Time-programmable microcavity optical comb and its application system

Abstract

This application provides a time-programmable microcavity optical comb and its application system. The time-programmable microcavity optical comb includes: a first laser for generating pump light; an optical resonant cavity, the first laser being connected to the optical resonant cavity to couple the pump light with the optical resonant cavity, forming an optical comb within the optical resonant cavity using a pump cavity film, the optical comb including multiple comb teeth; and an injection modulation module for phase modulation of the injected laser and injecting the phase-modulated injected laser into the optical resonant cavity, achieving frequency locking and phase synchronization of the nth comb tooth, thereby controlling the temporal position of the optical comb pulse, wherein the frequency of the injected laser is within the locked bandwidth of the nth comb tooth. The first laser and the optical resonant cavity work together to generate a microcavity optical comb, which has advantages such as high measurement speed, easy chip integration, and low power consumption, and the injection modulation module can quickly and efficiently control the temporal position of the optical comb pulse.

Description

Technical Field

[0001] This application relates to the field of optical frequency comb technology, and in particular to a time-programmable microcavity optical comb and its application system. Background Technology

[0002] High-precision absolute distance measurement has significant strategic importance in fields such as integrated circuit lithography, satellite formation, synthetic aperture radar, and high-end equipment manufacturing. While traditional laser interferometers can achieve sub-nanometer precision displacement measurement, they are essentially incremental measurements, suffering from inherent drawbacks such as error accumulation, difficulty in characterizing distance jumps, and reliance on long guide rails. Optical frequency combs (optical combs) can provide a series of equally spaced, phase-coherent comb teeth in the frequency domain, corresponding to a periodic sequence of ultrashort optical pulses in the time domain. This allows for the determination of absolute distance from a single point, opening up new opportunities for distance metrology.

[0003] In related technologies, research on optical comb ranging mainly focuses on fiber optic combs. The repetition rate (RF) of fiber optic combs is typically in the hundreds of MHz range. Limited by the small RF difference, the measurement speed is generally difficult to exceed tens of kHz. Furthermore, fiber optic combs are bulky and cannot be integrated into chips. Microcavity optical combs, with their high RF characteristics, can achieve measurement refresh rates in the hundreds of MHz range, offering high measurement speeds and advantages such as chip integration and low power consumption. However, microcavity optical combs lack time-domain control capabilities; current control of microcavity optical combs is mainly concentrated in the frequency domain, lacking the ability to control them in the time domain. Summary of the Invention

[0004] This application provides a time-programmable microcavity optical comb and its application system to solve at least some of the problems in the related technologies.

[0005] This application provides a time-programmable microcavity optical comb, comprising: The first laser is used to generate pump light; An optical resonant cavity is provided, wherein the first laser is connected to the optical resonant cavity to couple the pump light with the optical resonant cavity, and an optical comb is formed in the pump cavity film within the optical resonant cavity, the optical comb comprising multiple comb teeth; An injection modulation module is used to perform phase modulation on the injected laser and inject the phase-modulated injected laser into the optical resonant cavity to achieve frequency locking and phase synchronization of the nth comb tooth, thereby controlling the time domain position of the optical comb pulse, wherein the frequency of the injected laser is located within the locking bandwidth of the nth comb tooth.

[0006] Furthermore, the injection modulation module includes: A second laser is used to generate the injected laser; A phase modulation unit is used to perform phase modulation on the injected laser; An injection coupling unit is used to inject phase-modulated injection laser light into the optical resonant cavity.

[0007] Furthermore, the phase modulation unit includes an electro-optic phase modulator; and / or The phase modulation unit is used to apply a sinusoidal modulation signal to the injected laser to perform phase modulation on the injected laser.

[0008] Furthermore, the optical resonant cavity is an optical microcavity, which includes a microcavity integrated into the substrate and a crystal whispering-gallery mode microcavity; the optical resonant cavity is micro-ring type or racetrack type; or The optical resonant cavity is an optical fiber resonant cavity.

[0009] Furthermore, the optical comb also includes a frequency scanning module, which is connected to the first laser and used to tune the pump light to achieve frequency scanning of the pump light; the frequency scanning module includes: The first signal generator is used to generate a changing voltage signal; A voltage-controlled oscillator, connected to the first signal generator, is used to output a single-frequency radio frequency signal whose frequency varies with the voltage signal; A frequency modulator is connected to the voltage-controlled oscillator and the first laser. The frequency modulator operates in carrier-suppressed single-sideband modulation mode and is used to receive the pump light from the first laser. The single-frequency radio frequency signal output by the voltage-controlled oscillator is used as the modulation drive to realize the frequency scanning of the pump light.

[0010] Furthermore, the optical comb also includes an injection locking monitoring module, which includes: The first filter, connected to the optical resonant cavity, is used to output the signal of the nth comb tooth; A first detector, connected to the first filter, is used to observe the beat frequency signal between the nth comb tooth and the injected laser, so as to adjust the frequency of the injected laser according to the beat frequency signal, so that the frequency of the injected laser is located near the center of the locked bandwidth of the nth comb tooth.

[0011] Furthermore, the optical comb also includes an optical comb motion trajectory reconstruction module, which includes: The second filter, connected to the optical resonant cavity, is used to output the signal of the kth comb tooth, where k is not equal to n and 0; The third laser is used to output continuous laser. The third laser is connected to the second filter. The continuous laser and the signal of the kth comb tooth are heterodyne beat frequency to generate a heterodyne beat frequency signal. The second detector, connected to both the second filter and the third laser, is used to observe the heterodyne beat frequency signal in order to reconstruct the soliton motion trajectory based on the heterodyne beat frequency signal and the sideband intensity theory.

[0012] Another aspect of this application provides an application system for a time-programmable microcavity optical comb, comprising: Time-programmable microcavity optical comb.

[0013] Furthermore, the application system is a distance measurement system, which further includes: The beam splitting and frequency shifting module is connected to the optical comb and is used to split the output signal of the optical comb into two signals and shift the frequency of one of the signals. The delay line module, connected to the beam splitter frequency shifter module, is used to introduce a set delay into one of the signals so that the two signals generate a relative delay scan. The beam combining and detection module is used to combine two signals and detect interference signals. A signal processing module, connected to the beam combining detection module, is used to determine the distance based on the interference signal.

[0014] Furthermore, the set delay ΔT introduced by the delay line module is related to the phase modulation period T. m Satisfying ΔT≈T m / 2.

[0015] Furthermore, the signal processing module includes a resampling module and a multiheterodyne interferometry module, wherein the resampling module is connected between the beam combining detection module and the multiheterodyne interferometry module; The resampling module is used to convert the nonlinear delayed scan in the interference signal into a linear delayed scan; the multiheterodyne interferometry module is used to perform Fourier transform on the linear delayed scan interference signal, extract the intensity and phase information of the interference signal, and generate a radio spectrum that can be used for distance analysis.

[0016] Furthermore, the resampling module includes a positioning unit, a linear fitting unit, a Fourier transform unit, an offset removal unit, a linear correction unit, and a stitching unit connected in sequence. The positioning unit is used to: locate the envelope peak of the acquired interference signal, and take the midpoint between adjacent peak times as the scanning direction reversal point; The linear fitting unit is used to: perform linear fitting between the midpoint index and the corresponding time, and calculate the phase of the sinusoidal scan based on the intercept obtained from the fitting.

[0017] The Fourier transform unit is used to: perform a Fourier transform on the entire interference signal to obtain a spectrum containing the frequency-shifted carrier; The offset removal unit is used to: shift the positive spectrum downward by the frequency offset introduced by the beam splitting frequency shifting module, discard the negative spectrum, and then obtain a carrier-free interference pulse sequence through inverse Fourier transform; The linear correction unit is used to: divide the carrierless interference pulse sequence into a forward scanning segment and a backward scanning segment according to the scanning direction, and resample the nonlinear delay in each segment according to the phase of the sinusoidal scan to correct it into a linear time delay; The splicing unit is used to splice the same-direction scanning segments of the interference pulse sequence corrected to linear time delay, and then perform Fourier transform to obtain a radiation spectrum with a hyperbolic secant envelope.

[0018] Furthermore, the distance measurement system also includes a beam splitting module, a reference mirror, and a measurement mirror. The beam splitting module is connected to the beam splitting and frequency shifting module and is used to split the first of the two signals into a reference signal and a measurement signal. The reference mirror is used to make the reference signal return and interfere with the second of the two signals to obtain a reference interference signal. The measurement mirror is used to make the measurement signal return and interfere with the second signal to obtain a measurement interference signal. The signal processing module is used to determine the distance based on the reference interference signal and the measurement interference signal.

