A hybrid integrated high-precision optical frequency synthesizer

Abstract

The present invention provides a hybrid integrated high-precision optical frequency synthesizer. Its structure includes a pump laser core 4, a 2μm laser, a narrow linewidth tunable laser, a first modulator, a second modulator, a low repetition rate optical frequency comb, a high repetition rate optical frequency comb, a waveguide frequency doubler, and a frequency-stabilized microwave reference module. The present invention inputs two optical frequency combs, a high repetition rate optical frequency comb and a low repetition rate optical frequency comb, into a tunable laser to form an output of an optical frequency synthesizer. The octave self-reference optical frequency comb has a wider spectral range. By self-calibration, the comb tooth line width of the low repetition rate optical frequency comb can be narrowed and the expansion range is also narrower. The comb tooth spacing is set by a stable and accurate microwave reference clock. By stabilizing the phase of the comb tooth spacing and the octave optical frequency comb, high-precision optical frequency synthesis is achieved.

Description

Technical Field

[0001] The invention relates to an optical frequency synthesizer, in particular to a hybrid integrated high-precision optical frequency synthesizer. Background Art

[0002] The research on frequency synthesizers stems from the demand for accurate, stable and efficient frequency sources in modern communications, navigation, radar and other fields. Microwave frequency synthesizers are often used to generate any required frequency in the microwave band and have been widely used in scientific research and industrial production. As a remarkable technological innovation, optical frequency synthesizers have attracted widespread attention in the field of photonics. Optical frequency synthesizers have great application potential in the fields of large-capacity satellite laser communications, environmental atmospheric monitoring, deep space physics, high-resolution spectral satellites, etc. However, traditional optical frequency synthesizers have limitations in structure, volume, weight, power consumption and cost, so they have been limited to use in laboratories and are greatly restricted in practical applications. Summary of the invention

[0003] The purpose of the present invention is to provide a hybrid integrated high-precision optical frequency synthesizer to solve the problem that traditional frequency synthesizers are difficult to be applied in practical work due to their complex structure, high cost and power consumption.

[0004] The present invention is achieved in that:

[0005] A hybrid integrated high-precision optical frequency synthesizer, comprising:

[0006] The pump laser chip is connected to the first modulator and the second modulator respectively to provide the required optical synthesis signal;

[0007] A first modulator is connected to the pump laser chip and the low repetition rate optical frequency comb respectively, and is used to independently control the low repetition rate optical frequency comb;

[0008] The low repetition rate optical frequency comb is respectively connected to the first modulator, the 2μm laser chip, the waveguide frequency multiplier, the frequency-stabilized microwave reference module and the narrow linewidth tunable laser, and is used to match the comb tooth frequency of the high repetition rate optical frequency comb to provide precise frequency synthesis reference and signal relay;

[0009] A second modulator is connected to the pump laser chip and the high repetition rate optical frequency comb, respectively, and is used for independently controlling the high repetition rate optical frequency comb;

[0010] The high repetition rate optical frequency comb is respectively connected to the second modulator, the 2μm laser chip, the waveguide frequency doubler, the frequency-stabilized microwave reference module, the low repetition rate optical frequency comb and the narrow linewidth tunable laser to provide a self-reference of the frequency-doubled signal;

[0011] A narrow linewidth tunable laser is connected to a 2μm laser chip, a waveguide frequency doubler, a frequency-stabilized microwave reference module, and a low-repetition-rate optical frequency comb, respectively, to excite the optical frequency comb;

[0012] The 2μm laser chip is connected to a waveguide frequency doubler, a frequency-stabilized microwave reference module, a low-repetition-rate optical frequency comb, a high-repetition-rate optical frequency comb, and a narrow-linewidth tunable laser, respectively, to provide spectrum broadening for the waveguide frequency doubler;

[0013] The waveguide frequency doubler is connected to the 2μm laser chip, the low repetition rate optical frequency comb, the high repetition rate optical frequency comb, the frequency-stabilized microwave reference module, and the narrow linewidth tunable laser to broaden the range of the working spectrum;

[0014] The frequency-stabilized microwave reference module is connected to the low-repetition-rate optical frequency comb, high-repetition-rate optical frequency comb, 2μm laser chip and narrow-linewidth tunable laser respectively, and is used to lock the THz frequency interval of the high-repetition-rate optical frequency comb and assist in controlling the precise tuning of the narrow-linewidth tunable laser.

