Non-linear pulse compression method based on multiple through cavities of annular tire tread and related device

Abstract

The invention relates to the technical field of laser pulse compression, and discloses a nonlinear pulse compression method based on multiple through cavities of an annular tire tread and a related device. Comprising the steps that an annular tire tread multi-way cavity is used as a core device of nonlinear pulse compression, the multi-way cavity adopts a closed annular light path, and a tire tread is machined on the cavity surface, corresponding to an annular cavity, of the annular tire tread multi-way cavity so as to carry out astigmatism correction; a low-chirp or negative-chirp dielectric film or a metal film is plated on the cavity surface of the annular cavity, so that positive chirp or nonlinear chirp is prevented from being introduced during pulse reflection; a solid medium or inert gas is inserted into the annular cavity to serve as a nonlinear medium, so that the nonlinear effect in the multi-way cavity is regulated and controlled; a to-be-compressed pulse is incident into an annular tire tread multi-way cavity, and the reflection frequency of the to-be-compressed pulse in the cavity is changed by adjusting an incident angle, so that the optical path of a nonlinear effect and the nonlinear effect intensity are adjusted; and carrying out dispersion compensation on the pulse which is subjected to nonlinear spectrum broadening through the annular tire tread multi-way cavity, so as to realize pulse compression.

Description

Technical Field

[0001] This application relates to the technical field of laser pulse compression, and particularly to a non - linear pulse compression method and related device based on a multi - pass cavity with a toroidal tire surface. Background Art

[0002] In the technical field of laser pulse compression, the non - linear pulse compression method broadens the pulse spectrum by utilizing the non - linear effect of the medium (such as self - phase modulation), and combines dispersion compensation to achieve the output of ultra - short pulses, which has important application value in industrial processing, precision measurement and scientific research fields. In the prior art, the Herriott Cell, as a typical multi - pass cavity structure, is widely used to construct a non - linear pulse compression system. It realizes multiple reflections of the light beam through multiple groups of reflecting lenses to form a closed optical path to enhance the non - linear effect. However, this scheme has significant defects: First, the Herriott Cell depends on precise adjustment of the incident angle and the mirror spacing. The alignment of the optical path needs to be coordinated with a three - dimensional adjustment frame, which requires extremely high experience from optical engineers, and the debugging complexity and time cost increase significantly. Second, the open - type optical path design is vulnerable to environmental vibration and temperature fluctuations. Vibration causes the light beam to deviate from the reflection path, and temperature changes change the cavity size through thermal expansion, resulting in unstable non - linear effects and optical path mismatch, seriously affecting the repeatability and reliability of pulse compression. Third, the Herriott Cell has strict requirements for the collimation and mode matching degree of the input light beam. The thermal drift of industrial lasers easily leads to a decrease in the cavity efficiency, and its large volume requires external temperature control and pressure stabilization devices, making it difficult to meet the requirements of compact module packaging. The above problems make the Herriott Cell lack stability and have limited adaptability in practical applications, and there is an urgent need for an improved scheme with high stability, easy debuggability and a compact structure.

[0003] In view of the defects of the prior art, those skilled in the art have tried to improve the performance by modifying the multi - pass cavity structure. Although the traditional toroidal cavity has the characteristic of a closed optical path, a single cylindrical reflection will introduce astigmatism, resulting in beam distortion, and the problem of coordinating chirp control and non - linear effect regulation has not been solved.

[0004] Therefore, there is an urgent need for a method to solve at least one of the above problems. Summary of the Invention

[0005] This application provides a non - linear pulse compression method and related device based on a multi - pass cavity with a toroidal tire surface, aiming to solve the problem that those skilled in the art have tried to improve the performance by modifying the multi - pass cavity structure. Although the traditional toroidal cavity has the characteristic of a closed optical path, a single cylindrical reflection will introduce astigmatism, resulting in beam distortion, and the problem of coordinating chirp control and non - linear effect regulation has not been solved.

[0006] In a first aspect, an embodiment of this application provides a non - linear pulse compression method based on a multi - pass cavity with a toroidal tire surface, including:

[0007] Use a toroidal tire - face multi - pass cavity as the core device for non - linear pulse compression. The toroidal tire - face multi - pass cavity adopts a closed - loop optical path, and the cavity surface of the toroidal cavity corresponding to the toroidal cavity is processed with a tire - face for astigmatism correction;

[0008] Deposit a low - chirp or negative - chirp dielectric film or metal film on the cavity surface of the toroidal cavity to avoid introducing positive chirp or non - linear chirp during pulse reflection;

[0009] Insert a solid medium or inert gas into the toroidal cavity as a non - linear medium to regulate the non - linear effect in the multi - pass cavity;

[0010] Inject the pulse to be compressed into the toroidal tire - face multi - pass cavity, and change the number of reflections of the pulse to be compressed in the cavity by adjusting the incident angle, so as to adjust the optical path of the non - linear action and the intensity of the non - linear action;

[0011] Perform dispersion compensation on the pulse that has completed non - linear spectral broadening through the toroidal tire - face multi - pass cavity to achieve pulse compression. Among them, the closed - loop optical path of the toroidal tire - face multi - pass cavity reduces the optical path detuning caused by vibration or temperature fluctuations, and the closed - optical - axis characteristic reduces the debugging complexity of optical path alignment. And at the same optical path, the length of the toroidal tire - face multi - pass cavity is less than that of the traditional Herriott cavity.

[0012] In some embodiments, depositing a low - chirp or negative - chirp dielectric film or metal film on the cavity surface of the toroidal cavity includes: designing the film layer structure of the dielectric film or metal film according to the central wavelength, spectral bandwidth, and target chirp compensation amount of the pulse to be compressed, so that the film layer provides low - chirp or negative - chirp reflection characteristics matching the pulse chirp characteristics within the spectral range of the pulse. Among them, the chirp amount of the negative - chirp film layer forms a complement with the positive chirp introduced by the non - linear effect in the toroidal cavity, so as to synchronously compensate the transmission chirp during the pulse spectral broadening process and reduce the number of external - cavity dispersion compensation elements used.

[0013] In some embodiments, inserting a solid medium or inert gas into the toroidal cavity as a non - linear medium to regulate the non - linear effect in the multi - pass cavity includes: when the non - linear medium is a solid medium, selecting a crystal or glass material with a matched non - linear coefficient, and the size of the solid medium is adapted to the optical path of the toroidal cavity, and regulating the non - linear action intensity by adjusting the refractive index or doping concentration of the solid medium; when the non - linear medium is an inert gas, controlling the gas filling pressure of the toroidal cavity within the range of 10 kPa to 1 MPa, and adjusting the non - linear coefficient by changing the gas type and filling pressure to match the non - linear spectral broadening requirements of pulses with different energies and pulse widths to be compressed.

[0014] In some embodiments, the incident of the pulse to be compressed onto the annular tire surface multi-pass cavity includes: pre-optimizing the beam quality of the pulse to be compressed to ensure the uniformity of the optical field of the incident beam; utilizing the closed optical axis characteristic of the annular tire surface multi-pass cavity to achieve automatic optical path alignment through single-incidence calibration, without relying on a three-dimensional adjustment mount for precise angle adjustment, and reducing the commissioning complexity at the incident end.

[0015] Exemplarily, adjusting the incident angle to change the number of reflections of the pulse to be compressed in the cavity to adjust the optical path and intensity of the nonlinear effect includes: establishing a correspondence model between the incident angle and the number of reflections, and by adjusting the incident angle, making the number of reflections of the pulse to be compressed in the annular tire surface multi-pass cavity dynamically change within a preset range; according to the pulse width after target pulse compression and the requirements of nonlinear spectral broadening, calculating the required number of reflections through the correspondence model and matching the corresponding incident angle to linearly tune the optical path and intensity of the nonlinear effect, so as to flexibly control the pulse width.

[0016] In some embodiments, compensating the dispersion of the pulse that has completed nonlinear spectral broadening through the annular tire surface multi-pass cavity to achieve pulse compression includes: using a pair of chirped mirrors for dispersion compensation, and the single-chip chirp amount of the pair of chirped mirrors is designed to match according to the pre-compensation chirp amount of the annular cavity film layer and the pulse bandwidth after spectral broadening, wherein the total accumulated compensated dispersion amount cancels out the positive dispersion and transmission chirp introduced during the nonlinear spectral broadening process of the pulse; when the negative chirp provided by the annular cavity film layer has partially compensated the pulse chirp, reducing the number of lenses of the pair of chirped mirrors, so that the total dispersion amount compensation can be completed with only 1-2 chirped mirrors in the dispersion compensation process, simplifying the structure of the dispersion compensation system.

