CN114665361A - Disc medium high-energy ultrashort pulse laser regeneration amplifier based on CPA technology - Google Patents

Abstract

The invention discloses a disk medium high-energy ultrashort pulse laser regeneration amplifier based on CPA technology, comprising: a femtosecond laser seed light source for providing femtosecond seed light; the chirped Bragg fiber grating is used for broadening the femtosecond seed light into nanosecond laser pulses; the optical coupling input and output device is used for coupling input of the nanosecond laser pulse and coupling output of the amplified nanosecond laser pulse; the regenerative amplification laser cavity is used for performing regenerative amplification processing on coupled nanosecond laser pulses; the optical coupling input/output device comprises an optical 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 laser pulse output with high repetition frequency and high pulse energy.

Description

Disc medium high-energy ultrashort pulse laser regeneration amplifier based on CPA technology

Technical Field

The invention relates to the technical field of optics, in particular to a disc medium high-energy ultrashort pulse laser regeneration amplifier based on a CPA technology.

Background

Currently, the rapid development of solutions for thermal management and dispersion management of ultrafast lasers enables novel system designs that provide very high average and peak powers and pulse energies. Some laser systems can extend pulse energy to tens or even hundreds of millijoules. Overall, there are currently mainly several implementations:

the plate laser generates sub-picosecond pulses with average power over 1kW at a repetition rate of tens of MHz, and can generate 20mJ pulse energy at 12.5 kHz. However, with a strong asymmetric thermal lensing, the increase in average power is often at the expense of beam quality degradation.

Fiber lasers provide very good beam quality at 100kHz repetition rate with output energy in the mJ range (M2< 1.2). A coherent combination of multiple amplifier channels allows the technique to be extended by using eight channels, spreading the pulse energy to tens of millijoules.

Ultra-low temperature cooling of the laser working substance can achieve pulse energies of tens of mJ at khz repetition rates, but at the expense of a substantial reduction in gain bandwidth. In addition, the current mainstream technologies have technical limitations or defects such as excessively complicated system in realizing hundred milli-joule ultrashort laser pulses.

Disclosure of Invention

The embodiment of the invention provides a disc medium high-energy ultrashort pulse laser regeneration amplifier based on a CPA technology, and aims to realize high repetition frequency/high pulse energy at normal temperature based on a disc gain laser system.

The embodiment of the invention provides a disc medium high-energy ultrashort pulse laser regeneration amplifier based on a CPA technology, which comprises:

a femtosecond laser seed light source for providing femtosecond seed light;

the chirped Bragg fiber grating is used for broadening the femtosecond seed light into nanosecond laser pulses;

the optical coupling input-output device is used for coupling input of the nanosecond laser pulse and coupling output of the amplified nanosecond laser pulse;

the regenerative amplification laser cavity is used for performing regenerative amplification treatment on coupled nanosecond laser pulses;

the optical coupling input/output device comprises an optical fiber coupling collimation module, an optical isolator, a first 1/2 wave plate and a thin film polaroid;

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 telescopic module, a second telescopic module, a first disc gain medium, a second disc gain medium and a third reflection module; the first telescope module, the first disc gain medium, the second telescope module and the second disc gain medium are symmetrically distributed around the second reflection module;

the femtosecond seed light is stretched into nanosecond laser pulses through the chirped Bragg fiber grating pulse so as to avoid the damage of the femtosecond seed light to a device in the amplification process, and the nanosecond laser pulses sequentially pass through a fiber coupling collimation module, an optical isolator and a first 1/2 wave plate in the fiber coupling input-output device, are converted into linear p polarization and pass through the thin film polaroid to enter a regenerative amplification laser cavity;

the nanosecond laser pulse passes through the pockels cell without voltage and the second 1/2 wave plate, is converted into s polarization from linear p polarization, and enters the first disc gain medium after passing through the first reflection module; the s-polarized femtosecond seed light extracts energy in the first disc gain medium, then sequentially passes through the first telescopic module, the second reflecting module and the second telescopic module, and then enters the second disc gain medium to extract energy;

the nanosecond laser pulse extracts energy in the second disc gain medium, then sequentially passes through the third reflection module and the thin film polaroid, returns to the Pockels cell with the applied voltage, keeps s polarization to reciprocate in the regenerative amplification laser cavity to extract the energy in the first disc gain medium and the second disc gain medium for multiple times until the energy gain of the nanosecond laser pulse is saturated, and then outputs the amplified nanosecond laser pulse through the optical coupling input-output device.

