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将Bespalov Talanov理论推广到介质有增益 (损耗 )的情形 ,揭示了在介质有增益或损耗从而光强随传输距离变化的情况下小尺度自聚焦的特性 .主要是在一定的输入功率下 ,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 (B积分 )均随介质增益或传输距离的增大而增大 ;对于确定的输出功率 ,随介质增益的提高 ,B积分值变小 ,同时最快增长频率向低频方向移动 .利用局部能量守恒定律唯象地研究了增益和损耗对激光束成丝的影响 ,发现增益使成丝距离延长而损耗使成丝距离缩短 .讨论了介质增益和损耗对高功率激光放大器设计的影响 .尽量使激光器在小输入高增益状态下运行 ,可以从某种程度上抑制因小尺度自聚焦而导致的介质破坏效应 .
The Bespalov Talanov theory is generalized to the case of gain (loss) in the medium, which reveals the small-scale self-focusing property when the medium has gain or loss so that the light intensity changes with the transmission distance. It is mainly that under a certain input power, small The critical frequency, the fastest growth rate and the corresponding maximum gain (B integral) of scale modulation increase with the increase of medium gain or transmission distance. For the given output power, with the increase of medium gain, B integral The fastest growing frequency moves to the low frequency.The local energy conservation law is used to study the influence of gain and loss on the laser beam forming process.The results show that the gain can make the distance between the filaments become longer and the loss make the distance between the filaments shorten. The influence of medium gain and loss on the design of high power laser amplifier is studied.As far as possible, the laser can operate under the condition of small input and high gain, which can restrain the medium destruction effect caused by small-scale self-focusing to a certain extent.