Frequency stabilization device and frequency stabilization method of optical frequency comb

Abstract

The invention provides a frequency stabilization device and a frequency stabilization method of an optical frequency comb, and relates to the technical field of optics, the optical frequency comb can be generated based on a self-injection locking principle through an optical frequency comb unit comprising a laser and a first micro-resonator of which the end faces are coupled, and then the optical frequency comb is generated through the first micro-resonator. Through the control system, the second micro-resonator is used as a reference resonator, the laser with the specific frequency of the optical frequency comb and the resonance mode of the second micro-resonator can be locked, and the frequency stability of the laser with all frequencies of the optical frequency comb is improved.

Description

Technical Field

[0001] The present invention relates to the field of optical technology, and in particular to a frequency stabilization device and a frequency stabilization method for an optical frequency comb. Background Art

[0002] Optical frequency combs have excellent time-frequency characteristics, such as narrow pulse width, high frequency accuracy, and good coherence. In recent years, they have become a research hotspot in fields such as ultrafast laser technology and metrology, and have been widely used in cutting-edge research fields such as precision measurement, optical computing, and optical communications. Optical frequency combs appear as equally spaced pulse signals in the time domain and as a series of equally spaced frequency components with a fixed phase relationship in the frequency domain. The mathematical expression of the spectrum of an optical frequency comb is: ,in is the frequency of the nth frequency component in the optical frequency comb, is the offset frequency of the carrier envelope of the optical frequency comb, is the repetition frequency of the optical frequency comb, and n is an integer.

[0003] Maintaining the frequency stability and phase consistency of an optical frequency comb is crucial for driving breakthroughs in fields such as precision metrology, quantum technology, and optical communications. Therefore, there is an urgent need for a frequency stabilization device for optical frequency combs. Summary of the Invention

[0004] The present invention provides a frequency stabilization device and a frequency stabilization method for an optical frequency comb, so as to solve the defects existing in the related art.

[0005] The present invention provides a frequency stabilization device for an optical frequency comb, comprising: an optical frequency comb unit, an oscillator, and a frequency stabilization system; The optical frequency comb unit includes a laser and a first microresonator, wherein the first microresonator is etched on a photonic chip, and the laser is coupled to an input waveguide end face of the photonic chip; The frequency stabilization system includes a filter, a phase modulator, a second microresonator, a photodetector, a phase shifter, a mixer and a servo controller; The output waveguide of the photonic chip is connected to the filter, the phase modulator, the second microresonator, the photodetector, the mixer and the servo controller in sequence, the oscillator is connected to the phase modulator and the phase shifter respectively, the phase shifter is connected to the mixer, and the servo controller is connected to the laser; The optical frequency comb unit is used to generate an optical frequency comb based on the self-injection locking principle; The oscillator is used to generate a radio frequency signal; The filter is used to select a laser with a target frequency from the optical frequency comb; the laser with the target frequency passes through the phase modulator, the second microresonator, the photodetector, the mixer and the servo controller in sequence, thereby controlling the pump current of the laser and locking the laser with the target frequency to the resonant mode of the second microresonator.

[0006] According to the present invention, a frequency stabilization device for an optical frequency comb is provided, wherein the frequency stabilization system includes a first frequency stabilization system and a second frequency stabilization system, wherein the first frequency stabilization system and the second frequency stabilization system each include a filter, a phase modulator, a second microresonator, a photodetector, a phase shifter, a mixer, and a servo controller; The filter in the first frequency stabilization system and the filter in the second frequency stabilization system are both connected to the output waveguide of the photonic chip; The phase modulator and phase shifter in the first frequency stabilization system, and the phase modulator and phase shifter in the second frequency stabilization system, are both connected to the oscillator; The servo controller in the first frequency stabilization system is connected to the laser and is used to control the pump current of the laser and lock the laser of the target frequency selected by the filter in the first frequency stabilization system to the resonant mode of the second microresonator in the first frequency stabilization system; The servo controller in the second frequency stabilization system is connected to the first tuning structure of the first microresonator, and is used to control the current of the first tuning structure to lock the laser of the target frequency selected by the filter in the second frequency stabilization system to the resonant mode of the second microresonator in the second frequency stabilization system.

[0007] According to the present invention, a frequency stabilization device for an optical frequency comb is provided, wherein the optical frequency comb unit includes a first optical frequency comb unit and a second optical frequency comb unit, and the frequency stabilization system includes a third frequency stabilization system, a fourth frequency stabilization system, and a wavelength division multiplexer; the third frequency stabilization system and the fourth frequency stabilization system share the same phase modulator and the same second microresonator; The filter in the third frequency stabilization system is connected to the output end of the first optical frequency comb unit; The filter in the fourth frequency stabilization system is connected to the output end of the second optical frequency comb unit; The input end of the wavelength division multiplexer is connected to the output waveguide of the same second microresonator, the first output end is connected to the photodetector in the third frequency stabilization system, and the second output end is connected to the photodetector in the fourth frequency stabilization system; The servo controller in the third frequency stabilization system is connected to the laser in the first optical frequency comb unit, and is used to control the pump current of the laser in the first optical frequency comb unit, so as to lock the laser of the target frequency selected by the filter in the third frequency stabilization system to the resonant mode of the same second microresonator; The servo controller in the fourth frequency stabilization system is connected to the laser in the second optical frequency comb unit, and is used to control the pump current of the laser in the second optical frequency comb unit, so as to lock the laser of the target frequency selected by the filter in the fourth frequency stabilization system to the resonant mode of the same second microresonator.

