On-chip femtosecond pulse generation device and method based on integrated frequency comb and time domain phase control

Abstract

The application discloses an on-chip femtosecond pulse generation device and method based on integrated frequency comb and time domain phase control, which comprises an integrated optical frequency comb light source module, an SOA intensity modulation module, a time correlation phase modulation module and a dispersion compensation and pulse compression unit which are sequentially coupled in the light transmission direction, and is further provided with an adaptive control unit, wherein the feedback collection end of the adaptive control unit is coupled to the output light path. The application synchronously controls the phase curvature coefficient K and the dispersion compensation amount D through the adaptive control unit, dynamically maintains the Fourier transform limit matching relationship, combines the feedforward mapping and feedback correction double-loop structure, and compensates the thermal-optical dispersion coupling drift of the heterogeneous integrated chip in real time. The application can realize low-jitter and high-stability femtosecond pulse output on a single integrated chip, effectively solves the problems of pulse width broadening and time domain sidelobe degradation of a traditional open-loop system, and is suitable for scenes such as ultrafast optics and on-chip photon systems.

Description

Technical Field

[0001] This invention relates to the field of integrated photonics and ultrafast optics, specifically to an on-chip femtosecond pulse generation device and method based on integrated frequency comb and time-domain phase modulation. Background Technology

[0002] Ultrashort femtosecond pulses are core light sources in fields such as precision measurement, optical communication, quantum information, and ultrafast spectroscopy. Traditional implementation schemes mainly include: 1. Mode-locked lasers: rely on precision optical resonant cavities and mechanical tuning mechanisms, are bulky, have a fixed repetition rate, are difficult to tune, and are hard to integrate on a chip; 2. Microcavity Kerr optical frequency comb: Based on third-order nonlinear effects, although it can be integrated, it has low conversion efficiency, weak single comb line power, high phase noise, and is limited by the free spectral range of the microcavity and thermal detuning effect; 3. Electro-optic modulation synthesis scheme: It uses radio frequency drive intensity / phase modulator to generate frequency comb or pulse, but it requires complex microwave source, bias control and phase locking. The system has high power consumption and large size, and the modulation nonlinearity can easily introduce phase distortion.

[0003] Time-correlated phase modulation (TCP) technology, by introducing phase modulation in the time domain, can achieve a Fourier-like transform in the time-frequency domain, theoretically compressing nanosecond pulses to the femtosecond level. However, existing phase modulation systems mostly use discrete optical components, which present three major bottlenecks: 1) The matching relationship between the driving RF signal and the dispersive element relies on manual calibration, and environmental or device drift can easily lead to mismatch, causing pulse broadening, increased sidelobes, and deterioration of pulse width stability; 2) The use of discrete components results in low integration, large size, and high power consumption, making it difficult to guarantee long-term operational stability; 3) The lack of a real-time closed-loop compensation mechanism between phase curvature and dispersion compensation makes it impossible to suppress drift disturbances and maintain the consistency and reliability of pulse output. How to deeply integrate phase modulation, linear amplification, and adaptive dispersion stabilization control to achieve wide-range, high-fidelity, and transform-limited dynamic output of femtosecond pulses under the premise of full-chip integration remains a technological gap in the field of integrated ultrafast light sources. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an on-chip femtosecond pulse generation device and method based on integrated frequency comb and time-domain phase modulation. This invention discloses an on-chip femtosecond pulse generation device based on integrated frequency comb and time-domain phase modulation, comprising a light source module, an SOA intensity modulation module, a time-correlated phase modulation module, a dispersion compensation and pulse compression unit, and an output coupling interface, which are sequentially coupled along the optical signal propagation direction via on-chip optical waveguides; it also includes an adaptive control unit, which is electrically connected to the time-correlated phase modulation module and the dispersion compensation and pulse compression unit, and the feedback acquisition terminal of the adaptive control unit is coupled to the output optical path of the output coupling interface; The adaptive control unit is used to acquire the pulse width and spectral characteristic data of the output pulse in real time, and synchronously adjust the phase curvature coefficient of the time-correlated phase modulation module. The dispersion amount of the dispersion compensation and pulse compression unit Maintain dispersion With phase curvature coefficient satisfy The Fourier transform limit matching relationship is used to output a stable transform-limited femtosecond pulse sequence.