[0015] Furthermore, a frequency generation and transfer module is formed by a pump laser chip, a first modulator, a second modulator, a high repetition rate optical frequency comb and a low repetition rate optical frequency comb; the frequency generation and transfer module is used to lock the high repetition rate optical frequency comb and the low repetition rate optical frequency comb with each other, and use the two optical frequency combs as transfer oscillators to synthesize the output with a narrow linewidth tunable laser to obtain an optical synthetic signal.

[0016] Furthermore, a dissipative Kerr double comb system is formed by a low repetition rate optical frequency comb and a high repetition rate optical frequency comb; the dissipative Kerr double comb system realizes coherent multiplication from microwave to light wave by precisely controlling the comb tooth spacing and bias frequency to ensure accurate synchronization of signals. The low repetition rate optical frequency comb has a GHz mode spacing and uses an optical fiber cavity; the high repetition rate optical frequency comb has a THz mode spacing and uses a double-bandwidth silicon nitride micro-resonant cavity.

[0017] Furthermore, a self-reference locking module is formed by a 2μm laser chip and a waveguide frequency doubler; the self-reference locking module is used to lock the low repetition rate optical frequency comb and the high repetition rate optical frequency comb to each other. The self-reference locking module adopts a specific locking technology to ensure the stability and accuracy of frequency synthesis. The bias frequency is controlled by intensity modulation and a free space acousto-optic modulator. The frequency is measured by measuring the optical heterodyne beat frequency between the two optical frequency combs and fed back to the pump laser chip to achieve frequency stability.

[0018] Furthermore, the self-reference locking module is integrated with a narrow linewidth tunable laser to form a frequency synthesis module for outputting optical synthetic signals.

[0019] Furthermore, the pump laser chip works in conjunction with a narrow linewidth tunable laser to provide an optical synthetic signal required by the system; the pump laser chip serves as a shared pump source for a low repetition rate optical frequency comb and a high repetition rate optical frequency comb, and independently controls the low repetition rate optical frequency comb and the high repetition rate optical frequency comb using a single sideband frequency shifter and an erbium-doped fiber amplifier.

[0020] The present invention inputs two optical frequency combs, a high repetition rate optical frequency comb and a low repetition rate optical frequency comb, into a tunable laser to form the output of an optical frequency synthesizer. The octave self-reference optical frequency comb has a wider spectral range. By self-calibration, the comb line width of the low repetition rate optical frequency comb can be narrowed and the extension range is also narrower. The comb tooth spacing is set by a stable and accurate microwave reference clock. By stabilizing the phase of the comb tooth spacing and the octave optical frequency comb, high-precision optical frequency synthesis is achieved.

[0021] The present invention uses a pump laser chip to branch two optical frequency combs, and uses a single-sideband frequency shifter and an optical amplifier to independently control each optical frequency comb. Octave solitons will appear in the spectrum at the dispersion peaks at 1μm and 2μm. However, this THz spacing frequency output is not easily detected by a spectrometer, so a low repetition rate optical frequency comb is used to make up for the mode gap. The frequency is measured by detecting the optical heterodyne beat frequency between the two optical frequency combs 1THz away from the pump, and after feeding it back to the frequency of the pump laser, the signal is locked to the synthetic radio frequency, and the carrier envelope detuning frequency is locked by using the double frequency spanning relationship between the 2μm THz peak and the 1μm dispersion peak. Finally, with the dual optical frequency comb as the backbone, the narrow linewidth tunable laser is guided to perform arbitrary optical frequency synthesis. The system measures the frequency by measuring the optical heterodyne beat frequency between the two optical frequency combs, and feeds back the measured signal to the frequency of the pump laser, and achieves frequency stability by phase locking to the synthetic radio frequency.

