Laser phase modulation frequency shift device based on multi-harmonic microwave synthesizer and use method thereof

Abstract

A laser phase modulation frequency shift device based on a multi-harmonic microwave synthesizer comprises an upper computer. An upper computer signal is respectively connected with the first microwave generator, the second microwave generator, the third microwave generator, the fourth microwave generator, the first digital phase shifter, the second digital phase shifter, the third digital phase shifter and the fourth digital phase shifter through the microcontroller; the microwave generator generates a microwave signal according to a reference signal source, the microwave signal is subjected to phase shifting through the digital phase shifter and then synthesized into a sawtooth wave signal in the frequency mixer, the sawtooth wave signal is amplified through the power amplifier until the peak value reaches half-wave voltage and then input into the optical fiber electro-optic phase modulator, and frequency shifting is conducted on laser; the spectrum analyzer is connected with the output end of the power amplifier, analyzes the sawtooth wave signals, generates harmonic signals of all orders, and optimizes the frequency shift of the laser; the design has a higher optical signal bandwidth, is more suitable for an optical fiber electro-optic phase modulator, and achieves the maximization of the efficiency of frequency shift laser.

Description

Technical Field

[0001] The invention belongs to the technical field of optical communication, and in particular relates to a laser phase modulation frequency shifting device based on a multi-harmonic microwave synthesizer. Background Art

[0002] Lasers are widely used in material processing, precision manufacturing, medical field, communication field, atomic and molecular physics, quantum physics, spectroscopy and other scientific research due to their high focusing, high brightness, monochromaticity and good coherence.

[0003] Laser frequency shift technology plays an important role in spectroscopy research. By changing the frequency of the laser, the spectral characteristics of different substances can be finely analyzed. In the laser radar system, laser frequency shift technology can improve the measurement accuracy and detection distance of the laser radar by changing the frequency of the laser, making it play a role in the fields of automatic driving, drones, robot control, etc.

[0004] Laser frequency shifting technology is also a core technology in the field of quantum precision measurement. Laser frequency shifting can generate Raman light for manipulating the internal state of atoms. It can also use multiple laser beams of different frequencies to control the initial velocity and direction of atoms after Doppler cooling, so that atoms move in the target direction.

[0005] Traditional laser frequency shifting methods include: emitting a wide-band spectrum from a tunable laser, and then combining it with wavelength selection technology to obtain the required optical frequency; utilizing nonlinear optical effects to perform frequency conversion on a laser of a fixed wavelength to obtain an optical parametric laser with continuously adjustable wavelength; and precisely fine-tuning the laser resonant cavity length through the inverse piezoelectric effect of piezoelectric ceramics to achieve the effect of precisely tuning the frequency.

[0006] Modern laser frequency shifting technology usually uses acousto-optic modulators and electro-optic modulators to achieve laser frequency shifting. The modulation bandwidth of the acousto-optic modulator is generally only a few hundred megahertz, and is often used in conjunction with a frequency-locked laser for low-frequency frequency shifting; the electro-optic modulator can reach a modulation bandwidth of tens of thousands of megahertz, and its application limit is even higher.

[0007] In the field of quantum precision measurement, the frequency shift of lasers usually needs to be in the order of hundreds of megahertz to gigahertz. At the same time, the insertion loss and electro-optical conversion efficiency of the wide-band electro-optical phase modulator are not absolutely flat, and the laser frequency shifter has higher requirements for adjustability. Therefore, a phase modulation frequency shifting method that can perform high-speed, wide-band frequency shifting on lasers and has adjustable harmonic power is needed.

[0008] The invention with the announcement number CN 103227415 B discloses a fast frequency shifting device and frequency shifting method for semiconductor lasers. The invention controls the output frequency of the laser by controlling the laser current temperature, and shifts the laser frequency by twice the frequency of the RF signal through the double-pass AOM optical path. Finally, the saturated absorption spectrum of the atom is used to lock the frequency-shifted laser frequency, and the locked feedback loop uses the RF output source of the acousto-optic modulator. The invention realizes the laser frequency shifting effect through the frequency-shifted diffracted light of the acousto-optic modulator in the free space optical path. The optical path system is unstable, and the frequency shifting range of the acousto-optic modulator can only reach the order of several hundred megahertz due to bandwidth limitations.

