System and method for adjusting and compensating high-order dispersion through broadening-compression coordination

Abstract

The invention belongs to the field of laser emission devices, and provides a system and a method for adjusting and compensating high-order dispersion through broadening-compression coordination, and the method comprises the steps: calculating second-order dispersion and third-order dispersion introduced by a pulse amplifier; the introduced third-order dispersion is adjusted by changing the grating incidence angle in the pulse stretcher, so that the introduced third-order dispersion is counteracted with the total third-order dispersion of the system; according to the second-order dispersion change generated after the angle of the pulse stretcher is adjusted, a second-order dispersion value required to be provided by the pulse compressor is calculated, and the effective distance of the grating pair is adjusted for accurate compensation; and the angle of the pulse stretcher is corrected again according to the third-order dispersion feedback adjusted by the pulse compressor, and the steps are repeated until the total second-order dispersion and the third-order dispersion of the system approach to zero, so that near-transformation limit compression is realized. By adjusting the grating incident angle of the stretcher and the grating effective distance of the compressor, synchronous compensation of second-order and third-order dispersion in the ultrafast laser system is realized, and pulse output close to the transformation limit is obtained.

Description

Technical Field

[0001] The present invention belongs to the field of laser emitting devices, and in particular relates to a system and method for compensating for high-order dispersion by coordinated adjustment of stretching and compression. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Femtosecond lasers have been widely used in precision machining, bioimaging, spectral analysis and other fields. One of the core indicators for measuring the performance of a laser system is the energy and pulse width of the laser pulse. Typically, the average power output by a femtosecond laser oscillator is only in the milliwatt range, the energy of a single pulse is low, and the peak power is limited, making it difficult to meet the needs of high-energy applications. To this end, the femtosecond pulses need to be regenerated and amplified. However, due to the extremely short time width of femtosecond pulses, if they are directly amplified, their high peak power can easily exceed the damage threshold of the gain medium and other optical components in the system, leading to nonlinear effects and even device damage.

[0004] To address these issues, chirped pulse amplification (CPA) technology is often used. This technique uses a pulse stretcher to stretch femtosecond pulses to picoseconds or longer, thereby reducing peak power. This pulse is then boosted by an amplifier, and finally restored to a shorter pulse output by a compressor. While this method effectively avoids nonlinear damage, it inevitably introduces second-order chromatic dispersion (GDD) and third-order chromatic dispersion (TOD) into the system.

[0005] Dispersion introduced into the system primarily stems from two sources: first, the material dispersion of the gain medium, which propagates light of different wavelengths at different speeds, resulting in propagation delays between frequency components; and second, the inherent dispersion characteristics of various optical components in the system (such as lenses and mirrors). Second-order dispersion (GDD) is tunable and controllable to a certain extent and is often compensated for by adjusting the grating spacing in the compressor. However, third-order dispersion (TOD), a higher-order term in the rate of dispersion change, induces pulse distortions such as tailing, ringing, and sub-pulses, which severely impact pulse quality and temporal resolution. Currently, there is a lack of an effective and simple compensation method. Summary of the Invention

[0006] To address the above-mentioned issues, the present invention proposes a system and method for coordinated stretching and compression to compensate for high-order dispersion. By adjusting the grating incident angle of the stretcher and the effective grating distance of the compressor, the present invention achieves synchronous compensation of second-order and third-order dispersion in the ultrafast laser system, thereby obtaining a pulse output close to the conversion limit.