[0022] The present invention creates a self-referenced microwave-optical link by integrating optoelectronic chips such as high-power pump laser chips, high-repetition rate optical frequency combs, low-repetition rate optical frequency combs, and waveguide doublers. The present invention utilizes the design concept of a large cavity within a small cavity, coordinates a dual-frequency comb, combines the processing technology of active devices and a hybrid connection scheme, and realizes the integration of cross-feedback, signal interconnection, and wavelength tuning, thereby achieving large-bandwidth, high-precision, and high-stability optical frequency synthesis, effectively solving the problems of complex structure and high power consumption of traditional frequency synthesizers.

[0023] The present invention utilizes the design concept of a large cavity within a small cavity, integrates a high repetition rate optical frequency comb and a low repetition rate optical frequency comb, locks the two optical frequency combs to each other, and integrates a narrow linewidth tunable co-laser to form a frequency synthesis module for optical signal output. A dual-locked optical comb combination with co-pump excitation and hybrid integration is established to construct coherent optical frequency generation and transmission, a high repetition rate microcavity optical frequency comb is designed for self-reference, and a low repetition rate optical frequency comb is designed for precision frequency synthesis reference through frequency matching, and a nonlinear self-reference locking module is established in combination with a waveguide optical frequency multiplier; a dual-comb frequency relay scheme based on cross-locking is implemented, and a coordinated dual-frequency comb is used to study dispersion precision control technology, which meets the precise positioning of the mutual reference frequency and achieves a full-chain breakthrough in the generation and control of hybrid integrated high-precision optical frequency synthesis.

[0024] The beneficial effects of the present invention are as follows:

[0025] 1. The new paradigm of high and low repetition rate interlocked optical combs and the new mechanism of frequency relay transmission proposed in this invention fundamentally break through the bottleneck dilemma of multi-wave frequency synthesis light source "both frequency doubling and large bandwidth and precise tunability", and realize the organic integration of high efficiency, broadband, stability and tunability in integrated optical frequency synthesis.

[0026] 2. The new self-referenced scheme of integrated amplification and waveguide frequency doubling proposed in the present invention achieves an overall breakthrough in collaborative control mode interaction, frequency conversion phase matching and conversion efficiency improvement, forming an integrated "cavity + waveguide" intensive reference locking technology and a new device / module combination.

[0027] 3. The present invention constructs a new optical frequency synthesis scheme based on hybrid integration. The whole system integrates multiple materials, structures and optoelectronic combination schemes, realizes integrated and precise cross-feedback control of optics, electricity and heat in the time-frequency dimension, and realizes new performance of accurate synthesis and fine tuning of large-bandwidth optical frequencies. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a working principle diagram of the optical frequency synthesizer of the present invention.

[0029] Figure 2 It is a system configuration diagram of the optical frequency synthesizer of the present invention.

[0030] Figure 3 It is the spectrum output diagram of the optical frequency synthesizer of the present invention.

[0031] Figure 4 This is the spectral output of a low-repetition-rate optical frequency comb.

[0032] Figure 5 It is a diagram of the optical signal output of the optical frequency synthesizer of the present invention.

[0033] In the figure: 1. Frequency generation and transmission module; 2. Frequency synthesis module; 3. Self-reference locking module; 4. Pump laser chip; 5. 2μm laser chip; 6. Narrow linewidth tunable laser; 7. First modulator; 8. Low repetition rate optical frequency comb; 9. High repetition rate optical frequency comb; 10. Waveguide doubler; 11. Frequency-stabilized microwave reference module; 12. Second modulator. DETAILED DESCRIPTION

[0034] like Figure 2 As shown, the optical frequency synthesizer of the present invention includes a pump laser chip 4, a 2μm laser 5, a narrow linewidth tunable laser 6, a first modulator 7, a second modulator 12, a low repetition rate optical frequency comb 8, a high repetition rate optical frequency comb 9, a waveguide multiplier 10 and a frequency-stabilized microwave reference module 11.