[0009] The invention with the announcement number CN 102519445 B discloses a resonant optical gyroscope based on digital phase ramp frequency shifting technology. The invention uses a digital-to-analog converter (DAC) to output a sawtooth signal with a fixed amplitude of 2] of the full-wave voltage of the electro-optical phase modulator, so that each waveform is just shifted by 2π phase. Then, the slope of the sawtooth signal is changed by adjusting the size of each voltage step output by the analog-to-digital converter, and the time to reach the full-wave voltage is increased, thereby controlling the modulation frequency of the electro-optical phase modulation. The method of generating a sawtooth signal in the invention is through an analog-to-digital converter. The frequency of the generated sawtooth signal is limited by the sampling rate of the module digital signal, and the power of each order of harmonics is not easy to optimize. Summary of the invention

[0010] In view of the above problems, the present invention proposes a laser phase modulation and frequency shifting device based on a multi-harmonic microwave synthesizer and a method of using the same. The design concept is to use multi-harmonic microwave synthesis to generate a sawtooth voltage signal with an amplitude equal to the half-wave voltage of the phase modulator, and then use the sawtooth voltage signal in conjunction with an optical fiber electro-optic phase modulator to phase modulate and frequency shift the laser to achieve higher frequency accuracy and stability.

[0011] A laser phase modulation frequency shifting device based on a multi-harmonic microwave synthesizer comprises a host computer 1, the host computer 1 is signal-connected to a microcontroller 2 and transmits digital commands to the microcontroller 2;

[0012] The microcontroller 2 is respectively connected to the first microwave generator 3, the second microwave generator 4, the third microwave generator 5, the fourth microwave generator 6, the first digital phase shifter 8, the second digital phase shifter 9, the third digital phase shifter 10 and the fourth digital phase shifter 11;

[0013] The first microwave generator 3, the second microwave generator 4, the third microwave generator 5 and the fourth microwave generator 6 respectively perform serial digital communication with a reference signal source 7 and generate microwave signals; wherein the first microwave signal generated by the first microwave generator 3 is input into the mixer 12 after passing through the first digital phase shifter 8; the second microwave signal generated by the second microwave generator 4 is input into the mixer 12 after passing through the second digital phase shifter 9, and the frequency of the second microwave signal is twice that of the first microwave signal; the third microwave signal generated by the third microwave generator 5 is input into the mixer after passing through the third digital phase shifter 10, and the frequency of the third microwave signal is The fourth microwave signal generated by the fourth microwave generator 6 is input into the mixer 12 after passing through the fourth digital phase shifter 11, and the frequency of the fourth microwave signal is four times that of the first microwave signal; the mixer 12 synthesizes the first microwave signal, the second microwave signal, the third microwave signal and the fourth microwave signal into a sawtooth wave signal, and the sawtooth wave signal is amplified by the power amplifier 13 until the peak value reaches the half-wave voltage and then input into the optical fiber electro-optic phase modulator 15; a spectrum analyzer 16 is connected to the output end of the power amplifier 13, analyzes the sawtooth wave signal and generates harmonic signals of various orders; a spectrum analyzer 16 transmits the harmonic signals of various orders to the host computer 1;

[0014] A laser 14 inputs an initial laser of a fixed frequency to a fiber electro-optic phase modulator 15 through an optical fiber. The fiber electro-optic phase modulator 15 performs phase modulation and frequency shifting on the initial laser according to a sawtooth wave signal and then outputs a frequency-shifted laser.

[0015] More specifically, the signal output frequency of the reference signal source 7 is 100 MHz.

[0016] More specifically, the first digital phase shifter 8 , the second digital phase shifter 9 , the third digital phase shifter 10 and the fourth digital phase shifter 11 have an accuracy of eight bits, and can perform a phase shift on the input signal with an accuracy of 1.4°.

[0017] According to Fourier transform theory, it can be calculated that the sawtooth wave signal with a frequency of ω can be expressed as The greater the number n of harmonic signals used for mixing, the higher the waveform restoration of the sawtooth wave signal. The mixed signal can be obtained by inputting four harmonic signals into a four-in-one mixer, and a better sawtooth waveform can be obtained by configuring the frequencies of the four harmonic signals to be the first to fourth order harmonic frequencies of the sawtooth wave frequency through digital control.

