掠入射板条放大器激光介质热效应研究

发布时间：2018-07-04 13:07

本文选题：掠入射板条放大器 + 热效应　；参考：《北京工业大学》2015年硕士论文

【摘要】：随着半导体泵浦全固态激光技术的迅速发展,特别是半导体泵浦的板条激光器的发展,使得固体激光器的输出功率得到了进一步的提高,光束质量也有了很大的改善。由于LD抽运板条固体激光器具有结构紧凑、效率高、光束质量好等优点,在工业领域中的应用前景非常广阔,是目前激光领域的研究热点。但是随着泵浦功率的提高,激光介质的热效应成为制约高输出功率、高光束质量的重要因素,因此研究激光器中激光介质的热效应具有非常重要的理论意义和实际参考价值。本文针对本课题采用的掠入射级联放大系统,对掠入射板条放大器激光介质的热效应进行了详尽地、系统地理论分析和数值模拟。主要内容有:(1)分析板条放大器国内外的发展现状,可知激光介质热效应限制着板条放大器的发展。针对掠入射板条激光器,分析了热光效应、弹光效应和热致双折射效应;在考虑端面形变和抽运面形变的情况下,建立了相应的热力学模型,对温度场分布、应力场的分布、热致波前畸变和热透镜效应的理论计算进行了详细地公式推导和分析。(2)数值模拟了掠入射板条放大器中激光介质的热效应。采用COMSOL以及MATLAB软件,模拟了不同泵浦功率、板条厚度、泵浦光斑尺寸条件下的温度场分布;计算了特定条件下的应力场分布;分析了不同泵浦功率、板条厚度、泵浦光斑尺寸以及种子光入射角对热致波前畸变和热透镜效应的影响,并且进行了相应的测量验证,为级联放大系统不同级之间的匹配提供了依据。(3)提出了一种能够降低掠入射板条放大器热效应的新型复合结构(在抽运面上键合未掺杂晶体),并针对该结构建立了相应的热力学模型。模拟了该复合结构的温度场、应力及应变,并且和未键合的单一晶体结构进行对比;研究了不同厚度键合层对复合结构激光介质中温度场分布、介质形变、热致波前畸变以及热透镜效应的影响。模拟结果表明,通过在抽运面上键合非掺杂晶体可以有效地减弱掠入射板条放大器激光介质中的热效应。通过对掠入射板条放大器的激光介质热效应的理论分析和数值模拟让我们认识到了热效应的严重性以及急需解决的迫切性,同时使我们深刻的认识到了产生热效应的原因。这些分析和模拟计算的结果,对于预判光束热效应的强弱、减弱或者消除热效应,改善掠入射板条放大器光束质量、提高输出功率提供了参考依据。
[Abstract]:With the rapid development of semiconductor pumped all-solid-state laser technology, especially the development of semiconductor pumped slab laser, the output power of solid-state laser has been further improved, and the beam quality has been greatly improved. Because of the advantages of compact structure, high efficiency, good beam quality and so on, LD pumped slab solid-state lasers have a very broad application prospect in the industrial field, which is the research hotspot in the laser field at present. However, with the increase of pump power, the thermal effect of laser medium becomes an important factor that restricts the high output power and high beam quality. Therefore, the study of the thermal effect of laser medium in laser has very important theoretical significance and practical reference value. In this paper, the thermal effect of the laser medium of the grazing incident slab amplifier is analyzed and numerically simulated in detail. The main contents are as follows: (1) the development of slab amplifier at home and abroad is analyzed. It is known that the thermal effect of laser medium limits the development of strip amplifier. The thermo-optical effect, elastic-optical effect and thermally induced birefringence effect are analyzed for the grazing incident slab laser, and the corresponding thermodynamic model is established considering the end surface deformation and pump surface deformation, and the distribution of temperature field and stress field is obtained. The theoretical calculation of thermal wavefront distortion and thermal lens effect is derived and analyzed in detail. (2) the thermal effect of laser medium in grazing incident slab amplifier is numerically simulated. By using COMSOL and MATLAB software, the temperature field distribution under different pump power, slab thickness and pump spot size is simulated, the stress field distribution under specific conditions is calculated, and the different pump power and slab thickness are analyzed. The effects of pump spot size and incident angle of seed light on thermal wavefront distortion and thermal lens effect are verified. It provides a basis for matching between different stages of cascade amplification system. (3) A novel composite structure (bonding undoped crystal on pump surface) is proposed, which can reduce thermal effect of grazing incident slab amplifier. The corresponding thermodynamic model is given. The temperature field, stress and strain of the composite structure are simulated and compared with the unbonded single crystal structure. The influence of thermal wave front distortion and thermal lens effect. The simulation results show that the thermal effect in the laser medium of the grazing incident slab amplifier can be effectively reduced by bonding the undoped crystal on the pump surface. Through the theoretical analysis and numerical simulation of the thermal effect in the laser medium of the grazing incident slab amplifier, we realize the seriousness of the thermal effect and the urgency to be solved. At the same time, we have a deep understanding of the cause of the thermal effect. The results of these analyses and simulations provide a reference basis for predicting the intensity of the thermal effect, weakening or eliminating the thermal effect, improving the beam quality of the grazing incident slab amplifier and increasing the output power.
【学位授予单位】：北京工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN248

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