[0035] Among them, the output of the pump laser chip 4 is connected to the first modulator 7 and the second modulator 12 respectively to provide the required optical synthesis signal. The first modulator 7 is connected to the pump laser chip 4 and the low repetition rate optical frequency comb 8 respectively, and is used to independently control the low repetition rate optical frequency comb 8. The low repetition rate optical frequency comb 8 is connected to the first modulator 7, the 2μm laser chip 5, the waveguide frequency multiplier 10, the frequency-stabilized microwave reference module 11 and the narrow linewidth tunable laser 6 respectively, and is used to match the comb tooth frequency of the high repetition rate optical frequency comb 9 to provide precise frequency synthesis reference and signal relay. The second modulator 12 is connected to the pump laser chip 4 and the high repetition rate optical frequency comb 9 respectively, and is used to independently control the high repetition rate optical frequency comb 9. The high repetition rate optical frequency comb 9 is connected to the second modulator 12, the 2μm laser chip 5, the waveguide frequency doubler 10, the frequency-stabilized microwave reference module 11, the low repetition rate optical frequency comb 8 and the narrow linewidth tunable laser 6, respectively, to provide a self-reference of the frequency-doubled signal. The narrow linewidth tunable laser 6 is connected to the 2μm laser chip 5, the waveguide frequency doubler 10, the frequency-stabilized microwave reference module 11 and the low repetition rate optical frequency comb 8, respectively, to excite the optical frequency comb; the 2μm laser chip 5 is connected to the waveguide frequency doubler 10, the frequency-stabilized microwave reference module 11, the low repetition rate optical frequency comb 8, the high repetition rate optical frequency comb 9 and the narrow linewidth tunable laser 6, respectively, to provide spectrum broadening for the waveguide frequency doubler 10. The waveguide frequency doubler 10 is connected to the 2μm laser chip 5, the low repetition rate optical frequency comb 8, the high repetition rate optical frequency comb 9, the frequency-stabilized microwave reference module 11, and the narrow linewidth tunable laser 6, respectively, to broaden the range of the working spectrum. The frequency-stabilized microwave reference module 11 is connected to the low repetition rate optical frequency comb 8, the high repetition rate optical frequency comb 9, the 2μm laser chip 5, and the narrow linewidth tunable laser 6, respectively, to lock the THz frequency interval of the high repetition rate optical frequency comb and assist in controlling the precise tuning of the narrow linewidth tunable laser.

[0036] Figure 2In the present invention, a frequency generation and transfer module 1 is formed by a pump laser chip 4, a first modulator 7, a second modulator 12, a high repetition rate optical frequency comb 9 and a low repetition rate optical frequency comb 8. The frequency generation and transfer module 1 realizes the integration of the high repetition rate optical frequency comb 9 and the low repetition rate optical frequency comb 8 by adopting the design concept of a large cavity within a small cavity, and by locking the two optical frequency combs with each other and integrating a narrow linewidth tunable laser 6, the two optical frequency combs are used as transfer oscillators by utilizing the transfer oscillator principle, and the output is synthesized with the narrow linewidth tunable laser 6 to obtain an optical synthetic signal.

[0037] The pump laser chip 4 works in conjunction with the narrow linewidth tunable laser 6 to provide the optical synthesis signal required by the system. The pump laser chip 4 serves as a shared pump source for the low repetition rate optical frequency comb 8 and the high repetition rate optical frequency comb 9, and independently controls the low repetition rate optical frequency comb 8 and the high repetition rate optical frequency comb 9 using a single sideband frequency shifter and an erbium-doped fiber amplifier.

[0038] Figure 2 In the present invention, a dissipative Kerr double-comb system is formed by a low repetition rate optical frequency comb 8 and a high repetition rate optical frequency comb 9. The dissipative Kerr double-comb system realizes coherent multiplication from microwave to light wave by precisely controlling the comb tooth spacing and bias frequency to ensure accurate synchronization of signals. The low repetition rate optical frequency comb 8 has a mode spacing of 22 GHz and uses an optical fiber cavity; the high repetition rate optical frequency comb 9 has a mode spacing of 1 THz and uses a double-frequency-width silicon nitride micro-resonant cavity. The dissipative Kerr double-comb system realizes coherent multiplication from microwave to light wave by precisely controlling the comb tooth spacing (f rep,THz and f rep,GHz ) and the bias frequency of the silicon nitride comb (f ceo,THz ), realizing the coherent multiplication from microwave to light wave, ensuring the precise synchronization of signals.