[0018] A method for using a laser phase modulation frequency shifting device based on a multi-harmonic microwave synthesizer, the steps comprising:

[0019] 1) The reference signal source 7 sends a reference signal to the first microwave generator 3, the second microwave generator 4, the third microwave generator 5 and the fourth microwave generator 6; the host computer 1 sends an instruction to make the reference signal source 7 perform serial digital communication with the first microwave generator 3, the second microwave generator 4, the third microwave generator 5 and the fourth microwave generator 6 through the microcontroller 2;

[0020] 2) With the frequency of the reference signal source 7 as the reference frequency of the phase-locked loop, the first microwave generator 3 generates a first microwave signal, which is input into the mixer 12 after being phase-shifted by the first digital phase shifter 8; the second microwave generator 4 generates a second microwave signal, which is input into the mixer 12 after being phase-shifted by the second digital phase shifter 9, and the frequency of the second microwave signal is twice that of the first microwave signal; the third microwave generator 5 generates a third microwave signal, which is input into the mixer after being phase-shifted by the third digital phase shifter 10, and the frequency of the third microwave signal is three times that of the first microwave signal; the fourth microwave generator 6 generates a fourth microwave signal, which is input into the mixer 12 after being phase-shifted by the fourth digital phase shifter 11, and the frequency of the fourth microwave signal is four times that of the first microwave signal;

[0021] 3) The mixer 12 synthesizes the first microwave signal, the second microwave signal, the third microwave signal and the fourth microwave signal into a sawtooth wave signal, which is amplified by the power amplifier 13 until the peak value reaches the half-wave voltage and then input into the optical fiber electro-optic phase modulator 15;

[0022] 4) The sawtooth wave signal is amplified by the power amplifier 13 until the peak value reaches the half-wave voltage and then input into the optical fiber electro-optic phase modulator 15;

[0023] 5) The optical fiber electro-optic phase modulator 15 receives the initial laser with a frequency of ω sent by the laser 14 and the sawtooth wave signal with a frequency of Δω from the power amplifier 13. The initial laser is modulated by the sawtooth wave signal and is frequency-shifted to ω+Δω to become a frequency-shifted laser. The optical fiber electro-optic phase modulator 15 outputs a frequency-shifted laser.

[0024] 6) The spectrum analyzer 16 collects the sawtooth wave signal from the power amplifier output terminal 13, analyzes the sawtooth wave signal to generate harmonic signals of various orders, and inputs the harmonic signals of various orders into the host computer 1;

[0025] 7) The host computer 1 iteratively optimizes the initial values ​​of the frequency, output power and phase of the first microwave signal, the second microwave signal, the third microwave signal and the fourth microwave signal through the microcontroller 2 according to the power of the harmonic signals from the negative fourth order to the positive fourth order in each order of harmonic signals; the spectrum analyzer 16 simultaneously monitors the change in the proportion of the power of the harmonic signals from the negative fourth order to the positive fourth order in each order of harmonic signals. When the power of the positive first order harmonic signal accounts for the highest proportion relative to the total power of the harmonic signals of each order, the first output power optimization is completed.

[0026] 8) After the updated sawtooth wave signal is input into the optical fiber electro-optic phase modulator 15, the optical power of the frequency-shifted laser is obtained using the optical beat frequency spectrum and the scanning Fabry-Perot interferometer, and the host computer 1 iteratively optimizes the initial values ​​of the frequency, output power and phase of the first microwave signal, the second microwave signal, the third microwave signal and the fourth microwave signal through the microcontroller 2; when the optical power of the frequency-shifted laser reaches the maximum value, the second output power optimization is completed.

[0027] The technical effects of the present invention are as follows: compared with the laser frequency shifting method for controlling the current temperature of the laser and the length of the piezoelectric ceramic resonant cavity in the prior art CN 103227415 B, the present invention has higher frequency accuracy and stability; compared with the acousto-optic modulator frequency shifting in CN102519445 B, the present invention has higher bandwidth and optical path stability; when multi-harmonic microwave synthesis generates a sawtooth wave signal, the relative power of each harmonic can be controlled, and the optical signal bandwidth is higher, which is more suitable for an optical fiber electro-optic phase modulator, thereby maximizing the efficiency of the frequency-shifted laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural diagram of a laser phase modulation frequency shifting device based on a multi-harmonic microwave synthesizer of the present invention.