And the second-order dispersion and the third-order dispersion provided by the adjustable pulse compressor respectively correspond to the second-order dispersion and the third-order dispersion required by the chirped Bragg fiber grating for stretching from femtosecond to nanosecond.

Further, the adjustable pulse compressor comprises a first grating, a second grating, a first reflector group, a second reflector group, a third reflector group and a fourth reflector group; the first grating and the second grating are arranged in parallel, and the first reflector group and the third reflector group are both arranged on a movable platform;

enlarged nanosecond laser pulse passes through behind first speculum group, second speculum group, third speculum group, second speculum group and the first speculum group in proper order behind the diffraction of first grating, get into the diffraction takes place for the second grating to realize through the reflection of fourth speculum group after the optical axis is raised, then return to the second grating to again through first speculum group, second speculum group, third speculum group, second speculum group and first speculum group back, by first grating output compression light.

Further, the optical disc drive also comprises a pumping source for simultaneously pumping the first disc gain medium and the second disc gain medium.

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 the first disc gain medium, and the second pump beam is reflected to the second disc gain medium through a fourth reflection module.

Further, the first reflection module sequentially comprises a first 0-degree reflection mirror and a second 0-degree reflection mirror which are parallel in the vertical direction and are not on the same horizontal line along the light path;

the second reflection module comprises a third 0-degree reflection mirror which is parallel to the second 0-degree reflection mirror in the vertical direction;

the third reflection module comprises a first 45-degree reflection mirror arranged in the forward direction;

the fourth reflecting module comprises a second 45-degree reflecting mirror arranged in the opposite direction.

Further, the first telescopic module sequentially comprises a first concave mirror and a first convex mirror along the optical path; the second telescope module sequentially comprises a second convex mirror and a second concave mirror along the light 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.

Furthermore, the compression range of the adjustable pulse compressor is 1.6-10 picoseconds.

Furthermore, two electro-optical crystals are arranged in the Pockels cell, so that the phase modulation of the Pockels cell is lambda/2, the two electro-optical crystals are barium metaborate crystals, and the clear aperture of the Pockels cell is 80% -90% of the length of the barium metaborate crystals;

the left side and the right side of the barium metaborate are plated with gold or chromium, and the upper end and the lower end of the barium metaborate are plated with anti-reflection films of 1030 nm.

Further, the first disc gain medium and the second disc gain medium have the same structure, the first disc gain medium is of a disc-shaped structure, the diameter of the disc-shaped structure is 12-30 mm, the thickness of the disc-shaped structure is 0.100-0.250 mm, and the crystal wedge angle is 0-0.05 degrees;

the first disk gain medium is a YAG crystal doped with Yb with the mass concentration of 0.3-10%;

after the YAG crystal is polished, anti-reflection films of 940-969 nm and 1030nm are plated on the upper surface of the YAG crystal, reflection films of 940-969 nm and 1030nm are plated on the rear surface of the YAG crystal, and Yb: the rear surface of the YAG crystal is directly welded, bonded and/or glued on the heat sink material;

or, the first disk gain medium is doped Nd³⁺Ho or Tm³⁺CALGO, KYW, KGW, KLW and Lu of any one of the above₂O₃、Sc₂O₃Or YVO₄And (4) crystals.

