CN113258418A

CN113258418A - Laser amplification system

Info

Publication number: CN113258418A
Application number: CN202110803310.7A
Authority: CN
Inventors: 彭艳红; 杨毅
Original assignee: Sichuan Guangtianxia Laser Technology Co ltd
Current assignee: Sichuan Guangtianxia Laser Technology Co ltd
Priority date: 2021-07-16
Filing date: 2021-07-16
Publication date: 2021-08-13
Anticipated expiration: 2041-07-16
Also published as: CN113258418B

Abstract

The invention provides a laser amplification system, which belongs to the field of solid lasers and comprises a seed source, a pumping source, a gain medium group consisting of a plurality of gain medium units, a pumping light coupling system and a heat sink, wherein the gain medium units are sequentially and symmetrically arranged on two side surfaces of the heat sink and consist of a thin gain medium bottom doped with active ions, an undoped active ion and a triangular prism-shaped laser medium top with an isosceles triangle bottom surface, a columnar array structure is arranged in the heat sink, and cooling liquid flows in gaps of the columnar array structure; seed light emitted by the seed source enters the end gain medium unit within the range of +/-2 degrees of the Brewster angle, enters the next gain medium unit within the range of +/-2 degrees of the Brewster angle after exiting, and periodically propagates in the gain medium group in sequence; and pumping light emitted by the pumping source pumps the gain medium group through the pumping light coupling system. The invention has the advantages of enlarging the size of the gain medium, having the bending resistance effect and realizing the output of high-energy laser with high beam quality.

Description

Laser amplification system

Technical Field

The invention belongs to the field of solid lasers, and particularly relates to a laser amplification system.

Background

The high-energy solid laser has more and more extensive application in the fields of industrial application, scientific research, national defense and military industry, medical treatment and the like, and a laser amplification system is the key point for obtaining high-energy laser output. The large energy pump source inevitably generates a large amount of waste heat during operation of the gain medium, which requires effective thermal management of the gain medium to ensure stable beam quality and laser efficiency. Researches find that the large-energy laser amplifier can reduce the influence of large-size gain media and high-material emission cross sections on energy storage efficiency by adopting a multi-sheet energy storage dispersing mode, and simultaneously meet the requirement that thermal management under repeated frequency is not easy to cause overhigh energy storage density.

The two large surfaces of the traditional lath medium are indium-welded on the heat sink to realize the heat dissipation of the gain medium. The crystal growth generally adopts a Czochralski method, and the crystal growth process limits the size of a slab medium, cannot produce a large-size slab medium and limits the output laser energy.

Disclosure of Invention

The invention provides a laser amplification system, which is characterized in that a plurality of gain medium units which are regularly arranged are arranged on two sides of a heat sink, so that high-energy laser output is obtained, and heat influence is reduced.

The specific technical scheme of the invention is as follows:

a laser amplification system comprises a seed source, a pumping source, a gain medium group consisting of a plurality of gain medium units, a pumping light coupling system and a heat sink, and is characterized in that the gain medium units are composed of a thin gain medium bottom doped with active ions and a laser medium top not doped with the active ions, the laser medium top is a triangular prism with an isosceles triangle bottom surface, and the side surface of the triangular prism where the base side of the isosceles triangle is located is connected with the thin gain medium bottom; the gain medium units are sequentially and symmetrically arranged on two side surfaces of the heat sink; the interior of the heat sink is of a columnar array structure, and cooling liquid flows in gaps of the columnar array structure; seed light emitted by the seed source enters the gain medium unit at the end of the gain medium group within the range of +/-2 degrees of the Brewster angle, enters the next gain medium unit within the range of +/-2 degrees of the Brewster angle after exiting, and periodically propagates in the gain medium group in sequence; and the pumping light emitted by the pumping source pumps the gain medium group through the pumping light coupling system.

Further, the apex angle of the bottom surface of the top portion of the laser medium is cut off to form a quadrangular prism whose bottom surface is an isosceles trapezoid.

Further, the matrix material of the gain medium unit is crystal or ceramic, and the active ion is Nd³⁺、Yb³⁺、Er³ ⁺、Ho³⁺、Tm³⁺、Cr³⁺And Ti³⁺One or two of them.

Further, the pumping source is a laser diode or a flash lamp, the laser diode performs end-face pumping on the top of the laser medium of the end gain medium unit, and the flash lamp performs side-face pumping on the top and the bottom of the heat sink.

