Disk medium high-energy ultra-short pulse laser regenerative amplifier based on CPA technology

Abstract

The application discloses a disk medium high-energy ultra-short pulse laser regenerative amplifier based on CPA technology, comprising: a femtosecond laser seed light source for providing femtosecond seed light; a chirped Bragg fiber grating for expanding the femtosecond seed light into nanosecond laser pulses; an optical coupling input and output device for coupling input of the nanosecond laser pulses and coupling output of the nanosecond laser pulses after amplification processing; a regenerative amplification laser cavity for regenerative amplification processing of the coupled-in nanosecond laser pulses; the optical coupling input and output device comprises a fiber coupling collimation module, an optical isolator, a first 1 / 2 wave plate and a thin film polarizer; the regenerative amplification laser cavity comprises a Pockels cell, a second 1 / 2 wave plate, a first reflection module, a second reflection module, a first telescope module, a second telescope module, a first disk gain medium, a second disk gain medium and a third reflection module; the regenerative amplifier can realize high-repetition-frequency and high-pulse-energy laser pulse output.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical technology, in particular to a disk medium high-energy ultra-short pulse laser regenerative amplifier based on CPA technology. BACKGROUND

[0002] At present, the rapid development of the solution of heat management and dispersion management of ultrafast laser enables novel system design to provide high average and peak power and pulse energy. Some laser systems can expand the pulse energy to tens or even hundreds of millijoules. In general, there are mainly the following implementation manners:

[0003] Plate laser, which generates sub-picosecond pulses with average power exceeding 1kW at a repetition frequency of tens of MHz, can generate 20mJ pulse energy at 12.5kHz. However, due to the strong asymmetric thermal lens effect, the average power is often at the expense of beam quality deterioration.

[0004] Fiber laser, which provides very good beam quality (M2<1.2) at an output energy in the range of mJ at a repetition frequency of 100kHz. A coherent combination of multiple amplifier channels allows the expansion of the technology by using eight channels to expand the pulse energy to tens of millijoules.

[0005] Ultra-low temperature cooling of the laser working substance can achieve tens of mJ pulse energy at a repetition frequency of kilohertz, but needs to be at the expense of greatly reducing the gain bandwidth. And, the current mainstream technologies have technical limitations or system defects such as too complex in realizing hundreds of millijoule ultra-short laser pulses. SUMMARY

[0006] The embodiment of the present application provides a disk medium high-energy ultra-short pulse laser regenerative amplifier based on CPA technology, which aims to realize high repetition frequency / high pulse energy at room temperature based on disk gain laser system.

[0007] The embodiment of the present application provides a disk medium high-energy ultra-short pulse laser regenerative amplifier based on CPA technology, which comprises:

[0008] A femtosecond laser seed light source is used to provide femtosecond seed light;

[0009] A chirped Bragg fiber grating is used to expand the femtosecond seed light into nanosecond laser pulses;

[0010] An optical coupling input and output device is used to couple the nanosecond laser pulses and the amplified nanosecond laser pulses;

[0011] A regenerative amplification laser cavity is used to regenerate and amplify the coupled nanosecond laser pulses.

[0012] The light coupling input and output device comprises a fiber coupling collimation module, an optical isolator, a first 1 / 2 wave plate and a thin film polarizer;

[0013] The regenerative amplification laser cavity comprises a Pockels cell, a second 1 / 2 wave plate, a first reflection module, a second reflection module, a first telescope module, a second telescope module, a first disk gain medium, a second disk gain medium and a third reflection module; wherein the first telescope module, the first disk gain medium and the second telescope module, the second disk gain medium are symmetrically distributed about the second reflection module;

[0014] The femtosecond seed light is pulse broadened into nanosecond laser pulse by the chirped Bragg fiber grating to avoid device damage of the femtosecond seed light in the amplification process, the nanosecond laser pulse is converted into linear p-polarization by the fiber coupling collimation module, the optical isolator and the first 1 / 2 wave plate in the light coupling input and output device in turn, and then passes through the thin film polarizer to enter the regenerative amplification laser cavity;

[0015] The nanosecond laser pulse is converted into s-polarization by the Pockels cell and the second 1 / 2 wave plate without voltage, and then enters the first disk gain medium after passing through the first reflection module; the s-polarized femtosecond seed light extracts energy in the first disk gain medium, and then enters the second disk gain medium after passing through the first telescope module, the second reflection module and the second telescope module in turn;

[0016] The nanosecond laser pulse extracts energy in the second disk gain medium, and then returns to the Pockels cell with voltage after passing through the third reflection module and the thin film polarizer in turn, and keeps s-polarization in the regenerative amplification laser cavity to reciprocate back and forth to extract energy in the first disk gain medium and the second disk gain medium for multiple times until the energy gain of the nanosecond laser pulse is saturated, and then the amplified nanosecond laser pulse is output through the light coupling input and output device.

