Disk Laser

Abstract

The present invention relates to the field of laser technology, and provides a disk laser, comprising: a plurality of pairs of disk crystals are configured into an annular structure, each pair of disk crystals comprises a first disk crystal and a second disk crystal, and the first disk crystal is arranged opposite to the second disk crystal; a plurality of reflectors comprises a first reflector and a plurality of second reflectors, the orthographic projection of the first reflector is located at the center of the annular structure, and the plurality of second reflectors are arranged opposite to the plurality of first disk crystals one by one; a plurality of pump source components are arranged opposite to the plurality of second disk crystals one by one. The above-mentioned disk laser increases the absorption efficiency of the disk crystal by arranging a plurality of pairs of disk crystals, a plurality of reflectors and a plurality of pump source components, and by multi-pass pumping each disk crystal, and utilizes the excellent configuration advantages of the disk crystal to make its heat distribution in the axial direction uniform in one dimension, and the thermal gradient is uniformly distributed, which effectively solves the problem of power and beam quality reduction caused by thermal distortion.

Description

Technical Field

[0001] The present invention relates to the field of laser technology, and in particular to a disk laser. Background Art

[0002] Lasers based on Master Oscillator Power-Amplifier (MOPA), especially end-pumped Master Oscillator Power-Amplifiers, can not only maintain the high beam quality of the Master Oscillator, but also ensure high peak power, high conversion efficiency, and large energy output. Such lasers are widely used in laser processing, remote mapping, space radar and other fields. Semiconductor lasers (Laser Diode, LD) are widely used in Master Oscillator Power Amplifiers as pump sources because they have advantages such as compact structure, long life, high energy conversion efficiency, and easy thermal management compared with traditional lamp pumps. Continuous or quasi-continuous semiconductor lasers have been widely used in small and medium power industrial lasers, and pulsed semiconductor lasers have also been developed. With semiconductor lasers as pump sources, this type of Master Oscillator Power Amplifier has the advantages of high output energy, narrow pulse width, and compact structure, and has a wide range of practical value.

[0003] According to the pumping method, end pumping can be divided into continuous end pumping and pulsed end pumping. Continuous end pumping mostly outputs pump light in the form of optical fiber. The spot of this type of pump light is uniform, and the output power ranges from a few watts to several kilowatts. The MOPA laser with continuous end pumping has good output beam quality (single transverse mode) and high repetition frequency. Its beam quality is 1.28 in the X direction and 1.21 in the Y direction. There are also MOPA lasers that output single pulses with large energy, with a pulse width of 60ns, a repetition frequency of 5kHz, and a beam quality of less than 1.3. However, they all use water cooling because the continuous pumping power is large and generates a lot of heat. As a result, pulsed end pumping appeared. The average power of the pump source is low, and conduction cooling or air cooling can be used, which greatly reduces the chance of contamination of the gain crystal or pump source. Its beam quality is less than 1.5, but the single pulse energy is only 54mJ, which limits the distance of long-range measurement. The side-pumped slab MOPA laser has no water cooling and has a simple structure and high output single pulse energy. However, it uses pulse diode direct pumping, and the uniformity of the pump light affects the beam quality of the output light.

[0004] Existing water-free lasers usually adopt a distributed heat dissipation structure. The pump light output by fiber coupling passes through a diffraction element to decompose the pump light into multiple small beams of equal power, and then inject it into the laser crystal to disperse the original high-power pump light and reduce the heat received per unit area in the laser crystal, thereby achieving the requirement of no water cooling and heat dissipation. In addition, the pump light incident surface of the crystal is coated with an anti-reflection film for the pump light and a reflective film for the output laser. An output mirror is placed behind the crystal, and the output multiple small beams of laser light are then combined into a high-power laser output through a diffraction beam combining element. However, the thickness of the laser crystal in the axial direction of this technology is a key issue that limits the further development of such lasers to high power and high power quality. The thicker the crystal, the worse the uniform heat dissipation ability of the heat dissipation structure in this direction. Due to the accumulation of thermal effects, thermal stress refraction will occur inside the crystal, forming a thermal lens effect, resulting in a reduction in power and beam quality. Summary of the invention

[0005] The present invention provides a disk laser, which is used to solve the defect of the laser in the prior art that the power and beam quality are reduced due to the thick crystal thickness.