The embodiment of the invention provides a CPA technology-based disc medium high-energy ultrashort pulse laser regeneration amplifier, which comprises a femtosecond laser seed light source, a CPA optical fiber laser regeneration amplifier and a CPA optical fiber laser regeneration amplifier, wherein the femtosecond laser seed light source is used for providing femtosecond seed light; the chirped Bragg fiber grating is used for broadening the femtosecond seed light into nanosecond laser pulses; the optical coupling input-output device is used for coupling input of the nanosecond laser pulse and coupling output of the amplified nanosecond laser pulse; the regenerative amplification laser cavity is used for performing regenerative amplification processing on coupled nanosecond laser pulses; the optical coupling input/output device comprises an optical fiber coupling collimation module, an optical isolator, a first 1/2 wave plate and a thin film polaroid; 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 telescopic module, a second telescopic module, a first disc gain medium, a second disc gain medium and a third reflection module; the first telescope module, the first disc gain medium, the second telescope module and the second disc gain medium are symmetrically distributed around the second reflection module; the femtosecond seed light is stretched into nanosecond laser pulses through the chirped Bragg fiber grating pulse so as to avoid the damage of the femtosecond seed light to a device in the amplification process, and the nanosecond laser pulses sequentially pass through a fiber coupling collimation module, an optical isolator and a first 1/2 wave plate in the fiber coupling input-output device, are converted into linear p polarization and pass through the thin film polaroid to enter a regenerative amplification laser cavity; the nanosecond laser pulse passes through the pockels cell without voltage and the second 1/2 wave plate, is converted into s polarization from linear p polarization, and enters the first disc gain medium after passing through the first reflection module; the s-polarized femtosecond seed light extracts energy in the first disc gain medium, then sequentially passes through the first telescopic module, the second reflecting module and the second telescopic module, and then enters the second disc gain medium to extract energy; the nanosecond laser pulse extracts energy in the second disc gain medium, then sequentially passes through the third reflection module and the thin film polaroid, returns to the Pockels cell with the applied voltage, keeps s polarization to reciprocate in the regenerative amplification laser cavity to extract the energy in the first disc gain medium and the second disc gain medium for multiple times until the energy gain of the nanosecond laser pulse is saturated, and then outputs the amplified nanosecond laser pulse through the optical coupling input-output device. The laser system based on the disc gain in the embodiment of the invention has high repetition frequency/high pulse energy at normal temperature, the pulse energy can reach 200mJ, the pulse width is 1.6-10 picoseconds, the laser pulse output with excellent beam quality is excellent, and the system is greatly reduced.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is a system diagram of a CPA technology-based disc medium high-energy ultrashort pulse laser regeneration amplifier according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of the optical path of an adjustable pulse compressor in a CPA technology based disc medium high-energy ultrashort pulse laser regeneration amplifier according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of sub-optical paths of an adjustable pulse compressor in a CPA technology-based disc medium high-energy ultrashort pulse laser regeneration amplifier according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of another sub-optical path of an adjustable pulse compressor in a CPA technology based disc medium high-energy ultrashort pulse laser regeneration amplifier according to an embodiment of the present invention;

fig. 5 is a schematic diagram of laser mode distribution of a reproduction amplifying laser cavity in a CPA technology-based disc medium high-energy ultrashort pulse laser reproduction amplifier according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It will be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

It is also to be understood that the terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the specification of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It should be further understood that the term "and/or" as used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

Referring to fig. 1, an embodiment of the invention provides a disc medium high-energy ultrashort pulse laser regeneration amplifier based on CPA technology, including:

a femtosecond laser seed light source 1 for providing femtosecond seed light;

the chirped Bragg fiber grating 2 is used for broadening the femtosecond seed light into nanosecond laser pulses;

the optical coupling input-output device is used for coupling input of the nanosecond laser pulse and coupling output of the amplified nanosecond laser pulse;

the regenerative amplification laser cavity is used for performing regenerative amplification processing on coupled nanosecond laser pulses;

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

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; the first telescope module, the first disc gain medium, the second telescope module and the second disc gain medium are symmetrically distributed around the second reflection module;

the femtosecond seed light is subjected to pulse stretching by the chirped Bragg fiber grating 2 to form a nanosecond laser pulse so as to avoid device damage of the femtosecond seed light in the amplification process, and the nanosecond laser pulse sequentially passes through a fiber coupling collimation module, an optical isolator 3 and a first 1/2 wave plate 4 in the fiber coupling input-output device, is converted into linear p polarization, and passes through the thin film polaroid 5 to enter a regenerative amplification laser cavity;

the nanosecond laser pulse passes through the pockels cell 6 without voltage and the second 1/2 wave plate 7, is converted into s polarization from linear p polarization, and enters the first disc gain medium 8 after passing through the first reflection module; the s-polarized nanosecond laser pulse extracts energy in the first disc gain medium 8, then sequentially passes through the first telescopic module, the second reflection module and the second telescopic module, and then enters the second disc gain medium 9 to extract energy;

the nanosecond laser pulse extracts energy in the second disc gain medium 9, then sequentially passes through the third reflection module and the thin film polaroid, then returns to the pockels cell 6 with the applied voltage, keeps s polarization to reciprocate in the regenerative amplification laser cavity to extract the energy in the first disc gain medium 8 and the second disc gain medium 9 for many times until the energy gain of the nanosecond laser pulse is saturated, and then outputs the amplified nanosecond laser pulse through the optical coupling input-output device.

