Microcavity Kerr soliton optical frequency comb generation method and system based on tunable Raman gain

Abstract

The present invention discloses a method and system for generating a Kerr soliton optical frequency comb based on adjustable Raman gain. The system comprises: a pump laser, a first polarization controller, a first optical amplifier, a first circulator, a control laser, a second polarization controller, a second optical amplifier, a second circulator, an optical microcavity, a first beam splitter, a spectrum analyzer, a second beam splitter, a fiber Bragg grating, a high-speed detector, a spectrum analyzer, a photodetector, and an oscilloscope. The present invention controls the gain and Q value of the Raman mode by controlling the laser, thereby increasing the power threshold for generating the Raman optical frequency comb and regulating the interaction between the two nonlinear effects of Kerr and Raman, thereby generating a Kerr soliton optical frequency comb with a high repetition rate, a wide spectrum, and a high degree of coherence.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical devices, and in particular relates to a method and system for generating a microcavity Kerr soliton optical frequency comb based on adjustable Raman gain. Background Art

[0002] The microcavity Kerr soliton optical frequency comb is a miniaturized optical frequency comb with high coherence, a wide octave bandwidth, and a repetition rate that covers the microwave to terahertz band. It is generated based on a dual balance of dispersion and nonlinearity, as well as gain and loss. As a miniaturized coherent frequency comb source, it provides a high-resolution, high-precision, and high-accuracy frequency standard for optical precision measurement and is widely used in numerous scientific research fields, including ultrafast precision ranging, time-frequency reference transfer, and quantum computing. As optical communication technologies and radar systems evolve toward higher frequencies, higher requirements are being placed on the repetition rate, phase noise characteristics, and integration of optical frequency combs. Research on miniaturized Kerr soliton optical frequency comb sources with microwave repetition rates and low phase noise has become a pressing task.

[0003] In recent years, extensive research has been conducted on microcavity Kerr soliton frequency combs. Kerr soliton combs have been generated in microcavities made of various materials, including SiO₂, SiN, and MgF₂ (e.g., CN 111987580 A, CN 108616030 A, CN117394126 A, CN 111600192 A, and CN 117712815 A). Applications have also been explored in numerous fields, including low-phase-noise microwave generation and frequency synthesis, astronomical spectroscopy, dual-comb spectroscopy, and parallel coherent communications (e.g., CN115754922 A, CN212062984 A, and CN 116106921 A). However, stimulated Raman scattering (SRS) naturally exists in microcavities. This effect arises from the interaction between pump light and the vibrational energy levels of the microcavity molecules. This effect not only produces Raman self-frequency shifts of Kerr solitons but also hinders the formation of Kerr soliton frequency combs through Kerr-Raman nonlinear competition. This effect is particularly pronounced in SiO2 microcavities, where the Raman gain is relatively broad. The competition and complex interaction between the two different nonlinear effects make it difficult to enhance or suppress the Raman process in microcavities, thus limiting the formation of mode-locked Kerr soliton optical frequency combs.

[0004] To generate Kerr soliton frequency combs, it is necessary to manipulate the nonlinear interaction between Raman scattering and four-wave mixing parametric oscillation (FWM). Commonly used methods include microcavity size control, pump power adjustment, coupling loss regulation, and dispersion control. However, these methods impose certain requirements on the microcavity size, which affects the repetition rate control range. Furthermore, the size, coupling spacing, and geometric dispersion are difficult to change after the microcavity is fabricated. Summary of the Invention

[0005] The present invention aims to address the deficiencies of the above-mentioned prior art and proposes a method and system for generating a microcavity Kerr soliton optical frequency comb based on adjustable Raman gain, in order to obtain a high-coherence, low-noise Kerr soliton optical frequency comb, thereby realizing the generation of a Kerr soliton optical frequency comb with high repetition rate, wide spectrum and high coherence.

