CN117913632A - Multiple spherical aberration optimized slab laser amplifier - Google Patents

Abstract

The invention discloses a multi-spherical-aberration-optimized slab laser amplifier, which relates to the technical field of lasers, wherein seed light emitted by a seed source is subjected to one-pass spherical aberration optimization by a seed light spherical aberration optimization module and then is coupled into a slab crystal, the slab crystal receives pumping light to realize particle number inversion and one-pass amplification of the seed light, the amplified light is subjected to spherical aberration inversion by an off-axis reflection type spherical aberration self-compensation module to realize double spherical aberration optimization, and the two-pass light amplification is performed again by the slab crystal, and finally, the laser after the two-pass amplification is subjected to beam shaping and optimization by an amplified light spherical aberration optimization module. The invention utilizes a multiple spherical aberration system, reduces the spherical aberration influence caused by seed light and beam shaping, overcomes the beam quality degradation caused by amplification level lath crystal thermal lens effect, and can realize high-power and high-beam quality pulse laser output.

Description

Multiple spherical aberration optimized slab laser amplifier

Technical Field

The invention relates to the technical field of lasers, in particular to a multi-spherical-aberration-optimized slab laser amplifier.

Background

The solid laser based on the main oscillation power amplification structure has wide application prospect and development potential in the fields of active beacons, earth exploration, underwater communication, laser cleaning, laser etching, photoelectric countermeasure and the like by a simple structure, good stability and high cost performance. Currently, low power pulsed seed lasers are power amplified using a Main Oscillation Power Amplification (MOPA) structure, and are generally classified into disk, rod and slab lasers according to the shape of the gain medium. The disc laser has good research results in terms of power, but has small single-pass gain, needs enough incident power for effectively extracting energy, and has a very thin gain medium so that the disc laser has to adopt a complex multi-pass structure, has complex light path and poor stability, thereby being difficult to be applied to industrialization from a laboratory; the rod-shaped crystal is one of the most widely-developed and widely-applied laser amplification modes at present, but the further development of the rod-shaped crystal is limited due to the low damage threshold value caused by the small surface area and volume, the poor beam quality caused by the large thermal gradient and the like; in contrast, the slab laser amplifier is easier to realize the multi-pass amplification of a space structure, can obtain high-magnification laser amplification power, has simple light path and strong stability, and is suitable for industrial production and practical scene application. However, the slab laser amplifier still has the problem that it is difficult to combine high power and high beam quality because it is limited by the thermal lens effect inside the gain medium. For a short focal length thermal lens generated by a smaller-sized slat, a reflecting mirror is usually placed at the focal position of the thermal lens, so that the spherical aberration of the light beam after one-pass amplification is reversed at 2f and passes through the thermal lens again, thereby realizing spherical aberration self-compensation; however, for a slab laser amplifier with large size and high power, the scheme is not applicable due to the fact that the power density at the focal point is too high and the focal length of a thermal lens is too long, and the compensation effect is not obvious due to the fact that a lens type 4f image transmission system is introduced. Therefore, on the premise of ensuring high peak power, how to obtain a laser amplification system with simple and compact structure and excellent output beam quality is still a problem to be solved.

Disclosure of Invention

The present invention aims to solve the above problems by providing a multiple spherical aberration optimized slab laser amplifier.

The invention realizes the above purpose through the following technical scheme:

A multiple spherical aberration optimized slab laser amplifier comprising

A seed source for generating seed light;

the gain amplification module is used for realizing the inversion of the particle number and amplifying light;

The seed light spherical aberration optimization module is arranged between the seed source and the gain amplification module and is used for collimating and shaping seed light, enabling the seed light to be matched with an amplification level light spot mode, and carrying out spherical aberration elimination treatment on the shaped light beam by utilizing an aspheric lens;

the off-axis reflection type spherical aberration self-compensating module is used for converting positive spherical aberration generated by laser in a gain medium due to a thermal lens effect during one-pass amplification into negative spherical aberration, realizing turning of a one-pass amplification light path in the process, and coupling the laser into the slab crystal for the second time at a specific angle of a second period so as to compensate the negative spherical aberration of the light beam by utilizing the thermal lens effect of the slab crystal;

the amplified light spherical aberration optimization module is used for shaping the laser amplified in the double-pass process into square light spots and eliminating spherical aberration in the vertical direction by utilizing an aspheric cylindrical lens;

the gain amplification module comprises

The slab crystal is used as a gain medium and is used for receiving the pumping light to generate particle number inversion, and meanwhile, when the seed light beam passes through the slab crystal as an optical signal, high-energy state particles in the gain medium are stimulated to downwards transition to form high-energy laser so as to realize optical amplification;

the cooling heat sink is fixed on one side of the large surface of the slab crystal and is used for cooling the slab crystal and reducing heat distortion;

The palladium strip LD pumping array is fixed on one side of the small surface of the lath crystal and is used for generating pumping light and providing energy for the laser working substance to enable the laser working substance to form particle number inversion;

And the pump coupling waveguide is arranged between the palladium strip LD pump array and the slab crystal and is used for uniformly coupling pump light into the slab crystal.

