Short pulse regenerative amplifier based on spectrum shaping

Abstract

The invention discloses a short pulse regenerative amplifier based on spectrum shaping, and belongs to the technical field of femtosecond laser. Comprising a seed light source, a spectrum shaping system, a broadening module, an amplification module and a pulse compression module which are sequentially arranged along a light path, and an initial pulse light beam is output through the seed light source; carrying out nonlinear effect spectrum broadening and collimation shaping on the initial pulse light beam through a spectrum shaping system; a pulse light beam is sequentially adjusted into vertical polarized light and horizontal polarized light through a broadening module, and the pulse time domain width of the pulse light beam is broadened to hundred ps magnitude when the pulse light beam is in the vertical polarized light; gains of incident horizontal polarized light are extracted back and forth for multiple times through an amplification module, and amplified pulse light signals are output; the laser gain energy in the amplification module is controlled by the gain energy adjusting module; and the amplified pulse optical signal is compressed and exported through the pulse compression module. According to the invention, the influence of gain narrowing in the amplification process is eliminated, the amplified pulse with a wider spectrum is obtained, and the width of the compressed pulse is less than 100fs.

Description

Technical Field

[0001] The invention belongs to the technical field of femtosecond lasers, and in particular relates to a short pulse regenerative amplifier based on spectrum shaping. Background Art

[0002] The chirped pulse amplification (CPA) technology invented by Gerard Mourou and Donna Strickland in 1985 provided a reliable idea for improving the energy of femtosecond lasers, and they were awarded the 2018 Nobel Prize in Physics. Combined with CPA technology, all-solid-state ytterbium-doped femtosecond laser amplifiers play an important role in industrial ultrafast non-thermal micromachining, extreme ultraviolet optical frequency combs, high-throughput high-order harmonic generation, and angle-resolved electron momentum spectroscopy.

[0003] The emergence of regenerative amplifiers has further improved the energy of ultrashort pulse lasers, and even very low incident laser energy can achieve sufficiently large gains in multiple round-trip amplifications. At present, the disclosed technologies include regenerative cavities based on dual Yb:KGW crystals. Each crystal is pumped by two LDs with an average power of 50W, and an average power of 30W laser amplification output is obtained at a repetition frequency of 100kHz. At the same time, the spectrum width is 5.4nm, corresponding to a pulse width of less than 300fs. In the disclosed technology, the single pulse energy output by the oscillator is 10nJ, and the seed pulse with a pulse width of 92fs is widened and injected into the regenerative amplifier based on the Yb:CGA crystal, and an average power of 36W laser amplification is obtained. Finally, after transmission grating compression, an average power of 28W, a repetition frequency of 500kHz, a single pulse energy of 56μJ, a pulse width of 217fs, and a peak power of 258MW of high repetition rate ultrashort pulse laser output is achieved. Among the disclosed technologies, a regenerative cavity based on two Yb:KGW crystals placed orthogonally in a tangential direction is used to obtain a repetition frequency of 1kHz and a single pulse energy of 1.2mJ, which shortens the pulse width to 227fs while obtaining mJ energy. However, due to the different gains of different spectral components of the input pulse within the gain bandwidth, the input pulse spectrum will be lost after multiple gains, that is, the gain narrowing phenomenon, making it difficult to obtain an amplified pulse with a pulse width less than 100fs, limiting the application of lasers in some fields. Therefore, in order to ensure that the final amplified pulse can maintain the same time quality characteristics as the seed pulse, it is necessary to accurately control the seed spectrum phase and each order of chirp during the amplification process. Summary of the invention

[0004] Technical issues to be solved:

[0005] In order to avoid the shortcomings of the prior art, the present invention provides a short pulse regenerative amplifier based on spectrum shaping, which adopts a spectrum shaping system based on the second-order nonlinear effect to broaden the incident laser pulse and form a saddle-shaped spectrum at the same time, and determines the wavelength depression position based on the central wavelength of the light source, and the depression position coincides with the gain peak, thereby alleviating the gain narrowing; at the same time, by limiting the optical axis direction of the laser gain crystal and combining different axial gain spectra, the bandwidth is greatly increased, which is beneficial to offset the influence of gain narrowing during the amplification process, and finally obtains a wide-spectrum amplified pulse, and the pulse width after compression is less than 100fs.