[0005] As a further improvement of the present invention, the light source module includes an RSOA active gain unit and a nonlinear microring resonant module, wherein the RSOA active gain unit and the nonlinear microring resonant module are coupled through an on-chip optical waveguide and form an external cavity resonant optical path. The RSOA active gain unit is used to provide broadband optical gain under electrical injection conditions and output stable single-wavelength pump light; the nonlinear microring resonator module is based on the third-order Kerr nonlinear effect to excite a four-wave mixing process and generate an equally spaced multi-longitudinal-mode original optical frequency comb. As a further improvement of the present invention, the light source module also includes an on-chip filtering module. The on-chip filtering module is coupled to the output end of the nonlinear micro-ring resonant module through an on-chip optical waveguide. It is used to perform differentiated attenuation and power equalization on each tooth of the original optical frequency comb, and output a flat optical frequency comb with a spectral flatness better than 3dB. As a further improvement of the present invention, the SOA intensity modulation module is configured with a pulse drive port for performing time-domain intensity modulation on the flat optical frequency comb by inputting a periodic electrical drive signal, cutting it into an optical pulse sequence with a fixed repetition frequency, and simultaneously linearly amplifying the optical pulse. As a further improvement of the present invention, the time-correlated phase modulation module includes an electro-optic phase modulator and a pulse driving circuit; the pulse driving circuit outputs a parabolic envelope electrical signal with pre-distortion compensation, and applies a secondary time-domain phase to the optical pulse. A linear frequency chirp is introduced into the light pulse. As a further improvement of the present invention, the dispersion compensation and pulse compression unit adopts an on-chip chirped Bragg grating structure and is provided with a dispersion tuning interface, which can provide -5ps. 2 Up to -50ps 2 The tunable negative group delay dispersion is used for temporal focusing and compression of light pulses carrying linear chirps. As a further improvement of the present invention, the adaptive control unit includes a pulse width stabilization reference input module, a mapping algorithm module, a phase modulation drive output module, a dispersion compensation drive output module, and a feedback acquisition interface; The mapping algorithm module has a built-in parameter lookup table for the thermal-optical-dispersion coupling drift of the heterogeneous integrated chip. It adopts a dual closed-loop control architecture of feedforward mapping pre-tuning and feedback error correction. Through feedforward mapping, it synchronously outputs phase and dispersion driving signals within ≤10μs, and performs PID closed-loop fine-tuning through the actual pulse width data collected by feedback, controlling the output pulse width jitter within 5%.

[0006] As a further improvement of the present invention, the adaptive control unit includes a pulse width stabilization reference input module, a mapping algorithm module, a phase modulation drive output module, a dispersion compensation drive output module, and a feedback acquisition interface; The mapping algorithm module has a built-in parameter lookup table for the thermal-optical-dispersion coupling drift of the heterogeneous integrated chip. It adopts a dual closed-loop control architecture of feedforward mapping pre-tuning and feedback error correction. Through feedforward mapping, it synchronously outputs phase and dispersion driving signals within ≤10μs, and performs PID closed-loop fine-tuning through the actual pulse width data collected by feedback, controlling the output pulse width jitter within 5%.

[0007] This invention discloses an on-chip femtosecond pulse generation method based on integrated frequency comb and time-domain phase modulation, which is implemented based on the aforementioned on-chip femtosecond pulse generation device, including: Step S1: Integrated optical frequency comb generation: A spectrum-flat, equally spaced multi-longitudinal-mode optical frequency comb is generated and output through the light source module; Step S2, Temporal Intensity Modulation: The flat optical frequency comb is periodically intensity-cut by the SOA intensity modulation module to form an optical pulse sequence with a fixed repetition frequency, and the optical signal is linearly amplified simultaneously. Step S3, Time-Domain Phase Modulation: Apply a secondary time-domain phase to the optical pulse through the time-correlated phase modulation module, introduce linear frequency chirp, and establish a mapping relationship between the time domain and frequency domain of the optical pulse; Step S4, Dispersion Matching Compression: Adjustable negative group delay dispersion is provided by dispersion compensation and pulse compression unit to perform time-domain compression on optical pulses carrying linear chirps; Step S5, Adaptive Closed-Loop Control: Real-time acquisition of the pulse width and spectral data of the output pulse, and synchronous adjustment of the phase curvature coefficient. With dispersion ,maintain The Fourier transform limit matching relationship is used to output a stable transform-limited femtosecond pulse.

[0008] As a further improvement of the present invention, step S5 specifically includes: Step S51, Feedforward Pre-configuration: Based on the set target pulse width parameters, call the built-in parameter lookup table to calculate the target phase curvature and target dispersion, and synchronously output the phase modulation drive signal and dispersion compensation drive signal within ≤10μs to complete the parameter feedforward pre-adjustment; Step S52, Feedback Fine Correction: Real-time acquisition of the actual pulse width data of the output pulse, error calculation with the target pulse width, fine adjustment of phase and dispersion driving voltage through PID control algorithm, dynamic compensation of device thermal and optical drift and environmental disturbances, and maintenance of long-term stable pulse output.

[0009] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention employs on-chip micro-ring optical frequency comb, modulator, and dispersive devices to achieve full optical link integration, significantly reducing system size and complexity, and possessing high integration.

[0010] This invention achieves dynamic matching of phase modulation and dispersion compensation through an adaptive control unit, effectively suppressing environmental disturbances and device drift, and exhibiting high stability.

[0011] This invention achieves transform-limited femtosecond pulse output through the synergistic effect of spectrum flattening, phase modulation, and dispersion compression, resulting in high-quality pulse output characteristics.