The present embodiment provides a disc medium high-energy ultrashort pulse laser regenerative amplifier based on CPA technology, which mainly includes a femtosecond laser seed light source 1, a chirped bragg fiber grating 2, an optical coupling input-output device and a regenerative amplification laser cavity, wherein the optical coupling input-output device includes an optical fiber coupling collimation module, an optical isolator 3, a first 1/2 wave plate 4 and a thin film polarizer 5, and the regenerative amplification laser cavity includes 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 disc gain medium 8, a second disc gain medium 9 and a third reflection module.

The laser system based on the disc gain in the embodiment of the invention realizes laser pulse output with high repetition frequency/high pulse energy, pulse energy of 200mJ, pulse width of 1.6-10 picoseconds and excellent beam quality at normal temperature, and greatly reduces the system. In the embodiment, a CPA (chirped amplification) based regenerative amplifier is adopted, and the pulse width of the femtosecond seed light is widened from hundreds of femtoseconds to nearly one nanosecond, namely, the femtosecond seed light is widened to the nanosecond laser pulse, so that the damage of the pulse with high peak power to the optical element in the cavity is avoided. The regenerative amplifier can amplify the seed source with pulse energy of micro-focus to laser output of hundred milli-focuses, and the amplification factor can reach 10⁵To 10⁶. Preferably, in order to further increase the pulse energy to approach joule level, one or more multi-pass amplifiers are added, and the amplification factor depends on the input optical power and the number of channels, and can generally reach 2 to 5 times. The method lays a foundation for realizing laser light pulse with kilowatt-level average power and joule-level pulse energy. Specifically, the present embodiment utilizes two disc crystals (i.e. the first disc gain medium 8 and the second disc gain medium 9) to store energy effectively, thereby increasing the pulse output energy and increasing the round-trip gain. Meanwhile, the regenerative amplifier described in this embodiment is designed as an annular cavity, so that input and output can be effectively isolated, and an optical rotator is not used, thereby improving the quality of output light beams. In addition, the regenerative amplification laser cavity of the regenerative amplifier described in this embodiment adopts a double telescope system structure design, so that the laser mode is better matched with the pumping spot.

In a specific application scene, due to the characteristics of small heat affected zone, high processing precision and the like of ultrafast laser processing, the ultrafast laser processing can not be replaced in the novel fields of semiconductors, new energy and the like, has become a mainstream competitive field and becomes an important development direction of laser precision manufacturing in the recent years. With the rapid development of the industries such as 3C, automobile, semiconductor, display panel, etc., the micromachining requirements of the industries on the materials such as glass, ceramics, OLED, etc. are higher and higher, and the ultra-short laser pulse advantage of the ultra-fast disc laser with unique high repetition frequency and high energy will become the mainstream in the aspect of future precision equipment and material processing, and will be further applied to a great number of economic fields in a large scale, such as: precision processing of consumer electronics, mobile devices, display screens, semiconductors, printed circuit boards, and the like, and in the medical, scientific and military fields.

The ultra-fast laser in the middle and small power field (tens of watts, mu J level) has a mature technical scheme, but the ultra-fast laser needs to be deeply researched in the high performance field (hundreds of watts, mJ level). At present, ultrafast laser manufacturers mainly adopt a fiber laser technology, but due to the limitation of the area of a fiber mode field, ultrafast pulse laser products with high peak power and high average power cannot be realized. In addition, in the current large-scale scientific research devices, such as high-energy pumping sources needed in the fields of optical parametric chirped pulse amplification systems (OPCPA), attosecond pulse light sources, high-energy X-ray devices and the like, the demand for high-power high-energy pulse pumping lasers is increased. Whereas scaling an OPCPA system to the texawatt peak power of a kilohertz repetition rate requires picosecond pump pulses with an energy of hundreds of mJ. Therefore, the strategy and application value of the high-energy ultrashort pulse generated by the embodiment of the invention are also very obvious.

The practical significance of the embodiment of the invention is that the high-power disc laser system (namely the disc medium high-energy ultrashort pulse laser regenerative amplifier based on the CPA technology) can be directly applied to large scientific research devices, and the long-term monopoly of foreign laser manufacturers on the field is broken. The requirements of the scientific market are mainly 20 to 200mJ (millijoule) single pulse energy, 1kHz (kilohertz) repetition frequency and 1 to 10ps (picosecond) high pulse energy ultrafast laser system. With the establishment and application development of large scientific research devices, there will be a steady and continuous demand for the system in the future.

