双调Q复合腔Nd∶YAG-Cr^(4+)∶YAG激光器的研究

Investigation on a Compound Resonator Nd∶YAG-Cr^(4+)∶YAG Laser with Dual Q-Switching Operation

报道一种有实用价值的、构思新颖的双调Q ,双波长输出的Nd∶YAG Cr4+∶YAG激光器。在由两个平凹腔耦合而成的复合腔中 ,Cr4+∶YAG晶体既作为可饱和吸收体对Nd∶YAG发射的 1 0 6 μm激光被动调Q ,又作为增益介质在 1 0 6 μm激光脉冲作用下发射中心波长 1 4 4 μm的激光脉冲。该激光器实现了 1 0 6 μm激光被动调Q和 1 4 4 μm激光增益调Q的双波长激光振荡 ,输出的 1 0 6 μm和 1 4 4 μm激光脉冲的能量和脉冲宽度分别为 18mJ,5 2ns和0 2 5mJ,19ns ;后者的脉冲宽度约为前者的三分之一。理论上 ,根据Cr4+∶YAG的能级结构和复合腔特点 ,分析了双调Q的工作机理 ;从速率方程出发导出双调Q复合腔激光器输出的 1 4 4 μm激光脉冲宽度和腔内 1 0 6 μm激光功率的关系。 1 4 4 μm激光脉冲时间宽度的理论计算值 ( 2 1 7ns)与实验结果 ( 19ns)基本相符。

A pratical and novel Nd∶YAG Cr 4+ ∶YAG laser with dual Q switching and dual wavelength output is reported. In the compound resonator couplied with two plano concave cavities, a single Cr 4+ ∶YAG is both a saturable absorber of Q switch at 1 06 μm laser from Nd∶YAG and a laser gain medium at 1 44 μm with 1 06 μm laser as its intra cavity pump source. the dual wavelength laser oscillation with passively Q switched 1 06 μm laser and gain switched 1 44 μm laser is realized in the laser. The output energy and pulse duration of 1 06 μm and 1 44 μm laser are 18 mJ, 52 ns and 0.2 mJ, 19 ns respectively, and the pulse duration of the latter is about one of third of the former. The working mechanism of the dual Q switching is analyzed in theory according to energy levels of the Cr 4+ ∶YAG and the feature of the compound resonator. Based on the rate equations, the relationship between pulse duration of 1 44 μm laser and the intra cavity power of 1 06 μm laser is derived. The theoretical data (21.7 ns) of pulse duration of 1 44 μm laser is roughly consistent with the experimental resultt (19 ns).