[0012] The functional modules of this invention can be implemented in various integrated forms, exhibiting strong structural flexibility and good process compatibility and scalability.

[0013] This invention achieves on-chip integrated femtosecond pulse generation through a collaborative mechanism of "nonlinear optical frequency comb generation - intensity and phase joint modulation - dispersion matching compression". It has the advantages of compact structure, simple implementation and high output stability, and is suitable for coherent optical communication, microwave photonics, ultrafast spectral analysis and quantum information processing. Attached Figure Description

[0014] Figure 1 This is a structural architecture diagram of an on-chip femtosecond pulse generation device based on integrated frequency comb and time-domain phase modulation, as disclosed in one embodiment of the present invention. Figure 2 This is a schematic diagram of the light source module structure of an on-chip femtosecond pulse generation device based on integrated frequency comb and time-domain phase modulation, as disclosed in an embodiment of the present invention. Figure 3This is a schematic diagram of the on-chip filtering module structure of an on-chip femtosecond pulse generation device based on integrated frequency comb and time-domain phase modulation, as disclosed in an embodiment of the present invention. Figure 4 This is a schematic diagram of the planar structure of the SOA intensity modulation module of an on-chip femtosecond pulse generation device based on integrated frequency comb and time-domain phase modulation, as disclosed in an embodiment of the present invention. Figure 5 This is a three-dimensional structural schematic diagram of a thin-film lithium niobate electro-optic phase modulator for a time-related phase modulation module of an on-chip femtosecond pulse generation device based on integrated frequency comb and time-domain phase modulation, as disclosed in an embodiment of the present invention. Figure 6 This is a schematic diagram of the chirped grating planar part of the dispersion compensation and pulse compression unit of an on-chip femtosecond pulse generation device based on integrated frequency comb and time-domain phase modulation, as disclosed in an embodiment of the present invention. Figure 7 This is a schematic diagram of the time-related phase modulation and dispersion adaptive matching principle of an on-chip femtosecond pulse generation method based on integrated frequency comb and time-domain phase modulation, as disclosed in an embodiment of the present invention. Figure 8 This is a block diagram of the signal flow and parameter mapping logic of an adaptive control unit for an on-chip femtosecond pulse generation method based on integrated frequency comb and time-domain phase modulation, as disclosed in one embodiment of the present invention. Figure 9 This is a schematic diagram illustrating the long-term stability of the output pulse width of a traditional open-loop scheme for an on-chip femtosecond pulse generation method based on integrated frequency comb and time-domain phase modulation, as disclosed in an embodiment of the present invention. Figure 10 This is a schematic diagram of the time-domain waveform of the output pulse of a conventional open-loop scheme for an on-chip femtosecond pulse generation method based on integrated frequency comb and time-domain phase modulation, as disclosed in an embodiment of the present invention. Figure 11 This is a schematic diagram illustrating the long-term stability of the output pulse width of the closed-loop scheme of the on-chip femtosecond pulse generation method based on integrated frequency comb and time-domain phase modulation, as disclosed in one embodiment of the present invention. Figure 12 This is a schematic diagram of the pure transform limit pulse time-domain waveform of the closed-loop scheme of the on-chip femtosecond pulse generation method based on integrated frequency comb and time-domain phase modulation, as disclosed in one embodiment of the present invention.

[0015] In the picture: 100. Light source module; 101. RSOA active gain unit; 102. Nonlinear micro-ring resonator module; 103. On-chip filter module; 1031. Thermo-optic tuning electrode; 200. SOA intensity modulation module; 2001. Multi-quantum well active waveguide region; 2002. Adiabatic tapered transition waveguide; 300. Time-correlated phase modulation module; 3001. Substrate; 3002. Optical waveguide; 3003. Modulation electrode; 3004. Modulation voltage interface; 400. Dispersion compensation and pulse compression unit; 500. Adaptive control unit; 501. Pulse width stabilization reference input module; 502. Mapping algorithm module; 503. Phase modulation drive output module; 504. Dispersion compensation drive output module; 505. Feedback acquisition interface; 600. Output coupling interface. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0018] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0019] The present invention will now be described in further detail with reference to the accompanying drawings: Example 1 like Figure 1As shown, an on-chip femtosecond pulse generation device based on integrated frequency comb and time-domain phase modulation according to the present invention includes a light source module 100, an SOA intensity modulation module 200, a time-correlated phase modulation module 300, a dispersion compensation and pulse compression unit 400, and an output coupling interface 600, which are sequentially coupled along the optical signal propagation direction via on-chip optical waveguides. It also includes an adaptive control unit 500, which is electrically connected to the time-correlated phase modulation module 300 and the dispersion compensation and pulse compression unit 400 to achieve closed-loop synchronous modulation. The feedback acquisition end of the adaptive control unit 500 is coupled to the output optical path of the output coupling interface 600. The adaptive control unit 500 is used to acquire the pulse width and spectral characteristic data of the output pulse in real time and synchronously adjust the phase curvature coefficient of the time-correlated phase modulation module 300. With dispersion compensation and pulse compression unit 400 dispersion amount Maintain dispersion With phase curvature coefficient satisfy The Fourier transform limit matching relationship is used to output a stable transform-limited femtosecond pulse sequence.