[0006] In order to achieve the above-mentioned object, the present invention adopts the following technical solutions:

[0007] The present invention provides a Kerr soliton optical frequency comb generation system based on adjustable Raman gain, which comprises: a pump laser, a first polarization controller, a first optical amplifier, a first circulator, a control laser, a second polarization controller, a second optical amplifier, a second circulator, an optical microcavity, a first beam splitter, a spectrum analyzer, a second beam splitter, a fiber Bragg grating, a high-speed detector, a spectrum analyzer, a photodetector, and an oscilloscope;

[0008] The pump laser generates a pump laser, and the polarization state of the pump laser is regulated by the first polarization controller. The first optical amplifier amplifies the power of the regulated pump laser. The first circulator inputs the amplified pump laser into the optical microcavity to generate a Kerr optical frequency comb.

[0009] At the same time, the control laser generates a control laser, and the polarization state of the control laser is regulated by the second polarization controller. The second optical amplifier amplifies the power of the regulated control laser. The second circulator inputs the amplified control laser into the optical microcavity to regulate the Raman gain of the microcavity mode, thereby regulating the Kerr optical frequency comb to a soliton state, and the second circulator outputs the Kerr soliton optical frequency comb.

[0010] The first beam splitter splits the Kerr soliton optical frequency comb, wherein the first split Kerr optical comb enters the optical spectrum analyzer for observation and recording, and the second split Kerr optical comb passes through the second beam splitter to obtain a third split Kerr optical comb and a fourth split signal;

[0011] The third split Kerr optical comb is input into a fiber Bragg grating for filtering, and then a high-speed detector converts the filtered optical comb beat frequency signal into a radio frequency signal, and finally the spectrum analyzer observes and records the radio frequency signal;

[0012] The fourth split beam signal is photoelectrically converted by the photodetector and then input into the oscilloscope to obtain a microcavity transmission spectrum signal.

[0013] The Kerr soliton optical frequency comb generation system based on adjustable Raman gain described in the present invention is also characterized in that the pump laser and control laser are external cavity tuned continuous lasers, whose wavelength and output power can be tuned, and are used to inject continuous single-frequency optical signals into the optical microcavity to serve as pump light and control light.

[0014] The fiber Bragg grating has a band-stop characteristic and is used to filter out the pump light signal in the Kerr soliton optical frequency comb.

[0015] The high-speed photodetector operates in the microwave band, has a bandwidth greater than the frequency of the Kerr optical frequency comb beat signal, and is used to output the beat signal in the radio frequency band. The output end of the high-speed photodetector is connected to the spectrum analyzer.

[0016] The present invention provides a method for generating a microcavity Kerr soliton optical frequency comb. The method is characterized in that the method is applied to a Kerr soliton optical frequency comb generation system consisting of a pump laser, a first polarization controller, a first optical amplifier, a first circulator, a control laser, a second polarization controller, a second optical amplifier, a second circulator, an optical microcavity, a first beam splitter, a spectrum analyzer, a second beam splitter, a fiber Bragg grating, a high-speed detector, a spectrum analyzer, a photodetector, and an oscilloscope, and is performed according to the following steps:

[0017] Step 1: The control laser generates a control laser, and after the polarization state of the control laser is regulated by a second polarization controller, the regulated control laser is amplified by the second optical amplifier. The amplified control laser is then passed through the second circulator and inputted back into the optical microcavity to form a second light beam.

[0018] Step 2: adjusting the wavelength of the control laser so that the second light beam excites a forward Raman mode spectrum in the optical microcavity;

[0019] Step 3: The pump laser generates a pump laser, and after the polarization state of the pump laser is regulated by the first polarization controller, the regulated pump laser is amplified by the first optical amplifier. The amplified pump laser is then passed through the first circulator and input into the optical microcavity from the forward direction to form a first light beam.