[0006] The technical solution of the present invention is: a short pulse regenerative amplifier based on spectrum shaping, comprising a seed light source, a spectrum shaping system, a stretching module, an amplification module, and a pulse compression module arranged in sequence along an optical path.

[0007] Outputting an initial pulse light beam through the seed light source;

[0008] The spectrum shaping system is used to perform nonlinear effect spectrum broadening and collimation shaping on the initial pulse beam;

[0009] The collimated and shaped pulse beam is adjusted into vertical polarized light and horizontal polarized light in sequence by the stretching module, and the pulse time domain of the vertical polarized light is stretched to the order of hundreds of ps;

[0010] The amplification module extracts the gain of the incident horizontally polarized light by making multiple round trips in the regeneration cavity, and outputs an amplified pulse light signal; the laser gain energy in the amplification module is controlled by the gain energy adjustment module;

[0011] The amplified pulse light signal is compressed and exported through the pulse compression module.

[0012] A further technical solution of the present invention is: the seed light source is a light source based on ytterbium-doped medium, with a maximum output power of 7W, a pulse width of 122fs, and a central wavelength of 1030nm.

[0013] A further technical solution of the present invention is: the spectrum shaping system comprises a focusing lens, a nonlinear medium and a collimating lens arranged in sequence along the optical path; the material of the nonlinear medium is a BIBO crystal, the length of the BIBO crystal is 13 mm, the phase matching conditions are: θ=0°, φ=90°, and the phase mismatch is △k=77.5 mm-1;

[0014] The incident horizontally polarized light is focused by a focusing lens onto a nonlinear medium, and after the spectrum is broadened by the nonlinear effect, it is collimated and shaped by a collimating lens. After shaping, the light beam is incident on a broadening module.

[0015] A further technical solution of the present invention is: the stretching module comprises a polarization beam splitter, a first optical isolation system, a pulse stretcher, a third TFP mirror, and a second optical isolation system which are sequentially arranged along the optical path, wherein the first optical isolation system and the second optical isolation system are arranged such that the polarization of the light beam is rotated 90° after the light beam passes in the forward direction, and the polarizations of the light beam remain unchanged when the light beam passes in the reverse direction; the shaped light beam is converted into vertically polarized light after passing through the polarization beam splitter and the first optical isolation system and is incident on the pulse stretcher, and the pulse of the polarized light is stretched to the order of hundreds of ps in the pulse domain by the pulse stretcher, the stretched light beam is reflected and passes through the first optical isolation system again, and is reflected to the second optical isolation system via the polarization beam splitter and the third TFP mirror, and the stretched light beam is converted into horizontally polarized light by the second optical isolation system and enters the amplification module.

[0016] A further technical solution of the present invention is: the pulse stretcher is a concentric stretcher based on a transmission grating pair; the line density of the transmission grating pair is 1600L / mm, and both surfaces thereof are coated with an anti-reflection film with a central wavelength of 1040nm.

[0017] A further technical solution of the present invention is: the amplification module comprises a first TFP mirror, an electro-optical modulation device, a first plane reflector, a second TFP mirror, a first concave mirror, a second concave mirror, a third concave mirror, a first dichroic mirror, a laser crystal, a second dichroic mirror, a fourth concave mirror, and a second plane reflector, which are sequentially arranged along the optical path; by applying a quarter-wave voltage to the electro-optical modulation device so that the polarization direction of the optical pulse is rotated 90 degrees, the gain can be extracted back and forth in the amplification module for many times until the quarter-wave voltage on the electro-optical modulation device is removed, the optical pulse passes through the first plane reflector and then passes through the electro-optical modulation device again to change from vertically polarized light to horizontally polarized light, and is guided out of the cavity through the first TFP mirror to obtain an amplified light beam;

[0018] The laser crystal includes two laser gain crystals, which are CaYAlO4 crystals doped with Yb3+, and their surfaces are coated with 980nm-1100nm anti-reflection films; and the laser gain crystals are orthogonally placed, and their two optical axes are placed perpendicularly on a water-cooled copper block.

[0019] A further technical solution of the present invention is: the TFP incident angles of the first TFP mirror and the second TFP mirror are 65°, and the TFP incident angle of the third TFP mirror is 45°, and within the coating range of 1010nm-1060nm, it has high transmittance to p light and high reflection to s light.