In one embodiment, the tunable pulse compressor is used for pulse width compression of amplified nanosecond laser pulses, and the second-order dispersion and the third-order dispersion provided by the tunable pulse compressor respectively correspond to the second-order dispersion and the third-order dispersion required by the chirped Bragg fiber grating for stretching from femtosecond to nanosecond.

Further, with reference to fig. 2, in an embodiment, the adjustable pulse compressor includes a first optical grating 011, a second optical grating 012, a first mirror group 013, a second mirror group 014, a third mirror group 015 and a fourth mirror group 016; the first grating 011 and the second grating 012 are arranged in parallel, and the first reflecting mirror group 013 and the third reflecting mirror group 015 are both arranged on a movable platform;

amplified nanosecond laser pulse passes through behind first grating 011 diffraction in proper order through first speculum group 013, second speculum group 014, third speculum group 015, second speculum group 014 and first speculum group 013, get into diffraction takes place for second grating 012 to realize the optical axis through fourth speculum group 016 reflection back and raise, then return to second grating 012, and again through first speculum group 013, second speculum group 014, third speculum group 015, second speculum group 014 and first speculum group 013 after, by first grating 011 output compression light.

In this embodiment, the adjustable pulse compressor is used to compress the amplified nanosecond laser pulse, and 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 and then amplified, the compressed pulse width may be less than 1 picosecond.

Specifically, nanosecond laser pulse passes through first speculum group 013 after the diffraction (transmission or reflection grating) from first grating 011 in proper order, second speculum group 014, third speculum group 015, second speculum group 014, behind first speculum group 013 and the second grating 012, the bar facula that each spectral composition constitutes is raised by fourth speculum group 016 reflection back optical axis and is returned back in proper order through second grating 012, first speculum group 013, second speculum group 014, third speculum group 015, second speculum group 014, first speculum group 013 and the output of first grating 011 are compressed light. Here, the positions of the first reflecting mirror group 013 and the third reflecting mirror group 015 are adjustable, for example, by disposing them on a movable platform, so as to achieve the effect of adjusting the position movement.

In another specific embodiment, in conjunction with fig. 3 and 4, the tunable pulse compressor further comprises a first compressor mirror 017 for reflecting the input laser light to the first grating 011, and a second compressor mirror 018 for reflecting the output compressed light from the second grating 012. In fig. 3 and fig. 4, the direction of the arrow is the traveling direction of the light path, wherein fig. 3 is a schematic view of the light path from the laser to the fourth reflecting mirror set 016, and fig. 4 is a schematic view of the light path from the fourth reflecting mirror set 016 for the optical axis elevation and returning.

In one embodiment, a pump source 10 is further included for simultaneously pumping the first disk gain medium 8 and the second disk gain medium 9.

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 the first disc gain medium 8, and the second pump beam is reflected by a fourth reflection module to the second disc gain medium 9.

In this embodiment, two disc gain media are pumped by one pump source at the same time, and the beam splitter 11 (e.g. 50/50 beam splitter) and the fourth reflection module split and reflect the pump beam, so that the regenerative amplifier has good pumping and homogenizing flat-top power, the center wavelength is 940nm or 969nm, and the pump spot size on the first disc gain medium 8 and the second disc gain medium 9 is 5 to 6 mm.

In an embodiment, the first reflecting module sequentially comprises a first 0 ° reflecting mirror 12 and a second 0 ° reflecting mirror 13 which are parallel in the vertical direction and are not on the same horizontal line along the optical path;

the second reflecting module comprises a third 0-degree reflecting mirror 14 which is parallel to the second 0-degree reflecting mirror 13 in the vertical direction;

the third reflection module comprises a first 45-degree reflection mirror 15 arranged in the forward direction;

the fourth reflective module comprises a second, oppositely disposed, 45 deg. mirror 16.

And, in one embodiment, the first telescope module comprises a first concave mirror 17 and a first convex mirror 18 in sequence along the optical path; the second telescope module comprises 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.

