Combination of stimulated brillouin scattering and stimulated raman scattering for compressing ultra-short pulse lasers

Abstract

The application is a super-short pulse laser compressed by stimulated Brillouin scattering and stimulated Raman scattering, comprising a pump source, an optical isolation system, a half-wave plate, a first polarizer, a SBS pulse width compression system with adjustable pulse width, a first mirror and an SRS generation and amplification system, wherein the single-longitudinal-mode laser emits pump light which passes through the optical isolation system, the half-wave plate and the first polarizer in sequence and then enters the SBS pulse width compression system; the pump light is compressed into hundreds of picosecond laser in the SBS pulse width compression system, and the compressed hundreds of picosecond laser is reflected by the first polarizer and the first mirror and then enters the SRS generation and amplification system for further compression and amplification. The technical scheme of combining the SBS pulse width compression technology and the SRS pulse width compression technology overcomes the compression limit of the SBS pulse width compression technology, achieves a laser pulse output with narrower pulse width than the Q-switching technology and higher energy than the mode-locked technology.

Description

Technical Field

[0001] This invention relates to the field of high-energy short-pulse laser technology, and in particular to a compressed ultrashort-pulse laser combining stimulated Brillouin scattering and stimulated Raman scattering. Background Technology

[0002] Ultrashort pulse lasers have wide applications in many fields such as impact dynamics, laser precision ranging, ultra-long-range lidar, laser medical instruments, and laser micromachining. In particular, high-energy ultrashort pulse lasers are of great significance for promoting industrial processing and cutting-edge science.

[0003] There are currently three main methods for obtaining short-pulse lasers: (1) Q-switching technology, which can obtain sub-nanosecond short-pulse lasers by shortening the cavity length, and can obtain sub-nanosecond high-energy lasers by combining traveling wave amplification [e.g., invention patent publication number: CN110880672B, patent name: a high repetition rate high-energy nanosecond-level pulse laser and its usage method], but this method cannot obtain even shorter pulses; (2) Mode-locking technology, which can obtain ultra-short and ultra-fast pulses from femtosecond to picosecond, but the pulse energy generated is relatively small, usually in the nanojoule to microjoule range, and the subsequent amplification is relatively complex [e.g., invention patent publication number: CN101562310, patent name: passive mode-locked picosecond laser]; (3) Stimulated scattering pulse width compression technology, which usually compresses nanosecond pulses to the hundreds of picosecond range through stimulated Brillouin scattering (SBS), which can obtain high-energy hundreds of picosecond lasers, but due to physical limitations, it cannot obtain ultra-short and ultra-fast pulse lasers. This invention utilizes a combination of SBS and stimulated Raman scattering (SRS) compression technology, which balances the high energy conversion efficiency of SBS with the short compression limit of SRS, to effectively generate high-energy ultrashort pulse lasers. This method is simple in structure, low in cost, and highly applicable to engineering, making it a very effective technique for generating high-energy ultrashort pulses. Summary of the Invention

[0004] This invention provides a compressed ultrashort pulse laser combining stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS). By combining SBS and SRS pulse width compression techniques, it overcomes the compression limit of SBS pulse width compression technology, achieving a narrower pulse width than Q-switching and a higher energy laser pulse output than mode-locking. At the same time, a temperature control system is introduced to achieve continuous pulse width adjustment.

[0005] A combined stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) compressed ultrashort pulse laser comprises: a pump source 1, an optical isolation system 2, a half-wave plate 3, a first polarizer 4, and a pulse width-adjustable SBS pulse width compression system 5. The laser further comprises a first reflector 6 and an SRS generation and amplification system 7.

[0006] In this system, a single-longitudinal-mode laser, acting as pump source 1, emits pump light that passes sequentially through an optical isolation system 2, a half-wave plate 3, and a first polarizer 4 before entering an SBS pulse width compression system 5. The pump light is compressed into a picosecond laser in the SBS pulse width compression system 5. The compressed picosecond laser is then reflected by the first polarizer 4 and the first mirror 6 before entering an SRS generation and amplification system 7 for further compression and amplification.