[0020] A further technical solution of the present invention is: the pulse compression module includes a high-reflection mirror and a pulse compressor arranged in sequence along the optical path; the polarization state of the amplified light beam remains unchanged after passing through the second optical isolation system; it is transmitted through the third TFP mirror and passes above the high-reflection mirror, and is incident on the pulse compressor for compression; the compressed light beam is then reflected by the high-reflection mirror to derive a compressed pulse.

[0021] A further technical solution of the present invention is: the gain energy adjustment module includes a first pump source, a first optical coupling system, a second pump source, and a second optical coupling system, wherein the first pump source outputs a pump laser which is collimated and focused to a laser crystal through the first optical coupling system, and the second pump source outputs a pump laser which is collimated and focused to another laser crystal through the second optical coupling system.

[0022] A pulse amplification method of a short pulse regenerative amplifier based on spectrum shaping, the specific steps are as follows:

[0023] The seed light source outputs an initial pulse light beam;

[0024] The initial pulse beam is incident on the spectrum shaping system to complete the nonlinear effect spectrum broadening and collimation shaping;

[0025] The collimated and shaped pulse beam is incident on the stretching module, which adjusts the pulse beam into vertical polarized light and horizontal polarized light in sequence, and stretches the vertical polarized light pulse in time domain to the order of hundreds of ps.

[0026] After the horizontally polarized light is incident on the amplification module, a quarter-wave voltage is applied to the electro-optical modulator in the amplification module, so that the horizontally polarized light makes multiple round trips in the amplification module to extract gain and output an amplified pulse light signal;

[0027] The amplified pulse light signal is compressed by a pulse compression module and then exported.

[0028] Beneficial Effects

[0029] The beneficial effects of the present invention are as follows: the present invention is a narrow pulse width high power regenerative amplifier based on spectrum shaping, a spectrum shaping system is directly arranged after a seed light source, and the seed pulse can be widened by utilizing the cascade second-order nonlinear effect, thereby ensuring a seed spectrum with sufficient bandwidth; at the same time, the laser gain crystal of the present invention uses two ytterbium-doped laser crystals placed vertically with different optical axes, and according to the gains of different axial directions of the crystal, a gain spectrum that covers the seed spectrum bandwidth and can reduce the gain narrowing effect can be provided, and combined with a stretcher and a compressor based on a transmission grating, a laser amplification output with a pulse width less than 100 fs and an average power greater than 50 W can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1A schematic diagram of the structure of a regenerative amplifier according to an embodiment of the present invention;

[0031] Figure 2 Schematic diagram of the structure of the spectrum shaping system according to an embodiment of the present invention;

[0032] Figure 3 A schematic diagram of the laser crystal structure according to an embodiment of the present invention;

[0033] Figure 4 Schematic diagrams of the tangential and placement directions of laser gain crystals according to an embodiment of the present invention, wherein (a) is a schematic diagram of the placement direction of the first laser crystal, and (b) is a schematic diagram of the placement direction of the second laser crystal;

[0034] Figure 5 The gain spectrum of the laser gain crystal of the embodiment of the present invention is a superposition of the two-axis emission cross sections;

[0035] Figure 6 Spectra of the seed light source and the spectrum of the shaped light source according to an embodiment of the present invention, wherein (a) is a spectrum diagram of the seed light source, and (b) is a spectrum diagram of the shaped light source;

[0036] Explanation of the accompanying drawings: 1. seed light source; 2. spectrum shaping system; 3. polarization beam splitter; 4. first optical isolation system; 5. pulse stretcher; 6. third TFP mirror; 7. second optical isolation system; 8. first TFP mirror; 9. electro-optic modulation device; 10. first plane reflector; 11. second TFP mirror; 12. first concave mirror; 13. second concave mirror; 14. third concave mirror; 15. first dichroic mirror; 16. laser crystal; 17. second dichroic mirror; 18. fourth concave mirror; 19. second plane reflector; 20. first pump source; 21. first optical coupling system; 22. second pump source; 23. second optical coupling system; 24. high reflective mirror; 25. pulse compressor; 2a. focusing lens; 2b. nonlinear medium; 2c. collimating lens; 16a. first laser crystal; 16b. second laser crystal. DETAILED DESCRIPTION