[0017] Further, an adjustable pulse compressor for pulse width compression of the amplified nanosecond laser pulse is further included, the second order dispersion and the third order dispersion provided by the adjustable pulse compressor correspond to the second order dispersion and the third order dispersion required for the femtosecond broadening to nanosecond provided by the chirped Bragg fiber grating respectively.

[0018] Further, the adjustable pulse compressor comprises a first grating, a second grating, a first mirror group, a second mirror group, a third mirror group and a fourth mirror group; wherein the first grating and the second grating are arranged in parallel, and the first mirror group and the third mirror group are arranged on a movable platform;

[0019] The amplified nanosecond laser pulse diffracts through the first grating, sequentially passes through the first mirror set, the second mirror set, the third mirror set, the second mirror set and the first mirror set, diffracts through the second grating, is reflected through the fourth mirror set to realize optical axis lifting, then returns to the second grating, and is output from the first grating as compressed light after passing through the first mirror set, the second mirror set, the third mirror set, the second mirror set and the first mirror set again.

[0020] Further, the pump source is used for simultaneously pumping the first disc-shaped gain medium and the second disc-shaped gain medium.

[0021] Further, the pump source splits the pump beam into a first pump beam and a second pump beam through a beam splitter, the first pump beam directly irradiates into the first disc-shaped gain medium, and the second pump beam is reflected into the second disc-shaped gain medium through a fourth reflection module.

[0022] Further, the first reflection module sequentially includes a first 0° mirror and a second 0° mirror which are parallel in the vertical direction and not on the same horizontal line along the optical path.

[0023] The second reflection module includes a third 0° mirror which is parallel to the second 0° mirror in the vertical direction.

[0024] The third reflection module includes a first 45° mirror which is arranged in a forward direction.

[0025] The fourth reflection module includes a second 45° mirror which is arranged in a reverse direction.

[0026] Further, the first telescopic module sequentially includes a first concave mirror and a first convex mirror along the optical path, and the second telescopic module sequentially includes a second convex mirror and a second concave mirror along the optical path, wherein the curvature parameters of the first concave mirror and the second concave mirror are the same, and the curvature parameters of the first convex mirror and the second convex mirror are the same.

[0027] Further, the compression range of the adjustable pulse compressor is 1.6-10 picoseconds.

[0028] Further, two electro-optic crystals are arranged in the Pockels cell to make the phase modulation of the Pockels cell λ / 2, both the electro-optic crystals are barium metaborate crystals, and the clear aperture of the Pockels cell is 80%-90% of the length of the barium metaborate crystal.

[0029] The left and right sides of the barium metaborate crystal are plated with gold or chromium, and the upper and lower ends are plated with 1030nm anti-reflection film.

[0030] Further, the first disk gain medium and the second disk gain medium have the same structure, the first disk gain medium has a disk structure, and the disk structure has a diameter of 12-30 mm, a thickness of 0.100-0.250 mm, and a crystal wedge angle of 0-0.05°;

[0031] The first disk gain medium is YAG crystal doped with Yb with a mass concentration of 0.3%-10%.

[0032] After polishing the YAG crystal, a 940-969 nm and 1030 nm antireflection film is coated on the upper surface, a 940-969 nm and 1030 nm reflection film is coated on the rear surface, and the rear surface of the Yb:YAG crystal is directly welded, bonded and / or glued to the heat sink material.

[0033] Alternatively, the first disk gain medium is CALGO, KYW, KGW, KLW, Lu2O3, Sc2O3 or YVO4 crystal doped with any of Nd 3+ , Ho or Tm 3+ .