[0007] The SRS generation and amplification system 7 is used to compress the picosecond light generated by the SBS pulse width compression system 5. The SRS generation and amplification system 7 includes a beam splitter 7-1, a second reflecting mirror 7-2, a third reflecting mirror 7-3, a narrowband filter 7-4, an SRS generation cell 7-5, a first dichroic mirror 7-6, a first SRS amplification cell 7-7, and a second dichroic mirror 7-8. After the picosecond laser generated by the SBS pulse width compression system 5 enters the SRS generation and amplification system 7, it is split by the beam splitter 7-1: one beam is reflected by the first dichroic mirror 7-6 and enters the SRS generation cell 7-5. Forward stimulated Raman scattering occurs in the SRS generation cell 7-5, generating a forward-propagating Stokes seed beam. This beam passes through the narrowband filter 7-4, is reflected by the third mirror 7-3, and then passes through the first dichroic mirror 7-6 into the first SRS amplification cell 7-7. Another beam is reflected by the second mirror 7-2 and the second dichroic mirror 7-8 into the first SRS amplification cell 7-7, where it meets the Stokes seed beam. Since the two beams satisfy the SRS phase-matching condition, the Stokes seed beam will extract the energy of the picosecond laser and amplify it before finally being output through the second dichroic mirror 7-8.

[0008] The laser also includes a fourth reflecting mirror 8, a fourth reflecting mirror 9, a second SRS amplification cell 10, and a third dichroic mirror 11. By deflecting the optical path, the unexhausted picosecond laser light is amplified and compressed a second time with the Stokes seed light after one amplification, so as to obtain a higher energy conversion efficiency. The Stokes seed light output from the second dichroic mirror 7-8 enters the second SRS amplification cell 10 through the fourth reflecting mirror 8 and the fourth reflecting mirror 9. The picosecond laser light coming out of the second dichroic mirror 7-8 is highly reflected by the first dichroic mirror 7-6 to the third dichroic mirror 11, and then highly reflected again in the second SRS amplification cell 10, where it meets the Stokes seed light again and undergoes a second amplification and compression, finally outputting a high-energy picosecond laser light.

[0009] The narrowband filter 7-4 filters out the remaining picosecond laser and higher-order Stokes components, retaining only the positive first-order Stokes component; the first dichroic mirror 7-6 and the second dichroic mirror 7-8 are both highly transparent to the positive first-order Stokes seed light and highly reflective to the picosecond laser.

[0010] The optical isolation system 2 consists of a second polarizer 2-1, a Faraday rotator 2-2, and a third polarizer 2-3. The SBS pulse width compression system 5 consists of a quarter-wave plate 5-1, an SBS pulse width compression cell 5-2, a TEC cooler 5-3, a temperature control module 5-4, and a concave mirror 5-5. The pump source 1 generates a single longitudinal mode pump light, which passes through the isolation system 2 to prevent the return light from damaging the resonant cavity. The pump light then passes through a half-wave plate 3, a first polarizer 4, and a quarter-wave plate 5-1 to become circularly polarized light. In the SBS pulse width compression cell 5-2, the SBS pulse width compression effect occurs, compressing the pump light to the picosecond level. The temperature in the SBS pulse width compression cell is controlled by adjusting the TEC cooler 5-3 and the temperature control module 5-4, making the output pulse width adjustable. The output picosecond laser is transmitted in reverse, separated by the first polarizer 4, and refracted back by the first mirror 6 into the SRS generation and amplification system 7.

[0011] The medium in the SBS pulse width compression cell 5-2 is a liquid heavy fluorocarbon series medium with a large range of phonon lifetime and gain coefficient variation with temperature, such as FC-72, FC-77, FC-87, FC-84, FC-70, FC-770, etc.

[0012] In a liquid medium, the phonon lifetime of the medium decreases as the temperature decreases. By cooling the medium, the output pulse can be narrowed. At the same time, by controlling the change in the medium temperature, it can become a pulse-adjustable output light source, thereby controlling the output pulse width of the SRS generation amplification system to be adjustable and ultimately achieving the narrowing of the output pulse.

[0013] The TEC cooling chip 5-3 should be selected as a device with high temperature regulation accuracy as possible in order to achieve more precise pulse width regulation. The temperature regulation range is -30 to 130 degrees Celsius. The regulation temperature should not be higher than the boiling point of the medium in the SBS pulse width compression cell 5-2. In order to obtain a more ideal output pulse width, the output pulse width of the pulse width adjustable SBS pulse width compression system 5 should be as low as possible below 2ns.