[0019] Furthermore, the distance measurement system also includes a polarization multiplexed spatial optical path, in which the reference path signal and the measurement path signal are transmitted in orthogonal polarization states.

[0020] Furthermore, the distance measurement system also includes a spatial dispersion optical path, which includes a diffraction grating and a focusing lens; the diffraction grating is located at the front focal point of the focusing lens, and the sample to be measured is located at the rear focal point of the focusing lens; the diffraction grating is used to disperse the comb teeth of different frequencies of the optical comb at different angles, and the focusing lens is used to focus the dispersed comb teeth to different spatial positions on the surface of the sample to be measured, forming multiple independent measurement channels for parallel distance measurement.

[0021] This application provides a time-programmable microcavity optical comb and its application system. The time-programmable microcavity optical comb includes a first laser, an optical resonant cavity, and an injection modulation module. The first laser and the optical resonant cavity work together to generate the microcavity optical comb. The microcavity optical comb has advantages such as high measurement speed, easy chip integration, and low power consumption. The injection modulation module is used to perform phase modulation on the injected laser and inject the phase-modulated laser into the optical resonant cavity to achieve frequency locking and phase synchronization of the nth comb tooth, thereby controlling the time-domain position of the optical comb pulse. Compared with related technologies, where fiber optic combs rely on electronic phase-locked loops and microwave phase shifters to control the pulse position, resulting in overall complexity and slow pulse movement speed, the injection modulation module of the optical comb provided in this application not only enables time-programmable control of the microcavity optical comb but also significantly improves the speed of optical comb time control. Attached Figure Description

[0022] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0023] Figure 1 This is a schematic diagram of the structure of a time-programmable microcavity optical comb according to one embodiment of this application; Figure 2 for Figure 1 The diagram shown is a structural schematic of the injection modulation module. Figure 3 This is a schematic diagram of the structure of a time-programmable microcavity optical comb according to another embodiment of this application; Figure 4 This is a schematic diagram of the sideband strength theory; Figure 5 This is a schematic diagram of the structure of a distance measurement system provided in one embodiment of this application; Figure 6 This is the original diagram of the time-domain interference signal; Figure 7 The RF power spectrum and phase spectrum after resampling; Figure 8 This is a schematic diagram of the structure of a distance measurement system provided in one embodiment of this application; Figure 9 This is a schematic diagram of the structure of a distance measurement system provided in one embodiment of this application.

[0024] Figure label: The system comprises: a time-programmable microcavity optical comb 1, a first laser 10, an optical resonant cavity 20, an injection modulation module 30, a second laser 31, a phase modulation unit 32, a second signal generator 321, an RF amplifier 322, a phase modulator 323, an injection coupling unit 33, a frequency scanning module 40, a first signal generator 41, a voltage-controlled oscillator 42, a frequency modulator 43, an fiber amplifier 44, an injection lock monitoring module 50, a first filter 51, a first detector 52, a first oscilloscope 53, a soliton motion trajectory reconstruction module 60, a second filter 61, a third laser 62, a second detector 63, a distance measurement system 2, a beam splitting and frequency shifting module 21, and a delay line module 22. Beam combining and detection module 23, signal processing module 24, long delay line 221, adjustable delay line 222, resampling module 25, multi-heterodyne interferometry module 26, positioning unit 251, linear fitting unit 252, Fourier transform unit 253, offset removal unit 254, linear correction unit 255, splicing unit 256, beam splitting module 261, reference mirror 262, measuring mirror 263, polarization multiplexing spatial optical path 27, collimator 271, beam splitter 272, waveplate 273, third detector 264, second oscilloscope 265, spatial dispersive optical path 28, diffraction grating 281, focusing lens 282, semiconductor optical amplifier 283, sample under test 284. Detailed Implementation

[0025] This application provides a time-programmable microcavity optical comb and its application system. The time-programmable microcavity optical comb and its application system of this application will be described in detail below with reference to the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0026] High-precision absolute distance measurement has significant strategic importance in fields such as integrated circuit lithography, satellite formation, synthetic aperture radar, and high-end equipment manufacturing. While traditional laser interferometers can achieve sub-nanometer precision displacement measurement, they are essentially incremental measurements, suffering from inherent drawbacks such as error accumulation, difficulty in characterizing distance jumps, and reliance on long guide rails. Optical combs, on the other hand, can achieve absolute distance measurement, obtaining absolute distance from a single point without relying on incremental distance accumulation, thus opening up new opportunities for distance metrology.

[0027] Dual-comb ranging (DCR) is a core technology for achieving high-speed, high-precision absolute ranging (Nature Photonics, 3, 351-356 (2009)). It maps the optical frequency comb teeth to the radio frequency domain by using multiple heterodyne beat frequencies between two optical combs with slightly different repetition rates. Then, the phase and intensity information of the optical comb are inverted by measuring the radio frequency comb teeth, and finally, the time delay corresponding to the distance to be measured is obtained through linear fitting of the phase spectrum. Despite the enormous potential of dual-comb ranging, its development still faces the following challenges: First, the system's measurement performance and integration need improvement. Current DCR research focuses on femtosecond fiber optic combs, whose repetition rates are typically in the hundreds of MHz range. Limited by the small repetition rate difference, measurement speeds generally cannot exceed tens of kHz. Microcavity combs, with their high repetition rate characteristics, can achieve measurement refresh rates in the hundreds of MHz range, offering high measurement speeds and advantages such as chip integration and low power consumption. However, the highest reported accuracy of microcavity comb DCR to date is only about 12 nm, which is still incomparable to fiber optic comb DCR.

[0028] Secondly, the system complexity needs to be further reduced. Dual-comb interferometry requires high mutual coherence between the two combs, which usually requires locking with an ultra-narrow linewidth laser, resulting in a large and expensive system. Based on a counter-propagating (CP) soliton comb generated by a bidirectional pumped single microcavity (Nature Photonics, 11, 560-564 (2017)), the repetition frequency difference and offset frequency difference can be stabilized spontaneously by vernier frequency locking without external phase locking, which significantly simplifies the system. However, the rhythmic interaction between solitons in this scheme introduces femtosecond-level relative timing jitter, leading to systematic measurement bias (Nature Communications, 16, 6853 (2025)).

[0029] Finally, microcavity optical combs lack time-domain control capabilities. Current control of microcavity optical combs mainly focuses on the frequency domain, such as adjusting the cavity length through piezoelectric or electro-optic effects to lock the repetition rate, or locking and stabilizing the frequency of a single comb tooth through injection, lacking flexible control over the soliton pulse timing parameters. In contrast, this time-domain control capability has been demonstrated in time-programmable frequency combs (TPFCs) (Nature, 610, 667-673 (2022)), pushing ranging sensitivity to the quantum limit; however, it relies on electrical phase-locking and microwave phase shifting, resulting in complex structures, limited adjustment speed, and difficulty in integration. Therefore, there is an urgent need to develop a novel optical comb control and ranging technology that combines high precision, high speed, and high integration.

[0030] Based on this, this application provides a time-programmable microcavity optical comb and its application system.

[0031] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of the optical comb 1 shown in one embodiment of this application. Figure 1 In the embodiment shown, the time-programmable microcavity optical comb 1 includes a first laser, an optical resonant cavity 20, and an injection modulation module 30.

[0032] The first laser 10 is used to generate pump light, serving as the sole energy injection source for the entire system.

[0033] An optical resonant cavity 20 is connected to a first laser 10 so that the pump light is coupled to the optical resonant cavity 20. An optical comb 1 is formed in the pump cavity film within the optical resonant cavity 20. The optical comb 1 includes multiple comb teeth.

[0034] The injection modulation module 30 is used to perform phase modulation on the injected laser and inject the phase-modulated injected laser into the optical resonant cavity 20 to achieve frequency locking and phase synchronization of the nth comb tooth, thereby controlling the time domain position of the optical comb pulse. The frequency of the injected laser is located within the locking bandwidth of the nth comb tooth.

[0035] Specifically, the optical resonant cavity 20 is coupled to the first laser 10, receives pump light, and pumps the cavity film through its high Q value and nonlinear effects of the material, such as the Kerr effect and four-wave mixing, forming a stable soliton optical comb within the cavity. A soliton is a coherent optical comb; all optical combs mentioned in this application are coherent optical combs. This soliton optical comb exhibits a spectrum containing multiple discrete comb teeth in the frequency domain.

