Dual-cavity self-injection integrated photogenerated microwave source system based on microcavity structure

Abstract

The present invention relates to the field of photogenerated microwave technology, and in particular to a dual-cavity self-injection integrated photogenerated microwave source system based on a microcavity structure. The system is an integrated chip structure and includes three chip-level integrated units: a first integrated unit, which is an active device, including a DFB laser and a high-saturation power photodetector; a second integrated unit, which is a passive device, including a lithium niobate thin film modulator based on a silicon substrate, a lithium niobate ring whispering gallery microresonator, and a CaF2 whispering gallery resonator; and a third integrated unit, which is an integrated circuit chip for compensating for losses in a photoelectric oscillation circuit and performing phase matching, including a phase shifter and an electrical amplifier. The system of the present invention can overcome the problem of poor signal stability of self-injection-locked photogenerated microwave sources in the prior art, and provides a miniaturized microwave source with low phase noise, tunability, and high frequency stability for hypersonic precision strike weapons and equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of photogenerated microwave technology, and in particular to a dual-cavity self-injection integrated photogenerated microwave source system based on a microcavity structure. Background Art

[0002] Microwave photon signal generation technology utilizes the interaction between microwaves and light waves, relying on the high frequency, broadband, low loss, and anti-interference characteristics of light waves. It combines the advantages of broadband photonic technology and fine control of electronic technology, and uses optoelectronic conversion devices to achieve light wave and microwave fusion processing. It can effectively solve the problem of the incompatibility between high frequency bands and high signal quality faced by traditional microwave signal generation technology.

[0003] Currently, the main signal generation methods based on microwave photonic technology include optical beat frequency, nonlinear modulation frequency doubling, optical domain frequency division, and optoelectronic oscillation. Optoelectronic oscillation utilizes self-generated radio frequency oscillations to selectively initiate noise in a ring cavity and is one of the most representative optoelectronic fusion technologies. It uses an optical signal emitted by a laser to be transmitted to an optoelectronic modulator for modulation. The modulated signal is then transmitted to a photodetector for demodulation via a delay device (single-mode fiber or micro-ring cavity). The output electrical signal then passes through an electrical amplifier for loss compensation and a bandpass filter for mode selection before being transmitted back to the RF port of the optoelectronic modulator, completing a closed optoelectronic feedback loop. Oscillation occurs when the loop gain exceeds the loss threshold and meets the initiation threshold. OEOs, with their oscillator cavity composed of ultra-low-loss delay loops, exhibit unique advantages in ultra-high Q, ultra-low phase noise, ultra-wide frequency tuning range, and immunity to electromagnetic interference. They can generate high-spectral-purity microwave signals from several hundred MHz to over 100 GHz. By utilizing long, low-loss optical fibers as energy storage elements, they achieve phase noise as low as -163 dBc / Hz at 10 kHz, theoretically independent of the operating frequency. Traditional OEO structures utilize optical fibers as a delay and energy storage medium to reduce the phase noise of OEOs. However, optical fiber transmission delays vary over time and due to external environmental factors such as temperature and vibration, causing frequency drift in the output microwaves. This also limits the size, weight, and power consumption of the application platform. However, with the rapid development of the information age and the increasing demand for miniaturized, low-power, and lightweight microwave sources in aerospace applications, the size and weight of these microwave sources are particularly important for missile-borne microwave signal sources, where their operational effectiveness is directly affected. Consequently, significant efforts are currently underway to reduce the size of OEOs.

[0004] Chinese Patent Publication No. CN202111340205.0 discloses a tunable integrated photogenerated microwave source chip and system based on lithium niobate thin film. The chip comprises a substrate wafer, a lower cladding, a lithium niobate thin film, and an upper cladding, stacked from bottom to top. A lithium niobate optical waveguide is disposed on the lithium niobate thin film. The lithium niobate optical waveguide comprises a pattern conversion waveguide, a first straight waveguide, a first curved waveguide, a second straight waveguide, a second curved waveguide, a third straight waveguide, and an optical microcavity waveguide, which are connected in sequence. A first metal electrode is disposed on the upper cladding at a position corresponding to the first straight waveguide. The first metal electrode, the pattern conversion waveguide, and the first straight waveguide together form a phase modulator. A second metal electrode is disposed on the upper cladding at a position corresponding to the optical microcavity waveguide. The second metal electrode, the third straight waveguide, and the optical microcavity waveguide together form a high-Q microresonator. A detector is also disposed on the lithium niobate thin film and connected to the output of the high-Q microresonator. This technology allows for miniaturization of the photogenerated microwave source, but it also suffers from poor signal stability. Summary of the Invention

[0005] To this end, the present invention provides a dual-cavity self-injection integrated integrated photogenerated microwave source system based on a microcavity structure to overcome the problem of poor signal stability of the self-injection locked photogenerated microwave source in the prior art and proposes a miniaturized microwave source with low phase noise, tunability, and high frequency stability for hypersonic precision strike weapons and equipment.

