A high-energy 2940 nm pulsed disk laser based on Er

Abstract

The present invention relates to the field of disk laser technology, and in particular to a high-energy 2940 nanometer pulse disk laser based on Er. It includes a pump source, a collimation and homogenization system, a multi-stroke pump cavity and a resonant cavity arranged in sequence along the optical path, wherein a disk crystal, a plano-concave aspheric reflector and a plurality of prism groups are arranged in the multi-stroke pump cavity, the plano-concave aspheric reflector is an annular structure with a central through hole, and the plano-concave aspheric reflector is used to receive the pump light emitted by the pump source and focus it; the disk crystal is arranged at the focusing center position of the plano-concave aspheric reflector, and is used for pumping light and generating laser beams; the plurality of prism groups are arranged circumferentially around the disk crystal, and are used for secondary angle conversion of the pump light and incident again on the plano-concave aspheric reflector in the form of parallel light. The present invention effectively reduces the thermal lens effect of the crystal, and for the high quantum loss gain medium Er 3+ Doped crystals have good heat dissipation effects and can achieve higher power pumps.

Description

Technical Field

[0001] The invention relates to the technical field of disk lasers, and in particular to a high-energy 2940-nanometer pulse disk laser based on Er. Background Art

[0002] The laser with a wavelength of 2.94μm is in the near-infrared band and has an extremely high instantaneous temperature. The laser with this wavelength is located near the 3um absorption peak of water. Since the laser with a wavelength of 2.94μm is just near the absorption peak of water (3μm), water molecules have a strong absorption effect on this band. In addition, since more than 70% of biological cells are water, the penetration depth of Er laser in biological cell tissue is very shallow. Therefore, the laser with a wavelength of 2.94μm can also avoid damaging other molecular bonds in cells, and it does not have a large thermal damage like the laser produced by carbon dioxide laser. It has very little mechanical damage and thermal damage to the body. Therefore, Er:YAG laser is gradually becoming an important research direction and research hotspot in medical fields such as plastic surgery. It is an ideal scalpel in medicine, so Er laser has broad prospects in the fields of biology and medicine; at the same time, 2.94μm laser can also be used as a pumping light source for optical parametric oscillators to obtain 3-12μm tunable mid-infrared lasers.

[0003] Currently, due to Er 3+ The pump source of the laser is generally pumped at a wavelength near 970nm, and its quantum loss reaches 67%, which is wasted in the form of heat. Usually, a rod-shaped Er:YAG is used as the gain medium, and a diode laser with a wavelength near 970nm is used as the pump source to achieve Q-switched laser pulses. However, due to the huge amount of heat generated by Er:YAG during operation, it is impossible to achieve high repetition frequency operation, usually only a few Hz to tens of Hz, which is far from meeting the current medical and industrial needs. At the same time, due to its severe thermal lens effect under high power, the quality of the laser beam generated under high pumping is relatively poor, making it difficult to carry out precision processing, precision medicine and other fields. Summary of the invention

[0004] In view of the above problems, the purpose of the present invention is to provide a high-energy 2940 nm pulse disk laser based on Er to reduce the thermal lens problem caused by the Er-pumped rod-shaped gain medium, so that it can obtain higher energy pulse laser output.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A high-energy 2940-nanometer pulsed disk laser based on Er comprises a pump source, a collimation and homogenization system, a multi-stroke pump cavity and a resonant cavity arranged in sequence along an optical path, wherein a disk crystal, a plano-concave aspheric reflector and a plurality of prism groups are arranged in the multi-stroke pump cavity, wherein the plano-concave aspheric reflector is an annular structure with a central through hole, and the plano-concave aspheric reflector is used to receive the pump light emitted by the pump source and focus it; the disk crystal is arranged at the focusing center position of the plano-concave aspheric reflector, and is used for pumping the pump light and generating a laser beam; the plurality of prism groups are arranged around the disk crystal along the circumferential direction, and are used for secondary angle conversion of the pump light and incident again on the plano-concave aspheric reflector in the form of parallel light.

[0007] A heat sink is provided on the back side of the disc crystal.

[0008] The front side of the disk crystal is coated with an anti-reflection film, and the rear side is coated with a reflective film. The anti-reflection film is used to improve the transmittance of the pump light, and the reflective film is used to improve the reflectivity of the remaining pump light.