[0034] The embodiment of the present application provides a disk medium high-energy ultra-short pulse laser regenerative amplifier based on CPA technology, a femtosecond laser seed light source for providing femtosecond seed light; a chirped Bragg fiber grating for expanding the femtosecond seed light into nanosecond laser pulses; an optical coupling input and output device for coupling input of the nanosecond laser pulses and coupling output of the nanosecond laser pulses after amplification processing; a regenerative amplification laser cavity for regenerative amplification processing of the coupled-in nanosecond laser pulses; the optical coupling input and output device comprises a fiber coupling collimation module, an optical isolator, a first 1 / 2 wave plate and a thin film polarizer; the regenerative amplification laser cavity comprises a Pockels cell, a second 1 / 2 wave plate, a first reflection module, a second reflection module, a first telescope module, a second telescope module, a first disk gain medium, a second disk gain medium and a third reflection module; wherein the first telescope module, the first disk gain medium and the second telescope module, the second disk gain medium are symmetrically distributed about the second reflection module; the femtosecond seed light is expanded into nanosecond laser pulses through the chirped Bragg fiber grating to avoid device damage of the femtosecond seed light in the amplification process, the nanosecond laser pulses pass through the fiber coupling collimation module, the optical isolator and the first 1 / 2 wave plate in the optical coupling input and output device in sequence, are converted into linear p-polarization, and pass through the thin film polarizer to enter the regenerative amplification laser cavity; the nanosecond laser pulses are converted from linear p-polarization into s-polarization after passing through the Pockels cell and the second 1 / 2 wave plate without voltage, and enter the first disk gain medium after passing through the first reflection module; the s-polarized femtosecond seed light extracts energy in the first disk gain medium, passes through the first telescope module, the second reflection module and the second telescope module in sequence, and extracts energy in the second disk gain medium; the nanosecond laser pulses extract energy in the second disk gain medium, pass through the third reflection module and the thin film polarizer in sequence, return to the Pockels cell with voltage, and keep s-polarization in the regenerative amplification laser cavity to reciprocally oscillate to extract energy in the first disk gain medium and the second disk gain medium for multiple times until the energy gain of the nanosecond laser pulses is saturated, and then the amplified nanosecond laser pulses are output through the optical coupling input and output device. The laser system based on the disk gain in the embodiment of the present application realizes high repetition rate / high pulse energy at normal temperature, the pulse energy can reach 200 millijoules, the pulse width is 1.6-10 picoseconds, and the laser pulse output has excellent beam quality, and the system is greatly simplified. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0036] Figure 1 A system structure diagram of a disc medium high-energy ultra-short pulse laser regenerative amplifier based on CPA technology is provided for the embodiment of the present application;

[0037] Figure 2 An optical path schematic diagram of an adjustable pulse compressor in a disc medium high-energy ultra-short pulse laser regenerative amplifier based on CPA technology is provided for the embodiment of the present application;

[0038] Figure 3 A sub-optical path schematic diagram of an adjustable pulse compressor in a disc medium high-energy ultra-short pulse laser regenerative amplifier based on CPA technology is provided for the embodiment of the present application;

[0039] Figure 4 Another sub-optical path schematic diagram of an adjustable pulse compressor in a disc medium high-energy ultra-short pulse laser regenerative amplifier based on CPA technology is provided for the embodiment of the present application;

[0040] Figure 5 A laser mode distribution schematic diagram of a regenerative amplification laser cavity in a disc medium high-energy ultra-short pulse laser regenerative amplifier based on CPA technology is provided for the embodiment of the present application. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0042] It should be understood that, when used in the specification and the appended claims, the terms “comprise” and “include” indicate the presence of described features, integers, steps, operations, elements, and / or components, but do not exclude one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0043] It should also be understood that the terms used in the present application specification are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the present application specification and the appended claims, the singular forms “a”, “an” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0044] It should be further understood that the term "and / or" as used in the specification and in the claims, if any, is intended to mean an addition of one or more of the listed items to another, and is intended to cover all possible combinations of the items.

[0045] Please see below Figure 1 The CPA technology-based disk medium high-energy ultra-short pulse laser regenerative amplifier provided by the embodiment of the application comprises:

[0046] The femtosecond laser seed light source 1 is used to provide femtosecond seed light;

[0047] The chirped Bragg fiber grating 2 is used to expand the femtosecond seed light into nanosecond laser pulses;

[0048] The optical coupling input and output device is used to couple in the nanosecond laser pulses and couple out the nanosecond laser pulses after amplification processing;

[0049] The regenerative amplification laser cavity is used to perform regenerative amplification processing on the coupled-in nanosecond laser pulses;

[0050] The optical coupling input and output device comprises a fiber coupling collimation module, an optical isolator 3, a first 1 / 2 wave plate 4 and a thin film polarizer 5;

[0051] The regenerative amplification laser cavity comprises a Pockels cell 6, a second 1 / 2 wave plate 7, a first reflection module, a second reflection module, a first telescope module, a second telescope module, a first disk gain medium 8, a second disk gain medium 9 and a third reflection module; wherein the first telescope module, the first disk gain medium and the second telescope module, the second disk gain medium are symmetrically distributed about the second reflection module;

[0052] The femtosecond seed light is expanded into nanosecond laser pulses by the chirped Bragg fiber grating 2 to avoid device damage of the femtosecond seed light in the amplification process, the nanosecond laser pulses are sequentially subjected to the fiber coupling collimation module, the optical isolator 3 and the first 1 / 2 wave plate 4 in the optical coupling input and output device, are converted into linear p-polarization, and pass through the thin film polarizer 5 to enter the regenerative amplification laser cavity;

[0053] After passing through the Pockels cell 6 and the second 1 / 2 wave plate 7 without voltage, the nanosecond laser pulses are converted from linear p-polarization into s-polarization, and enter the first disk gain medium 8 after passing through the first reflection module; the s-polarized nanosecond laser pulses extract energy in the first disk gain medium 8 and sequentially pass through the first telescope module, the second reflection module and the second telescope module to extract energy in the second disk gain medium 9;

[0054] After the nanosecond laser pulse extracts energy in the second disk gain medium 9, it returns to the Pockels cell 6 with voltage in turn after passing through the third reflection module and the film polarizer, and keeps the s polarization reciprocating in the regenerative amplification laser cavity, so as to extract energy in the first disk gain medium 8 and the second disk gain medium 9 for multiple times, until the energy gain of the nanosecond laser pulse is saturated, and then the amplified nanosecond laser pulse is output through the optical coupling input and output device.

