Separation Pulse Laser Regenerative Amplification Device and Method

Abstract

The present invention discloses a separated pulse laser regenerative amplification device and method. The device includes a signal light coupling module and a separated pulse laser regenerative amplification module. The separated pulse laser regenerative amplification module includes a second polarization beam splitter and a third reflector. The second polarization beam splitter is adjacent to a second half-wave plate and is in the same column as the third reflector and the second half-wave plate. On one side of the second polarization beam splitter, a first quarter-wave plate, a Pockels cell, and a first reflector are sequentially arranged. On the other side of the second polarization beam splitter, a third half-wave plate, a first polarization separation pulse module, and a first nonlinear pulse amplification module are sequentially arranged. The method includes steps of signal light input, polarization beam splitting and pulse separation performed on the injected separated pulse laser regenerative amplification module, laser amplification, polarization beam combination, and regenerative amplification.

Description

Technical Field

[0001] The present invention relates to the field of ultrafast laser technology, and particularly to a split-pulse laser regenerative amplification device and method. Background Art

[0002] The development of ultrafast optics and high-field laser technology has provided new opportunities for many frontier researches and applications in physics and information science, and has become one of the most active research fronts in related fields; laser light sources developed based on ultrafast fiber and high-field laser technology, with their characteristics of ultra-high peak power, ultra-fast action process, ultra-high resolution accuracy, etc., have been realized in key fields of national economy and people's livelihood such as industrial processing, medical surgery, time-frequency transfer, etc.; moreover, it drives the development of some future high-tech industries and promotes the development and progress of many fields such as chemistry, materials science, condensed matter physics, nanoscience, biology, and medicine.

[0003] Currently, the mainstream ultrafast femtosecond laser technology for obtaining high peak power (megawatt level, 1 MW = 10^6 W) and high energy (millijoule level, 1 mJ = 10^-3 J) is the chirped regenerative amplification technology or chirped pulse multi-pass amplification technology based on Yb materials. The chirped pulse amplification technology was proposed and verified by Gérard Mourou and Donna Strickland in 1985. Based on the concept of time-for-power, the seed pulse is first temporally broadened and then pulse-amplified to avoid the time-frequency domain distortion and laser damage caused by the high peak power amplified pulse in the amplifier. Finally, the amplified pulse is temporally compressed. This technology has increased the laser peak power obtained by humans by nearly 6 orders of magnitude, reaching the petawatt level (1 PW = 10^12 W), and was commended with the Nobel Prize in Physics in 2018. However, in the chirped amplification system, the pulse broadening weakens the nonlinear effect during the amplification process, and the adverse effect of laser pulse gain narrowing becomes prominent, resulting in limited output pulse width, usually above 300 fs. On the other hand, chirped pulse amplification relies on optical fibers or spatial dispersion media (such as a large number of optical fibers, chirped fiber gratings with large dispersion, spatial diffraction gratings, etc.) to perform temporal modulation on the seed pulse, with high cost and large volume, affecting the practical application of the laser amplifier.

[0004] The split-pulse amplification technology, based on the concept of space-for-output power (pulse energy), spatially splits the seed light by means of polarization, lenses, etc. and temporally delays it to form 2n sub-pulse sequences, which can also reduce the peak power during the pulse amplification process and avoid nonlinear accumulation and amplifier damage. Currently, the split-pulse amplification technology is mostly seen in fiber laser amplifiers with limited output energy. Summary of the Invention

[0005] In view of the above deficiencies in the prior art, the purpose of the present invention is to provide a separated pulsed laser regenerative amplification device and method, so as to solve the problems of high cost, large volume and limited output energy existing in the existing separated pulsed amplification devices.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A separated pulsed laser regenerative amplification device includes a signal light coupling module and a separated pulsed laser regenerative amplification module; the signal light coupling module includes a first half-wave plate, a first polarization beam splitter, a first Faraday rotator and a second half-wave plate arranged in sequence; the separated pulsed laser regenerative amplification module includes a second polarization beam splitter and a third reflector, the second polarization beam splitter is adjacent to the second half-wave plate and is in the same column as the third reflector and the second half-wave plate; on one side of the second polarization beam splitter, a first quarter-wave plate, a Pockels cell and a first reflector are arranged in sequence, and on the other side of the second polarization beam splitter, a third half-wave plate, a first polarization separation pulse module and a first non-linear pulse amplification module are arranged in sequence;

[0008] The first polarization separation pulse module includes m polarization separation modules arranged at intervals, where m≥2, and each polarization separation module includes a polarization beam splitter, and a quarter-wave plate and a reflector are arranged in sequence on both sides of the polarization beam splitter; the distance between adjacent two polarization separation modules is the same, and the vertical distance between the two reflectors in the polarization separation module increases sequentially from the polarization separation module to the direction of the first non-linear pulse amplification module;

[0009] The separated pulsed laser regenerative amplification module is used to realize one-time pulse splitting, two-time laser amplification and one-time pulse combining of the signal light injected by the signal light coupling module through the reflection circuit of the second polarization beam splitter, the first quarter-wave plate, the Pockels cell, the first reflector, the Pockels cell, the first quarter-wave plate, the second polarization beam splitter, the third half-wave plate, the first polarization separation pulse module, the first non-linear pulse amplification module, the first polarization separation pulse module, the third half-wave plate and the second polarization beam splitter; and after the pulse combination, the combined pulsed signal light is reflected by the third reflector to the second polarization beam splitter, and then the signal light passes through the transmission circuit of the third half-wave plate, the first polarization separation pulse module, the first non-linear pulse amplification module, the first polarization separation pulse module, the third half-wave plate and the second polarization beam splitter, so as to realize the re-pulse splitting, two-time laser regenerative amplification and re-pulse combining of the signal light, and then the signal light is transmitted from the second polarization beam splitter and re-injected into the Pockels cell to complete one regenerative amplification cycle of the signal light;

[0010] The signal light coupling module is used to inject the seed pulse into the separated pulse laser regenerative amplification module. When the signal light passes through the separated pulse laser regenerative amplification module and completes multiple regenerative amplification cycles until gain saturation, it is reflected by the second half-wave plate, the first Faraday rotator of the signal light coupling module to the first polarization beam splitter, and then the regenerated and amplified laser pulse beam is output.