[0037] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0038] Based on the different gains of different spectral components of input pulses within the gain bandwidth of existing amplifiers, the input pulse spectrum will be lost after multiple gains, that is, the gain narrowing phenomenon, and it is difficult to obtain a shorter pulse width, which limits the application of lasers in some fields. The present invention provides a short pulse regeneration amplifier based on spectrum shaping, including a seed light source, a spectrum shaping system, a broadening module, an amplification module, and a pulse compression module arranged in sequence along an optical path, wherein an initial pulse light beam is output through the seed light source; the initial pulse light beam is subjected to nonlinear effect broadening and collimation shaping through the spectrum shaping system; the collimated and shaped pulse light beam is adjusted to vertical polarized light and horizontal polarized light in sequence through the broadening module, and the pulse time domain width is broadened to the order of hundreds of ps when it is in the vertical polarized light; the incident horizontally polarized light is extracted from the gain in its regeneration cavity multiple times through the amplification module, and an amplified pulse light signal is output; the laser gain energy in the amplification module is controlled by a gain energy adjustment module; and the amplified pulse light signal is compressed and exported through the pulse compression module.

[0039] The above technical solution is further described below with reference to the accompanying drawings and examples:

[0040] In one embodiment, referring to Figure 1 As shown, a short pulse regenerative amplifier based on spectrum shaping includes: a seed light source 1, a spectrum shaping system 2, a polarization beam splitter 3, a first optical isolation system 4, a pulse stretcher 5, a third TFP mirror 6, a second optical isolation system 7, a first TFP mirror 8, an electro-optical modulation device 9, a first plane reflector 10, a second TFP mirror 11, a first concave mirror 12, a second concave mirror 13, a third concave mirror 14, a first dichroic mirror 15, a laser crystal 16, a second dichroic mirror 17, a fourth concave mirror 18, a second plane reflector 19, a first pump source 20, a first optical coupling system 21, a second pump source 22, a second optical coupling system 23, a high-reflection mirror 24 and a pulse compressor 25.

[0041] The first pump source 20 outputs pump laser, which is collimated and focused to the laser crystal 16 via the first optical coupling system 21 . The second pump source 22 outputs pump laser, which is collimated and focused to the laser crystal 16 via the second optical coupling system 23 .

[0042] The seed light source 1 provides horizontal polarized light, which is shaped by the spectrum shaping system 2. After the shaping, the light beam passes through the polarization beam splitter 3 and the first optical isolation system 4 and becomes vertically polarized light. The vertically polarized light is incident on the pulse stretcher 5, and the pulse time domain of the vertically polarized light is stretched to the order of hundreds of ps. The stretched light beam is re-reflected to the first optical isolation system 4, and is reflected to the second optical isolation system 7 via the polarization beam splitter 3 and the third TFP mirror 6. The second optical isolation system 7 converts the stretched light beam into horizontally polarized light, and then passes through the first TFP mirror 8 and the one without a quarter-wave voltage in turn. The light beam passes through the electro-optical modulator 9 without a quarter-wave voltage, and the polarization state is rotated 90° to become vertical polarized light after passing through the electro-optical modulator twice. After passing through, a quarter-wave voltage is applied to the electro-optical modulator 9, and then the light beam is reflected by the first TFP mirror 8, the second TFP mirror 11, the first concave mirror 12, the second concave mirror 13, the third concave mirror 14 and the first dichroic mirror 15 in sequence, and then the gain is extracted by the laser crystal 16, and then the light beam is incident on the second plane reflector 19 through the second dichroic mirror 17 and the fourth concave mirror 18; The angle of the second plane reflector 19 is adjusted to make the incident light beam return along the original path, pass through the second dichroic mirror 17 and the fourth concave mirror 18, and then pass through the laser crystal 16 to extract the gain. Then, after being reflected by the first dichroic mirror 15, the third concave mirror 14, the second concave mirror 13, the first concave mirror 12, the second TFP mirror 11 and the first TFP mirror 8, the light beam passes through the electro-optical modulator 9 to which a quarter-wave voltage is applied, and then passes through the electro-optical modulator 9 to which a quarter-wave voltage is applied again after being reflected by the first plane reflector 10. The polarization direction of the light beam remains unchanged after passing through the electro-optical modulator 9 twice, and the light beam is repeatedly extracted in the regeneration cavity. The gain is taken until the quarter-wave voltage on the electro-optical modulator 9 is removed. The light passes through the first plane reflector 10 and then passes through the electro-optical modulator 9 again to change from vertically polarized light to horizontally polarized light, and is led out of the cavity through the first TFP mirror 8 to obtain an amplified light beam. The amplified light beam passes through the second optical isolation system 7 and its polarization state remains unchanged. It is transmitted through the third TFP mirror 6 and passes over the high-reflection mirror 24, and is incident on the pulse compressor 25 for compression. The pulse compressor 25 is set to have an incident height higher than the height of the outgoing light beam. The compressed light beam is reflected by the high-reflection mirror 24 to complete the pulse light compression and lead out the compressed pulse light.

