Mid-infrared microcavity optical frequency comb generation system and method based on self-injection locking

Abstract

The application discloses a kind of mid-infrared microcavity optical frequency comb generation system and method based on self-injection locking, solve the problem of complex system architecture, integrated difficulty, mode-locking start difficult in existing microcavity optical frequency comb generation scheme.Specifically including pump light source unit, micro-ring resonator, optical splitter, feedback regulation unit and spectrum analysis unit.The application inherits the inherent advantages of self-injection locking scheme, system structure is simple, convenient to operate, can realize the stable output of one-key start type optical frequency comb;The performance requirement of pump laser is low, the compression of laser linewidth and the suppression of noise are realized by feedback injection mechanism, without using high-performance narrow-linewidth swept laser, so as to reduce system cost and implementation difficulty.

Description

Technical Field

[0001] This invention relates to a mid-infrared microcavity optical frequency comb generation system and method, specifically to a mid-infrared microcavity optical frequency comb generation system and method based on self-injection locking. Background Technology

[0002] The mid-infrared band is the core atmospheric transmission window, where the characteristic absorption peaks of the vast majority of molecules are distributed. Compared to the near-infrared band, the spectral absorption intensity in the mid-infrared band can be 1 to 2 orders of magnitude higher, resulting in a significant advantage in detection sensitivity. This makes it irreplaceable in many fields such as national defense, medicine, and communications.

[0003] The industrialization and practical application of mid-infrared light waves highly depend on high-performance light sources, especially those with broadband and multi-wavelength coherent characteristics. Optical frequency combs (FFCs) exhibit periodic mode-locked light pulses in the time domain and consist of a series of equally spaced, highly coherent spectral lines in the frequency domain. They have already shown excellent application potential in fields such as coherent communication and precision measurement.

[0004] Currently, traditional mid-infrared optical frequency combs are mainly fabricated using fluoride optical fibers, specially doped semiconductors, and other devices combined with mode-locking technology. This results in drawbacks such as complex system structure, large size, heavy weight, and high cost, significantly hindering their engineering implementation and practical application. Furthermore, limitations imposed by waveguide dispersion tuning difficulties and physical cavity length constraints prevent traditional solutions from simultaneously achieving both high bandwidth and high repetition rate characteristics, thus limiting performance improvements.

[0005] With the iterative upgrades of semiconductor process technology, optical microcavities, possessing high quality factor and low mode volume characteristics, have become a research hotspot due to their inherent advantages such as small size, low power consumption, flexible and controllable dispersion, and ease of integration. Compared to traditional mode-locked laser optical frequency combs, microcavity optical frequency combs offer outstanding advantages in terms of small size, low power consumption, and wide spectrum, demonstrating unique technological advantages and application prospects in fields such as coherent optical communication, optical clocks, and ultrafast high-precision ranging.

[0006] However, in the actual generation process of mid-infrared microcavity optical frequency combs, the coupling effects of thermal and Kerr nonlinear effects cause frequency shifts in the microcavity resonant peaks, accompanied by drastic fluctuations in intracavity optical power, making stable mode-locking difficult to achieve. Furthermore, while C-band optical frequency combs have abundant and mature tuning methods, the mid-infrared band is limited by the performance shortcomings of the supporting lasers and optoelectronic devices, resulting in very limited available tuning methods. This has become a core technical challenge restricting the stable generation of mid-infrared microcavity optical frequency combs.

[0007] Self-injection locking technology can precisely lock the laser frequency to the microcavity resonant frequency by adjusting the gain and loss distribution within the laser resonant cavity through microcavity feedback light. This eliminates the need for complex tuning structures and feedback loops, avoiding dependence on laser tuning performance and mid-infrared optoelectronic device performance, and providing a feasible technical path for achieving stable mode-locking of mid-infrared microcavity optical frequency combs.