[0011] Further, the first non-linear pulse amplification module includes a first gain crystal, a second Faraday rotator and a second mirror; the second Faraday rotator is located between the first gain crystal and the second mirror, and the first gain crystal is adjacent to the polarization separation pulse module.

[0012] Further, the first non-linear pulse amplification module includes a third polarization beam splitter, a first gain crystal, a second mirror, a fourth mirror, a fourth half-wave plate, and a fifth mirror; the third polarization beam splitter, the fifth mirror and the first polarization separation pulse module are on the same straight line, and the third polarization beam splitter is located between the fifth mirror and the first polarization separation pulse module; the beam emission line formed by the third polarization beam splitter, the first gain crystal and the second mirror is perpendicular to the beam emission line formed by the third polarization beam splitter and the fifth mirror, and the first gain crystal is located between the third polarization beam splitter and the second mirror; the fourth mirror is located on one side of the second mirror, and the beam emission line formed by the fourth mirror, the fourth half-wave plate and the fifth mirror is parallel to the beam emission line formed by the third polarization beam splitter, the first gain crystal and the second mirror.

[0013] Further, the fourth half-wave plate can be replaced by a third Faraday rotator.

[0014] Further, the first non-linear pulse amplification module includes a third polarization beam splitter, a first gain crystal, a second mirror, two pairs of reflective diffraction gratings, a fourth mirror, a third Faraday rotator, and a fifth mirror; the third polarization beam splitter, the fifth mirror and the first polarization separation pulse module are on the same straight line, and the third polarization beam splitter is located between the fifth mirror and the first polarization separation pulse module; the beam emission line formed by the third polarization beam splitter, the first gain crystal and the second mirror is perpendicular to the beam emission line formed by the third polarization beam splitter and the fifth mirror, and the first gain crystal is located between the third polarization beam splitter and the second mirror; the two pairs of reflective diffraction gratings are located between the second mirror and the fourth mirror, and the beam emission line formed by the fourth mirror, the third Faraday rotator and the fifth mirror is parallel to the beam emission line formed by the third polarization beam splitter, the first gain crystal and the second mirror.

[0015] Further, the third mirror can be replaced by a second regenerative amplification module, and the second regenerative amplification module includes a sixth mirror, a fourth polarization beam splitter, a fifth half-wave plate, a second polarization separation pulse module, and a second nonlinear pulse amplification module arranged in sequence; the fourth polarization beam splitter corresponds to the second polarization beam splitter and is located in the same column; the sixth mirror and the first mirror are on the same side, and the fifth half-wave plate and the sixth mirror are respectively on two opposite sides of the fourth polarization beam splitter.

[0016] Further, the second nonlinear pulse amplification module includes a second gain crystal, a fourth Faraday rotator, and a seventh mirror arranged in sequence.

[0017] Further, the first gain crystal and the second gain crystal are laser crystals doped with ytterbium ions or neodymium ions.

[0018] A method for separating and regeneratively amplifying pulsed lasers, characterized by comprising: S1, input of signal light, injecting seed pulses in the ps magnitude into the separated pulsed laser regenerative amplification module through the signal light coupling module; the separated pulsed laser regenerative amplification module is as described in any one of claims 1-5; S2, performing polarization beam splitting and pulse separation on the inside of the separated pulsed laser regenerative amplification module. When performing polarization beam splitting on the pulsed laser, the signal light first reflects the s-polarized light through the second polarization beam splitter, and then successively passes through the first quarter-wave plate and the Pockels cell and is reflected by the first mirror. During the reflection process, by controlling the switching time of the Pockels cell, the reflected s-polarized light becomes P-polarized light after passing through the quarter-wave plate. After this P-polarized light passes through the second polarization beam splitter, the polarization direction of the incident P-polarized light is rotated by a set angle through the third half-wave plate, and the signal light is equally divided into P-polarized light and S-polarized light to achieve signal light beam splitting; the split polarized light is injected into the polarization separation module of the polarization film separation pulse module for pulse separation. When performing pulse separation, when the polarized light passes through the m polarization separation modules of the polarization film separation pulse module, it is divided into sub-pulses with orthogonal polarization between 2m adjacent pulses and with a time delay between pulses; S3, laser amplification, the separated sub-pulses are injected into the first non-linear pulse amplification module, and after two pulse signal amplifications in the first non-linear pulse amplification module, and the polarization direction of the sub-pulses is rotated by 90°, and they return along the original path; S4, polarization beam combining the amplified signal light. Specifically, the amplified sub-pulses are re-injected into the polarization film separation pulse module to achieve polarization beam combining and are recombined into a single amplified pulse signal light in the S-polarized state; S5, regeneratively amplifying the single amplified pulse signal light. Specifically, the amplified pulse signal light is reflected by the second polarization beam splitter to the third mirror, and then after being emitted back to the second polarization beam splitter by the third mirror, it successively passes through the third half-wave plate and the polarization film separation pulse module to achieve polarization beam splitting and pulse separation of the amplified pulse signal light. Then, after being amplified and reflected by the first non-linear pulse amplification module in sequence, it enters the polarization film separation pulse module to achieve pulse re-combining, and the signal light polarization returns to p-polarization again, and is transmitted from the second polarization beam splitter and re-injected into the Pockels cell to complete one regenerative amplification cycle; S6, precisely controlling the switching time of the Pockels cell, enabling the signal light to repeat the regenerative amplification cycle steps of S2-S5 until saturation of the gain. Then, after passing through the second half-wave plate, the first Faraday rotator of the signal light coupling module and being reflected by the first polarization beam splitter, the regeneratively amplified laser pulse beam is output.