[0039] The frequency generation and transfer module 1 is a microcomb reference source. In order to generate two dissipative Kerr optical frequency combs, the present invention uses a high-power pump laser chip 4 and uses a first modulator 7 and a second modulator 12 to independently control each optical frequency comb. In the silicon nitride planar waveguide coupled resonator, a single pulse soliton spanning an octave was successfully generated.

[0040] The spectral output of the high repetition rate optical frequency comb 9 is as follows Figure 3As shown. Through waveguide dispersion engineering, the present invention produces dispersion peaks at 999nm and 2190nm in the optical power, which is due to the zero-integrated GVD starting from the pump wavelength. By intentionally mismatching the radius of the microresonator, the present invention uses a narrowband intracavity filter to select the desired longitudinal mode, achieving a high side mode suppression ratio. However, the comb tooth spacing of the high repetition rate optical frequency comb 9 is in the THz order, which is not easily detected by light and will be reduced to microwave frequency using traditional electronic equipment. Therefore, the present invention relies on the low repetition rate optical frequency comb 8 to make up for the gap between the high repetition rate terahertz comb modes.

[0041] The spectral output of the low repetition rate optical frequency comb 8 is shown in Figure 4 As shown, it has a mode spacing of 22 GHz. By using optical detection technology, the f clk The microwave-optical frequency chain is stable to 22 GHz, which provides the basis for the stability of the fiber cavity reference comb. The 50th relative comb line of the low repetition rate optical frequency comb 8 is used to lock the THz frequency interval of the high repetition rate optical frequency comb 9, thereby guiding the precise tuning of the tunable laser synthesizer.

[0042] Figure 2 In the present invention, a 2μm laser chip 5 and a waveguide frequency doubler 10 constitute a self-reference locking module 3. The self-reference locking module 3 is used to lock the low repetition rate optical frequency comb and the high repetition rate optical frequency comb to each other. The self-reference locking module 3 adopts a specific locking technology to ensure the stability and accuracy of frequency synthesis. The bias frequency is controlled by intensity modulation and a free space acousto-optic modulator. The optical heterodyne beat frequency between the two optical frequency combs is measured to measure the frequency, and is fed back to the pump laser chip 1 to achieve frequency stability.

[0043] The present invention adopts the framework of a traditional optical-microwave synthesizer, with a narrow linewidth tunable laser 6 as its core, which is responsible for generating a tunable optical signal with C-band tunable characteristics, narrow linewidth and fast frequency control capabilities, and locking it to a stable micro-comb reference source.

[0044] The self-reference locking module 3 is integrated with the narrow linewidth tunable laser 6, and together with the semiconductor optical amplifiers in the two modulators, a frequency synthesis module is formed to output optical synthetic signals. At room temperature, the narrow linewidth tunable laser 6 can emit up to 4mW of continuous wave power, while the semiconductor optical amplifier provides a small signal gain of more than 10dB. The laser consists of a gain section, a phase section, and two high-quality factor microresonators, which are realized by heterogeneously integrated InP-based electrically pumped quantum wells on a silicon waveguide. Thermal heating of the silicon microresonator and the passive phase section is accomplished by injecting current into a metal heater above the waveguide.

[0045] The self-reference of the self-reference locking module 3 is achieved by using an amplified laser to provide power to the waveguide frequency doubler in order to determine the absolute frequency of each comb line, achieving a high signal-to-noise ratio and phase-locking to the radio frequency, completing the stability transfer from the micro-comb reference source to the terahertz comb line.

[0046] The frequency is measured by measuring the optical heterodyne beat frequency between two optical frequency combs at a frequency difference of 1 THz from the pump laser. After eliminating the relative contribution of the single-sideband frequency shifter, the measured signal is fed back to the pump laser frequency and phase-locked to the synthetic radio frequency f 1 =αf clk (where α is the ratio of two integers) to achieve frequency stability. In this way, not only f rep,THz The frequency of f clk The stability of the silicon nitride terahertz comb was successfully transferred to the THz comb teeth. For each silicon nitride terahertz comb line, the terahertz frequency was locked by exploiting the frequency-doubling spanning relationship between the terahertz line at 1,998nm and the dispersion peak at 999nm.