Furthermore, the heat sink is formed by welding tungsten copper with one side of a columnar array structure on another smooth tungsten copper, the two tungsten copper jointly form a sealing structure with a water-cooling flow channel inside, and the top end of the columnar array structure is welded on the other smooth tungsten copper.

The invention has the beneficial effects that:

1. the uneven temperature of the slab gain medium can generate the tendency that the periphery of the slab gain medium bends towards the heat sink and drives the heat sink to bend, and gain medium units are symmetrically distributed on two side faces of the heat sink in sequence, so that the tendency that the periphery of the heat sink generated on the upper side face of the heat sink bends downwards and the tendency that the periphery of the heat sink generated on the lower side face of the heat sink bends upwards are offset, and the heat sink is ensured not to bend, so that a gain medium group welded on the heat sink by indium cannot bend or the bending degree is very weak, the bending resistance effect is realized, the wave front distortion is reduced, and the quality of output light beams is improved;

2. the gain medium units are sequentially and symmetrically arranged on the two side surfaces of the heat sink to form a gain medium group with an extra-large size, so that the seed light is transmitted in the gain medium group equivalently to the lath medium with the extra-large size, and the limitation of a crystal growth process on the size of the crystal can be compensated by adopting a plurality of gain medium units, so that the laser output with large energy is realized;

3. because the surface of the gain medium group is exposed outside in a large area, the gain medium group can be pumped in various ways, such as end pumping in the same direction or opposite direction with the seed light, and side pumping on the upper side and the lower side of the heat sink;

4. the invention adopts the bottom of the thin gain medium doped with active ions and the top of the pure matrix laser medium not doped with the active ions, the heat effect is limited at the bottom of the gain medium unit, the surface area of the bottom of the thin gain medium is large, the thickness of the thin gain medium is small, the heat sink can perform good heat dissipation on the thin gain medium, the heat effect is low, and the repetition frequency work can be realized.

Drawings

Fig. 1 is a schematic structural diagram of a laser amplification system according to embodiment 1 of the present invention;

fig. 2 is a schematic diagram of the structure and optical path of a gain medium unit proposed in embodiment 1 of the present invention;

fig. 3 is a schematic structural diagram of a heat sink proposed in embodiment 1 of the present invention;

fig. 4 is a schematic view of an internal partial structure of a heat sink proposed in embodiment 1 of the present invention;

fig. 5 is a schematic crystal bending diagram of a heat sink indium-soldered single-sided gain medium unit according to embodiment 1 of the present invention;

fig. 6 is a schematic crystal bending diagram of a heat sink indium-bonded double-sided gain medium unit according to embodiment 1 of the present invention.

The reference numbers are as follows:

1. a seed source; 2. a pump source; 3. a gain medium group; 4. a heat sink; 4-1, smooth tungsten copper; 4-2, one surface is tungsten copper with a columnar array structure; 5-1. a first dichroic mirror; 5-2. a second dichroic mirror; 6. a polarizing plate; 7. a total reflection mirror; 8.1/2 wave plate.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described with reference to the following embodiments and the accompanying drawings.

The following non-limiting examples are presented to enable those of ordinary skill in the art to more fully understand the present invention and are not intended to limit the invention in any way.

Example 1

The present embodiment provides a laser amplification system, which has a structure as shown in fig. 1, and includes: the device comprises a seed source 1, a pumping source 2, a gain medium group 3 consisting of 16 gain medium units, a heat sink 4, a first dichroic mirror 5-1, a second dichroic mirror 5-2, a polarizing plate 6, a total reflection mirror 7 and an 1/2 wave plate 8.

The 16 gain medium units are sequentially and symmetrically arranged on two side surfaces of the heat sink 4, 8 gain medium units on the upper side surface of the heat sink 4 are sequentially numbered from 001 to 008, and 8 gain medium units on the lower side surface are in one-to-one correspondence with the 001 to 008 gain medium units on the upper side surface and are sequentially numbered from 016 to 009;