[0043] In one embodiment, the seed light source 1 is a light source based on an ytterbium-doped medium, the maximum output power of the seed light source 1 is 7 W, the pulse width is 122 fs, and the central wavelength is 1030 nm.

[0044] In one embodiment, referring to Figure 2As shown, the spectrum shaping system 2 includes: a focusing lens 2a, a nonlinear medium 2b and a collimating lens 2c; the horizontally polarized light is focused to the nonlinear medium 2b by the focusing lens 2a, and after the spectrum is broadened by the nonlinear effect, it is collimated and shaped by the collimating lens 2c, and the shaped light beam is incident on the polarization beam splitter 3.

[0045] Preferably, the material of the nonlinear medium 2b is BIBO crystal, the length of the BIBO crystal is 13 mm, the phase matching conditions are: θ = 0°, φ = 90°, and the phase mismatch is △k = 77.5 mm -1 .

[0046] In one embodiment, the surface of the polarization beam splitter prism is coated with a 1028-1064 nm anti-reflection film, which can pass p-polarized light and reflect s-polarized light.

[0047] In one embodiment, the first optical isolation system 4 and the second optical isolation system 7 are configured to rotate the polarization by 90° after passing through in the forward direction, and to keep the polarizations unchanged in the reverse direction.

[0048] In one embodiment, the pulse stretcher 5 is a concentric stretcher based on a transmission grating pair, which is used to stretch the seed pulse in time domain to the order of hundreds of ps.

[0049] Preferably, the line density of the transmission grating pair is 1600 L / mm, and both surfaces of the transmission grating pair are coated with an anti-reflection film with a central wavelength of 1040 nm.

[0050] In one embodiment, the TFP incident angles of the first TFP mirror 8 and the second TFP mirror 11 are 65°, and the TFP incident angle of the third TFP mirror 6 is 45°. Within the coating range of 1010nm-1060nm, the p-light is highly transparent and the s-light is highly reflective.

[0051] In one embodiment, the electro-optical modulator 9 is used to change the polarization state of the laser in the cavity. It is set so that when no quarter-wave voltage is applied, the polarization direction of the light beam rotates 45° each time it passes through the electro-optical modulator 9, and when a quarter-wave voltage is applied, the polarization direction of the light beam rotates 90° each time it passes through the electro-optical modulator 9.

[0052] In one embodiment, the reflectivity R of the first plane reflector 10 and the second plane reflector 19 is greater than 99.9%, and the first concave mirror 12, the second concave mirror 13, the third concave mirror 14 and the fourth concave mirror 18 are used to control the size of the laser mode at the gain crystal. In this embodiment, the relative distances of the first concave mirror 12, the second concave mirror 13, the third concave mirror 14 and the fourth concave mirror 18 are controlled so that the laser beam waist in the regeneration cavity is respectively located on two laser crystals 16, ensuring good matching between the pump light spot and the seed laser spot on the laser crystal 16, so that the seed pulse obtains a higher gain when it travels back and forth to the laser crystal 16.

[0053] In one embodiment, the surfaces of the first dichroic mirror 15 and the second dichroic mirror 17 are coated with a high-transmission film for 900 - 980 nm and a high-reflection film for 1020 - 1200 nm.

[0054] In one embodiment, referring to Figure 3 as shown, the laser crystal 16 includes two laser gain crystals, namely a first laser crystal 16a and a second laser crystal 16b.

[0055] Preferably, the laser gain crystal is a CaYAlO 3+ crystal doped with rare earth ion ytterbium (Yb 4 ), and the surfaces of the laser gain crystals are all coated with an antireflection film for 980 nm - 1100 nm.

[0056] Preferably, the laser gain crystals are vertically cut, and the two optical axes are vertically placed on the water-cooled copper block.

[0057] Referring to Figure 4 as shown, in this embodiment, the schematic diagram of the tangential and placement directions of the laser gain crystals, Figure 4 where (a) is the schematic diagram of the placement direction of the first laser crystal 16a, Figure 4 and (b) is the schematic diagram of the placement direction of the second laser crystal 16b. The laser directions all propagate along the a-axis of the crystal, but the laser polarization directions correspond to the a-axis and c-axis of the crystal respectively. Figure 5 This is the gain spectrum obtained by superimposing the emission cross-sections of the two axes of the laser gain crystal in this embodiment. The gain spectrum is saddle-shaped, which is very beneficial for offsetting the influence of gain narrowing during the amplification process, so as to obtain an amplified pulse with a wider spectrum.