[0008] However, in the critical 2μm mid-infrared band, self-injection-locked optical frequency comb technology faces a severe power-threshold mismatch problem. Currently, the single-mode output power of commercially available traditional InP-based optoelectronic devices has long been stable at around 10mW, far below the pump threshold power required for stable generation by a 2μm-band microcavity optical frequency comb, resulting in a significant power gap. Therefore, to overcome the current technological bottleneck and achieve stable output of the 2μm-band mid-infrared microcavity optical frequency comb, it is urgent to develop a novel implementation scheme that breaks through the traditional self-injection-locked technology paradigm. Summary of the Invention

[0009] To address the technical challenges of complex system architecture, difficult integration, and difficult mode-locking startup in existing microcavity optical frequency comb generation schemes, this invention provides a mid-infrared microcavity optical frequency comb generation system and method based on self-injection locking.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A mid-infrared microcavity optical frequency comb generation system based on self-injection locking is characterized by:

[0012] The system includes a pump source unit, a micro-ring resonator, an optical splitter, a feedback adjustment unit, and a spectral analysis unit. The pump source unit emits mid-infrared pump laser light. The input of the micro-ring resonator is connected to the output of the pump source unit, and its output is connected to the input of the optical splitter. The first output of the optical splitter is connected to the feedback adjustment unit, and its second output is connected to the spectral analysis unit or an external analysis and measurement device, used to split the output light of the micro-ring resonator into feedback light and application light. The output of the feedback adjustment unit is connected to the input of the pump source unit, used to adjust the feedback light and send it to the pump source unit. The micro-ring resonator generates an optical frequency comb under the action of the pump source unit and the feedback adjustment unit. The spectral analysis unit analyzes the spectral information of the application light.

[0013] Furthermore, the pump source unit includes a distributed feedback laser, an optical circulator, a power amplifier, and a polarization controller connected sequentially from input to output; the distributed feedback laser is connected to the first input terminal of the optical circulator; the first output terminal of the optical circulator is connected to the input terminal of the power amplifier, its second input terminal is connected to the output terminal of the feedback adjustment unit, and its second output terminal is connected to the input terminal of the distributed feedback laser; the power amplifier is used to amplify the intensity of the mid-infrared pump laser; the output terminal of the polarization controller is connected to the input terminal of the micro-ring resonator and is used to adjust the polarization state of the mid-infrared pump laser.

[0014] Furthermore, the microring resonator is a microring resonator with up-and-down channels; the input end of the microring resonator is connected to the output end of the polarization controller, and its drop end is connected to the input end of the optical splitter.

[0015] Furthermore, the feedback adjustment unit includes an optical fiber delay line and an adjustable optical fiber attenuator connected sequentially from input to output between the optical splitter and the optical circulator; the input end of the optical fiber delay line is connected to the first output end of the optical splitter for adjusting the phase of the feedback light; the output end of the adjustable optical fiber attenuator is connected to the second input end of the optical circulator for adjusting the intensity of the feedback light.

[0016] Furthermore, the spectral analysis unit employs a spectral analyzer; the distributed feedback laser is a 2μm band laser.

[0017] Furthermore, the splitting ratio of the optical splitter is 90:10, where 90 corresponds to the application light and 10 corresponds to the feedback light.

[0018] A method for generating a mid-infrared microcavity optical frequency comb based on self-injection locking, employing the aforementioned mid-infrared microcavity optical frequency comb generation system based on self-injection locking, is characterized by including the following steps:

[0019] Step 1: Connect the spectral analysis unit to the optical splitter, and output mid-infrared pump laser to the micro-ring resonator through the pump source unit. Adjust the pump source unit so that the intensity and polarization state of the mid-infrared pump laser meet the intensity threshold and phase matching conditions for the nonlinear four-wave mixing effect.

[0020] Step 2: The optical splitter divides the output light of the micro-ring resonator into feedback light and application light. The feedback light enters the pump source unit, and the application light enters the spectral analysis unit.

[0021] Step 3: Maintain constant mid-infrared pump laser power, adjust mid-infrared pump laser frequency so that the mid-infrared pump laser wavelength approaches any resonant peak position of the micro-ring resonator, and establish self-injection lock state.

[0022] Step 4: Based on the spectral information presented by the spectral analysis unit, the phase and intensity of the feedback light are adjusted by the feedback adjustment unit to achieve the optimal feedback state, and a stable optical frequency comb is formed in the micro-ring resonant cavity, thus completing the generation of the mid-infrared microcavity optical frequency comb.