[0020] Step 4: The first light beam generates a Raman gain-dominated Raman optical frequency comb in the optical microcavity;

[0021] Step 5: Adjusting the output power of the control laser or the wavelength of the control laser to control the Q value of the Raman mode in the optical microcavity, thereby regulating the ratio of the power threshold of Raman mode generation to the Kerr Raman power threshold, so that the Raman optical frequency comb is converted into a Kerr soliton optical frequency comb;

[0022] Step 6: auxiliary heating the optical microcavity by adjusting the detuning of the second light beam, thereby regulating the number of Kerr soliton pulses, so that a Kerr soliton optical frequency comb with a desired number of pulses is generated in the optical microcavity;

[0023] Step 7: The Kerr soliton optical frequency comb is split by the first beam splitter to obtain a first split Kerr optical comb and a second split Kerr optical comb, wherein the first split Kerr optical comb enters the optical spectrum analyzer to observe and record the generated Kerr soliton optical frequency comb spectrum;

[0024] Step 8: After the second split Kerr light comb passes through the second beam splitter, a third split Kerr light comb and a fourth split signal are obtained; wherein the third split Kerr light comb is input into a fiber Bragg grating for filtering, and then the filtered light comb beat frequency signal is converted into a radio frequency signal by a high-speed detector, and finally the radio frequency signal is observed and recorded by the spectrum analyzer;

[0025] Step 9: The fourth split beam signal is photoelectrically converted by the photodetector and then input into the oscilloscope to obtain a microcavity transmission spectrum signal.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention provides a method for generating a Kerr soliton frequency comb based on a novel mechanism of adjustable Raman gain. By controlling the change in Raman gain induced by laser light, the Q value and power threshold of the Raman mode are regulated, thereby effectively regulating the power threshold ratio of the Raman-Kerr comb. This solves the problem of real-time control of Kerr-Raman nonlinear interactions in optical microcavities, and produces a high-coherence, low-noise Kerr soliton frequency comb.

[0028] 2. The microcavity and the coupled waveguide are fixedly spaced, without the need for mechanical displacement, changes in microcavity size, or dispersion. This is an all-optical control method with fast control speed, good repeatability, simplicity, and reliability.

[0029] 3. The control laser involved in the present invention can not only be used to regulate the gain and effective loss of the Raman mode, but also can be used as an auxiliary light to stabilize the intracavity power, thereby expanding the detuning range of solitons and facilitating the formation of Kerr soliton optical combs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the experimental setup system for generating a microcavity Kerr soliton optical frequency comb based on tunable Raman gain;

[0031] Figure 2 This is a flow chart of the method for generating a microcavity Kerr soliton optical frequency comb;

[0032] Figure 3 This is a schematic diagram of a method of regulating Raman mode characteristics by controlling laser provided by the present invention;

[0033] Figure 4 It is a schematic diagram of the transmission spectrum waveform collected by the oscilloscope;

[0034] Figure 5 is the spectrum evolution diagram of the generated Kerr soliton optical frequency comb;

[0035] Figure 6 This is a schematic diagram of the spectrum of the Kerr soliton optical frequency comb beat signal collected by the spectrum analyzer. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings:

[0037] In this embodiment, a method and system for generating a microcavity Kerr soliton optical frequency comb based on adjustable Raman gain is provided. By controlling the Raman gain through laser control, the coupling region and intracavity loss of the microcavity mode can be controlled, thereby regulating the effective loss and Q value of the microcavity mode without mechanical displacement. Therefore, the Raman scattering threshold can be controlled by changing the Raman mode gain, and the Kerr-Raman nonlinear interaction can be controlled, providing a new method for generating mode-locked Kerr soliton optical frequency combs.

[0038] See also Figure 1 In this embodiment, a microcavity Kerr soliton optical frequency comb generation system based on adjustable Raman gain includes: a Kerr soliton optical frequency comb generation system based on adjustable Raman gain, including: a pump laser 1, a first polarization controller 2, a first optical amplifier 3, a first circulator 4, a control laser 5, a second polarization controller 6, a second optical amplifier 7, a second circulator 8, an optical microcavity 9, a first beam splitter 10, a spectrum analyzer 11, a second beam splitter 12, a fiber Bragg grating 13, a high-speed detector 14, a spectrum analyzer 15, a photodetector 16, and an oscilloscope 17;

[0039] Among them, the pump laser 1 generates pump laser. The pump laser 1 adopts an external cavity tuned continuous laser with a linewidth of 10 kHz and an output wavelength of 1543.86 nm. The polarization state of the pump laser is controlled by the first polarization controller 2. The first polarization controller 2 adopts a fiber three-ring polarization controller. The first optical amplifier 3 amplifies the power of the regulated pump laser. The first optical amplifier 3 adopts a high-power erbium-doped fiber amplifier with a maximum output power of 5W and an operating band of the C band. The first circulator 4 is used to input the amplified pump laser into the tapered fiber coupler and couple the pump laser into the optical microcavity 9 through the tapered fiber coupler. The circulator 4 has three ports, the first port of which is used to receive pump light, the second port is connected to the tapered fiber coupler, and the third port is used to output the reverse light in the microcavity.