[0058] In one embodiment, the first pump source 20 and the second pump source 22 are semiconductor lasers with fiber-coupled output.

[0059] Preferably, the maximum output powers of the first pump source 20 and the second pump source 22 are 130 W, the central wavelength is 981 nm, the numerical aperture is 0.15, and the fiber core diameter is 105 μm.

[0060] In one embodiment, the first optical coupling system 21 and the second optical coupling system 23 are 1:4 optical coupling systems, which are used to collimate and focus the pump laser to the laser crystal 16.

[0061] In one embodiment, the pulse compressor 25 is a compressor based on a transmission grating pair, which is used to compress the amplified pulse to the femtosecond level.

[0062] Preferably, the groove density of the transmission grating pair is 1600 L / mm, and the two surfaces of the transmission grating pair are coated with an antireflection film with a central wavelength of 1040 nm.

[0063] In one embodiment, a pulse amplification method of a short pulse regenerative amplifier based on spectrum shaping comprises the following specific steps:

[0064] Step 1: The seed light source outputs an initial pulse beam;

[0065] Step 2: The initial pulse beam is incident on the spectrum shaping system to complete nonlinear effect spectrum broadening and collimation shaping;

[0066] Step 3: The collimated and shaped pulse beam is incident on the stretching module, which adjusts the pulse beam into vertically polarized light and horizontally polarized light in sequence, and stretches the vertically polarized light pulse in the time domain to the order of hundreds of ps;

[0067] Step 4: After the horizontally polarized light is incident on the amplification module, a quarter-wave voltage is applied to the electro-optical modulator in the amplification module, so that the horizontally polarized light makes multiple round trips in the amplification module to extract gain and output an amplified pulse light signal;

[0068] Step 5: The amplified pulse light signal is compressed by a pulse compression module and then exported.

[0069] In one embodiment, referring to Figure 6 As shown, the spectrum of the seed light source 1 and the spectrum of the light source after shaping, Figure 6 (a) is the spectrum of seed light source 1. Figure 6 (b) is the spectrum of the light source after shaping; when the seed light source 1 outputs an average power of 7W, a spectrum half-width of 15nm, and a pulse width of 122fs, after the spectrum system, the output average power is 6W, the spectrum half-width is 56nm, the pulse width is 48fs, and the optical-to-optical conversion efficiency is 85.7%. After shaping, the spectrum is significantly broadened and saddle-shaped, which is very helpful to offset the effect of gain narrowing during the amplification process, thereby obtaining an amplified pulse with a wider spectrum.

[0070] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A short pulse regenerative amplifier based on spectrum shaping, characterized in that: It includes a seed light source, a spectrum shaping system, a stretching module, an amplification module, and a pulse compression module arranged in sequence along the optical path. Outputting an initial pulse light beam through the seed light source; The spectrum shaping system is used to perform nonlinear effect spectrum broadening and collimation shaping on the initial pulse beam; The collimated and shaped pulse beam is adjusted to vertical polarized light and horizontal polarized light in sequence by the stretching module, and when it is in the vertical polarized light, its pulse time domain width is stretched to the order of hundreds of ps; The amplification module extracts the gain of the incident horizontally polarized light by making multiple round trips in the regeneration cavity, and outputs an amplified pulse light signal; the laser gain energy in the amplification module is controlled by the gain energy adjustment module; The amplified pulse light signal is compressed and exported through the pulse compression module.

2. A short pulse regenerative amplifier based on spectrum shaping according to claim 1, characterized in that: The seed light source is a light source based on ytterbium-doped medium, with a maximum output power of 7W, a pulse width of 122fs, and a central wavelength of 1030nm.

3. A short pulse regenerative amplifier based on spectrum shaping according to claim 1, characterized in that: The spectrum shaping system comprises a focusing lens, a nonlinear medium and a collimating lens arranged in sequence along the optical path; the material of the nonlinear medium is a BIBO crystal, the length of the BIBO crystal is 13 mm, the phase matching conditions are: θ=0°, φ=90°, and the phase mismatch is △k=77.5 mm-1; The incident horizontally polarized light is focused by a focusing lens onto a nonlinear medium, and after the spectrum is broadened by the nonlinear effect, it is collimated and shaped by a collimating lens. After shaping, the light beam is incident on a broadening module.