[0019] Further, the third mirror can be replaced by the second regenerative amplification module as described above. After the seed pulse is injected into the separated pulse laser regenerative amplification module through the signal light coupling module, the signal light is sequentially subjected to pulse separation, laser amplification, and re-combination in S2 - S4, and then is reflected by the second polarization beam splitter to the fourth polarization beam splitter of the second regenerative amplification module. After the combined signal light is reflected to the fourth polarization beam splitter, it is reflected to the fifth half-wave plate and then sequentially enters the third polarization beam separation pulse module and the second non-linear pulse amplification module to realize pulse separation and laser amplification of the polarized light after combination, and the polarization direction of the sub-pulse rotates by 90°. After passing through the second non-linear pulse amplification module and the third polarization beam separation pulse module again to realize laser amplification and pulse combination, it projects out from the fourth polarization beam splitter, is reflected by the sixth mirror, and then passes through the fourth polarization beam splitter again, and sequentially enters the fifth half-wave plate, the third polarization beam separation pulse module, and the second non-linear pulse amplification module to realize pulse separation, amplification, reflection, and re-amplification, and then enters the third polarization beam separation pulse module to realize pulse combination, and then is reflected back to the second polarization beam splitter through the fourth polarization beam splitter, and undergoes pulse separation, laser amplification, and re-combination in S2 - S4 again, and then transmits out from the second polarization beam splitter and returns to the Pockels cell to complete a regenerative amplification cycle.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The signal light pulse can be divided into 2m sub-pulse components in the separation pulse module, which greatly improves the pulse duty cycle in the laser amplification process, and the pulse passes through the gain crystal multiple times, which is beneficial to realizing more efficient pulse amplification and reducing the power consumption of the laser.

[0022] 2. There is no need for expensive dispersion broadening media such as diffraction gratings, chirped Bragg fiber gratings, and volume Bragg gratings. The method of pulse separation and amplification has a more compact structure, lower cost, and can achieve millijoule-level pulse output.

[0023] 3. The dual-channel separated pulse regenerative amplification device and method utilize the characteristic that the radiation spectra of different gain crystals or the same type of gain crystals with different cutting directions are complementary, which can effectively suppress the gain narrowing effect in the regenerative amplification process and facilitate obtaining femtosecond pulses with higher peak power. Description of the Drawings

[0024] Figure 1 It is a schematic installation structure diagram of the single-channel separated pulse laser regenerative amplification device in Embodiment 1;

[0025] Figure 2 It is a schematic installation structure diagram of the single-channel separated pulse laser regenerative amplification device with a non-linear amplification loop mirror in Embodiment 2;

[0026] Figure 3 It is the installation structure diagram of the single-channel separated pulse laser regenerative amplifier device of the nonlinear amplifying loop mirror in Embodiment 3;

[0027] Figure 4 It is the installation diagram of the dispersion-compensated nonlinear amplifying loop mirror separated pulse laser regenerative amplifier device in Embodiment 4;

[0028] Figure 5 It is the schematic installation structure diagram of the two-channel same-crystal separated pulse laser regenerative amplifier device in Embodiment 5;

[0029] Figure 6 It is the schematic installation structure diagram of the two-channel two-crystal separated pulse laser regenerative amplifier device in Embodiment 6;

[0030] Figure 7 It is the schematic structure diagram of the first polarizer separated pulse module 206 in the embodiment;

[0031] Figure 8 It is the schematic structure diagram of the two-crystal placement structure with different placement directions in Embodiment 6;

[0032] Figure 9 It is the schematic diagram of the pulse amplification evolution process in the embodiment. Specific implementation manners

[0033] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents the selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0034] It should be noted that similar reference numerals and letters denote similar items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the figures, or the orientation or positional relationship in which the inventive product is customarily placed during use. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the present invention. In addition, the terms "first", "second", "third", etc. are only used for distinguishing descriptions and cannot be construed as indicating or implying relative importance. In addition, terms such as "horizontal" and "vertical" do not mean that the components are required to be absolutely horizontal or hanging, but can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined. In the description of the present invention, it should also be noted that unless otherwise clearly specified and limited, the terms "arranged", "installed", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0035] Embodiment 1:

[0036] As Figure 1 shown, the single-channel separation pulsed laser regeneration amplification device provided in this embodiment includes a signal light coupling module and a separation pulsed laser regeneration amplification module; the signal light coupling module includes a first half-wave plate 101, a first polarization beam splitter 102, a first Faraday rotator 103, and a second half-wave plate 104 arranged in sequence;

[0037] the separation pulsed laser regeneration amplification module includes a second polarization beam splitter 201 and a third mirror 210. The second polarization beam splitter 201 is adjacent to the second half-wave plate 104 and is in the same column as the third mirror 210 and the second half-wave plate 104; on one side of the second polarization beam splitter 201, a first quarter-wave plate 202, a Pockels cell 203, and a first mirror 204 are arranged in sequence, and on the other side of the second polarization beam splitter 201, a third half-wave plate 205, a first polarization separation pulsed module 206, and a first non-linear pulsed amplification module are arranged in sequence;

[0038] The first polarization separation pulse module 206 includes 5 polarization separation modules arranged at intervals (as Figure 7 shown), each polarization separation module includes a polarization beam splitter 1, and a quarter-wave plate (2 or 4 shown in the figure) and a mirror (3 and 5 shown in the figure) are sequentially arranged on both sides of the polarization beam splitter 1; the distance between adjacent two polarization separation modules is the same, and the vertical distance between the two mirrors in the polarization separation module increases sequentially from the polarization separation module to the direction of the first nonlinear pulse amplification module; as Figure 7 shown, the distance between the two mirrors of the first polarization separation module is l = 8 mm, and the length l of each subsequent module is doubled.