[0014] The SRS generation cell 7-5 adopts a forward SRS seed generation method. The position of the first SRS amplification cell 7-7 needs to ensure that the process of the picosecond laser and the Stokes seed light meeting and amplifying in opposite directions is in the Raman medium.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] 1. This invention provides a combined stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) compressed ultrashort pulse laser. By combining SBS and SRS, it overcomes the pulse compression limit of SBS pulse width compression technology, breaking through the picosecond level and achieving high-energy ultrashort pulse output. By adjusting the pulse width and time-domain waveform of the SBS output through temperature control, the final output parameters are controlled and optimized. By generating an amplified SRS structure, the pulse width is further transformed into an ultrashort pulse, achieving ultrashort compression of the SBS pulse width from sub-nanosecond to sub-picosecond, picosecond, and tens of picosecond levels.

[0017] 2. The ultrashort pulse laser provided by this invention obtains a high peak power picosecond laser by pre-compressing a high-energy nanosecond pulse using SBS. This avoids the use of focusing structures in subsequent SRS pulse width compression, solves the influence of higher-order Stokes light on pulse width compression, significantly improves energy conversion efficiency, and obtains picosecond pulse outputs in the order of hundreds of millijoules and tens of millijoules.

[0018] 3. The ultrashort pulse laser provided by this invention has a high energy conversion rate and single-mode output due to stimulated Brillouin scattering. The final output laser pulse is a single-mode laser, which can be applied to related fields that require single-mode high-energy picosecond lasers.

[0019] 4. The ultrashort pulse laser provided by the present invention can generate special wavelengths that are difficult to generate by other lasers due to the large wavelength frequency shift of stimulated Raman scattering, and the output is a single wavelength.

[0020] 5. The output of the SBS pulse width compression system in the ultrashort pulse laser provided by the present invention determines the final output to a certain extent, and the phonon lifetime of its stimulated Brillouin medium will decrease as the temperature decreases. By introducing a temperature regulation system to change the phonon lifetime of the Brillouin medium, the pulse width of the laser can be adjusted.

[0021] 6. The ultrashort pulse laser provided by the present invention does not require an active amplifier to amplify the laser pulse. It can generate high-energy laser pulse output simply by using the SBS pulse width compression system and the SRS generation and amplification system.

[0022] 7. The output of the SBS pulse width compression system is controlled to be a standard Gaussian waveform so that it can be input into the SRS amplification generation system. Considering the permanent damage and irreparability of solid SRS media, the output power of SBS needs to be strictly controlled so that the output range of SBS meets the damage threshold and Raman threshold. The SRS generation amplification system of this application generates forward Raman without using a focusing lens, avoiding crystal damage and reducing the influence of higher-order Stokes light. When secondary amplification is performed, there will be shorter pulses and higher energy conversion efficiency. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of one embodiment of the compressed ultrashort pulse laser combining stimulated Brillouin scattering and stimulated Raman scattering of the present invention.

[0024] Figure 2 This is a schematic diagram of another embodiment of the compressed ultrashort pulse laser combining stimulated Brillouin scattering and stimulated Raman scattering of the present invention.

[0025] Figure 3 This is a numerical simulation diagram of the back-facing Stokes light after being compressed and amplified by the pulse-width-adjustable SBS pulse width compression system in this embodiment.

[0026] Figure 4 This is a numerical simulation diagram of the final laser pulse output after compression and amplification by the SRS generation and amplification system in this embodiment.

[0027] Figure 5 The graph shows the measurement of the input pulse width (a), the output pulse width of the SBS pulse width compression system (b), and the final output pulse width (c) of the SRS generation amplification system for the ultrashort pulse laser provided by the present invention when the pump source pulse width is 8ns.