[0017] In some embodiments, before compensating the dispersion of the pulse that has completed nonlinear spectral broadening through the annular tire surface multi-pass cavity, it further includes: correcting the astigmatism during the beam transmission process using the tire surface to improve the output beam quality; compensating the chirp during the pulse spectral broadening process through the low-chirp or negative-chirp dielectric film or metal film to reduce the number of external cavity chirped mirrors used.

[0018] In a second aspect, the present application provides a nonlinear pulse compression device based on an annular tire surface multi-pass cavity, and the device includes:

[0019] An astigmatism correction unit for using an annular tire surface multi-pass cavity as a core device for nonlinear pulse compression, the annular tire surface multi-pass cavity adopting a closed annular optical path, and the cavity surface of the annular cavity corresponding to the annular tire surface is processed for astigmatism correction;

[0020] The cavity surface coating unit is used to coat a low-chirp or negative-chirp dielectric film or metal film on the cavity surface of the annular cavity to avoid introducing positive chirp or nonlinear chirp during pulse reflection;

[0021] The dielectric insertion unit is used to insert a solid dielectric or inert gas into the annular cavity as a nonlinear dielectric to regulate the nonlinear effect in the multi-pass cavity;

[0022] The pulse incident unit is used to incident the pulse to be compressed into the annular toroidal multi-pass cavity, and change the number of reflections of the pulse to be compressed in the cavity by adjusting the incident angle, so as to adjust the optical path and intensity of the nonlinear effect;

[0023] The compression implementation unit is used to perform dispersion compensation on the pulse that has completed nonlinear spectral broadening through the annular toroidal multi-pass cavity to achieve pulse compression; wherein, the closed annular optical path of the annular toroidal multi-pass cavity reduces the optical path detuning caused by vibration or temperature fluctuation, and the closed optical axis characteristic reduces the debugging complexity of optical path alignment, and at the same optical path, the length of the annular toroidal multi-pass cavity is less than that of the traditional Herriott cavity.

[0024] In a third aspect, an embodiment of the present application provides a control module, which includes a memory and a processor. The memory is used to store a computer program, and the processor is used to execute the computer program and implement the method provided in any embodiment of the present application when executing the computer program.

[0025] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the processor is caused to implement the method provided in any embodiment of the present application.

[0026] The non - linear pulse compression method and related device based on a multi - pass cavity with an annular tire surface provided by the embodiments of the present application achieve efficient pulse compression through innovative cavity structures and regulation mechanisms. Specifically, an annular tire - surface multi - pass cavity is adopted, which is characterized in that: the closed annular optical path is different from the open optical path of the traditional Herriott cavity, forming a closed path for the cyclic propagation of light beams. The tire - surface processing is to process the tire - surface structure on the cavity surface of the annular cavity, which is used to correct the astigmatism during the light - beam transmission process and improve the output beam quality. A low - chirp or negative - chirp dielectric film / metal film is plated on the cavity surface of the chirped film layer to avoid introducing positive chirp or non - linear chirp due to reflection, and synchronously compensate the chirp effect in the pulse spectral broadening. A solid medium (such as a non - linear crystal) or an inert gas is inserted into the cavity, and the non - linear coefficient is adjusted through material properties (refractive index, doping concentration) or gas parameters (type, pressure) to enhance the non - linear spectral broadening efficiency. By adjusting the incident angle, the number of reflections of the pulse in the cavity is dynamically changed (from 4 passes to 16 passes), linearly adjusting the optical path and intensity of the non - linear effect to achieve flexible control of the pulse width. Utilizing the characteristics of the closed optical axis simplifies the optical path alignment and reduces the debugging complexity; under the same optical path, the cavity length is only 1 / 4 of that of the Herriott cavity, supporting compact packaging; combined with chirp compensation of the film layer, the number of extracavity dispersion elements (such as the number of chirped mirrors) is reduced. The pulse to be compressed is incident after pre - optimization (beam quality M² ≤ 1.1), undergoes non - linear spectral broadening through the annular cavity, and then compensates for the dispersion through a pair of chirped mirrors, finally achieving pulse compression.

[0027] The provided method has at least the following beneficial effects:

[0028] Solving the problem of high debugging difficulty: The characteristics of the closed optical axis support single - incident automatic alignment, without relying on precise adjustment of the incident angle and mirror spacing by a three - dimensional adjustment frame, significantly reducing the dependence on the experience of engineers and shortening the debugging time.

[0029] Improving the long - term working stability: The closed annular optical path isolates external vibration interference, preventing the light beam from deviating from the reflection path; the cavity structure is less affected by temperature fluctuations (without the thermal - expansion optical - path mismatch of the open optical path), and the stability of non - linear effects (such as self - phase modulation) is greatly improved, and the pulse - width fluctuation of the output pulse is significantly reduced.

[0030] Achieving compact modular packaging: Under the same optical path, the cavity length is only 1 / 4 of that of the Herriott cavity, without the need for external temperature - control / pressure - stabilization devices, facilitating integrated design and meeting the requirements of industrial scenarios for miniaturized and highly reliable modules.

[0031] Optimizing the beam quality and compression efficiency: The tire - surface structure corrects astigmatism, avoiding beam distortion caused by single - cylindrical - surface reflection in the traditional annular cavity; the negative - chirp film layer synchronously compensates for the chirp introduced by reflection, reducing extracavity dispersion - compensation elements, simplifying the system structure while improving the phase consistency, and significantly optimizing the uniformity of the compressed - pulse spectral broadening and the beam quality (M² factor).

[0032] Enhance the tuning flexibility of the nonlinear effect: By dynamically adjusting the number of reflections (4 - 16 passes) with the incident angle and combining the parameter control of solid / gas nonlinear media (such as gas pressure from 10 kPa to 1 MPa), it is possible to linearly match input pulses with different energies and pulse widths, achieve precise control of the nonlinear interaction intensity, and support a wide range of tuning of the pulse width.

[0033] Lower the threshold for industrial applications: Reduce the requirement for the mode matching degree of the input beam (no strict collimation is required), be compatible with the mode changes caused by the thermal drift of industrial lasers, and the cavity efficiency is stable; The collaborative design of chirped film layers and chirped mirror pairs reduces the complexity of the dispersion compensation module and improves the robustness of the system.

[0034] In summary, through the systematic innovation of "closed annular optical path + tire - surface astigmatism correction + chirped film layer compensation + nonlinear medium tuning", the present invention breaks through the bottlenecks of traditional Herriott cavities in terms of debugging difficulty, environmental stability, and volume, providing a compression solution with high performance, easy integration, and high adaptability for high - power ultrashort - pulse laser systems, especially suitable for industrial processing and scientific research scenarios with strict requirements for stability and compactness.

[0035] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit this application. Description of the Drawings

[0036] To more clearly illustrate the technical solutions of the embodiments of this application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0037] Figure 1 It is a schematic flow chart of the steps of a nonlinear pulse compression method based on a ring - shaped tire - surface multi - pass cavity provided by an embodiment of this application;

[0038] Figure 2 It is the first structural schematic diagram of a ring - shaped cavity provided by an embodiment of this application;

[0039] Figure 3 It is the second structural schematic diagram of a ring - shaped cavity provided by an embodiment of this application;

[0040] Figure 4 It is the third structural schematic diagram of a ring - shaped cavity provided by an embodiment of this application;

[0041] Figure 5 It is the fourth structural schematic diagram of a ring - shaped cavity provided by an embodiment of this application;

[0042] Figure 6 It is the 5th structural schematic diagram of an annular cavity provided by an embodiment of the present application;

[0043] Figure 7 It is the 6th structural schematic diagram of an annular cavity provided by an embodiment of the present application;

[0044] Figure 8 It is the schematic diagram of the pulse compression effect provided by an embodiment of the present application;

[0045] Figure 9 It is the schematic diagram of the characterization result of the compressed pulse provided by an embodiment of the present application;

[0046] Figure 10 It is the structural schematic block diagram of a non - linear pulse compression device based on a multi - pass cavity of an annular tire surface provided by an embodiment of the present application;

[0047] Figure 11 It is the structural schematic block diagram of the control module provided by an embodiment of the present application.

[0048] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. Specific Embodiments

[0049] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0050] The flowcharts shown in the accompanying drawings are only illustrative examples, and do not necessarily include all contents and operations / steps, nor do they necessarily need to be executed in the described order. For example, some operations / steps can also be decomposed, combined, or partially merged. Therefore, the actual execution order may be changed according to the actual situation.

[0051] It should be understood that in order to facilitate the clear description of the technical solutions in the embodiments of the present invention, in the embodiments of the present invention, terms such as "first" and "second" are used to distinguish the same items or similar items with basically the same functions and effects. Those skilled in the art can understand that the terms "first", "second", etc. do not limit the quantity and execution order, and the terms "first", "second", etc. do not necessarily mean different.

[0052] It should be understood that the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. As used in the specification of this application and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include the plural forms.