[0036] The injection modulation module 30 is responsible for generating the injection laser, phase modulating the injection laser, and injecting the phase-modulated injection laser into the optical resonant cavity 20. The frequency of the injection laser is precisely tuned to within the locking bandwidth of the nth comb tooth in the soliton optical comb. Through the injection locking physical mechanism, the injection laser captures the nth comb tooth, forcing its frequency and phase to be synchronized with the injection laser. Based on this, the phase change caused by applying phase modulation to the injection laser will be transmitted to the nth comb tooth in real time without distortion through this locking link.

[0037] Based on the time-frequency Fourier transform relationship, the phase slope determined by the 0th comb tooth (pump light) and the nth comb tooth (locked comb tooth) can be modulated to directly control the position of the soliton pulse in the time domain, thus enabling time-programmable optical comb 1. Specifically, based on the properties of the Fourier transform, a linear phase change in the frequency domain corresponds to a pulse shift in the time domain. For optical comb 1, the phase of two comb teeth will determine the corresponding phase shift slope, thereby determining the pulse position. However, if the frequency of one of the comb teeth is modulated, the spectral phase slope can be changed, thereby controlling the pulse position. The modulation process of a microcavity optical comb can be represented as follows: in, The phase of the nth comb tooth relative to the pump. For the pump phase, For repetition frequency, For the observation time. This control method utilizes the coherent pumping characteristics of a microcavity optical comb, determining one of the two frequencies used to set the phase slope as the pumping frequency of the microcavity optical comb; therefore, as long as the observation time is achieved... Modulation can be used to control microcavity solitons.

[0038] Please refer to Figure 2 , Figure 2 for Figure 1 The diagram shows the structure of the injection modulation module 30. Figure 2 In the illustrated embodiment, the injection modulation module 30 includes: The second laser 31 is used to generate the injected laser. The second laser 31 is a tunable continuous laser, and its output frequency can be finely adjusted within a certain spectral range.

[0039] The phase modulation unit 32 is used to perform phase modulation on the injected laser. Specifically, the phase modulation unit 32 is connected to the second laser 31, receives the injected laser output from the second laser 31, and applies the required modulation waveform to the injected laser to perform phase modulation.

[0040] The injection coupling unit 33 is used to inject the phase-modulated injection laser into the optical resonant cavity 20. Specifically, the injection coupling unit 33 connects the output end of the phase modulation unit 32 and the optical resonant cavity 20, and is used to efficiently input and couple the phase-modulated injection laser into the optical resonant cavity 20, so that it can interact with the existing soliton optical comb field in the cavity through injection locking.

[0041] The injection coupling unit 33 can be an evanescent wave coupler made of tapered optical fiber, or it can be an on-chip integrated end face coupler. This application does not limit this.

[0042] The injection modulation module 30 divides the three core sub-functions of controlling light generation, phase programming, and intracavity injection locking into three independent units. This modular architecture facilitates the independent design, optimization, and replacement of each unit in engineering implementation. For example, phase modulation units 32 with different bandwidths can be selected according to the required modulation speed, or different injection coupling unit schemes 33, such as tapered fiber coupling or on-chip waveguide coupling, can be selected according to the integration requirements.

[0043] Furthermore, the phase modulation unit 32 includes an electro-optic phase modulator 323. The electro-optic phase modulator 323 utilizes the Pockels effect of materials, exhibiting extremely fast response speeds and capable of achieving high-frequency phase modulation up to tens of GHz. It is particularly suitable for applications requiring extremely high modulation speeds, such as high-speed lidar or high-frequency vibration measurement. In this scheme, the temporal shift speed of the soliton pulse can be flexibly set by adjusting the amplitude and frequency of the RF modulation signal applied to the electro-optic phase modulator 323, and its shift speed is significantly higher than that of existing TPFC schemes based on electrical phase-locked loops. The phase modulation unit 32 can also be one or more combinations of devices capable of changing the optical path or refractive index, such as a piezoelectric modulator, a thermo-optically tuned delay line, or a piezoelectric ceramic-driven fiber stretcher and free-space optical delay line. A piezoelectric ceramic-driven fiber stretcher or free-space optical delay line changes the geometric path of light propagation by physically stretching the fiber or moving a reflector, thus effectively introducing a phase change. This is suitable for scenarios requiring large modulation amplitudes but not high modulation frequency requirements. This application does not impose any limitations. In this way, multiple physical implementation paths are provided for the phase modulation unit 32, ranging from high speed to low speed and from on-chip to fiber, covering different application requirements and technology maturity.

[0044] In some embodiments, the phase modulation unit 32 is used to apply a sinusoidal modulation signal to the injected laser to modulate its phase. In other embodiments, the modulation waveform applied by the phase modulation unit 32 to the injected laser is not limited to a sine wave, but can also be a triangular wave, a square wave, a ramp, or any combination of these basic waveforms, or even an arbitrarily programmed waveform. Applicable modulation waveforms include triangular waves, square waves, ramps, etc. Thus, not only can the soliton pulse undergo sinusoidal simple harmonic oscillation, but it can also be driven to perform linear scanning, step transitions, or move along arbitrarily complex trajectories. This lays the technical foundation for subsequent applications of the optical comb 1 in scenarios requiring complex timing control, such as coherent multidimensional spectral measurements, and greatly broadens its application scope.

[0045] In some embodiments, the optical resonant cavity 20 is an optical microcavity, which includes a microcavity integrated on a substrate and a microcavity in crystal whispering mode, and the optical resonant cavity is micro-ring type or racetrack type; in other embodiments, the optical resonant cavity 20 is an optical fiber resonant cavity.

[0046] Thus, the optical resonator 20 can be implemented using either of two technical approaches: one is a microcavity integrated into the substrate, and the other is a discrete fiber optic resonator. The microcavity integrated into the substrate can be a microring resonator or a racetrack-shaped resonator fabricated on a nonlinear optical material platform such as silicon nitride, silicon dioxide, lithium niobate, lithium tantalate, silicon carbide, or aluminum nitride using micro- and nano-fabrication processes (such as photolithography and etching). These materials all possess the high Q-value and third-order optical nonlinearity necessary to support the stable formation of soliton states. The microcavity in the crystal whispering-gallery mode can be a magnesium fluoride (MgF2) cavity.

[0047] An optical fiber resonator is formed by connecting a section of ordinary single-mode passive optical fiber into a ring via an optical fiber coupler. Like optical microcavities, this passive fiber ring also serves as a container for accommodating and maintaining nonlinear optical effects, requiring an external pump laser to drive the generation of a soliton optical comb within it.

[0048] Please refer to Figure 3 , Figure 3 This is a schematic diagram of the structure of an optical comb according to another embodiment of this application. Figure 3 In the illustrated embodiment, to stably excite the single soliton state, the optical comb 1 further includes a frequency scanning module 40. The frequency scanning module 40 is connected to the first laser 10 and is used to tune the pump light, achieving frequency scanning of the pump light. Specifically, it is used to perform rapid and controllable scanning tuning of the pump light frequency to overcome the resonant frequency drift caused by the inherent thermo-optical effect of the microcavity, guiding the intracavity optical field smoothly from a chaotic state to a stable single soliton state.

[0049] Frequency scanning module 40 includes: The first signal generator 41 is used to generate a changing voltage signal, which is a voltage signal that changes rapidly over time.

[0050] The voltage-controlled oscillator 42 is connected to the first signal generator 41 and is used to output a single-frequency radio frequency signal whose frequency varies with the voltage signal. The frequency modulator 43 is connected to the voltage-controlled oscillator 42 and the first laser 10. The frequency modulator 43 operates in carrier-suppressed single-sideband modulation mode to receive the pump light from the first laser 10 and uses the single-frequency radio frequency signal output by the voltage-controlled oscillator 42 as the modulation drive to realize the frequency scanning of the pump light.

[0051] Stable generation of a single soliton optical comb is a physical prerequisite for achieving programmable control and high-precision measurement throughout the entire process. This fast frequency scanning module 40 provides an electronically controllable implementation scheme with flexibly adjustable scanning parameters such as speed and range. An IQ modulator is used as the frequency modulator 43. The IQ modulator operates in carrier-suppressed single-sideband modulation mode, enabling efficient and clean frequency scanning without redundant sidebands, a key enabling technology for stable single soliton excitation. In this embodiment, the frequency scanning module 40 also includes a frequency fiber amplifier 44, connected between the frequency modulator 43 and the optical resonant cavity 20, for amplifying the pump light modulated by the frequency modulator 43.