[0047] The present invention uses a high-power pump laser chip 4 as a shared pump source for two micro-resonant comb generators. The output of the 3dB splitter is used for the LiNbO 3 Single sideband modulator and erbium-doped fiber amplifier. The frequency detuning produced by each microcomb resonance is controlled by an amplified voltage controlled oscillator and arbitrary waveform generator, generating a voltage ramp. In this way, a single soliton can be generated on the silicon nitride and fiber cavity microcombs by linear voltage ramps of 5 GHz within 100 ns and 100 MHz within 3 μs, respectively. Once the soliton is started, feedback controls the frequency of each voltage controlled oscillator, ensuring appropriate device matching for GHz and terahertz frequencies.

[0048] Intensity modulation on a silicon nitride microcomb to control f ceo,THz , and controlled by a free-space acousto-optic modulator. A lensed fiber with a 2.5μm spot size was used to couple the silicon nitride chip, with an insertion loss of 7dB per facet. During operation, the on-chip pump power of the silicon nitride microcomb was about 160mW, which is 10 times the threshold for soliton generation. 80mW was coupled to the fiber cavity microcomb using a tapered single-mode fiber, generating solitons at 12 times the soliton threshold.

[0049] In order to achieve f-2f self-reference, that is, to determine the absolute frequency of each comb line, the present invention uses an independent 2μm laser chip 5 to provide 9mW power for the waveguide doubler 10 to achieve f ceo,THz Finally, the signal is phase-locked to the RF f 2 =βf clk, and by feeding back to the silicon nitride pump power, the clk The stability of all terahertz comb lines spanning 130 THz to 300 THz is transferred. A signal, the f-beat laser, is generated by heterodyning the DKS dual-comb signal in the opposite mode of the pump. This signal is input into a phase-locked loop (PLL) based on a field programmable gate array (FPGA) with a local oscillator of f 3 =γf clk , digitally divided by 512. Ultimately, the laser is locked to the DKS dual comb, producing a fully stable, tunable synthesizer output. The adjustable output range of the optical frequency synthesizer is as follows: Figure 5 shown.

[0050] The working process of the optical frequency synthesizer of the present invention includes the following steps: (1) starting the pump laser and the tunable laser to provide a laser source; (2) generating high repetition rate and low repetition rate optical frequency combs through a frequency generation and transmission module; (3) using a self-reference locking module to lock the two optical frequency combs; (4) outputting a stable optical signal through a frequency synthesis module.

[0051] like Figure 1 As shown, the working principle of the optical frequency synthesizer of the present invention is: using the idea of ​​a large cavity in a small cavity, integrating a high repetition rate optical frequency comb 9 and a low repetition rate optical frequency comb 8, and locking the two optical frequency combs to each other, and integrating a narrow linewidth tunable laser to form a frequency synthesis module 2 for optical signal output. The high repetition rate optical frequency comb 9 has a wider spectral range, but the comb tooth line width is relatively large; the low repetition rate optical frequency comb 8 has a narrower comb tooth line width and a narrower extension range. These comb tooth spacings are set by a stable and accurate microwave reference clock. A high-precision optical frequency synthesizer is achieved by phase stabilizing the comb spacing and the octave optical frequency comb. Two optical frequency combs are generated using an external cavity pump laser, and each comb is independently controlled using a single-sideband frequency shifter and an optical amplifier. Octave solitons appear in the spectrum at dispersion peaks at 1μm and 2μm. However, the frequency output of this THz spacing is not easily detected by a spectrometer, so a low repetition rate frequency comb is used to make up for the mode gap. The frequency is measured by detecting the optical heterodyne beat frequency between the two combs at a distance of 1 THz from the pump, and after feeding back to the frequency of the pump laser, the signal is locked to the synthetic radio frequency, and the locking is achieved by using the frequency-doubled spanning relationship of the 2μm THz peak and the 1μm dispersion peak. Finally, the dual optical frequency comb is used as the backbone to guide the tunable laser to perform arbitrary optical frequency synthesis.