[0053] It should also be understood that the term "and / or" used in the specification of this application and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0054] The following will, with reference to the accompanying drawings, elaborate on some embodiments of this application. Without conflict, the following embodiments and the features in the embodiments may be combined with each other.

[0055] In the field of laser pulse compression technology, the nonlinear pulse compression method broadens the pulse spectrum by utilizing the nonlinear effect of the medium (such as self-phase modulation), and combines dispersion compensation to achieve the output of ultra-short pulses, which has important application value in the fields of industrial processing, precision measurement and scientific research. In the prior art, the Herriott Cell, as a typical multi-pass cavity structure, is widely used to construct a nonlinear pulse compression system, which realizes multiple reflections of the light beam through multiple groups of reflecting lenses to enhance the nonlinear effect. However, this solution has significant defects: firstly, the Herriott Cell depends on precise adjustment of the incident angle and the mirror spacing, and the optical path alignment needs to be coordinated with a three-dimensional adjustment frame, which requires extremely high experience of optical engineers, and the debugging complexity and time cost are significantly increased; secondly, the open optical path design is easily affected by environmental vibration and temperature fluctuations. Vibration causes the light beam to deviate from the reflection path, and temperature changes change the cavity size through thermal expansion, resulting in unstable nonlinear effects and optical path mismatch, seriously affecting the repeatability and reliability of pulse compression; thirdly, the Herriott Cell has strict requirements for the collimation and mode matching degree of the input light beam, and the thermal drift of industrial lasers easily leads to a decrease in the cavity efficiency, and its large volume needs to be equipped with external temperature control and pressure stabilization devices, which is difficult to meet the requirements of compact module packaging. The above problems make the Herriott Cell lack stability and have limited adaptability in practical applications, and there is an urgent need for an improved solution with high stability, easy debuggability and a compact structure.

[0056] In view of the defects of the prior art, those skilled in the art have tried to improve the performance by improving the multi-pass cavity structure. Although the traditional ring cavity has the characteristics of a closed optical path, a single cylindrical reflection will introduce astigmatism, resulting in beam distortion, and the problem of coordinating chirp control and nonlinear effect regulation has not been solved.

[0057] Therefore, there is an urgent need for a method to solve at least one of the above problems.

[0058] To solve the above content, please refer to Figures 1 to 7(In Figures 2 - 7 , 1 is a ring cavity, 2 is a chirped mirror, 3 is a nonlinear medium, 3.1 is a solid nonlinear medium, 3.2 is a gas nonlinear medium, and 4 is an astigmatism-corrected toroidal surface), an embodiment of the present application provides a nonlinear pulse compression method based on a ring toroidal multi-pass cavity, which is applied to a control module. Specifically, as shown in Figure 1 , the provided nonlinear pulse compression method based on a ring toroidal multi-pass cavity includes steps S101 to S105. Details are as follows:

[0059] Step S101. Use a ring toroidal multi-pass cavity as the core device for nonlinear pulse compression. The ring toroidal multi-pass cavity adopts a closed ring optical path, and a toroidal surface is machined on the cavity surface corresponding to the ring cavity for astigmatism correction.

[0060] Specifically, a ring toroidal multi-pass cavity with a closed ring optical path structure is used as the core device for nonlinear pulse compression. A toroidal surface (Torus Surface) structure is machined on the cavity surface (reflective surface) of the ring cavity to correct the astigmatism generated during multiple reflections of the light beam. The toroidal surface is an aspherical surface with different radii of curvature in two orthogonal directions, which can compensate for the astigmatism distortion caused by the single cylindrical surface reflection of the traditional ring cavity.

[0061] The ring cavity adopts a closed ring optical path, which is surrounded by multiple mirrors to form a closed path (such as a circular, elliptical or polygonal closed loop). The light beam circulates along the closed optical axis in the cavity. A toroidal surface structure is precisely machined on the surface of the mirrors in the ring cavity (single cylindrical surface or multiple cylindrical surfaces). The surface parameters of the curved surface are optimized through optical design software (such as Zemax) to effectively correct the astigmatism (such as coma and field curvature) of the light beam during reflection. The mirror substrate can be made of low-expansion coefficient materials such as fused quartz, silicon or metal (such as aluminum) to ensure the stability of the surface accuracy during long-term use.

[0062] The traditional ring cavity uses a single cylindrical mirror, resulting in spot distortion of the light beam due to astigmatism after multiple reflections, which affects the beam quality of the compressed pulse; the toroidal surface structure compensates for the astigmatism in the orthogonal directions through an aspherical surface, ensuring that the light beam still maintains high uniformity and collimation after multiple reflections in the cavity. Different from the open optical path of the Herriott cavity, the closed optical path structure of the ring cavity reduces the interference of external vibration and air flow on the optical path alignment, significantly reducing the risk of optical path misalignment. The characteristic of the closed optical axis makes the propagation path of the light beam in the cavity symmetric, eliminating the need to rely on a three-dimensional adjustment frame for precise angle calibration, and greatly reducing the debugging complexity compared with the Herriott cavity.

[0063] Step S102. Coat a low-chirp or negative-chirp dielectric film or metal film on the cavity surface of the ring cavity to avoid introducing positive chirp or nonlinear chirp during pulse reflection.

[0064] Specifically, by depositing a low-chirp dielectric film or metal film, or a negative-chirp dielectric film or metal film on the mirror surface of the ring cavity, the chirp introduced during pulse reflection (i.e., the time delay difference of different frequency components of the pulse) is offset by the dispersion characteristics of the film layer, avoiding the interference of positive chirp or nonlinear chirp on subsequent pulse compression.

[0065] According to the pulse center wavelength (such as 1030 nm) and spectral range (such as 1010–1045 nm), a multi-layer dielectric film (such as a SiO2 / TiO2 combination) or metal film (such as a gold-plated film) is prepared by ion beam sputtering or electron beam evaporation technology. By optimizing the film layer thickness and material refractive index, the target chirp amount (such as negative chirp amount to compensate for the dispersion during the reflection process) is achieved. Considering the cumulative effect of multiple reflections of the pulse in the cavity, the group delay dispersion (GDD) parameter of the film layer is designed to make the chirp amount introduced by a single reflection negative or close to zero, ensuring that the total chirp amount is controllable after multiple reflections.

[0066] In the traditional Herriott cavity, the reflection chirp is not controlled, resulting in phase distortion during the pulse spectral broadening process, which affects the compression efficiency. In this step, through film layer dispersion compensation, the accumulation of positive chirp or nonlinear chirp is avoided, ensuring the pulse phase consistency. The negative chirp film layer can partially compensate for the intracavity dispersion, reducing the number of chirped mirrors required for subsequent dispersion compensation, simplifying the system structure and reducing costs.

[0067] Step S103. Insert a solid medium or inert gas into the ring cavity as a nonlinear medium to regulate the nonlinear effect in the multi-pass cavity.

[0068] Specifically, a solid medium (such as Yb:YAG crystal, fused quartz) or inert gas (such as argon, krypton) is inserted into the ring multi-pass cavity as a nonlinear medium. Through the nonlinear optical effect of the medium (such as self-phase modulation), the pulse spectral broadening is enhanced, and the nonlinear action intensity is adjusted by the medium type and filling parameters.

[0069] The solid medium can fix a bulk nonlinear crystal (such as β-BBO, Yb:YAG) or undoped transparent solid (such as fused quartz) in the cavity, and utilize its high nonlinear coefficient (such as γ value) to achieve strong nonlinear action, which is suitable for high-energy pulse compression. The gas medium can build a sealed gas chamber in the cavity, fill it with an inert gas (such as argon) and adjust the air pressure (such as 1–10 atm). Through the low damage threshold and adjustable nonlinear coefficient of the gas, it can adapt to the low-energy, high-repetition frequency pulse scenario. The medium layout can place the nonlinear medium at the position of the optical waist in the cavity (where the beam radius is the smallest) to maximize the nonlinear action efficiency; the solid medium can be maintained at a constant temperature by a temperature control device, and the gas medium can monitor the air pressure in real time through a pressure sensor and feedback for adjustment.

[0070] Different from the Herriott cell which relies on a fixed optical path length to regulate the nonlinear effect, this step realizes the dynamic tuning of the nonlinear coefficient (γ) by changing the medium type (solid / gas) or adjusting the gas pressure and solid temperature to meet the compression requirements for different input pulse parameters (energy, pulse width). Solid media are suitable for high-power scenarios, and gas media are suitable for low-damage scenarios, broadening the application scope of the compression method (such as industrial processing, precision measurement).

[0071] Step S104. Incident the pulse to be compressed onto the annular tire-surface multipass cell, and change the number of reflections of the pulse to be compressed in the cell by adjusting the incident angle, so as to adjust the optical path of the nonlinear effect and the intensity of the nonlinear effect.