[0039] The method for regenerative amplification of separated pulsed lasers in the single-channel separation pulsed laser regenerative amplification device in this embodiment includes: S1, input of signal light, injecting seed pulses in the picosecond range into the separated pulsed laser regenerative amplification module through the signal light coupling module; S2, polarization splitting and pulse separation are performed in the separated pulsed laser regenerative amplification module. When polarization splitting the pulsed laser, after the signal light is reflected by the s-polarized light through the second polarization beam splitter 201, it then passes through the first quarter-wave plate 202 and the Pockels cell 203 in sequence, and is reflected by the first mirror 204. During the reflection process, by controlling the switching time of the Pockels cell 203, the reflected s-polarized light is changed into P-polarized light after passing through the quarter-wave plate. After the P-polarized light passes through the second polarization beam splitter 201, the polarization direction of the incident P-polarized light is rotated by a set angle through the third half-wave plate 205, and the signal light is equally divided into P-polarized light and S-polarized light, achieving signal light splitting; the split polarized light is injected into the polarization separation module of the polarization sheet separation pulse module for pulse separation. When pulse separation is performed, when the polarized light passes through the 5 polarization separation modules of the polarization sheet separation pulse module, it is divided into sub-pulses with orthogonal polarization between 32 adjacent pulses and with a time delay between pulses; S3, laser amplification, the separated sub-pulses are injected into the first non-linear pulse amplification module, and are amplified twice by the pulse signal in the first non-linear pulse amplification module, and the polarization direction of the sub-pulses is rotated by 90°, and returns along the original path; S4, polarization beam combination of the amplified signal light. Specifically, the amplified sub-pulses are re-injected into the polarization sheet separation pulse module to achieve polarization beam combination and are re-combined into a single amplified pulse signal light in the S polarization state; S5, regenerative amplification of the single amplified pulse signal light. Specifically, the amplified pulse signal light is reflected by the second polarization beam splitter 201 to the third mirror 210, and then is emitted back to the second polarization beam splitter 201 by the third mirror 210, and then passes through the third half-wave plate 205 and the polarization sheet separation pulse module in sequence to achieve polarization splitting and pulse separation of the amplified pulse signal light. Then, after being amplified and reflected by the first non-linear pulse amplification module in sequence, it enters the polarization sheet separation pulse module to achieve pulse re-combination, and the polarization of the signal light changes back to p-polarization and is transmitted from the second polarization beam splitter 201 and re-injected into the Pockels cell 203 to complete one regenerative amplification cycle (a single regenerative amplification cycle includes two pulse splitting and combination and 4 times of energy amplification, greatly improving the amplification efficiency); S6, precisely control the switching time of the Pockels cell 203 to make the signal light repeat the regenerative amplification cycle steps of S2 - S5 until gain saturation, and then output the regeneratively amplified laser pulse beam through the second half-wave plate 104, the first Faraday rotator 103 to the first polarization beam splitter 102 of the signal light coupling module.

[0040] Such as Figure 7As shown, taking a single pulse separation process as an example, the signal light δ is linearly polarized, with a pulse width τ = 10 ps, and the polarization direction makes an angle of 45° with the upper surface of the polarization beam splitter. It can be decomposed into a δs component perpendicular to the interface and a δp component parallel to the interface. Only the pulse energy of the two is halved compared to δ, and other parameters remain unchanged. After δ is incident on the polarization beam splitter 1, the δs component and the δp component are reflected and transmitted by the polarization beam splitter respectively. In the reflection path, after the δs component passes through the quarter-wave plate 2 and the mirror 3, it returns along the original path. By reasonably adjusting the rotation angle of the quarter-wave plate, the δs component is remodulated into p-light, transmits through the polarization beam splitter, arrives at the quarter-wave plate 4 and the mirror 5, and is reflected again. Similarly, by adjusting the rotation angle of the quarter-wave plate 4, the δs component with p-polarization is remodulated into s-light, is reflected by the polarization beam splitter 1, and spatially coincides with the δp component that has not experienced delay, and is collinearly output. Since the δs component pulse experiences a longer optical path, it lags behind the δp component pulse in time. The lag time τdelay = 2(np - 1)dp / c + 4(nw - 1)dw / c + 2l / c = 76.6 ps.

[0041] After the δs pulse and the δp pulse after delay beam combination pass through the half-wave plate 6, their deflection angles are each rotated by 45° again, and are incident on the second polarization separation pulse module, and the sub-pulses in both directions are further split into 4. After passing through 5 polarization separation pulse modules, a pulse sequence with 32 adjacent sub-pulses being polarization orthogonal (δp component and δs component) and a pulse delay of 76.6 ps can be obtained.

[0042] Specifically, the separated pulse laser regenerative amplification module is used for the signal light injected by the signal light coupling module to pass through the reflection line of the second polarization beam splitter 201, the first quarter-wave plate 202, the Pockels cell 203, the first mirror 204, the Pockels cell 203, the first quarter-wave plate 202, the second polarization beam splitter 201, the third half-wave plate 205, the first polarization separation pulse module 206, the first non-linear pulse amplification module, the first polarization separation pulse module 206, the third half-wave plate 205, and the second polarization beam splitter 201 to realize one-time pulse splitting, two-time laser amplification and one-time pulse combination of the signal light; and after the pulse combination, the combined pulse signal light is reflected by the third mirror 210 to the second polarization beam splitter 201, and then the signal light passes through the transmission line of the third half-wave plate 205, the first polarization separation pulse module 206, the first non-linear pulse amplification module, the first polarization separation pulse module 206, the third half-wave plate 205, and the second polarization beam splitter 201 to realize the re-pulse splitting, two-time laser regenerative amplification and re-pulse combination of the signal light, and then is transmitted from the second polarization beam splitter 201 and re-injected into the Pockels cell 203 to complete one regenerative amplification cycle of the signal light (see specifically Figure 1 and Figure 9 )

[0043] The signal light coupling module is used to inject seed pulses into the separated pulse laser regenerative amplification module. When the signal light passes through the separated pulse laser regenerative amplification module and completes multiple regenerative amplification cycles until gain saturation, it is reflected by the second half-wave plate 104 and the first Faraday rotator 103 of the signal light coupling module to the first polarization beam splitter 102, and then the regeneratively amplified laser pulse beam is output.

[0044] In this embodiment, the first non-linear pulse amplification module includes a first gain crystal 207, a second Faraday rotator 208 and a second mirror 209; the second Faraday rotator 208 is located between the first gain crystal and the second mirror, and the first gain crystal is adjacent to the polarization splitting pulse module. The first gain crystal 207 is preferably a Yb:CaF2 crystal, with dimensions of 3mm×10mm×10mm, and the crystal is cut at a flat angle. The anti-reflection film in the 950 - 1100 nm band is evaporated on the light-passing surface. The ytterbium ion doping concentration is 3.at%. Under 976nm LD pumping, the 1030 nm signal light can obtain effective gain, realizing the power amplification and energy enhancement of the signal light.

[0045] The second Faraday rotator 208 can rotate the polarization angle of the incident linearly polarized light by 45°. Cooperating with the third half-wave plate 205 and the second polarization beam splitter 201, it can realize the separation and isolation of the incident light and the outgoing light. Cooperating with the mirror, it can be used as a Faraday mirror, making the polarization state of the incident laser rotate 90° and return along the original path.