[0007] According to some embodiments, the present invention adopts the following technical solutions: A system for compensating for high-order dispersion by coordinated stretching and compression, comprising: Pulse oscillator, used to generate seed pulses of femtosecond and picosecond pulse levels; The pulse stretcher has a grating structure, which changes the dispersion by adjusting the grating incident angle and the grating effective distance, provides positive second-order dispersion, and realizes the stretching of the seed pulse generated by the pulse oscillator; The pulse amplifier is used to amplify the stretched seed pulse. During the amplification process, some unnecessary second-order dispersion and third-order dispersion will be introduced. A pulse compressor having a grating structure, which changes the dispersion by adjusting the grating incident angle and the grating effective distance, providing negative second-order dispersion to compress the amplified seed pulse; A collaborative adjustment and compensation module is used to calculate the second-order dispersion and third-order dispersion introduced by the pulse amplifier; by changing the grating incident angle in the pulse stretcher, the introduced third-order dispersion is adjusted to offset the total third-order dispersion of the system; based on the change in second-order dispersion caused by the pulse stretcher angle adjustment, the second-order dispersion value required by the pulse compressor is calculated, and accurately compensated by adjusting the effective distance of its grating pair; the pulse stretcher angle is corrected again based on the third-order dispersion feedback after the pulse compressor adjustment, and the above steps are repeated until the total second-order dispersion and third-order dispersion of the system approach zero, achieving near-transformation limit compression.

[0008] As an optional embodiment, the grating in the grating structure is a transmissive or reflective grating, and its line density range is [600 lines / mm, 1800 lines / mm], that is, [600 line pairs / mm, 1800 line pairs / mm].

[0009] As a further embodiment, the grating incident light and the diffracted light of the grating satisfy the grating equation; When the incident angle is equal to the diffraction angle and satisfies the Littrow angle condition, the diffraction efficiency is maximum.

[0010] As a further embodiment, the range of the incident light on the grating is [36°, 70°].

[0011] As an optional implementation, the effective distance of the grating pair can be adjusted in the range of [0.3 m, 1.0 m].

[0012] As an optional embodiment, the pulse stretcher is a double grating structure, including a first diffraction grating, a 4f system, a second diffraction grating and a reflector placed in the order of the optical path, wherein the first diffraction grating is used to spatially expand the incident light and control the dispersion by adjusting its incident angle; The 4f system consists of two lenses with equal focal lengths, forming a 1:1 imaging structure; The second diffraction grating is used to collimate the light path back; The reflecting mirror is used to return the light path.

[0013] As an optional embodiment, the pulse stretcher is a single grating structure, and its optical path includes a first diffraction grating, a concave reflector, a convex reflector and a roof reflector in sequence; The concave reflector focuses the diffracted light onto the convex mirror; The convex reflector and the concave mirror are placed concentrically to form a telescopic system to reflect the light again; The roof reflector is used to fold back the light path so that the light can follow a predetermined path to achieve a four-way or eight-way folded light path.

[0014] As an optional embodiment, the pulse compressor is a double grating structure, including a first diffraction grating, a second diffraction grating and a reflector placed in the order of the optical path, the two diffraction gratings are arranged in parallel, and the system dispersion is adjusted by changing the distance between the grating pairs; Reflectors are used to fold back the light path.

[0015] As an optional embodiment, the pulse compressor is a single grating structure, including a first diffraction grating, a reflector and a roof reflector; The reflector returns the light beam to the effective area of ​​the first diffraction grating; The roof reflector is used to adjust the light path and can bend the light beam multiple times.

[0016] As an optional embodiment, when the pulse compressor has a single grating structure, the process of adjusting the effective distance of its grating pair for precise compensation is replaced by adjusting the effective distance between the grating and the reflector for precise compensation.

[0017] The working method of the system based on the above-mentioned stretching-compression coordinated adjustment and compensation of high-order dispersion includes the following steps: The pulse oscillator generates seed pulses of femtosecond and picosecond pulse levels; The pulse stretcher changes the dispersion by adjusting the grating incident angle and the grating effective distance, providing positive second-order dispersion to achieve the stretching of the seed pulse generated by the pulse oscillator; The pulse amplifier amplifies the stretched seed pulse, and in the process of amplification, some unwanted second-order dispersion and third-order dispersion are introduced; The pulse compressor changes the dispersion by adjusting the grating incident angle and the grating effective distance, providing negative second-order dispersion to compress the amplified seed pulse; The collaborative adjustment and compensation module calculates the second-order and third-order dispersions introduced by the pulse amplifier. By changing the incident angle of the grating in the pulse stretcher, the introduced third-order dispersion is adjusted to offset the total third-order dispersion of the system. Based on the change in second-order dispersion caused by the pulse stretcher angle adjustment, the second-order dispersion value required by the pulse compressor is calculated, and the effective distance of its grating pair is adjusted to accurately compensate for it. The pulse stretcher angle is corrected again based on the feedback of the adjusted third-order dispersion of the pulse compressor. The above steps are repeated until the total second-order and third-order dispersions of the system approach zero, achieving near-transformation limit compression.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The present invention does not require additional optical elements, has a simple structure, and has a high degree of adjustment freedom. By adjusting the grating incident angle of the stretcher and the effective grating distance of the compressor, the second-order and third-order dispersion in the ultrafast laser system can be synchronously compensated, thereby obtaining a pulse output close to the conversion limit. The present invention can effectively compensate for or minimize the influence of third-order dispersion in the amplification system, which is conducive to further improving the quality and stability of the output pulses of the ultrafast laser system.

