Method and device for generating integrated start key single soliton microcavity optical frequency comb based on double-loop coupling system

Abstract

The invention relates to a method and a device for generating an integrated start key single soliton microcavity optical frequency comb based on a double-loop coupling system. Comprising a monolithic integrated III-V group pumping laser chip, a silicon-based CMOS process integrated double-coupling optical microcavity chip, a temperature control unit, a driving control unit, a light beam splitter, a detection unit, a photoelectric detector and a feedback control unit. According to the scheme, blue detuning of the single soliton microcavity optical frequency comb is realized through double-coupling microcavity tuning local dispersion. The invention provides a technical scheme of an integrated start key single soliton microcavity optical frequency comb. The problems of thermal instability, dependence on a high-quality factor micro-ring resonant cavity and relatively low output power of the single soliton micro-cavity optical frequency comb due to the fact that pump laser needs to be locked in micro-cavity red detuning when the single soliton micro-cavity optical frequency comb is generated in a single-cavity system are solved, and the system stability and reliability of the single soliton micro-cavity optical frequency comb are improved. According to the scheme, a feasible path is provided for engineering application of the microcavity optical frequency comb in the fields of communication, sensing and the like.

Description

Technical Field

[0001] This invention belongs to the field of integrated photonics and nonlinear optics, specifically relating to a method and apparatus for generating an integrated microcavity optical frequency comb, and more particularly to a method and apparatus for generating a keyed single soliton microcavity optical frequency comb based on a dual-ring coupling system. Technical Background Microcavity soliton optical frequency combs, as a type of coherently locked frequency light source excited in a semiconductor integrated microcavity, possess advantages such as a large number of wavelength channels and high coherence. They demonstrate enormous application potential in high-capacity information transmission and processing systems compatible with wavelength division multiplexing (WDM) technology. Compared to mode-locked laser frequency combs and electro-optic frequency combs, microcavity soliton optical frequency combs offer advantages such as small size, easy integration, low power consumption, low phase noise, and compatibility with WDM systems. With the development of artificial intelligence technology, multi-wavelength light sources compatible with WDM systems are becoming increasingly important. The frequency spacing of a microcavity soliton optical frequency comb is related to the radius of the microcavity. By adjusting the radius of the microcavity, the frequency spacing of the optical frequency comb can be made compatible with WDM systems. It can provide hundreds of mutually locked coherent light sources, and microcavity soliton optical frequency combs have significant application prospects in many fields such as future high-capacity optical communication and optical interconnection between data centers.