[0023] Further, step 1 specifically involves connecting the spectrometer to the optical splitter, outputting mid-infrared pump laser through a distributed feedback laser, adjusting the output power of the mid-infrared pump laser through a power amplifier to make the intensity of the mid-infrared pump laser reach the intensity threshold that can excite the micro-ring resonator to generate a nonlinear four-wave mixing effect, and simultaneously adjusting the polarization state of the mid-infrared pump laser through a polarization controller to match it with the transverse electric eigenmode of the micro-ring resonator.

[0024] Further, step 3 specifically involves maintaining the mid-infrared pump laser power output by the distributed feedback laser constant through a power amplifier, adjusting the drive current and voltage of the distributed feedback laser to change its output frequency, so that the mid-infrared pump laser wavelength approaches any resonant peak position of the micro-ring resonator. When the mid-infrared pump laser wavelength enters the locked bandwidth of the resonant peak, the feedback light induces the pump frequency of the distributed feedback laser to approach and lock towards its own frequency, thus establishing a self-injection locked state.

[0025] Further, step 4 specifically involves coordinating the phase and intensity of the feedback light through the fiber delay line and the adjustable fiber attenuator until the spectrometer presents a stable, smooth, and bandwidth-maximized soliton optical frequency comb spectrum, achieving the optimal feedback state. In this way, a stable optical frequency comb is formed in the micro-ring resonator, completing the generation of the mid-infrared microcavity optical frequency comb.

[0026] The beneficial effects of this invention are:

[0027] 1. The self-injection locking-based mid-infrared microcavity optical frequency comb generation system and method provided by this invention inherits the inherent advantages of the self-injection locking scheme. The system has a simple structure and is easy to operate, and can achieve stable output of the optical frequency comb with one-button start. It has low requirements for pump laser performance, and achieves laser linewidth compression and noise suppression through feedback injection mechanism. It does not require the use of high-performance narrow-linewidth sweep laser, thereby reducing system cost and implementation difficulty.

[0028] 2. This invention reduces the output power requirements of distributed feedback lasers by using a power amplifier. By replacing traditional backscattering with the lower channel of a microring resonator as the feedback source, it overcomes the physical limitation that weak random scattering feedback in high-quality factor microcavities prevents locking from being initiated. Simultaneously, it avoids the problem of unidirectional isolation blocking the feedback path by the power amplifier, thus avoiding the dependence on high-quality factor microring resonators in self-injection locking schemes. It eliminates the need for matching microring resonator devices with extremely high fabrication capabilities, reducing the fabrication process requirements for microring resonators. Furthermore, this scheme is applicable to both positive and negative dispersion microring resonators, eliminating the need for precise adjustment of the dispersion characteristics of the microring resonator.

[0029] 3. The microring resonator used in this invention can be made of various materials such as silicon nitride and lithium niobate, which has broad material compatibility, low material dependence, and wide applicability. When implemented in the 2μm band, it can achieve stable output of mid-infrared microcavity optical frequency comb with low threshold, high repetition rate, and low noise, which significantly reduces system complexity and improves startup reliability. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of an embodiment of the self-injection locking mid-infrared microcavity optical frequency comb generation system of the present invention;

[0031] Figure 2 This invention presents the second-order dispersion characteristics of a silicon nitride microring resonator with a repetition frequency of 100G. The internal figure shows the TE0 fundamental mode field distribution of the microring resonator.

[0032] Figure 3 yes Figure 2 The corresponding micro-ring resonator optical frequency comb result diagram;

[0033] Figure 4 This invention presents the second-order dispersion characteristics of a silicon microring resonator with a repetition frequency of 45 GHz, and the internal figure shows the TEO fundamental mode field distribution of the microring resonator.

[0034] Figure 5 yes Figure 4 The corresponding micro-ring resonator optical frequency comb result diagram.

[0035] The attached figures are labeled as follows:

[0036] 1. Distributed feedback laser; 2. Optical circulator; 3. Power amplifier; 4. Polarization controller; 5. Micro-ring resonator; 6. Optical splitter; 7. Fiber delay line; 8. Adjustable fiber attenuator; 9. Spectrometer. Detailed Implementation

[0037] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] This invention provides a mid-infrared microcavity optical frequency comb generation system based on self-injection locking, such as... Figure 1 As shown, the system includes a pump light source unit, a micro-ring resonator 5, an optical splitter 6, a feedback adjustment unit, and a spectral analysis unit.

