A Xenon Lamp Pumped Solid-State Laser Based on a Highly Refractive Index Matched Gain Medium

Abstract

A xenon lamp pumped solid laser based on a gain medium with a high refractive index matching includes a xenon lamp pumping system and a resonant cavity, wherein the resonant cavity includes an input mirror, an output mirror and an end-pumped gain medium, wherein the gain medium is a gradient-doped transparent ceramic rod prepared by a gel injection molding method, wherein the core is a YAG ceramic co-doped with Cr and Nd ions, and the outer layer is a YAG ceramic doped with any rare earth ion of Lu, Gd, and Te, which are staggered one by one in an N+1 manner; a laser converging device converges the pumping light output by the xenon lamp pumped laser and then incidents it to the input mirror, and the transmitted pumping light is incident to the gain medium from the end face, and the gain medium generates laser through stimulated radiation, and the generated laser oscillates in the resonant cavity and is finally output from the output mirror. The present invention uses gradient-doped transparent ceramics, and through doping and matching of rare earth ions of different concentrations, while achieving theoretical transmittance, solves the thermal effect problem caused by different refractive indices, effectively improves beam quality, and realizes mode control.

Description

Technical Field

[0001] The invention relates to the field of solid lasers, and in particular to a xenon lamp pumped solid laser based on a gain medium with a high refractive index match. Background Art

[0002] Sunlight is a continuous wide-spectrum light source, and its radiation spectrum contains many commonly used laser pumping absorption bands. Focused high-energy-density sunlight is coupled into the laser medium, and the laser medium is pumped to achieve laser output. This type of laser is called a solar-pumped laser, which has potential application prospects in satellite laser communications, wireless transmission of space energy, and space laser weapons. At present, there are three main types of lasers that directly use sunlight as a pump source: solar-pumped gas lasers, solar-pumped solid-state lasers, and solar-pumped fiber lasers. The gain medium used in solar-pumped solid-state lasers is solid materials such as crystals and ceramics. The convergence system has developed from a single imaging optical device to a combination of imaging and non-imaging devices, and has a certain practical application capability.

[0003] Due to the influence of weather, a xenon lamp pumping system with the same spectrum width can be used to simulate sunlight testing during the experiment. Therefore, the design of a xenon lamp focusing system with convenient operation is particularly important.

[0004] The gain medium is the core of the solid-state laser, which determines the laser output wavelength and light conversion efficiency. As mentioned earlier, the energy of sunlight is mainly concentrated in the visible light band. Only when the gain medium satisfies the high matching degree, high absorption and high conversion efficiency of visible light at the same time can the pumping efficiency be fully improved and high-quality sunlight-pumped solid-state laser output be achieved. Therefore, the selection and development of gain media suitable for sunlight-directly pumped solid-state lasers is particularly critical. In sunlight-directly pumped solid-state lasers, glass and glass optical fiber, single crystal and ceramics are currently the most commonly used gain media.

[0005] As a new generation of solid gain medium, transparent ceramics can achieve material densification only by high-temperature sintering of raw material powders. The preparation temperature is far lower than the melting point of the material, and the preparation cycle is only one week. At the same time, ceramic materials are easy to achieve high-concentration and uniform ion doping due to their intrinsic characteristics of polycrystalline state. Reference 1 (Yang Liying, Li Jiaqiang, Zhang Jinyu, et al. Thermal effects of semiconductor laser pumped composite crystal solid lasers [J]. Journal of Luminescence, 2017, 38(06): 742-746.) proposed that for solid lasers directly pumped by sunlight, single-structure single crystals or ceramic media are very likely to cause uneven heat distribution during laser operation, resulting in thermal lens effect and reducing laser output performance. Reference 2 (PAVEL N, TSUNEKANE M, TAIRAT. Composite, all-ceramics, high-peak power Nd:YAG / Cr 4+ :YAG monolithic micro-laser with multiple-beam output for engine ignition[J].Opt.Express,2011,19(10):9378-9384.) and Reference 3 (Guo Junhong, Duan Yanmin, Zhang Jing et al. Nd:YAG / Cr 4+ : Study on the output characteristics of Q-switched laser of YAG / YAG bonded crystal [J]. Acta Photonica Sinica, 2018, 47(02): 205-210.) mentioned that the use of composite structure ceramic medium can effectively improve the thermal effect of laser medium during laser operation, thereby achieving stable laser output. In addition, composite structure solid laser materials can achieve multifunctional applications of solid lasers through diversified structural design, and have great development potential. In particular, reference 4 (D. Kracht, R. HuB, R. Wilhelm, J. Neumann, Core-doped ceramic Nd: YAG laser with Sm: YAG cladding, 2007 Conference on Lasers and Electro-Optics, 2007, pp. 1-2) and reference 5 (K. Hasegawa, T. Ichikawa, Y. Takeda, A. Ikesue, H. Ito, T. Motohiro, Lasing characteristics of refractive-index-matched composite Y3Al5O 12rods employing transparent ceramics for solar-pumped lasers, Jap. J. Appl. Phys. 57 (2018), 042701.) proposed that Y3Al5O with a core-cladding structure 12 YAG laser rods show better laser characteristics than uniformly doped rods. Compared with traditional uniformly doped laser rods, core doping and undoped cladding can achieve effective mode control, so that the TEM00 mode is dominant and the beam quality is improved. However, this is under the assumption that the refractive index of the core and cladding matches. In actual situations, there is a large deviation between the refractive index of the core and the cladding. The longer the length, the more likely it is to cause distortion of the beam propagation, and the uneven refractive index easily leads to power degradation. Therefore, improvement is needed. Summary of the invention