Preferably, the seed light spherical aberration optimization module comprises a first plano-convex spherical lens, a second plano-convex spherical lens, a first plano-concave cylindrical lens, a first plano-convex aspherical mirror and a second plano-convex aspherical mirror.

Preferably, the off-axis reflective spherical aberration self-compensating module comprises a first aspheric mirror and a second aspheric mirror.

Preferably, the magnified light spherical aberration optimization module includes a second plano-concave cylindrical lens, a second plano-convex cylindrical lens, a first plano-convex aspheric cylindrical lens, and a second plano-convex aspheric cylindrical lens.

Preferably, the included angles between the two end faces and the upper surface and the lower surface of the slab crystal are 45 degrees, the incident light of the off-axis reflection type spherical aberration self-compensating module is emitted from the end face of the slab crystal, and the emergent light of the off-axis reflection type spherical aberration self-compensating module is just emitted from the end face to enter another period of the slab crystal.

Preferably, the slab crystal has n Zigzag optical path transmission periods, the maximum selectable m=n-range amplification, and the optical path is led to the next period by using a once off-axis reflective spherical aberration self-compensation module after each range amplification, and the off-axis reflective spherical aberration self-compensation module is used for m-1 times.

Preferably, in the seed light spherical aberration optimization module, the surface type, the curvature radius and the interval of 12 mirror surfaces of the first plano-convex spherical lens, the second plano-convex spherical lens, the first plano-concave cylindrical lens, the first plano-convex aspheric lens and the second plano-convex aspheric lens which are sequentially arranged along the seed light transmission direction are respectively: convex sphere, 67.5mm, 10mm; plane, infinite, 200mm; plane, infinite, 10mm; convex sphere, 22.5mm, 100mm; concave cylindrical surface (vertical direction), -90mm, 10mm; plane, infinite, 400mm; plane, infinite, 10mm; convex cylindrical surface (vertical direction), 270mm, 100mm; convex aspheric surface, 67.5mm, 5mm; plane, infinite, 291.3mm; plane, infinite, 5mm; convex aspherical, 67.5; the aspherical coefficients of the first plano-convex aspherical mirror and the second plano-convex aspherical mirror are-1.245 and 1, respectively.

Preferably, the included angle between the normal line of the first aspheric mirror and the normal line of the second aspheric mirror in the off-axis reflective spherical aberration self-compensating module and the optical axis, the curvature radius and the aspheric coefficients are respectively 37.2 degrees, -600mm and-1; 36.8 DEG, -600mm, -1; the first aspheric mirror and the second aspheric mirror have a spacing of 403.2mm.

Preferably, the second plano-concave cylindrical lens, the second plano-convex cylindrical lens, the first plano-convex aspheric cylindrical lens and the second plano-convex aspheric cylindrical lens in the amplifying optical spherical aberration optimizing module are respectively: concave cylindrical surface (horizontal direction), 45mm, 0, 8mm; plane, infinite, 0, 200mm; plane, infinite, 0, 8mm; convex cylindrical surface (horizontal direction), 135mm, 0, 100mm; convex aspheric cylindrical surface (vertical direction), 145mm, -1.21, 10mm; plane, infinite, 429.6mm, 0; plane, infinite, 10mm, 0; convex aspheric cylindrical surface (vertical direction), 48.3mm, 1.3.

The invention has the beneficial effects that: (1) The invention adopts the double-pass Zigzag solid lath amplification, can obtain near infrared laser with average power in kW level and pulse width in ps level, and meets the requirement of large energy. (2) The seed light spherical aberration optimization module enables the seed source injected into the amplifying stage to have good beam quality, and the beam quality of the subsequent amplified light is effectively optimized. (3) The off-axis reflective spherical aberration self-compensating module converts positive spherical aberration generated by the slat thermal lens effect of the laser after single-pass amplification into negative spherical aberration, and the spherical aberration carried by the extra lens is not introduced, so that the spherical aberration is counteracted positively and negatively after the laser passes through the slat crystal with the positive spherical aberration for the second time, and the light beam quality of the amplifying stage is further optimized. (4) The laser output by the slat amplifier is finally shaped and the beam quality is optimized by the amplifying light spherical aberration optimizing module, so that the laser output with M2 less than 1.2 can be obtained. (5) The invention has simple light path and strong stability, and is suitable for integrated production and industrial application.