[0055] The embodiment provides a disk medium high-energy ultra-short pulse laser regenerative amplifier based on CPA technology, mainly comprising a femtosecond laser seed light source 1, a chirped Bragg fiber grating 2, an optical coupling input and output device and a regenerative amplification laser cavity, wherein the optical coupling input and output device comprises a fiber coupling collimation module, an optical isolator 3, a first 1 / 2 wave plate 4 and a film polarizer 5, and the regenerative amplification laser cavity comprises a Pockels cell 6, a second 1 / 2 wave plate 7, a first reflection module, a second reflection module, a first telescope module, a second telescope module, a first disk gain medium 8, a second disk gain medium 9 and a third reflection module.

[0056] The laser system based on the disk gain in the embodiment of the application realizes laser pulse output with high repetition frequency / high pulse energy, pulse energy up to 200 millijoules, pulse width of 1.6-10 picoseconds and excellent beam quality at normal temperature, and greatly reduces the system. The embodiment adopts a regenerative amplifier based on CPA (chirped amplification), so that the pulse width of the femtosecond seed light is expanded from several hundred femtoseconds to nearly one nanosecond, i.e. the nanosecond laser pulse, thereby avoiding damage of the high peak power pulse to the optical elements in the cavity. The regenerative amplifier can amplify the seed source with pulse energy of microjoules to laser output with pulse energy of hundreds of millijoules, and the amplification multiple can reach 10 5 to 10 6 . Preferably, in order to further increase the pulse energy close to the joule level, one or more multi-pass amplifiers need to be added, the amplification multiple depends on the input optical power and the number of channels, and generally can reach 2 to 5 times. In order to realize kilowatt-level average power, the laser pulse with joule-level pulse energy lays a foundation. Specifically, the embodiment utilizes two disk crystals (i.e. the first disk gain medium 8 and the second disk gain medium 9) to effectively store energy, improve pulse output energy and increase round-trip gain. Meanwhile, the regenerative amplifier in the embodiment is designed as a ring cavity, so that the input and output can be effectively isolated, the optical rotator is avoided, and the output beam quality is improved. In addition, the regenerative amplifier in the embodiment adopts a double-telescope system structure design in the regenerative amplification laser cavity, so that the laser mode is better matched with the pump spot.

[0057] In specific application scenarios, due to the characteristics of small heat-affected zone and high machining precision, ultrafast laser processing has an irreplaceable role in new fields such as semiconductors and new energy, has become a mainstream competitive field, and has become an important development direction of laser precision manufacturing in recent years. With the rapid development of 3C, automobile, semiconductor, display panel and other industries, the demand for micro-machining of glass, ceramic, OLED and other materials in various industries is becoming higher and higher. The unique advantages of high repetition rate and high energy of the disc ultrafast laser will become the mainstream of future precision equipment and material processing, and will be further widely applied in many economic fields, such as precision machining of consumer electronics, mobile devices, display screens, semiconductors, printed circuit boards, and medical, scientific research and military fields.

[0058] In the field of small and medium power (tens of watts, μJ level), ultrafast lasers have relatively mature technical solutions, but in the field of high performance (hundreds of watts, mJ level), further research is needed. At present, ultrafast laser manufacturers mainly use fiber laser technology, but due to the limitation of fiber mode field area, it is impossible to realize high peak power and high average power ultrafast pulse laser products. Moreover, in the current large-scale scientific research devices, such as optical parametric chirped pulse amplification system (OPCPA), attosecond pulse light source and high-energy X-ray device, high-energy pumping sources are needed, which increases the demand for high-power high-energy pulse pumping lasers. Scaling the OPCPA system to kilohertz repetition rate and terawatt peak power requires hundreds of mJ of picosecond pumping pulses. Therefore, the strategic and application value of the high-energy ultra-short pulse generated by the embodiment of the present application is also very prominent.