[0046] In this embodiment, all lenses and optical elements operate in the 1030 nm band, with high reflection or transmission efficiency. The half-wave plate and the quarter-wave plate are both phase retardation plates in the 1030 nm band, which can realize the polarization direction modulation of linearly polarized laser. The thickness is dw = 0.5 mm, and the refractive index is nw = 1.5.

[0047] The first polarization beam splitter 102 and the second polarization beam splitter 201 are both polarization laser separation devices based on multi-layer dielectric polarization beam splitting films, which reflect s-polarized light and transmit p-polarized light. The polarization extinction ratio > 2000:1. Its shape is a cube structure, with a thickness dp = 5 mm and a refractive index np = 1.6.

[0048] The first mirror, the second mirror and the third mirror are mirrors operating in the 1000 - 1100 nm band, with a working angle of 0° and a reflectivity > 99.5%. The three mirrors form a stable regenerative resonator. The first mirror, the second mirror and the third mirror set in this embodiment do not refer to a single type of lens, and can be a combination of multiple plano-concave or plane mirrors, forming a regenerative standing wave cavity with low loss.

[0049] The Pockels cell 203 in this embodiment is a quarter-wave fast electro-optic device, which acts as a quarter-wave plate under high voltage (>2 kV). The rise and fall times of the response time (high-voltage signal) of the Pockels cell are both <10 ns.

[0050] The first quarter-wave plate 202 is a phase retardation plate in the 1030 nm band, which provides a quarter-wave phase retardation for the orthogonal polarization components. When used in conjunction with the Pockels cell, it can achieve fast electro-optic modulation of the seed light and the regeneratively amplified output light, realizing laser input and output.

[0051] By controlling the switching time of the Pockels cell, after dozens of regenerative amplification cycles, a signal light pulse in the order of 10 ps can be amplified to the millijoule level, and the gain narrowing effect during the regenerative amplification process can be effectively suppressed. The system does not require a traditional dispersion broadening medium, greatly reducing the volume of the system and providing an effective alternative to chirped pulse amplification technology.

[0052] Expanding the regenerative amplification optical path in the separated pulse laser regenerative amplification module can effectively solve the limitation of gain narrowing in regenerative amplification and achieve a higher peak power pulse output. This embodiment addresses the problems of nonlinear accumulation, spectral gain narrowing, and pulse compression in high-field ultrafast laser amplification, replacing the traditional chirped pulse solid regenerative amplification technology and no longer relying on expensive dispersion delay media to achieve pulse broadening.

[0053] Embodiment 2:

[0054] This embodiment provides a separated pulse laser regenerative amplification device with a nonlinear amplifying loop mirror, as shown in the appendix Figure 2It includes a signal light coupling module and a separated pulse laser regeneration and amplification module. Among them, the signal light coupling module is the same as that in Embodiment 1; the separated pulse laser regeneration and amplification module includes a second polarization beam splitter 201 and a third reflector 210. The second polarization beam splitter 201 is adjacent to the second half-wave plate 104 and is in the same column as the third reflector 210 and the second half-wave plate 104. On one side of the second polarization beam splitter 201, a first quarter-wave plate 202, a Pockels cell 203, and a first reflector 204 are sequentially arranged. On the other side of the second polarization beam splitter 201, a third half-wave plate 205, a first polarization sheet separated pulse module 206, and a first non-linear pulse amplification module are sequentially arranged. In this embodiment, the first non-linear pulse amplification module includes a third polarization beam splitter 214, a first gain crystal 208, a second reflector 209, a fourth reflector 211, a fourth half-wave plate 212, and a fifth reflector 213 (the above components constitute the non-linear amplification ring mirror in this embodiment, replacing the first gain crystal in Embodiment 1. The non-linear amplification ring mirror can also amplify the signal light after pulse separation, and the polarization state rotates by 90°, and then returns to the first polarization sheet separated pulse module to realize pulse beam combination); the third polarization beam splitter 214, the fifth reflector 213, and the first polarization sheet separated pulse module 206 are on the same straight line, and the third polarization beam splitter 214 is located between the fifth reflector 213 and the first polarization sheet separated pulse module; the beam emission line formed by the third polarization beam splitter 214, the first gain crystal, and the second reflector is perpendicular to the beam emission line formed by the third polarization beam splitter 214 and the fifth reflector, and the first gain crystal is located between the third polarization beam splitter 214 and the second reflector; the fourth reflector is on one side of the second reflector, and the beam emission line formed by the fourth reflector, the fourth half-wave plate, and the fifth reflector is parallel to the beam emission line formed by the third polarization beam splitter 214, the first gain crystal, and the second reflector.

[0055] The first gain crystal, the third polarization beam splitter 214, and the fourth half-wave plate in this embodiment have the same device parameters as the related devices in Embodiment 1. The second reflector, the fourth reflector, and the fifth reflector are plane high-reflection mirrors in the 1030 nm band, with a reflectivity > 99.5% and an incident angle of 45°.

[0056] The first polarization sheet separated pulse module 206 in this embodiment has the same structure as that in Embodiment 1. The signal light after pulse separation is also divided into 32 sub-pulse sequences. The polarization between adjacent two sub-pulses is orthogonal, denoted as δp and δs components, and the delay is τdelay.

[0057] After the δp and δs components after pulse separation are incident on the third polarization beam splitter 214, the δp component is transmitted and the δs component is reflected. The transmitted light is reflected by the fifth mirror 213, and its polarization direction is converted to s polarization by rotating the fourth half-wave plate 212. Then, it passes through the fourth mirror 211 and the second mirror 209 and is injected into the first gain crystal 208 to achieve energy enhancement. Finally, it is reflected by the third polarization beam splitter 214. Conversely, the δs component is first reflected by the third polarization beam splitter 214, then directly injected into the first gain crystal 208 to achieve energy enhancement, then reflected by the second mirror 209 and the fourth mirror 211, modulated into p light by the fourth half-wave plate 212, and then reflected by the fifth mirror 213 and transmitted out of the third polarization beam splitter 214. It can be seen that after the δp and δs after pulse separation are amplified and reflected by the nonlinear amplifying loop mirror, their respective polarization directions are rotated by 90° and then return to the first polarizer separation pulse module 206 to achieve pulse combining. And further realize the separation pulse regeneration amplification cycle to obtain an energy enhancement of 60 dB.