[0002] Single-soliton optical frequency combs in the anomalous dispersion region of microcavities exhibit ultra-narrow pulse characteristics in the time domain, which has significant application value in precision measurement, on-chip optical clocks, and other fields. However, the generation of negative dispersion microcavity solitons still faces two key problems: 1. Low conversion efficiency. The quantum-limited conversion efficiency of traditional red-detuned soliton schemes is only 3%-5%, which severely limits the overall output power of the optical frequency comb, and its low conversion efficiency reduces its utilization value; 2. The generation of microcavity soliton optical frequency combs often occurs in the red-detuned state of the microcavity, and external noise such as power jitter can easily cause the optical frequency comb to lose lock, reducing the stability of the generated microcavity optical frequency comb. Therefore, developing microcavity single-soliton optical frequency combs that combine miniaturization, thermal stability, and high conversion efficiency is the key to promoting the engineering application of microcavity optical frequency combs. Currently, a series of research methods have emerged, and in order to improve stability, a series of research schemes such as auxiliary modes, auxiliary lasers, and Brillouin lasers have been adopted. While techniques involving auxiliary photothermal balancing (patent CN111244741B) can typically achieve programmable soliton generation, they usually require an acousto-optic modulator or additional pump laser to introduce the laser into the microcavity through blue detuning, increasing system complexity. Furthermore, the generated soliton optical frequency comb remains red detuned, limiting conversion efficiency, and the generation of solitons in the microcavity still requires a complex evolutionary process. Additionally, the introduction of auxiliary modes necessitates specific design of the dispersion and mode coupling strength of the optical microcavity, reducing the universality of microcavity soliton fabrication.To improve the soliton conversion efficiency of microcavity systems, one approach is to fabricate soliton optical combs with special morphologies, such as soliton crystal optical combs. However, the fabrication of soliton crystal optical combs typically requires the creation of an additional potential well field (Synthesized soliton crystals. Nat Commun 12, 3179 (2021)), which reduces their application value. Alternatively, one approach is to create corresponding mode frequency shift points, such as in photonic crystal cavities (Spontaneous pulse formation in edgeless photonic crystal resonators. Nat. Photon. 15, 461–467 (2021)) and dual-cavity systems with significantly different free spectral ranges (Surpassing the nonlinear conversion efficiency of soliton microcombs. Nat. Photon. 17, 992–999). (2023). However, the pumps used in the aforementioned microcavity single-soliton optical frequency combs are often red-detuned, with the pump laser close to the resonant peak of the microcavity. Pump laser and amplifier jitter will still cause the pump laser to become misaligned with the resonant peak. Microcavity single-soliton optical frequency combs with further blue detuning have not yet been fabricated. The stability of microcavity single-soliton optical frequency combs still faces significant challenges. Furthermore, the aforementioned methods lack external references when locking the microcavity single-soliton optical frequency comb, making it difficult to guarantee its long-term stability. The integration and miniaturization of highly stable microcavity single-soliton optical frequency combs remain challenging, hindering the development of subsequent applications. Therefore, developing microcavity single-soliton optical frequency combs that combine miniaturization, thermal stability, and high conversion efficiency is crucial for their engineering applications. Summary of the Invention

[0003] To address the technical challenges of thermal stability, integration, and high conversion efficiency of microcavity solitons, this invention proposes a method and apparatus for generating integrated keyed soliton microcavity optical frequency combs based on a dual-ring coupling system. This aims to solve the problems of low thermal stability and conversion efficiency of soliton optical frequency combs in negatively dispersive microcavities. To this end, this invention achieves highly stable and efficient soliton generation by controlling microcavity dispersion through dual-ring coupling and combining it with blue detuned pump injection locking.

[0004] The unique feature of this invention lies in its primary basis for achieving injection-locked soliton optical frequency combs through microcavity blue detuning by adjusting local dispersion using dual coupling. The device constitutes a closed-loop optical feedback control system, specifically including: a monolithically integrated III-V group pump laser chip, a silicon-based CMOS process integrated dual-coupled optical microcavity chip, a temperature control unit, a drive control unit, an optical beam splitter, a detector unit, a photodetector, and a feedback control unit. The pump laser chip, the dual-coupled optical microcavity chip, the optical beam splitter, the detector unit, the photodetector, and the feedback control unit are connected sequentially to form a closed-loop optical feedback control circuit.

[0005] The monolithically integrated III-V group pump laser chip serves as a pump laser source, and forms a pump laser seed source by injection locking with a dual-coupled optical microcavity chip.

[0006] Furthermore, the III-V group pump laser chip is a distributed feedback (DFB) laser chip or a reflective semiconductor optical amplifier (RSOA) chip. The output facet of the pump laser chip is coated with an antireflection film and can be packaged at a specific angle to reduce facet reflection and prevent damage to the chip due to self-oscillation caused by reflected light. The pump laser chip forms a narrow-linewidth pump laser source by locking its output light with the injection of the main cavity in the dual-coupled optical microcavity chip. By adjusting the operating current of the pump laser chip, its output power can be controlled, thereby exciting and maintaining the generation of the optical frequency comb in the main cavity.

[0007] The silicon-based CMOS integrated dual-coupled optical microcavity chip is used to modulate dispersion and generate a single soliton microcavity optical frequency comb through the dual-cavity coupling effect.