[0039] The pump source unit is used to emit mid-infrared pump laser. In this embodiment, the pump source unit includes a distributed feedback laser 1, an optical circulator 2, a power amplifier 3, and a polarization controller 4 connected sequentially from input to output. The distributed feedback laser 1 is connected to the first input terminal of the optical circulator 2. The distributed feedback laser 1 is a 2μm band laser. The optical circulator 2 is used to construct a unidirectional feedback loop to avoid interference from the output light of the distributed feedback laser 1 and other unnecessary light sources. The first output terminal of the optical circulator 2 is connected to the input terminal of the power amplifier 3, its second input terminal is connected to the output terminal of the feedback adjustment unit, and its second output terminal is connected to the input terminal of the distributed feedback laser 1. The power amplifier 3 is used to amplify the intensity of the mid-infrared pump laser to meet the intensity threshold for the nonlinear four-wave mixing effect in the micro-ring resonator 5. The output terminal of the polarization controller 4 is connected to the input terminal of the micro-ring resonator 5 and is used to adjust the polarization state of the mid-infrared pump laser.

[0040] Microring resonator 5 is used to generate a broadband optical frequency comb in the mid-infrared band; in this embodiment, microring resonator 5 is a microring resonator with up-and-down channels, specifically a silicon nitride microring resonator with a repetition frequency of 100 GHz, whose second-order dispersion characteristics are as follows: Figure 2 As shown, this microring resonator exhibits negative dispersion near the 2μm pump wavelength. In other embodiments, similar methods can also be used. Figure 4 The silicon microring resonator shown has a repetition frequency of 45 GHz and exhibits positive dispersion near the 2 μm pump wavelength. The input terminal of the microring resonator 5 is connected to the output terminal of the polarization controller 4, and its drop terminal is connected to the input terminal of the optical splitter 6. Addressing the challenges of difficult feedback light adjustment in self-injection locked states, the inability to simultaneously achieve a high quality factor and strong feedback, and the power amplifier blocking the feedback path, this embodiment uses the drop terminal of the microring resonator instead of traditional backscattering as the feedback source. This solution not only avoids the unidirectional isolation of the power amplifier but also overcomes the physical bottleneck of insufficient random scattering feedback in high-quality factor microring resonators to initiate locking, achieving independent and precise adjustment of the feedback light intensity and phase.

[0041] The first output terminal of the optical splitter 6 is connected to the feedback adjustment unit, and its second output terminal is connected to the spectral analysis unit or an external analysis and measurement device, used to split the output light of the micro-ring resonator 5 into feedback light and application light. In this embodiment, the splitting ratio of the optical splitter 6 is 90:10, where 90 corresponds to the application light and 10 corresponds to the feedback light.

[0042] The feedback adjustment unit is used to adjust the feedback light and send it to the pump light source unit. In this embodiment, the feedback adjustment unit includes an optical fiber delay line 7 and an adjustable optical fiber attenuator 8 connected sequentially from input to output between the optical splitter 6 and the optical circulator 2. The input end of the optical fiber delay line 7 is connected to the first output end of the optical splitter 6 to adjust the phase of the feedback light. The output end of the adjustable optical fiber attenuator 8 is connected to the second input end of the optical circulator 2 to adjust the intensity of the feedback light.

[0043] The spectral analysis unit is used to analyze the spectral information of the applied light; in this embodiment, the spectral analysis unit adopts a spectral analyzer 9.

[0044] The generation of a mid-infrared microcavity optical frequency comb using the aforementioned self-injection locking-based mid-infrared microcavity optical frequency comb generation system specifically includes the following steps:

[0045] Step 1: Connect the spectrometer 9 to the optical splitter 6. Output mid-infrared pump laser through the distributed feedback laser 1. Adjust the output power of the mid-infrared pump laser through the power amplifier 3 so that the intensity of the mid-infrared pump laser reaches the intensity threshold that can significantly excite the nonlinear four-wave mixing effect of the micro-ring resonator 5. At the same time, adjust the polarization state of the mid-infrared pump laser through the polarization controller 4 to match it with the transverse electric eigenmode of the micro-ring resonator 5, so as to reduce coupling loss and improve nonlinear conversion efficiency.