[0029] Figure 2 It is a time domain diagram of the sawtooth wave synthesized by four harmonic signals of the present invention.

[0030] Figure 3 It is a frequency domain diagram of the sawtooth wave synthesized by the four-segment harmonic signal of the present invention.

[0031] Figure 4 It is a flow chart of optimization of the fourth-order harmonic signal by the host computer of the present invention. DETAILED DESCRIPTION

[0032] The specific implementation of the embodiment of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the embodiment of the present invention, and is not used to limit the embodiment of the present invention.

[0033] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0034] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0035] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0037] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0038] The present invention will be described in detail below in conjunction with exemplary embodiments with reference to the accompanying drawings.

[0039] A laser phase modulation frequency shifting device based on a multi-harmonic microwave synthesizer comprises a host computer 1, the host computer 1 is signal-connected to a microcontroller 2 and transmits digital commands to the microcontroller 2;

[0040] The microcontroller 2 is respectively connected to the first microwave generator 3, the second microwave generator 4, the third microwave generator 5, the fourth microwave generator 6, the first digital phase shifter 8, the second digital phase shifter 9, the third digital phase shifter 10 and the fourth digital phase shifter 11;

[0041] The first microwave generator 3, the second microwave generator 4, the third microwave generator 5 and the fourth microwave generator 6 respectively perform serial digital communication with a reference signal source 7 and generate microwave signals; wherein the first microwave signal generated by the first microwave generator 3 is input into the mixer 12 after passing through the first digital phase shifter 8; the second microwave signal generated by the second microwave generator 4 is input into the mixer 12 after passing through the second digital phase shifter 9, and the frequency of the second microwave signal is twice that of the first microwave signal; the third microwave signal generated by the third microwave generator 5 is input into the mixer after passing through the third digital phase shifter 10, and the frequency of the third microwave signal is The fourth microwave signal generated by the fourth microwave generator 6 is input into the mixer 12 after passing through the fourth digital phase shifter 11, and the frequency of the fourth microwave signal is four times that of the first microwave signal; the mixer 12 synthesizes the first microwave signal, the second microwave signal, the third microwave signal and the fourth microwave signal into a sawtooth wave signal, and the sawtooth wave signal is amplified by the power amplifier 13 until the peak value reaches the half-wave voltage and then input into the optical fiber electro-optic phase modulator 15; a spectrum analyzer 16 is connected to the output end of the power amplifier 13, analyzes the sawtooth wave signal and generates harmonic signals of various orders; a spectrum analyzer 16 transmits the harmonic signals of various orders to the host computer 1;

[0042] A laser 14 inputs an initial laser of a fixed frequency to a fiber electro-optic phase modulator 15 through an optical fiber. The fiber electro-optic phase modulator 15 performs phase modulation and frequency shifting on the initial laser according to a sawtooth wave signal and then outputs a frequency-shifted laser.

[0043] The first microwave generator 3, the second microwave generator 4, the third microwave generator 5 and the fourth microwave generator 6 are combined frequency generators of chip-level voltage-controlled oscillators and phase-locked loops of Texas Instruments, which can generate microwave signals up to 15 GHz that are phase-locked to a reference signal. A 100 MHz reference signal source 7 is used as the phase-locked loop reference frequency of the microwave generator, and the microcontroller 2 is used to perform serial digital communication with the four microwave generators to control the frequency and power of the generated microwave signals. The four-way signals are then respectively passed through a first-level digital phase shifter, which has an accuracy of eight bits and can perform phase shifting of the input signal with an accuracy of 1.4°. The microcontroller is used to perform serial digital communication with the four digital phase shifters to achieve relative phase control of the four-way microwave signals.

[0044] The time domain theoretical values ​​of the sawtooth wave signal synthesized by harmonic signals of various orders are as follows: Figure 2 As shown in the figure, the frequency domain theoretical values ​​of each order harmonic signal are as follows Figure 3 As shown, the time domain diagram shows that the synthesized waveform is an approximate sawtooth waveform; the optical frequency domain diagram of laser phase modulation using this waveform can suppress the positive and negative fourth-order harmonic power of the fundamental wave to less than 1.5%, and the positive first-order power can reach more than 73%.