[0008] Furthermore, the silicon-based CMOS integrated dual-coupled optical microcavity chip is a through-hole microcavity chip, including a main cavity and an auxiliary cavity. The coupling of the two cavities is achieved by optimizing the spacing between the main cavity and the auxiliary cavity, and there is a certain deviation between their free spectral ranges. The main cavity is used to generate a microcavity single soliton optical frequency comb, and narrow linewidth laser injection locking needs to be achieved in the blue detuning region of the main cavity. A metal thin film is provided on the surface of the auxiliary cavity. The drive control unit thermally tunes the metal thin film by applying a tuning current, thereby changing the resonance state of the auxiliary cavity to control the local dispersion of the main cavity.

[0009] Furthermore, the metal thin film is made of materials such as titanium, platinum, or gold, which have stable thermoelectric properties. By adjusting the power of the metal thin film on the auxiliary cavity, the crossover between specific resonance modes of the main cavity and the auxiliary cavity can be achieved, thereby adjusting the local dispersion.

[0010] Furthermore, the silicon-based CMOS integrated dual-coupled optical microcavity chip has tapered structures or gradient refractive index lenses on its input and output waveguides, which are used to achieve efficient optical coupling with the III-V group laser chip and downstream optical path components, respectively.

[0011] Furthermore, the pump laser chip and the dual-coupled optical microcavity chip can be integrated via heterogeneous integration, or they can be fabricated separately and then fixed and encapsulated using UV adhesive by optimizing the shape of the input waveguide of the dual-coupled optical microcavity chip. After encapsulation, the pump laser chip and the dual-coupled optical microcavity chip can be attached to a ceramic substrate, and their operating temperature can be precisely controlled by the temperature control unit. The output end of the microcavity chip optical frequency comb can be provided with an optical fiber coupling interface.

[0012] Furthermore, the materials for the main cavity and auxiliary cavity can be selected from CMOS process-compatible semiconductor materials such as silicon and silicon nitride.

[0013] The temperature control unit is used to control the operating temperature of the pump laser chip and the dual-coupled optical microcavity chip, ensuring their normal operation. Specifically, temperature monitoring can be achieved through temperature sensors such as thermistors, and the temperature can be adjusted by controlling the thermoelectric cooler (TEC) or heater based on the monitoring signal.

[0014] The drive control unit is a multi-channel, high-precision, low-noise current source. One output channel of the current source is connected to the pump laser chip, and the driving power and operating wavelength of the pump laser chip are controlled by adjusting the output current. The other output channel is connected to the metal thin film of the auxiliary cavity, and the position of the resonant peak of the auxiliary cavity is controlled by adjusting the output current, thereby tuning the relative dispersion between the main cavity and the auxiliary cavity.

[0015] The optical beamsplitter has its input end optically connected to the output end of the optical frequency comb of the dual-coupled optical microcavity chip. This beamsplitter splits the optical frequency comb signal generated by the dual-coupled optical microcavity chip into two paths: one path serves as the main output signal of the system; the other path is optically connected to the input end of the detection unit to provide a feedback monitoring signal.

[0016] The detection unit receives the optical frequency comb signal from the optical beam splitter's splitting path at its input terminal. This signal is used to monitor changes in the center wavelength of the optical frequency comb caused by environmental and other factors. It can be a high-precision FP cavity. Wavelength-sensitive devices such as unequal-arm Mach-Zehnder interferometers or locally ultra-narrow linewidth phase-shifting gratings.

[0017] The input end of the photodetector is optically connected to the output end of the detector unit to detect the optical signal output by the detector unit and convert it into an electrical signal to reflect the power and state changes of the optical frequency comb.

[0018] The feedback control unit is connected to the photodetector and is used to receive the electrical signals output by it. This unit mainly includes ADC (analog-to-digital converter) and DAC (digital-to-analog converter) functional modules. The ADC module is used to collect the voltage of the photodetector to monitor the evolution state of the optical frequency comb; the DAC module generates a control voltage based on the state information to tune the operating current of the pump laser chip in real time, thereby tuning the laser wavelength by changing the refractive index inside the pump laser chip, and realizing the automatic locking and long-term stability of the microcavity single soliton optical frequency comb.