[0020] Specifically: like Figure 1-2 As shown, in the above embodiment, preferably, the light source module 100 includes an RSOA active gain unit 101 and a nonlinear microring resonator module 102. The RSOA active gain unit 101 and the nonlinear microring resonator module 102 are coupled through an on-chip optical waveguide and form an external cavity resonant optical path, outputting narrow-linewidth single-wavelength pump light. The RSOA active gain unit 101 adopts an InGaAsP / InP multi-quantum-well structure, including a semiconductor active waveguide region and a bias control interface. A high-reflection film is provided on the rear end face, and an anti-reflection structure is provided on the front end waveguide end face. The bias control interface only inputs DC bias current, with a bias current range of 20-200mA, providing broadband optical gain under electrical injection conditions. In this embodiment, the RSOA active gain unit 101 can also be replaced by a distributed feedback (DFB) laser, an external cavity semiconductor laser, or an external continuous wave (CW) laser source, etc., which can provide linewidth pump light.

[0021] In the above embodiments, preferably, the RSOA active gain unit 101 is used to provide broadband optical gain under electrical injection conditions and output stable single-wavelength pump light; the nonlinear microring resonant module 102 excites a four-wave mixing process based on the third-order Kerr nonlinear effect to generate an equally spaced multi-longitudinal-mode original optical frequency comb. The nonlinear microring resonant module 102 is an add-drop type microring resonant structure, including an input bus waveguide, a ring resonant cavity, and an output bus waveguide. The ring resonant cavity is coupled to the input bus waveguide and the output bus waveguide respectively through coupling regions. The microring is made of Si3N4 high nonlinear waveguide material, operates in the anomalous dispersion region, and has a quality factor of not less than 1×10⁻⁶. 6 Under resonant enhancement conditions, the pump light accumulates power within the micro-ring and undergoes a four-wave mixing process based on the third-order Kerr nonlinear effect, generating an equally spaced multi-wavelength optical frequency comb. The nonlinear micro-ring resonant module 102 receives the pump light through the input bus waveguide and outputs the optical frequency comb signal through the output bus waveguide.

[0022] like Figure 3 As shown, in the above embodiment, preferably, the light source module 100 further includes an on-chip filter module 103. The on-chip filter module 103 is coupled to the output end of the nonlinear micro-ring resonator module 102 through an on-chip optical waveguide. It is used to perform differentiated attenuation and power equalization on each tooth of the original optical frequency comb, resulting in a flat optical frequency comb with a spectral flatness better than 3 dB. In this embodiment, the on-chip filter module 103 is composed of a multi-stage micro-ring resonator array cascaded together. Each micro-ring is independently equipped with a thermo-optical tuning electrode 1031 on its outer side. Through the wavelength selective attenuation characteristics of each filter unit, power equalization is performed on different teeth of the optical frequency comb to suppress power fluctuations of the teeth, resulting in an output spectral flatness better than 3 dB, thereby obtaining a broadband flat optical frequency comb.

[0023] like Figure 4As shown, in the above embodiment, preferably, the SOA intensity modulation module 200 is configured with a pulse drive port for time-domain intensity modulation of the flat optical frequency comb by inputting a periodic electrical drive signal, cutting it into a sequence of optical pulses with a fixed repetition frequency, and simultaneously linearly amplifying the optical pulses. In this embodiment, the SOA intensity modulation module 200 adopts an InP-based semiconductor optical amplifier structure, including a multi-quantum-well active waveguide region 2001 in the middle, and adiabatic tapered transition waveguides 2002 (gradual coupling regions) disposed at both ends of the active waveguide region, and is configured with a pulse drive port. By inputting a periodic electrical drive signal, time-varying gain modulation of the optical signal is achieved, so that the input flat optical frequency comb is gated and cut in the time domain to form a pulse sequence with a stable repetition frequency, while simultaneously linearly amplifying the optical pulses. The adiabatic tapered transition waveguide is used to achieve low-loss mode matching with the passive waveguides on the front and rear chips. The small-signal gain of the SOA is 15-25dB, the modulation bandwidth is not less than 100MHz, and the pulse repetition frequency is 10-40MHz.