[0052] Besides generating solitons through the frequency scanning module 40, solitons can also be stably generated using methods such as "power kick," dual pumping, thermal tuning, and self-injection locking. This application does not limit the scope of solitons in this regard.

[0053] In this embodiment, the pump light of the first laser 10 is 1536.6 nm, and a high-Q silicon nitride optical microcavity with a free spectral range (FSR) of approximately 100 GHz is used to generate a soliton comb. Its intrinsic Q-value and loaded Q-value are 8.6 M and 2.9 M, respectively, and the on-chip pump power is approximately 200 mW. After the soliton is stabilized, the second laser 31 injects an injection laser at a wavelength of approximately 1562.2 nm, ensuring its frequency falls within the locked bandwidth (approximately 100 MHz) of the nth comb tooth (e.g., n = -32). The on-chip power of the injected laser is typically adjusted between 1.5 and 2.5 mW.

[0054] After injection locking, the phase modulation unit 32 is used to phase modulate the second laser beam generated by the second laser 31 to achieve time control of the microcavity soliton pulse. In this embodiment, the phase modulation unit 32 includes a second signal generator 321, an RF amplifier 322, and a phase modulator 323. The RF amplifier 322 is connected to both the second signal generator 321 and the phase modulator 323. The second signal generator 321 outputs a 5 MHz sine wave, which is amplified by the RF amplifier 322 to a 33 dBm RF power to drive the phase modulator 323. (approximately 3.7 V), producing amplitude It is 12.2 rad.

[0055] To monitor the injection lock status in real time and ensure robust system operation, this time-programmable microcavity optical comb 1 also includes an injection lock monitoring module 50. The injection lock monitoring module 50 includes: The first filter 51 is connected to the optical resonant cavity 20 and is used to output the signal of the nth comb tooth. Specifically, the first filter 51 is used to optically bandpass filter out the optical signal of the locked nth comb tooth from the broadband soliton optical comb. The first detector 52, connected to the first filter 51, receives the signal from the nth comb tooth output by the first filter 51, and also receives a small portion of the injected laser as a reference beam. This detector is used to observe the heterodyne beat frequency signal between the nth comb tooth and the injected laser in real time. The frequency of the injected laser is adjusted according to the beat frequency signal so that its frequency is near the center of the locking bandwidth of the nth comb tooth. In this embodiment, the injection locking monitoring module 50 also includes a first oscilloscope 53, connected to the first detector 52. During operation, the experimenter can observe the beat frequency signal displayed on the first detector 52 through the first oscilloscope 53 while finely adjusting the wavelength of the second laser 31. The beat frequency changes from high to low; when it decreases and stabilizes within the injection locking bandwidth, the beat frequency signal disappears, indicating successful injection locking. Further fine-tuning can bring the injected laser frequency near the center of the locking bandwidth to ensure the most stable locking state, making it less susceptible to environmental influences and loss of lock.

[0056] By setting up the injection lock monitoring module 50, the operator is provided with an intuitive injection lock status indicator, transforming the invisible optical frequency lock process into an observable and identifiable radio frequency signal change process. This greatly facilitates system debugging and long-term stable operation, and is an indispensable auxiliary support module for achieving robust time-programmable control.

[0057] To enable online and quantitative characterization and calibration of the temporal motion of soliton pulses under time-programmable control, this time-programmable microcavity optical comb 1 also includes a soliton motion trajectory reconstruction module 60. This module is based on an important physical principle: sideband strength theory. Figure 4 This diagram illustrates the sideband intensity theory. When a soliton pulse exhibits periodic motion in the time domain (e.g., due to sinusoidal modulation of the nth comb tooth), each comb tooth 1 will symmetrically generate a series of equally spaced sidebands on both sides of the original main peak in the frequency domain. The ratio r(aA) of the complex amplitude between these sidebands and the main comb tooth satisfies the following formula with respect to the amplitude of the soliton pulse's motion in the time domain: Where 'a' represents the tooth number of the optical comb 1, and 'A' represents the A-th order sideband corresponding to the soliton motion. Let A be the motion amplitude of the A-th sideband. This represents the phase of the A-th order sideband. Based on this principle, by measuring the beat frequency signal between one tooth of optical comb 1 and another continuous laser beam, the motion amplitude and phase of the A-th order sideband are calculated according to the ratio of the complex amplitudes. The motion trajectory of the soliton optical comb is then reconstructed.

[0058] The optical comb 1 motion trajectory reconstruction module includes: The second filter 61, connected to the optical resonant cavity 20, is used to output the signal of the k-th comb tooth, where k is not equal to n and 0; it excludes the 0th (pump anchor) and the nth (modulation anchor) teeth, ensuring that the selected comb tooth is a free comb tooth whose changes can faithfully reflect the overall motion of the soliton without being directly disturbed by a single externally injected signal.

[0059] The third laser 62 is used to output continuous laser. The third laser 62 is connected to the second filter 61. The continuous laser and the signal of the kth comb tooth are heterodyne beat frequency to generate a heterodyne beat frequency signal. The second detector 63, connected to both the second filter 61 and the third laser 62, is used to observe the heterodyne beat frequency signal to reconstruct the soliton's trajectory based on the heterodyne beat frequency signal and sideband intensity theory. The soliton is a correlated state optical comb. By analyzing the complex amplitude ratios of each sideband to the main beat frequency signal on the beat frequency spectrum recorded by the second detector 63, the amplitude and phase of the soliton's time-domain motion (i.e., its trajectory) can be deduced based on sideband intensity theory. By applying different driving powers or different waveforms (triangular wave, square wave, ramp, etc.) and observing whether the reconstructed trajectory matches the expectation, the modulation performance of the time-programmable optical comb 1 can be comprehensively quantitatively characterized and calibrated.

[0060] exist Figure 3 In the illustrated embodiment, the first filter 51 and the second filter 61 are two independent filters. In some other embodiments, the first filter 51 and the second filter 61 may be the same filter, and this application does not impose any limitations on this. Figure 3 In the illustrated embodiment, the first oscilloscope 53 is connected not only to the first detector 52 but also to the second detector 63. Thus, it can display not only the signal detected by the first detector 52 but also the signal detected by the second detector 63. In some other embodiments, the soliton motion trajectory reconstruction module 60 may also include a separate oscilloscope connected to the second detector 63 to display the signal detected by the second detector 63. This application does not impose any limitations on this.

[0061] The optical comb 1 motion trajectory reconstruction module utilizes a bystander comb tooth as an ultrafast probe for the overall motion of solitons to construct a non-invasive, highly sensitive online characterization system. By choosing k≠n, background interference from direct modulation signals is completely eliminated, ensuring that the measurement results are entirely derived from the true physical response of the solitons. This method itself is also an independent and widely applicable technique that can be used to study and characterize any ultrafast optical system that can generate periodic pulses, including but not limited to the time-domain modulation process of optical pulses in counter-propagating microcavity soliton pairs, vibrational soliton molecules, mode-locked lasers, and bidirectional mode-locked lasers.

[0062] This application also provides an application system for a time-programmable microcavity optical comb, the application system including the time-programmable microcavity optical comb. In some embodiments, the application system is a distance measurement system that can be used for distance measurement.

[0063] Please refer to Figure 5 , Figure 5 This is a schematic diagram of the structure of a distance measurement system 2 provided in one embodiment of this application. Figure 5 In the embodiment shown, the distance measurement system 2 achieves the equivalent dual-comb measurement effect that traditional solutions require two independent lasers and a precision phase-locked loop electronics system using only a single optical comb 1.

[0064] Distance measurement system 2 includes: A time-programmable microcavity optical comb 1 serves as the sole light source for generating optical pulse sequences.

[0065] The beam splitter and frequency shifter module 21, connected to the optical comb 1, is used to split the output signal of the optical comb 1 into two signals and shift the frequency of one of the signals. The beam splitter and frequency shifter module 21 has two functions: first, to split the beam output from the optical comb 1 into a first path and a second path; second, after splitting, to optically shift the frequency of one of the paths, i.e., to add a fixed frequency offset. The purpose of this is to assign a unique and identifiable frequency label to this path of light. In this embodiment, the beam splitter and frequency shifter module 21 shifts the frequency of one path by 350 MHz to avoid spectral aliasing.