[0040] At the same time, a control laser 5 generates a control laser. The control laser 5 uses an external cavity-tuned continuous laser with a linewidth of 200 kHz and an output wavelength of 1546.46 nm. The polarization state of the control laser is regulated by a second polarization controller 6, which uses a fiber three-ring polarization controller. A second optical amplifier 7 amplifies the power of the regulated control laser to provide a sufficiently strong control light signal for the generation of the Kerr optical frequency comb. The amplified control light is used to regulate the Raman gain and produce an auxiliary heating effect on the microcavity. The second optical amplifier 7 uses a high-power erbium-doped fiber amplifier with a maximum output power of 5 W and an operating band in the C band. A second circulator 8 inputs the amplified control laser into a tapered fiber coupler, which couples the control laser into the optical microcavity 9 through the tapered fiber coupler and outputs a forward Kerr optical frequency comb. The circulator 8 has three ports: a first port for receiving the control light, a second port connected to the tapered fiber coupler, and a third port for outputting the forward light within the microcavity.

[0041] Optical microcavity 9, a nonlinear optical device for generating a Kerr frequency comb, converts a single-frequency pump laser into a Kerr frequency comb through the nonlinear optical effect of cascaded four-wave mixing. Optical microcavity 9 utilizes a SiO2 microrod cavity with a diameter of approximately 1.2 mm, an axial length of approximately 0.4 mm, and a spherical lateral profile. Fabricated by CO2 laser turning, the microrod cavity exhibits anomalous dispersion characteristics. The optical microcavity is coupled using an add-pass coupling structure and a tapered fiber coupler to couple the pump and control lasers into and out of the optical microcavity.

[0042] The first beam splitter 10 splits the Kerr soliton optical frequency comb. The first beam splitter 10 is a tapered optical power splitter with a power splitting ratio of 50:50. The first split Kerr optical comb enters the optical spectrum analyzer 11 for observation and recording of the generated optical comb spectrum. The spectral envelope shape is used as one of the criteria for judging the state of the optical frequency comb. The optical spectrum analyzer 11 adopts an optical spectrum analyzer with a wavelength range of 600-1750 nm, a resolution of 0.03 nm, and a wavelength accuracy of ±20 pm. After the second split Kerr optical comb passes through the second beam splitter 12, the third split Kerr optical comb and the fourth split signal are obtained. The beam splitter 12 is a tapered optical power splitter with a power splitting ratio of 90:10.

[0043] The third split Kerr optical comb is input into the fiber Bragg grating 13 for filtering. The fiber Bragg grating 13 adopts a band-stop fiber Bragg grating filter with a bandwidth of 0.4 nm, which is used to filter out the pump light signal in the Kerr soliton optical frequency comb. The filtered optical comb beat signal is then converted into a radio frequency signal by the high-speed detector 14. The high-speed detector 14 adopts an indium gallium arsenide PIN photodetector with a wavelength range of 1260-1610 nm. Its bandwidth is greater than the frequency of the Kerr optical frequency comb beat signal and is used to output the beat signal in the radio frequency band. Finally, the spectrum analyzer 15 observes and records the radio frequency signal. The spectrum analysis signal serves as the basis for determining the generation of the soliton state optical frequency comb.

[0044] The fourth split beam signal is photoelectrically converted by the photodetector 16, which uses an indium gallium arsenide photodetector with a wavelength range of 800-1700 nm and a bandwidth of 150 MHz; it is then input into the oscilloscope 17 to obtain the microcavity transmission spectrum signal, read the mode parameters such as Q value, and determine the soliton step position.