[0059] The practical significance of the embodiment of the present application also lies in that the high-power disc laser system (i.e. the disc medium high-energy ultra-short pulse laser regenerative amplifier based on CPA technology) can be directly applied to large scientific research devices, breaking the long-term monopoly of foreign laser manufacturers in this field. The demand of the scientific research market is mainly for 20 to 200 mJ (millijoule) single pulse energy, 1 kHz (kilohertz) repetition frequency, and 1 to 10 ps (picosecond) high pulse energy ultrafast laser system. With the establishment and application development of large-scale scientific research devices, there will be a steady and continuous demand for this system in the future.

[0060] In an embodiment, it further includes an adjustable pulse compressor for pulse width compression of the amplified nanosecond laser pulses, and the second-order dispersion and third-order dispersion provided by the adjustable pulse compressor correspond to the second-order dispersion and third-order dispersion required from femtosecond stretching to nanosecond provided by the chirped Bragg fiber grating, respectively.

[0061] Further, in combination with Figure 2In an embodiment, the adjustable pulse compressor comprises a first grating 011, a second grating 012, a first mirror group 013, a second mirror group 014, a third mirror group 015 and a fourth mirror group 016; wherein the first grating 011 and the second grating 012 are arranged in parallel, and the first mirror group 013 and the third mirror group 015 are arranged on a movable platform.

[0062] The amplified nanosecond laser pulse is diffracted by the first grating 011, and then passes through the first mirror group 013, the second mirror group 014, the third mirror group 015, the second mirror group 014 and the first mirror group 013 in turn, enters the second grating 012 to be diffracted, is reflected by the fourth mirror group 016 to raise the optical axis, and then returns to the second grating 012, and again passes through the first mirror group 013, the second mirror group 014, the third mirror group 015, the second mirror group 014 and the first mirror group 013, and is output by the first grating 011 as compressed light.

[0063] In this embodiment, the adjustable pulse compressor is used to compress the amplified nanosecond laser pulse. In a specific embodiment, the compression range of the adjustable pulse compressor is 1.6-10 picoseconds. Further, if the seed light is phase-modulated before amplification, the compressed pulse width can be less than 1 picosecond.

[0064] Specifically, after the nanosecond laser pulse is diffracted (transmitted or reflected grating) by the first grating 011, it passes through the first mirror group 013, the second mirror group 014, the third mirror group 015, the second mirror group 014, the first mirror group 013 and the second grating 012 in turn, and the bar-shaped light spot composed of each spectral component is reflected by the fourth mirror group 016 to raise the optical axis and is returned to pass through the second grating 012, the first mirror group 013, the second mirror group 014, the third mirror group 015, the second mirror group 014, the first mirror group 013 and the first grating 011 in turn to output the compressed light. Here, the positions of the first mirror group 013 and the third mirror group 015 are adjustable, for example, arranged on a movable platform to achieve the effect of position adjustment.

[0065] In another specific embodiment, in combination with Figure 3 and Figure 4 , the adjustable pulse compressor further comprises a first compressor mirror 017 for reflecting the input laser to the first grating 011, and a second compressor mirror 018 for reflecting and outputting the compressed light output by the second grating 012. Figure 3 and Figure 4 In the above, the direction of the arrow is the direction of the light path, wherein, Figure 3A schematic diagram of the light path of the laser reaching the fourth mirror group 016, Figure 4 A schematic diagram of the light path of the laser returning from the fourth mirror group 016.

[0066] In an embodiment, a pump source 10 is further included for simultaneously pumping the first disc gain medium 8 and the second disc gain medium 9.

[0067] Further, in an embodiment, the pump source 10 splits the pump beam into a first pump beam and a second pump beam through a beam splitter 11, the first pump beam directly irradiates into the first disc gain medium 8, and the second pump beam is reflected into the second disc gain medium 9 through a fourth reflection module.

[0068] In the embodiment, two disc gain media are simultaneously pumped by one pump source, and the pump beam is split and reflected by the beam splitter 11 (for example, a 50 / 50 beam splitter) and the fourth reflection module, so that the regenerative amplifier has a good flat top power of the pump homogenization, the center wavelength is 940 nm or 969 nm, and the pump spot size on the first disc gain medium 8 and the second disc gain medium 9 is 5 to 6 mm.

[0069] In an embodiment, the first reflection module includes a first 0° mirror 12 and a second 0° mirror 13 in the vertical direction and not on the same horizontal line along the light path in sequence;

[0070] The second reflection module includes a third 0° mirror 14 in the vertical direction parallel to the second 0° mirror 13;

[0071] The third reflection module includes a first 45° mirror 15 arranged in a forward direction;

[0072] The fourth reflection module includes a second 45° mirror 16 arranged in a reverse direction.

[0073] In an embodiment, the first telescope module includes a first concave mirror 17 and a first convex mirror 18 along the light path in sequence, and the second telescope module includes a second convex mirror 19 and a second concave mirror 20 along the light path in sequence, wherein the curvature parameters of the first concave mirror 17 and the second concave mirror 20 are the same, and the curvature parameters of the first convex mirror 18 and the second convex mirror 19 are the same.