[0008] According to a frequency stabilization device for an optical frequency comb provided by the present invention, the resonance frequency fluctuation of the second microresonator is less than or equal to a preset threshold.

[0009] According to the optical frequency comb stabilization device provided by the present invention, the second microresonator may include a vortex line structure microresonator, a microring structure microresonator, a finger structure microresonator and a disk structure microresonator; The vortex line structure microresonator, the microring structure microresonator, the finger structure microresonator and the disk structure microresonator are prepared based on different materials.

[0010] According to the frequency stabilization device for an optical frequency comb provided by the present invention, the laser includes a laser chip, and the filter includes a microring filter.

[0011] According to the frequency stabilization device of an optical frequency comb provided by the present invention, the optical frequency comb unit, the filter, the phase modulator, the second microresonator and the photodetector are integrated on a chip, and the phase shifter, the mixer and the servo controller are integrated on an electronic control board.

[0012] According to the frequency stabilization device of an optical frequency comb provided by the present invention, metal electrodes are integrated on the input waveguide of the photonic chip, the first microresonator, and the output waveguide of the photonic chip; The metal electrodes integrated on the input waveguide and output waveguide of the photonic chip are used to tune the light transmission phase of the waveguide section; The metal electrode integrated on the first microresonator is used to tune the free spectral range of the first microresonator.

[0013] According to the optical frequency comb frequency stabilization device provided by the present invention, the frequency stabilization system further includes a second modulation structure of the second micro-modulator; The second modulation structure is used to control a stable position of a resonant mode of the second microresonator.

[0014] The present invention further provides a method for stabilizing the frequency of an optical frequency comb implemented based on the above-mentioned frequency stabilization device of the optical frequency comb, comprising: Generate optical frequency comb based on the principle of self-injection locking; Selecting a laser of a target frequency from the optical frequency comb, and performing phase modulation on the laser of the target frequency based on a radio frequency signal to obtain a modulated signal; inputting the modulated signal into a second microresonator to obtain an output optical signal of the second microresonator; Converting the output optical signal into an electrical signal, and inputting a phase-shifted signal obtained by phase-shifting the electrical signal and the radio frequency signal into a mixer to obtain an error signal reflecting the frequency deviation between the output frequency of the laser and the resonant frequency of the second microresonator; Based on the error signal, the output frequency of the laser is controlled to lock the laser light of the target frequency to the resonant mode of the second microresonator.

[0015] The optical frequency comb frequency stabilization device and method provided by the present invention utilizes an optical frequency comb unit comprising an end-coupled laser and a first microresonator to generate an optical frequency comb based on the principle of self-injection locking. This is further enhanced by the on-chip integrated first microresonator. Using a control system and using a second microresonator as a reference resonator, laser light at a specific frequency in the optical frequency comb can be locked to the resonant mode of the second microresonator, improving the frequency stability of laser light at all frequencies in the optical frequency comb. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the present invention or related technologies, the following briefly introduces the drawings required for use in the embodiments or related technical descriptions. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 This is one of the structural schematic diagrams of the frequency stabilization device of the optical frequency comb provided by the present invention.

[0018] Figure 2 It is a schematic diagram of the on-chip integrated structure of the frequency stabilization device of the optical frequency comb provided by the present invention.

[0019] Figure 3 This is the second structural schematic diagram of the frequency stabilization device of the optical frequency comb provided by the present invention.

[0020] Figure 4 This is the third structural schematic diagram of the frequency stabilization device of the optical frequency comb provided by the present invention.

[0021] Figure 5 It is a structural schematic diagram of the electronic device provided by the present invention. DETAILED DESCRIPTION

[0022] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0023] Figure 1 FIG. 1 is a schematic structural diagram of a frequency stabilization device for an optical frequency comb provided in an embodiment of the present invention. Figure 1 As shown, the frequency stabilization device of the optical frequency comb includes: an optical frequency comb unit 1, an oscillator 2 and a frequency stabilization system; The optical frequency comb unit 1 includes a laser 11 and a first microresonator 12. The first microresonator 12 is etched on the photonic chip. The laser 11 is coupled to the input waveguide end face of the photonic chip. The control system includes a filter 31, a phase modulator 32, a second microresonator 33, a photodetector 34, a phase shifter 35, a mixer 36 and a servo controller 37; The output waveguide of the photonic chip is connected to the input-through waveguide of the filter 31. The drop waveguide of the filter 31, the phase modulator 32, the second microresonator 33, the photodetector 34, the mixer 36 and the servo controller 37 are connected in sequence. The oscillator 2 is connected to the phase modulator 32 and the phase shifter 35 respectively. The phase shifter 35 is connected to the mixer 36. The servo controller 37 is connected to the laser 11. The optical frequency comb unit 1 is used to generate an optical frequency comb based on the self-injection locking principle; Oscillator 2 is used to generate radio frequency signal; The filter 31 is used to select a laser of a target frequency from the optical frequency comb; the laser of the target frequency passes through the phase modulator 32, the second microresonator 33, the photodetector 34, the mixer 36 and the servo controller 37 in sequence, and then controls the pump current of the laser 11 to lock the laser of the target frequency to the resonant mode of the second microresonator 33.