[0066] Delay line module 22, connected to beam splitter / frequency shifter module 21, is used to introduce a set delay into another signal, so that the two signals produce a relative delayed scan; specifically, delay line module 22 is used to introduce a fixed time delay ΔT into this optical path. If the microcavity optical comb has... The delay change will result in the two optical combs 1 with a delay of ΔT having The relative motion between the two optical combs achieves an equivalent dual-comb scanning. That is, since the soliton pulses output by optical comb 1 in this system are themselves undergoing periodic time-domain scanning, this fixed delay causes the relative time delay of the two pulses to appear as a continuous periodic scan when they reach the beam convergence point. This effect is completely equivalent to the relative time travel caused by the inherent small repetition rate difference between two traditional optical combs 1. This effect is known as the equivalent repetition rate difference.

[0067] The beam combining and detection module 23 is used to combine two signals and detect the interference signal. Specifically, the beam combining and detection module 23 is used to re-bend one light source that has undergone frequency shifting and the other light source that has undergone delay processing, and make them interfere. The interference signal is converted into an electrical signal by a photodetector and recorded to form a time-domain interferogram.

[0068] The signal processing module 24 is connected to the beam combining detection module 23 and is used to determine the distance based on the interference signal.

[0069] Distance measurement system 2 uses a single optical comb 1, achieving the effect of dual-comb measurement. Since the two interfering optical signals originate from the same optical comb 1 before beam splitting, they naturally share the excellent coherence of this optical comb 1, i.e., they possess perfect mutual coherence. This fundamentally eliminates the most complex, expensive, and unstable part of traditional dual-comb systems—namely, the ultra-narrow linewidth reference laser and multi-loop phase-locked electronics system used to ensure the mutual coherence of the two independent lasers. Therefore, the distance measurement system 2 provided in this application represents a significant improvement in system complexity, size, cost, and practicality.

[0070] In some embodiments, the set delay ΔT introduced by the delay line module 22 is related to the period of the phase modulation. Satisfying ΔT≈ / 2. Assumption According to the sine variation, It will change in the opposite direction of the sine wave, so the relative delay change corresponds to a change of twice the sine wave. For example, when the modulation frequency is 5 MHz ( When ΔT = 200 ns, ΔT is approximately 100 ns. Therefore, ΔT ≈ / 2 allows for a relatively large range of delayed scans.

[0071] The choice of this specific delay amount is an optimal design to obtain the maximum equivalent repetition rate scanning range. Mathematically, if the time-domain position of a single pulse moves according to a sine function (amplitude B), then it is delayed... The other pulse of / 2 will move according to an inverted sine function. The relative delay scan between these two pulses will also be a sine function, but with an amplitude of 2B, double that of a single pulse. This means that by choosing ΔT≈ / 2, we maximized the equivalent repetition rate sweep range without increasing the single-channel phase modulation power. This directly increases the unambiguous range (NAR) of the ranging and improves the signal-to-noise ratio.

[0072] The delay ΔT can be implemented using long optical fibers, or, for photonic integration in subsequent systems, can be replaced by on-chip delay lines. In this embodiment, the delay line module 22 includes a long delay line 221 and an adjustable extension line, using a sine wave (frequency f). m High-speed timing scanning of the time-programmable optical comb 1 is achieved through modulation at 5 MHz, and one of the channels is delayed by a long delay line 221 (total length approximately 20 m) to obtain a time delay of approximately 100 ns. The long delay line 221 includes approximately 17.5 m of single-mode fiber (SMF-28e) and approximately 2.5 m of dispersion compensating fiber (DCF) to manage net dispersion, thereby reducing soliton pulse broadening.

[0073] The reason for not using a triangular wave to scan the soliton timing is to avoid distortion caused by higher harmonics, given the limited modulation bandwidth. This is because the relative time delay scanning range in the experiment is smaller than the microcavity round-trip period τ. R The adjustable delay line 222 can be used to adjust the τ. R Fine-tuning the relative delay within the range allows the solitons of the two relative scans to overlap in time, thereby achieving equivalent dual-comb measurements.

[0074] exist Figure 5 In the illustrated embodiment, the signal processing module 24 includes a resampling module 25 and a multiheterodyne interferometry module 26. The resampling module 25 is connected between the beam combining detection module 23 and the multiheterodyne interferometry module 26. The resampling module 25 is used to convert the nonlinear delay scan in the interference signal into a linear delay scan. The multiheterodyne interferometry module 26 is used to perform a Fourier transform on the linear delay scan interference signal, extract the intensity and phase information of the interference signal, and generate a radio spectrum that can be used for range analysis.

[0075] Since optical comb 1 achieves soliton scanning by being driven by a sine wave (or other nonlinear periodic waveform), the relative delay scan between the two pulses exhibits a nonlinear time signature (e.g., sinusoidal shape). If a Fourier transform is directly performed on the time-domain interferogram acquired under this nonlinear scan, the spectrum will be severely broadened and distorted, making it impossible to distinguish clear RF comb teeth. Signal processing module 24 includes a resampling module 25 and a multiheterodyne interferometry module 26 connected to it. The resampling module 25 uses a unique multi-step digital signal processing flow to accurately correct the nonlinear sinusoidal delay scan to an ideal linear delay scan in the data domain. This facilitates the multiheterodyne interferometry module 26 to perform a Fourier transform on the linear delay scan interference signal, extract the intensity and phase information of the interference signal, and generate an RF spectrum that can be used for range analysis.

[0076] Please refer to Figure 6 , Figure 6 This is the original diagram of the time-domain interferometric signal, because... Figure 6 In the illustrated embodiment, a sinusoidal wave drive is used to achieve soliton scanning. The sinusoidal scan must be resampled to a linear scan to correctly recover the spectrum. However, in this application, the beam-splitting frequency shifting module 21 shifts one of the beams by 350 MHz. Directly resampling the original interference signal would destroy the carrier wave. Therefore, in... Figure 5 In the embodiment shown, the resampling module 25 includes a positioning unit 251, a linear fitting unit 252, a Fourier transform unit 253, an offset removal unit 254, a linear correction unit 255, and a splicing unit 256 connected in sequence.

[0077] The positioning unit 251 is used to: locate the envelope peak of the acquired interference signal and take the midpoint between adjacent peak times as the scanning direction reversal point. The positioning unit 251 is responsible for accurately extracting the motion model parameters of the pulse relative delay scanning from the acquired raw time-domain interference signal. Its processing flow is as follows: first, the envelope peak position of each interference pulse sequence in the interferogram is identified; then, the midpoint between two adjacent peak times is taken, and this midpoint time is determined as the scanning direction reversal point, corresponding to the moment when the relative delay between the two pulses reaches its maximum or minimum. Ideally, these midpoint times are strictly periodic, with a repetition period equal to half the phase modulation period, i.e., 1 / 2. When the modulation frequency At 5 MHz, the period is 100 ns.

[0078] The linear fitting unit 252 is used to: perform linear fitting between the midpoint index and the corresponding time, and calculate the phase of the sinusoidal scan based on the intercept obtained from the fitting. The linear fitting unit 252 receives the reversal point time sequence output by the positioning unit 251, and deduces the initial phase parameters of the sinusoidal scan motion by performing linear fitting on these discrete time points. Specifically, it performs least-squares linear fitting with the index of each reversal point as the independent variable and the measured time as the dependent variable. Since the reversal points are ideally strictly equally spaced (appearing once every half modulation cycle), the intercept t0 of the fitted line carries the initial phase information of the scan motion. (Sinusoidal scan phase) Therefore, the relationship between the relative delay scan between the two pulses and the slowly varying time can be fully described as follows: ;in This represents the amplitude of the sinusoidal relative delay scan. This unit transforms the discrete time points acquired by the positioning unit 251 into a continuous, parameterized motion mathematical model, providing a precise mathematical basis for all subsequent model-based resampling corrections. Essentially, it completes the mathematical modeling from discrete observations to a continuous motion model.

[0079] The Fourier transform unit 253 is used to perform a Fourier transform on the entire interference signal to obtain the spectrum containing the frequency-shifted carrier. The Fourier transform unit 253 directly performs a global Fourier transform on the acquired original time-domain interferogram before any resampling processing. Its purpose is to convert the time-domain signal to the frequency domain so that carrier removal and forward / reverse scanning separation can be performed using frequency-domain operations. Since the system has already introduced an f-wave frequency shifter into one of the signals on the optical path... AOM With a fixed frequency offset (e.g., 350 MHz), the useful signal in the Fourier transform spectrum will be concentrated around +f AOM The positive frequency range centered on this.