[0019] Accordingly, the present invention also provides a method for generating an integrated keyed single soliton microcavity optical frequency comb based on the above-mentioned device, comprising the following steps: S1. System initialization and pump setup: Start the temperature control unit to bring the pump laser chip and the dual-coupled optical microcavity chip to the set operating temperature; drive the pump laser chip and adjust its operating current and temperature so that the wavelength of its output laser is injected and locked to a resonant mode of the main cavity in the blue detuning region, forming a stable pump light source, and exciting the initial optical frequency comb in the main cavity; S2. Dispersion modulation and soliton excitation: The driving control unit applies a tuning current to the metal thin film of the auxiliary cavity to change the position of the resonance peak of the auxiliary cavity, so that it is controllably coupled with the pump mode of the main cavity, thereby enhancing the local anomalous dispersion of the main cavity near the pump mode; this operation causes the optical frequency comb in the main cavity to transform from a broadband modulation unstable state to a coherent single soliton state. S3. Feedback Locking and Key-on Operation: The feedback control unit is activated, enabling the device to enter a closed-loop operating mode. Based on the feedback optical path split from the output signal of the dual-coupled optical microcavity chip optical frequency comb by the optical beam splitter, the detection unit and photodetector monitor the state changes of the optical frequency comb in real time and feed the signal back to the feedback control unit. This unit processes the signal through its internal algorithm, generates control commands in real time, and directly adjusts the operating current of the pump laser chip accordingly, thereby automatically locking and stabilizing the single soliton optical frequency comb at the optimal operating point, achieving long-term stable operation in a "key-on" manner.

[0020] The technical solution proposed in this invention has the following technical effects: By injecting and locking the pump laser into the main cavity in the blue detuned region, and combining this with dual-ring coupling to control the local dispersion of the main cavity, the system can achieve the transition from a four-wave mixing frequency comb to a single soliton frequency comb in the blue detuned region. This approach avoids the inherent thermal instability problems caused by soliton generation at or near the resonance peak in the red detuned region, and the use of blue detuned pumping itself helps to improve the temperature stability of the system.

[0021] Based on the effect of dual-ring assisted enhancement of local anomalous dispersion in the main cavity, the efficient conversion of optical field energy into soliton states is promoted, thereby improving the optical-to-optical conversion efficiency of the single soliton optical frequency comb and realizing the generation of a microcavity single soliton optical frequency comb with relatively high output power.

[0022] By employing an on-chip integrated unequal-arm Mach-Zehnder interferometer (MZI) as a frequency calibration reference, combined with a closed loop consisting of a photodetector and a feedback control unit, laser wavelength drift can be calibrated in real time and feedback control can be performed. This design eliminates the dependence of the long-term stability of the optical frequency comb on a large-volume external reference, ultimately realizing the full-chain control of the microcavity single soliton optical frequency comb from generation to self-stabilization, improving the overall system's ease of operation (keyless start) and long-term stability.

[0023] This scheme reduces the reliance on the high quality factor (high Q value) of the main microcavity itself through a dual-ring coupling dispersion control mechanism, relaxes the process requirements for microcavity manufacturing, and helps promote the practical development of integrated keyed single soliton optical frequency comb generation devices. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a high-conversion-efficiency single soliton frequency comb generation device with integrated keying provided in an embodiment of the present invention; Figure 2 This is the spectrum of the blue detuned locked four-wave mixing state; Figure 3 To obtain the spectrum of blue detuned solitons generated in the main cavity by adjusting the auxiliary cavity; Figure 4 A schematic diagram of an on-chip unequal-arm Mach-Zehnder interferometer used as an on-chip detector; Figure 5 Here is the flowchart for the feedback control unit algorithm; Figure label: 1-Pump laser chip; 2-Dual-coupled optical microcavity chip; 21-Main cavity; 22-Auxiliary cavity; 23-Metal thin film; 3-Temperature control unit; 31-Thermistor; 4-Fiber beam splitter; 5-Detector unit; 6-Photodetector; 7-Feedback control unit; 8-Drive control unit. Detailed Implementation