[0028] The attached diagram lists the components represented by each number as follows:

[0029] 1: Pump source; 2: Optical isolation system;

[0030] 3: Half-wave plate; 4: First polarizer;

[0031] 5: SBS pulse width compression system; 6: First reflecting mirror;

[0032] 7: SRS amplification system; 8: Fourth reflecting mirror;

[0033] 9: Fourth reflecting mirror; 10: Second SRS magnifying cell;

[0034] 11: Third dichroic mirror;

[0035] 2-1: Second polarizer; 2-2: Faraday rotator;

[0036] 2-3: Third polarizer;

[0037] 5-1: Quarter-wave plate; 5-2: SBS pulse width compression cell;

[0038] 5-3: TEC cooling element; 5-4: Temperature control module;

[0039] 5-5: Concave reflecting mirror;

[0040] 7-1: Beam splitter; 7-2: Second reflecting mirror;

[0041] 7-3: Third reflecting mirror; 7-4: Narrow-band filter;

[0042] 7-5: SRS generation cell; 7-6: First dichroic mirror;

[0043] 7-7: SRS magnifying cell; 7-8: Second dichroic mirror. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0045] This invention first achieves pulse width compression from nanoseconds to hundreds of picoseconds using SBS pulse width compression technology, and then achieves compression from hundreds of picoseconds to picoseconds using SRS pulse width compression technology. SBS pulse width compression allows SRS to avoid the use of mode-locked lasers, increasing its application value; while SRS pulse width compression technology overcomes the drawback of the large compression limit of SBS technology, enabling the entire system to output picosecond or even femtosecond pulses.

[0046] See Figure 1 A combined stimulated Brillouin scattering and stimulated Raman scattering compressed ultrashort pulse laser includes: a pump source 1, an optical isolation system 2, a half-wave plate 3, a first polarizer 4, a pulse width-adjustable SBS pulse width compression system 5, a first reflector 6, and an SRS generation and amplification system 7.

[0047] In this system, a single-longitudinal-mode laser, acting as pump source 1, emits pump light that sequentially passes through an optical isolation system 2, a half-wave plate 3, and a first polarizer 4 before entering an SBS pulse width compression system 5. The pump light is compressed into a picosecond laser beam in the SBS pulse width compression system 5. The compressed picosecond laser beam is then reflected by the first polarizer 4 and the first mirror 6 before entering an SRS generation and amplification system 7 for further compression and amplification.

[0048] The optical isolation system 2 consists of a second polarizer 2-1, a Faraday rotator 2-2, and a third polarizer 2-3. It allows incident light to pass through the optical isolation system 2 in one direction, while returning light, due to a change in polarization direction, cannot pass through polarizer 2-1, thus protecting the pump source 1. The polarizers are Brewster angle polarizers.

[0049] The input energy can be controlled by adjusting the half-wave plate 3 without changing the spot size and beam quality.

[0050] Furthermore, the SBS pulse width compression system 5 is used to compress the pulse width of the pump light. The SBS pulse width compression system 5 consists of a quarter-wave plate 5-1, an SBS pulse width compression cell 5-2, a TEC cooling chip 5-3, a temperature control module 5-4, and a concave reflector 5-5. After the pump light enters the SBS pulse width compression system 5, it is first converted into circularly polarized light by the quarter-wave plate 5-1, and then reflected and focused back into the SBS pulse width compression cell 5-2 by the concave reflector 5-5 to form an interference standing wave field. After this field is generated, it propagates towards the SBS and produces a picosecond laser. The picosecond laser returns along the optical path, and after passing through the quarter-wave plate 5-1, it is converted into linearly polarized light for output. Since it passes through the quarter-wave plate 5-1 twice, the picosecond laser is reflected by the first polarizer 4 and the first reflector 6 before entering the SRS generation amplification system 7.

[0051] SBS is limited by its long phonon lifetime. In liquid media, the phonon lifetime of the medium decreases as the temperature decreases. By cooling the medium, the output pulse can be narrowed. At the same time, by controlling the change in the medium temperature, it can become a pulse-adjustable output light source.

[0052] The medium in the SBS pulse width compression cell 5-2 is selected from liquid heavy fluorocarbon series media with a wide temperature variation range, such as FC-72, FC-77, FC-87, FC-84, FC-70, and FC-770. This allows the output pulse width to be adjustable by regulating the temperature of the medium in the cell through the TEC cooler 5-3 and the temperature control module 5-4. The phonon lifetime of the medium decreases as the temperature decreases; therefore, by cooling the medium, the final output pulse can be narrowed. Furthermore, by changing the temperature, the output pulse width of the SBS pulse width compression system can be adjusted, thereby controlling the adjustable output pulse width of the SRS generation amplification system.