[0006] The present invention provides a disk laser, comprising: a plurality of pairs of disk crystals, the plurality of pairs of disk crystals are configured into an annular structure, each pair of disk crystals comprises a first disk crystal and a second disk crystal, the first disk crystal is arranged opposite to the second disk crystal; a plurality of reflectors, the plurality of reflectors comprises a first reflector and a plurality of second reflectors, the orthographic projection of the first reflector is located at the center of the annular structure, and the plurality of second reflectors are arranged opposite to the plurality of first disk crystals respectively; a plurality of pump source components, the plurality of pump source components are arranged opposite to the plurality of second disk crystals respectively; wherein the pump light emitted by each pump source component can pass through the second disk crystal, the first reflector, and the first disk crystal to be incident on the second reflector, and after being reflected by the second reflector, be incident on the second disk crystal along a propagation direction opposite to the initial propagation path.

[0007] According to a disk laser provided by the present invention, the optical axis of each of the second reflectors coincides with the optical axis of the pump source assembly.

[0008] According to a disk laser provided by the present invention, each of the pump source components comprises: a fiber coupling mirror group, the fiber coupling mirror group is arranged opposite to the second disk crystal; and a pump source is connected to the fiber coupling mirror group through an optical fiber.

[0009] According to a disk laser provided by the present invention, the fiber coupling lens assembly includes: a pair of first plano-convex lenses, the two first plano-convex lenses are arranged opposite to each other, the convex surfaces of the two first plano-convex lenses are arranged opposite to each other, one of the two first plano-convex lenses is arranged opposite to the second disk crystal, and the other is connected to the optical fiber.

[0010] A disk laser provided according to the present invention also includes: a second plano-convex lens, which is arranged opposite to the multiple pairs of disk crystals, the first reflector is located between the disk crystals and the second plano-convex lens, and the convex surface of the second plano-convex lens faces the first reflector.

[0011] A disk laser provided according to the present invention further includes: a Q-switched crystal, wherein along the propagation direction of the light, the Q-switched crystal is located downstream of the second plano-convex lens.

[0012] A disk laser provided according to the present invention further includes: a beam combining element, which is located downstream of the Q-switched crystal along the propagation direction of the light.

[0013] A disk laser provided according to the present invention further includes: a heat sink, a plurality of pairs of the disk crystals are arranged on a first side of the heat sink, the heat sink has a second side opposite to the first side, and the second side is used for bonding a semiconductor cooler.

[0014] According to a disk laser provided by the present invention, the surfaces of the first reflector and the second reflector are coated with an anti-reflection film and a high-reflection film, wherein the coating density of the anti-reflection film and the high-reflection film is greater than or equal to 99.5%, the wavelength of light that can be transmitted by the anti-reflection film is 940nm, and the wavelength of light that can be transmitted by the high-reflection film is 1030nm.

[0015] According to a disk laser provided by the present invention, the surface of the second plano-convex lens is coated with a reflective film, the coating density of the reflective film is equal to 97%, and the wavelength of light that can be transmitted by the reflective film is 1030-1050nm.

[0016] The disk laser provided by the present invention increases the absorption efficiency of the disk crystal by arranging multiple pairs of disk crystals, multiple reflectors and multiple pump source components, and performs multi-pass pumping on each disk crystal. The excellent configuration advantage of the disk crystal is utilized to make the heat distribution in the axial direction one-dimensionally uniform, and the thermal gradient distribution is uniform, thereby effectively solving the problem of power and beam quality reduction caused by thermal distortion. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 It is a schematic diagram of the structure of the disk laser provided by the present invention;

[0019] Figure 2 yes Figure 1 Schematic diagram of arrangement of reflectors and disk crystals shown in FIG.