[0006] To achieve the above objectives, the present invention provides a dual-cavity self-injection integrated photogenerated microwave source system based on a microcavity structure, which is an integrated chip structure and includes three chip-level integrated units:

[0007] The first integrated unit is an active device, including a DFB laser used as a system light source and a high saturation power photodetector used to perform system photoelectric conversion;

[0008] A second integrated unit, which is a passive device connected to the first integrated unit to suppress system phase noise, includes a lithium niobate thin film modulator based on a silicon substrate, a lithium niobate ring whispering gallery microresonator, and a CaF2 whispering gallery resonator;

[0009] a third integrated unit connected to the first integrated unit and the second integrated unit, the third integrated unit being an integrated circuit chip for compensating for losses in the optoelectronic oscillation circuit and performing phase matching, including a phase shifter and an electrical amplifier;

[0010] In the system, the optical signal emitted by the DFB laser is transmitted to the lithium niobate thin film modulator for modulation after being coupled with a mode spot. The modulated optical signal is transmitted to the lithium niobate ring-shaped whispering gallery microresonator after being coupled with a straight-through waveguide. The lithium niobate ring-shaped whispering gallery microresonator filters and stores energy on the coupled optical signal, and then transmits it to the photodetector through waveguide grating diffraction for beat frequency, so as to output the converted electrical signal to the third integrated unit through photoelectric conversion. The electrical signal is phase-shifted in turn by the phase shifter, and after the loop loss is compensated by the electrical amplifier, the electrical signal that meets the oscillation threshold is transmitted to the RF input port of the lithium niobate thin film modulator to complete the loop closure.

[0011] Furthermore, the first integrated unit and the second integrated unit couple the DFB laser and the high saturation power photodetector to the light field of the thin film lithium niobate chip on the silicon substrate respectively through waveguide edge coupling and grating vertical coupling.

[0012] Furthermore, the system forms a microwave photon filter through the DFB laser, the lithium niobate ring whispering gallery microresonator and a phase modulator to perform frequency tuning. During frequency tuning, the microwave photon filter expands the tuning range of the microwave signal by adjusting the wavelength of the optical signal emitted by the DFB laser. The microwave photon filter controls the mode spacing of the lithium niobate ring whispering gallery microcavity through bias voltage to adjust the microwave signal frequency to a target value.

[0013] Furthermore, the CaF2 whispering gallery resonator uses a self-injection effect to suppress phase noise.

[0014] Furthermore, the system adopts an integrated structure of lithium niobate film and whispering gallery microcavity.

[0015] Furthermore, the oscillation threshold refers to a gain value being greater than a loss value.

[0016] Furthermore, the DFB laser adopts an InP substrate.

[0017] The filtering principle of the present invention based on the dual-cavity self-injection integrated photogenerated microwave source is:

[0018] The present invention proposes a dual-cavity microwave resonant loop based on ultra-high Q loop self-injection. Its frequency tuning method is as follows: ultra-low spurious signal mode selection and phase noise optimization are achieved by utilizing the ultra-high Q value and mode spacing (FSR2) of the microcavity. Here, FSR1 represents the mode spacing of the CaF2 microresonant cavity, fsr1 represents the mode spacing of the injection resonant loop formed by the CaF2 microresonant cavity, FSR2 represents the mode spacing of the lithium niobate thin film microresonant cavity, and fsr2 represents the mode spacing of the resonant loop formed by the lithium niobate thin film microresonant cavity. In the master oscillator loop formed by the lithium niobate resonant cavity, the frequency difference (Nfsr2) between the wavelength of the laser mode matched in the loop and the resonant mode of the microcavity is the final RF output wavelength RF, where N is an integer. Frequency tuning is achieved by tuning the wavelength of the laser, and mode matching and microwave frequency tuning are achieved by adding electrode feedback to the lithium niobate microcavity. The combination of the above two methods can achieve fine control of the final generated microwave signal.