[0072] Specifically, by incidenting the pulse to be compressed onto the annular tire-surface multipass cell at a specific angle and changing the number of reflections of the pulse in the cell by adjusting the incident angle, the optical path of the nonlinear effect (i.e., the total distance that the light beam propagates in the nonlinear medium) can be controlled, realizing the flexible adjustment of the intensity of the nonlinear effect.

[0073] The incident angle adjustment mechanism is provided with a two-dimensional precision turntable (such as an electric rotary table with an accuracy of ±0.01°) at the input end of the cell, and dynamically adjusts the included angle θ between the incident light beam and the cell surface through a servo system. The number of reflections is related to the optical path: according to the geometric parameters of the annular cell (such as radius R, curvature radius r of the cell surface), a mathematical model of the incident angle θ and the number of reflections N is established (such as N∝1 / θ, based on the geometric optical reflection law), and the quantitative adjustment of N (such as 8-pass, 12-pass reflections) is realized by controlling θ.

[0074] Compared with the limitation of the fixed number of reflections of the Herriott cell, this step realizes continuously adjustable optical path through angle adjustment, thereby linearly controlling the degree of pulse spectral broadening (Δλ∝optical path×nonlinear coefficient), facilitating the output of compressed pulses with different pulse widths as required (such as from hundreds of femtoseconds to sub-picosecond order). The closed annular optical path has lower requirements for the collimation of the input light beam than the Herriott cell, and the mode change caused by the thermal drift of the industrial laser has a significantly reduced impact on the cell efficiency, improving the robustness of the system in complex environments.

[0075] Step S105. Perform dispersion compensation on the pulse that has completed nonlinear spectral broadening through the annular tire-surface multipass cell to realize pulse compression; wherein, the closed annular optical path of the annular tire-surface multipass cell reduces the optical path detuning caused by vibration or temperature fluctuation, and the closed optical axis characteristic reduces the debugging complexity of optical path alignment, and at the same optical path, the length of the annular tire-surface multipass cell is less than that of the traditional Herriott cell.

[0076] Specifically, for the pulse that has completed nonlinear spectral broadening through the ring cavity, group velocity dispersion (GVD) compensation is performed using chirped mirrors or other dispersion compensation devices to eliminate the time delay of different frequency components of the pulse and achieve the output of ultrashort pulses. Among them, the negative chirp film layer of the ring cavity can pre-compensate for part of the dispersion and reduce the external compensation amount.

[0077] The chirped mirror configuration forms a mirror pair by using two or more chirped mirrors (such as the mirrors with negative chirp film layers described in step S102). The chirp amount of a single chip is designed to be -1000 fs² @ 1030 nm, and the total dispersion compensation amount is accumulated through multiple reflections (such as achieving a total chirp compensation of -8000 fs² through 8-pass reflections). Based on the bandwidth after pulse spectral broadening (such as 1010–1045 nm) and the accumulated dispersion in the cavity (including nonlinear chirp and film layer dispersion), the compensation strategy is optimized through the Fourier transform method or numerical simulation to ensure that second-order and higher-order dispersions are effectively corrected.

[0078] Combining the pre-compensation of the negative chirp film layer in the cavity with the secondary compensation of the chirped mirror pair outside the cavity, phase-matched compression of the spectrally broadened pulse is achieved. Compared with the Herriott cavity scheme, the compression efficiency is increased by more than 30% (such as compressing the initial pulse width of 700 fs to the sub-100 femtosecond level). The closed optical path of the ring cavity is only 1 / 4 of the length of the Herriott cavity under the same optical path. Combining with the reduced number of external chirped mirrors, the overall system volume is reduced by more than 50%, meeting the requirements of industrial module packaging for compactness. The closed optical path structure reduces the influence of temperature fluctuations on the optical path (without an external temperature control device), and the risk of optical path detuning caused by vibration interference is significantly reduced. The fluctuation range of the output pulse width is reduced from ±15% in the traditional scheme to within ±5%.

[0079] In summary, this method systematically solves the inherent defects of the Herriott cavity, such as complex debugging, environmental sensitivity, and large volume, through three core technologies: the innovation of the ring toroidal multi-pass cavity structure (solving astigmatism and optical path stability), the collaborative regulation of chirped film layers and nonlinear media (optimizing phase matching and nonlinear effects), and the dynamic tuning of the reflection times by the incident angle (flexibly controlling compression parameters). It provides a breakthrough solution for industrial-grade high-stability pulse compression equipment and has significant technological progress and practical value.

[0080] In some embodiments, depositing a low-chirp or negative-chirp dielectric film or metal film on the cavity surface of the ring cavity includes: designing the film layer structure of the dielectric film or metal film according to the central wavelength, spectral bandwidth, and target chirp compensation amount of the pulse to be compressed, so that the film layer provides low-chirp or negative-chirp reflection characteristics that match the chirp characteristics of the pulse within the spectral range of the pulse; among them, the chirp amount of the negative chirp film layer forms a complement with the positive chirp introduced by the nonlinear effect in the ring cavity to synchronously compensate for the transmission chirp during the pulse spectral broadening process and reduce the number of external dispersion compensation elements used.

[0081] The input of film layer design parameters is based on the central wavelength of the pulse to be compressed (e.g., 1030 nm), the spectral bandwidth (e.g., broadened to 1010–1045 nm), and the target chirp compensation amount (e.g., -500 fs chirp amount for single-pass reflection). A multi-layer film system model is established using thin-film design software (e.g., TFCalc). 2 chirp amount), and a multi-layer film system model is established using thin-film design software (e.g., TFCalc).

[0082] For dielectric films, high refractive index materials (TiO2, n≈2.3) and low refractive index materials (SiO2, n≈1.46) are alternately deposited. The group delay dispersion (GDD) at different wavelengths is controlled by adjusting the thickness of each layer (with nanometer-level precision). For metal films, gold films are selected and dielectric protective layers are evaporated on the surface to optimize the chirp characteristics in the ultraviolet to near-infrared bands.

[0083] The chirp complementary strategy includes analyzing the positive dispersion introduced by nonlinear effects (such as self-phase modulation) (the high-frequency components of the pulse lag behind the low-frequency components), designing the single-pass reflection chirp amount of the negative chirp film layer (e.g., -1000 fs²@1030 nm), so that it forms an algebraic cancellation with the intracavity nonlinear positive dispersion after multiple reflections (e.g., the cumulative negative chirp of 8-pass reflection is -8000 fs², canceling the nonlinear positive dispersion of +6000 fs², and the remaining -2000 fs² is compensated by an extracavity chirped mirror).

[0084] The preparation process deposits the film layer by using the ion beam sputtering (IBS) technique, monitors the thickness with a quartz crystal oscillator to ensure that the film layer uniformity error is <1%. After coating, a spectrometer (e.g., Agilent Cary 5000) and a GDD measuring instrument (e.g., Femtolasers SPIDER) are used to calibrate the reflectivity (>99.8%) and the chirp amount (error <5%).

[0085] Through the quantitative matching of film layer parameters and nonlinear effects, the phase distortion caused by the uncontrolled reflection chirp in the traditional Herriott cavity is avoided, ensuring that "broadening - chirp compensation" is synchronized during the pulse spectral broadening process. The time-bandwidth product of the compressed pulse is closer to the transform limit (increased to more than 95% of the theoretical value). The negative chirp film layer pre-compensates for some dispersion, reducing the number of lenses in the extracavity chirped mirror pair from 4 in the traditional scheme to 2 or even 1, reducing the optical path debugging difficulty and device cost, and at the same time reducing the vibration-sensitive points introduced by external components. The wide-spectrum high-reflection characteristics of the film layer (e.g., reflectivity >99.5% at 1010–1045 nm) adapt to the wavelength drift (±5 nm) of industrial lasers, avoiding the reduction of compression efficiency caused by mode mismatch, and improving the output pulse energy stability from ±8% in the traditional scheme to ±3%.

[0086] In some embodiments, inserting a solid medium or an inert gas into the ring cavity as a nonlinear medium to regulate the nonlinear effect in the multi-pass cavity includes: when the nonlinear medium is a solid medium, selecting a crystal or glass material with a matching nonlinear coefficient, where the size of the solid medium is adapted to the optical path of the ring cavity, and regulating the nonlinear interaction intensity by adjusting the refractive index or doping concentration of the solid medium; when the nonlinear medium is an inert gas, controlling the gas filling pressure of the ring cavity within the range of 10 kPa to 1 MPa, and adjusting the nonlinear coefficient by changing the gas type and filling pressure to match the nonlinear spectral broadening requirements of the pulses to be compressed with different energies and pulse widths.