Drawings

FIG. 1 is a schematic diagram of the overall structure of the present invention;

FIG. 2 is a schematic diagram of the optical path of the seed light spherical aberration optimization module according to the present invention;

FIG. 3 is a schematic diagram of a slab crystal Zigzag optical path of the present invention;

FIG. 4 is a schematic diagram of an off-axis reflective spherical aberration self-compensating module according to the present invention;

FIG. 5 is a schematic diagram of an optical path of an amplified light spherical aberration optimization module according to the present invention;

FIG. 6 is a diagram of a wavefront of the present invention without optimization by a seed light spherical aberration optimization module;

FIG. 7 is a wavefront map of the present invention optimized by a seed light spherical aberration optimization module;

FIG. 8 is a two-pass enlarged wavefront map of the present invention without an off-axis reflective spherical aberration self-compensating module;

FIG. 9 is a two-pass enlarged wavefront map of an off-axis reflective spherical aberration self-compensating module embodying the present invention;

FIG. 10 is a diagram of the wavefront of the magnified light spherical aberration optimization module of the present invention.

Reference numerals illustrate:

1. A seed source; 2. a first plano-convex ball lens; 3. a second plano-convex ball lens; 4. a first plano-concave cylindrical lens; 5. a first plano-convex cylindrical lens; 6. a first plano-convex aspherical mirror; 7. a second plano-convex aspherical mirror; 8. cooling the heat sink; 9. a lath crystal; 10. a first aspherical mirror; 11. a second aspherical mirror; 12. a pump coupling waveguide; 13. palladium strip LD pump arrays; 14. a second plano-concave cylindrical lens; 15. a second plano-convex cylindrical lens; 16. a first plano-convex aspherical cylindrical lens; 17. and a second plano-convex aspherical cylindrical lens.

Detailed Description

The invention is further described below with reference to the accompanying drawings:

As shown in fig. 1, the invention provides a multi-spherical-aberration-optimized slab laser amplifier, which comprises a seed source 1, wherein the seed source 1 is an optical fiber laser, a solid state laser or an optical fiber-solid mixed laser, the seed light is pulse laser or continuous laser, and the average power is 10W-1 kW; the gain amplification module is used for realizing the inversion of the particle number and amplifying light; the seed light spherical aberration optimization module is arranged between the seed source 1 and the gain amplification module and is used for collimating and shaping seed light, enabling the seed light to be matched with an amplification level light spot mode, and carrying out spherical aberration elimination treatment on the shaped light beam by utilizing an aspheric lens; the off-axis reflection type spherical aberration self-compensating module is used for converting positive spherical aberration generated by laser in a gain medium due to a thermal lens effect during one-pass amplification into negative spherical aberration, realizing turning of a one-pass amplification light path in the process, and coupling the laser into the slab crystal 9 for the second time at a specific angle of a second period, so that the negative spherical aberration of the light beam is compensated by utilizing the thermal lens effect of the slab crystal 9; and the amplified light spherical aberration optimization module is used for shaping the laser amplified in the double pass into square light spots and eliminating spherical aberration in the vertical direction by utilizing an aspheric cylindrical lens.

As shown in fig. 1, further, on the basis of the above embodiment, the gain amplification module includes a slab crystal 9 as a gain medium for receiving the pump light to generate population inversion, and when the seed light beam passes through the slab crystal 9 as an optical signal, the high-energy state particles in the gain medium are stimulated to transition downwards to form high-energy laser light so as to realize optical amplification; the beam quality factor m2<1.5, the average power >1kW after amplifying the light through the slab crystal 9; the cooling heat sink 8 is welded on one side of the large surface of the lath crystal 9 through indium wires and is used for cooling the lath crystal 9, so that heat distortion is reduced; the cooling liquid for cooling the heat sink 8 is water or pentafluoropropane or liquid nitrogen capable of circulating refrigeration; a palladium strip LD pumping array 13 fixed on the facet side of the slab crystal 9 for generating pumping light to energize the laser working substance to form particle number inversion; all LD light emergent surfaces on the palladium bar LD pumping array 13 are coupled with micro lenses for reducing the divergence angle of the X axis of the pumping light; a pump coupling waveguide 12 disposed between the palladium strip LD pump array 13 and the slab crystal 9 for uniformly coupling pump light into the slab crystal 9; the pump coupling waveguide 12 is made of quartz, and 808nm antireflection films are plated on the light incident surface and the light emergent surface. The seed light passes through the slab crystal 9 in a Zigzag propagation path and gain is obtained in the process, and single-pass laser amplification is achieved.