[0053] Furthermore, the SRS generation and amplification system 7 is used to perform pulse width compression on the picosecond light generated by the SBS pulse width compression system 5. The SRS generation and amplification system 7 consists of a beam splitter 7-1, a second reflector 7-2, a third reflector 7-3, a narrowband filter 7-4, an SRS generation cell 7-5, a first dichroic mirror 7-6, a first SRS amplification cell 7-7, and a second dichroic mirror 7-8. The picosecond laser generated by the SBS pulse width compression system 5 enters the SRS generation and amplification system 7 and is split by the beam splitter 7-1. One beam is reflected by the first dichroic mirror 7-6 and enters the SRS generation cell 7-5, where forward SRS occurs. The forward-propagating Stokes seed light passes through the narrowband filter 7-4, is reflected by the third mirror 7-3, and then passes through the first dichroic mirror 7-6 into the first SRS amplification cell 7-7. The other beam is reflected by the second mirror 7-2 and the second dichroic mirror 7-8 and enters the first SRS amplification cell 7-7, where it meets the Stokes seed light in opposite directions. Since the two beams meet the SRS phase matching condition, the Stokes seed light will extract the energy of the picosecond laser and amplify it, and finally output it through the second dichroic mirror 7-8.

[0054] Among them, the SRS generation cell 7-5 adopts a method based on forward SRS seed generation. In this structure, forward SRS is the main component, and the back-direction Raman light will not be amplified in the amplification cell and will not encounter the pump light. Compared with back-direction SRS, forward SRS has higher conversion efficiency and has advantages such as not needing to adopt a focusing structure and not requiring input linewidth. Through subsequent amplification and compression in the first SRS amplification cell 7-7, high-energy picosecond laser output can be achieved.

[0055] The narrowband filter 7-4 filters out the remaining picosecond laser and higher-order Stokes components, retaining only the positive first-order Stokes components.

[0056] Among them, the first dichroic mirror 7-6 and the second dichroic mirror 7-8 are highly reflective of the picosecond laser generated by the SBS pulse width compression system 5 and highly transparent to the first-order Stokes seed light generated by the SRS generation cell 7-5.

[0057] The position of the first SRS amplification cell 7-7 needs to ensure that the amplification process of the picosecond laser and the Stokes seed light meeting and meeting in opposite directions occurs in the Raman medium.

[0058] Further, see Figure 2The SRS amplification system 7, based on the above structure, adds a fourth reflecting mirror 8, a fourth reflecting mirror 9, a second SRS amplification cell 10, and a third dichroic mirror 11. Through optical path deflection, the unexhausted picosecond laser light undergoes a second amplification and compression with the Stokes seed light after one amplification, achieving higher energy conversion efficiency. The Stokes seed light output from the second dichroic mirror 7-8 enters the second SRS amplification cell 10 via the fourth reflecting mirrors 8 and 9. The picosecond laser light exiting the second dichroic mirror 7-8 is highly reflected by the first dichroic mirror 7-6 to the third dichroic mirror 11, and then highly reflected again in the second SRS amplification cell 10, where it again encounters the Stokes seed light for a second amplification and compression, finally outputting a high-energy picosecond laser light.

[0059] This invention uses a picosecond laser generated by SBS pulse width compression technology as the input light for SRS pulse width compression technology, realizing the combined use of SBS and SRS, and ultimately achieving the goal of outputting ultrashort pulses using SRS pulse width compression technology.

[0060] The medium in the SBS pulse width compression cell 5-2 is one of the liquid heavy fluorocarbon series media such as FC-72, FC-77, FC-87, FC-84, FC-70, and FC-770. The cell lengths of the SBS pulse width compression cell 5-2, the SRS generation cell 7-5, and the first SRS amplification cell 7-7 vary from 0.5cm to 50cm depending on the medium and actual conditions. The focal length of the concave mirror 5-5 is 10 to 50cm. The medium in the two SRS amplification cells and the SRS generation cell is a Raman-active medium in solids, gases, and liquids such as Ba(NO3)2, H2, NH3, and CS2 with optical phonon lifetimes in the picosecond range.