[0020] Reference numerals:

[0021] 11: heat sink; 20: disk crystal; 21: first disk crystal; 22: second disk crystal; 30: reflector; 31: first reflector; 32: second reflector; 41: pump source; 42: optical fiber; 43: optical fiber coupling mirror assembly; 50: second plano-convex lens; 60: Q-switched crystal; 70: beam combining element; 431: first plano-convex lens. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] The features of the terms "first" and "second" in the specification and claims of the present invention may include one or more of the features explicitly or implicitly. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0024] Combine the following Figure 1 and Figure 2 The disk laser of the present invention is described.

[0025] like Figure 1 and Figure 2As shown, in an embodiment of the present invention, the disk laser includes: a plurality of pairs of disk crystals 20, a plurality of reflectors 30, and a plurality of pump source components. The plurality of pairs of disk crystals 20 are configured into an annular structure, and each pair of disk crystals 20 includes a first disk crystal 21 and a second disk crystal 22, and the first disk crystal 21 is arranged opposite to the second disk crystal 22. The plurality of reflectors 30 include a first reflector 31 and a plurality of second reflectors 32, and the orthographic projection of the first reflector 31 is located at the center of the annular structure, and the plurality of second reflectors 32 are arranged opposite to the plurality of first disk crystals 21 one by one. The plurality of pump source components are arranged opposite to the plurality of second disk crystals 22 one by one. Among them, the pump light emitted by each pump source component can pass through the second disk crystal 22, the first reflector 31, and the first disk crystal 21 to be incident on the second reflector 32, and after being reflected by the second reflector 32, it is incident on the second disk crystal 22 along a propagation direction opposite to the initial propagation path.

[0026] Specifically, in this embodiment, the thickness of each disk crystal 20 is several hundred microns, the material of the disk crystal 20 is Yb:YAG, and the doping concentration is 10%. The disk crystal 20 is used as a gain medium. Due to its extremely thin crystal thickness, its temperature in the axial direction is one-dimensionally distributed, and the thermal gradient difference is extremely small, which effectively solves the problem of beam quality deterioration caused by the thermal lens effect. In addition, the extremely thin crystal thickness is very conducive to heat conduction, which greatly reduces the pressure of temperature control of the disk crystal 20.

[0027] A plurality of disk crystals 20 are arranged in a ring structure. In this embodiment, the ring structure may be a rectangular ring or a circular ring. Figure 2 The rectangular ring structure formed by the two pairs of disk crystals 20 shown may also be a circular ring structure formed by three or four pairs of disk crystals 20 , wherein the first disk crystal 21 of each pair of disk crystals 20 needs to be arranged opposite to the second disk crystal 22 .

[0028] Specifically, each second disk crystal 22 is provided with a corresponding pump source component, and the pump source component is used to emit pump light. The pump light is incident on the corresponding second disk crystal 22, and is reflected by the second disk crystal 22 to the first reflector 31, and then reflected by the first reflector 31 to the first disk crystal 21 opposite to the second disk crystal 22, and reflected by the first disk crystal 21 to the second reflector 32 opposite to the first disk crystal 21. After the pump light is reflected by the second reflector 32, it returns to the second disk crystal 22 along the original propagation path. Specifically, the pump light is reflected by the second reflector 32 to the first disk crystal 21 opposite to the second reflector 32, and then reflected by the first disk crystal 21 to the first reflector 31, and finally reflected by the first reflector 31 to the second disk crystal 22. In this process, the pump light passes through a pair of disk crystals 20 twice, so that each disk crystal 20 absorbs the pump light twice, which effectively improves the absorption efficiency of the disk laser for the pump light.

[0029] The disk laser provided in the embodiment of the present invention increases the absorption efficiency of the disk crystal by arranging multiple pairs of disk crystals, multiple reflectors and multiple pump source components, and performs multi-pass pumping on each disk crystal. The excellent configuration advantage of the disk crystal is utilized to make the heat distribution in the axial direction uniform in one dimension, and the thermal gradient distribution is uniform, thereby effectively solving the problem of power and beam quality reduction caused by thermal distortion.