[0058] Embodiment 3:

[0059] This embodiment provides another separation pulse laser regeneration amplification device of a nonlinear amplifying loop mirror. Compared with Embodiment 2, the difference lies only in the first nonlinear pulse amplification module. In this embodiment, the third Faraday rotator 215 is used to replace the fourth half-wave plate 212 in Embodiment 2 to form a separation pulse regeneration amplification device of a nonlinear amplifying loop mirror.

[0060] The third Faraday rotator 215 inserted in the first nonlinear amplifying loop mirror has a polarization rotation angle of 90°, which is different from the first Faraday rotator 103 in Embodiment 1 of the present invention.

[0061] Embodiment 4:

[0062] As Figure 4As shown in the figure, this embodiment provides a dispersion compensation non-linear amplification loop mirror separated pulse laser regeneration amplification device. Compared with Embodiment 3, the main difference of the regeneration amplification device in this embodiment lies in the first non-linear pulse amplification module. Specifically, the first non-linear pulse amplification module in this embodiment includes a third polarization beam splitter 214, a first gain crystal 208, a second mirror 209, two pairs of reflective diffraction gratings 216, a fourth mirror 211, a third Faraday rotator 215, and a fifth mirror 213; the third polarization beam splitter 214, the fifth mirror 213, and the first polarizer separation pulse module are on the same straight line, and the third polarization beam splitter 214 is located between the fifth mirror 213 and the first polarizer separation pulse module; the beam emission lines formed by the third polarization beam splitter 214, the first gain crystal 208, and the second mirror 209 are perpendicular to the beam emission lines formed by the third polarization beam splitter 214 and the fifth mirror 213, and the first gain crystal is located between the third polarization beam splitter 214 and the second mirror; the two pairs of reflective diffraction gratings 216 are located between the second mirror 209 and the fourth mirror 211, and the beam emission lines formed by the fourth mirror 211, the third Faraday rotator, and the fifth mirror are parallel to the beam emission lines formed by the third polarization beam splitter 214, the first gain crystal, and the second mirror.

[0063] In this embodiment, two pairs of reflective diffraction gratings are inserted into the non-linear amplification loop mirror to perform dispersion compensation on the signal light after pulse separation. Combining with the regeneration amplification process, the gain narrowing effect in the high-energy pulse amplification process can be effectively suppressed.

[0064] The typical characteristics of the two pairs of reflective diffraction gratings are that the working wavelength range is 1030 nm, the grating groove period is 1250 l / mm, the grating diffraction efficiency > 90%, and the Littrow angle is 42°. The arrangement of the gratings is as shown in the appendix. Figure 4 The grating spacing can be adjusted according to the actual situation.

[0065] Embodiment 5:

[0066] As Figure 5As shown in the figure, this embodiment provides a dual-channel and same-crystal separated pulse laser regenerative amplification device, including a signal light coupling module and a separated pulse laser regenerative amplification module; the signal light coupling module is the same as that in Embodiment 1. Compared with Embodiment 1, an additional separated pulse laser regenerative amplification module is added in this embodiment. That is, the separated pulse laser regenerative amplification module in this embodiment includes a first-channel separated pulse laser regenerative amplification module and a second-channel separated pulse laser regenerative amplification module. Among them, the first-channel separated pulse laser regenerative amplification module includes a second polarization beam splitter 201, a first quarter-wave plate 202, a Pockels cell 203, a first mirror 204, a third half-wave plate 205, a first polarization separation pulse module 206, and a first non-linear pulse amplification module; the installation positions of the above components are the same as those in Embodiment 1, and will not be described here. The second-channel separated pulse laser regenerative amplification module includes a sixth mirror 217, a fourth polarization beam splitter 218, a fifth half-wave plate 219, a second polarization separation pulse module 220, a second gain crystal 221, a fourth Faraday rotator 222, and a seventh mirror 223 arranged in sequence; the fourth polarization beam splitter 218 corresponds to the second polarization beam splitter 201 and is in the same column; the sixth mirror 217 and the first mirror 204 are on the same side, and the fifth half-wave plate 219 and the sixth mirror 217 are respectively on two opposite sides of the fourth polarization beam splitter 218.

[0067] The first gain crystal 207 and the second gain crystal 221 in this embodiment are two completely identical crystals. After adding an additional separated pulse laser regenerative amplification module in this embodiment, it helps to improve the pulse energy and suppress the gain narrowing.

[0068] The optical path evolution process of this embodiment is as follows: After the seed pulse is injected into the separated pulse laser regenerative amplifier module through the signal light coupling module, the signal light sequentially undergoes pulse separation, laser amplification, and re-combination in S2 - S4 in Embodiment 1, and then is reflected by the second polarization beam splitter to the fourth polarization beam splitter of the second regenerative amplifier module; after the combined signal light is reflected to the fourth polarization beam splitter, it is reflected to the fifth half-wave plate and then enters the third polarization beam separation pulse module and the second non-linear pulse amplification module in sequence, realizing pulse separation and laser amplification of the polarized light after combination, and the polarization direction of the sub-pulse rotates by 90°. After passing through the second non-linear pulse amplification module and the third polarization beam separation pulse module again to realize laser amplification and pulse combination, it projects out from the fourth polarization beam splitter, is reflected by the sixth mirror, and then passes through the fourth polarization beam splitter again, and enters the fifth half-wave plate, the third polarization beam separation pulse module, and the second non-linear pulse amplification module in sequence to realize pulse separation, amplification, reflection, and re-amplification, and then enters the third polarization beam separation pulse module to realize pulse combination, and is reflected back to the second polarization beam splitter through the fourth polarization beam splitter, and undergoes pulse separation, laser amplification, and re-combination in S2 - S4 again, and then transmits out from the second polarization beam splitter and returns to the Pockels cell to complete one regenerative amplification cycle. A single regenerative amplification cycle includes four pulse beam splittings and combinations and 8 times of energy amplification, greatly improving the amplification efficiency.