[0006] The purpose of the present invention is to provide a xenon lamp pumped solid laser based on a gain medium with a highly matched refractive index, wherein the refractive index of the core and the cladding are highly matched, thereby improving the beam quality.

[0007] To achieve the above-mentioned purpose, the technical scheme adopted by the present invention is as follows: a xenon lamp-pumped solid-state laser based on a gain medium with a high refractive index matching, comprising a xenon lamp pumping system and a resonant cavity, wherein the xenon lamp pumping system is a converging heat dissipation system, comprising a xenon lamp pumping laser and a laser converging device, wherein the laser converging device is provided with a light spot size adjustment device, and the light outlet of the laser converging device is a rotatable converging light outlet, and the resonant cavity is a linear cavity, comprising an input mirror, an output mirror, and an end-face pumped gain medium arranged on the optical path between the input mirror and the output mirror, wherein the gain medium is a gradient-doped transparent ceramic rod prepared by a gel injection molding method, wherein the core is a Cr and Nd ion co-doped YAG ceramic, the outer layer is YAG ceramic doped with any one of Lu, Gd, Te rare earth ions, which are staggered one by one in N+1 manner, the Cr ion doping concentration in the core of the gain medium is 0.05at.%-2.5at.%, the doping concentration ratio of Cr and Nd ions is 0.1-2, and the doping concentration ratio of the outer layer rare earth ions to the core Nd ions is 1-6; the xenon lamp spectrum range is the simulated sunlight spectrum range, the laser focusing device converges the pump light output by the xenon lamp pump laser and then incident on the input mirror, the transmitted pump light is incident on the gain medium from the end face, the gain medium generates laser through stimulated radiation, the generated laser oscillates in the resonant cavity, and finally outputs from the output mirror.

[0008] Preferably, the gain medium has a diameter of 1 mm-20 mm and a length of 5 mm-100 mm.

[0009] Preferably, the spot size adjustment device adjusts the focusing size of the pump light in a range of 0.5 mm to 6 mm, and the adjustment range of the light outlet of the laser focusing device is 0° to 180°.

[0010] Preferably, the input mirror is one of a plane mirror, a plano-convex mirror or a plano-concave mirror, coated with a dielectric film that is highly reflective to pulsed lasers in the required band; the output mirror is one of a plane mirror, a plano-convex mirror or a plano-concave mirror, coated with a dielectric film that is highly reflective to pulsed lasers in the required band, or a dielectric film that is partially reflective and partially transparent to the required pulsed laser band.

[0011] Preferably, the xenon lamp pump system adopts air cooling.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] (1) The pumping system used in the present invention is a sunlight simulation system, namely a xenon lamp converging and cooling system, which can adjust the size and direction of the converging light spot and can also control the size of the converging light spot intensity.

[0014] (2) By using gradient-doped transparent ceramics and doping and matching rare earth ions of different concentrations, the theoretical transmittance can be achieved while solving the thermal effect problem caused by different refractive indices, which can effectively improve the beam quality and realize mode control. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic diagram of an end pump provided by an embodiment of the present invention;

[0016] Figure 2 is a profile diagram of the gradient doping of the gain medium core;

[0017] In the figure, 1 is the core, 2 is the outer layer, 3 is the xenon lamp pump laser, 4 is the laser focusing device, 5 is the spot size adjustment device, 6 is the light outlet, 7 is the resonant cavity, 8 is the input mirror, 9 is the gain medium, and 10 is the output mirror. DETAILED DESCRIPTION