[0024] like Figure 5 As shown, in the above embodiment, preferably, the time-correlated phase modulation module 300 includes an electro-optic phase modulator and a pulse driving circuit; the pulse driving circuit outputs a parabolic envelope electrical signal with pre-distortion compensation, applying a secondary time-domain phase to the optical pulse. This achieves time-frequency mapping and introduces linear frequency chirp into the optical pulse. In this embodiment, the electro-optic phase modulator is a thin-film lithium niobate electro-optic phase modulator, which adopts an integrated structure of substrate-waveguide-electrode: substrate 3001 is a lithium niobate thin-film substrate, optical waveguide 3002 is disposed on the surface of substrate 3001 along the light transmission direction, and a pair of modulation electrodes 3003 are symmetrically arranged on both sides of optical waveguide 3002, with modulation voltage interface 3004 led out from the electrode ends. The pulse drive circuit outputs an electrical signal with a parabolic envelope or pre-distortion compensated, which is loaded onto the electrodes through the modulation voltage interface. The electro-optic effect of lithium niobate is used to change the effective refractive index of the waveguide, applying a secondary time-domain phase to the optical pulse. This achieves time-frequency mapping and introduces linear frequency chirping into the optical pulse.

[0025] like Figure 6 As shown, in the above embodiment, preferably, the dispersion compensation and pulse compression unit 400 adopts an on-chip chirped Bragg grating structure and is equipped with a dispersion tuning interface to achieve adjustable negative group delay dispersion compensation, providing adjustable negative group delay dispersion from -5ps² to -50ps², used for temporal focusing and compression of light pulses carrying linear chirps. In this embodiment, the dispersion amount and phase curvature are adjusted to satisfy a matching relationship. This enables the Fourier transform limit compression of chirped pulses.

[0026] In the above embodiments, preferably, the output coupling interface 600 can adopt an end-face coupling structure or a grating coupling structure to stably output the compressed femtosecond pulse.

[0027] In the above embodiments, preferably, the adaptive control unit 500 includes a pulse width stabilization reference input module 501, a mapping algorithm module 502, a phase modulation drive output module 503, a dispersion compensation drive output module 504, and a feedback acquisition interface 505. The mapping algorithm module 502 has a built-in parameter lookup table for the thermal-optical-dispersion coupling drift of the heterogeneous integrated chip. It adopts a dual closed-loop control architecture of feedforward mapping pre-tuning and feedback error correction. Through feedforward mapping, it synchronously outputs phase and dispersion drive signals within ≤10μs, and performs PID closed-loop fine-tuning based on the actual pulse width data acquired through feedback, controlling the output pulse width jitter within 5%. The feedback acquisition interface 505 acquires the output pulse width and spectral data in real time, dynamically compensates for device and environmental drift through closed-loop feedback, and synchronizes phase curvature and dispersion matching parameters in real time to ensure long-term stability of the pulse output.

[0028] In the above embodiments, preferably, all optical functional modules are fabricated on the same photonic chip substrate using a heterogeneous integration process, which is either Si3N4 / InP heterogeneous integration or Si3N4 / TFLN heterogeneous integration; the final output femtosecond pulse has a pulse width range of 100-800 fs, and the pulse width jitter during 24-hour long-term operation is less than 5%.

[0029] Example 2 The present invention provides an on-chip femtosecond pulse generation method based on integrated frequency comb and time-domain phase modulation, which is implemented based on the above-mentioned on-chip femtosecond pulse generation device, comprising: Step S1, Integrated optical frequency comb generation: A spectrally flat, equally spaced multi-longitudinal-mode optical frequency comb is generated and output through the light source module; specifically: Step S11: The RSOA active gain unit 101 generates broadband optical gain under electrical injection driving conditions, and under the external cavity resonance effect formed with the nonlinear micro-ring resonant module 102, it suppresses multi-longitudinal mode oscillation through frequency selective feedback, allowing only wavelengths that meet the resonance conditions to obtain net gain, thereby outputting narrow linewidth single-wavelength pump light. Step S12: Single-wavelength pump light is coupled into the nonlinear micro-ring resonant module 102. Under the high-Q resonance enhancement effect, a four-wave mixing process occurs based on the third-order Kerr nonlinear effect to generate an equally spaced multi-wavelength optical frequency comb. Step S13: The optical frequency comb enters the on-chip filter module 103, where multi-stage filtering units perform differentiated attenuation processing on each comb tooth to achieve spectral power equalization and obtain a broadband flat optical frequency comb. Each microring is independently equipped with a thermo-optical tuning electrode 1031. By individually adjusting the effective refractive index of each microring waveguide, its resonant wavelength is changed, allowing different microrings to lock onto different wavelength comb teeth within the optical frequency comb. Transmission attenuation is independently applied to the corresponding comb teeth, achieving parallel power equalization of the entire comb band.