As shown in fig. 1 and 3, further, on the basis of the above embodiment, the angles between the two end surfaces of the slab crystal 9 and the upper and lower surfaces are 45 °, the incident light of the off-axis reflective spherical aberration self-compensating module is emitted from the end surface of the slab crystal 9, and the emitted light of the off-axis reflective spherical aberration self-compensating module enters the other period of the slab crystal 9 just from the end surface. The slab crystal 9 has n Zigzag optical path transmission periods, the maximum selectable m=n-pass amplification, and after each pass amplification, the optical path is led to the next period by using a single off-axis reflective spherical aberration self-compensation module, and the off-axis reflective spherical aberration self-compensation module is used m-1 times in total. In this example, 139 mm. Times.56 mm. Times.4 mm was used for the length. Times.width. Times.thickness of the slab crystal 9; the lath crystal 9 is made of ytterbium ion doped yttrium aluminum garnet, and the doping atomic fraction is 0.6%.

As shown in fig. 3, the position of the slab crystal 9 is adjusted so that the seed light is coupled into the front end face of the slab crystal 9 at an angle of the first period and exits from the rear end face of the slab crystal 9 after being transmitted by total reflection in the slab crystal 9 in the form of Zagzig.

As shown in fig. 1, further, the seed light spherical aberration optimization module includes a first plano-convex spherical lens 2, a second plano-convex spherical lens 3, a first plano-concave cylindrical lens 4, a first plano-convex cylindrical lens 5, a first plano-convex aspherical mirror 6, and a second plano-convex aspherical mirror 7, on the basis of the above embodiment. During operation, the seed source 1 outputs a high-repetition-frequency and narrow-pulse-width circular parallel light beam, the light beam sequentially passes through the first plano-convex spherical lens 2, the second plano-convex spherical lens 3, the first plano-concave cylindrical lens 4 and the first plano-convex cylindrical lens 5 and then becomes a rectangular parallel light beam with spherical aberration, the length and the width of the light beam respectively correspond to the length and the width of the end face of the lath crystal 9, and the light beam passes through a spherical aberration lens designed by Zemax: the wavefront RMS after the first plano-convex aspherical mirror 6 and the second plano-convex aspherical mirror 7 falls to a level of 10-2 lambda. Wherein the wavelength of the seed light is consistent with the working wavelength of the lath crystal 9, and the beam direction of the seed light is parallel to the normal line of the front surface of the first plano-convex spherical lens 2. The focal length of the first plano-convex ball lens 2 is larger than that of the second plano-convex ball lens 3, and the function of the first plano-convex ball lens is to collimate and beam the seed light to be mode-matched with the size of the amplifying-stage light spot in the horizontal direction. The focal length of the first plano-concave cylindrical lens 4 is smaller than that of the first plano-convex cylindrical lens 5, and the focal length of the first plano-concave cylindrical lens 4 is used for collimating and expanding the seed light in the vertical direction to be mode-matched with the amplifying-stage light spot in the vertical direction. The focal lengths of the first plano-convex aspherical mirror 6 and the second plano-convex aspherical mirror 7 are equal, and the focal lengths are used for reducing spherical aberration caused by seed light and shaping process under the condition of not changing the size of the light beam.

As shown in fig. 1, further, in the seed light spherical aberration optimization module, the surface, curvature radius and interval of 12 mirror surfaces of the first plano-convex spherical lens 2, the second plano-convex spherical lens 3, the first plano-concave cylindrical lens 4, the first plano-convex cylindrical lens 5, the first plano-convex aspherical mirror 6 and the second plano-convex aspherical mirror 7, which are sequentially arranged along the seed light transmission direction, are respectively: convex sphere, 67.5mm, 10mm; plane, infinite, 200mm; plane, infinite, 10mm; convex sphere, 22.5mm, 100mm; concave cylindrical surface (vertical direction), -90mm, 10mm; plane, infinite, 400mm; plane, infinite, 10mm; convex cylindrical surface (vertical direction), 270mm, 100mm; convex aspheric surface, 67.5mm, 5mm; plane, infinite, 291.3mm; plane, infinite, 5mm; convex aspherical, 67.5; the aspherical coefficients of the first plano-convex aspherical mirror 6 and the second plano-convex aspherical mirror 7 are-1.245 and 1, respectively.