[0045] The mixed sawtooth wave signal is amplified by the power amplifier, and the voltage amplitude is amplified to a half-wave voltage and then input into the optical fiber electro-optic phase modulator. When the initial laser with a frequency of ω output by the laser 14 passes through the phase modulator, the phase is modulated by the sawtooth wave signal with a frequency of Δω and will be shifted to ω+Δω, so that the frequency shift and fast frequency hopping of the laser can be achieved by changing the frequency of the sawtooth waveform.

[0046] The host computer 1 is connected to the microcontroller 2 via serial communication, and the parameters of the sawtooth waveform are optimized by sending the power and phase of the four microwave signals to the microcontroller 2 respectively. The power and phase optimization process of each order harmonic signal is shown in Figure 4 : The spectrum analyzer 16 reads the sawtooth wave signal from the output end of the power amplifier 13 and analyzes the power of each order of harmonic signals therefrom. The host computer 1 performs iterative parameter optimization according to the power of each order of harmonic signals and the fundamental power in the frequency domain of the current sawtooth wave signal. The optimization goal is to achieve the highest suppression ratio of harmonic signals other than the positive first order in the harmonic signals from the negative fourth order to the positive fourth order, and at the same time, the positive first order power accounts for the highest proportion.

[0047] The sawtooth wave is then input into the fiber electro-optic phase modulator 15; the host computer 1 then performs a second round of iterative parameter optimization, using laser spectrum resolution methods such as external optical beat frequency spectrum and scanning Fabry-Perot interferometer to obtain the optical power of the frequency-shifted laser. The optimization goal is to maximize the optical power, and the optimized parameters are used as the parameters of the laser frequency shift at this frequency.

[0048] The technical effects of the present invention are as follows: compared with the laser frequency shifting method of the prior art CN 103227415 B for controlling the current temperature of the laser and the length of the piezoelectric ceramic resonant cavity, the present invention has higher frequency accuracy and stability; compared with the frequency shifting of the acousto-optic modulator in CN 102519445 B, the present invention has higher bandwidth and optical path stability; when the multi-harmonic microwave synthesis generates a sawtooth wave signal, the relative power of each harmonic can be controlled, and the optical signal bandwidth is higher, which is more suitable for the optical fiber electro-optic phase modulator, thereby maximizing the efficiency of the frequency-shifted laser.

[0049] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A laser phase modulation frequency shifting device based on a multi-harmonic microwave synthesizer, characterized in that: The invention comprises a host computer (1), wherein the host computer (1) is connected to a microcontroller (2) by signal and transmits digital commands to the microcontroller (2); The microcontroller (2) is respectively connected to the first microwave generator (3), the second microwave generator (4), the third microwave generator (5), the fourth microwave generator (6), the first digital phase shifter (8), the second digital phase shifter (9), the third digital phase shifter (10) and the fourth digital phase shifter (11); The first microwave generator (3), the second microwave generator (4), the third microwave generator (5) and the fourth microwave generator (6) respectively perform serial digital communication with a reference signal source (7) and generate microwave signals; The first microwave signal generated by the first microwave generator (3) passes through a first digital phase shifter (8) and is then input into a mixer (12); the second microwave signal generated by the second microwave generator (4) passes through a second digital phase shifter (9) and is then input into a mixer (12), and the frequency of the second microwave signal is twice that of the first microwave signal; the third microwave signal generated by the third microwave generator (5) passes through a third digital phase shifter (10) and is then input into the mixer, and the frequency of the third microwave signal is three times that of the first microwave signal; the fourth microwave signal generated by the fourth microwave generator (6) passes through a fourth digital phase shifter (11) and is then input into the mixer, and the frequency of the third microwave signal is three times that of the first microwave signal. (11) is then input into a mixer (12), and the frequency of the fourth microwave signal is four times that of the first microwave signal; the mixer (12) synthesizes the first microwave signal, the second microwave signal, the third microwave signal and the fourth microwave signal into a sawtooth wave signal, and the sawtooth wave signal is amplified by a power amplifier (13) until the peak value reaches the half-wave voltage and then input into an optical fiber electro-optic phase modulator (15); a spectrum analyzer (16) is connected to the output end of the power amplifier (13), analyzes the sawtooth wave signal and generates harmonic signals of various orders; and the spectrum analyzer (16) transmits the harmonic signals of various orders to a host computer (1); A laser (14) inputs an initial laser with a fixed frequency to an optical fiber electro-optic phase modulator (15) through an optical fiber. The optical fiber electro-optic phase modulator (15) performs phase modulation and frequency shifting on the initial laser according to a sawtooth wave signal and then outputs a frequency-shifted laser.