[0030] Step S2, Temporal Intensity Modulation: The SOA intensity modulation module 200 periodically cuts the flat optical frequency comb to form an optical pulse sequence with a fixed repetition frequency, and simultaneously completes the linear amplification of the optical signal; Step S3, Time-Domain Phase Modulation: Apply a secondary time-domain phase modulation to the optical pulse through the time-correlated phase modulation module 300. By introducing linear frequency chirp, a mapping relationship between the time domain and frequency domain of optical pulses is established; Step S4, Dispersion Matching Compression: Adjustable negative group delay dispersion is provided by the dispersion compensation and pulse compression unit 400 to perform time-domain compression on the optical pulse carrying linear chirp; like Figure 7 As shown, the physical process of optical signal evolution and adaptive matching in this embodiment is as follows: In the direction of optical signal flow, the nanosecond-level initial pulse output in step S2 is subjected to a secondary time-domain phase modulation by the time-correlated phase modulation module 300. Afterward, the pulse amplitude envelope remains unchanged, and the internal instantaneous frequency changes linearly with time, satisfying the relationship... (in (where is the phase curvature coefficient), the corresponding frequency domain spectrum broadens, completing the time-frequency mapping; the light pulse carrying linear chirp then enters the dispersion compensation and pulse compression unit 400, and the negative group delay dispersion applies an inverse group delay to different frequency components.

[0031] In the dimension of control signal coordination Figure 3 The intervention mechanism of the adaptive control unit was also revealed: the adaptive control unit 500 calculates the required phase curvature based on the target pulse width reference. With cumulative dispersion When the system detects an environmental disturbance causing a waveguide thermo-optical effect, the control unit synchronously adjusts the drive voltage of the phase modulator to change the... And simultaneously adjust the tuning interface of the dispersion compensation unit to change When cumulative dispersion With phase curvature Strictly satisfy the matching relationship At this time, all frequency components are perfectly synchronized and focused in the time domain, achieving Fourier transform-limited pulse compression, ultimately compressing the initial nanosecond-level pulse into a femtosecond-level transform-limited pulse. This process demonstrates that optical path dispersion compensation and electrically controlled phase modulation achieve high-precision dynamic spatiotemporal alignment on the on-chip scale.

[0032] Step S5, Adaptive Closed-Loop Control: Real-time acquisition of the pulse width and spectral data of the output pulse, and synchronous adjustment of the phase curvature coefficient. With dispersion ,maintain The Fourier transform limiting matching relationship is used to output a stable transform-limited femtosecond pulse. Step S5 specifically includes: Step S51, Feedforward Pre-configuration: Based on the set target pulse width parameters, call the built-in parameter lookup table to calculate the target phase curvature and target dispersion, and synchronously output the phase modulation drive signal and dispersion compensation drive signal within ≤10μs to complete the parameter feedforward pre-adjustment; like Figure 8 The signal flow diagram of the adaptive control unit shown addresses the phase curvature caused by thermo-optical effects and stress birefringence in on-chip heterogeneous integrated chips (such as Si3N4 / TFLN). and dispersion To address the issue of nonlinear coupling drift, the system employs a dual-loop hardware signal flow architecture with feedforward mapping and feedback correction to compensate for device and environmental drift in real time.

[0033] In the feedforward mapping loop, the pulse width stabilization reference input receives the target pulse width data set by the user and inputs it to the mapping algorithm module 502. The mapping algorithm module 502 has a built-in lookup table (LUT) for the thermal-optical-dispersion coupling drift of heterogeneous integrated chips; the LUT not only stores the ideal state... and The mapping relationship also incorporates real-time data from the on-chip integrated temperature sensor, and corrects the formula in real time. (in Feedforward calculations are performed to compensate for waveguide temperature drift.

[0034] After the calculation is completed, the basic time-dependent phase modulation drive voltage is synchronously output within ≤10μs. With dispersion compensation drive voltage This enables decoupled synchronous pre-tuning of the two channels.

[0035] Step S52, Feedback Fine Correction: Real-time acquisition of the actual pulse width data of the output pulse, error calculation with the target pulse width, fine adjustment of phase and dispersion driving voltage through PID control algorithm, dynamic compensation of device thermal and optical drift and environmental disturbances, and maintenance of long-term stable pulse output.

[0036] In the feedback correction loop, the feedback acquisition interface 505 reads the pulse width and spectral characteristics of the output light pulse in real time through an on-chip integrated photodetector or an autocorrelator coupled to the output. The actual pulse width is then extracted. Then, the target pulse width Error calculations are performed and input into the PID control algorithm module. The PID module outputs a fine-tuning compensation voltage. This voltage is superimposed onto the feedforward loop via hardware adders. and The final driving signal is formed on top. Through the aforementioned signal flow logic of "feedforward fast decoupling pre-tuning + feedback high-precision closed-loop fine-tuning," the system strictly controls the relative pulse width jitter within 5%. This joint matching mechanism, which coordinates the control of optical, electrical, thermal, and dispersion factors on the on-chip scale, effectively overcomes the defect of pulse broadening caused by environmental drift in traditional open-loop systems, ensuring long-term stable operation for 24 hours.