[0024] Specifically, the frequency stabilization device of the optical frequency comb provided in the embodiment of the present invention, the turnkey optical frequency comb (Turnkey Microcombs) unit may include a laser and a first microresonator. The laser may be a semiconductor laser, such as a distributed feedback semiconductor laser, or a laser chip. The first microresonator refers to a micro-nanostructure with a quality factor (Q) within a preset range, which may be 10 4 -10 9 , for example, a ring resonator. The photonic chip etched with the first microresonator can be made of materials such as silicon nitride.

[0025] The laser is coupled with the input waveguide end face of the photonic chip, so that the single-frequency laser A output by the laser is input from the input waveguide of the photonic chip and transmitted backward along the input waveguide. At the end face coupling position, the energy is transferred to the first microresonator through the evanescent wave coupling mechanism.

[0026] Backscattered light is excited in the first microresonator, and the backscattered light is coupled to the input waveguide and transmitted backward into the resonant cavity of the laser, forming a self-injection locked loop.

[0027] When the initial detuning between the laser mode (i.e., the laser's output frequency) and the resonance peak of the first microresonator is within the soliton excitation range and the phase of the backscattered light satisfies the feedback phase condition, the soliton state optical frequency comb B can be excited through the Kerr nonlinear effect. Thus, by coupling the laser to the input waveguide facet of a photonic chip etched with the first microresonator, full-chip optical frequency comb generation can be achieved, i.e., generating an optical frequency comb from a single chip. This structure eliminates the discrete components required by traditional optical frequency combs, such as active modulators and external feedback circuits. Instead, it achieves turnkey (i.e., instant-on) stable optical frequency comb output through the collaborative nonlinear dynamics of the laser and the first microresonator, reducing power consumption to the milliwatt level. This is a high-performance chip-based optical frequency comb generation solution.

[0028] In addition to the laser and the first microresonator, the optical frequency comb unit may further include a microlens structure to collimate or change the optical path, which is not specifically limited here.

[0029] The oscillator (Local Oscillator) may be a radio frequency source, such as a highly stable microwave source, for generating a radio frequency signal and transmitting the radio frequency signal to a phase modulator and a phase shifter in the control system.

[0030] Based on the PDH (Pound-Drever-Hall) frequency stabilization technology, the control system can use the second microresonator as a reference resonator to lock the target frequency laser of the optical frequency comb (i.e., the target frequency component) to the resonant mode of the second microresonator, that is, to lock the frequency of the target frequency laser to the resonant frequency of the second microresonator. This can greatly improve the frequency stability of the target frequency component and achieve noise suppression and stability improvement. Since there is a mode-locked relationship between the multiple frequency components of the optical frequency comb, the remaining frequency components will maintain the same frequency stability as the target frequency component, thus realizing an integrated multi-channel frequency-stabilized optical frequency comb. For multi-channel applications such as optical communications and optical computing, there is no need to independently lock multiple lasers, making the frequency-stabilized optical frequency comb possible for heterogeneous integration on a full chip.

[0031] In the control system, the filter can be either a conventional filter or a microring filter, comprising an integrated structure of input and output waveguides, a microring resonator, and a drop waveguide. The filter implements wavelength-selective filtering. The input ports of the filter's input and output waveguides receive an optical frequency comb B. Light from the optical frequency comb whose wavelength meets the resonant conditions of the microring resonator enters the microring resonator through evanescent wave coupling, forming a standing wave resonance. Laser light C at the target frequency is then output from the drop waveguide. Light from the optical frequency comb whose wavelength does not meet the resonant conditions of the microring resonator is directly transmitted and output from the output ports of the input and output waveguides. The output ports of the input and output waveguides can also be used to output the optical frequency comb for subsequent frequency stabilization. The filter's implementation relies on the high quality factor of the microring resonator to achieve narrow linewidth filtering. The free spectral range (FSR) of the microring resonator determines the channel spacing, and the microring resonator's electrical and thermal tunability enables tuning of the filtering range.

[0032] The filter can achieve efficient and compact wavelength selection function through resonant wavelength matching and evanescent wave coupling mechanism.

[0033] The phase modulator receives the RF signal generated by the oscillator and the laser light of the target frequency. Using the RF signal as the modulation frequency and the laser light of the target frequency as the carrier, the phase modulator uses an electro-optical modulator (EOM) to modulate the laser light of the target frequency. This generates a modulated signal D, which generates sidebands on either side of the carrier wave. The frequency spacing of the sidebands is the modulation frequency, and the amplitude of the sidebands must match the carrier wave to optimize error signal sensitivity. The modulation frequency is typically in the MHz range (e.g., 10MHz to 100MHz).

[0034] The second microresonator can be an optical resonant cavity with a minimum circumscribed rectangular frame size of less than or equal to centimeters. The second microresonator can serve as a high-fineness frequency reference, and its resonant frequency provides an absolute reference for the frequency of the laser of the target frequency. Figure 1 The second microresonator shown in FIG is a spiral microresonator made of silicon nitride material.

[0035] A modulated optical beat signal can be emitted from the second microresonator. The modulated optical beat signal contains interference information between the carrier and the sidebands. The modulated optical beat signal is transmitted to a photodetector, which converts the modulated optical beat signal into an electrical signal. The photodetector can be a photodiode.