[0069] After completing one regenerative amplification cycle, precisely control the switching time of the Pockels cell, so that the signal light repeats the pulse separation, laser amplification, and re-combination in S2 - S4 in Embodiment 1, and then repeats the above steps until gain saturation. After that, it is reflected by the second half-wave plate, the first Faraday rotator of the signal light coupling module to the first polarization beam splitter, and then outputs the regeneratively amplified laser pulse beam.

[0070] Embodiment 6:

[0071] As Figure 6 shown, this embodiment provides a separated pulse laser regenerative amplifier device with two different crystals. The optical path structure of the device in this embodiment is basically the same as that in Embodiment 5, except that the first gain crystal 207 and the second gain crystal 221 in this embodiment are two different types of gain crystals, or two crystals with different cutting directions or placement angles. The differences in crystal type, cutting direction, or placement angle result in a certain complementarity in their radiation spectral bands, thereby effectively suppressing the gain narrowing effect during the regenerative amplification process.

[0072] Specifically, in this embodiment, the first gain crystal and the second gain crystal are gain crystals of the same type but different cutting directions. The first gain crystal 207 is a Yb:CaF2 crystal, and the second gain crystal 221 is a Yb:CALGO crystal. The central band of the radiation spectrum of the Yb:CaF2 crystal is located at 1030 nm, and the central band of the radiation spectrum of the Yb:CALGO crystal is located at 1040 nm. The two have a certain complementarity, which broadens the overall radiation spectrum of the regenerative amplifier and can effectively suppress gain narrowing during the amplification process.

[0073] When the first gain crystal and the second gain crystal are selected as gain crystals of the same type but different placement angles, the gain crystal is an Np-cut Yb:KGW crystal (see appendix Figure 8 ). For the three mutually orthogonal axes of the Yb:KGW crystal, Np, Nm, and Ng, the Ng direction is the incident direction of the signal light. For the first gain crystal 207, the Np direction is parallel to the p-polarized signal light direction, and the Nm direction is parallel to the s-polarized signal light direction. For the second gain crystal 221, the p direction is parallel to the s-polarized signal light direction, and the Nm direction is parallel to the p-polarized signal light direction.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those of ordinary skill in the art should understand that any modifications or equivalent replacements of the technical solutions of the present invention without departing from the purpose and scope of the present technical solution shall be covered by the scope of the claims of the present invention.

Claims

1. A separated pulsed laser regenerative amplification device, comprising a signal light coupling module and a separated pulsed laser regenerative amplification module; Characterized in that, The signal light coupling module includes a first half-wave plate, a first polarization beam splitter, a first Faraday rotator and a second half-wave plate arranged in sequence; The separated pulsed laser regenerative amplification module includes a second polarization beam splitter and a third reflector. The second polarization beam splitter is adjacent to the second half-wave plate and is in the same column as the third reflector and the second half-wave plate. On one side of the second polarization beam splitter, a first quarter-wave plate, a Pockels cell and a first reflector are arranged in sequence. On the other side of the second polarization beam splitter, a third half-wave plate, a first polarization separation pulse module and a first non-linear pulse amplification module are arranged in sequence. The first non-linear pulse amplification module includes a first gain crystal, a second Faraday rotator and a second reflector. The first non-linear pulse amplification module includes a third polarization beam splitter, a first gain crystal and a second reflector. The second Faraday rotator is located between the first gain crystal and the second reflector, and the first gain crystal is adjacent to the polarization separation pulse module; The first polarization separation pulse module includes m polarization separation modules arranged at intervals, where m≥2. Each polarization separation module includes a polarization beam splitter. On both sides of the polarization beam splitter, a quarter-wave plate and a reflector are arranged in sequence. The distance between adjacent two polarization separation modules is the same, and the vertical distance between the two reflectors in the polarization separation module increases sequentially from the polarization separation module to the direction of the first non-linear pulse amplification module; The separated pulsed laser regenerative amplification module is used to perform a reflection circuit of the signal light injected by the signal light coupling module through the second polarization beam splitter, the first quarter-wave plate, the Pockels cell, the first reflector, the Pockels cell, the first quarter-wave plate, the second polarization beam splitter, the third half-wave plate, the first polarization separation pulse module, the first non-linear pulse amplification module, the first polarization separation pulse module, the third half-wave plate and the second polarization beam splitter, to achieve one-time pulse splitting of the signal light, two-time laser amplification and one-time pulse combining; And after the pulse combining, the combined pulsed signal light is reflected by the third reflector to the second polarization beam splitter, and then the signal light passes through the third half-wave plate, the first polarization separation pulse module, the first non-linear pulse amplification module, the first polarization separation pulse module, the third half-wave plate and the second polarization beam splitter through the transmission circuit, to achieve secondary pulse splitting of the signal light, two-time laser regenerative amplification and secondary pulse combining, and then is transmitted from the second polarization beam splitter and re-injected into the Pockels cell to complete one regenerative amplification cycle of the signal light; The signal light coupling module is used to inject the seed pulse into the separated pulsed laser regenerative amplification module, and when the signal light passes through the separated pulsed laser regenerative amplification module and completes multiple regenerative amplification cycles until the gain saturation, after passing through the second half-wave plate, the first Faraday rotator and being reflected by the first polarization beam splitter of the signal light coupling module, the regenerated and amplified laser pulse beam is output.

2. The separated pulsed laser regenerative amplification device according to claim 1, Characterized in that, The first non-linear pulse amplification module further includes a fourth reflector, a fourth half-wave plate, and a fifth reflector; the third polarization beam splitter, the fifth reflector, and the first polarization separation pulse module are on the same straight line, and the third polarization beam splitter is located between the fifth reflector and the first polarization separation pulse module; the light beam emission line formed by the third polarization beam splitter, the first gain crystal, and the second reflector is perpendicular to the light beam emission line formed by the third polarization beam splitter and the fifth reflector, and the first gain crystal is located between the third polarization beam splitter and the second reflector; the fourth reflector is located on one side of the second reflector, and the light beam emission line formed by the fourth reflector, the fourth half-wave plate, and the fifth reflector is parallel to the light beam emission line formed by the third polarization beam splitter, the first gain crystal, and the second reflector.

3. The separated pulse laser regeneration amplification device according to claim 2, wherein, the fourth half-wave plate can be replaced by a third Faraday rotator.