As shown in fig. 2, after fixing the position of the seed source 1, the centers of the front and rear surfaces of the first plano-convex spherical lens 2, the second plano-convex spherical lens 3, the plano-convex cylindrical lens, the plano-concave cylindrical lens, the first plano-convex aspherical mirror 6, and the second plano-convex aspherical mirror 7 are aligned in order with the seed light optical axis. Adjusting the front and back positions of the lenses to enable focuses of the first plano-convex ball lens 2 and the second plano-convex ball lens 3 to coincide, so that seed light is collimated and expanded into circular parallel light with the width consistent with the width of the end face; the focal points of the plano-convex cylindrical lens and the plano-concave cylindrical lens are overlapped, the length direction of the seed light is collimated and expanded into rectangular parallel light with the same length as the end face, and the expansion multiple can be selected randomly according to design requirements; the focuses of the first plano-convex aspherical mirror 6 and the second plano-convex aspherical mirror 7 are overlapped, and spherical aberration generated after shaping the seed light is reduced.

As shown in fig. 1 and 4, further, the off-axis reflective spherical aberration self-compensating module includes a first aspheric mirror 10 and a second aspheric mirror 11. The off-axis reflection type spherical aberration self-compensating module returns the laser amplified in one pass to the amplifier again through another period with the same light distribution through the first aspheric mirror 10 and the second aspheric mirror 11, and compensates the spherical aberration effect caused by the thermal lens at the same time of performing the second-pass amplification. The incident light of the off-axis reflective spherical aberration self-compensating module is emitted from the end face of the slab crystal 9, and the emitted light of the off-axis reflective spherical aberration self-compensating module is just incident from the end face into another period of the slab crystal 9. The first aspheric mirror 10 and the second aspheric mirror 11 are two parabolic mirror surfaces with the same model, and the mirrors are plated with 30-40 DEG high-reflection films, so that the first-pass amplified light beam can be turned into the lath to be amplified in two passes on the premise of not introducing new spherical aberration.

As shown in fig. 1 and 4, further, on the basis of the above embodiment, the included angles between the normal lines of the first aspheric mirror 10 and the second aspheric mirror 11 and the optical axis, the curvature radius and the aspheric coefficients of the off-axis reflective spherical aberration self-compensating module are respectively 37.2 °, -600mm, -1;36.8 DEG, -600mm, -1; the surface distance between the first aspherical mirror 10 and the second aspherical mirror 11 is 403.2mm.

As shown in fig. 1, further, the magnified light spherical aberration optimization module includes a second plano-concave cylindrical lens 14, a second plano-convex cylindrical lens 15, a first plano-convex aspherical cylindrical lens 16, and a second plano-convex aspherical cylindrical lens 17, on the basis of the above-described embodiment. The magnifying light spherical aberration optimizing module is arranged on the optical axis after two-way magnification, the beams passing through the second plano-concave cylindrical lens 14 and the second plano-convex cylindrical lens 15 are horizontally expanded and collimated, the beams passing through the first plano-convex aspheric cylindrical lens 16 and the second plano-convex aspheric cylindrical lens 17 are vertically contracted to be the same size in the horizontal direction and collimated, and meanwhile, spherical aberration in the vertical direction is optimized by utilizing the aspheric lenses. The focal length of the second plano-concave cylindrical lens 14 in the magnifying light spherical aberration optimizing module is smaller than that of the second plano-convex cylindrical lens 15, and the magnifying light spherical aberration optimizing module is used for collimating and expanding the magnifying light in the horizontal direction. The focal length of the first plano-convex aspherical cylindrical lens 16 is larger than that of the second plano-convex aspherical cylindrical lens 17, and the first plano-convex aspherical cylindrical lens is used for collimating and converging the amplified light in the vertical direction and reducing spherical aberration in the vertical direction.

As shown in fig. 1, further, on the basis of the above embodiment, the surface type, the radius of curvature, the aspherical coefficient, and the interval of the 8 mirror surfaces of the second plano-concave cylindrical lens 14, the second plano-convex cylindrical lens 15, the first plano-convex aspherical cylindrical lens 16, and the second plano-convex aspherical cylindrical lens 17 in the magnifying optical spherical aberration optimizing module, which are sequentially arranged along the laser light transmitting direction, are respectively: concave cylindrical surface (horizontal direction), 45mm, 0, 8mm; plane, infinite, 0, 200mm; plane, infinite, 0, 8mm; convex cylindrical surface (horizontal direction), 135mm, 0, 100mm; convex aspheric cylindrical surface (vertical direction), 145mm, -1.21, 10mm; plane, infinite, 429.6mm, 0; plane, infinite, 10mm, 0; convex aspheric cylindrical surface (vertical direction), 48.3mm, 1.3.