[0019] The present invention has a wide range of applications and is suitable for ultrafast laser systems with limited space or extremely high requirements for output pulse quality, and can achieve comprehensive compensation for non-ideal dispersion of the system.

[0020] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0022] Figure 1 Schematic diagram of the structure of a transmissive double-grating pulse stretcher according to an embodiment; Figure 2 Schematic diagram of the structure of a reflective double-grating pulse stretcher according to an embodiment; Figure 3 Schematic diagram of the structure of a transmissive single-grating pulse stretcher according to an embodiment; Figure 4 Schematic diagram of the structure of a reflective single-grating pulse stretcher according to an embodiment; Figure 5 Schematic diagram of the structure of a transmissive double-grating pulse compressor according to an embodiment; Figure 6 Schematic diagram of the structure of a reflective dual-grating pulse compressor according to an embodiment; Figure 7Schematic diagram of the structure of a transmission-type single-grating pulse compressor according to an embodiment; Figure 8 Schematic diagram of the structure of a reflective single-grating pulse compressor according to an embodiment; Figure 9 FIG4 is a flowchart of a dispersion compensation iteration according to an embodiment.

[0023] Among them, 101 is a transmission grating, 102 is a reflection grating, 2 is a lens with a certain focal length, and two lenses can form a 4f system; 3 is a reflector; 4 is a convex reflector; 5 is a concave reflector; 6 is a plane reflector; and 7 is a roof reflector. DETAILED DESCRIPTION

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0026] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0027] In the absence of conflict, the embodiments and features in the embodiments of this application can be combined with each other.

[0028] Example 1 A system for compensating for high-order dispersion by coordinated stretching and compression, comprising: A pulse oscillator (hereinafter referred to as the oscillator) is used to generate seed pulses of the femtosecond and picosecond pulse order; The pulse stretcher (hereinafter referred to as the stretcher) has a grating structure. By adjusting the grating incident angle and the grating effective distance, the dispersion is changed to provide positive second-order dispersion, thereby achieving the stretching of the seed pulse generated by the pulse oscillator. The pulse amplifier (hereinafter referred to as the amplifier) ​​is used to amplify the stretched seed pulse. During the amplification process, some unwanted second-order and third-order dispersion will be introduced. The pulse compressor (hereinafter referred to as the compressor) has a grating structure, which changes the dispersion by adjusting the grating incident angle and the grating effective distance, providing negative second-order dispersion to compress the amplified seed pulse; Coordinated adjustment compensation modules, such as Figure 9 As shown, it is used to calculate the second-order dispersion and third-order dispersion introduced by the pulse amplifier; by changing the grating incident angle in the pulse stretcher, the introduced third-order dispersion is adjusted to offset the total third-order dispersion of the system; according to the change in the second-order dispersion caused by the pulse stretcher angle adjustment, the second-order dispersion value required by the pulse compressor is calculated, and the effective distance of its grating pair is adjusted to accurately compensate for it; according to the feedback of the third-order dispersion adjusted by the pulse compressor, the pulse stretcher angle is corrected again, and the above steps are repeated until the total second-order dispersion and third-order dispersion of the system approach zero, achieving near-transformation limit compression.