4. The short pulse regenerative amplifier based on spectrum shaping according to claim 1, characterized in that: The stretching module comprises a polarization beam splitter, a first optical isolation system, a pulse stretcher, a third TFP mirror, and a second optical isolation system which are sequentially arranged along the optical path, wherein the first optical isolation system and the second optical isolation system are arranged so that the polarization of the light beam rotates 90° after passing through in the forward direction, and the polarizations of the light beam remain unchanged when passing through in the reverse direction; the shaped light beam is converted into vertically polarized light after passing through the polarization beam splitter and the first optical isolation system and is incident on the pulse stretcher, and the pulse of the polarized light is stretched to the order of hundreds of ps in the pulse domain by the pulse stretcher, the stretched light beam is reflected and passes through the first optical isolation system again, and is reflected to the second optical isolation system via the polarization beam splitter and the third TFP mirror, and the stretched light beam is converted into horizontally polarized light by the second optical isolation system and enters the amplification module.

5. A short pulse regenerative amplifier based on spectrum shaping according to claim 4, characterized in that: The amplification module comprises a first TFP mirror, an electro-optical modulation device, a first plane reflector, a second TFP mirror, a first concave mirror, a second concave mirror, a third concave mirror, a first dichroic mirror, a laser crystal, a second dichroic mirror, a fourth concave mirror, and a second plane reflector, which are sequentially arranged along the optical path. By applying a quarter-wave voltage to the electro-optical modulation device, the polarization direction of the optical pulse is rotated by 90 degrees, and the gain can be extracted back and forth in the amplification module for many times until the quarter-wave voltage on the electro-optical modulation device is removed, and the optical pulse is converted from vertically polarized light to horizontally polarized light after passing through the first plane reflector and passing through the electro-optical modulation device again, and is guided out of the cavity through the first TFP mirror to obtain an amplified light beam; The laser crystal includes two laser gain crystals, which are CaYAlO4 crystals doped with Yb3+, and their surfaces are coated with 980nm-1100nm anti-reflection films; and the laser gain crystals are orthogonally placed, and their two optical axes are placed perpendicularly on a water-cooled copper block.

6. A short pulse regenerative amplifier based on spectrum shaping according to claim 5, characterized in that: The TFP incident angles of the first TFP mirror and the second TFP mirror are 65°, and the TFP incident angle of the third TFP mirror is 45°. Within the coating range of 1010nm-1060nm, the mirror has high transmittance to p-light and high reflection to s-light.

7. The short pulse regenerative amplifier based on spectrum shaping according to claim 5, characterized in that: The gain energy adjustment module comprises a first pump source, a first optical coupling system, a second pump source and a second optical coupling system, wherein the pump laser output by the first pump source is collimated and focused to a laser crystal through the first optical coupling system, and the pump laser output by the second pump source is collimated and focused to another laser crystal through the second optical coupling system.

8. The short pulse regenerative amplifier based on spectrum shaping according to claim 1, characterized in that: The pulse compression module includes a high-reflection mirror and a pulse compressor arranged in sequence along the optical path. The polarization state of the amplified light beam remains unchanged after passing through the second optical isolation system, and is transmitted through the third TFP mirror and passes above the high-reflection mirror, and is incident on the pulse compressor for compression. The compressed light beam is then reflected by the high-reflection mirror to derive a compressed pulse.

9. A pulse amplification method of a regenerative amplifier based on spectrum shaping according to any one of claims 1 to 8, characterized in that The specific steps are as follows: The seed light source outputs an initial pulse light beam; The initial pulse beam is incident on the spectrum shaping system to complete the nonlinear effect spectrum broadening and collimation shaping; The collimated and shaped pulse beam is incident on the stretching module, which adjusts the pulse beam into vertical polarized light and horizontal polarized light in sequence, and stretches the vertical polarized light pulse in time domain to the order of hundreds of ps. After the horizontally polarized light is incident on the amplification module, a quarter-wave voltage is applied to the electro-optical modulator in the amplification module, so that the horizontally polarized light makes multiple round trips in the amplification module to extract gain and output an amplified pulse light signal; The amplified pulse light signal is compressed by a pulse compression module and then exported.

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