[0030] Furthermore, in an embodiment of the present invention, the surfaces of the first reflector 31 and the second reflector 32 are coated with an anti-reflection film and a high-reflection film, wherein the coating density of the anti-reflection film and the high-reflection film is greater than or equal to 99.5%, the wavelength of light that can be transmitted by the anti-reflection film is 940nm, and the wavelength of light that can be transmitted by the high-reflection film is 1030nm.

[0031] Further, in the embodiment of the present invention, the optical axis of each second reflector 32 coincides with the optical axis of the pump source assembly, that is, the angle between the second reflector 32 and the optical axis of the corresponding pump source assembly is 0°.

[0032] like Figure 1 and Figure 2 As shown, in the embodiment of the present invention, each pump source assembly includes: a pump source 41, an optical fiber 42 and an optical fiber coupling mirror set 43. The pump source 41 is connected to the optical fiber coupling mirror set 43 through the optical fiber 42, and the optical fiber coupling mirror set 43 is arranged opposite to the second disk crystal 22.

[0033] Specifically, the pump light emitted by the pump source 41 is homogenized and shaped by the optical fiber 42 and then enters the optical fiber coupling mirror group 43. The optical fiber coupling mirror group 43 performs 1:2 beam expansion and collimation on the pump light, and then injects it into the second disk crystal 22 arranged opposite to the optical fiber coupling mirror group 43. Optionally, in this embodiment, the core diameter of the optical fiber 42 is 800 microns.

[0034] Furthermore, the fiber coupling lens assembly 43 includes a pair of first plano-convex lenses 431. The two first plano-convex lenses 431 are disposed opposite to each other, the convex surfaces of the two first plano-convex lenses 431 are disposed opposite to each other, one of the two first plano-convex lenses 431 is disposed opposite to the second disk crystal 22, and the other is connected to the optical fiber 42.

[0035] Specifically, the two first plano-convex lenses 431 are used to expand and collimate the pump light, and the expansion ratio thereof is 1:2.

[0036] like Figure 1 As shown, in the embodiment of the present invention, the disk laser further includes a second plano-convex lens 50. The second plano-convex lens 50 is arranged opposite to the multiple pairs of disk crystals 20, the first reflector 31 is located between the disk crystals 20 and the second plano-convex lens 50, and the convex surface of the second plano-convex lens 50 faces the first reflector 31. Specifically, the multiple pump lights absorbed by the disk crystals 20 pass through the second plano-convex lens 50 to form a resonant cavity output laser.

[0037] Furthermore, the surface of the second plano-convex lens 50 is coated with a reflective film, the coating density of the reflective film is equal to 97%, and the wavelength of light that can be transmitted by the reflective film is 1030-1050nm.

[0038] Furthermore, the disk laser further includes a Q-switched crystal 60. Along the propagation direction of the light, the Q-switched crystal 60 is located downstream of the second plano-convex lens 50. After the laser outputted by the second plano-convex lens 50 passes through the Q-switched crystal 60, the Q-switched crystal 60 compresses the pulse width, and a sub-nanosecond short-pulse laser can be obtained.

[0039] Furthermore, the disk laser further comprises a beam combining element 70. The beam combining element 70 is located downstream of the Q-switched crystal 60 along the propagation direction of the light.

[0040] Specifically, the pump light absorbed by each disk crystal 20 passes through the second plano-convex lens 50 to form a resonant cavity output laser, and the pulse width of the laser is compressed by the Q-switched crystal 60 to obtain a sub-nanosecond short-pulse laser. Multiple laser beams are combined by the beam combining element 70 to become a laser output with high peak power and high beam quality.

[0041] It should be noted that: in the above-mentioned embodiment, each disk crystal 20 emits a beam of pump light. Figure 2In the embodiment shown, there are 4 disk crystals 20 emitting 4 pump light beams, which are combined into a laser beam after passing through the second plano-convex lens 50, the Q-switched crystal 60 and the beam combining element 70. It can be understood that the more disk crystals 20 there are, the higher the peak power and beam quality of the laser beam formed after the combination.