[0029] The grating parameter design described in this invention is suitable for the near-infrared band (such as the central wavelength of Yb lasers, 1020-1080nm), but those skilled in the art will understand that the method is also applicable to other operating bands (such as 800nm, 1550nm, etc.) and similar dispersion adjustment can be achieved by adjusting the grating line density and incident angle. The grating used in the present invention can be a transmission type or a reflection type grating, and its line density range is 600-1800 lines / mm. The specific selection depends on the required dispersion value, incident angle matching and laser operating wavelength.

[0030] If it is a reflective grating, it works near the Littrow angle; when the incident angle deviates too much from the Littrow angle, the diffraction efficiency decreases.

[0031] The incident light and diffracted light of different types of gratings satisfy the grating equation: (1) Where m is the diffraction order of the grating, is the wavelength, Λ is the grating period, is the incident angle of the light beam, is the diffraction angle of the light beam.

[0032] When the incident angle is equal to the diffraction angle and satisfies the Littrow angle condition, the diffraction efficiency is maximum, that is, The best angle of incidence at this time : (2) By properly configuring the grating parameters, the required GDD and TOD can be obtained. The phase delay of the system can be expressed by Taylor expansion: (3) The above formula, represent right At angular frequency The nth derivative at . is the center frequency, is the group delay, which represents the time it takes for light of this frequency to pass through the system; Second-order dispersion will broaden the pulse. and It is third-order dispersion and fourth-order dispersion, which will cause the pulse to be distorted.

[0033] The second-order dispersion GDD and third-order dispersion TOD can be expressed as: (4) (5) Where c is the speed of light in a vacuum and Lg is the vertical distance between the grating pairs.

[0034] The reflectors 3, lenses, and other optical components used in this invention should be coated with high-reflection or high-transmittance coatings that match the laser wavelength used, such as HR@1020-1080nm or broadband anti-reflection coatings. These coating types are not limited; the appropriate coating solution can be selected based on the laser's central wavelength.

[0035] The incident angle of the grating in the stretcher or compressor of the present invention should be calculated according to the grating equation and set in conjunction with the dispersion control requirements. Preferably, the incident angle is 38.9°, which satisfies the Littrow condition, or an angle close to it (e.g., 36°–40°) to achieve high diffraction efficiency and dispersion control capabilities. The incident angle can be adjusted by those skilled in the art for different wavelengths and groove densities as needed.

[0036] The reflector used to fold back the light path in the present invention may be a roof reflector 7 or a common plane reflector 6 , and the selection is made according to specific application requirements.

[0037] The effective distance between the grating pairs in the stretcher and compressor of the present invention is adjustable from 0.3 m to 1.0 m. This parameter directly determines the amount of dispersion, and adjusting its length can effectively compensate for the GDD introduced into the amplifier.

[0038] The stretcher and compressor structures of the present invention are not limited and can be a dual-grating + 4f system structure, a single grating + reflector structure, etc. These structures can be flexibly selected based on spatial layout, dispersion requirements, and integration, and can all achieve high-order dispersion compensation using the adjustment method described in the present invention.

[0039] like Figure 1 and Figure 2 As shown, in some embodiments, the stretcher is a double grating structure, including a first diffraction grating, a 4f system, a second diffraction grating and a reflector placed in the order of the optical path.

[0040] The first diffraction grating is used to spatially expand the incident light and control the dispersion by adjusting its incident angle; The 4f system consists of two lenses with equal focal lengths, forming a 1:1 imaging structure; The second diffraction grating is used to collimate the light path back; The reflecting mirror is used to return the light path.

[0041] Of course, depending on the type of grating, whether it is a transmissive grating 101 or a reflective grating 102 , the position of the reflector 3 can be adaptively adjusted.

[0042] like Figure 3 and Figure 4 As shown, in some embodiments, the stretcher may also be a single grating structure, and its optical path includes the first diffraction grating, the concave reflector 5, the convex reflector 4 and the roof reflector 7 in sequence.

[0043] The concave reflector 5 focuses the diffracted light onto the convex reflector; the convex reflector 4 is placed concentrically with the concave reflector to form a telescope system, reflecting the light again. The roof reflector 7 is used to fold the light path, allowing the light to follow the predetermined path, achieving a four-way or eight-way folded optical path.