[0046] Step 2: The optical splitter 6 splits the output light of the micro-ring resonator 5 into feedback light and application light. The feedback light enters the fiber delay line 7, and the application light enters the spectrometer 9.

[0047] Step 3: Keep the mid-infrared pump laser power output by the distributed feedback laser 1 constant through the power amplifier 3, adjust the driving current and voltage of the distributed feedback laser 1 to change its output frequency, so that the mid-infrared pump laser wavelength approaches any resonant peak position of the micro-ring resonator 5. When the mid-infrared pump laser wavelength enters the locked bandwidth of the resonant peak, the feedback light induces the pump frequency of the distributed feedback laser 1 to approach and lock its own frequency, and the self-injection locked state is established.

[0048] At this point, the first thing observed on the spectrometer 9 is a significant narrowing of the laser linewidth. The physical mechanism lies in the feedback light altering the carrier concentration and photon number density distribution within the cavity, enhancing laser coherence and effectively suppressing frequency drift and phase noise. The intensity of the applied spectral line output from the drop end of the micro-ring resonator 5 gradually increases from weak to strong, and the power of the mid-infrared pump laser reaches a relatively stable plateau, rather than the single-peak scanning process of traditional scanning methods. This stage signifies that the laser frequency has locked to the resonance peak, and the self-injection locked state has been established. In the self-injection locked state, when the resonance peak frequency shifts in the micro-ring resonator 5 due to thermal effects or Kerr nonlinear effects, the feedback light can automatically guide the pump frequency of the distributed feedback laser 1 to follow the change in the resonance peak, thereby maintaining frequency locking and effectively overcoming the mode-locking instability problem caused by resonance peak drift during optical frequency comb generation. During this process, the power amplifier 3 maintains a constant mid-infrared pump laser power output from the distributed feedback laser 1 to suppress refractive index drift caused by thermal effects within the micro-ring resonator 5, ensuring stable resonance conditions.

[0049] Step 4: Adjust the phase and intensity of the feedback light in tandem using the fiber delay line 7 and the adjustable fiber attenuator 8, such as... Figure 3 As shown, when the spectrometer 9 presents a stable, smooth, and bandwidth-maximized soliton optical frequency comb spectrum, it indicates that the system has been adjusted to the optimal feedback state, and a stable optical frequency comb is formed in the micro-ring resonator 5, thus completing the generation of the mid-infrared microcavity optical frequency comb.

[0050] This method can also be used to establish a self-injection locked state for positive dispersive microcavities, such as... Figure 5 As shown, its output spectrum differs significantly from that of the negative dispersive microcavity in terms of envelope shape and bandwidth characteristics.

[0051] In step 4, when the phase of the feedback light is adjusted via the fiber delay line 7, the spectrometer 9 behaves as follows:

[0052] When the feedback light intensity or phase does not reach optimal matching, its spectrum is dominated by a single narrow-band pump line. The nonlinear four-wave mixing effect has not been fully excited in the micro-ring resonator 5, so no obvious comb-like spectral structure appears. Unlike the traditional pump frequency scanning method, in the self-injection locked state, since the mid-infrared pump laser frequency has been locked to the resonance peak and maintained constant, the system will not experience the evolution path of first appearing a modulation instability (MI) comb spectrum and then transitioning to a soliton comb during the frequency scanning process. The traditional intermediate state of "MI comb" with gradually widening bandwidth will not appear on the spectrometer 9. Once the adjustable fiber attenuator 8 and fiber delay line 7 are adjusted to a suitable state, the spectrometer 9 will directly jump to a soliton optical frequency comb spectrum with clear bandwidth and equal spacing of comb teeth in a very short time.

[0053] Therefore, by coordinating the adjustment of the adjustable fiber attenuator 8 and the fiber delay line 7, the intensity and phase of the feedback light are repeatedly optimized until the system is adjusted to the optimal feedback state. At this point, the spectrometer 9 ultimately presents a stable, smooth, and bandwidth-maximized soliton optical frequency comb spectrum. Its characteristics are: clear, evenly spaced comb teeth with a smooth envelope, typically exhibiting a sech²-type envelope; the 3-dB bandwidth of the spectrum reaches its maximum value and no longer increases significantly with fine-tuning of the feedback parameters; the comb teeth are stable, without severe jitter or mode jumps.