2. The laser phase modulation frequency shifting device based on a multi-harmonic microwave synthesizer according to claim 1, characterized in that: The signal output frequency of the reference signal source (7) is 100 MHz.

3. The laser phase modulation frequency shifting device based on a multi-harmonic microwave synthesizer according to claim 1, characterized in that: The first digital phase shifter (8), the second digital phase shifter (9), the third digital phase shifter (10) and the fourth digital phase shifter (11) have an accuracy of eight bits and can perform phase shift on the input signal with an accuracy of 1.4°.

4. The method for using the laser phase modulation frequency shifting device based on a multi-harmonic microwave synthesizer according to claim 1, comprising the steps of: 1) A reference signal source (7) sends a reference signal to a first microwave generator (3), a second microwave generator (4), a third microwave generator (5) and a fourth microwave generator (6); a host computer (1) sends an instruction to enable the reference signal source (7) to perform serial digital communication with the first microwave generator (3), the second microwave generator (4), the third microwave generator (5) and the fourth microwave generator (6) through a microcontroller (2); 2) With the frequency of the reference signal source (7) as the reference frequency of the phase-locked loop, the first microwave generator (3) generates a first microwave signal, the first microwave signal is input into a mixer (12) after being phase-shifted by a first digital phase shifter (8); the second microwave generator (4) generates a second microwave signal, the second microwave signal is input into a mixer (12) after being phase-shifted by a second digital phase shifter (9), and the frequency of the second microwave signal is twice that of the first microwave signal; the third microwave generator (5) generates a third microwave signal, the third microwave signal is input into the mixer after being phase-shifted by a third digital phase shifter (10), and the frequency of the third microwave signal is three times that of the first microwave signal; the fourth microwave generator (6) generates a fourth microwave signal, the fourth microwave signal is input into the mixer (12) after being phase-shifted by a fourth digital phase shifter (11), and the frequency of the fourth microwave signal is four times that of the first microwave signal; 3) The mixer (12) synthesizes the first microwave signal, the second microwave signal, the third microwave signal and the fourth microwave signal into a sawtooth wave signal, and the sawtooth wave signal is amplified by the power amplifier (13) until the peak value reaches the half-wave voltage and then input into the optical fiber electro-optic phase modulator (15); 4) The sawtooth wave signal is amplified by a power amplifier (13) until its peak value reaches the half-wave voltage and then input into an optical fiber electro-optic phase modulator (15); 5) The optical fiber electro-optic phase modulator (15) receives the initial laser light with a frequency of ω sent by the laser (14) and the sawtooth wave signal with a frequency of Δω from the power amplifier (13). The initial laser light is modulated by the sawtooth wave signal and is frequency-shifted to ω+Δω, thus becoming a frequency-shifted laser light; The optical fiber electro-optic phase modulator (15) outputs frequency-shifted laser light; 6) The spectrum analyzer (16) collects the sawtooth wave signal from the output end (13) of the power amplifier, analyzes the sawtooth wave signal to generate harmonic signals of various orders, and inputs the harmonic signals of various orders into the host computer (1); 7) The upper computer (1) iteratively optimizes the initial values ​​of the frequency, output power and phase of the first microwave signal, the second microwave signal, the third microwave signal and the fourth microwave signal through the microcontroller (2) according to the power of the harmonic signals from the negative fourth order to the positive fourth order in the harmonic signals of each order; the spectrum analyzer (16) simultaneously monitors the change in the proportion of the power of the harmonic signals from the negative fourth order to the positive fourth order in the harmonic signals of each order, and when the power of the harmonic signal of the positive first order has the highest proportion relative to the total power of the harmonic signals of each order, the first output power optimization is completed. 8) After the updated sawtooth wave signal is input into the optical fiber electro-optic phase modulator (15), the optical power of the frequency-shifted laser is obtained using an external optical beat frequency spectrum and a scanning Fabry-Perot interferometer, and the host computer (1) iteratively optimizes the initial values ​​of the frequency, output power and phase of the first microwave signal, the second microwave signal, the third microwave signal and the fourth microwave signal through a microcontroller (2); when the optical power of the frequency-shifted laser reaches a maximum value, the second output power optimization is completed.

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