[0080] The offset removal unit 254 is used to: shift the entire positive spectrum downwards by the frequency offset introduced by the beam shifting module 21, discard the negative spectrum, and then obtain a carrier-free interference pulse sequence through inverse Fourier transform. The offset removal unit 254 receives the carrier-containing spectrum generated by the Fourier transform unit 253 and performs three ordered operations: bandpass filtering, spectrum shifting, and signal reconstruction. First, a bandpass filter is used in the frequency domain to retain only the useful signal range centered on the positive frequency, while filtering out unwanted images and low-frequency noise in the negative frequency range. Second, the entire retained positive spectrum is shifted downwards by a frequency offset f precisely equal to that introduced by the frequency shifter. AOMThe value is shifted to near zero frequency. The third step involves performing an inverse Fourier transform on the processed spectrum to re-obtain a complex, time-domain interference pulse sequence with carrier offset removed. This complex time-domain signal demodulates complete amplitude and phase information, enabling subsequent segmentation according to the scanning direction. Without this step and directly resampling the original interferogram, the 350 MHz carrier will be destroyed, preventing proper signal recovery. This unit is the crucial link in the entire signal processing chain. It uses frequency domain filtering and spectrum shifting to cleanly remove the frequency labels introduced to distinguish between forward and reverse scans, preserving the information of the forward and reverse scan signals completely in the reconstructed complex time-domain signal, paving the way for the segmentation processing of the linear correction unit 255.

[0081] The linear correction unit 255 is used to: divide the carrierless interference pulse sequence into forward and backward scanning segments according to the scanning direction, and resample the nonlinear delay within each segment according to the phase of the sinusoidal scan, correcting it to a linear time delay. The linear correction unit 255 is the core of the resampling algorithm. It receives the carrierless complex interference pulse sequence output by the offset removal unit 254, and performs physical straightening correction on the nonlinear delay scan in the signal based on the motion model jointly established by the positioning unit 251 and the linear fitting unit 252. The specific operation consists of three steps: First, segmentation according to the scanning direction: According to the reversal point of the scanning direction, the continuous time-domain signal is cut into independent data segments, each segment strictly corresponding to one simple forward or backward scan process. Second, intra-segment resampling: Within each data segment, although the sampling points of the signal are equally spaced in real time, the physical relative delay of the two corresponding pulses varies according to a sinusoidal law. The linear correction unit 255 calls the established sinusoidal motion model and resamples the data segment using a numerical interpolation algorithm. It recalculates and maps the originally equally spaced sampling points on the sinusoidal time coordinate to the linear time coordinate. During resampling, the physical scan range corresponding to each segment is strictly maintained. In the third step, correction is complete: after this processing, the sampling times of the data within the segment no longer correspond to uniform real time, but rather to uniform physical relative delays. All distortions and blurring caused by the nonlinear scan are completely eliminated in this step. This unit is the core of the entire algorithm, transforming curved motion into straight motion. It converts the physically feasible sinusoidal periodic motion into a mathematically rigorous linear scan model, providing the standard linear equally spaced sampling conditions required for the Fourier transform. This is the fundamental reason why this system can ultimately extract a clear, distortion-free spectrum from the nonlinear scan signal.

[0082] The splicing unit 256 is used to: splice the co-directional scan segments of the interference pulse sequence corrected to linear time delay, and then perform a Fourier transform to obtain an interference signal with a hyperbolic secant envelope. The splicing unit 256 is responsible for reassembling and integrating the linearly corrected independent data segments. It concatenates all the forward scan segment data corrected to linear delay scans end-to-end in time sequence into a complete and coherent long sequence; the backward scan segments are spliced ​​in the same way. Then, a second Fourier transform is performed on the spliced ​​co-directional scan long sequence to finally generate a radio frequency spectrum that can be used for physical quantity extraction. The radio frequency spectrum obtained by this second Fourier transform exhibits a clear and characteristic hyperbolic secant envelope, with its comb spacing equal to the modulation frequency. twice, that is, 2 .like Figure 7 As shown, Figure 7 The resulting RF power and phase spectra are obtained after resampling. The splicing unit 256 reconnects the fragmented segments, after fine-tuned segmentation correction, into a long sequence that meets the requirements of standard spectrum analysis. This operation not only satisfies the data volume requirements of Fourier transform (the long sequence implies high frequency resolution), but the unidirectional splicing strategy also ensures that the data participating in the final Fourier transform are completely consistent with its sampling mapping relationship. The final output RF power and phase spectra, with clear envelopes and equally spaced comb teeth, serve as the direct information source for the multiheterodyne interferometry module 26 to perform high-precision phase extraction and range inversion.

[0083] In some embodiments, soliton scanning can also be achieved using linear waves such as triangular waves. When soliton scanning is achieved using triangular wave driving, the resampling module is basically the same as when soliton scanning is achieved using sine wave driving. The difference is that when soliton scanning is achieved using triangular wave driving, the resampling module includes a positioning unit 251, a linear fitting unit 252, a Fourier transform unit 253, an offset removal unit 254, and a stitching unit 256, but does not include a linear correction unit 255.

[0084] Please refer to Figure 8 , Figure 8 This is a schematic diagram of the structure of a distance measurement system 2 provided in one embodiment of this application. Figure 8 In the illustrated embodiment, the distance measurement system 2 further includes a beam splitting module 261, a reference reflector 262, and a measurement reflector 263. The beam splitting module 261 is connected to the beam splitting and frequency shifting module 21 and is used to split the first of the two signals into a reference signal and a measurement signal. The reference reflector 262 is used to make the reference signal return and interfere with the second of the two signals to obtain a reference interference signal. The measurement reflector 263 is used to make the measurement signal return and interfere with the second signal to obtain a measurement interference signal. The signal processing module 24 is used to determine the distance based on the reference interference signal and the measurement interference signal.

[0085] Thus, the distance measurement system 2, based on the equivalent dual-comb measurement system, further adds a beam-splitting module 261, a reference mirror 262, and a measurement mirror 263. The beam-splitting and frequency-shifting module 21 has already divided the beam output from the optical comb 1 into a first path and a second path, where the first path is a signal pulse and the second path is a local oscillator pulse. The path containing the local oscillator pulse has been configured with a delay line module 22 according to the aforementioned scheme. By setting the beam-splitting module 261, the signal pulse can be further divided into two paths: a reference path signal and a measurement path signal. The reference path signal illuminates a fixed-position reference mirror 262 and returns along the same path after reflection. The measurement path signal illuminates a measurement mirror 263 placed at the target location and also returns along the same path after reflection. The returned reference path signal and measurement path signal are combined and interfered with the local oscillator pulse processed by the delay line module 22, respectively. Within a complete measurement cycle (the cycle is half the modulation cycle, i.e., 1 / 2), the signal is measured. The detector will receive two interference signals sequentially: a reference interference signal and a measurement interference signal. The reference interference signal is generated by the interference of the reference path signal and the local oscillator pulse. The measurement interference signal is generated by the interference of the measurement path signal and the local oscillator pulse. The information about the measured distance is contained in the time delay difference between these two interference signals. Since the position of the reference mirror is fixed and known, the change in the distance between the measuring mirror and the reference mirror is directly reflected in the time delay of the measurement interference signal relative to the reference interference signal.

[0086] In this embodiment, the delay line module 22 includes a long delay line 221 and an adjustable delay line 222. The long delay line 221 is disposed on the local oscillator pulse path, and the adjustable delay line 222 is disposed on the signal pulse path. It also includes multiple collimators 271, a polarization multiplexing spatial optical path 27, a beam splitter 272, multiple waveplates 273, two third detectors 264, and a second oscilloscope 265.

[0087] The reference interference signal and the measurement interference signal acquired by the two third detectors 264 are first processed by the aforementioned resampling module 25 to be corrected into interference signals under linear delay scanning, and then Fourier transformed to generate their respective clear radio frequency spectra. Afterwards, the signal processing module 24 performs the following calculation steps to complete the high-precision inversion of the absolute distance.

[0088] Step 1: Frequency Domain Phase Extraction. The phase information of each RF comb tooth obtained after resampling and Fourier transform is extracted. This yields the spectral phase of the reference path. and the spectrum phase of the measurement path , where ω is the angular frequency relative to the pump light.