[0025] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0026] The following description, with reference to the accompanying drawings, illustrates an embodiment of an integrated keyed single-soliton microcavity optical frequency comb generation device based on a dual-ring coupling system. The microcavity single-soliton optical frequency comb, which balances high conversion efficiency and high thermal stability, as mentioned in the background art, is complex to implement, costly, and difficult to miniaturize. This application provides a method and apparatus for generating an integrated keyed single-soliton microcavity optical frequency comb based on a dual-ring coupling system. In this apparatus, the local dispersion of the enhanced microcavity is adjusted by coupling the dual rings, and the blue-detuned steady-state single-soliton optical frequency comb is generated through injection locking of its pump laser chip. This improves the output power and temperature stability of the microcavity soliton and eliminates the dependence of the integrated keyed microcavity single-soliton optical frequency comb generation on a high-quality factor microcavity.

[0027] Specifically, such as Figure 1 As shown, this embodiment provides a device for generating an integrated keyed single soliton microcavity optical frequency comb based on a dual-ring coupling system. The device specifically includes a pump laser chip 1, a dual-coupled optical microcavity chip 2, a main cavity 21, an auxiliary cavity 22, a metal thin film 23, a temperature control unit 3, a thermistor 31, an optical fiber beam splitter 4, a detector unit 5, a photodetector 6, a feedback control unit 7, and a drive control unit 8.