[0009] The thickness of the disc crystal is 50-200um.

[0010] Each of the prism groups includes two prisms, the two prisms are symmetrically arranged relative to a horizontal plane, and the two prisms are perpendicular to each other.

[0011] The number of the prism groups is at least five.

[0012] The collimating and homogenizing system comprises a homogenizing rod and a collimating lens which are sequentially arranged along the optical path.

[0013] The resonant cavity is provided with a Q-switch, an FP standard, a reflector and an output coupling mirror, wherein the Q-switch, the FP standard and the reflector are arranged in sequence along the optical path, and the output coupling mirror OC is arranged at the laser output port of the resonant cavity for pulse output of the laser.

[0014] The resonant cavity corresponds to the central through hole of the plano-concave aspheric reflecting mirror.

[0015] The pump source adopts a diode with a wavelength of 970±10nm.

[0016] The advantages and beneficial effects of the present invention are:

[0017] 1. The present invention reduces the thickness of Er:YAG crystal to 50-200um, so that the waste heat of the crystal is only dissipated along a single axis, effectively reducing the thermal lens effect of the crystal. 3+ The doped crystals have good heat dissipation effects and can obtain higher power pumps, further expanding the application of 2940 nanometers in the fields of medical and broadcasting countermeasures.

[0018] 2. The present invention utilizes a group of reflectors at 90 degrees to each other and an aspheric reflector to form a multi-stroke pumping structure, thereby solving the problem of prism angle calculation in the traditional pumping mode. In terms of processing, it is only necessary to make prisms in pairs, replacing the difficult processing of four different prism groups in the traditional pumping mode, further reducing the cost and design difficulty of the laser.

[0019] 3. The present invention can achieve 2940nm wavelength narrow linewidth output by introducing the FP etalon into the cavity, thereby expanding its application field.

[0020] 4. The present invention compresses the thickness of the Er:YAG gain medium by using disc technology, thereby increasing its diameter-to-thickness ratio (50-100:1), so that the heat flow direction is only along one-dimensional direction, greatly improving its heat exchange efficiency. At the same time, by using acousto-optic Q-switching or electro-optic Q-switching devices, such as RTP, TeO2 and other Q-switching crystals, it is possible to achieve high-energy, kHz pulse laser output, greatly improving the processing efficiency of 2940 nanometer lasers, and further broadening their application fields in medicine, industry and national defense. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the structure of an Er-based high-energy 2940-nanometer pulsed disk laser in an embodiment of the present invention.

[0022] In the figure: 1 is a pump source, 2 is a collimating and homogenizing system, 21 is a homogenizing rod, 22 is a collimating lens, 3 is a disk crystal, 4 is a multi-stroke pump cavity, 5 is a resonant cavity, 6 is a heat sink, 7 is a prism group, 8 is a plano-concave aspheric reflector, 9 is a Q-switch, 10 is a FP etalon, 11 is a reflector, and 12 is an output coupling mirror. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] like Figure 1As shown, the present invention provides a high-energy 2940 nm pulsed disk laser based on Er, comprising a pump source 1, a collimation and homogenization system 2, a multi-stroke pump cavity 4 and a resonant cavity 5 arranged in sequence along the optical path, wherein a disk crystal 3, a plano-concave aspheric reflector 8 and a plurality of prism groups 7 are arranged in the multi-stroke pump cavity 4, the plano-concave aspheric reflector 8 is an annular structure with a central through hole, and the plano-concave aspheric reflector 8 is used to receive the pump light emitted by the pump source 1 and focus it; the disk crystal 3 is arranged at the focusing center position of the plano-concave aspheric reflector 8, and is used for pumping the pump light and generating a laser beam; the plurality of prism groups 7 are arranged around the disk crystal 3 along the circumferential direction, and are used for secondary angle conversion of the pump light and incident on the plano-concave aspheric reflector 8 again in the form of parallel light.

[0025] In the embodiment of the present invention, the pump source 1 uses a diode with a wavelength of 970±10 nm. The collimating and homogenizing system 2 includes a homogenizing rod 21 and a collimating lens 22 arranged in sequence along the optical path, wherein the homogenizing rod 21 uses a polygonal rod or SI type optical fiber, and the material is quartz, sapphire or the like.