[0019] Furthermore, the present invention proposes an injection-locked loop based on the above-mentioned dual-cavity microwave resonant loop based on ultra-high Q value loop self-injection. In the loop, the FSR2 of a single loop composed of a lithium niobate thin film microresonant cavity is measured to calculate the equivalent delay of the lithium niobate microcavity, and the equivalent delays of other loops are calculated. The Q value required by the injection loop CaF2 microresonant cavity is calculated based on the calculated equivalent delay of the lithium niobate microcavity and the equivalent delays of other loops. A tunable delay line is used to complete mode matching of the two resonant loops and filter out optical sidebands entering the injection-locked loop that disrupt the loop balance to complete signal filtering of the same frequency, thereby achieving injection locking.

[0020] Furthermore, the frequency tuning of the photogenerated microwave source is achieved through a microwave photon filter composed of a laser, a phase modulator and a lithium niobate whispering gallery microresonator. By adjusting the wavelength of the laser, a large range of microwave signals can be tuned, and by biasing the mode spacing of the lithium niobate film whispering gallery microcavity, fine control of the microwave signal frequency can be achieved.

[0021] Phase noise mainly depends on the equivalent Q value of the loop. By introducing a high-Q CaF2 phase noise suppression loop and using the self-injection effect, the limited Q factor of the lithium niobate whispering gallery microcavity is compensated, achieving ultra-low phase noise signal output.

[0022] Long-term stability mainly depends on the laser frequency stability and the loop frequency instability caused by loop temperature and jitter. The loop delay jitter is compensated by using a phase-locked loop. The laser frequency is stabilized by locking the laser injection into a high-Q factor CaF2 micro-resonator, ultimately outputting an ultra-high stability signal.

[0023] The weight of a photogenerated microwave source is mainly limited by the energy storage delay device in the loop. This project utilizes the integrated technology of lithium niobate thin film and whispering gallery microcavity to greatly reduce the weight of the integrated device.

[0024] The signal linewidth mainly depends on the bandwidth of the filter in the loop. The injection loop composed of high-Q lithium niobate whispering gallery microcavity and ultra-high Q CaF2 used in the project as a filter meets the project's requirements for signal linewidth and side mode suppression ratio.

[0025] Compared with the existing technology, the beneficial effect of the present invention lies in that, in response to the demand of hypersonic precision strike weapons and equipment for low phase noise, tunable, high frequency stability miniaturized microwave sources, the present invention carries out research on the integrated technology of dual-cavity self-injection low phase noise photogenerated microwave source based on microcavity structure, and proposes an integrated low phase noise tunable photogenerated microwave source by breaking through the self-injection locked photogenerated microwave source signal stability improvement technology, the design and preparation of high-Q value broadband tunable lithium niobate resonator, the phase modulator technology based on lithium niobate thin film waveguide, the detector chip structure design and impedance system design and optoelectronic microsystem heterogeneous three-dimensional integration technology, which effectively improves the stability of the self-injection locked photogenerated microwave source signal.

[0026] Furthermore, the frequency tuning of the photogenerated microwave source of the system described in the present invention is achieved through a microwave photon filter composed of a laser, a phase modulator and a lithium niobate whispering gallery microresonator. By adjusting the wavelength of the laser, tuning of a large range of microwave signals can be achieved. By controlling the mode spacing of the lithium niobate thin film whispering gallery microcavity through bias voltage, fine regulation of the microwave signal frequency is effectively achieved, ensuring that the system described in the present invention can achieve a higher frequency tuning target value.

[0027] Furthermore, the system described in the present invention introduces a high-Q CaF2 phase noise suppression loop and uses the self-injection effect to calculate the Q value required by the CaF2 microresonator in the injection loop, thereby avoiding the problem of limited Q factor of the lithium niobate whispering gallery microcavity. By calculating and injecting an equivalent Q value into the loop through self-injection technology, the output of an ultra-low phase noise signal is effectively achieved.

[0028] Furthermore, the system of the present invention achieves loop delay jitter compensation by adopting a phase-locked loop, and achieves laser frequency stabilization by locking the laser injection into a high-Q factor CaF2 microresonator, further ensuring that the output signal has ultra-high stability.