[0054] To ensure stable system output, after step 3, the system power can be turned off and then restarted. Without any manual adjustments, a stable soliton optical frequency comb should directly appear in the spectrometer 9. Repeatedly switching the system on and off repeatedly achieves the above process, indicating that the generation of the mid-infrared micro-ring optical frequency comb has been successfully realized.

[0055] In practical applications, the spectrometer 9 can be removed and connected to an external analytical measurement device, or a first-level optical splitter can be connected after 90% of the branch of the optical splitter 6 to connect to an external analytical measurement device. For example, when used for gas detection, the spectrometer 9 can be removed or a first-level optical splitter can be connected after 90% of the branch of the optical splitter 6, so that the application light is passed into the absorption cell containing the gas to be measured. By utilizing the selective absorption characteristics of different gas molecules to specific wavelengths, the parallel detection of multiple trace gases such as CO2 and CH4 can be achieved through spectral inversion.

[0056] In traditional self-injection locking schemes, the feedback light primarily relies on Rayleigh scattering inherent within the microring resonator. However, for high-quality factor microcavities (with extremely low scattering loss), the Rayleigh scattering intensity is often very weak, making it difficult to provide sufficient feedback power to initiate locking or maintain stable mode locking. Furthermore, the intensity and phase of the feedback light cannot be independently adjusted, and when a power amplifier is introduced into the system, its unidirectional isolation completely blocks the back feedback path, limiting the application of self-injection locking schemes in scenarios requiring high pump power (such as the mid-infrared band). Unlike traditional schemes that use in-cavity Rayleigh scattering as the feedback source, this embodiment innovatively uses the drop end of the microring resonator as the feedback source. This design, while ensuring high-quality factor feedback, achieves independent and precise adjustment of the feedback parameters (intensity and phase), overcoming the technical bottleneck of traditional self-injection locking schemes that struggle to balance high-quality factor and strong feedback.

[0057] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present invention should be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A mid-infrared microcavity optical frequency comb generation system based on self-injection locking, characterized in that: It includes a pump light source unit, a micro-ring resonator (5), an optical splitter (6), a feedback adjustment unit, and a spectral analysis unit; The pump light source unit is used to emit mid-infrared pump laser; The input end of the micro-ring resonator (5) is connected to the output end of the pump light source unit, and its output end is connected to the input end of the optical splitter (6). The first output terminal of the optical splitter (6) is connected to the feedback adjustment unit, and its second output terminal is connected to the spectral analysis unit or external analysis and measurement equipment, which is used to split the output light of the micro-ring resonator (5) into feedback light and application light. The output of the feedback adjustment unit is connected to the input of the pump light source unit, and is used to adjust the feedback light and send it to the pump light source unit. The micro-ring resonant cavity (5) is used to generate an optical frequency comb under the action of the pump light source unit and the feedback adjustment unit; The spectral analysis unit is used to analyze the spectral information of the applied light.

2. The mid-infrared microcavity optical frequency comb generation system based on self-injection locking according to claim 1, characterized in that: The pump source unit includes a distributed feedback laser (1), an optical circulator (2), a power amplifier (3), and a polarization controller (4) connected sequentially from input to output. The distributed feedback laser (1) is connected to the first input terminal of the optical circulator (2); The first output terminal of the optical circulator (2) is connected to the input terminal of the power amplifier (3), its second input terminal is connected to the output terminal of the feedback adjustment unit, and its second output terminal is connected to the input terminal of the distributed feedback laser (1). The power amplifier (3) is used to amplify the intensity of the mid-infrared pump laser; The output of the polarization controller (4) is connected to the input of the micro-ring resonator (5) to adjust the polarization state of the mid-infrared pump laser.

3. The mid-infrared microcavity optical frequency comb generation system based on self-injection locking according to claim 2, characterized in that: The microring resonator (5) is an up-and-down microring resonator; The input end of the micro-ring resonator (5) is connected to the output end of the polarization controller (4), and its drop end is connected to the input end of the optical splitter (6).