In this embodiment, the femtosecond seed light becomes a nanosecond laser pulse after being broadened by the fiber circulator and the CFBG, and the nanosecond laser pulse becomes linear p-polarization after being collimated and sequentially passing through the optical isolator 3 and the first 1/2 wave plate 4, and then passes through the thin film polarizer 5. The nanosecond laser pulse passes through the electro-optic crystal in the pockels cell 6 and the second 1/2 wave plate 7 which are not applied with voltage, becomes s-polarized, is reflected by the first 0-degree reflector 12 and the second 0-degree reflector 13 in the first reflection module, and then passes through the first disc gain medium 8. After the energy stored in the first disc gain medium 8 is extracted, nanosecond laser pulses pass through the first concave mirror 17 and the first convex mirror 18 in the first telescope module, pass through the third 0-degree reflector 14 in the second reflector module, enter the second telescope module, and reach the second disc gain medium 9 through the second convex mirror 19 and the second concave mirror 20. Here, to ensure that the laser modes at the two disc gain media are identical, the first and second telescopic modules are geometrically perfectly symmetrical. The two symmetrical telescopic modules, other reflectors, disc gain crystals and electro-optical crystals in the regenerative amplification laser cavity form a stable cavity which is matched with a laser mode and a pumping light spot mode.

The nanosecond laser pulse is reflected by the surface of the second disc gain medium 9, then passes through the first 45-degree reflecting mirror 15 and the thin film polarizing film 5 in the third reflecting module, and then returns to the original optical path, and one-time optical path circulation is completed. At this time, 1/2 glass slide voltage is applied to the pockels cell 6, the s polarization of the nanosecond laser pulse is kept unchanged after passing through the 1/2 glass slide voltage electro-optical crystal and the second 1/2 wave plate 7, the polarization state of the s polarized light passing through the pockels cell 6 to which the voltage is applied is unchanged, the s polarized nanosecond laser pulse can be kept to oscillate back and forth in the regenerative amplification laser cavity, and the energy stored in the two disk gain media is repeatedly extracted for many times, so that the effective amplification of the laser pulse energy is realized, the driving voltage of the pockels cell 6 is reduced to 0 until the energy gain of the nanosecond laser pulse is saturated, the polarization of the nanosecond laser pulse is changed from s polarization to p polarization after passing through the second 1/2 wave plate 7, and the nanosecond laser pulse is output after passing through the thin film polarizer 5 after one cycle. And outputting the amplified nanosecond laser pulse to an adjustable pulse width compressor to compress the laser pulse.

Here, it is understood that, in other specific embodiments, the first telescopic module and the second telescopic module may include a greater number of convex mirrors and concave mirrors to achieve better matching of the laser mode, and further, the number of the telescopic modules may also be selected according to an actual scene, and only the telescopic modules need to be symmetrically distributed. Similarly, the reflectors included in the first reflection module, the second reflection module, the third reflection module and the fourth reflection module, regardless of the number or the reflection angle, can be selected according to the actual scene.

In an embodiment, as shown in fig. 5, in the process of oscillating the nanosecond laser pulse back and forth in the reproduction amplification laser cavity, because the first telescope module and the second telescope module are symmetrically distributed, and the first disc gain medium 8 and the second disc gain medium 9 are symmetrically distributed, the sizes of the spots of the nanosecond laser pulse in the first telescope module and the second telescope module are equal, and similarly, the sizes of the spots in the first disc gain medium 8 and the second disc gain medium 9 are equal, and the number of crystal ions and the stored energy are also the same, so that the laser mode and the energy density distribution in the cavity are better matched with the pump spot.

In an embodiment, two electro-optical crystals are arranged in the pockels cell 6, so that the phase modulation of the pockels cell 6 is λ/2, both of the electro-optical crystals are barium metaborate crystals, and the clear aperture of the pockels cell 6 is 80% -90% of the length of the barium metaborate crystals;

the left side and the right side of the barium metaborate are plated with gold or chromium, and the upper end and the lower end of the barium metaborate are plated with anti-reflection films of 1030 nm.

In this embodiment, the electro-optical crystal in the pockels cell 6 is mainly BBO (barium metaborate), etc., and a large clear aperture is required to realize high-energy pulse output. The BBO crystal is plated with gold or chromium on two sides, and high-transmission films of 1030nm are plated on the upper and lower ends. By applying a voltage across the gold plating, the pockels cell 6 can be phase modulated to λ/2, thereby controlling the laser's operating time in the amplification cavity. In one embodiment, two BBO crystals are 9X 20mm in size³The clear aperture is 85% multiplied by 9mm, and the diameter of a light spot on the BBO is 4-5 mm.