[0087] The implementation method of the solid medium includes: material selection and adaptation: selecting a crystal (such as β-BBO, γ≈5×10⁻²³ m² / W) or glass (such as tellurite glass, γ≈2×10⁻² 0 m² / W) with a relatively high nonlinear coefficient γ, designing the medium size (such as diameter 10 mm and length 20 mm) according to the optical path radius of the ring cavity (such as 50 mm) to ensure that the medium completely covers the optical waist area (beam radius <500 μm). Adjust the refractive index of the material by doping concentration regulation (such as Yb³⁺ ion concentration 0.1%–1%) or temperature control (accuracy ±0.1°C), and then adjust the nonlinear interaction intensity (Δγ / γ≤10%).

[0088] Fixing and temperature control: Fix the solid medium by using a support with a low coefficient of thermal expansion (such as invar), wrap a semiconductor refrigeration sheet around it, and maintain the temperature of the medium stable through a PID controller to avoid beam distortion caused by the thermal lens effect.

[0089] The implementation method of the inert gas medium includes: gas chamber construction and control: integrating a sealed gas chamber (volume 100–500 cm 3 ) inside the ring cavity, equipped with a pressure sensor (accuracy ±0.1% FS) and a pneumatic pressure regulating valve, supporting a pressure range of 10 kPa (low pressure) to 1 MPa (high pressure). Optional gases include argon (low damage threshold, suitable for low-energy pulses), krypton (high nonlinear coefficient, suitable for high-energy pulses), and rapid switching of gas types can be achieved through a mass flow controller (accuracy ±0.5%).

[0090] Nonlinear coefficient tuning involves utilizing the fact that the nonlinear coefficient γ ∝ gas density (γ = γ0×P / P0, where P0 is the standard atmospheric pressure), linearly controlling the value of γ by adjusting the gas pressure (e.g., γ = 0.1γ0 at 10 kPa and γ = 10γ0 at 1 MPa), and matching the broadening requirements of different energy pulses (e.g., a 1 mJ pulse corresponds to 0.5 MPa argon, and a 0.1 mJ pulse corresponds to 50 kPa argon). Solid media are suitable for high-energy (>1 mJ), narrow-pulse-width (>500 fs) pulse compression to avoid ionization damage to gas media; gas media are suitable for low-energy (<100 μJ), high-repetition-rate (>100 kHz) scenarios to solve the heat accumulation problem of solid media, enabling the compression method to cover the requirements of multiple fields such as industrial processing (high energy) and scientific measurement (low noise). By continuously adjusting the doping concentration / temperature of the solid medium or the gas pressure, a 10-fold dynamic range of the nonlinear interaction strength is achieved (γ = 1×10 -23 to 1×10 -22 m 2 / W). Compared with the limitation of the fixed nonlinear coefficient of the Herriott cavity, the compression parameters can be quickly optimized according to the output characteristics of different lasers (such as fiber lasers vs solid lasers), and the compression efficiency is increased by 20%–50%. The temperature control design of the solid medium suppresses the optical path change caused by thermal expansion (ΔL / L < 10 -6 / °C), and the sealed gas chamber of the gas medium avoids the influence of external contamination (such as dust) on the nonlinear effect. The trouble-free operation time of the system is increased from 500 hours in the traditional scheme to more than 2000 hours.

[0091] In some embodiments, the incident of the pulse to be compressed on the annular tire surface multipass cavity includes: pre-optimizing the beam quality of the pulse to be compressed to ensure the uniformity of the optical field of the incident beam; utilizing the closed optical axis characteristic of the annular tire surface multipass cavity to achieve automatic optical path alignment through single-incidence calibration, without relying on a three-dimensional adjustment frame for precise angle adjustment, and reducing the debugging complexity at the incident end.

[0092] The pre-optimization of the beam quality is achieved by integrating a beam shaping system at the output end of the laser, which includes a beam expander group (magnification 2–5 times) and a mode filter (such as a single-mode fiber or a spatial filter), optimizing the M 2 factor of the incident beam to <1.1 (close to the diffraction limit), and ensuring the uniformity of the optical field by real-time monitoring of the spot ellipticity (axial ratio <1.2) through a CCD beam analyzer.

[0093] Closed optical axis automatic alignment utilizes the geometric symmetry of the ring cavity (such as the coincidence of the optical axis of the circular cavity and the central axis of the cavity), designs a fixed-angle bracket at the incident end (accuracy ±0.1°), and only requires single-incidence calibration: monitor the energy at the output end of the cavity through a photodetector, and finely adjust the incident angle to the maximum energy (automatically lock the optimal incident angle), without the need for the three-dimensional adjustment frame (±5° adjustment of X / Y / Z axes) and long-term empirical debugging relied on by traditional Herriott cavities.

[0094] For traditional Herriott cavities, optical engineers need to adjust the three-dimensional angles with micrometer-level accuracy, which takes several hours; in this embodiment, through the characteristics of the closed optical axis and energy feedback for automatic alignment, the debugging time is shortened to within 10 minutes, and professional experience is not required, significantly reducing labor costs and being suitable for batch calibration in industrial production lines. The thermal drift of industrial lasers (such as a beam pointing drift of ±5 mrad caused by a 10°C temperature change) has a much smaller impact on the ring cavity than on the Herriott cavity - the angular tolerance of the closed optical path (±2°) is 20 times that of the open optical path (±0.1°). Even if the beam pointing drifts, the non-linear interaction efficiency can still be maintained through the remaining number of reflections, and the decrease in the cavity efficiency is reduced from 40% in the traditional scheme to <10%. M 2 An incident light beam with a <1.1 factor ensures that the spot distortion rate is <5% after reflection on the tire surface, avoiding local over-strength / over-weakness of the non-linear effect caused by uneven light fields and improving the spatio-temporal quality of the compressed pulse (the energy ratio of the time-domain sidelobe <5%).

[0095] Exemplarily, adjusting the incident angle changes the number of reflections of the pulse to be compressed in the cavity to adjust the optical path and intensity of the non-linear interaction, including: establishing a correspondence relationship model between the incident angle and the number of reflections, and by adjusting the incident angle, making the number of reflections of the pulse to be compressed in the multi-pass cavity of the annular tire surface change dynamically within a preset range; according to the pulse width after target pulse compression and the non-linear spectral broadening requirements, calculating the required number of reflections through the correspondence relationship model and matching the corresponding incident angle to linearly tune the optical path and intensity of the non-linear interaction to achieve flexible control of the pulse width.

[0096] The mathematical model is established based on geometric optics to establish a relationship formula between the incident angle θ and the number of reflections N for the ring cavity (radius R): N = 2πR / d*sinθ; where d is the arc length interval between adjacent reflection points (a fixed value), and θ is the angle between the incident light beam and the tangent of the cavity surface (0° < θ < 90°). Calibrate the model through an optical simulation software (such as LightTools) to ensure that the calculation error of N is <1%.

[0097] An electric rotary stage (resolution 0.001°) is installed at the incident end, connected to the control system to read the target pulse width in real time (e.g., it takes N = 8 passes to compress from 500 fs to 100 fs), θ = 15° is obtained by back-calculation, and the rotary stage is driven to automatically position. It supports continuous adjustment of the reflection times within the range of 4 - 16 passes, corresponding to the dynamic change of the nonlinear optical path from 0.5 m to 2 m.

[0098] Quantitative control of the reflection times N is achieved through angle adjustment, and then the nonlinear optical path is linearly tuned (L = N×l, where l is the optical path of a single reflection), so that the spectral broadening amount Δλ ∝ L×γ (γ is the nonlinear coefficient), and finally precise control of the compressed pulse width τ ∝ 1 / Δλ is realized (e.g., the target pulse width of 100 fs corresponds to Δλ = 35 nm, and 200 fs corresponds to Δλ = 17 nm), and the tuning accuracy reaches ±5 fs. For a traditional Herriott cavity, replacing the reflection times requires manual replacement of the lens group (time-consuming > 30 minutes). In this embodiment, the reflection times can be switched within seconds through the electric rotary stage, adapting to multi-task scenarios (such as the same device alternately processing material cutting and surface treatment, requiring different pulse width outputs), and the production efficiency is increased by more than 3 times. A relatively large incident angle adjustment range allows a certain divergence angle of the incident beam (such as ±1 mrad), reducing the accuracy requirements for the laser collimation system (the focal length of the collimating mirror can be relaxed from 500 mm in the traditional scheme to 200 mm), and further reducing the hardware cost.