4. The mid-infrared microcavity optical frequency comb generation system based on self-injection locking according to claim 3, characterized in that: The feedback adjustment unit includes an optical fiber delay line (7) and an adjustable optical fiber attenuator (8) connected sequentially from input to output between the optical splitter (6) and the optical circulator (2). The input end of the optical fiber delay line (7) is connected to the first output end of the optical splitter (6) to adjust the phase of the feedback light; The output end of the adjustable fiber optic attenuator (8) is connected to the second input end of the optical circulator (2) to adjust the intensity of the feedback light.

5. The mid-infrared microcavity optical frequency comb generation system based on self-injection locking according to claim 4, characterized in that: The spectral analysis unit uses a spectral analyzer (9). The distributed feedback laser (1) is a 2μm band laser.

6. The mid-infrared microcavity optical frequency comb generation system based on self-injection locking according to claim 4 or 5, characterized in that: The optical splitter (6) has a splitting ratio of 90:10, where 90 corresponds to the application light and 10 corresponds to the feedback light.

7. A method for generating a mid-infrared microcavity optical frequency comb based on self-injection locking, employing the mid-infrared microcavity optical frequency comb generation system based on self-injection locking as described in any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Connect the spectral analysis unit to the optical splitter (6), and output mid-infrared pump laser to the micro-ring resonator (5) through the pump source unit. Adjust the pump source unit so that the intensity and polarization state of the mid-infrared pump laser meet the intensity threshold and phase matching conditions for the nonlinear four-wave mixing effect. Step 2: The optical splitter (6) splits the output light of the micro-ring resonator (5) into feedback light and application light. The feedback light enters the pump source unit, and the application light enters the spectral analysis unit. Step 3: Maintain constant mid-infrared pump laser power, adjust mid-infrared pump laser frequency so that the mid-infrared pump laser wavelength approaches any resonance peak position of the micro-ring resonator (5), and establish self-injection lock state; Step 4: Based on the spectral information presented by the spectral analysis unit, the phase and intensity of the feedback light are adjusted by the feedback adjustment unit to make the feedback light reach the optimal feedback state. A stable optical frequency comb is formed in the micro-ring resonant cavity (5) to complete the generation of the mid-infrared micro-cavity optical frequency comb.

8. The method for generating a mid-infrared microcavity optical frequency comb based on self-injection locking according to claim 7, characterized in that: Step 1 specifically involves connecting the spectrometer (9) to the optical splitter (6), outputting a mid-infrared pump laser through the distributed feedback laser (1), adjusting the output power of the mid-infrared pump laser through the power amplifier (3) to make the intensity of the mid-infrared pump laser reach the intensity threshold that can excite the micro-ring resonator (5) to produce a nonlinear four-wave mixing effect, and adjusting the polarization state of the mid-infrared pump laser through the polarization controller (4) to match it with the transverse electric eigenmode of the micro-ring resonator (5).

9. The method for generating a mid-infrared microcavity optical frequency comb based on self-injection locking according to claim 8, characterized in that: Step 3 specifically involves maintaining the mid-infrared pump laser power output by the distributed feedback laser (1) constant through the power amplifier (3), adjusting the driving current and voltage of the distributed feedback laser (1) to change its output frequency, so that the mid-infrared pump laser wavelength approaches any resonant peak position of the micro-ring resonator (5), and when the mid-infrared pump laser wavelength enters the locked bandwidth of the resonant peak, the feedback light induces the pump frequency of the distributed feedback laser (1) to approach and lock its own frequency, and the self-injection locked state is established.

10. The method for generating a mid-infrared microcavity optical frequency comb based on self-injection locking according to claim 9, characterized in that: Step 4 specifically involves coordinating the phase and intensity of the feedback light through the fiber delay line (7) and the adjustable fiber attenuator (8) until the spectrometer (9) presents a stable, smooth, and bandwidth-maximized soliton optical frequency comb spectrum, achieving the optimal feedback state. Then, a stable optical frequency comb is formed in the micro-ring resonator (5), completing the generation of the mid-infrared microcavity optical frequency comb.

Images