[0028] Among them, the pump laser chip 1 adopts a semiconductor DFB chip with a center wavelength of 1550.12 nm and an output power of 100 mW. An antireflection film needs to be deposited on the output end face of the pump laser chip to reduce end face reflection and avoid damage to the chip caused by reflection-induced pulse self-oscillation. The output wavelength of the pump laser chip can be controlled by tuning the operating current. The main cavity 21 adopts a silicon nitride microring resonator with a free spectral range of 100 GHz and a quality factor of 3×10. 6 The dual-coupled optical microcavity chip 2 requires a corresponding graded waveguide structure to achieve efficient coupling between the dual-coupled optical microcavity chip and the pump laser chip, and between the dual-coupled optical microcavity chip and the output fiber array. The coupling efficiency between the pump laser chip and the dual-coupled optical microcavity chip is approximately 60%, and the coupling loss between the dual-coupled optical microcavity chip and the fiber array is approximately 70%. The generation of the main cavity optical frequency comb is achieved through injection locking between the pump laser chip and the dual-coupled optical microcavity chip. The auxiliary cavity 22 adopts a silicon nitride microring resonator with a free spectral range of 103.1 GHz and a quality factor of 1×10⁻⁶. 6The auxiliary cavity surface needs to be deposited with a thin metal film 23 to achieve flexible control of its resonance peak, thereby enabling the modulation of local dispersion in the main cavity 21. The pump laser chip 1 and the dual-coupled optical microcavity chip 2 need to be integrated on the same silicon nitride ceramic substrate. After optical alignment, the laser chip-silicon nitride chip-fiber array are solidified and packaged using ultraviolet adhesive, and then the whole assembly is attached to the corresponding butterfly-shaped housing. The temperature control unit 3 includes a thermistor 31 attached to the butterfly-shaped housing and a corresponding temperature control circuit. The thermistor 31 monitors the temperature of the package in real time, and the temperature control circuit drives the thermoelectric cooler (TEC) located at the bottom of the ceramic substrate based on this signal. The independent TEC is driven by the temperature control unit 3 to compensate for changes in ambient temperature, thereby stabilizing the operating temperature. The fiber optic beam splitter 4 is mainly used to separate the output frequency comb signal. It is a polarization-maintaining fiber optic beam splitter with a splitting ratio of 99:1. The main output end, which accounts for 99% of the optical power, serves as the optical frequency comb signal output port of the device. The auxiliary output end, which accounts for 1% of the optical power, is optically connected to the input end of the detection unit 5 to provide feedback monitoring signals. The detection unit 5 is an on-chip unequal-arm Mach-Zehnder interferometer. This interferometer requires precise temperature control. The length difference between its unequal arms is 30 cm. Wavelength locking is achieved by locking the center wavelength of the output soliton at the bottom of the unequal-arm interference peak. A schematic diagram of this locking structure is shown below. Figure 4 As shown; the photodetector 6 is used to monitor power changes, and the analog voltage signal it generates is transmitted to the feedback control unit 7; the feedback control unit 7 is mainly used to adjust the operating current of the pump laser chip 1 to adjust the refractive index, thereby achieving fine tuning of the center wavelength of the output microcavity optical frequency comb; the drive control unit 8 is used to provide drive current for the pump laser chip 1 and to provide tuning current for the thermal tuner of the auxiliary cavity 22. Figure 2 The spectrum of the modulation-unstable optical frequency comb generated by the pump laser chip and main cavity 21 under blue detuned injection locking is shown. Figure 3 To adjust the position of the resonant peak of auxiliary cavity 22 and thus the blue detuned microcavity soliton spectrum when generating a steady-state modulated unstable optical frequency comb, the conversion efficiency of the microcavity soliton is usually obtained by analyzing the spectrum of the output soliton, which is defined as the ratio of the output soliton power to the total output power. Since there is a part of the frequency comb component at the central pump in the output spectrum, the logarithmic coordinates of the output spectrum need to be converted to linear coordinates and fitted according to the sech2 function to extract the part of the frequency comb power at the central pump. Then, it is summed with the power of the remaining frequency comb, and the ratio of this to the overall power of the spectrum is the conversion efficiency of the soliton optical frequency comb. According to this method, the conversion efficiency of the microcavity soliton optical frequency comb is 26.7%. Therefore, the conversion efficiency from pump light to soliton optical frequency comb is greater than 20%, which exceeds the limit of the traditional microcavity single soliton conversion efficiency (3%~5%). Figure 5The flowchart illustrates the feedback control algorithm for achieving long-term stable operation of the injected locked microcavity soliton optical frequency comb, executed by the feedback control unit 7 to maintain the locked state. This process is based on a specific implementation where the detector unit 5 is an unequal-arm Mach-Zehnder interferometer (MZI). Its core principle is to lock the center wavelength of the optical frequency comb at the bottom of the interference peak (i.e., the point of minimum power) of the MZI transmission spectrum. When the center wavelength is precisely located at the bottom of the peak, the error voltage output by the photodetector 6 is zero (or a set reference value). After system startup or unexpected loss of lock, the algorithm executes the following process to establish or restore lock (corresponding to...). Figure 5 (Flowchart): Read the current error voltage: Obtain the MZI output power (i.e., error voltage) corresponding to the current optical frequency comb center wavelength. Active perturbation and direction judgment: Fine-tune (e.g., slightly reduce) the operating current of the pump laser chip 1 and read the error voltage again. By comparing the trend of error voltage changes before and after the perturbation, the offset direction of the pump wavelength relative to the bottom of the MZI interference peak can be determined (i.e., deviation towards red or blue shift). Closed-loop locking: The feedback control unit 7 adjusts the driving current of the pump laser chip 1 in the opposite direction according to the determined offset direction, so that the center wavelength of the optical frequency comb moves towards the bottom of the interference peak. Subsequently, the algorithm enters the steady-state locking mode: continuously monitor the error voltage, and fine-tune the pump current in real time through internal algorithms (such as proportional-integral control) to drive and maintain the error voltage stable near zero. Through the above closed-loop control, the center wavelength of the optical frequency comb is finally stably locked at the wavelength corresponding to the bottom of the MZI interference peak, that is, the soliton generation point of the microcavity blue detuning region, thereby realizing the long-term stable operation of the single soliton optical frequency comb.