[0089] Step 2: Use the time-of-flight method to coarsely measure the distance and determine the unambiguous distance. This step utilizes the phase information of multiple comb teeth to solve for the absolute distance by fitting the phase slope. The principle is as follows: The time delay τ of the light pulse traveling in space is represented by a linear phase slope in the frequency domain, that is: Where τ is the additional flight time delay of the measurement pulse relative to the reference pulse. The phase difference between the measurement path and the reference path... A linear fit is performed with the angular frequency ω as the independent variable, and the resulting slope is the group delay τ. Since the measurement pulse travels one round trip distance, the flight time is τ = 2L / c. Therefore, the absolute distance L to be measured can be calculated by the following formula: Where c is the speed of light. In practice, several comb teeth (e.g., 13) with the highest RF power signal-to-noise ratio are selected for fitting to obtain the statistically optimal slope estimate. The distance L obtained in this step is an unambiguous absolute distance, but its accuracy is limited by the statistical error of phase fitting and is usually only used as a coarse measurement result.

[0090] Step 3: Precise measurement using interferometry. This step utilizes the phase information of a single comb tooth to achieve extremely high-precision interferometric measurement within a microscopic scale of half a wavelength. The principle is as follows: Light is a wave, and the distance to be measured changes by half a carrier wavelength ( / 2), the phase of the reflected light will change for a full 2π cycle. Therefore, by measuring the phase ϕ of a single comb tooth, the fractional part of the distance to be measured within half a wavelength scale can be accurately determined: ,in Let M be the carrier wavelength, and M be an unknown integer representing how many complete half-wavelengths the distance to be measured contains. The existence of M is the inherent unambiguous range limitation of interferometry—interferometry alone cannot determine which half-wavelength the distance is.

[0091] Step 4: Two-step fusion to achieve final high-precision measurement. The time-of-flight method and interferometry are used in tandem to leverage their respective strengths: The integer ambiguity M is calculated using the coarse measurement results; the absolute distance L is substituted into the following formula to determine the integer M: Since the error of the coarse distance L is much smaller than half a wavelength, the M calculated from this is unique and accurate.

[0092] Correcting the final distance using precise measurement results: Substituting the determined integer M and the high-precision phase ϕ measured from a single comb tooth into the interferometric precise measurement calculation formula, the final high-precision absolute distance is obtained. This distance method combines the advantages of the time-of-flight method (TOF) in terms of its wide range of unambiguous data with the sub-nanometer precision of the interferometric method.

[0093] The distance measurement method described in this application utilizes an equivalent dual-optical-comb system to generate two interferometric signals: a reference signal and a measurement signal. A resampling algorithm ensures spectral purity. Then, at the data processing end, it organically integrates the wide-range, unambiguous ranging of the time-of-flight method with the high-precision single-wavelength ranging of the interferometric method. This two-step synergy perfectly resolves the core contradiction in precision ranging where accuracy and range are mutually exclusive.

[0094] exist Figure 8 In the embodiment shown, the distance measurement system 2 further includes a polarization multiplexed spatial optical path 27, in which the reference path signal and the measurement path signal are transmitted in orthogonal polarization states.

[0095] In ranging systems, optical pulses need to be transmitted to the measuring end through long optical fibers. Ambient temperature and mechanical vibrations can cause minute fluctuations in the fiber length, which are directly converted into optical path noise. If this noise is inconsistent between the reference path and the measuring path, it will severely compromise nanometer-level ranging accuracy. To address this, this application adds a polarization-multiplexed spatial optical path 27. The core idea is to allow the reference light and the measuring light to transmit in orthogonal polarization states along identical physical paths, converting fiber length fluctuations into common-mode noise shared by both paths, which is then canceled out by differential phase measurement.

[0096] like Figure 8 As shown, the working process of the polarization multiplexing spatial optical path 27 is as follows: the reference path signal and the measurement path signal are modulated into a pair of orthogonal linear polarization states (such as horizontal and vertical polarization), and then combined into the same spatial optical path through a polarization beam splitter. The combined beam propagates along the same path and illuminates the reference mirror 262 at a fixed position and the measurement mirror 263 on the target under test, respectively. The reflected beam is precisely separated into two paths according to the polarization state by the polarization beam splitter, and the time-domain interference signals of each path are recorded by a detector.

[0097] Since the reference light and the measurement light share the same physical channel with orthogonal polarization states in most optical paths (especially long fiber segments), any fluctuation in fiber length introduces identical optical path changes to both paths, manifesting as common-mode phase noise. During signal processing, the spectral phase of the reference path and the measurement path is extracted. and Calculate the phase difference Common-mode noise is precisely differentially canceled. The remaining phase difference reflects only the change in the actual spatial distance between the reference mirror and the measuring mirror.

[0098] After resampling the two interference signals separately, the spectral phase is extracted. Several comb teeth (13 in this example) with the highest power-to-noise ratio are selected for further processing. A linear fit is performed, and the flight time is obtained from the slope, from which the absolute distance is calculated. The optical frequency spacing between adjacent RF comb teeth is Δω = 2π / t. ar Therefore, the scan amplitude tar The unambiguous range (NAR) directly determines the ranging distance. To obtain a larger t... ar This embodiment adopts the following design: each of the two paths has a delay T m / 2: The amplitude of the single-path soliton motion is t ar After a half-cycle delay, the relative scanning amplitude of the two paths reaches 2t. ar Equivalent scan amplitude t ar ≈4t ar Precise calibration of optical path difference: The signal path and the local oscillator path constitute a non-equilateral Mach-Zehnder interferometer, and its optical path difference δ d It consists of an optical fiber section (delay line and polarization controller) and a free space section. This embodiment calibrates δ. d =32.87m. Precise t ar calculate: Substituting the parameters, we get the proportionality coefficient |sin(π) δdf m / c)|=0.989, close to the theoretical maximum value of 1, achieving the optimal scanning magnification effect.

[0099] In this embodiment, the polarization multiplexing spatial optical path 27 uses simple optical means to convert the fiber noise introduced by the environment into a common-mode signal and differentially eliminate it; combined with the optical path difference optimization design, it ensures that the system achieves high-precision absolute distance measurement with the maximum equivalent scanning range.

[0100] Please refer to Figure 9 , Figure 9 This is a schematic diagram of the structure of a distance measurement system 2 according to another embodiment of this application. Figure 9 In the embodiment shown, the distance measurement system 2 further includes a spatial dispersion optical path 28, which includes a diffraction grating 281 and a focusing lens 282. The diffraction grating 281 is located at the front focal point of the focusing lens 282, and the sample to be measured 284 is located at the rear focal point of the focusing lens 282. The diffraction grating 281 is used to disperse the comb teeth of different frequencies of the optical comb 1 at different angles, and the focusing lens 282 is used to focus the dispersed comb teeth to different spatial positions on the surface of the sample to be measured 284, forming multiple independent measurement channels for parallel distance measurement.

[0101] A key feature of microcavity optical combs is their large tooth spacing and wide bandwidth. This embodiment can serve as a parallel lidar system based on a time-programmable microcavity soliton optical frequency comb. Utilizing the inherent multi-channel parallel characteristics of the optical comb 1, simultaneous measurement of multi-point position information can be achieved. By constructing a parallel lidar ranging optical path, a grating is used to disperse different teeth of the microcavity optical comb to different positions on the surface of the sample 284 under test, forming multiple independent measurement channels and establishing a one-to-one mapping relationship between the frequency of the optical comb 1 and its spatial position. In this embodiment, the optical comb 1 is amplified by a semiconductor optical amplifier 283 (model BOA1550S) to compensate for the relatively high power loss in non-cooperative target measurement. The semiconductor optical amplifier 283 has an amplification bandwidth of 105 nm near 1550 nm and can amplify more than 120 teeth. The reflective grating is placed at the front focal point of the lens, and the sample 284 under test is placed at the rear focal point of the lens. The grating line density is 900 lines / mm, and the lens focal length is 20 cm. The spectral line phase ϕ(n) at different channels is obtained through multiheterodyne measurements, and high-precision interferometric distance is calculated using the phase of a single spectral line. L int For static objects, the height variation in different regions of the sample can be determined by comparing the phase difference of different comb tooth numbers. For vibrating objects, the parallel lidar architecture enables simultaneous measurement of multi-point vibration information and analysis of the sensitivity measurement limit. This invention will achieve high frame rate, multi-point dynamic non-contact distance measurement, and can be used for high-frequency vibration monitoring of micro-electro-mechanical systems (MEMS), surface acoustic wave devices, and opto-mechanical devices, replacing traditional white light interferometers.