[0042] Furthermore, if Figure 1 As shown, in an embodiment of the present invention, the disk laser further includes a heat sink 11. A plurality of pairs of disk crystals 20 are disposed on the surface of the heat sink 11. Specifically, in this embodiment, the heat sink 11 is made of copper, a plurality of disk crystals 20 are disposed on one side of the heat sink 11, and the other side of the heat sink 11 is used to bond a semiconductor cooler to dissipate heat from the disk crystals 20.

[0043] The disk laser provided by the embodiment of the present invention has the advantages of solid lasers such as small size and low power consumption, and can take into account good beam quality while ensuring high peak power. Multiple pairs of disk crystals are welded on the heat sink respectively, and multiple pump source components are used to perform multi-pass pumping on the relatively arranged disk crystals respectively, thereby increasing the absorption efficiency of the disk crystals; utilizing the excellent configuration advantages of the disk crystal, its heat distribution in the axial direction is one-dimensionally uniformly distributed, and the thermal gradient is evenly distributed, which effectively solves the problem of power and beam quality reduction caused by thermal distortion. At the same time, this configuration effectively reduces the cavity length of the resonant cavity, and the pulse width can be effectively compressed after passing through the Q-switched crystal, thereby obtaining a laser with a sub-nanosecond width, and then after being combined by the beam combining element, a high peak power, narrow pulse width, and high beam quality laser is obtained.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A disk laser, characterized in that: include: A plurality of pairs of disc crystals, wherein the plurality of pairs of disc crystals are configured into a ring structure, each pair of disc crystals comprises a first disc crystal and a second disc crystal, and the first disc crystal is arranged opposite to the second disc crystal; A plurality of reflectors, wherein the plurality of reflectors include a first reflector and a plurality of second reflectors, the orthographic projection of the first reflector is located at the center of the annular structure, and the plurality of second reflectors are respectively arranged opposite to the plurality of first disk crystals one by one; A plurality of pump source components, wherein the plurality of pump source components are respectively arranged opposite to the plurality of the second disk crystals one by one; The pump light emitted by each of the pump source components can pass through the second disk crystal, the first reflector, the first disk crystal and be incident on the second reflector, and after being reflected by the second reflector, be incident on the second disk crystal along a propagation direction opposite to the initial propagation path; the optical axis of each of the second reflectors coincides with the optical axis of the pump source component; Each of the pump source components comprises: a fiber coupling mirror group, the fiber coupling mirror group is arranged opposite to the second disk crystal; a pump source is connected to the fiber coupling mirror group through an optical fiber; The optical fiber coupling lens assembly comprises: a pair of first plano-convex lenses, the two first plano-convex lenses are arranged opposite to each other, the convex surfaces of the two first plano-convex lenses are arranged opposite to each other, one of the two first plano-convex lenses is arranged opposite to the second disk crystal, and the other is connected to the optical fiber; A second plano-convex lens is arranged opposite to the plurality of pairs of disk crystals, the first reflector is located between the disk crystals and the second plano-convex lens, and the convex surface of the second plano-convex lens faces the first reflector; The surfaces of the first reflector and the second reflector are coated with an anti-reflection film and a high-reflection film, wherein the coating density of the anti-reflection film and the high-reflection film is greater than or equal to 99.5%, the wavelength of light that can be transmitted by the anti-reflection film is 940nm, and the wavelength of light that can be transmitted by the high-reflection film is 1030nm.

2. The disk laser according to claim 1, characterized in that: Also includes: A Q-switching crystal is located downstream of the second plano-convex lens along the propagation direction of the light.

3. The disk laser according to claim 2, characterized in that: Also includes: A beam combining element is located downstream of the Q-switching crystal along the propagation direction of the light.

4. The disk laser according to claim 1, characterized in that: Also includes: A heat sink, wherein a plurality of pairs of the disk crystals are arranged on a first side of the heat sink, and the heat sink has a second side opposite to the first side, and the second side is used for bonding a semiconductor refrigerator.

5. The disk laser according to claim 1, characterized in that: The surface of the second plano-convex lens is coated with a reflective film, the coating density of the reflective film is equal to 97%, and the wavelength of light that can be transmitted by the reflective film is 1030-1050nm.

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