【作者】 张申金；

【导师】 冯国英；

【作者基本信息】 四川大学 ， 光学， 2004， 硕士

【摘要】 采用激光二极管阵列(LDA)代替氙光灯作为抽运源的激光二极管抽运固体激光器(DPSSL)以其转换效率高、稳定性好、体积小、光束质量高、重复频率高、寿命长和全固态等优点，已成为新型激光器的发展热点，而且它还可以克服以氙光灯作为抽运源时带来的热效应等副作用。Nd：YLF晶体有较长的荧光寿命及自然双折射特性，用功率受限型抽运源LD进行抽运，可充分发挥激光二极管的潜力。 本文从理论及实验上分析研究了高功率LDA侧面抽运Nd：YLF激光放大器的放大特性，所做得主要内容包括： 1、从交叠积分及输运方程出发，对激光放大器的放大特性进行了理论分析，对激光放大器的增益特性、能量转换效率特性及能量输出特性进行了相关的理论研究及计算模拟。 2、设计、制造并成功运行了高功率LDA侧面抽运棒状Nd：YLF的激光放大器及一套两级双程离轴放大系统。实验中对LDA及Nd：YLF棒进行了有效的温度控制，同时采取了精确的延时措施，提高了激光放大器的转换效率和稳定性。实验得到了激光放大器及放大系统的增益特性、输出能量特性及能量提取效率特性与放大器LDA的抽运电流、放大脉冲与放大器LDA抽运电流之间的延时及注入能量之间的关系。实验结果表明：采用侧面直接抽运耦合系统的激光放大器有均匀的抽运光分布场和增益分布场。注入能量为20μJ时，两个激光放大器的双程离轴小信号增益为5.35和5.25；在5mm×5mm软光阑处注入能量为27四川大学硕士学位论文pJ时，放大系统小信号净增益近600倍，输出能量为5.7mJ，能量提取效率为0.86%;注入1.58mJ能量时，放大系统输出能量为129.ZmJ，能量提取效率达到19.5%，实验结果与理论分析和模拟结果基本一致。 3、采用光线追迹和有限元方法，对高功率LDA重复脉冲侧面抽运Nd:YAG激光放大器中棒的瞬态温度分布进行了详细的计算模拟，分析比较了不同抽运阶段、抽运频率及占空比的情况下，棒内的瞬态温度分布。模拟结果表明:高功率LDA侧面重复脉冲抽运时，棒内温度随抽运频率和占空比的增大而增大，棒横截面内圆心处温度随时间变化成锯齿形分布，最后温度随时间成周期性变化。 4、注入光源采用高功率LDA侧面抽运棒状Nd:YLF的电光调Q振荡器，振荡器使用设计新颖的双台阶Q开关驱动器及低压KTP晶体作为电光调Q开关。实验结果表明:电光调Q振荡器输出激光脉冲时间抖动小于4ns，脉冲宽度小于6.7ns，输出能量可达1.16mJ，单纵模几率为100%，单脉冲能量稳定度为3%，脉宽稳定度为4%。 本文对高功率LDA侧面直接抽运Nd:YLF激光放大器及放大系统进行了详细的理论分析及实验研究。其结论可为设计、研制及优化高功率LDA侧面直接抽运固体激光放大器提供参考。 关键词:高功率LDA侧面抽运两级双程离轴放大增益第2页共4页更多还原

【Abstract】 Because of the advantages of high energy conversion efficiency, high stability, small size, high quality, high repeated frequency, long fluorescence life, all-solid-state et al, the diode pumped solid-state laser (DPSSL) has been the development hotspot of new kind of laser. By using laser diode array (LDA) to replace Xe lamp to pump medium, DPSSL can also overcome the serious thermal effects and other side-effect of Xe lamp. Nd:YLF crystal has longer fluorescence life and natural birefeingent, and can exert the potential of power-restricted LD.Here the basic amplifing characters of Nd:YLF laser amplifier side-pumped by high power laser diode array are analyzed and researched based on theory and experiment. The main content is the following:1 By using Overlap Integral and covey equations, the amplifing characters of laser amplifier are analyzed. The characters of gain, energy conversion efficiency, and output energy are studied based on theory and simulation in detail.2 A Nd:YLF laser amplifier and a suit of two-stage double-pass off-axis amplifying system are designed, made, and operated successfully. The laser amplifier is side-pumped by high power laser diode array. The temperatures of laser diode array and Nd:YLF rod are controlled effectively and the accurate delay is adopted. Such measures increase the energy conversion efficiency and stability of amplifier. The relations of gain, energy conversion efficiency, output energy and pump current, delay between amplifying pulse and current of amplifier, input energyare received based on experiment.The results of experiment indicate: the laser amplifier with side-directly-pumped coupling system has uniform pump light distribution and gain distribution. As input energy is 20 J, the gains of two amplifiers are 5.35 and 5.25. As input energy is 27 J after the 5mm 5mm soft diaphragm, the two- stage double-pass off-abaxial small-signal net gain of amplifying system is 600, output energy is 5.7mJ, and energy extract efficiency is 0.86%. As input energy is 1.58mJ,the output energy of amplifying system is 129.2mJ, and the energy extract efficiency is 19.5%.3 The transient temperature distribution in the Nd:YAG laser rod repeating pulse-pumped by high power ring-LD array is simulated in detail by using ray tracing method and finite element method. The transient temperature distributions at different pump periods, pump frequencies and pump widths are analyzed and compared. The result indicats that when high power ring-LDA pumps repeatly, the core temperature of the rod has sawtoothed distribution, and the temperature of the rod rises as the pump frequency or pump width rises. At last the temperature has periodical distribution with time.4 A electro-optics Q-switch oscillator side-pumped by high power laser diode array is adopted to produce amplifying pulse. The oscillator has original double-step Q switch driver and low-voltage KTP crystal as the electro-optics switch. The results of experiment indicate that: The time dither of output pulse of electro-optics Q-switch oscillator is less than 4 ns, pulse width is less than 6.7ns, output energy is 1.16mJ, single-longitudinal mode probability is 100%, energy stability of single pulse is 3%, and stability of pulse width is 4%.The amplifying characters of a Nd:YLF laser amplifier side-pumped by high power laser diode array are analyzed and researched in detail based on theory and experiment. The results can offer references to design, develop, and optimize solid-state laser amplifier side-directly-pumped by high power laser diode array.更多还原