[0074] In this embodiment, the femtosecond seed light is expanded into nanosecond laser pulse after passing through the fiber circulator and CFBG. The nanosecond laser pulse is linearly p-polarized after passing through the collimator, the optical isolator 3 and the first 1 / 2 wave plate 4 in turn, and then passes through the thin film polarizer 5. The nanosecond laser pulse becomes s-polarized after passing through the electro-optic crystal in the Pockels cell 6 and the second 1 / 2 wave plate 7, and then reflects off the first 0° mirror 12 and the second 0° mirror 13 in the first reflection module, and then passes through the first disk gain medium 8. After extracting the energy stored in the first disk gain medium 8, the nanosecond laser pulse passes through the first concave mirror 17 and the first convex mirror 18 in the first telescope module, and then enters the second telescope module through the third 0° mirror 14 in the second reflection module, and then reaches the second disk gain medium 9 through the second convex mirror 19 and the second concave mirror 20. Here, to ensure that the laser mode is the same at the two disk gain media, the first telescope module and the second telescope module are completely symmetrical in geometry. The two symmetrical telescope modules, together with other mirrors, disk gain crystals and electro-optic crystals in the regenerative amplification laser cavity, form a stable cavity and match the laser mode and the pump spot mode.

[0075] After the nanosecond laser pulse is reflected off the surface of the second disk gain medium 9, it returns to the original light path after passing through the first 45° mirror 15 in the third reflection module and the thin film polarizer 5, completing a light path cycle. At this time, the Pockels cell 6 has been applied with a 1 / 2 wave plate voltage, and the nanosecond laser pulse remains s-polarized after passing through the 1 / 2 wave plate voltage electro-optic crystal and the second 1 / 2 wave plate 7. The s-polarized light passes through the Pockels cell 6 with voltage applied without changing the polarization state, and the s-polarized nanosecond laser pulse can oscillate back and forth in the regenerative amplification laser cavity and repeatedly extract the energy stored in the two disk gain media, thereby achieving efficient amplification of the laser pulse energy. When the energy gain of the nanosecond laser pulse reaches saturation, the driving voltage of the Pockels cell 6 is reduced to 0, the polarization of the nanosecond laser pulse changes from s-polarization to p-polarization after passing through the second 1 / 2 wave plate 7, and the amplified nanosecond laser pulse is output after passing through the thin film polarizer 5 after another cycle.

[0076] Here, it can be understood that in other specific embodiments, the first telescope module and the second telescope module can contain a larger number of convex mirrors and concave mirrors to achieve better matching of the laser mode, and further, the number of telescope modules can also be selected according to the actual scene, as long as the telescope modules are symmetrically distributed. Similarly, the number and reflection angles of the mirrors included in the first reflection module, the second reflection module, the third reflection module and the fourth reflection module can also be selected according to the actual scene.

[0077] In a specific embodiment, the first and second gain media 8, 9 are doped Yb:YAG crystals Figure 5 As shown, during the back-and-forth oscillation of the nanosecond laser pulse in the regenerative amplification laser cavity, due to the symmetrical distribution of the first and second telescope modules and the first and second disk gain media 8, 9, the nanosecond laser pulse has equal spot sizes in the first and second telescope modules, and the same, the first and second disk gain media 8, 9 have equal spot sizes and the same number of crystal ions and stored energy, so that the laser mode and energy density distribution in the cavity have a better match with the pump spot.

[0078] In an embodiment, the Pockels cell 6 is provided with two electro-optic crystals to make the phase modulation of the Pockels cell 6 λ / 2, both of the electro-optic crystals are barium borate crystals, and the clear aperture of the Pockels cell 6 is 80% to 90% of the length of the barium borate crystal.

[0079] The left and right sides of the barium borate crystal are plated with gold or chromium, and the upper and lower ends are plated with 1030nm anti-reflection film.

[0080] In the embodiment, the electro-optic crystal in the Pockels cell 6 is mainly BBO (barium borate) and the like, and a larger clear aperture is required to achieve high-energy pulse output. The two sides of the BBO crystal are plated with gold or chromium, and the upper and lower ends are plated with 1030nm high transmission film. By applying voltage to the gold-plated sides, the phase modulation of the Pockels cell 6 can be λ / 2, thereby controlling the running time of the laser in the amplification cavity. In a specific embodiment, the size of the two BBO crystals is 9x9x20mm 3 , the clear aperture is 85% x 9mm, and the spot diameter on the BBO is 4-5mm.

[0081] In an embodiment, the first and second disk gain media 8, 9 have the same structure, the first disk gain medium 8 has a disc structure, and the disc structure has a diameter of 12-30mm, a thickness of 0.100-0.250mm, and a crystal wedge angle of 0-0.05°.

