为了对激光谐振腔进行优化设计,运用光学传输矩阵理论,借助V型折叠腔激光器的等效简化模型对该激光腔的稳定性进行了研究。分析了腔长、折叠镜焦距、反射镜曲率半径与系统稳定性的关系,得到以失调量为参数的稳区临界曲线方程,实现了三镜折叠腔型CO2斩光盘式调Q脉冲输出激光器的设计。分析结果表明,对于子腔预先给定的参量,只要另一子腔满足适当的失调量,整个谐振腔就是稳定的。任一子腔内有二个稳定区而非以往研究者提出的一个稳定区,可根据需要选取最佳的稳定点。采用失调量而非g因子作为参数,直接给出稳定区范围和失调误差,使用性好。

In order to optimize the design of laser resonant cavity, analytical solutions concerning Gaussian beam were derived in a three-mirror V-folded cavity by using the theory of optical propagation matrix. The cavity stability of the folded cavity laser was investigated with an equivalent simplified model. The influence of resonator parameters, such as folded mirror focus, cavity length and curvature radius, on the stability of Q-switched lasers were studied. The stable region′s boundary curve expression is obtained with the off-focus amount as a design parameter. According to theoretical analysis, a mechanically chopper-typed Q-switched CO2 pulse laser was taken as an application example. It was found that for one resonator with preset parameters, as long as the other resonator chose appropriate off-focus amount, the whole laser folded cavity was stable. Either of the resonator cavities can work with two stable regions, instead of previously supposed one. Appropriate stable position can be selected according to preset conditions. By adopting off-focus amount instead of factor g as the parameter, the stable region boundary and maladjusted error are derived directly, which is simple, straightforward and convenience for application.