[0029] Furthermore, this embodiment also proposes a method for generating an integrated keyed single soliton microcavity optical frequency comb based on a dual-ring coupling system, comprising the following steps: 1) The pump laser chip 1, the dual-coupled optical microcavity chip 2, and the output fiber array are packaged on a high-precision displacement stage and housed in a butterfly-shaped shell. A thermistor 31 is attached to the butterfly shell, and the pump laser chip and the metal region of the auxiliary cavity 22 are driven by a gold wire connection. The unequal-arm Mach-Zehnder interferometer chip (as the detector unit 5) is connected to the system optical path via optical fiber and subjected to independent temperature control, completing the process. Figure 1 Optical coupling and electrical connection between the various devices; 2) The operating temperatures of the pump laser chip 1 and the dual-coupled optical microcavity chip 2 are set by the temperature control unit 3. The drive control unit 8 provides a drive current to the pump laser chip 1, setting its output power to 100 mW. Adjusting the operating temperature of the pump laser chip 1 injects its output wavelength into a blue-detuned resonant mode locked in the main cavity 21 of the dual-coupled optical microcavity chip 2, thereby exciting an initial modulation-unstable optical frequency comb within the main cavity 21. Its output spectrum is as follows: Figure 2 As shown; 3) A tuning current is applied to the metal thin film 23 on the surface of the auxiliary cavity 22 by the drive control unit 8, thermally tuning the resonant peak position of the auxiliary cavity 22 so that it undergoes a controllable mode crossover with the pump resonant mode of the main cavity 21. The spectral changes at the output of the dual-coupled optical microcavity chip 2 are monitored until the spectrum evolves into a stable single soliton state, such as... Figure 3 As shown, this indicates that the microcavity single soliton optical frequency comb has been successfully generated; 4) Adjust the operating temperature of the on-chip unequal-arm Mach-Zehnder interferometer (detector unit 5) to change the phase of its interference spectrum so that the wavelength of the resonance valley (minimum power point) of its interference transmission spectrum precisely coincides with the center wavelength of the stable single soliton optical frequency comb output in step 3), thus completing the initial calibration of the feedback locking point. 5) Start the feedback control unit 7, and the system executes as follows: Figure 5 The feedback control algorithm is shown. First, it reads the voltage signal output by the photodetector 6 (i.e., the output power of the detector unit 5, used as the error voltage). Then, it actively fine-tunes the operating current of the pump laser chip 1 and reads the error voltage again. By comparing the trends of the two voltage values, it determines the offset direction of the optical frequency comb's center wavelength. Finally, based on the determined offset direction, the feedback control unit 7 outputs a control command to the drive control unit 8, which in turn adjusts the drive current of the pump laser chip 1 in the opposite direction, bringing the error voltage close to zero. This automatically locks the center wavelength of the optical frequency comb at the interference valley of the detector unit 5, achieving long-term, stable operation of the microcavity single soliton optical frequency comb.

[0030] This scheme enables the generation of blue-detuned integrated keyed microcavity single soliton microcavity optical frequency combs, effectively eliminating the dependence of integrated keyed single soliton microcavity optical frequency combs on high-quality factor microcavities.

Claims

1. A device for generating an integrated keyed single soliton microcavity optical frequency comb based on a dual-ring coupling system, characterized in that, include: Monolithically integrated III-V group pump laser chip, silicon-based CMOS process integrated dual-coupled optical microcavity chip, temperature control unit, drive control unit, optical beam splitter, detector unit, photodetector and feedback control unit; The pump laser chip, dual-coupled optical microcavity chip, optical beam splitter, detector unit, photodetector and feedback control unit are connected in sequence to form a closed-loop optical feedback control circuit. The pump laser chip serves as a pump laser source, and its output is coupled to the input of the dual-coupled optical microcavity chip. The dual-coupled optical microcavity chip is used to modulate dispersion and generate a single soliton microcavity optical frequency comb through the dual-cavity coupling effect, and its output end is connected to the input end of the optical beam splitter. The temperature control unit is used to monitor and control the temperature of the pump laser chip and the dual-coupled optical microcavity chip; The drive control unit is connected to the pump laser chip and the dual-coupled optical microcavity chip respectively, and is used to drive the pump laser chip and tune the dual-coupled optical microcavity chip. The input end of the optical beam splitter is optically connected to the output end of the optical frequency comb of the dual-coupled optical microcavity chip, and splits the input light into two paths. One path serves as the main output of the device, and the other path is optically connected to the input end of the detection unit to provide a feedback monitoring signal. The detection unit receives the optical frequency comb signal from the optical beam splitter's beam splitting path at its input end, which is used to monitor the change in the center wavelength of the optical frequency comb, and its output end is connected to the input end of the photodetector. The photodetector has its input end connected to the output end of the detector unit for detecting the optical signal output by the detector unit, and its output end connected to the input end of the feedback control unit. The output of the feedback control unit is connected to the pump laser chip and is used to adjust the operating current of the pump laser chip according to the electrical signal output by the photodetector.

