【作者】 王明哲；

【导师】 谭吉春； 李明中；

【作者基本信息】 国防科学技术大学 ， 光学工程， 2006， 硕士

【摘要】 二极管泵浦固体激光器(DPSSL)相对于传统的灯泵浦固体激光器已大大降低了热效应,但是随着泵浦光功率的进一步提高,激光介质的热效应仍是限制DPSSL向高功率高光束质量发展的重要因素。本论文采用有限元数值模拟和实验观测相结合的方法,研究了重复频率和热容模式二极管泵浦固体激光器的热效应问题,其中对于重复频率DPSSL分为端面泵浦和侧面泵浦两种泵浦方式,进行了重点研究。主要研究结果如下:1.对于激光二极管阵列(LDA)重复频率端面泵浦的大口径Nd:YLF片状放大器,介质的温升和最大热应力与泵浦功率基本呈线性关系,有效泵浦功率密度达到10 kW/cm2时,普通冷却条件下介质可能发生热致断裂;对于相同输出功率的二极管阵列,耦合后能量在空间上呈超高斯分布时热效应最小。2.在重复频率DPSSL中,重复频率的增加将明显增加介质的温升和热应力等热效应;而增大表面的强迫对流换热系数,将会降低介质的最高温升,但最大热应力不一定降低,单纯增加表面换热能力不能保证介质安全工作。结论得到了实验验证。3.对于环形LDA泵浦棒状放大器,以泵浦阵列半径为出发点,讨论一定增益下最高效泵浦效率方案的设计。研究表明,对于相同的增益指标,介质直径越小,所需泵浦功率和热效应也越小。4.热容模式下的LD泵浦固体激光器虽然克服了重复频率DPSSL表面冷却带来的一些热问题,但由泵浦不均匀性引发的一系列热效应不能忽略,对输出功率和光束质量都产生了一定影响。本文的研究结果,对于高功率LD泵浦固体激光器的设计和运行具有一定的参考意义。更多还原

【Abstract】 Compared with traditional solid-state lasers pumped by flash lamps, diode pumped solid-state laser (abbreviated to DPSSL) has lower thermal effect. But, to a certain extent, thermal effects still restrict the DPSSL from giving out a high power and high energy output as desired. In this dissertation, thermal effects of repeated-pulse solid-state laser and heat capacity laser, especially end-pumped and side-pumped repeated-pulse laser, have been analyzed by finite element method and IR camera. The main results obtained in the dissertation can be summarized as follows:Firstly, a finite element thermal model of repeated pulse LDA (Laser Diode Array) end-pumped laser crystal Nd:YLF is established. 3D and transient distributions of temperature and thermal stress in laser crystal were calculated. The results show that the maximal temperature and thermal stress increase with pump power linearly, and fracture due to thermal stress may occur when effective pump energy up to 10 kW/cm2; the thermal effect of crystal under Super-Gaussian transverse distribution is the weakest when pumped by same power.Secondly, in end-pumped repeated pulse laser, thermal effects rise definitely when the frequency increases. When the heat transfer coefficient increase, the maximal temperature will decrease, but the maximal thermal stress may not decrease, the crystal can’t work safely only by the increase of heat transfer coefficient. Some of the conclusions have been verified by experiment.Thirdly, pump efficiency and thermal effect in ring-LDA pulse-side-pumped Nd:glass laser have been studied. When designing a pump structure of specified gain amplifier, we start with LDA ring radius, and the highest pump efficiency can be achieved. Based on the same gain coefficient, the smaller glass radius is, the lower pump power needed and the lower thermal effects are.Finally, although LDA pumped heat capacity laser has partially eliminate the thermal effect of high average power laser, thermal effect due to the non-uniform pump can not be neglected. By means of 3D heat transfer codes and experimental measurement, the temperature and thermal stress distribution have been researched.The conclusions in this dissertation can be used to optimize and operate the high power DPSSL.更多还原