[0045] join Figure 2 In this embodiment, a microcavity Kerr soliton optical frequency comb generation method is applied to a Kerr soliton optical frequency comb generation system consisting of a pump laser 1, a first polarization controller 2, a first optical amplifier 3, a first circulator 4, a control laser 5, a second polarization controller 6, a second optical amplifier 7, a second circulator 8, an optical microcavity 9, a first beam splitter 10, a spectrum analyzer 11, a second beam splitter 12, a fiber Bragg grating 13, a high-speed detector 14, a spectrum analyzer 15, a photodetector 16, and an oscilloscope 17, and is performed in the following steps:

[0046] Step 1: The control laser 5 generates a control laser with a control wavelength of 1546.46 nm and a power of 685.5 mW. After the polarization state of the control laser is adjusted by the second polarization controller 6, the adjusted control laser is amplified by the second optical amplifier 7. The amplified control laser passes through the second circulator 8 and is reversely input into the optical microcavity 9 to form a second light beam.

[0047] Step 2: Adjust the wavelength of the control laser 5 so that the second light beam excites the forward Raman mode and the Raman frequency comb in the optical microcavity 9;

[0048] Step 3: The pump laser 1 generates a pump laser with a wavelength of 1543.86 nm and a power of 260.5 mW. After the polarization state of the pump laser is regulated by the first polarization controller 2, the regulated pump laser is amplified by the first optical amplifier 3. The amplified pump laser passes through the first circulator 4 and is input into the optical microcavity 9 from the forward direction to form the first light beam.

[0049] Step 4: The first light beam generates a Raman gain-dominated Raman optical frequency comb in the optical microcavity 9;

[0050] Step 5: Adjust the output power of the control laser 5 or the wavelength of the control laser 5 to control the Q value of the Raman mode in the optical microcavity 9, thereby regulating the ratio of the power threshold generated by the Raman mode and the Kerr Raman power threshold, so that the Raman optical frequency comb is converted into a Kerr soliton optical frequency comb.

[0051] Step 6: auxiliary heating of the optical microcavity 9 is performed by adjusting the detuning of the second light beam, thereby regulating the number of Kerr soliton pulses, so that a Kerr soliton optical frequency comb with a desired number of pulses is generated in the optical microcavity 9;

[0052] Step 7: The Kerr soliton optical frequency comb is split by the first beam splitter 10 to obtain a first split Kerr optical comb and a second split Kerr optical comb. The first split Kerr optical comb enters the optical spectrum analyzer 11 to observe and record the generated Kerr soliton optical frequency comb spectrum.

[0053] Step 8: After the second split Kerr comb passes through the second beam splitter 12, a third split Kerr comb and a fourth split signal are obtained. The third split Kerr comb is input into the fiber Bragg grating 13 for filtering, and the high-speed detector 14 converts the filtered comb beat signal into a radio frequency signal. Finally, the spectrum analyzer 15 observes and records the radio frequency signal.

[0054] Step 9: The fourth split beam signal is photoelectrically converted by the photodetector 16 and then input into the oscilloscope 17 to obtain a microcavity transmission spectrum signal.

[0055] Figure 3 is a schematic diagram of regulating Raman mode characteristics by controlling laser provided by the present invention, optionally, wherein, Figure 3 Part (a) is a schematic diagram of Raman mode transmission spectrum control. Figure 3 Part (b) is a diagram showing how the Raman mode Q value and minimum transmittance change with the controlled optical power. The pump wavelength and probe wavelength are 1513.46 nm and 1618.88 nm, respectively. The controlled optical powers are 10.92 mW, 11.76 mW, 12.59 mW, 13.32 mW, 14.29 mW, and 14.96 mW from left to right. The probe optical power is kept below 0.5 mW to minimize thermal effects. Figure 3 It can be seen that with the increase of control light power, the Raman mode linewidth decreases significantly, and the Raman mode Q value increases from 6.83×10 7 Increased to 1.16×10 8 The minimum transmittance gradually decreases from 0.74 to around 0.29, indicating that the system evolves from the undercoupled state to the critical coupled state.

[0056] Another method provided in this embodiment for regulating Raman mode characteristics by controlling light is to optionally regulate the Raman mode Q value by adjusting the detuning of the controlled light, thereby changing the Raman power threshold and regulating the Kerr-Raman nonlinear effect.