[0029] Furthermore, the system of the present invention utilizes the integrated lithium niobate film and whispering gallery microcavity integration technology to greatly reduce the weight of the integrated device. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1This is a schematic structural diagram of a dual-cavity self-injection integrated photogenerated microwave source system based on a microcavity structure according to the present invention;

[0031] Figure 2 This is a diagram showing the filtering principle of the dual-cavity self-injection integrated photogenerated microwave source system based on a microcavity structure of the present invention. DETAILED DESCRIPTION

[0032] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention.

[0033] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0034] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside", and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0035] Furthermore, it should be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0036] See also Figure 1 As shown, it is a structural schematic diagram of a dual-cavity self-injection integrated photogenerated microwave source system based on a microcavity structure of the present invention. The present invention provides a dual-cavity self-injection integrated photogenerated microwave source system based on a microcavity structure, which is an integrated chip structure, including three chip-level integrated units:

[0037] The first integrated unit is an active device, including a DFB laser used as a system light source and a high saturation power photodetector used to perform system photoelectric conversion;

[0038] A second integrated unit, which is a passive device connected to the first integrated unit to suppress system phase noise, includes a lithium niobate thin film modulator based on a silicon substrate, a lithium niobate ring whispering gallery microresonator, and a CaF2 whispering gallery resonator;

[0039] a third integrated unit connected to the first integrated unit and the second integrated unit, the third integrated unit being an integrated circuit chip for compensating for losses in the optoelectronic oscillation circuit and performing phase matching, including a phase shifter and an electrical amplifier;

[0040] In the system, the optical signal emitted by the DFB laser is transmitted to the lithium niobate thin film modulator for modulation after being coupled with a mode spot. The modulated optical signal is transmitted to the lithium niobate ring-shaped whispering gallery microresonator after being coupled with a straight-through waveguide. The lithium niobate ring-shaped whispering gallery microresonator filters and stores energy on the coupled optical signal, and then transmits it to the photodetector through waveguide grating diffraction for beat frequency, so as to output the converted electrical signal to the third integrated unit through photoelectric conversion. The electrical signal is phase-shifted in turn by the phase shifter, and after the loop loss is compensated by the electrical amplifier, the electrical signal that meets the oscillation threshold is transmitted to the RF input port of the lithium niobate thin film modulator to complete the loop closure.

[0041] Please continue reading Figure 1 As shown, the first integrated unit and the second integrated unit couple the DFB laser and the high saturation power photodetector to the thin film lithium niobate chip light field on the silicon substrate through waveguide edge coupling and grating vertical coupling respectively.

[0042] Specifically, the system forms a microwave photon filter through the DFB laser, the lithium niobate ring whispering gallery microresonator and a phase modulator for frequency tuning. During frequency tuning, the microwave photon filter expands the tuning range of the microwave signal by adjusting the wavelength of the optical signal emitted by the DFB laser. The microwave photon filter controls the mode spacing of the lithium niobate ring whispering gallery microcavity through bias voltage to adjust the microwave signal frequency to the target value.

[0043] Specifically, the CaF2 whispering gallery resonator uses a self-injection effect to suppress phase noise.

[0044] Specifically, the system adopts an integrated structure of lithium niobate film and whispering gallery microcavity.

[0045] Specifically, the oscillation threshold refers to a gain value being greater than a loss value.

[0046] Specifically, the DFB laser adopts an InP substrate.

[0047] Specifically, the system described in the present invention is based on an integrated photogenerated microwave source architecture of a laser and a dual-microcavity structure: based on the analysis of the notch microwave photon filtering mechanism composed of microcavities and the integrated OEO phase noise reduction technology, a phase noise optimization technology based on dual-cavity self-injection and a phase stabilization circuit based on a frequency division phase detection feedback loop are constructed to achieve an integrated photogenerated microwave source with ultra-low phase noise and ultra-high stability.

[0048] Specifically, the system described in the present invention is based on the research on the broadband signal generation mechanism of lasers and microcavity notch filters. It controls the mode of the microcavity by bias voltage and controls the relationship between bias voltage and ring cavity delay to realize Fourier mode-locked broadband signal generation microwave source and provide its phase noise and stability improvement solution.

[0049] Specifically, the system described in the present invention is based on the filtering theory research of an integrated optically generated microwave source of a laser and a dual-microcavity structure. By controlling the modes of the two ring cavities and matching the modes of the two microcavities, the laser is mode-locked to one of the microcavities with an ultra-high Q value to achieve highly stable and tunable signal generation.