2. The apparatus according to claim 1, characterized in that, The dual-coupled optical microcavity chip is a through-type micro-ring structure, including a main cavity and an auxiliary cavity. The coupling of the two cavities is achieved by optimizing the spacing between the main cavity and the auxiliary cavity, and there is a certain deviation between their free spectral ranges. The main cavity is used to generate a single soliton microcavity optical frequency comb, and narrow linewidth laser injection locking needs to be achieved in the blue detuning region of the main cavity; The auxiliary cavity surface is provided with a metal thin film. The drive control unit thermally tunes the metal thin film by applying a tuning current, thereby changing the resonance state of the auxiliary cavity and controlling the local dispersion of the main cavity.

3. The apparatus according to claim 2, characterized in that, The metal film is made of titanium, platinum, or gold.

4. The apparatus according to claim 2, characterized in that, The ends of the input and output waveguides of the dual-coupled optical microcavity chip are provided with tapered structures or gradient refractive index lenses.

5. The apparatus according to claim 1, characterized in that, The pump laser chip is a distributed feedback laser chip or a reflective semiconductor optical amplifier chip, and its output end face is coated with an anti-reflection film.

6. The apparatus according to claim 1, characterized in that, The pump laser chip and the dual-coupled optical microcavity chip are coupled and packaged by heterogeneous integration or optical adhesive bonding.

7. The apparatus according to claim 1, characterized in that, The temperature control unit includes a temperature sensor.

8. The apparatus according to claim 1, characterized in that, The drive control unit is a multi-channel current source, with one output channel connected to the pump laser chip to control its drive current, and another output channel connected to the metal thin film of the auxiliary cavity to provide the tuning current.

9. The apparatus according to claim 1, characterized in that, The detection unit is a wavelength-sensitive device, wherein the wavelength-sensitive device is a Fabry-Perot cavity, an unequal-arm Mach-Zehnder interferometer, or a phase-shifting grating.

10. A method for generating an integrated keyed single soliton microcavity optical frequency comb based on a dual-ring coupling system, employing the apparatus described in any one of claims 1-9, characterized in that... The method for generating the integrated keyed single soliton microcavity optical frequency comb includes: S1. Pump Setup and Initial Excitation: Control the temperature control unit and drive control unit to adjust and lock the output wavelength of the pump laser chip to a blue detuned resonant mode in the main cavity, so as to excite the initial optical frequency comb in the main cavity; S2. Dispersion modulation and soliton state excitation: The drive control unit tunes the resonant state of the auxiliary cavity to controllably couple it with the pump mode of the main cavity, thereby enhancing the local anomalous dispersion of the main cavity and thus converting the optical frequency comb in the main cavity into a single soliton state; S3. Feedback Locking and Stable Operation: The feedback control unit is activated; based on the feedback optical path signal split by the optical beam splitter, the state of the output microcavity optical frequency comb is monitored by the detection unit and photodetector, and the monitoring signal is fed back to the feedback control unit; the feedback control unit generates control commands according to the monitoring signals, and adjusts the operating current of the pump laser chip to achieve automatic locking and long-term stable operation of the single soliton microcavity optical frequency comb.

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