In one embodiment, the first disc gain medium 8 and the second disc gain medium 9 have the same structure, the first disc gain medium 8 is a disc-shaped structure, the diameter of the disc-shaped structure is 12-30 mm, the thickness of the disc-shaped structure is 0.100-0.250 mm, and the crystal wedge angle is 0-0.05 °;

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

after the YAG crystal is polished, anti-reflection films of 940-969 nm and 1030nm are plated on the upper surface of the YAG crystal, reflection films of 940-969 nm and 1030nm are plated on the rear surface of the YAG crystal, and Yb: the rear surface of the YAG crystal is directly welded, bonded and/or glued on the heat sink material;

or, the first disk gain medium 8 is doped Nd³⁺Ho or Tm³⁺Any one of CALGO, KYW, KGW, KLW and Lu₂O₃、Sc₂O₃Or YVO₄And (4) crystals.

In this embodiment, the first disk gain medium 8 is configured as a disk structure, and the diameter of the first disk gain medium 8 is 12 to 30mm, the thickness is 0.100 to 0.250mm, and the wedge angle of the crystal is 0 to 0.05 °, such as 0.02 °. The first disk gain medium 8 is a YAG crystal doped with Yb in a concentration (mass concentration) of 0.3% to 10% (e.g., 7%). After high-quality polishing, the upper surface of the crystal is plated with anti-reflection films 940-969 nm and 1030nm, and the rear surface is plated with reflection films 940-969 nm and 1030 nm. In addition, the surface of the fully-reflected disc crystal is directly welded, bonded and/or glued on heat sinks such as copper tungsten, SiC or diamond, and the like, so that the one-dimensional axial high-efficiency heat dissipation can realize the high-power-density pumping of the disc.

In addition, the disc gain media (i.e. the first disc gain media 8 and the second disc gain media 9) in this embodiment may also be doped Nd³⁺Ho or Tm³⁺Any one of CALGO, KYW, KGW, KLW and Lu₂O₃、Sc₂O₃Or YVO₄And (4) crystals. For example, the disk gain medium may be Nd-doped³⁺YVO (YVO)₄The crystal can be Ho-doped CALGO crystal or Ho-doped YVO₄Crystals, and the like.

In this embodiment, the regenerative amplifier is configured with two Yb: YAG disc crystals, which are used as gain media in the regenerative amplifier and pumped with all-solid-state semiconductor laser pumping light (DPSS) to obtain the energy required for amplification. The amplifier overall structure is built into a water-cooled monolithic aluminum case, and therefore has high thermal and mechanical stability.

The embodiments are described in a progressive mode in the specification, the emphasis of each embodiment is on the difference from the other embodiments, and the same and similar parts among the embodiments can be referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description. It should be noted that, for those skilled in the art, it is possible to make several improvements and modifications to the present application without departing from the principle of the present application, and such improvements and modifications also fall within the scope of the claims of the present application.

It should also be noted that, in this specification, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

Claims (10)

1. A disc medium high-energy ultrashort pulse laser regeneration amplifier based on CPA technology is characterized by comprising:

a femtosecond laser seed light source for providing femtosecond seed light;

the chirped Bragg fiber grating is used for broadening the femtosecond seed light into nanosecond laser pulses;

the optical coupling input-output device is used for coupling input of the nanosecond laser pulse and coupling output of the amplified nanosecond laser pulse;

the regenerative amplification laser cavity is used for performing regenerative amplification processing on coupled nanosecond laser pulses;

the optical coupling input/output device comprises an optical fiber coupling collimation module, an optical isolator, a first 1/2 wave plate and a thin film polaroid;

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 telescopic module, a second telescopic module, a first disc gain medium, a second disc gain medium and a third reflection module; the first telescope module, the first disc gain medium, the second telescope module and the second disc gain medium are symmetrically distributed around the second reflection module;

the femtosecond seed light is stretched into nanosecond laser pulses through the chirped Bragg fiber grating pulse so as to avoid the damage of the femtosecond seed light to a device in the amplification process, and the nanosecond laser pulses sequentially pass through a fiber coupling collimation module, an optical isolator and a first 1/2 wave plate in the fiber coupling input-output device, are converted into linear p polarization and pass through the thin film polaroid to enter a regenerative amplification laser cavity;

the nanosecond laser pulse passes through the pockels cell without voltage and the second 1/2 wave plate, is converted into s polarization from linear p polarization, and enters the first disc gain medium after passing through the first reflection module; the s-polarized femtosecond seed light extracts energy in the first disc gain medium, then sequentially passes through the first telescopic module, the second reflecting module and the second telescopic module, and then enters the second disc gain medium to extract energy;

the nanosecond laser pulse extracts energy in the second disc gain medium, then sequentially passes through the third reflection module and the thin film polaroid, returns to the Pockels cell with the applied voltage, keeps s polarization to reciprocate in the regenerative amplification laser cavity to extract the energy in the first disc gain medium and the second disc gain medium for multiple times until the energy gain of the nanosecond laser pulse is saturated, and then outputs the amplified nanosecond laser pulse through the optical coupling input-output device.