[0057] Figure 4 This is a schematic diagram of the transmission spectrum waveform collected by the oscilloscope. Figure 4 It can be seen that the pump Q value is about 2×10 8 .

[0058] Figure 5 The spectral evolution diagram of the generated Kerr soliton optical frequency comb is shown in Figure 2. According to the microcavity Kerr soliton optical frequency comb generation method, the control laser and the pump laser are scanned into the microcavity resonance peak in sequence, and the following is generated first: Figure 5 The Raman optical frequency comb spectrum shown in part (a) of the figure shows that the system is in the Raman-dominated region and almost no Kerr optical comb is generated. As the control laser detuning decreases, the following is observed: Figure 5 Part (b) shows the Kerr-Raman frequency comb spectrum. The Kerr frequency comb is in a modulation instability state. Further reducing the control laser detuning, we can obtain Figure 5 Part (c) of the graph shows the Kerr-Raman frequency comb spectrum. The Kerr frequency comb is in a soliton state. Therefore, by adjusting the control light detuning, the Kerr-Raman comb state transition can be controlled to generate a Kerr soliton frequency comb.

[0059] Figure 6 Figure 1 is a schematic diagram of the spectrum of the Kerr soliton optical frequency comb beat signal collected by the spectrum analyzer. Figure 6 It can be seen that the 3 dB bandwidth of the Kerr optical frequency comb beat signal is about 10 Hz, indicating that the Kerr optical frequency comb is a mode-locked soliton state.

[0060] The microcavity Kerr soliton optical frequency comb generation method based on adjustable Raman gain mentioned in this embodiment is not limited to the microrod cavity system, and can be applied to all similar optical microcavity Kerr optical frequency comb systems.

[0061] In summary, the present invention proposes a method and system for generating a microcavity Kerr soliton frequency comb based on adjustable Raman gain. This method effectively controls the Raman-Kerr threshold ratio, thereby generating a Kerr soliton frequency comb. This all-optical control method eliminates the need for size or coupling spacing control, facilitating miniaturization and integration. This method is achieved by controlling the Raman mode Q value and power threshold using a control laser, thereby controlling the Kerr-Raman nonlinear interaction, and utilizing the auxiliary heating effect of the control laser to generate a broadband, low-noise Kerr soliton frequency comb.

[0062] Some aspects not described in detail in this invention are well known to those skilled in the art. The specific embodiments described above are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A Kerr soliton optical frequency comb generation system based on adjustable Raman gain, characterized in that: include: A pump laser (1), a first polarization controller (2), a first optical amplifier (3), a first circulator (4), a control laser (5), a second polarization controller (6), a second optical amplifier (7), a second circulator (8), an optical microcavity (9), a first beam splitter (10), a spectrum analyzer (11), a second beam splitter (12), a fiber Bragg grating (13), a high-speed detector (14), a spectrum analyzer (15), a photodetector (16), and an oscilloscope (17); The pump laser (1) generates a pump laser, and the polarization state of the pump laser is regulated by a first polarization controller (2); the first optical amplifier (3) amplifies the power of the regulated pump laser; and the first circulator (4) inputs the amplified pump laser into an optical microcavity (9) to generate a Kerr optical frequency comb. At the same time, the control laser (5) generates a control laser, and the polarization state of the control laser is regulated by the second polarization controller (6), the second optical amplifier (7) performs power amplification on the regulated control laser, and the second circulator (8) inputs the amplified control laser into the optical microcavity (9) to regulate the Raman gain of the microcavity mode, thereby regulating the Kerr optical frequency comb to a soliton state, and the second circulator (8) outputs the Kerr soliton optical frequency comb; The first beam splitter (10) splits the Kerr soliton optical frequency comb, wherein the first split Kerr optical comb enters the optical spectrum analyzer (11) for observation and recording of the generated optical comb spectrum, and the second split Kerr optical comb passes through the second beam splitter (12) to obtain a third split Kerr optical comb and a fourth split signal; The third split Kerr optical comb is input into a fiber Bragg grating (13) for filtering, and then the filtered optical comb beat frequency signal is converted into a radio frequency signal by a high-speed detector (14), and finally the radio frequency signal is observed and recorded by the spectrum analyzer (15); The fourth split beam signal is photoelectrically converted by the photodetector (16) and then input into the oscilloscope (17) to obtain a microcavity transmission spectrum signal.