[0082] The first disk gain medium 8 is a YAG crystal doped with Yb with a mass concentration of 0.3%-10%;

[0083] After polishing, the YAG crystal is plated with 940-969nm and 1030nm anti-reflection film on the upper surface, and 940-969nm and 1030nm reflective film on the rear surface, and the rear surface of the Yb:YAG crystal is directly welded, bonded and / or glued to the heat sink material.

[0084] Alternatively, the first disk gain medium 8 is a Nd 3+CALGO, KYW, KGW, KLW, Lu2O3, Sc2O3 or YVO4 crystal doped with any one of Nd 3+ CALGO, KYW, KGW, KLW, Lu2O3, Sc2O3 or YVO4 crystal doped with any one of Nd

[0085] In this embodiment, the first disk gain medium 8 is arranged in a disc structure, and the diameter of the first disk gain medium 8 is 12 to 30 mm, the thickness is arranged as 0.100 to 0.250 mm, and the wedge angle of the crystal is 0 to 0.05°, for example, 0.02°, etc. The first disk gain medium 8 is a YAG crystal doped with Yb concentration (mass concentration) of 0.3% to 10% (for example, 7%). After high-quality polishing, the upper surface of the crystal is coated with 940 to 969 nm and 1030 nm antireflection film, and the back surface is coated with 940 to 969 nm and 1030 nm reflective film. In addition, the total reflection back surface of the disk crystal is directly welded, bonded and / or glued on a copper tungsten, SiC or diamond heat sink, and the one-dimensional axial high-efficiency heat dissipation can realize the high-power density pumping of the disk.

[0086] In addition, the disk gain medium (i.e. the first disk gain medium 8 and the second disk gain medium 9) in this embodiment can also be a YAG crystal doped with Nd 3+ CALGO, KYW, KGW, KLW, Lu2O3, Sc2O3 or YVO4 crystal doped with any one of Nd 3+ CALGO, KYW, KGW, KLW, Lu2O3, Sc2O3 or YVO4 crystal doped with any one of Nd 3+ CALGO, KYW, KGW, KLW, Lu2O3, Sc2O3 or YVO4 crystal doped with any one of Nd

[0087] In this embodiment, the regenerative amplifier is configured with two Yb:YAG disk crystals which are used as gain media in the regenerative amplifier and are pumped with a full solid-state semiconductor laser pump light (DPSS) to obtain the required energy for amplification. The overall structure of the amplifier is built into a water-cooled single-piece aluminum box, so it has very high thermal stability and mechanical stability.

[0088] The embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple, and the relevant parts are referred to the method part. It should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, some improvements and modifications can be made to the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

[0089] It is further noted that the terminology "first", "second" and the like used in the specification are merely used for differentiating one entity or action from another, and do not necessarily imply any actual physical or logical relationship or order between such entities or actions. Moreover, the use of the term "including", "containing" or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, article or apparatus that comprises a list of elements is not required to comprise only those elements but can include other elements not expressly listed or inherent to such process, method, article or apparatus. An element preceded by "comprises a..." does not, without further restriction, preclude the existence of additional elements of the same nature as those recited.

Claims

1. A disk-based high-energy ultrashort pulse laser regenerative amplifier based on CPA technology, characterized in that, include: Femtosecond laser seed light source, used to provide femtosecond seed light; A chirped Bragg fiber grating is used to broaden the femtosecond seed light into a nanosecond laser pulse; An optically coupled input / output device is used to couple the nanosecond laser pulse into the input and to couple the amplified nanosecond laser pulse out of the output. A regenerative amplification laser cavity is used to regenerate and amplify coupled-input nanosecond laser pulses. The optical coupling input / output device includes an optical fiber coupling collimation module, an optical isolator, a first half-wave plate, and a thin-film polarizer. The regenerative amplified laser cavity includes a Pockels cell, a second half-wave plate, a first reflection module, a second reflection module, a first telescope module, a second telescope module, a first disk gain medium, a second disk gain medium, and a third reflection module; wherein the first telescope module, the first disk gain medium, the second telescope module, and the second disk gain medium are symmetrically distributed about the second reflection module. It also includes an adjustable pulse compressor for pulse width compression of amplified nanosecond laser pulses, the adjustable pulse compressor comprising a first grating, a second grating, a first mirror group, a second mirror group, a third mirror group, and a fourth mirror group; wherein the first grating and the second grating are arranged in parallel, and the first mirror group and the third mirror group are both disposed on a movable platform; The femtosecond seed light is pulse-broadened into a nanosecond laser pulse by the chirped Bragg fiber grating to avoid device damage during the amplification process. The nanosecond laser pulse passes sequentially through the fiber-coupled collimation module, optical isolator and first half-wave plate in the optical coupler input / output device, is converted into linear p-polarization, and passes through the thin film polarizer into the regenerating amplified laser cavity. After passing through the unvoltaged Pockels cell and the second half-wave plate, the nanosecond laser pulse is converted from linear p-polarization to s-polarization, and then enters the first disk gain medium after passing through the first reflection module. The s-polarized femtosecond seed light extracts energy in the first disk gain medium and then passes through the first telescope module, the second reflection module, and the second telescope module in sequence before entering the second disk gain medium to extract energy. After the nanosecond laser pulse extracts energy from the second disk gain medium, it passes through the third reflection module and the thin-film polarizer in sequence and returns to the voltage-applied Pockels cell. The s-polarization is maintained and oscillates back and forth in the regenerating amplified laser cavity to extract energy from the first and second disk gain media multiple times until the energy gain of the nanosecond laser pulse reaches saturation. Then, the amplified nanosecond laser pulse is output through the optical coupling input / output device. It also includes a pump source for simultaneously pumping the first disk gain medium and the second disk gain medium.