[0102] This application also provides an optical sensing system based on a time-programmable microcavity optical comb 1. The applications of this time-programmable microcavity optical comb 1 and its equivalent dual-comb system are not limited to the field of ranging. For example, it can be used as a light source for dual-comb spectral measurements. By allowing the signal light to pass through the sample and interfere with the local oscillator light, the absorption spectrum of the sample can be rapidly obtained, achieving high-speed, high-sensitivity gas sensing and environmental monitoring. The sample can be a gas, liquid, or solid. Furthermore, because this optical comb 1 possesses unique, high-speed programmable soliton pulse timing manipulation capabilities, it can be directly used to generate multi-pulse excitation sequences with precise time delays, applicable to the field of multidimensional coherent spectroscopy, to study and analyze complex dynamic processes such as coherent coupling and energy transfer in atomic, molecular, semiconductor, and quantum materials.

[0103] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the following claims.

[0104] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A time-programmable microcavity optical comb, characterized in that, include: The first laser is used to generate pump light; An optical resonant cavity is provided, wherein the first laser is connected to the optical resonant cavity to couple the pump light with the optical resonant cavity, and an optical comb is formed in the pump cavity film within the optical resonant cavity, the optical comb comprising multiple comb teeth; An injection modulation module is used to perform phase modulation on the injected laser and inject the phase-modulated injected laser into the optical resonant cavity to achieve frequency locking and phase synchronization of the nth comb tooth, thereby controlling the time domain position of the optical comb pulse, wherein the frequency of the injected laser is located within the locking bandwidth of the nth comb tooth.

2. The time-programmable microcavity optical comb according to claim 1, characterized in that, The injection modulation module includes: A second laser is used to generate the injected laser; A phase modulation unit is used to perform phase modulation on the injected laser; An injection coupling unit is used to inject phase-modulated injection laser light into the optical resonant cavity.

3. The time-programmable microcavity optical comb according to claim 2, characterized in that, The phase modulation unit includes an electro-optic phase modulator; and / or The phase modulation unit is used to apply a sinusoidal modulation signal to the injected laser to perform phase modulation on the injected laser.

4. The time-programmable microcavity optical comb according to claim 1, characterized in that, The optical resonant cavity is an optical microcavity, which includes a microcavity integrated on a substrate and a crystal whispering-gallery mode microcavity. The optical resonant cavity is either micro-ring-shaped or racetrack-shaped; or The optical resonant cavity is an optical fiber resonant cavity.

5. The time-programmable microcavity optical comb according to claim 1, characterized in that, The optical comb also includes a frequency scanning module, which is connected to the first laser and is used to tune the pump light to achieve frequency scanning of the pump light. The frequency scanning module includes: The first signal generator is used to generate a changing voltage signal; A voltage-controlled oscillator, connected to the first signal generator, is used to output a single-frequency radio frequency signal whose frequency varies with the voltage signal; A frequency modulator is connected to the voltage-controlled oscillator and the first laser. The frequency modulator operates in carrier-suppressed single-sideband modulation mode and is used to receive the pump light from the first laser. The single-frequency radio frequency signal output by the voltage-controlled oscillator is used as the modulation drive to realize the frequency scanning of the pump light.

6. The time-programmable microcavity optical comb according to claim 1, characterized in that, The optical comb also includes an injection lock monitoring module, which includes: The first filter, connected to the optical resonant cavity, is used to output the signal of the nth comb tooth; A first detector, connected to the first filter, is used to observe the beat frequency signal between the nth comb tooth and the injected laser, so as to adjust the frequency of the injected laser according to the beat frequency signal, so that the frequency of the injected laser is located near the center of the locked bandwidth of the nth comb tooth.

7. The time-programmable microcavity optical comb according to claim 1, characterized in that, The optical comb further includes an optical comb motion trajectory reconstruction module, which includes: The second filter, connected to the optical resonant cavity, is used to output the signal of the kth comb tooth, where k is not equal to n and 0; The third laser is used to output continuous laser. The third laser is connected to the second filter. The continuous laser and the signal of the kth comb tooth are heterodyne beat frequency to generate a heterodyne beat frequency signal. The second detector, connected to both the second filter and the third laser, is used to observe the heterodyne beat frequency signal in order to reconstruct the soliton motion trajectory based on the heterodyne beat frequency signal and the sideband intensity theory.

8. An application system for a time-programmable microcavity optical comb, characterized in that, include: The time-programmable microcavity optical comb as described in any one of claims 1-7.

9. The application system of the time-programmable microcavity optical comb according to claim 8, characterized in that, The application system is a distance measurement system, which further includes: The beam splitting and frequency shifting module is connected to the optical comb and is used to split the output signal of the optical comb into two signals and shift the frequency of one of the signals. The delay line module, connected to the beam splitter frequency shifter module, is used to introduce a set delay into one of the signals so that the two signals generate a relative delay scan. The beam combining and detection module is used to combine two signals and detect interference signals. A signal processing module, connected to the beam combining detection module, is used to determine the distance based on the interference signal.

10. The application system of the time-programmable microcavity optical comb according to claim 9, characterized in that, The delay line module introduces a set delay ΔT and a phase modulation period T. m Satisfying ΔT≈T m / 2.

11. The application system of the time-programmable microcavity optical comb according to claim 9, characterized in that, The signal processing module includes a resampling module and a multiheterodyne interferometry module, wherein the resampling module is connected between the beam combining detection module and the multiheterodyne interferometry module; The resampling module is used to convert the nonlinear delayed scan in the interference signal into a linear delayed scan; the multiheterodyne interferometry module is used to perform Fourier transform on the linear delayed scan interference signal, extract the intensity and phase information of the interference signal, and generate a radio spectrum that can be used for distance analysis.

12. The application system of the time-programmable microcavity optical comb according to claim 11, characterized in that, The resampling module includes a positioning unit, a linear fitting unit, a Fourier transform unit, an offset removal unit, a linear correction unit, and a stitching unit connected in sequence. The positioning unit is used to: locate the envelope peak of the acquired interference signal, and take the midpoint between adjacent peak times as the scanning direction reversal point; The linear fitting unit is used to: perform linear fitting with the midpoint index and the corresponding time, and calculate the phase of the sinusoidal scan based on the intercept obtained from the fitting. The Fourier transform unit is used to: perform a Fourier transform on the entire interference signal to obtain a spectrum containing the frequency-shifted carrier; The offset removal unit is used to: shift the positive spectrum downward by the frequency offset introduced by the beam-splitting frequency shifting module, discard the negative spectrum, and then obtain a carrier-free interference pulse sequence through inverse Fourier transform; The linear correction unit is used to: divide the carrierless interference pulse sequence into a forward scanning segment and a backward scanning segment according to the scanning direction, and resample the nonlinear delay in each segment according to the phase of the sinusoidal scan to correct it into a linear time delay; The splicing unit is used to splice the same-direction scanning segments of the interference pulse sequence corrected to linear time delay, and then perform Fourier transform to obtain a radiation spectrum with a hyperbolic secant envelope.

13. The application system of the time-programmable microcavity optical comb according to claim 9, characterized in that, The distance measurement system further includes a beam splitting module, a reference mirror, and a measurement mirror. The beam splitting module is connected to the beam splitting and frequency shifting module and is used to split the first of the two signals into a reference signal and a measurement signal. The reference mirror is used to make the reference signal return and interfere with the second of the two signals to obtain a reference interference signal. The measurement mirror is used to make the measurement signal return and interfere with the second signal to obtain a measurement interference signal. The signal processing module is used to determine the distance based on the reference interference signal and the measurement interference signal.

14. The application system of the time-programmable microcavity optical comb according to claim 13, characterized in that, Also includes: A polarization-multiplexed spatial optical path, wherein the reference path signal and the measurement path signal are transmitted in the polarization-multiplexed spatial optical path with orthogonal polarization states.

15. The application system of the time-programmable microcavity optical comb according to claim 9, characterized in that, It also includes a spatial dispersion optical path, which includes a diffraction grating and a focusing lens; the diffraction grating is located at the front focal point of the focusing lens, and the sample to be tested is located at the rear focal point of the focusing lens; the diffraction grating is used to disperse the comb teeth of different frequencies of the optical comb at different angles, and the focusing lens is used to focus the dispersed comb teeth to different spatial positions on the surface of the sample to be tested, forming multiple independent measurement channels for parallel distance measurement.

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