[0036] Here, it is necessary to adjust the phase of the RF signal output by the oscillator to match the phase of the electrical signal output by the photodetector, ensuring the correct polarity of the error signal after mixing.

[0037] The phase shifter can shift the phase of the RF signal output by the oscillator, adjust the phase relationship between the reference signal and the reflected signal, and ensure maximum sensitivity and correct polarity of the error signal.

[0038] The mixer mixes the electrical signal output by the photodetector with the phase-shifted signal output by the phase shifter to extract a low-frequency error signal. This error signal reflects the frequency deviation between the target laser frequency and the resonant frequency of the second microresonator. The amplitude of the error signal is linearly related to the frequency deviation, and the polarity of the error signal indicates the direction of the frequency deviation.

[0039] The servo controller receives the error signal from the mixer and generates a feedback voltage using a proportional-integral-differential (PID) control algorithm. It then controls the laser's pump current through a piezoelectric ceramic (PZT) or current modulator, modulating the laser's output frequency so that the target frequency is locked to the resonant frequency of the second microresonator.

[0040] The optical frequency comb frequency stabilization device provided in the embodiments of the present invention utilizes an optical frequency comb unit comprising an end-coupled laser and a first microresonator to generate an optical frequency comb based on the principle of self-injection locking. This is further enhanced by the on-chip integrated first microresonator. By using a control system and using the second microresonator as a reference resonator, the laser light at a specific frequency in the optical frequency comb can be locked to the resonant mode of the second microresonator, thereby improving the frequency stability of the laser light at all frequencies in the optical frequency comb.

[0041] Based on the above embodiments, Figure 1 As shown, the frequency stabilization system also includes a second modulation structure T of the second microresonator, which is used to control the stable position of the resonant mode of the second microresonator, that is, the position where the resonant frequency of the microresonator appears. Here, the second modulation structure can be a thermoelectric cooler (TEC), which can be in contact with the substrate of the second microresonator and is used to drive the thermoelectric power generation effect of the semiconductor thermocouple pair through direct current to accurately actively control the temperature of the second microresonator, thereby changing the stable position of the resonant mode of the second microresonator, thereby reducing the output range of the servo controller, reducing the control difficulty, and improving the control accuracy.

[0042] Based on the above embodiment, the laser includes a laser chip, and the filter includes a microring filter, which makes it possible to achieve on-chip heterogeneous integration of a frequency-stabilized optical frequency comb.

[0043] Based on the above embodiments, Figure 2 As shown, the optical frequency comb unit including the laser 11 and the first microresonator 12, the filter 31, the phase modulator 32, the second microresonator 33 and the photodetector 34 are integrated on the chip 38, and the phase shifter 35, the mixer 36 and the servo controller 37 can be integrated on the electronic control board, so that the frequency stabilization device of the optical frequency comb can achieve high-density system-level packaging, breaking through the laboratory limitations and transforming the frequency stabilization device of the optical frequency comb from a laboratory precision instrument into an industrial-grade standard module.

[0044] Figure 1 The illustrated frequency stabilization device for an optical frequency comb can lock a specific frequency component of the optical frequency comb to the resonant mode of the second microresonator, improving the frequency stability of all frequency components of the optical frequency comb. However, the repetition rate of the optical frequency comb is still subject to drift. Based on this, embodiments of the present invention also provide a frequency stabilization device that can completely lock the repetition rate and carrier-envelope offset frequency of the optical frequency comb.

[0045] Based on the above embodiments, Figure 3 As shown, the frequency stabilization system includes a first frequency stabilization system and a second frequency stabilization system, that is, the frequency stabilization device can include an optical frequency comb unit 1 and two frequency stabilization systems. The first frequency stabilization system includes a filter 41, a phase modulator 42, a second microresonator 43, a photodetector 44, a phase shifter 45, a mixer 46, and a servo controller 47, and the second frequency stabilization system includes a filter 51, a phase modulator 52, a second microresonator 53, a photodetector 54, a phase shifter 55, a mixer 56, and a servo controller 57.

[0046] The filter 41 in the first frequency stabilization system and the filter 51 in the second frequency stabilization system are both connected to the output waveguide of the photonic chip in the optical frequency comb unit 1 .

[0047] The phase modulator 42 and the phase shifter 45 in the first frequency stabilization system, and the phase modulator 52 and the phase shifter 55 in the second frequency stabilization system are all connected to the oscillator 2 .

[0048] The servo controller 47 in the first frequency stabilization system is connected to the laser 11 in the optical frequency comb unit 1 and is used to control the pump current of the laser 11 to lock the laser light of the target frequency selected by the filter 41 in the first frequency stabilization system to the resonant mode of the second microresonator 43 in the first frequency stabilization system. The servo controller 57 in the second frequency stabilization system is connected to the first tuning structure of the first microresonator 12 in the optical frequency comb unit 1, and is used to control the current of the first tuning structure to lock the laser of the target frequency selected by the filter 51 in the second frequency stabilization system to the resonant mode of the second microresonator 53 in the second frequency stabilization system.

[0049] Specifically, the free spectral ranges of the filter 41 in the first frequency stabilization system and the filter 51 in the second frequency stabilization system can be different to filter out two frequency components in the optical frequency comb B, namely the laser light C1 of the target frequency and the laser light C2 of the target frequency.