4. The separated pulse laser regeneration amplification device according to claim 1, wherein, the first non-linear pulse amplification module includes a third polarization beam splitter, a first gain crystal, a second reflector, two pairs of reflective diffraction gratings, a fourth reflector, a third Faraday rotator, and a fifth reflector; the third polarization beam splitter, the fifth reflector, and the first polarization separation pulse module are on the same straight line, and the third polarization beam splitter is located between the fifth reflector and the first polarization separation pulse module; the light beam emission line formed by the third polarization beam splitter, the first gain crystal, and the second reflector is perpendicular to the light beam emission line formed by the third polarization beam splitter and the fifth reflector, and the first gain crystal is located between the third polarization beam splitter and the second reflector; the two pairs of reflective diffraction gratings are located between the second reflector and the fourth reflector, and the light beam emission line formed by the fourth reflector, the third Faraday rotator, and the fifth reflector is parallel to the light beam emission line formed by the third polarization beam splitter, the first gain crystal, and the second reflector.

5. The separated pulse laser regeneration amplification device according to claim 1 or 2 or 3 or 4, wherein, the third reflector can be replaced by a second regeneration amplification module, and the second regeneration amplification module includes a sixth reflector, a fourth polarization beam splitter, a fifth half-wave plate, a second polarization separation pulse module, and a second non-linear pulse amplification module arranged in sequence; the fourth polarization beam splitter corresponds to the second polarization beam splitter and is located in the same column; the sixth reflector and the first reflector are on the same side, and the fifth half-wave plate and the sixth reflector are respectively located on two opposite sides of the fourth polarization beam splitter.

6. The separated pulse laser regeneration amplification device according to claim 5, wherein, the second non-linear pulse amplification module includes a second gain crystal, a fourth Faraday rotator, and a seventh reflector arranged in sequence.

7. The separated pulse laser regeneration amplification device according to claim 6, wherein, the first gain crystal and the second gain crystal are laser crystals doped with ytterbium or neodymium ions.

8. A method for separated pulse laser regeneration amplification, wherein, it includes: S1. Signal light input: Inject seed pulses in the picosecond (ps) level into the separated pulse laser regeneration and amplification module through the signal light coupling module. The separation pulsed laser regeneration amplification module is as described in any one of claims 1-5; S2, polarizing beam splitting and pulse separation are performed on the injection into the separation pulsed laser regeneration amplification module. When polarizing beam splitting the pulsed laser, the signal light first reflects the s-polarized light through the second polarizing beam splitter, and then sequentially passes through the first quarter-wave plate and the Pockels cell and is reflected by the first reflector. During the reflection process, by controlling the switching time of the Pockels cell, the reflected s-polarized light becomes P-polarized light after passing through the quarter-wave plate. After this P-polarized light passes through the second polarizing beam splitter, the polarization direction of the incident P-polarized light is rotated by a set angle through the third half-wave plate, and the signal light is equally divided into P-polarized light and S-polarized light, realizing signal light beam splitting; the split polarized light is injected into the polarization separation module of the polarization splitting pulsed module for pulse separation. When performing pulse separation, when the polarized light passes through the m polarization separation modules of the polarization splitting pulsed module, it is divided into 2 m sub-pulses with orthogonal polarization between two adjacent pulses and with a time delay between pulses; S3, laser amplification. The separated sub-pulses are injected into the first non-linear pulse amplification module, and after two pulse signal amplifications in the first non-linear pulse amplification module, and the polarization direction of the sub-pulses is rotated by 90°, and they return along the original path; S4, polarization beam combination of the amplified signal light. Specifically, the amplified sub-pulses are reinjected into the polarization splitting pulsed module to realize polarization beam combination and are recombined into a single amplified pulsed signal light in the S polarization state; S5, regeneration amplification of the single amplified pulsed signal light. Specifically, the amplified pulsed signal light is reflected by the second polarizing beam splitter to the third reflector, and then after being reflected back to the second polarizing beam splitter by the third reflector, it sequentially passes through the third half-wave plate and the polarization splitting pulsed module to realize polarization beam splitting and pulse separation of the amplified pulsed signal light. Then, after being amplified and reflected by the first non-linear pulse amplification module in sequence, it enters the polarization splitting pulsed module to realize pulse recombination again, and the signal light polarization returns to p-polarization again, and is transmitted from the second polarizing beam splitter and reinjected into the Pockels cell to complete a regeneration amplification cycle; S6, precisely control the switching time of the Pockels cell, so that the signal light repeats the regeneration amplification cycle steps of S2-S5. Until saturation gain, after passing through the second half-wave plate and the first Faraday rotator of the signal light coupling module and being reflected by the first polarizing beam splitter, the regenerated and amplified laser pulsed beam is output.

9. The separated pulse laser regeneration and amplification method according to claim 8, characterized in that the third reflector can be replaced by the second regeneration and amplification module as described in claim 6; after the seed pulse is injected into the separated pulse laser regeneration and amplification module through the signal light coupling module, the signal light is sequentially subjected to pulse separation, laser amplification, and recombination in S2 - S4, and then is reflected by the second polarization beam splitter to the fourth polarization beam splitter of the second regeneration and amplification module; after the combined signal light is reflected to the fourth polarization beam splitter, it is reflected to the fifth half-wave plate and then enters the third polarization separation pulse module and the second non-linear pulse amplification module in sequence to achieve pulse separation and laser amplification of the combined polarized light, and the polarization direction of the sub-pulses rotates by 90°. After passing through the second non-linear pulse amplification module and the third polarization separation pulse module again to achieve laser amplification and pulse recombination, it projects out from the fourth polarization beam splitter, is reflected by the sixth reflector, and then passes through the fourth polarization beam splitter again, and enters the fifth half-wave plate, the third polarization separation pulse module, and the second non-linear pulse amplification module in sequence to achieve pulse separation, amplification, reflection, and re-amplification, and then enters the third polarization separation pulse module to achieve pulse recombination, and then is reflected back to the second polarization beam splitter through the fourth polarization beam splitter, and undergoes pulse separation, laser amplification, and recombination in S2 - S4 again, and then transmits out from the second polarization beam splitter, returns to the Pockels cell, and completes one regeneration and amplification cycle.

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