[0018] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] like Figure 1As shown, the present invention provides a xenon lamp pumped solid laser based on a gain medium with a high refractive index matching, comprising a xenon lamp pumping system and a resonant cavity 7. The xenon lamp pumping system is a converging heat dissipation system, comprising a xenon lamp pumped laser 3 and a laser converging device 4. The laser converging device 4 is provided with a spot size adjustment device 5. The light outlet 6 of the laser converging device 4 is a rotatable converging light outlet. The resonant cavity 7 is a linear cavity, comprising an input mirror 8, an output mirror 10, and an end-face pumped gain medium 9 arranged on the optical path between the input mirror 8 and the output mirror 10. The input mirror 8 is one of a plane mirror, a plano-convex mirror or a plano-concave mirror, and is coated with a dielectric film with high reflection to a pulse laser of a required wavelength band. The output mirror 10 is one of a plane mirror, a plano-convex mirror or a plano-concave mirror, and is coated with a high reflection film to a pulse laser of a required wavelength band, or a dielectric film with partial reflection and partial transmission of the required pulse laser wavelength band.

[0020] The xenon lamp pumping system in the present invention is a xenon lamp converging and cooling system, which adopts air cooling. The convergence size of the output light spot is adjustable within a range of 0.5mm-6mm, and the direction of the light outlet 6 of the laser converging device 4 is adjustable within a rotation angle of 0°-180°.

[0021] In the present invention, the spectral range of the xenon lamp simulates the spectral range of sunlight. The laser focusing device 4 focuses the pump light output by the xenon lamp pump laser 3 and then incidents it to the input mirror 8. The transmitted pump light is incident to the gain medium 9 from the end face. The gain medium 9 generates laser through stimulated radiation. The generated laser oscillates in the resonant cavity 7 and is finally output from the output mirror 10.

[0022] Figure 2 The cross-sectional schematic diagram of a gradient doped transparent ceramic rod prepared by gel casting method, the diameter of the gain medium 9 is 1mm-20mm, the length is 5mm-100mm, the gain medium 9 adopts gradient doping, the core 1 is YAG ceramic co-doped with Cr and Nd ions, the outer layer 2 is YAG ceramic single-doped with Lu, Gd, Te rare earth ions, staggered one by one in N+1 manner. The Cr ion concentration is 0.05at.%-2.5at.%, the Cr and Nd ion concentration ratio is 0.1-2, and the outer layer rare earth ion doping concentration ratio to the core Nd ion is 1-6.

[0023] The above xenon lamp pumped solid laser was used to simulate the generation of 1064nm laser:

[0024] Example 1: When the convergent spot size is 0.5 mm, the laser working medium used has a diameter of 1 mm and a length of 5 mm, the core is Cr and Nd ion co-doped YAG ceramic, of which 0.2 at.% Cr ions are doped and 2 at.% Nd ions are doped, and the second layer is Lu ion-doped YAG ceramic, of which 12 at.% Lu ions are doped, the above device is used to generate xenon lamp-pumped 1064 nm laser.

[0025] Example 2: When the convergent spot size is 4 mm, the laser working medium used has a diameter of 10 mm and a length of 50 mm, the core is Cr and Nd ion co-doped YAG ceramic, of which 1 at.% Cr ions are doped and 1.5 at.% Nd ions are doped, and the second layer is Gd ion-doped YAG ceramic, of which 4 at.% Gd ions are doped, the above device is used to generate xenon lamp-pumped 1064 nm laser.

[0026] Example 3: When the convergent spot size is 6 mm, the laser working medium used has a diameter of 20 mm and a length of 100 mm, the core is Cr and Nd ion co-doped YAG ceramic, of which 0.6 at.% Cr ions are doped and 0.6 at.% Nd ions are doped, and the second layer is Te ion-doped YAG ceramic, of which 1.8 at.% Te ions are doped, the above device is used to generate xenon lamp-pumped 1064 nm laser.

[0027] Example 4: When the convergent spot size is 3mm, the laser working medium used has a diameter of 5mm and a length of 8mm, the core is Cr, Nd ion co-doped YAG ceramic, wherein 0.2at.% Cr ions are doped and 2at.% Nd ions are doped, the second layer is Lu ion doped YAG ceramic, wherein 12at.% Lu ions are doped, the third layer is Cr, Nd ion co-doped YAG ceramic, wherein 0.2at.% Cr ions are doped and 2at.% Nd ions are doped, the fourth layer is Lu ion doped YAG ceramic, wherein 12at.% Lu ions are doped, and gradient doping is performed in this way. Using the above device, xenon lamp pumped 1064nm laser is generated.