[0044] like Figure 5 and Figure 6 As shown, in some embodiments, the compressor is a dual-grating structure, including a first diffraction grating, a second diffraction grating, and a reflector, arranged in the order of the optical path. The two gratings are arranged in parallel, and the system dispersion is adjusted by changing the distance between the grating pairs; the reflection is used to return the optical path.

[0045] like Figure 7 and Figure 8 As shown, in some embodiments, the compressor may also be a single grating structure, including a first diffraction grating, a reflector and a roof reflector 7; The reflector returns the light beam to the effective area of ​​the grating; The roof reflector 7 is used to adjust the light path and can bend the light beam multiple times.

[0046] Likewise, depending on the type of grating, whether it is a transmissive grating 101 or a reflective grating 102 , the positions of the reflector 3 and the roof reflector 7 are adaptively adjusted.

[0047] This method is applicable to various ultrafast laser systems with CPA architectures, including but not limited to femtosecond oscillators, stretchers, regenerative amplifiers, and compressors. It can also be expanded to include OPCPAs, picosecond systems, and nonlinear amplification systems.

[0048] The invention is applicable to ultrashort laser pulse systems with pulse widths between 30 fs and 1000 fs. After compression, pulses approaching the conversion limit can be obtained. The average power of the system's output pulses can range from milliwatts to hundreds of watts, with peak powers reaching terawatts.

[0049] In this embodiment, the grating parameters are as follows: the grating line period is 833 nm, corresponding to a line count of 1200 lines / mm. The central wavelength of the incident pulse is 1048 nm. According to the grating equation, the grating has the highest diffraction efficiency when the incident angle is 38.96°. The effective propagation distance of the grating in the stretcher is set to 0.4 m.

[0050] Ideally, if the amplifier introduces no additional dispersion (GDD = 0, TOD = 0), the compressor structure can be set to be completely symmetrical with the stretcher, meaning the effective distance between the compressor gratings is also 0.4 m. In this configuration, the dispersion provided by the compressor is exactly equal to the dispersion of the stretcher, with opposite sign, thus perfectly compensating for the dispersion introduced by the stretcher and compressing the pulse to the transform limit. At this point, the dispersion parameters provided by the stretcher and compressor are each |GDD| = 49.88 × 10 5 fs 2 ,|TOD|=96×10 5 fs 3 .

[0051] However, in practical systems, the amplifier part inevitably introduces a certain amount of high-order dispersion. In this embodiment, the dispersion parameter of the amplifier is GDD = 2.3×10 5 fs 2 , TOD = 7 × 10 5 fs 3 If the high-order dispersion in the system cannot be completely eliminated, it will cause severe distortion of the pulse's temporal shape. This will generate low-intensity pedestals on both sides of the pulse, reducing the peak power of the pulse and affecting the efficiency of other subsequent nonlinear optical processes.

[0052] In order to achieve pulse recompression, it is necessary to coordinately adjust the incident angle of the pulse stretcher and the effective grating distance of the compressor, so that the system dispersion is finally fully compensated.

[0053] Specifically, in this embodiment, the grating incident angle of the stretcher is first adjusted to 38°, sacrificing a portion of the diffraction efficiency within an acceptable range to make the third-order dispersion (TOD ≈ -103×10 5 fs 3 ) and the TOD introduced by other optical units in the system, thus achieving preliminary compensation for the third-order dispersion. Since the change of the incident angle will also affect the GDD provided by the stretcher (here is 52.017×10 5 fs 2 ), so the effective propagation distance between the compressor grating pairs needs to be adjusted synchronously so that the GDD provided by the compressor (here is -54.317×10 5 fs2 ) cancels out the sum of the GDD of the stretcher and amplifier.

[0054] However, the change of the effective distance of the compressor will affect the TOD value of its output (for example, after adjustment, it is +105 × 10 5 fs 3 ), at which point the stretcher incident angle needs to be fine-tuned again to maintain the balance of the system's overall TOD compensation. This iterative adjustment of the stretcher incident angle and compressor grating distance ultimately achieves full compensation of the system's GDD and TOD, compressing the pulse to a width close to the conversion limit.