[0099] In some embodiments, dispersive compensation is performed on the pulses that have completed nonlinear spectral broadening through the multi-pass cavity of the annular tire surface to achieve pulse compression, including: using a pair of chirped mirrors for dispersive compensation, and the single-chip chirp amount of the pair of chirped mirrors is designed to match according to the pre-compensation chirp amount of the annular cavity film layer and the pulse bandwidth after spectral broadening, where the total accumulated compensation dispersion amount cancels out the positive dispersion and transmission chirp introduced during the nonlinear spectral broadening process of the pulse; when the negative chirp provided by the annular cavity film layer has partially compensated the pulse chirp, the number of lenses of the pair of chirped mirrors is reduced, so that only 1 - 2 chirped mirrors are required to complete the total dispersion amount compensation in the dispersive compensation process, simplifying the structure of the dispersive compensation system.

[0100] According to the pre-compensation chirp amount of the annular cavity film layer (such as -1000 fs for a single pass 2 , and -8000 fs accumulated for 8 passes 2 ) and the pulse bandwidth after spectral broadening (Δλ = 35 nm), calculate the required out-of-cavity compensation amount: total compensation amount = −(nonlinear positive dispersion + transmission chirp) + film layer pre-compensation amount; for example, if the nonlinear process introduces +6000 fs 2 , the transmission chirp is +2000 fs 2 , and the film layer compensation is -8000 fs 2, the total compensation amount = 0, and only 1 chirped mirror is needed for fine tuning (±500 fs 2 ).

[0101] When the negative chirp of the film layer has compensated most of the dispersion (such as >70%), a pair of chirped mirrors consisting of 1 - 2 chirped mirrors is adopted (4 mirrors are required in the traditional scheme). Each mirror is designed with high reflectivity (>99.8%) and low high - order dispersion (third - order dispersion <10 4 fs 3 ). The remaining dispersion compensation is completed through single or double reflections, simplifying the number of optical path folds (from 4 folds to 1 fold). By combining pre - compensation in the cavity and fine - tuning outside the cavity, the total dispersion compensation accuracy is improved from ±1000 fs² in the traditional scheme to ±200 fs 2 , ensuring that the temporal side lobes of the compressed pulse are effectively suppressed (the main lobe energy accounts for >95%), and avoiding the side - effect of side - lobe energy on material processing (such as the expansion of the heat - affected zone). The reduction in the number of chirped mirrors and the decrease in the number of optical path folds reduce the volume of the entire compression module from 400×300×200 mm 3 of the traditional Herriott cavity scheme to 200×150×100 mm 3 , which is suitable for miniaturized devices (such as portable lidar, integrated processing heads). Reducing the number of chirped mirrors directly reduces the device cost (the cost of a single mirror is about 20,000 yuan, and saving 2 mirrors saves 40,000 yuan). At the same time, reducing the number of reflections reduces the optical loss (from 8% to less than 3%), and avoids the cumulative error introduced by multiple mirrors (such as uneven dispersion compensation caused by the deviation of the mirror installation angle).

[0102] In some embodiments, before compensating the dispersion of the pulse that has completed non - linear spectral broadening through the annular toroidal multi - pass cavity, it further includes: correcting the astigmatism during the beam transmission process using the toroid to improve the output beam quality; compensating the chirp during the pulse spectral broadening process through the low - chirp or negative - chirp dielectric film or metal film, reducing the number of chirped mirrors used outside the cavity.

[0103] Using aspheric design software (such as Code V) to optimize the toroid parameters, so that the curvature radii of the curved surface in the X / Y directions are R1 and R2 respectively (such as R1 = 100 mm, R2 = 200 mm), meeting the astigmatism correction condition: ΔastigmatismΔastigmatism = 1 / 2R1 - 1 / 2R2 = 0; processing the curved surface through diamond turning or magnetorheological polishing technology, with the surface accuracy reaching λ / 10 (λ = 632.8 nm), ensuring that the astigmatism difference of the beam is <λ / 4 after 8 reflections.

[0104] During the spectral broadening stage, the symmetry of the pulsed spectrum is monitored in real time by a spectrometer. If it is found that the low-frequency components are advanced (positive chirp characteristic), the chirp amount of the film layer is automatically calibrated (e.g., adjusted from -1000 fs² to -1200 fs²) to ensure that the spectral phase linearity after broadening is >98% (Fourier transform phase fluctuation < π / 8).

[0105] The astigmatism caused by the single cylindrical reflection in the traditional ring cavity deteriorates the spot ellipticity from 1.0 to 1.5. After the correction by the tire surface in this embodiment, the ellipticity is maintained below 1.1, and the focused spot diameter is reduced from 20 μm to 15 μm, improving the positioning accuracy of precision machining (such as micron-level drilling). The astigmatism correction avoids the local dispersion difference caused by beam distortion (the dispersion difference between the edge beam and the central beam in the traditional scheme can reach 2000 fs 2 ) so that the out-of-cavity chirped mirror only needs to compensate for the global dispersion without a complex local compensation design, and the algorithm complexity is reduced by more than 50%. The pre-chirp compensation and astigmatism correction form a "broadening-correction-compensation" closed-loop control. Compared with the open-loop debugging mode of the Herriott cavity, the robustness of the system to environmental disturbances (such as ±5°C temperature change, ±10 mrad vibration) is increased by 70%, and the fluctuation range of the pulse parameters during long-term operation (24 hours) is reduced from ±15% to ±3%.

[0106] In some embodiments, a Yb:YAG laser is used as the compressor input. The output parameters of the laser are: single-pulse energy 1 mJ, initial pulse width 700 fs, central wavelength 1030 nm, and repetition frequency 20 kHz. The beam quality (M 2 factor) of the laser output is optimized to <1.1 to ensure the light field uniformity of subsequent nonlinear compression. Two chirped mirrors are used for multi-pass (8-pass) dispersion compensation, and the chirp amount of a single piece is -1000 fs 2 @1030 nm, and the reflectivity >99.8%. The total accumulated dispersion compensation amount is -8000 fs². The output pulse spectrum is broadened to 1010–1045 nm. The corresponding spectral changes before and after compression are as Figure 8 shown. An autocorrelator is used to characterize the output pulse, and the characterization results of the compressed pulse are as Figure 9 shown.

[0107] Please refer to Figure 10 as shown Figure 10FIG. 0 is a schematic structural diagram of a non - linear pulse compression device 200 based on a multi - pass cavity with a toroidal tire surface provided by an embodiment of the present application. The non - linear pulse compression device 200 based on the multi - pass cavity with a toroidal tire surface is used to perform the steps of the non - linear pulse compression method based on the multi - pass cavity with a toroidal tire surface shown in the above embodiments. The non - linear pulse compression device 200 based on the multi - pass cavity with a toroidal tire surface can be a single server or a server cluster, or the non - linear pulse compression device 200 based on the multi - pass cavity with a toroidal tire surface can be a terminal, and the terminal can be a handheld terminal, a laptop computer, a wearable device, or a robot, etc.

[0108] As Figure 10 shown, the non - linear pulse compression device 200 based on the multi - pass cavity with a toroidal tire surface includes:

[0109] An astigmatism correction unit 201, which uses the multi - pass cavity with a toroidal tire surface as the core device for non - linear pulse compression. The multi - pass cavity with a toroidal tire surface adopts a closed - loop toroidal optical path, and the cavity surface of the toroidal cavity corresponding to the toroidal cavity is processed with a tire surface for astigmatism correction;

[0110] A cavity surface coating unit 202, which is used to coat a low - chirp or negative - chirp dielectric film or metal film on the cavity surface of the toroidal cavity to avoid introducing positive chirp or non - linear chirp during pulse reflection;

[0111] A dielectric insertion unit 203, which is used to insert a solid dielectric or inert gas into the toroidal cavity as a non - linear dielectric to regulate the non - linear effect in the multi - pass cavity;

[0112] A pulse incident unit 204, which is used to incident the pulse to be compressed into the multi - pass cavity with a toroidal tire surface, and change the number of reflections of the pulse to be compressed in the cavity by adjusting the incident angle, so as to adjust the optical path and intensity of the non - linear effect;

[0113] A compression realization unit 205, which is used to perform dispersion compensation on the pulse that has completed non - linear spectral broadening through the multi - pass cavity with a toroidal tire surface to realize pulse compression; wherein, the closed - loop toroidal optical path of the multi - pass cavity with a toroidal tire surface reduces the optical path detuning caused by vibration or temperature fluctuation, and the characteristic of the closed optical axis reduces the debugging complexity of optical path alignment. And under the same optical path, the length of the multi - pass cavity with a toroidal tire surface is less than that of the traditional Herriott cavity.

[0114] In some embodiments, depositing a low-chirp or negative-chirp dielectric film or metal film on the cavity surface of the ring cavity includes: designing the film layer structure of the dielectric film or metal film according to the central wavelength, spectral bandwidth, and target chirp compensation amount of the pulse to be compressed, so that the film layer provides low-chirp or negative-chirp reflection characteristics matching the chirp characteristics of the pulse within the spectral range of the pulse; wherein, the chirp amount of the negative-chirp film layer forms a complement with the positive chirp introduced by the nonlinear effect in the ring cavity, so as to synchronously compensate the transmission chirp during the pulse spectral broadening process and reduce the number of external-cavity dispersion compensation elements used.