[0050] Laser light C1 of the target frequency passes sequentially through phase modulator 42, second microresonator 43, photodetector 44, and mixer 46, generating a first error signal reflecting the frequency deviation between the frequency of laser light C1 of the target frequency and the resonant frequency of second microresonator 43. Here, the RF signal generated by oscillator 2 is phase-shifted by phase shifter 45 to generate a first phase-shifted signal. Mixer 46 mixes the first phase-shifted signal with the first electrical signal output by photodetector 44 to generate a first error signal.

[0051] The first error signal is transmitted to the servo controller 47. The servo controller 47 controls the pump current of the laser 11 according to the first error signal, adjusts the output frequency of the laser 11, and locks the laser C1 of the target frequency to the resonant mode of the second microresonator 43, that is, locks the frequency of the laser C1 of the target frequency to the resonant frequency of the second microresonator 43.

[0052] Laser light C2 of the second target frequency passes sequentially through phase modulator 52, second microresonator 53, photodetector 54, and mixer 56, generating a second error signal reflecting the frequency deviation between the target frequency laser light C2 and the resonant frequency of second microresonator 53. Here, the RF signal generated by oscillator 2 is phase-shifted by phase shifter 55 to generate a second phase-shifted signal. Mixer 56 mixes the second phase-shifted signal with the second electrical signal output by photodetector 54 to generate a second error signal.

[0053] The second error signal is transmitted to the servo controller 57, which controls the current of the first tuning structure according to the second error signal, modulates the free spectrum range of the first microresonator 12, and locks the laser light C2 of the target frequency to the resonant mode of the second microresonator 53, that is, locks the frequency of the laser light C2 of the target frequency to the resonant frequency of the second microresonator 53.

[0054] It is understood that the first tuning structure of the first microresonator can be a thermistor, and by applying current to the first tuning structure, the response bandwidth of the second microresonator 53 can be made to reach hundreds of kHz.

[0055] In the frequency stabilization device of the optical frequency comb provided in the embodiment of the present invention, the optical frequency comb unit can have two modulation degrees of freedom, namely, the output frequency of the modulated laser and the free spectral range of the first microresonator. The lasers of two target frequencies of the same optical frequency comb can be locked to the resonant modes of the two groups of second microresonators, so that a stable frequency difference relationship is established between the lasers of the two target frequencies. The repetition frequency and the offset frequency of the carrier envelope of the optical frequency comb can be completely locked, thereby realizing a completely locked fully integrated optical frequency comb.

[0056] Based on the above embodiments, Figure 3 As shown, the first frequency stabilization system further includes a third tuning structure T1, which can control the stable position of the resonant mode of the second microresonator 43. The third tuning structure can be a thermoelectric cooler, which can be in contact with the substrate of the second microresonator 43 and is used to drive the thermoelectric power generation effect of the semiconductor thermocouple pair via direct current to accurately actively control the temperature of the second microresonator 43, thereby changing the stable position of the resonant mode of the second microresonator 43, that is, the position where the resonant frequency of the second microresonator 43 appears. This reduces the output range of the servo controller 47, reduces the control difficulty, and improves the control accuracy.

[0057] Based on the above embodiments, Figure 3As shown, the second frequency stabilization system further includes a fourth modulation structure T2, which can control the stable position of the resonant mode of the second microresonator 53. The third tuning structure can be a thermoelectric cooler, which can be in contact with the substrate of the second microresonator 53 and is used to drive the thermoelectric power generation effect of the semiconductor thermocouple pair via DC current to accurately actively control the temperature of the second microresonator 53, thereby changing the stable position of the resonant mode of the second microresonator 53, that is, the position where the resonant frequency of the second microresonator 53 appears. This reduces the output range of the servo controller 57, reduces the control difficulty, and improves the control accuracy.

[0058] High-resolution spectroscopy plays a vital role in molecular spectroscopy, chemical analysis, gas remote sensing, and other fields. Dual optical frequency comb technology offers revolutionary applications in high-resolution spectroscopy and precision ranging. Typically composed of two optical frequency combs with slightly different repetition rates, its core advantages lie in high resolution, high precision, wide spectral coverage, and rapid measurement capabilities. For precision ranging systems, poor stability in the repetition rates of the two optical frequency combs significantly reduces ranging accuracy. To achieve precise ranging results, a dual optical frequency comb system is required to generate two frequency-locked optical frequency combs.

[0059] Existing dual optical frequency comb systems typically require that the frequency difference between the target frequencies of the laser beams selected by the two optical frequency combs must be strictly constrained within the photodetector's response bandwidth, necessitating rigorous parameter matching and screening of the optical frequency combs. To address this issue, embodiments of the present invention also provide a frequency stabilization device that can achieve dual optical frequency comb locking.

[0060] Based on the above embodiments, Figure 4 As shown, the optical frequency comb unit 1 includes a first optical frequency comb unit 1-1 and a second optical frequency comb unit 1-2. The first optical frequency comb unit 1-1 includes a laser 1-11 and a first microresonator 1-12, and the second optical frequency comb unit 1-2 includes a laser 1-21 and a first microresonator 1-22.

[0061] The frequency stabilization system includes a third frequency stabilization system, a fourth frequency stabilization system and a wavelength division multiplexer 8. The third frequency stabilization system includes a filter 61, a photodetector 62, a phase shifter 63, a mixer 64 and a servo controller 65. The fourth frequency stabilization system includes a filter 71, a photodetector 72, a phase shifter 73, a mixer 74 and a servo controller 75.