As shown in fig. 5, the centers of the front and rear surfaces of the second plano-concave cylindrical lens 14, the second plano-convex cylindrical lens 15, the first plano-convex aspherical cylindrical lens 16 and the second plano-convex aspherical cylindrical lens 17 are aligned in this order with the optical axes of the amplified light, and the front and rear positions of the lenses are adjusted so that the focuses of the second plano-concave cylindrical lens 14 and the second plano-convex cylindrical lens 15 are overlapped, thereby collimating and expanding the amplified light in the horizontal direction; the focal points of the first plano-convex aspherical cylindrical lens 16 and the second plano-convex aspherical cylindrical lens 17 are superimposed, and the amplified light is collimated and condensed in the vertical direction to reduce aberration.

As shown in fig. 1, in operation, the seed source 1 generates a high-repetition frequency and narrow-pulse-width circular parallel beam, the seed light is shaped into parallel light matched with an amplifying-stage light spot mode by the seed light spherical aberration optimizing module arranged on the seed light emergent light path, the shaped beam is subjected to spherical aberration elimination processing by the aspheric lens, then the particle number is reversed by the gain amplifying module arranged behind the seed light spherical aberration optimizing module and light amplification is realized, meanwhile, the cooling heat sink 8 cools the working lath crystal 9, so that heat distortion is reduced, the palladium-strip LD pumping array 13 and the pumping coupling waveguide 12 arranged on the side surface of the lath crystal 9 generate and transmit pumping light, the lath crystal 9 is excited to realize particle number reversal, then the off-axis reflection spherical aberration self-compensating module arranged on the light path after one-path amplification converts positive spherical aberration generated by the light into negative spherical aberration, and realizes one-path amplification light and gain medium coupling, and thus two-path amplification is carried out, and then the amplifying light spherical aberration optimizing module arranged on the laser output light path of the amplifier reduces the thermal aberration, and the horizontal dimension and the vertical dimension of the amplified light beam are amplified in a uniform direction, and the spherical aberration is reduced in the vertical direction.

As shown in fig. 6, the wavefront rms=27.63 μm after not being optimized by the seed light spherical aberration optimization module; as shown in fig. 7, the wavefront rms= 0.0286 μm after optimization by the seed light spherical aberration optimization module; as shown in fig. 8, the wavefront rms= 38.513 μm after the two-pass amplification without the off-axis reflective self-compensating module is assembled; as shown in fig. 9, the wavefront rms= 1.076 μm after the two-pass amplification by the off-axis reflective self-compensating module is equipped; as shown in fig. 10, the wavefront rms= 0.0885 μm after passing through the amplified light spherical aberration optimization module. The wave front state of the contrast light beam passing through the thermal lens twice under the no-spherical-aberration self-compensation module and the off-axis reflective spherical-aberration self-compensation module is simulated by the thermal lens with the focal distance of 2000, so that the RMS value of the wave reaches 38.5 micrometers at the end face of the crystal when the light is amplified in one pass, and the RMS value is 1.1 after passing through the off-axis reflective spherical-aberration self-compensation module, and the wave front quality is good. In addition, it can be found that the off-axis reflective spherical aberration self-compensating module can deteriorate the wavefront difference between the horizontal direction and the vertical direction, but after the amplifying light spherical aberration optimizing module, the wavefront difference between the two directions is reduced, so that the near infrared pulse laser with high power and high beam quality can be output.

The curvature radius and the aspherical coefficients of the first plano-convex aspherical column lens and the second plano-convex aspherical column lens in the seed light spherical aberration optimization module, the first aspherical mirror and the second aspherical mirror in the off-axis reflection type spherical aberration self-compensation module and the first plano-convex aspherical column lens and the second plano-convex aspherical column lens in the amplified light spherical aberration optimization module are completed by the aid of ZEMAX optical design software.