2. The CPA technology-based disc medium high-energy ultrashort pulse laser regeneration amplifier of claim 1, further comprising a tunable pulse compressor for pulse width compression of amplified nanosecond laser pulses, wherein the second-order dispersion and the third-order dispersion provided by the tunable pulse compressor respectively correspond to the second-order dispersion and the third-order dispersion required for femtosecond broadening to nanoseconds provided by the chirped Bragg fiber grating.

3. The CPA technology-based disc medium high-energy ultrashort pulse laser regeneration amplifier of claim 1, wherein 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; the first grating and the second grating are arranged in parallel, and the first reflector group and the third reflector group are both arranged on a movable platform;

enlarged nanosecond laser pulse passes through behind first speculum group, second speculum group, third speculum group, second speculum group and the first speculum group in proper order behind the diffraction of first grating, get into the diffraction takes place for the second grating to realize through the reflection of fourth speculum group after the optical axis is raised, then return to the second grating to again through first speculum group, second speculum group, third speculum group, second speculum group and first speculum group back, by first grating output compression light.

4. The CPA technology-based disc medium high-energy ultrashort pulse laser reproduction amplifier of claim 1, further comprising a pump source for simultaneously pumping the first disc gain medium and the second disc gain medium.

5. The CPA technology-based disc medium high-energy ultrashort pulse laser reproduction amplifier of claim 4, wherein 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 the first disc gain medium, and the second pump beam is reflected by a fourth reflection module to the second disc gain medium.

6. The CPA technology-based disc medium high-energy ultrashort pulse laser regeneration amplifier of claim 5, wherein the first reflection module sequentially comprises a first 0 ° mirror and a second 0 ° mirror which are parallel to each other in a vertical direction and are not on the same horizontal line;

the second reflection module comprises a third 0-degree reflection mirror which is parallel to the second 0-degree reflection mirror in the vertical direction;

the third reflection module comprises a first 45-degree reflection mirror arranged in the forward direction;

the fourth reflecting module comprises a second 45-degree reflecting mirror arranged in the opposite direction.

7. The CPA technology-based disc medium high-energy ultrashort pulse laser regeneration amplifier according to claim 1, wherein the first telescope module comprises a first concave mirror and a first convex mirror in sequence along a light path; the second telescope module sequentially comprises a second convex mirror and a second concave mirror along the light 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.

8. A disc medium high-energy ultrashort pulse laser regeneration amplifier based on CPA technology as claimed in claim 2, wherein the compression range of the adjustable pulse compressor is 1.6-10 picoseconds.

9. The CPA technology-based disc medium high-energy ultrashort pulse laser regeneration amplifier as recited in claim 1, wherein two electro-optical crystals are disposed in the Pockels cell, so that the phase modulation of the Pockels cell is λ/2, both of the electro-optical crystals are barium metaborate, and the optical aperture of the Pockels cell is 80% -90% of the length of the barium metaborate;

the left side and the right side of the barium metaborate are plated with gold or chromium, and the upper end and the lower end of the barium metaborate are plated with anti-reflection films of 1030 nm.

10. The CPA technology-based disc medium high-energy ultrashort pulse laser regeneration amplifier of claim 1, wherein the first disc gain medium and the second disc gain medium have the same structure, the first disc gain medium is a disc-shaped structure, the diameter of the disc-shaped structure is 12-30 mm, the thickness of the disc-shaped structure is 0.100-0.250 mm, and the crystal wedge angle is 0-0.05 °;

the first disk gain medium is a YAG crystal doped with Yb with the mass concentration of 0.3-10%;

after the YAG crystal is polished, anti-reflection films of 940-969 nm and 1030nm are plated on the upper surface of the YAG crystal, reflection films of 940-969 nm and 1030nm are plated on the rear surface of the YAG crystal, and Yb: the rear surface of the YAG crystal is directly welded, bonded and/or glued on the heat sink material;

or, the first disk gain medium is doped Nd³⁺Ho or Tm³⁺Any one of CALGO, KYW, KGW, KLW and Lu₂O₃、Sc₂O₃Or YVO₄And (4) crystals.

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