2. The Kerr soliton optical frequency comb generation system based on adjustable Raman gain according to claim 1, characterized in that: The pump laser (1) and the control laser (5) are external cavity tuned continuous lasers, whose wavelength and output power can be tuned, and are used to inject continuous single-frequency optical signals into the optical microcavity (9) as pump light and control light.

3. The Kerr soliton optical frequency comb generation system based on adjustable Raman gain according to claim 1, characterized in that: The fiber Bragg grating (13) has a band-stop characteristic and is used to filter out the pump light signal in the Kerr soliton optical frequency comb.

4. The Kerr soliton optical frequency comb generation system based on adjustable Raman gain according to claim 1, characterized in that: The high-speed photodetector (14) operates in the microwave band, has a bandwidth greater than the frequency of the Kerr optical frequency comb beat signal, and is used to output the beat signal in the radio frequency band. The output end of the high-speed photodetector (14) is connected to the spectrum analyzer (15).

5. A method for generating a microcavity Kerr soliton optical frequency comb, characterized in that: The invention is applied to a Kerr soliton optical frequency comb generation system composed of a pump laser (1), a first polarization controller (2), a first optical amplifier (3), a first circulator (4), a control laser (5), a second polarization controller (6), a second optical amplifier (7), a second circulator (8), an optical microcavity (9), a first beam splitter (10), a spectrum analyzer (11), a second beam splitter (12), a fiber Bragg grating (13), a high-speed detector (14), a spectrum analyzer (15), a photodetector (16) and an oscilloscope (17), and is performed according to the following steps: Step 1: The control laser (5) generates a control laser, and after the polarization state of the control laser is regulated by the second polarization controller (6), the regulated control laser is power amplified by the second optical amplifier (7), and the amplified control laser is passed through the second circulator (8) and then inputted into the optical microcavity (9) in reverse to form a second light beam; Step 2: adjusting the wavelength of the control laser (5) so that the second light beam excites a forward Raman mode spectrum in the optical microcavity (9); Step 3: The pump laser (1) generates a pump laser, and after the polarization state thereof is regulated by the first polarization controller (2), the regulated pump laser is power amplified by the first optical amplifier (3). The amplified pump laser is then passed through the first circulator (4) and input into the optical microcavity (9) in a forward direction to form a first light beam; Step 4: the first light beam generates a Raman gain-dominated Raman optical frequency comb in the optical microcavity (9); Step 5: adjusting the output power of the control laser (5) or the wavelength of the control laser (5) to control the Q value of the Raman mode in the optical microcavity (9), thereby regulating the ratio of the power threshold generated by the Raman mode to the Kerr Raman power threshold, so that the Raman optical frequency comb is converted into a Kerr soliton optical frequency comb; Step 6: auxiliary heating of the optical microcavity (9) is performed by adjusting the detuning of the second light beam, thereby regulating the number of Kerr soliton pulses, so that a Kerr soliton optical frequency comb with a required number of pulses is generated in the optical microcavity (9); Step 7, the Kerr soliton optical frequency comb is split by the first beam splitter (10) to obtain a first split Kerr optical comb and a second split Kerr optical comb, wherein the first split Kerr optical comb enters the optical spectrum analyzer (11) to observe and record the generated Kerr soliton optical frequency comb spectrum; Step 8: After the second split Kerr light comb passes through the second beam splitter (12), a third split Kerr light comb and a fourth split signal are obtained; wherein the third split Kerr light comb is input into a fiber Bragg grating (13) for filtering, and then the filtered light comb beat frequency signal is converted into a radio frequency signal by a high-speed detector (14), and finally the radio frequency signal is observed and recorded by the spectrum analyzer (15); Step 9: The fourth split beam signal is subjected to photoelectric conversion by the photodetector (16) and then input into the oscilloscope (17) to obtain a microcavity transmission spectrum signal.

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