[0037] Finally, a high-quality transform-limited optical pulse sequence with a pulse width in the sub-picosecond to femtosecond range is output through the output coupling interface 600. Through the above structure and working process, this embodiment relies on adaptive closed-loop synchronous control to realize an integrated collaborative mechanism of "optical frequency comb generation - intensity modulation - phase modulation - dispersion matching compression", and obtains low jitter and high stability femtosecond pulse output on a monolithic heterogeneous integrated photonic chip.

[0038] Performance verification and comparative analysis of the examples To verify the key role of the adaptive control mechanism proposed in this invention in maintaining the stability of on-chip femtosecond pulses, this embodiment compares and verifies the device of this invention with a traditional open-loop system based on system-level simulation and theoretical model calculation.

[0039] Simulation test conditions: The ambient temperature was set at 25℃, and the initial output pulse width of the system was compressed to 200 fs. Subsequently, a temperature step disturbance (increasing to 30℃) was introduced, and continuous monitoring was performed for 24 hours.

[0040] Comparative example (traditional open-loop system): adopts the same optical path architecture as the present invention, but removes the adaptive control unit and uses a fixed voltage to drive the phase modulator and dispersion compensation unit. Simulation results and analysis of physical phenomena: 1. Severely widened pulse width: such as Figure 9 As shown, in Comparative Example 1, the increase in temperature causes a thermo-optical shift in the effective refractive index of the Si3N4 / TFLN waveguide (Δn≈1.5×10). -4 ), causing phase curvature A significant shift occurs, while the dispersion compensation is fixed. Unable to update synchronously, matching conditions The system was disrupted. Simulation data shows that the output pulse width of the open-loop system rapidly widens to 1.8 ps after temperature changes, and exhibits irregular pulse width jitter (RMS jitter > 30%) with ambient temperature fluctuations over 24 hours.

[0041] 2. Temporal sidelobe degradation: such as Figure 10 As shown, due to the high-order phase error introduced by dispersion mismatch, the compressed pulse in Comparative Example 1 exhibits significant high-order dispersion sidelobes in the time-domain waveform. Autocorrelation function (ACF) simulations show that the peak power of the sidelobes accounts for more than 18% of the peak power of the main lobe, severely degrading the pulse's peak power and signal-to-noise ratio.

[0042] In the comparative example, the traditional open-loop system exhibits severe pulse width jitter under temperature disturbances, and the time-domain waveform shows serious high-order sidelobe degradation, which cannot meet the requirements of ultrafast optical applications.

[0043] Verification results of the embodiment of the present invention (closed-loop system): Under the same temperature step and continuous operation conditions, the present invention relies on the dual-loop architecture of feedforward mapping + feedback correction. The adaptive control unit corrects the driving voltage through LUT lookup table and temperature compensation formula at the instant of temperature change (≤10μs).

[0044] Simulation data shows that the output pulse width of this invention remains stable within the range of 200±6 fs (RMS jitter <3%), and the pulse width stability during 24-hour long-term operation is as follows: Figure 11 As shown; simultaneously, the time-domain waveform is pure, with a sidelobe suppression ratio better than 22dB (sidelobe power ratio < 0.6%), and the corresponding transform-limiting pulse time-domain waveform is as follows. Figure 12 As shown.

[0045] It can be seen that, under the same temperature step disturbance, the closed-loop system of the present invention exhibits extremely high pulse width locking capability and excellent time-domain waveform quality.

[0046] Overview, combined Figures 9-12 Simulation and theoretical verification data fully demonstrate that this invention is not a simple combination of existing optical devices and conventional electronic feedback, but rather an adaptive matching mechanism for deep coordination of optoelectronic signals, specifically addressing the pain point of "thermal-optical-dispersion coupling drift" unique to on-chip heterogeneous integrated chips. This mechanism has achieved unexpected technical results, possessing outstanding substantive features and significant progress.

[0047] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An on-chip femtosecond pulse generation device based on integrated frequency comb and time-domain phase modulation, characterized in that, The system includes a light source module, an SOA intensity modulation module, a time-correlated phase modulation module, a dispersion compensation and pulse compression unit, and an output coupling interface, which are sequentially coupled and connected along the optical signal propagation direction via on-chip optical waveguides. It also includes an adaptive control unit, which is electrically connected to the time-correlated phase modulation module and the dispersion compensation and pulse compression unit, respectively, and the feedback acquisition terminal of the adaptive control unit is coupled to the output optical path of the output coupling interface. The adaptive control unit is used to acquire the pulse width and spectral characteristic data of the output pulse in real time, and synchronously adjust the phase curvature coefficient of the time-correlated phase modulation module. The dispersion amount of the dispersion compensation and pulse compression unit Maintain dispersion With phase curvature coefficient satisfy The Fourier transform limit matching relationship is used to output a stable transform-limited femtosecond pulse sequence.