the gain medium unit consists of a thin gain medium bottom doped with active ions and a pure matrix laser medium top not doped with the active ions, and the joint of the thin gain medium bottom and the heat sink 4 is plated with SiO₂The top of the laser medium is a triangular prism with an isosceles triangle bottom surface, and the side surface of the triangular prism where the bottom edge of the isosceles triangle is located is bonded with the bottom of the thin gain medium; as shown in fig. 2, the bottom of the thin gain medium is obtained by carrying out thin-film cultivation on YAG (yttrium aluminum garnet) doped with neodymium, wherein the doping concentration of neodymium ions is 1%, and the whole size is carried out by carrying out thin-film cultivation under the condition of 100.59 × 5.00 × 150 mm; pure YAG is adopted at the top of the laser medium, and the size is as follows: bottom edge 90 mm, waist angle α =28.79 °, length 150 mm. The bottom of the thin gain medium and the top of the laser medium are bonded into a pentagonal prism structure, the whole gain medium unit is of a symmetrical structure, and the refractive index of the gain medium to seed light with the wavelength of 1064 nm is 1.82. Fig. 2 is a schematic diagram of the structure and optical path of the gain medium unit. Since the waist angle α =28.79 ° of the gain medium unit, the gain medium can be arranged in a straight line.

The seed source 1 is positioned at one side of a gain medium unit (namely a No. 001 gain medium unit) at the end part of the gain medium group 3 and emits seed light which is parallel to the surface of the heat sink 4 and has the wavelength of 1064 nm; the pumping source 2 is positioned at one side of the gain medium unit (namely, the No. 009 gain medium unit) at the other end of the gain medium group 3, a laser diode pumping source is adopted, and the wavelength of pumping light is 808 nm; the polarizer 6, the total reflection mirror 7, the 1/2 wave plate 8, the first dichroic mirror 5-1 and the second dichroic mirror 5-2 jointly form a pump light coupling system, wherein the first dichroic mirror 5-1 and the second dichroic mirror 5-2 are highly reflective to light with a wavelength of 1064 nm and highly transmissive to light with a wavelength of 808 nm.

As shown in fig. 2, the seed light emitted from the seed source 1 enters one side surface (i.e., interface a) of the top of the laser medium of the 001 th gain medium unit at the brewster angle of 61.21 °, and after being totally reflected at the joint of the bottom of the thin gain medium and the heat sink 4 (i.e., bottom interface b), exits in parallel at the other side surface (i.e., interface c) of the top of the laser medium; and then, the light enters the No. 002 gain medium unit at the Brewster angle of 61.21 degrees, and in the same way, the seed light enters the No. 003 to No. 008 gain medium units at the Brewster angle of 61.21 degrees and periodically propagates in the gain medium units. After being emitted from the No. 008 gain medium unit, the seed light is reflected by the first dichroic mirror 5-1 and the second dichroic mirror 5-2 in sequence, then enters the No. 009 gain medium unit at the Brewster angle 61.21 degrees, enters the No. 010-016 gain medium units at the Brewster angle 61.21 degrees, and continues to periodically propagate in the No. 010-016 gain medium unit.

The pumping light emitted by the pumping source 2 is divided into p light propagating along the original propagation direction and s light reflected by 45 degrees by the polarizer 6, the p light enters the No. 009 gain medium unit at 61.21 degrees after passing through the first dichroic mirror 5-1, enters the No. 010 gain medium unit again after passing through the No. 009 gain medium unit, and continues to propagate periodically; the s light is adjusted by the total reflection mirror 7, then changed into p light after passing through the 1/2 wave plate 8, then enters the No. 008 gain medium unit at 61.21 degrees through the second dichroic mirror 5-2, enters the No. 007 gain medium unit after passing through the No. 008 gain medium unit, and continues to periodically propagate.

The 16 gain medium units are equivalent to an oversized slab medium, and therefore more energy can be extracted by the seed light, and high-power energy output is realized. This is because, when only observing that the seed light propagates in the sheet gain medium bottom of the 16 gain medium units, the seed light turns back and reaches the upper and lower surfaces of the sheet gain medium bottom in a zigzag propagation state, which is consistent with the propagation state of the seed light in the slab medium.

By designing the size of the gain medium unit in the embodiment, the seed light is incident in parallel and emergent in parallel, so that the position relationship of the adjacent gain medium units is simple; and simultaneously, the s light of the pump light is converted into the p light, so that almost all the pump light can be coupled into the gain medium unit.

The seed light and the pump light are both p light, are incident within the Brewster angle and the range of 2 degrees nearby, can realize high transmission (more than 99.9%) of the seed light and the pump light, and avoid plating antireflection films on an incident end face and an emergent end face, thereby avoiding the film layer from being damaged by the laser and obtaining high-energy laser output. Because the gain medium is a triangular prism capable of cutting off three edges and corners, the incident end face and the emergent end face enable the seed light to be parallel to the surface of the heat sink when the seed light is transmitted in the air, a plurality of gain media can be arranged on a rectangular heat sink, the output energy is improved, and the heat dissipation of the gain media is concentrated on one large surface.