[0062] The third frequency stabilization system and the fourth frequency stabilization system share the same phase modulator 32 and the same second microresonator 33; The filter 61 in the third frequency stabilization system is connected to the output waveguide of the photonic chip in the first optical frequency comb unit 1-1; The filter 71 in the fourth frequency stabilization system is connected to the output waveguide of the photonic chip in the second optical frequency comb unit 1-2; The input end of the wavelength division multiplexer 8 is connected to the output waveguide of the same second microresonator 33, the first output end is connected to the photodetector 62 in the third frequency stabilization system, and the second output end is connected to the photodetector 72 in the fourth frequency stabilization system; The servo controller 65 in the third frequency stabilization system is connected to the laser 1-11 in the first optical frequency comb unit 1-1, and is used to control the pump current of the laser 1-11 in the first optical frequency comb unit 1, so as to lock the laser light of the target frequency selected by the filter 61 in the third frequency stabilization system to the resonant mode of the same second microresonator 33; The servo controller 75 in the fourth frequency stabilization system is connected to the laser 1-21 in the second optical frequency comb unit 1-2, and is used to control the pump current of the laser 1-21 in 1-2, and lock the laser of the target frequency selected by the filter 71 in the fourth frequency stabilization system to the resonant mode of the same second microresonator 33.

[0063] Specifically, laser 1-11 can output single-frequency laser light A1, which can generate a set of optical frequency combs B1 after passing through first microresonator 1-12. Optical frequency comb B1 can select laser light C3 of the target frequency after passing through filter 61. Laser 1-21 can output single-frequency laser light A2, which can generate a set of optical frequency combs B2 after passing through first microresonator 1-22. Optical frequency comb B2 can select laser light C4 of the target frequency after passing through filter 71. Here, the free spectral ranges of filters 61 and 71 are different, ensuring that wavelength division multiplexer 8 can successfully separate optical signals of different wavelengths.

[0064] The laser light C3 of the target frequency and the laser light C4 of the target frequency are both phase-modulated by the same phase modulator 32 and pass through the same second microresonator 33 to obtain a modulated light beat signal containing two wavelengths.

[0065] The modulated optical beat signal is wavelength-separated by wavelength division multiplexer 8, resulting in a modulated optical beat signal corresponding to laser C3 of the target frequency and a modulated optical beat signal corresponding to laser C4 of the target frequency. Here, the modulated optical beat signals of two wavelengths are transmitted on a common fiber and then split into independent channels of different wavelengths by the wavelength division multiplexer. In this embodiment of the present invention, a dense wavelength division multiplexer (DWDM) can be used, with a wavelength spacing of 0.8 nm (corresponding to a frequency spacing of 100 GHz) or less (e.g., a frequency spacing of 50 GHz), which can support 80 to 160 independent channels.

[0066] The modulated light beat signal corresponding to the target frequency laser C3 is sequentially transmitted through the photodetector 62 and the mixer 64 to generate a third error signal reflecting the frequency deviation between the target frequency laser C3 and the resonant frequency of the same second microresonator 33. This third error signal is transmitted to the servo controller 65, which controls the pump current of the laser 1-11 based on the third error signal, adjusting the output frequency of the laser 1-11 and locking the target frequency laser C3 to the resonant mode of the second microresonator 33. In other words, the frequency of the target frequency laser C3 is locked to the resonant frequency of the same second microresonator 33.

[0067] Here, the RF signal generated by the oscillator 2 is phase-shifted by the phase shifter 63 to obtain a third phase-shifted signal, and the mixer 64 mixes the third phase-shifted signal with the third electrical signal output by the photodetector 62 to obtain a third error signal.

[0068] The modulated light beat signal corresponding to the target frequency laser C4 is sequentially transmitted through the photodetector 72 and the mixer 74 to generate a fourth error signal reflecting the frequency deviation between the target frequency laser C4 and the resonant frequency of the same second microresonator 33. This fourth error signal is transmitted to the servo controller 75, which controls the pump current of the laser 1-21 based on the fourth error signal, adjusting the output frequency of the laser 1-21 and locking the target frequency laser C4 to the resonant mode of the same second microresonator 33, that is, locking the frequency of the target frequency laser C4 to the resonant frequency of the same second microresonator 33.

[0069] Here, the RF signal generated by the oscillator 2 is phase-shifted by the phase shifter 73 to obtain a fourth phase-shifted signal, and the mixer 74 mixes the fourth phase-shifted signal with the fourth electrical signal output by the photodetector 72 to obtain a fourth error signal.

[0070] In the embodiment of the present invention, the lasers of two target frequencies in the two optical frequency combs generated by the first optical frequency comb unit 1-1 and the second optical frequency comb unit 1-2 can be locked to different modes of the same mode family emitted by the same second microresonator, thereby realizing a highly integrated dual-comb system. The two optical frequency combs establish a locking relationship with the same second microresonator, and since the second microresonator is regarded as a reference source with extremely stable frequency, it is considered that the two optical frequency combs also establish a locking relationship. Since the core optical devices used are similar to Figure 1 There is only a difference in quantity, so the frequency stabilization device still has the possibility of heterogeneous integration on the entire chip.