[0026] In the embodiment of the present invention, the front side of the disk crystal 3 is coated with an anti-reflection film, and the back side is coated with a reflective film. The anti-reflection film is used to improve the transmittance of the pump light, and the reflective film is used to improve the reflectivity of the remaining pump light. Specifically, the disk crystal 3 uses Er:YAG material with a doping concentration of 50% as the gain medium, and its thickness ranges from 50-200um.

[0027] On the basis of the above embodiment, a heat sink 6 is provided on the back of the disk crystal 3 for back cooling. In this embodiment, the concave surface of the plano-concave aspheric reflector 8 faces the direction of the disk crystal 3, the disk crystal 3 is located at the focusing center of the plano-concave aspheric reflector 8, its front side is used for pumping by pump light, and its back side is welded on the metal heat sink for back cooling; the central through hole of the plano-concave aspheric reflector 8 allows the pump light to pass through, and the surrounding annular belt is used as a reflective end mirror to form a resonant cavity with the rear surface of the gain medium (disk crystal 3).

[0028] In the embodiment of the present invention, each prism group 7 includes two prisms, the two prisms are symmetrically arranged relative to the horizontal plane, and the two prisms are perpendicular to each other. Specifically, the number of prism groups 7 is at least five or more, and they are arranged in a circular array with the crystal focal point as the axis. The function thereof can realize a 24, 48, 72 stroke pumping structure, so that a beam of pumping light passes through the gain medium multiple times, and finally the remaining reflected light is reflected back to the LD (diode) through the reflecting prism.

[0029] In the embodiment of the present invention, the multi-stroke pump cavity 4 adopts a multi-stroke pump structure, so that a beam of pump light is absorbed by the disk crystal 3 24 times. The principle is that the pump light is collimated by the collimation and homogenization system 2 and then incident on the plano-concave aspheric reflector 8, and then the disk crystal 3 obtains the first round of stroke pump light absorption after being focused by the plano-concave aspheric reflector 8; the parallel light reflected by the plano-concave aspheric reflector 8 enters the prism group 7 to complete the optical path turning, and the light is separated and incident on the plano-concave aspheric reflector 8 with a through hole in the center again, and continues to focus on the disk crystal 3 to complete the first round of stroke pumping. The remaining pump light is emitted as parallel light to the plano-concave aspheric reflector 8 with a through hole in the center, and the above process is repeated to complete the second round of crystal pump light absorption process, and the 24 pumping processes are realized in a cycle.

[0030] In an embodiment of the present invention, a Q-switch 9, an FP standard tool 10, a reflector 11 and an output coupling mirror 12 are provided in the resonant cavity 5, wherein the Q-switch 9, the FP standard tool 10 and the reflector 11 are arranged in sequence along the optical path, and the output coupling mirror OC12 is arranged at the laser output port position of the resonant cavity 5 for pulse output of the laser.

[0031] The resonant cavity 5 corresponds to the central through hole of the plano-concave aspheric reflector 8. The reflective film on the rear surface of the disk crystal 3, the Q-switch 9, the output coupling mirror 12, the FP etalon 10 and the reflector 11 constitute the resonant cavity 5, and the pulse output of the laser is achieved by controlling the time of the Q-switch 9. Specifically, the crystal selected by the Q-switch 9 is an RTP crystal and an antimony oxide crystal.

[0032] The present invention processes the gain medium to a thickness of 50-200um and adopts a single-sided pump back-cooling method to work, which greatly solves the problem of thermal lens effect of the crystal, is conducive to the Er:YAG crystal to achieve high-power continuous output, and greatly solves the impact of high quantum loss waste heat caused by 970nm pumping on the device. After two rounds of pump light absorption, the disk crystal 3 generates stimulated spontaneous radiation, which is amplified and output through the resonant cavity 5. By changing the position and direction of the output coupling mirror 12, the resonant cavity can be changed to a straight line, V and Z-shaped cavity, thereby causing different changes in the output characteristics of the laser to obtain multi-mode or fundamental transverse mode output.

