增益介质中发散光束的小尺度自聚焦  

Small-Scale Self-Focusing of Divergent Beams in Gain Medium

作　　者：张艳丽[1] 李小燕[1] 朱健强[1] 

机构地区：[1]中国科学院上海光学精密机械研究所高功率激光物理联合实验室,上海201800

出　　处：《光学学报》2009年第3期786-793,共8页Acta Optica Sinica

摘　　要：将Bepalov-Talanov理论拓展为发散光束在增益介质中的情形,研究了介质小信号增益和饱和增益情况下小尺度扰动的自聚焦特性。在小信号增益情形下,对于确定的输入功率,不同的光束初始曲率半径,小尺度调制增长的临界频率、最快增长频率及其对应的最大增益随介质小信号增益或传输距离的变化有不同的变化性质。光束初始曲率半径表征着光束衍射发散的程度,它的减小在一定程度上能够使小尺度调制的最快增长频率和最大增益减小。小信号增益情形下,对于确定的输出功率,增加介质小信号增益,扰动的最大增益会随之减小,而最快增长频率相应向低频方向移动。相比于小信号增益情形,饱和增益介质情形下小尺度调制增长的最快增长频率及最大增益较小。在不同的系统设计中,需权衡放大器增益及光束参数,选择合适的系统参数及光束控制装置进行实际应用。Bespalov-Talanov theory is extended to the divergent beam in gain medium. The small-scale self-focusing properties are studied systematically in small-signal and saturated gain conditions. In the case of small-signal gain, for a given input power with different initial radiuses, the cutoff spatial frequency, the fastest growing frequency and the maximum growth of small-scale modulation, evolve differently with the change of the small-signal gain and propagation distance. The initial radius represents the degree of diffraction divergence, the decrease of the initial radius can reduce the fastest growing frequency and the maximum perturbation growth. For a given output power, the increase of the small-signal gain can decrease the maximum perturbation growth, while the fastest growing frequency shifts to the lower frequency. Compared with the small-signal gain, the fastest growing frequency and the maximum gain are smaller in medium with saturated gain. In different system design, the amplifier gain and the beam parameters should be weighed and selected properly in practical systems.

关 键 词：非线性光学 小尺度自聚焦 介质小信号增益 饱和增益 小尺度调制增长率 

分 类 号：O436.3[机械工程—光学工程]