2. The disk-based high-energy ultrashort pulse laser regenerative amplifier based on CPA technology according to claim 1, characterized in that, The second-order and third-order dispersions provided by the adjustable pulse compressor correspond to the second-order and third-order dispersions required for femtosecond broadening to nanosecond by the chirped Bragg fiber grating, respectively.

3. The disk-based high-energy ultrashort pulse laser regenerative amplifier based on CPA technology according to claim 1, characterized in that, The amplified nanosecond laser pulse is diffracted by the first grating and then sequentially passes through the first mirror group, the second mirror group, the third mirror group, the second mirror group, and the first mirror group. It then enters the second grating and undergoes diffraction. After being reflected by the fourth mirror group, the optical axis is raised. The pulse then returns to the second grating and passes through the first mirror group, the second mirror group, the third mirror group, the second mirror group, and the first mirror group again before being output as compressed light by the first grating.

4. The disk-based high-energy ultrashort pulse laser regenerative amplifier based on CPA technology according to claim 1, characterized in that, The pump source splits the pump beam into a first pump beam and a second pump beam through a beam splitter. The first pump beam directly illuminates the first disk gain medium, and the second pump beam is reflected into the second disk gain medium through a fourth reflection module.

5. The disk-based high-energy ultrashort pulse laser regenerative amplifier based on CPA technology according to claim 4, characterized in that, The first reflection module includes, along the optical path, a first 0° reflector and a second 0° reflector that are vertically parallel and not on the same horizontal line; The second reflection module includes a third 0° reflector that is vertically parallel to the second 0° reflector; The third reflection module includes a first 45° reflector that is facing forward; The fourth reflection module includes a second 45° reflector positioned in the opposite direction.

6. The disk-based high-energy ultrashort pulse laser regenerative amplifier based on CPA technology according to claim 1, characterized in that, The first telescope module includes a first concave mirror and a first convex mirror along the optical path; the second telescope module includes a second convex mirror and a second concave mirror along the optical path, wherein the first concave mirror and the second concave mirror have the same curvature parameters, and the first convex mirror and the second convex mirror have the same curvature parameters.

7. The disk-based high-energy ultrashort pulse laser regenerative amplifier based on CPA technology according to claim 2, characterized in that, The adjustable pulse compressor has a compression range of 1.6 to 10 picoseconds.

8. The disk-based high-energy ultrashort pulse laser regenerative amplifier based on CPA technology according to claim 1, characterized in that, The Pockels cell contains two electro-optic crystals to modulate the phase of the Pockels cell to λ / 2. Both electro-optic crystals are barium metaborate crystals, and the aperture of the Pockels cell is 80% to 90% of the length of the barium metaborate crystal. The barium metaborate is plated with gold or chromium on both sides and coated with a 1030nm antireflection film at both ends.

9. The disk-based high-energy ultrashort pulse laser regenerative amplifier based on CPA technology according to claim 1, characterized in that, The first disk gain medium and the second disk gain medium have the same structure. The first disk gain medium has a disk-shaped structure with a diameter of 12~30mm, a thickness of 0.100~0.250mm, and a crystal wedge angle of 0~0.05°. The first disk gain medium is a YAG crystal with a Yb doping concentration of 0.3% to 10%; After polishing, the YAG crystal is coated with antireflective films of 940~969 nm and 1030 nm on its upper surface and with reflective films of 940~969 nm and 1030 nm on its rear surface. The rear surface of the Yb:YAG crystal is directly welded, bonded and / or glued to the heat sink material. Alternatively, the first disk gain medium is Nd-doped. 3+ , Ho or Tm 3+ Any one of the following crystals: CALGO, KYW, KGW, KLW, Lu2O3, Sc2O3, or YVO4.

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