[0061] Example 1: This example has the same structure as the specific implementation method described above. The SRS amplification system performs a single amplification and has the following parameters:

[0062] A single-longitudinal-mode laser serves as pump source 1, with an output wavelength of 1064 nm, a divergence angle of 0.35 mrad, and a peak power of 4 MW. The SBS pulse width compression cell 5-2 uses FC-770 as its dielectric (phonon lifetime of 600 ps, ​​Brillouin gain coefficient of 3.5 cm / GW at 1064 nm) and has a cell length of 100 cm. The concave mirror 5-5 has a focal length of 33 cm, and the distance between the concave mirror 5-5 and the SBS pulse width compression cell 5-2 is 10 cm. The gain medium of the SRS generation cell 7-5 and the first SRS amplification cell 7-7 is Ba(NO3)2 crystal. The cell length of the SRS generation cell 7-5 is 3 cm, and the cell length of the first SRS amplification cell 7-7 is 7.5 cm. Other types of devices are not limited; any device that can perform the above functions is acceptable. Numerical simulations of the picosecond laser generated by the SBS pulse width compression system 5 in this embodiment and the final output ultrashort pulse laser are as follows: Figure 3 and Figure 4 As shown, the final output ultrashort pulse laser has a pulse width of 160 ps.

[0063] Example 2: This example has the same structure as Example 1. Figure 5 The following are pulse width measurement diagrams when the output wavelength of pump source 1 is 1064nm and the pulse width is 8ns. (a) is the output pulse width measurement diagram of pump source 1, (b) is the output pulse width measurement diagram of the pulse width adjustable SBS pulse width compression system 5, and (c) is the final output pulse width measurement diagram of SRS generation amplification system 7. The pulse widths are 8ns, 711ps and 97ps, respectively.

[0064] Example 3: The TEC cooling chip 5-3 should be selected with high temperature regulation accuracy to achieve more precise pulse width regulation. The temperature regulation range is -30 to 130 degrees Celsius, and the regulation temperature should not exceed the boiling point of the medium in the SBS pulse width compression cell 5-2. Furthermore, to obtain a more ideal output pulse width, the output pulse width of the pulse-width adjustable SBS pulse width compression system 5 should be below 2ns as much as possible.

[0065] Unless otherwise specified, the model numbers of the various devices in this embodiment of the invention are not limited. Any device that can perform the above functions is acceptable, and any part not mentioned in this invention is applicable to the prior art.

Claims

1. A compressed ultrashort pulse laser combining stimulated Brillouin scattering and stimulated Raman scattering, comprising: The laser comprises a pump source, an optical isolation system, a half-wave plate, a first polarizer, and a pulse-width-adjustable SBS pulse-width compression system. Its distinguishing feature is that the laser further includes a first reflecting mirror and an SRS generation and amplification system. In this system, a single longitudinal mode laser emits pump light as the pump source, which then passes through an optical isolation system, a half-wave plate, and a first polarizer before entering the SBS pulse width compression system. The pump light is compressed into a picosecond laser in the SBS pulse width compression system. The compressed picosecond laser is then reflected by the first polarizer and the first mirror before entering the SRS generation and amplification system for further compression and amplification. The SRS generation and amplification system is used to compress the pulse width of the picosecond laser generated by the SBS pulse width compression system. The SRS generation and amplification system includes a beam splitter, a second mirror, a third mirror, a narrowband filter, an SRS generation cell, a first dichroic mirror, a first SRS amplification cell, and a second dichroic mirror. After the picosecond laser generated by the SBS pulse width compression system enters the SRS generation and amplification system, it is split by the beam splitter: one beam is reflected by the first dichroic mirror and enters the SRS generation cell, where forward stimulated Raman scattering occurs, generating a forward-propagating Stokes seed beam that passes through the narrowband filter, is reflected by the third mirror, and then passes through the first dichroic mirror to enter the first SRS amplification cell; the other beam is reflected by the second mirror and the second dichroic mirror and enters the first SRS amplification cell, where it meets the Stokes seed beam in the opposite direction. Since the two beams meet the SRS phase matching condition, the Stokes seed beam will extract the energy of the picosecond laser and amplify it, and finally output it through the second dichroic mirror. The narrowband filter filters out the remaining picosecond laser and higher-order Stokes components, retaining only the positive first-order Stokes component; both the first and second dichroic mirrors are highly transparent to the positive first-order Stokes seed light and highly reflective to the picosecond laser. The SRS generation cell adopts a method based on forward SRS seed generation. The position of the first SRS amplification cell needs to ensure that the process of the picosecond laser and the Stokes seed light meeting and amplifying in opposite directions is in the Raman medium. The SRS generation amplification system generates forward Raman without using a focusing lens, avoiding crystal damage and reducing the influence of high-order Stokes light. The output range of SBS needs to be between the damage threshold and the Raman threshold. There is no need for an active amplifier to amplify the laser pulse. High-energy laser pulse output can be generated simply by the SBS pulse width compression system and the SRS generation and amplification system, realizing the ultra-short compression of SBS pulse width from sub-nanosecond to sub-picosecond, picosecond, and tens of picoseconds.