[0071] Traditional dual-optical frequency comb locking technology requires that the frequency difference between the target frequency lasers selected by the two optical frequency combs must be strictly constrained within the response bandwidth of the photodetector, thus requiring strict parameter matching and screening of the optical frequency combs. However, this frequency stabilization device, based on an innovative scheme of mode-pull coupling, dynamically adjusts the relative relationship between the resonant mode of the same second microresonator and the target frequency laser of the optical frequency comb. This overcomes the physical limitations of the detector bandwidth and achieves locking between any two optical frequency combs. This completely eliminates the stringent device parameter screening requirements of traditional technologies and provides a universal solution for the deployment of dual-comb systems in complex environments.

[0072] Based on the above embodiments, Figure 4 As shown, the frequency stabilization system further includes a fifth modulation structure T3, which can control the stable position of the resonant mode of the same second microresonator 33. The fifth tuning structure can be a thermoelectric cooler, which can be in contact with the substrate of the same second microresonator 33 and is used to drive the thermoelectric power generation effect of the semiconductor thermocouple pair via direct current to accurately actively control the temperature of the same second microresonator 33, thereby changing the stable position of the resonant mode of the same second microresonator 33, that is, the location where the resonant frequency of the same second microresonator 33 appears. This reduces the output range of the servo controller 65 and the servo controller 75, reduces the control difficulty, and improves the control accuracy.

[0073] Based on the above embodiment, the second microresonator can be an ultrastable microresonator, whose resonance frequency fluctuation can be less than or equal to a preset threshold, the free spectrum range can reach 100 MHz, and the quality factor Q can reach 10 5 Furthermore, an ultra-stable optical frequency comb can be output through the optical frequency comb stabilization device.

[0074] On the basis of the above embodiment, the second microresonator may include a spiral microresonator (spiral), a microring microresonator (ring), a finger microresonator (finger) and a disk microresonator (disk); The vortex line microresonator, the microring microresonator, the finger microresonator, and the disk microresonator are fabricated from different materials. For example, the microring and finger microresonators are typically made of silicon nitride, while the disk microresonator is typically made of alkali metal fluorides (magnesium fluoride, calcium fluoride), ULE, etc.

[0075] On the basis of the above embodiment, the laser is a distributed feedback semiconductor laser, and the active region of the distributed feedback semiconductor laser is integrated with a periodic grating structure.

[0076] Specifically, the periodic grating structure may be a Bragg grating, which utilizes Bragg reflection to selectively feed back a specific wavelength to achieve single longitudinal mode output.

[0077] Based on the above embodiment, metal electrodes may be integrated on the input waveguide of the photonic chip, the first microresonator and the output waveguide of the photonic chip by a metal lift-off process; The metal electrodes integrated on the input waveguide and output waveguide of the photonic chip are used to tune the light transmission phase of the waveguide section; The metal electrode integrated on the first microresonator is used to tune the free spectral range of the first microresonator.

[0078] In summary, the frequency stabilization device for the optical frequency comb provided in the embodiment of the present invention can perform multi-channel collaborative optimization of the optical frequency comb, so that the output optical frequency comb has ultra-high frequency stability and improved environmental robustness. The system-level packaging integration of the frequency stabilization device is relatively high, which effectively promotes the large-scale application of optical frequency combs.

[0079] like Figure 5 As shown, based on the above embodiments, an embodiment of the present invention further provides a method for stabilizing the frequency of an optical frequency comb implemented based on the frequency stabilization device of the optical frequency comb provided in each of the above embodiments, comprising: S1, generates an optical frequency comb based on the principle of self-injection locking; S2, selecting a laser of a target frequency from the optical frequency comb, and performing phase modulation on the laser of the target frequency based on a radio frequency signal to obtain a modulated signal; S3, inputting the modulated signal into the second microresonator to obtain an output optical signal of the second microresonator; S4, converting the output optical signal into an electrical signal, and inputting a phase-shifted signal obtained by phase-shifting the electrical signal and the radio frequency signal into a mixer to obtain an error signal reflecting the frequency deviation between the output frequency of the laser and the resonant frequency of the second microresonator; S5 , controlling the output frequency of the laser based on the error signal, and locking the laser light of the target frequency to the resonant mode of the second microresonator.

[0080] Specifically, in an embodiment of the present invention, step S1 can be implemented by an optical frequency comb unit, step S2 can be implemented by a filter combined with an oscillator and a phase modulator, step S3 can be implemented by a second microresonator, step S4 can be implemented by a photodetector, a phase shifter and a mixer, and step S5 can be implemented by a servo controller. For detailed implementation methods, please refer to the embodiments of the frequency stabilization device of the above-mentioned light beam frequency comb, which will not be repeated here.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A frequency stabilization device for an optical frequency comb, characterized in that: include: Optical frequency comb units, oscillators, and frequency stabilization systems; The optical frequency comb unit includes a laser and a first microresonator, wherein the first microresonator is etched on a photonic chip, and the laser is coupled to an input waveguide end face of the photonic chip; The frequency stabilization system includes a filter, a phase modulator, a second microresonator, a photodetector, a phase shifter, a mixer and a servo controller; The output waveguide of the photonic chip is connected to the filter, the phase modulator, the second microresonator, the photodetector, the mixer and the servo controller in sequence, the oscillator is connected to the phase modulator and the phase shifter respectively, the phase shifter is connected to the mixer, and the servo controller is connected to the laser; The optical frequency comb unit is used to generate an optical frequency comb based on the self-injection locking principle; The oscillator is used to generate a radio frequency signal; The filter is used to select a laser with a target frequency from the optical frequency comb; the laser with the target frequency passes through the phase modulator, the second microresonator, the photodetector, the mixer and the servo controller in sequence, thereby controlling the pump current of the laser and locking the laser with the target frequency to the resonant mode of the second microresonator.