2. The on-chip femtosecond pulse generation device according to claim 1, characterized in that, The light source module includes an RSOA active gain unit and a nonlinear microring resonant module. The RSOA active gain unit and the nonlinear microring resonant module are coupled through an on-chip optical waveguide to form an external cavity resonant optical path. The RSOA active gain unit is used to provide broadband optical gain under electrical injection conditions and output stable single-wavelength pump light; the nonlinear microring resonator module is based on the third-order Kerr nonlinear effect to excite a four-wave mixing process and generate an equally spaced multi-longitudinal-mode original optical frequency comb.

3. The on-chip femtosecond pulse generation device according to claim 2, characterized in that, The light source module also includes an on-chip filter module, which is coupled to the output of the nonlinear micro-ring resonator module through an on-chip optical waveguide. The filter module is used to perform differentiated attenuation and power equalization on each tooth of the original optical frequency comb, and outputs a flat optical frequency comb with a spectral flatness better than 3dB.

4. The on-chip femtosecond pulse generation device according to claim 1, characterized in that, The SOA intensity modulation module is configured with a pulse drive port, which is used to perform time-domain intensity modulation on the flat optical frequency comb by inputting a periodic electrical drive signal, cut it into an optical pulse sequence with a fixed repetition frequency, and simultaneously linearly amplify the optical pulse.

5. The on-chip femtosecond pulse generation device according to claim 1, characterized in that, The time-correlated phase modulation module includes an electro-optic phase modulator and a pulse driving circuit; the pulse driving circuit outputs a parabolic envelope electrical signal with pre-distortion compensation, which applies a second-order time-domain phase to the optical pulse. A linear frequency chirp is introduced into the light pulse.

6. The on-chip femtosecond pulse generation device according to claim 1, characterized in that, The dispersion compensation and pulse compression unit adopts an on-chip chirped Bragg grating structure and is equipped with a dispersion tuning interface, providing -5ps. 2 Up to -50ps 2 The tunable negative group delay dispersion is used for temporal focusing and compression of light pulses carrying linear chirps.

7. The on-chip femtosecond pulse generation device according to claim 1, characterized in that, The adaptive control unit includes a pulse width stabilization reference input module, a mapping algorithm module, a phase modulation drive output module, a dispersion compensation drive output module, and a feedback acquisition interface; The mapping algorithm module has a built-in parameter lookup table for the thermal-optical-dispersion coupling drift of the heterogeneous integrated chip. It adopts a dual closed-loop control architecture of feedforward mapping pre-tuning and feedback error correction. Through feedforward mapping, it synchronously outputs phase and dispersion driving signals within ≤10μs, and performs PID closed-loop fine-tuning through the actual pulse width data collected by feedback, controlling the output pulse width jitter within 5%.

8. The on-chip femtosecond pulse generation device according to claim 1, characterized in that, All optical functional modules are fabricated on the same photonic chip substrate using a heterogeneous integration process, which is either Si3N4 / InP heterogeneous integration or Si3N4 / TFLN heterogeneous integration. The device ultimately outputs femtosecond pulses with a pulse width range of 100-800 fs, and the pulse width jitter is less than 5% during 24-hour long-term operation.

9. A method for generating on-chip femtosecond pulses based on integrated frequency comb and time-domain phase modulation, implemented using the on-chip femtosecond pulse generation device according to any one of claims 1-8, characterized in that, include: Step S1: Integrated optical frequency comb generation: A spectrum-flat, equally spaced multi-longitudinal-mode optical frequency comb is generated and output through the light source module; Step S2, Temporal Intensity Modulation: The flat optical frequency comb is periodically intensity-cut by the SOA intensity modulation module to form an optical pulse sequence with a fixed repetition frequency, and the optical signal is linearly amplified simultaneously. Step S3, Time-Domain Phase Modulation: Apply a secondary time-domain phase to the optical pulse through the time-correlated phase modulation module, introduce linear frequency chirp, and establish a mapping relationship between the time domain and frequency domain of the optical pulse; Step S4, Dispersion Matching Compression: Adjustable negative group delay dispersion is provided by dispersion compensation and pulse compression unit to perform time-domain compression on optical pulses carrying linear chirps; Step S5, Adaptive Closed-Loop Control: Real-time acquisition of the pulse width and spectral data of the output pulse, and synchronous adjustment of the phase curvature coefficient. With dispersion ,maintain The Fourier transform limit matching relationship is used to output a stable transform-limited femtosecond pulse.

10. The on-chip femtosecond pulse generation method according to claim 9, characterized in that, Step S5 specifically includes: Step S51, Feedforward Pre-configuration: Based on the set target pulse width parameters, call the built-in parameter lookup table to calculate the target phase curvature and target dispersion, and synchronously output the phase modulation drive signal and dispersion compensation drive signal within ≤10μs to complete the parameter feedforward pre-adjustment; Step S52, Feedback Fine Correction: Real-time acquisition of the actual pulse width data of the output pulse, error calculation with the target pulse width, fine adjustment of phase and dispersion driving voltage through PID control algorithm, dynamic compensation of device thermal and optical drift and environmental disturbances, and maintenance of long-term stable pulse output.

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