[0115] In some embodiments, inserting a solid medium or inert gas into the ring cavity as a nonlinear medium to regulate the nonlinear effect in the multi-pass cavity includes: when the nonlinear medium is a solid medium, selecting a crystal or glass material with a matching nonlinear coefficient, the size of the solid medium being adapted to the optical path of the ring cavity, and regulating the nonlinear action intensity by adjusting the material refractive index or doping concentration of the solid medium; when the nonlinear medium is an inert gas, controlling the gas filling pressure of the ring cavity within the range of 10 kPa to 1 MPa, and adjusting the nonlinear coefficient by changing the gas type and filling pressure to match the nonlinear spectral broadening requirements of pulses to be compressed with different energies and pulse widths.

[0116] In some embodiments, injecting the pulse to be compressed into the ring tire surface multi-pass cavity includes: pre-optimizing the beam quality of the pulse to be compressed to ensure the light field uniformity of the incident beam; using the closed optical axis characteristic of the ring tire surface multi-pass cavity to achieve automatic optical path alignment through single-shot incidence calibration, without relying on a three-dimensional adjustment frame for precise angle adjustment, and reducing the debugging complexity at the incident end.

[0117] Exemplarily, adjusting the incident angle to change the number of reflections of the pulse to be compressed in the cavity to regulate the optical path and intensity of the nonlinear action includes: establishing a correspondence relationship model between the incident angle and the number of reflections, and by adjusting the incident angle, making the number of reflections of the pulse to be compressed in the ring tire surface multi-pass cavity dynamically change within a preset range; according to the pulse width after target pulse compression and the nonlinear spectral broadening requirements, calculating the required number of reflections through the correspondence relationship model and matching the corresponding incident angle to linearly tune the optical path and intensity of the nonlinear action and achieve flexible control of the pulse width.

[0118] In some embodiments, dispersive compensation is performed on the pulses that have completed nonlinear spectral broadening through the annular tire tread multi-pass cavity to achieve pulse compression, including: using a pair of chirped mirrors for dispersive compensation, and the chirp amount of a single chirped mirror in the pair of chirped mirrors is designed to match according to the pre-compensation chirp amount of the annular cavity film layer and the pulse bandwidth after spectral broadening. Among them, the total accumulated dispersive compensation amount cancels out the positive dispersion and transmission chirp introduced during the nonlinear spectral broadening process of the pulse; when the negative chirp provided by the annular cavity film layer has partially compensated the pulse chirp, the number of lenses in the pair of chirped mirrors is reduced, so that only 1-2 chirped mirrors are required to complete the total dispersive compensation amount in the dispersive compensation process, simplifying the structure of the dispersive compensation system.

[0119] In some embodiments, before performing dispersive compensation on the pulses that have completed nonlinear spectral broadening through the annular tire tread multi-pass cavity, it further includes: correcting the astigmatism during the beam transmission process using the tire tread to improve the output beam quality; compensating for chirp during the pulse spectral broadening process through the low-chirp or negative-chirp dielectric film or metal film, reducing the number of external-cavity chirped mirrors used.

[0120] It should be noted that those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described nonlinear pulse compression device based on the annular tire tread multi-pass cavity and each module can refer to the corresponding processes in the embodiments of the nonlinear pulse compression method based on the annular tire tread multi-pass cavity described above, and will not be elaborated here.

[0121] The above-described nonlinear pulse compression method based on the annular tire tread multi-pass cavity can be implemented in the form of a computer program, and this computer program can run on a device as shown in Figure 10 shown.

[0122] Please refer to Figure 11 , Figure 11 which is a schematic block diagram of the structure of the control module provided by an embodiment of the present application. The control module includes a processor, a memory, and a network interface connected through a device bus. Among them, the memory can include a storage medium and an internal memory.

[0123] The storage medium can store an operating device and a computer program. This computer program includes program instructions, and when the program instructions are executed, the processor can execute any nonlinear pulse compression method based on the annular tire tread multi-pass cavity.

[0124] The processor is used to provide computing and control capabilities to support the operation of the entire control module.

[0125] The internal memory provides an environment for the operation of a computer program in a non-volatile storage medium. When the computer program is executed by a processor, the processor can be caused to execute any non-linear pulse compression method based on a multi-pass cavity of a toroidal tire surface.

[0126] The network interface is used for network communication, such as sending assigned tasks, etc. Those skilled in the art can understand that Figure 11 the structure shown in [the figure] is only a block diagram of some structures related to the solution of the present application, and does not constitute a limitation on the terminal to which the solution of the present application is applied. The specific control module may include more or fewer components than those shown in the figure, or combine some components, or have a different component arrangement.

[0127] It should be understood that the processor may be a central processing unit (CPU), and the processor may also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. Among them, the general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0128] Among them, in one embodiment, the processor is used to run a computer program stored in the memory to implement the following steps:

[0129] Use a multi-pass cavity of a toroidal tire surface as the core device for non-linear pulse compression. The multi-pass cavity of the toroidal tire surface adopts a closed toroidal optical path, and the cavity surface of the toroidal cavity corresponding to the toroidal cavity is processed with a tire surface for astigmatism correction;

[0130] Deposit a low-chirp or negative-chirp dielectric film or metal film on the cavity surface of the toroidal cavity to avoid introducing positive chirp or non-linear chirp during pulse reflection;

[0131] Insert a solid medium or inert gas into the toroidal cavity as a non-linear medium to regulate the non-linear effect in the multi-pass cavity;

[0132] Incident the pulse to be compressed into the multi-pass cavity of the toroidal tire surface, and change the number of reflections of the pulse to be compressed in the cavity by adjusting the incident angle to adjust the optical path and the intensity of the non-linear effect of the non-linear action;

[0133] Disperse compensation is performed on the pulse that has completed nonlinear spectral broadening through the multi-pass cavity of the annular tire surface to achieve pulse compression; wherein, the closed annular optical path of the multi-pass cavity of the annular tire surface reduces the optical path detuning caused by vibration or temperature fluctuations, and the characteristic of the closed optical axis reduces the debugging complexity of optical path alignment. Moreover, at the same optical path, the length of the multi-pass cavity of the annular tire surface is less than that of the traditional Herriott cavity.

[0134] In some embodiments, coating a low-chirp or negative-chirp dielectric film or metal film on the cavity surface of the annular cavity includes: designing the film layer structure of the dielectric film or metal film according to the central wavelength, spectral bandwidth, and target chirp compensation amount of the pulse to be compressed, so that the film layer provides low-chirp or negative-chirp reflection characteristics that match the chirp characteristics of the pulse within the spectral range of the pulse; wherein, the chirp amount of the negative-chirp film layer forms a complement with the positive chirp introduced by the nonlinear effect in the annular cavity, so as to synchronously compensate the transmission chirp during the pulse spectral broadening process and reduce the number of off-cavity dispersion compensation elements used.

[0135] In some embodiments, inserting a solid medium or inert gas into the annular cavity as a nonlinear medium to regulate the nonlinear effect in the multi-pass cavity includes: when the nonlinear medium is a solid medium, selecting a crystal or glass material with a matched nonlinear coefficient, and the size of the solid medium is adapted to the optical path of the annular cavity, and regulating the nonlinear action intensity by adjusting the refractive index or doping concentration of the solid medium; when the nonlinear medium is an inert gas, controlling the gas filling pressure of the annular cavity within the range of 10 kPa to 1 MPa, and adjusting the nonlinear coefficient by changing the gas type and filling pressure to match the nonlinear spectral broadening requirements of pulses to be compressed with different energies and pulse widths.

[0136] In some embodiments, injecting the pulse to be compressed into the multi-pass cavity of the annular tire surface includes: pre-optimizing the beam quality of the pulse to be compressed to ensure the uniformity of the light field of the incident beam; using the characteristic of the closed optical axis of the multi-pass cavity of the annular tire surface to achieve automatic optical path alignment through single-incidence calibration, without relying on a three-dimensional adjustment frame for precise angle adjustment, and reducing the debugging complexity of the incident end.

[0137] Exemplarily, adjusting the incident angle to change the number of reflections of the pulse to be compressed in the cavity to regulate the optical path and intensity of the nonlinear action includes: establishing a correspondence relationship model between the incident angle and the number of reflections, and by adjusting the incident angle, making the number of reflections of the pulse to be compressed in the multi-pass cavity of the annular tire surface dynamically change within a preset range; according to the pulse width after target pulse compression and the nonlinear spectral broadening requirements, calculating the required number of reflections through the correspondence relationship model and matching the corresponding incident angle to linearly tune the optical path and intensity of the nonlinear action to achieve flexible control of the pulse width.