[0033] The multi-stroke pumped disk laser of the present invention utilizes multiple groups of reflectors and parabolic mirrors, and realizes a multi-stroke pumping structure by designing a reasonable reflection structure. And through the central hole of the parabola, by adopting multiple pairs of prism groups, the design angle problem of the prism in the existing multi-stroke pumping structure is greatly simplified, and it can be realized by only circumferential arrangement, and at the same time, the distance between the prism and the aspherical mirror is reduced, making the system more compact and conducive to miniaturization. At the same time, RTP and antimony oxide are used as Q-switched crystals in the resonant cavity, so as to realize Q-switched laser output, and the FP standard tool is used for wavelength selection.

[0034] The present invention adopts a multi-stroke pumped thin-slice laser. Since the thickness of the disk crystal 3 is only 200um, its heat conduction direction is only transmitted along the one-dimensional z-axis. By using a 24-stroke pumping structure, the absorption of the Er:YAG laser with a doping concentration of 50% reaches more than 98%, thereby further solving the technical difficulty of too low output power during continuous operation at 2940 nanometers. In addition, by designing a reasonable cavity structure, high-energy Q-switched laser output can be achieved, thereby meeting the application requirements of mid-infrared lasers in industry and medicine.

[0035] The above description is only an embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, expansion, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A high-energy 2940 nm pulsed disk laser based on Er, characterized in that: The invention comprises a pump source (1), a collimation and homogenization system (2), a multi-stroke pump cavity (4) and a resonant cavity (5) arranged in sequence along an optical path, wherein a disk crystal (3), a plano-concave aspheric reflector (8) and a plurality of prism groups (7) are arranged in the multi-stroke pump cavity (4), wherein the plano-concave aspheric reflector (8) is an annular structure with a central through hole, and the plano-concave aspheric reflector (8) is used to receive pump light emitted by the pump source (1) and to focus the pump light; the disk crystal (3) is arranged at the focusing center position of the plano-concave aspheric reflector (8) and is used for pumping the pump light and generating a laser beam; and the plurality of prism groups (7) are arranged around the disk crystal (3) along the circumferential direction and are used for secondary angle conversion of the pump light and for incident again on the plano-concave aspheric reflector (8) in the form of parallel light.

2. The Er-based high-energy 2940 nm pulsed disk laser according to claim 1, characterized in that: A heat sink (6) is provided on the back side of the disc crystal (3).

3. The Er-based high-energy 2940 nm pulsed disk laser according to claim 2, characterized in that: The front side of the disk crystal (3) is coated with an anti-reflection film, and the rear side is coated with a reflective film, the anti-reflection film is used to increase the transmittance of the pump light, and the reflective film is used to increase the reflectance of the remaining pump light.

4. The Er-based high-energy 2940 nm pulsed disk laser according to claim 3, characterized in that: The thickness of the disc crystal (3) is 50-200 um.

5. The Er-based high-energy 2940 nm pulsed disk laser according to claim 1, characterized in that: Each of the prism groups (7) comprises two prisms, the two prisms are symmetrically arranged relative to a horizontal plane, and the two prisms are perpendicular to each other.

6. The Er-based high-energy 2940 nm pulsed disk laser according to claim 1, characterized in that: The number of the prism groups (7) is at least five.

7. The Er-based high-energy 2940 nm pulsed disk laser according to claim 1, characterized in that: The collimating and homogenizing system (2) comprises a homogenizing rod (21) and a collimating lens (22) which are sequentially arranged along the optical path.

8. The Er-based high-energy 2940 nm pulsed disk laser according to claim 1, characterized in that: The resonant cavity (5) is provided with a Q-switching switch (9), an FP standard tool (10), a reflector (11) and an output coupling mirror (12), wherein the Q-switching switch (9), the FP standard tool (10) and the reflector (11) are arranged in sequence along the optical path, and the output coupling mirror OC (12) is arranged at the laser output port of the resonant cavity (5) for laser pulse output.

9. The Er-based high-energy 2940 nm pulsed disk laser according to claim 1, characterized in that: The resonant cavity (5) corresponds to the central through hole of the plano-concave aspheric reflector (8).

10. The Er-based high-energy 2940 nm pulsed disk laser according to claim 1, characterized in that: The pump source (1) uses a diode with a wavelength of 970±10 nm.

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