As shown in fig. 3 and 4, in this embodiment, the heat sink 4 is formed by welding tungsten copper 4-2 indium, one surface of which is in a columnar array structure, on another smooth tungsten copper 4-1, the two tungsten copper together form a sealing structure with a water-cooling flow channel inside, and the top end indium of the columnar array structure is welded on the other smooth tungsten copper, so that the inside of the heat sink 4 is in the columnar array structure, and the cooling liquid flows in the gap of the columnar array structure; and after two side surfaces of the whole heat sink 4 are ground and polished, indium welding the gain medium unit on the surface.

Because the bottom of the gain medium unit is indium-welded on the heat sink 4 and is cooled by the heat sink 4, the temperature of the area near the surface of the gain medium unit is low during operation, and the other area of the gain medium unit is heated up due to the absorption of laser energy but is not rapidly cooled, so that the temperature of the gain medium unit is not uniform: the top temperature of the pure-matrix laser medium is higher, the temperature of an area at the bottom of the thin gain medium close to the top of the laser medium is highest, and the temperature of an area at the bottom of the thin gain medium close to the surface of the heat sink is low, so that the upper part of the gain medium unit is heated and expanded to cause the tendency that crystals bend and drive the heat sink 4 to bend; the gain medium unit is indium-welded on the heat sink 4, the part of the heat sink 4, which is in contact with the gain medium unit, is a thin layer, the temperature of one side close to the gain medium unit is higher, and the temperature of one side close to the columnar array structure is lower, so the heat sink 4 also has a certain bending tendency due to uneven temperature, as shown in fig. 5, the periphery of the bottom of the thin gain medium has a downward bending tendency, and the center has an upward convex tendency.

However, because the two sides of the heat sink 4 are heated symmetrically, and the upper and lower tungsten copper sheets are supported by the columnar array structure, the downward bending tendency of the periphery of the heat sink 4 generated on the upper side of the heat sink 4 and the upward bending tendency of the periphery of the heat sink 4 generated on the lower side of the heat sink 4 are offset, and the heat sink 4 cannot be bent, as shown in fig. 6, so that the gain medium welded on the heat sink 4 by indium cannot be bent or the bending degree is very weak, thereby realizing the effect of bending resistance, reducing wave front distortion and improving the quality of output light beams.

Claims

1. A laser amplification system comprises a seed source, a pumping source, a gain medium group consisting of a plurality of gain medium units, a pumping light coupling system and a heat sink, and is characterized in that the gain medium units are composed of the bottom of a thin gain medium doped with active ions and the top of a laser medium not doped with the active ions, the top of the laser medium is a triangular prism with an isosceles triangle bottom surface, and the side surface of the triangular prism where the base side of the isosceles triangle is located is connected with the bottom of the thin gain medium; the gain medium units are sequentially and symmetrically arranged on two side surfaces of the heat sink; the interior of the heat sink is of a columnar array structure, and cooling liquid flows in gaps of the columnar array structure; seed light emitted by the seed source enters the end gain medium unit within the range of +/-2 degrees of the Brewster angle, enters the next gain medium unit within the range of +/-2 degrees of the Brewster angle after exiting, and periodically propagates in the gain medium group in sequence; and the pumping light emitted by the pumping source pumps the gain medium group through the pumping light coupling system.

2. The laser amplification system of claim 1, wherein the apex angle of the bottom surface of the top of the laser medium is cut off to form a quadrangular prism having an isosceles trapezoid bottom surface.

3. The laser amplification system of any one of claims 1 and 2,wherein the gain medium unit has a crystal or ceramic matrix material and Nd as an active ion³⁺、Yb³⁺、Er³⁺、Ho³⁺、Tm³⁺、Cr³⁺And Ti³⁺One or two of them.

4. The laser amplification system of any one of claims 1 and 2, wherein the pump source is a laser diode that end-pumps the top of the laser medium of the end gain medium unit or a flash lamp that side-pumps the top of the laser medium of the gain medium unit on the upper and lower sides of the heat sink.

5. The laser amplification system of any one of claims 1 and 2, wherein the heat sink is formed by welding tungsten copper with one surface in a columnar array structure on another smooth tungsten copper, the two tungsten copper together form a sealing structure with a water cooling flow passage inside, and the top end of the columnar array structure is welded on the other smooth tungsten copper.