light passes through the second acousto-optic modulator (62) to the second beam splitter (610), and is divided into two frequency-shifted S-polarized light beams, one frequency-shifted S-polarized light beam is detected by the second low-noise photodetector (66), the output end of the second low-noise photodetector (66) is connected to the second input end of the servo system (63), the second output end of the servo system (63) is connected to the input end of the second power amplifier (68), and the other frequency-shifted S-polarized light beam passes through the second polarization beam splitter (7).

2. A dual-frequency laser generating device with dual-stable frequency and power and high-power output according to claim 1, characterized in that: The laser (1) uses a high-power solid laser and two acousto-optic devices that can withstand a high power threshold to form a dual-frequency laser generation structure, rather than an atomic gas chamber that cannot withstand high power.

3. The dual-frequency laser generating device with dual-stable frequency and power and high-power output according to claim 1, characterized in that: The timing device (64) is a highly stable timing device used to provide a clock signal.

4. The dual-frequency laser generating device with dual-stable frequency and power and high-power output according to claim 3, characterized in that: The timing device (64) is a hydrogen, rubidium, cesium atomic clock, or an atomic nuclear clock.

5. The dual-frequency laser generating device with dual-stable frequency and power and high-power output according to claim 1, characterized in that: It also includes a plurality of high-reflection mirrors (5) for reflecting the P-polarized light and the S-polarized light to the first acousto-optic modulator (61) and the second acousto-optic modulator (62), respectively, and reflecting the two frequency-shifted light beams to the second polarization beam splitter (7).

6. A method for generating a dual-frequency laser with dual-stable frequency and power and high-power output, characterized in that: The device according to any one of claims 1 to 5 comprises the following steps: Step 1, after the laser light generated by the laser (1) passes through the quarter wave plate (2), the polarization state of the laser light is adjusted by rotating the half wave plate (3); Step 2, passing the adjusted laser light through a first polarization beam splitter (4) to form P-polarized light and S-polarized light; Step 3, performing high-precision power modulation and high-precision frequency modulation on the P-polarized light and the S-polarized light through a high-precision power modulation and frequency modulation system (6) to form two frequency-shifted light beams; Step 4: passing the two frequency-shifted light beams through a second polarization beam splitter (7) to form a dual-frequency laser beam with high-power output and dual-stabilization of power and frequency.

7. The method for generating a dual-frequency laser with dual-stable frequency and power and high-power output according to claim 6, characterized in that: The high-precision power modulation in step 3 is achieved by the direct relationship between the diffraction efficiency of the first-order diffracted light of the first acousto-optic modulator (61) and the second acousto-optic modulator (62) and the radio frequency power, specifically: The diffraction efficiency of the first-order diffraction light is linearly related to the RF power, and the relationship is: η=fP1 Where f represents the slope in the linear region, and P1 represents the magnitude of the RF power; When the incident laser power before the first acousto-optic modulator (61) and the second acousto-optic modulator (62) is X in When , the first-order diffraction light power is: X out =ηX in ±X fluctuation Among them, X fluctuation is the fluctuation size of the light field; The voltage signals collected by the first low-noise photodetector (65) and the second low-noise photodetector (66) are: 5 PD =GRX out Wherein, G is the photoelectric conversion efficiency of the first low-noise photodetector (65) and the second low-noise photodetector (66), and R is the percentage of feedback sampling; The collected voltage signal is compared with a preset high precision voltage V set By comparison, the signal difference is: ΔV=V PD -V set ; After the servo system (63) controls the circuit, the error signal generated is: Among them, P, I, and D are the parameters of feedback control, x offset is the initial voltage feedback parameter to be set; The respective error signals are fed back to the first acousto-optic modulator (61) and the second acousto-optic modulator (62) in real time, thereby achieving stable output of laser power.

8. The method for generating a dual-frequency laser with dual-stable frequency and power and high-power output according to claim 7, characterized in that: The high-precision frequency modulation in step 3 is specifically as follows: Assume that the light field expression of the incident light is: The noise introduced by the signal source is: The delay noise introduced during signal transmission is: The noise introduced by the first power amplifier (67) and the second power amplifier (68) during the signal amplification process is: The electrical signal is converted into sound waves, and the noise introduced by the diffraction process of light through the acoustic medium is: The noise superposition of the ultrasonic field is: The light field is modulated using the ultrasonic field, which is expressed as: Consider only the frequencies ω0+ω1+ω2+ω3+ω3+ω4 and the phases For the frequency part: the two polarized lights are shifted in frequency by acousto-optic modulation, and the frequency component is expressed as: f AOM1 =f aom1 +f1+f2+f3+f4+... f AOM2 =f aom2 +f1'+f2'+f3'+f4'+... Among them, f AOM1 、f AOM2 represents the frequency of the first order diffracted light outputted by the first low noise photodetector (65) and the second low noise photodetector (66), respectively, and f aom1 、f aom2 represents the frequency of the fundamental frequency light f0 after frequency shift, f1 and f1' represent the frequency noise introduced by the output signals of different frequency signal sources, f2 and f2' represent the frequency noise introduced by the different transmission delays of the two signals, f3 and f3' represent the noise introduced by the two electrical signals during the signal amplification process through the first power amplifier (67) and the second power amplifier (68) with different electrical characteristics, respectively, and f4 and f4' represent the noise introduced by the light diffraction process through the acoustic medium after the two electrical signals are converted into acoustic waves through the piezoelectric transducers in the first acousto-optic modulator (61) and the second acousto-optic modulator (62) with different electrical characteristics. For the phase part: ensure that the optical path of the two orthogonal polarized lasers in the dual-frequency laser is the same, and reduce the phase difference between the two polarized light beams.

9. The method for generating a dual-frequency laser with dual-stable frequency and power and high-power output according to claim 8, characterized in that: The dual-frequency laser beam in step 4 is represented as: f beat =|(f aom1 -f aom2 )+(f1-f1')+(f2-f2')+(f3-f3')+(f4-f4')...|。

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