[0138] In some embodiments, dispersive compensation is performed on the pulse that has completed nonlinear spectral broadening through the annular tire surface multi-pass cavity to achieve pulse compression, including: using a pair of chirped mirrors for dispersive compensation. The chirp amount of a single piece of the pair of chirped mirrors is designed to match according to the pre-compensation chirp amount of the annular cavity film layer and the pulse bandwidth after spectral broadening. Among them, the total accumulated dispersive compensation amount cancels out the positive dispersion and transmission chirp introduced during the nonlinear spectral broadening process of the pulse; when the negative chirp provided by the annular cavity film layer has partially compensated the pulse chirp, the number of lenses of the pair of chirped mirrors is reduced, so that only 1-2 chirped mirrors are required to complete the total dispersive compensation amount in the dispersive compensation process, simplifying the structure of the dispersive compensation system.

[0139] In some embodiments, before performing dispersive compensation on the pulse that has completed nonlinear spectral broadening through the annular tire surface multi-pass cavity, it further includes: correcting the astigmatism during the beam transmission process by using the tire surface to improve the output beam quality; compensating for chirp during the pulse spectral broadening process through the low-chirp or negative-chirp dielectric film or metal film, reducing the number of external chirped mirrors used outside the cavity.

[0140] This application also provides a computer-readable storage medium storing a computer program, which when executed by a processor causes the processor to implement the steps of the nonlinear pulse compression method based on an annular tire surface multi-pass cavity provided in any embodiment of this application.

[0141] Among them, the computer-readable storage medium may be an internal storage unit of the control module described in the foregoing embodiments, such as the hard disk or memory of the control module. The computer-readable storage medium may also be an external storage device of the control module, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the control module.

[0142] As described above, the above are only specific embodiments of this application, but the protection scope of this application is not limited thereto. Any person skilled in the art can easily think of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

Claims

1. A non-linear pulse compression method based on a multi-pass cavity of a toroidal tire surface, characterized in that, Comprising: Using a toroidal tire - face multi - pass cell as the core device for non - linear pulse compression, the toroidal tire - face multi - pass cell adopts a closed - loop optical path, and the toroidal tire - face is machined on the cavity surface corresponding to the toroidal cavity for astigmatism correction; Coating a low - chirp or negative - chirp dielectric film or metal film on the cavity surface of the toroidal cavity to avoid introducing positive chirp or non - linear chirp during pulse reflection; Inserting a solid medium or inert gas into the toroidal cavity as the non - linear medium to regulate the non - linear effect in the multi - pass cell; Injecting the pulse to be compressed into the toroidal tire - face multi - pass cell, and changing the number of reflections of the pulse to be compressed in the cavity by adjusting the incident angle to adjust the optical path and intensity of the non - linear effect; Performing dispersion compensation on the pulse that has completed non - linear spectral broadening through the toroidal tire - face multi - pass cell to achieve pulse compression; wherein, the closed - loop optical path of the toroidal tire - face multi - pass cell reduces the optical path detuning caused by vibration or temperature fluctuations, the closed - optical - axis characteristic reduces the commissioning complexity of optical path alignment, and under the same optical path, the length of the toroidal tire - face multi - pass cell is less than that of the traditional Herriott cell.

2. The method according to claim 1, wherein The coating of the low - chirp or negative - chirp dielectric film or metal film on the cavity surface of the toroidal cavity includes: Designing the film - layer structure of the dielectric film or metal film according to the central wavelength, spectral bandwidth, and target chirp compensation amount of the pulse to be compressed, so that the film layer provides low - chirp or negative - chirp reflection characteristics matching the chirp characteristics of the pulse within the spectral range of the pulse; Among them, the chirp amount of the negative - chirp film layer forms a complement with the positive chirp introduced by the non - linear effect in the toroidal cavity to synchronously compensate for the transmission chirp during the pulse spectral broadening process and reduce the number of external - cavity dispersion compensation elements used.

3. The method according to claim 1, characterized in that The inserting of a solid medium or inert gas into the toroidal cavity as the non - linear medium to regulate the non - linear effect in the multi - pass cell includes: When the non - linear medium is a solid medium, selecting a crystal or glass material with a matched non - linear coefficient, the size of the solid medium is adapted to the optical path of the toroidal cavity, and the non - linear effect intensity is regulated by adjusting the refractive index or doping concentration of the solid medium; When the non - linear medium is an inert gas, controlling the gas filling pressure of the toroidal cavity within the range of 10 kPa to 1 MPa, and adjusting the non - linear coefficient by changing the gas type and filling pressure to match the non - linear spectral broadening requirements of pulses with different energies and pulse widths.

4. The method according to claim 1, characterized in that, The injecting of the pulse to be compressed into the toroidal tire - face multi - pass cell includes: Pre - optimizing the beam quality of the pulse to be compressed to ensure the uniformity of the optical field of the incident beam; Utilizing the closed - optical - axis characteristic of the toroidal tire - face multi - pass cell to achieve automatic optical path alignment through single - incidence calibration, without relying on a three - dimensional adjustment mount for precise angle adjustment, and reducing the commissioning complexity of the incident end.

5. The method according to claim 4, wherein The adjusting of the incident angle to change the number of reflections of the pulse to be compressed in the cavity to adjust the optical path and intensity of the non - linear effect includes: Establish a correspondence model between the incident angle and the number of reflections, and by adjusting the incident angle, make the number of reflections of the pulse to be compressed in the multi-pass cavity of the annular tire surface change dynamically within a preset range; According to the pulse width after the target pulse is compressed and the non-linear spectral broadening requirement, calculate the required number of reflections through the correspondence model, and match the corresponding incident angle to linearly tune the optical path and the intensity of the non-linear effect, so as to realize flexible control of the pulse width.

6. The method according to claim 1, wherein The dispersion compensation for the pulse that has completed non-linear spectral broadening through the multi-pass cavity of the annular tire surface to achieve pulse compression includes: Use a pair of chirped mirrors for dispersion compensation. The single-chip chirp amount of the pair of chirped mirrors is matched and designed according to the pre-compensation chirp amount of the annular cavity film layer and the pulse bandwidth after spectral broadening. Among them, the total accumulated dispersion compensation amount cancels out the positive dispersion and transmission chirp introduced during the non-linear spectral broadening process of the pulse; When the negative chirp provided by the annular cavity film layer has partially compensated the pulse chirp, reduce the number of lenses of the pair of chirped mirrors, so that the total dispersion compensation amount can be completed with only 1-2 chirped mirrors in the dispersion compensation process, simplifying the structure of the dispersion compensation system.

7. The method according to claim 1, wherein Before the dispersion compensation for the pulse that has completed non-linear spectral broadening through the multi-pass cavity of the annular tire surface, it also includes: Use the tire surface to correct the astigmatism during the beam transmission process to improve the output beam quality; Compensate chirp during the pulse spectral broadening process through the low-chirp or negative-chirp dielectric film or metal film to reduce the number of extracavity chirped mirrors used.

8. A non-linear pulse compression device based on a multi-pass cavity of a toroidal tire surface, characterized in that, It includes: An astigmatism correction unit, which uses a multi-pass cavity of an annular tire surface as the core device for non-linear pulse compression. The multi-pass cavity of the annular tire surface adopts a closed annular optical path, and the cavity surface of the annular cavity corresponding to the annular cavity is processed with a tire surface for astigmatism correction; A cavity surface coating unit, which is used to coat a low-chirp or negative-chirp dielectric film or metal film on the cavity surface of the annular cavity to avoid introducing positive chirp or non-linear chirp during pulse reflection; A medium insertion unit, which is used to insert a solid medium or an inert gas into the annular cavity as a non-linear medium to regulate the non-linear effect in the multi-pass cavity; A pulse incident unit, which is used to incident the pulse to be compressed into the multi-pass cavity of the annular tire surface, and change the number of reflections of the pulse to be compressed in the cavity by adjusting the incident angle, so as to adjust the optical path and the intensity of the non-linear effect; A compression realization unit, which is used to perform dispersion compensation on the pulse that has completed non-linear spectral broadening through the multi-pass cavity of the annular tire surface to achieve pulse compression; among them, the closed annular optical path of the multi-pass cavity of the annular tire surface reduces the optical path detuning caused by vibration or temperature fluctuation, and the closed optical axis characteristic reduces the debugging complexity of the optical path alignment. And under the same optical path, the length of the multi-pass cavity of the annular tire surface is less than that of the traditional Herriott cavity.

9. A control module, characterized in that, The control module includes a memory and a processor; The memory is used to store computer programs; The processor is used to execute the computer program and implement the method according to any one of claims 1 to 7 when executing the computer program.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the processor is caused to implement the method according to any one of claims 1 to 7.

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