[0055] The following calculation results are a specific adjustment example of an optimized configuration (as shown in Table 1, where GDD units are ×10 5 fs 2 , TOD units × 10 5 fs 3 ): When the incident angle of the stretcher grating is 35.9° and the effective propagation distance of the compressor grating is 480.15 mm, the total GDD and TOD of the system are fully compensated, and the output pulse can be compressed to the shortest.

[0056] Table 1 System configuration parameters

[0057] Example 2 The working method of the system for stretching-compression coordinated adjustment and compensation of high-order dispersion provided in the first embodiment includes the following steps: The pulse oscillator generates seed pulses of femtosecond and picosecond pulse levels; The pulse stretcher changes the dispersion by adjusting the grating incident angle and the grating effective distance, providing positive second-order dispersion to achieve the stretching of the seed pulse generated by the pulse oscillator; The pulse amplifier amplifies the stretched seed pulse, and in the process of amplification, some unwanted second-order dispersion and third-order dispersion are introduced; The pulse compressor changes the dispersion by adjusting the grating incident angle and the grating effective distance, providing negative second-order dispersion to compress the amplified seed pulse; The collaborative adjustment and compensation module calculates the second-order and third-order dispersions introduced by the pulse amplifier. By changing the incident angle of the grating in the pulse stretcher, the introduced third-order dispersion is adjusted to offset the total third-order dispersion of the system. Based on the change in second-order dispersion caused by the pulse stretcher angle adjustment, the second-order dispersion value required by the pulse compressor is calculated, and the effective distance of its grating pair is adjusted to accurately compensate for it. The pulse stretcher angle is corrected again based on the feedback of the adjusted third-order dispersion of the pulse compressor. The above steps are repeated until the total second-order and third-order dispersions of the system approach zero, achieving near-transformation limit compression.

[0058] In this embodiment, a stretcher adjustment mechanism is proposed: by changing the grating incident angle, the third-order dispersion TOD introduced by the stretcher is adjusted to offset the total TOD of the system; Compressor compensation mechanism: Based on the GDD change caused by the stretcher angle adjustment, the GDD value required by the compressor is calculated and accurately compensated by adjusting the effective distance of its grating pair; Closed-loop compensation iterative method: Since TOD and GDD are coupled to each other, the total dispersion of the system is recalculated after each adjustment. Through multiple rounds of iterative calculations, the total GDD and TOD of the system are eventually brought close to zero, achieving near-transformation limit compression.

[0059] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made by those skilled in the art that fall within the spirit and principles of the present invention and do not require creative effort are intended to be within the scope of protection of the present invention.

Claims

1. A system for coordinated stretching and compression to compensate for high-order dispersion, characterized in that: include: Pulse oscillator, used to generate seed pulses of femtosecond and picosecond pulse levels; A pulse stretcher has a grating structure, which changes the dispersion by adjusting the grating incident angle and the grating effective distance, providing positive second-order dispersion to achieve the stretching of the seed pulse generated by the pulse oscillator; The pulse amplifier is used to amplify the stretched seed pulse. During the amplification process, some unnecessary second-order dispersion and third-order dispersion will be introduced. A pulse compressor having a grating structure, which changes the dispersion by adjusting the grating incident angle and the grating effective distance, providing negative second-order dispersion to compress the amplified seed pulse; A collaborative adjustment and compensation module is used to calculate the second-order dispersion and third-order dispersion introduced by the pulse amplifier; by changing the grating incident angle in the pulse stretcher, the introduced third-order dispersion is adjusted to offset the total third-order dispersion of the system; based on the change in second-order dispersion caused by the pulse stretcher angle adjustment, the second-order dispersion value required by the pulse compressor is calculated, and accurately compensated by adjusting the effective distance of its grating pair; the pulse stretcher angle is corrected again based on the third-order dispersion feedback after the pulse compressor adjustment, and the above steps are repeated until the total second-order dispersion and third-order dispersion of the system approach zero, achieving near-transformation limit compression.