[0050] See also Figure 2 As shown, it is a diagram of the filtering principle of the dual-cavity self-injection integrated integrated photogenerated microwave source system based on the microcavity structure of the present invention. The filtering principle of the dual-cavity self-injection integrated integrated photogenerated microwave source based on the present invention is:

[0051] The present invention proposes a dual-cavity microwave resonant loop based on ultra-high Q loop self-injection. Its frequency tuning method is as follows: ultra-low spurious signal mode selection and phase noise optimization are achieved by utilizing the ultra-high Q value and mode spacing (FSR2) of the microcavity. Here, FSR1 represents the mode spacing of the CaF2 microresonant cavity, fsr1 represents the mode spacing of the injection resonant loop formed by the CaF2 microresonant cavity, FSR2 represents the mode spacing of the lithium niobate thin film microresonant cavity, and fsr2 represents the mode spacing of the resonant loop formed by the lithium niobate thin film microresonant cavity. In the master oscillator loop formed by the lithium niobate resonant cavity, the frequency difference (Nfsr2) between the wavelength of the laser mode matched in the loop and the resonant mode of the microcavity is the final RF output wavelength RF, where N is an integer. Frequency tuning is achieved by tuning the wavelength of the laser, and mode matching and microwave frequency tuning are achieved by adding electrode feedback to the lithium niobate microcavity. The combination of the above two methods can achieve fine control of the final generated microwave signal.

[0052] Please continue reading Figure 2As shown, the present invention proposes an injection-locked loop based on the above-mentioned dual-cavity microwave resonant loop based on ultra-high Q value loop self-injection. In the loop, the FSR2 of a single loop composed of a lithium niobate thin film microresonant cavity is measured to calculate the equivalent delay of the lithium niobate microcavity, and the equivalent delays of other loops are calculated. The Q value required by the injection loop CaF2 microresonant cavity is calculated based on the calculated equivalent delay of the lithium niobate microcavity and the equivalent delays of other loops. A tunable delay line is used to achieve mode matching of the two resonant loops and filter out optical sidebands entering the injection-locked loop that disrupt the loop balance to complete signal filtering of the same frequency, thereby achieving injection locking.

[0053] Specifically, the frequency tuning of the photogenerated microwave source is achieved through a microwave photon filter composed of a laser, a phase modulator and a lithium niobate whispering gallery microresonator. By adjusting the wavelength of the laser, a wide range of microwave signals can be tuned, and by biasing the mode spacing of the lithium niobate film whispering gallery microcavity, fine control of the microwave signal frequency can be achieved.

[0054] Specifically, phase noise depends primarily on the equivalent Q value of the loop. The system of the present invention introduces a high-Q CaF2 phase noise suppression loop and utilizes the self-injection effect to compensate for the limited Q factor of the lithium niobate whispering gallery microcavity, achieving ultra-low phase noise signal output.

[0055] Specifically, long-term stability depends primarily on the laser frequency stability and loop frequency instability caused by loop temperature and jitter. The system of the present invention uses a phase-locked loop to compensate for loop delay jitter, and achieves laser frequency stabilization by laser injection locking to a high-Q factor CaF2 microresonator, ultimately outputting an ultra-high stability signal.

[0056] Specifically, the weight of the photogenerated microwave source is mainly limited by the energy storage delay device in the loop. The system described in the present invention utilizes the integrated lithium niobate film and whispering gallery microcavity integration technology to greatly reduce the weight of the integrated device.

[0057] Specifically, the signal linewidth mainly depends on the bandwidth of the filter in the loop. The injection loop composed of the high-Q lithium niobate whispering gallery microcavity and ultra-high-Q CaF2 used in the system of the present invention as a filter meets the project's requirements for signal linewidth and side mode suppression ratio.