The specific design method of the first plano-convex aspheric mirror and the second plano-convex aspheric mirror comprises the following steps: the method comprises the steps of utilizing optical design software Zemax to simulate a light source after seed light passes through a shaping lens, sequentially designing curvature radiuses, lens thicknesses and lens sizes of each surface of a first plano-convex aspherical mirror and a second plano-convex aspherical mirror, setting air intervals and aspherical coefficients between the two lenses as variables, opening an evaluation function editor, and setting an optimization guide: the optimization function type selects RMS to optimize the module and the data is shown in table 1.

The Zemax is used for designing an off-axis reflective spherical aberration self-compensating module, and the numerical aperture NA, the wavelength and the field angle in Zemax software are set. An initial lens model is built in a lens data table, the thermal lens focal length f=2000 mm is simulated and designed, a square parallel light beam with the size of 40 x 4mm passes through the simulated thermal lens, and the thermal lens effect in the slab laser amplifier is simulated. An aspherical off-axis mirror is built after the thermal lens, the surface coordinates being defined as:

wherein c is curvature (inverse of curvature radius), r is radial coordinate under the lens unit, k is a conic coefficient, in this embodiment, the mirror surface is made to take a parabolic form, the conic coefficient is-1, the parabolic curvature radius is-600 mm, and the substrate thickness is 40mm; setting Y eccentricity, namely-450 mm and off-axis distance 450mm, adding coordinate interruption, and enabling light reflected by the paraboloid to vertically enter an image plane; the distance from the paraboloid to the image plane is set as a variable, and the distance F between the focus and the paraboloid is obtained by using quick focusing. And then, placing the same aspheric off-axis reflector at the position of 2F, adding coordinate interruption, adjusting the inclination angle of the reflector and the distance between the thermal lens and the reflecting surface, so that the reflected light rays are incident to a second thermal lens simulation lens at an angle meeting the second period of the end surface, and obtaining the spherical aberration self-compensating module based on off-axis reflection, wherein the data can be shown in the table 1.

The specific design method of the first plano-convex aspheric cylindrical lens and the second plano-convex aspheric cylindrical lens comprises the following steps: the method comprises the steps of utilizing optical design software Zemax to simulate a light source for amplifying light after the light passes through a horizontal beam expanding lens, sequentially designing the curvature radius, the lens thickness and the lens size of each surface of a first plano-convex aspheric cylindrical lens and a second plano-convex aspheric cylindrical lens, enabling the focal length of the first plano-convex aspheric cylindrical lens to be larger than that of the second plano-convex aspheric cylindrical lens according to the beam shrinkage multiplying power, setting an air interval aspheric coefficient between the two lenses as a variable, opening an evaluation function editor, and setting an optimization guide: the optimization function type selects RMS to optimize the module and the data is shown in table 1.

Table 1 multiple spherical aberration optimized optical design lens data table

The seed light spherical aberration optimization module can shape the seed light and reduce the wavefront RMS of the light source injected into the amplifying stage to the level of 10 < -2 >. In addition, the aspherical off-axis reflector can simultaneously realize the mirror reflection and focusing of the light path at a special angle, thereby ensuring the image transmission function required by the off-axis reflection type spherical aberration self-compensation module and simultaneously avoiding the extra spherical aberration caused by the spherical lens.

The foregoing is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Those skilled in the art will appreciate that many changes, modifications, substitutions and alterations can be made to these embodiments without departing from the spirit and scope of the invention, which are intended to be within the scope of the invention. The scope of the invention is defined by the claims and their equivalents.

Claims (9)

1. A multiple spherical aberration optimized slab laser amplifier, characterized by: comprising

A seed source for generating seed light;

the gain amplification module is used for realizing the inversion of the particle number and amplifying light;

The seed light spherical aberration optimization module is arranged between the seed source and the gain amplification module and is used for collimating and shaping seed light, enabling the seed light to be matched with an amplification level light spot mode, and carrying out spherical aberration elimination treatment on the shaped light beam by utilizing an aspheric lens;

the off-axis reflection type spherical aberration self-compensating module is used for converting positive spherical aberration generated by laser in a gain medium due to a thermal lens effect during one-pass amplification into negative spherical aberration, realizing turning of a one-pass amplification light path in the process, and coupling the laser into the slab crystal for the second time at a specific angle of a second period so as to compensate the negative spherical aberration of the light beam by utilizing the thermal lens effect of the slab crystal;

the amplified light spherical aberration optimization module is used for shaping the laser amplified in the double-pass process into square light spots and eliminating spherical aberration in the vertical direction by utilizing an aspheric cylindrical lens;

the gain amplification module comprises

The slab crystal is used as a gain medium and is used for receiving the pumping light to generate particle number inversion, and meanwhile, when the seed light beam passes through the slab crystal as an optical signal, high-energy state particles in the gain medium are stimulated to downwards transition to form high-energy laser so as to realize optical amplification;

the cooling heat sink is fixed on one side of the large surface of the slab crystal and is used for cooling the slab crystal and reducing heat distortion;

The palladium strip LD pumping array is fixed on one side of the small surface of the lath crystal and is used for generating pumping light and providing energy for the laser working substance to enable the laser working substance to form particle number inversion;

And the pump coupling waveguide is arranged between the palladium strip LD pump array and the slab crystal and is used for uniformly coupling pump light into the slab crystal.