2. The system for compensating for high-order dispersion by coordinated stretching and compression according to claim 1, wherein: The grating in the grating structure is a transmissive or reflective grating, and the grating incident light and the diffracted light of the grating satisfy the grating equation; When the incident angle is equal to the diffraction angle and satisfies the Littrow angle condition, the diffraction efficiency is maximum.

3. The system for compensating for high-order dispersion by coordinated stretching and compression according to claim 2, wherein: The line density range of the grating is [600 line pairs / mm, 1800 line pairs / mm]; The range of the incident light on the grating is [36°, 70°].

4. The system for compensating for high-order dispersion by coordinated stretching and compression according to claim 1, wherein: The effective distance of the grating pair can be adjusted in the range of [0.3 m, 1.0 m].

5. The system for compensating for high-order dispersion by coordinated stretching and compression according to claim 1, wherein: The pulse stretcher is a double-grating structure, comprising a first diffraction grating, a 4f system, a second diffraction grating and a reflector placed in the order of the optical path, wherein the first diffraction grating is used to spatially expand the incident light and control the dispersion by adjusting its incident angle; The 4f system consists of two lenses with equal focal lengths, forming a 1:1 imaging structure; The second diffraction grating is used to collimate the light path back; The reflecting mirror is used to return the light path.

6. The system for compensating for high-order dispersion by coordinated stretching and compression according to claim 1, wherein: The pulse stretcher is a single grating structure, and its optical path includes a first diffraction grating, a concave reflector, a convex reflector and a roof reflector in sequence; The concave reflector focuses the diffracted light onto the convex mirror; The convex reflector and the concave mirror are placed concentrically to form a telescopic system to reflect the light again; The roof reflector is used to fold back the light path so that the light can follow a predetermined path to achieve a four-way or eight-way folded light path.

7. The system for compensating high-order dispersion by coordinated stretching and compression according to claim 1, wherein: The pulse compressor has a double grating structure, including a first diffraction grating, a second diffraction grating and a reflector placed in the order of the optical path. The two diffraction gratings are arranged in parallel, and the system dispersion is adjusted by changing the distance between the grating pairs. Reflectors are used to fold back the light path.

8. The system for compensating high-order dispersion by coordinated stretching and compression according to claim 1, wherein: The pulse compressor is a single grating structure, comprising a first diffraction grating, a reflector and a roof reflector; The reflector returns the light beam to the effective area of ​​the first diffraction grating; The roof reflector is used to adjust the light path and can bend the light beam multiple times.

9. The system for compensating for high-order dispersion by coordinated stretching and compression according to claim 8, wherein: When the pulse compressor is a single grating structure, the process of adjusting the effective distance of its grating pair for precise compensation is replaced by adjusting the effective distance between the grating and the reflector for precise compensation.

10. A method for operating a system for compensating for high-order dispersion by cooperative stretching and compression adjustment based on any one of claims 1 to 9, characterized in that: The following steps are involved: The pulse oscillator generates seed pulses of femtosecond and picosecond pulse levels; The pulse stretcher changes the dispersion by adjusting the grating incident angle and the grating effective distance, providing positive second-order dispersion to achieve the stretching of the seed pulse generated by the pulse oscillator; The pulse amplifier amplifies the stretched seed pulse, and in the process of amplification, some unwanted second-order dispersion and third-order dispersion are introduced; The pulse compressor changes the dispersion by adjusting the grating incident angle and the grating effective distance, providing negative second-order dispersion to compress the amplified seed pulse; The collaborative adjustment and compensation module calculates the second-order and third-order dispersions introduced by the pulse amplifier. By changing the incident angle of the grating in the pulse stretcher, the introduced third-order dispersion is adjusted to offset the total third-order dispersion of the system. Based on the change in second-order dispersion caused by the pulse stretcher angle adjustment, the second-order dispersion value required by the pulse compressor is calculated, and the effective distance of its grating pair is adjusted to accurately compensate for it. The pulse stretcher angle is corrected again based on the feedback of the adjusted third-order dispersion of the pulse compressor. The above steps are repeated until the total second-order and third-order dispersions of the system approach zero, achieving near-transformation limit compression.

Images