[0058] Thus far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

[0059] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A dual-cavity self-injection integrated photogenerated microwave source system based on a microcavity structure, characterized in that: It is an integrated chip structure, including three chip-level integrated units: The first integrated unit is an active device, including a DFB laser used as a system light source and a high saturation power photodetector used to perform system photoelectric conversion; A second integrated unit, which is a passive device connected to the first integrated unit to suppress system phase noise, includes a lithium niobate thin film modulator based on a silicon substrate, a lithium niobate ring whispering gallery microresonator, and a CaF2 whispering gallery resonator; a third integrated unit connected to the first integrated unit and the second integrated unit, the third integrated unit being an integrated circuit chip for compensating for losses in the optoelectronic oscillation circuit and performing phase matching, including a phase shifter and an electrical amplifier; In the system, the optical signal emitted by the DFB laser is transmitted to the lithium niobate thin film modulator for modulation after being coupled with a mode spot. The modulated optical signal is transmitted to the lithium niobate ring-shaped whispering gallery microresonator after being coupled with a straight-through waveguide. The lithium niobate ring-shaped whispering gallery microresonator filters and stores energy on the coupled optical signal, and then transmits it to the photodetector through waveguide grating diffraction for beat frequency, so as to output the converted electrical signal to the third integrated unit through photoelectric conversion. The electrical signal is phase-shifted in turn by the phase shifter, and after the loop loss is compensated by the electrical amplifier, the electrical signal that meets the oscillation threshold is transmitted to the radio frequency input port of the lithium niobate thin film modulator to complete the loop closure. The first integrated unit and the second integrated unit couple the DFB laser and the high saturation power photodetector to the light field of the thin film lithium niobate chip on the silicon substrate respectively through waveguide edge coupling and grating vertical coupling; The system uses the DFB laser, the lithium niobate ring whispering gallery microresonator and a phase modulator to form a microwave photon filter for frequency tuning. During frequency tuning, the microwave photon filter expands the tuning range of the microwave signal by adjusting the wavelength of the optical signal emitted by the DFB laser. The microwave photon filter controls the mode spacing of the lithium niobate ring whispering gallery microcavity through bias voltage to adjust the microwave signal frequency to a target value.

2. The dual-cavity self-injection integrated photogenerated microwave source system based on a microcavity structure according to claim 1 is characterized in that: The CaF2 whispering gallery resonator uses a self-injection effect to suppress phase noise.

3. The dual-cavity self-injection integrated photogenerated microwave source system based on a microcavity structure according to claim 1 is characterized in that: The system adopts an integrated structure of lithium niobate film and whispering gallery microcavity.

4. The dual-cavity self-injection integrated photogenerated microwave source system based on a microcavity structure according to claim 1 is characterized in that: The oscillation threshold refers to a gain value greater than a loss value.

5. The dual-cavity self-injection integrated photogenerated microwave source system based on a microcavity structure according to claim 1 is characterized in that: The DFB laser adopts an InP substrate.

6. The dual-cavity self-injection integrated photogenerated microwave source system based on a microcavity structure according to any one of claims 1 to 5, characterized in that: The system adopts a dual-cavity microwave resonant loop based on ultra-high Q value loop self-injection, and its frequency tuning method is: With the help of the ultra-high Q value and mode spacing FSR2 of the microcavity, through the mode control of the two ring cavities and the matching control of the two microcavity modes, the laser is mode-locked to one of the ultra-high Q value microcavities, achieving ultra-low spurious signal mode selection and phase noise optimization. Wherein, FSR1 represents the mode spacing of the CaF2 microresonator, fsr1 represents the mode spacing of the injection resonant loop formed by the CaF2 microresonator, FSR2 represents the mode spacing of the lithium niobate thin film microresonator, and fsr2 represents the mode spacing of the resonant loop formed by the lithium niobate thin film microresonator; In the master oscillator loop formed by the lithium niobate resonant cavity, the frequency difference Nfsr2 between the wavelength of the laser mode matched in the loop and the resonant mode of the microcavity is the wavelength RF of the final RF output, where N is an integer. Frequency tuning is achieved by tuning the wavelength of the laser, and electrode feedback is added to the lithium niobate microcavity to achieve mode matching and microwave frequency tuning. The combination of these two tuning methods enables fine control of the generated microwave signal.

7. The dual-cavity self-injection integrated photogenerated microwave source system based on a microcavity structure according to claim 6 is characterized in that: The system uses an injection-locked loop. In the loop, the FSR2 of a single loop formed by a lithium niobate thin film microresonator is measured to calculate the equivalent delay of the lithium niobate microresonator and the equivalent delays of other parts of the loop. The required Q value of the injection loop CaF2 microresonator is calculated based on the calculated equivalent delay of the lithium niobate microresonator and the equivalent delays of other parts of the loop. A tunable delay line is used to achieve mode matching between the two resonant loops and filter out optical sidebands that enter the injection-locked loop and disrupt the loop balance to complete signal filtering of the same frequency, thereby achieving injection locking.

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