2. The stimulated Brillouin scattering and stimulated Raman scattering combined compressed ultrashort pulse laser according to claim 1, characterized in that, The laser also includes a fourth reflecting mirror, a second SRS amplification cell, and a third dichroic mirror. By deflecting the optical path, the unexhausted picosecond laser light is amplified and compressed a second time with the Stokes seed light after being amplified once, so as to obtain a higher energy conversion efficiency. The Stokes seed light output from the second dichroic mirror passes through the fourth mirror and enters the second SRS amplification cell. The picosecond laser from the second dichroic mirror is highly reflected by the first dichroic mirror to the third dichroic mirror, and then highly reflected again into the second SRS amplification cell, where it meets the Stokes seed light again and undergoes a second amplification and compression, finally outputting a high-energy picosecond laser.

3. The stimulated Brillouin scattering and stimulated Raman scattering combined compressed ultrashort pulse laser according to claim 2, characterized in that, The SRS generation cell and the two SRS amplification cells are filled with Raman-active media with optical phonon lifetimes on the order of picoseconds.

4. The stimulated Brillouin scattering and stimulated Raman scattering combined compressed ultrashort pulse laser according to claim 3, characterized in that, The Raman active medium is one of Ba(NO3)2, H2, NH3, and CS2.

5. The stimulated Brillouin scattering and stimulated Raman scattering combined compressed ultrashort pulse laser according to claim 1, characterized in that, The optical isolation system consists of a second polarizer, a Faraday rotator, and a third polarizer. The SBS pulse width compression system consists of a quarter-wave plate, an SBS pulse width compression cell, a TEC cooler, a temperature control module, and a concave mirror. The pump source generates a single longitudinal mode pump light, which passes through the isolation system to prevent the return light from damaging the resonant cavity. The pump light then passes through a half-wave plate, the first polarizer, and the quarter-wave plate to become circularly polarized light. In the SBS pulse width compression cell, the SBS pulse width compression effect occurs, compressing the pump light to the picosecond level. The temperature in the SBS pulse width compression cell is controlled by adjusting the TEC cooler and the temperature control module, making the output pulse width adjustable. The output picosecond laser is transmitted in reverse, separated by the first polarizer, and refracted back by the first mirror to enter the SRS generation and amplification system.

6. The stimulated Brillouin scattering and stimulated Raman scattering combined compressed ultrashort pulse laser according to claim 5, characterized in that, The medium in the SBS pulse width compression cell is a liquid heavy fluorocarbon series medium with a large range of phonon lifetime and gain coefficient variation with temperature, specifically one of FC-72, FC-77, FC-87, FC-84, FC-70, and FC-770.

7. The stimulated Brillouin scattering and stimulated Raman scattering combined compressed ultrashort pulse laser according to claim 5, characterized in that, In a liquid medium, the phonon lifetime of the medium decreases as the temperature decreases. By cooling the medium, the output pulse can be narrowed. At the same time, by controlling the change in the medium temperature, it can become a pulse-adjustable output light source, thereby controlling the output pulse width of the SRS generation amplification system to be adjustable and ultimately achieving the narrowing of the output pulse.

8. The stimulated Brillouin scattering and stimulated Raman scattering combined compressed ultrashort pulse laser according to claim 5, characterized in that, TEC cooling chips are selected from devices with high temperature regulation accuracy in order to achieve more precise pulse width regulation. The temperature regulation range is -30 to 130 degrees Celsius. The regulation temperature cannot be higher than the boiling point of the medium in the SBS pulse width compression cell. In order to obtain a more ideal output pulse width, the output pulse width of the pulse width adjustable SBS pulse width compression system is below 2ns.

Images