2. The optical frequency comb frequency stabilization device according to claim 1, characterized in that: The frequency stabilization system includes a first frequency stabilization system and a second frequency stabilization system, wherein the first frequency stabilization system and the second frequency stabilization system each include a filter, a phase modulator, a second microresonator, a photodetector, a phase shifter, a mixer, and a servo controller; The filter in the first frequency stabilization system and the filter in the second frequency stabilization system are both connected to the output waveguide of the photonic chip; The phase modulator and phase shifter in the first frequency stabilization system, and the phase modulator and phase shifter in the second frequency stabilization system, are both connected to the oscillator; The servo controller in the first frequency stabilization system is connected to the laser and is used to control the pump current of the laser and lock the laser of the target frequency selected by the filter in the first frequency stabilization system to the resonant mode of the second microresonator in the first frequency stabilization system; The servo controller in the second frequency stabilization system is connected to the first tuning structure of the first microresonator, and is used to control the current of the first tuning structure to lock the laser of the target frequency selected by the filter in the second frequency stabilization system to the resonant mode of the second microresonator in the second frequency stabilization system.

3. The optical frequency comb frequency stabilization device according to claim 1, characterized in that: The optical frequency comb unit includes a first optical frequency comb unit and a second optical frequency comb unit, and the frequency stabilization system includes a third frequency stabilization system, a fourth frequency stabilization system, and a wavelength division multiplexer; the third frequency stabilization system and the fourth frequency stabilization system share the same phase modulator and the same second microresonator; The filter in the third frequency stabilization system is connected to the output end of the first optical frequency comb unit; The filter in the fourth frequency stabilization system is connected to the output end of the second optical frequency comb unit; The input end of the wavelength division multiplexer is connected to the output waveguide of the same second microresonator, the first output end is connected to the photodetector in the third frequency stabilization system, and the second output end is connected to the photodetector in the fourth frequency stabilization system; The servo controller in the third frequency stabilization system is connected to the laser in the first optical frequency comb unit, and is used to control the pump current of the laser in the first optical frequency comb unit, so as to lock the laser of the target frequency selected by the filter in the third frequency stabilization system to the resonant mode of the same second microresonator; The servo controller in the fourth frequency stabilization system is connected to the laser in the second optical frequency comb unit, and is used to control the pump current of the laser in the second optical frequency comb unit, so as to lock the laser of the target frequency selected by the filter in the fourth frequency stabilization system to the resonant mode of the same second microresonator.

4. The frequency stabilization device for an optical frequency comb according to any one of claims 1 to 3, characterized in that: The resonance frequency fluctuation of the second microresonator is less than or equal to a preset threshold.

5. The frequency stabilization device for an optical frequency comb according to any one of claims 1 to 3, characterized in that: The second microresonator may include a vortex line structure microresonator, a microring structure microresonator, a finger structure microresonator and a disk structure microresonator; The vortex line structure microresonator, the microring structure microresonator, the finger structure microresonator and the disk structure microresonator are prepared based on different materials.

6. The frequency stabilization device for an optical frequency comb according to any one of claims 1 to 3, characterized in that: The laser includes a laser chip, and the filter includes a microring filter.

7. The frequency stabilization device for an optical frequency comb according to any one of claims 1 to 3, characterized in that: The optical frequency comb unit, the filter, the phase modulator, the second microresonator and the photodetector are integrated on a chip, and the phase shifter, the mixer and the servo controller are integrated on an electronic control board.

8. The frequency stabilization device for an optical frequency comb according to any one of claims 1 to 3, characterized in that: Metal electrodes are integrated on the input waveguide of the photonic chip, the first microresonator and the output waveguide of the photonic chip; The metal electrodes integrated on the input waveguide and output waveguide of the photonic chip are used to tune the light transmission phase of the waveguide section; The metal electrode integrated on the first microresonator is used to tune the free spectral range of the first microresonator.

9. The frequency stabilization device for an optical frequency comb according to any one of claims 1 to 3, characterized in that: The frequency stabilization system further includes a second modulation structure of the second micro-modulator; The second modulation structure is used to control a stable position of a resonant mode of the second microresonator.

10. A method for stabilizing an optical frequency comb based on the optical frequency comb stabilization device according to any one of claims 1 to 9, characterized in that: include: Generate optical frequency comb based on the principle of self-injection locking; Selecting a laser of a target frequency from the optical frequency comb, and performing phase modulation on the laser of the target frequency based on a radio frequency signal to obtain a modulated signal; inputting the modulated signal into a second microresonator to obtain an output optical signal of the second microresonator; Converting the output optical signal into an electrical signal, and inputting a phase-shifted signal obtained by phase-shifting the electrical signal and the radio frequency signal into a mixer to obtain an error signal reflecting the frequency deviation between the output frequency of the laser and the resonant frequency of the second microresonator; Based on the error signal, the output frequency of the laser is controlled to lock the laser light of the target frequency to the resonant mode of the second microresonator.

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