Claims

1. A hybrid integrated high-precision optical frequency synthesizer, characterized in that: include: A pump laser chip is connected to the first modulator and the second modulator respectively, and is used to provide the required optical synthesis signal; A first modulator is connected to the pump laser chip and the low repetition rate optical frequency comb, respectively, and is used to independently control the low repetition rate optical frequency comb; The low repetition rate optical frequency comb is respectively connected to the first modulator, the 2μm laser chip, the waveguide frequency multiplier, the frequency-stabilized microwave reference module and the narrow linewidth tunable laser, and is used to match the comb tooth frequency of the high repetition rate optical frequency comb to provide precise frequency synthesis reference and signal relay; A second modulator is connected to the pump laser chip and the high repetition rate optical frequency comb, respectively, and is used for independently controlling the high repetition rate optical frequency comb; The high repetition rate optical frequency comb is respectively connected to the second modulator, the 2μm laser chip, the waveguide frequency doubler, the frequency-stabilized microwave reference module, the low repetition rate optical frequency comb and the narrow linewidth tunable laser to provide a self-reference of the frequency-doubled signal; A narrow linewidth tunable laser is connected to a 2μm laser chip, a waveguide frequency doubler, a frequency-stabilized microwave reference module, and a low-repetition-rate optical frequency comb, respectively, to excite the optical frequency comb; The 2μm laser chip is connected to a waveguide frequency doubler, a frequency-stabilized microwave reference module, a low-repetition-rate optical frequency comb, a high-repetition-rate optical frequency comb, and a narrow-linewidth tunable laser, respectively, to provide spectrum broadening for the waveguide frequency doubler; The waveguide frequency doubler is connected to the 2μm laser chip, the low repetition rate optical frequency comb, the high repetition rate optical frequency comb, the frequency-stabilized microwave reference module, and the narrow linewidth tunable laser to broaden the range of the working spectrum; The frequency-stabilized microwave reference module is connected to the low-repetition-rate optical frequency comb, high-repetition-rate optical frequency comb, 2μm laser chip and narrow-linewidth tunable laser respectively, and is used to lock the THz frequency interval of the high-repetition-rate optical frequency comb and assist in controlling the precise tuning of the narrow-linewidth tunable laser.

2. The optical frequency synthesizer according to claim 1, characterized in that: A frequency generation and transfer module is composed of a pump laser chip, a first modulator, a second modulator, a high repetition rate optical frequency comb and a low repetition rate optical frequency comb; the frequency generation and transfer module is used to lock the high repetition rate optical frequency comb and the low repetition rate optical frequency comb with each other, and use the two optical frequency combs as transfer oscillators to synthesize the output with a narrow linewidth tunable laser to obtain an optical synthetic signal.

3. The optical frequency synthesizer according to claim 1 or 2, characterized in that: A dissipative Kerr double-comb system is composed of a low-repetition-rate optical frequency comb and a high-repetition-rate optical frequency comb. The dissipative Kerr double-comb system realizes coherent multiplication from microwaves to light waves by precisely controlling the comb tooth spacing and the bias frequency to ensure accurate synchronization of signals. The low-repetition-rate optical frequency comb has a mode spacing of GHz and uses an optical fiber cavity. The high-repetition-rate optical frequency comb has a mode spacing of THz and uses a double-bandwidth silicon nitride micro-resonant cavity.

4. The optical frequency synthesizer according to claim 1, characterized in that: A self-reference locking module is formed by a 2μm laser chip and a waveguide frequency doubler; the self-reference locking module is used to mutually lock a low repetition rate optical frequency comb and a high repetition rate optical frequency comb.

5. The optical frequency synthesizer according to claim 4, characterized in that: The self-reference locking module is integrated with the narrow linewidth tunable laser to form a frequency synthesis module for outputting optical synthesis signals.

6. The optical frequency synthesizer according to claim 1, characterized in that: The pump laser chip works in conjunction with a narrow linewidth tunable laser to provide the optical synthetic signal required by the system; the pump laser chip serves as a shared pump source for a low repetition rate optical frequency comb and a high repetition rate optical frequency comb, and uses a single-sideband frequency shifter and an erbium-doped fiber amplifier to independently control the low repetition rate optical frequency comb and the high repetition rate optical frequency comb.

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