[0028] Example 5: When the focusing spot size is 6 mm, the diameter of the laser working medium used is 20 mm, the length is 100 mm, the core is Cr, Nd ion co-doped YAG ceramic, wherein 0.6 at.% Cr ion doping, 0.6 at.% Nd ion doping, the second layer is Te ion doped YAG ceramic, wherein 1.8 at.% Te ion doping, the third layer is Cr, Nd ion co-doped YAG ceramic, wherein 0.6 at.% Cr ion doping, 0.6 at.% Nd ion doping, the fourth layer is Te ion doping The fifth layer is a Cr, Nd ion co-doped YAG ceramic, in which 1.8at.% Te ions are doped, the fifth layer is a Cr, Nd ion co-doped YAG ceramic, in which 0.6at.% Cr ions are doped and 0.6at.% Nd ions are doped, the sixth layer is a Te ion-doped YAG ceramic, in which 1.8at.% Te ions are doped, and the seventh layer is a Cr, Nd ion co-doped YAG ceramic, in which 0.6at.% Cr ions are doped and 0.6at.% Nd ions are doped. The above device is used to generate a xenon lamp pumped 1064nm laser.

[0029] By comparison, it is found that when the core concentration of the gain medium is different from the ion doping concentration of the second layer (Examples 1-3), the ion ratio in Example 2 is well matched, that is, the refractive index difference between the YAG ceramic doped with 1at.% Cr ions and 1.5at.% Nd ions and the YAG ceramic doped with 4at.% Gd ions is close to or equal to 0, and the refractive distortion is very small. It can achieve a good refractive index match when the light beam passes through the material under the premise of achieving the theoretical transmittance, and the laser effect is the best; but when the gradient doping concentration is the same during the preparation process (Examples 4 and 5), the more layers there are, the less the refractive index matching can achieve a beneficial effect. Therefore, two-layer doping is better than multi-layer doping, and the thermal effect of the material is significantly improved.

Claims

1. A xenon lamp-pumped solid-state laser based on a highly refractive index-matched gain medium, comprising a xenon lamp pumping system and a resonant cavity (7), characterized in that: The xenon lamp pumping system is a converging heat dissipation system, comprising a xenon lamp pumping laser (3) and a laser converging device (4); the laser converging device (4) is provided with a light spot size adjustment device (5); and the light outlet (6) of the laser converging device (4) is a rotatable converging light outlet; the resonant cavity (7) is a linear cavity, comprising an input mirror (8), an output mirror (10), and an end-face pumped gain medium (9) arranged on the optical path between the input mirror (8) and the output mirror (10); the gain medium (9) is a gradient-doped transparent ceramic rod prepared by a gel injection molding method, wherein the core (1) is a YAG co-doped with Cr and Nd ions. The ceramic has a Cr ion doping concentration of 1 at.%, an Nd ion doping concentration of 1.5 at.%, and an outer layer (2) is a YAG ceramic doped with Gd ions, with a Gd ion doping concentration of 4 at.%. The diameter of the gain medium (9) is 1 mm to 20 mm, and the length is 5 mm to 100 mm. The xenon lamp spectrum range is a simulated sunlight spectrum range. The laser focusing device (4) focuses the pump light output by the xenon lamp pump laser (3) and then incidents it to the input mirror (8). The transmitted pump light is incident on the gain medium (9) from the end face. The gain medium (9) generates laser light through stimulated radiation. The generated laser light oscillates in the resonant cavity (7) and is finally output from the output mirror (10).

2. A xenon lamp-pumped solid-state laser based on a highly refractive index matched gain medium according to claim 1, characterized in that: The light spot size adjustment device (5) adjusts the pump light focusing size in a range of 0.5 mm to 6 mm, and the light outlet (6) of the laser focusing device (4) has an adjustment range of 0 o -180 o .

3. A xenon lamp-pumped solid-state laser based on a highly refractive index matched gain medium according to claim 1, characterized in that: The input mirror (8) is one of a plane mirror, a plano-convex mirror or a plano-concave mirror, coated with a dielectric film that is highly reflective to pulsed lasers in a required wavelength band; the output mirror (10) is one of a plane mirror, a plano-convex mirror or a plano-concave mirror, coated with a dielectric film that is highly reflective to pulsed lasers in a required wavelength band, or a dielectric film that is partially reflective and partially transparent to the required pulsed laser wavelength band.

4. The xenon lamp-pumped solid-state laser based on a highly refractive index matched gain medium according to claim 1, characterized in that: The xenon lamp pump system adopts an air-cooling heat dissipation method.

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