2. A multiple spherical aberration optimized slab laser amplifier according to claim 1, wherein: the seed light spherical aberration optimization module comprises a first plano-convex spherical lens, a second plano-convex spherical lens, a first plano-concave cylindrical lens, a first plano-convex aspheric mirror and a second plano-convex aspheric mirror.

3. A multiple spherical aberration optimized slab laser amplifier according to claim 1, wherein: the off-axis reflection type spherical aberration self-compensation module comprises a first aspheric reflector and a second aspheric reflector.

4. A multiple spherical aberration optimized slab laser amplifier according to claim 1, wherein: the amplified light spherical aberration optimization module comprises a second plano-concave cylindrical lens, a second plano-convex cylindrical lens, a first plano-convex aspheric cylindrical lens and a second plano-convex aspheric cylindrical lens.

5. A multiple spherical aberration optimized slab laser amplifier according to claim 1, wherein: the included angles between the two end faces of the slab crystal and the upper surface and the lower surface are 45 degrees, the incident light of the off-axis reflection type spherical aberration self-compensating module is emitted from the end face of the slab crystal, and the emergent light of the off-axis reflection type spherical aberration self-compensating module just enters the other period of the slab crystal from the end face.

6. A multiple spherical aberration optimized slab laser amplifier according to claim 1, wherein: the slab crystal has n Zigzag type optical path transmission periods, the maximum selectable m=n-range amplification is realized, an off-axis reflective spherical aberration self-compensation module is used for introducing an optical path into the next period after each range of amplification, and the off-axis reflective spherical aberration self-compensation module is used for m-1 times.

7. A multiple spherical aberration optimized slab laser amplifier according to claim 2, wherein: the first plano-convex spherical lens, the second plano-convex spherical lens, the first plano-concave cylindrical lens, the first plano-convex aspheric lens and the second plano-convex aspheric lens in the seed light spherical aberration optimization module are respectively: convex sphere, 67.5mm, 10mm; plane, infinite, 200mm; plane, infinite, 10mm; convex sphere, 22.5mm, 100mm; concave cylindrical surface (vertical direction), -90mm, 10mm; plane, infinite, 400mm; plane, infinite, 10mm; convex cylindrical surface (vertical direction), 270mm, 100mm; convex aspheric surface, 67.5mm, 5mm; plane, infinite, 291.3mm; plane, infinite, 5mm; convex aspherical, 67.5; the aspherical coefficients of the first plano-convex aspherical mirror and the second plano-convex aspherical mirror are-1.245 and 1, respectively.

8. A multiple spherical aberration optimized slab laser amplifier according to claim 3, wherein: the included angles between the normal lines of the first aspheric reflector and the second aspheric reflector in the off-axis reflection type spherical aberration self-compensating module and the optical axis, the curvature radius and the aspheric coefficients are respectively 37.2 degrees, -600mm and-1; 36.8 DEG, -600mm, -1; the first aspheric mirror and the second aspheric mirror have a spacing of 403.2mm.

9. A multiple spherical aberration optimized slab laser amplifier according to claim 4, wherein: the second plano-concave cylindrical lens, the second plano-convex cylindrical lens, the first plano-convex aspheric cylindrical lens and the second plano-convex aspheric cylindrical lens in the amplified light spherical aberration optimization module are sequentially arranged along the laser transmission direction, and the surface type, the curvature radius, the aspheric coefficients and the intervals of the 8 mirror surfaces are respectively as follows: concave cylindrical surface (horizontal direction), 45mm, 0, 8mm; plane, infinite, 0, 200mm; plane, infinite, 0, 8mm; convex cylindrical surface (horizontal direction), 135mm, 0, 100mm; convex aspheric cylindrical surface (vertical direction), 145mm, -1.21, 10mm; plane, infinite, 429.6mm, 0; plane, infinite, 10mm, 0; convex aspheric cylindrical surface (vertical direction), 48.3mm, 1.3.