Research on Excitation and Relaxation Processes in the Self-Terminating Metal Vapor Laser of Low-Temperature Operation Using a Metal-Vapor-Complex Reaction

弛豫振荡现象在许多激光器中都有观察到，但在气体激光器中并不常见。弛豫振荡通常不会被观察到，因为与固态激光器、半导体激光器和某些其他激光系统相比，大多数气体激光器的上激光能级的衰减速率大，其中激发的粒子数反转的恢复时间基本上长于激光腔衰减时间。然而，在某些情况下，甚至在气体激光器中也可以满足弛豫振荡的条件，因为在金属蒸气激光器中，在510.6nm放电激光输出中，观察到了振荡/非振荡的波形，并讨论了激光上能级的衰减特性。泵浦CuCl蒸气激光器在铜蒸气激光器（CVL）输出中经常观察到谐振腔渡越时间随时间间隔的波动。然而，在我们的实验中观察到的波动不是由于这种效应。根据激光器工作温度的不同，激光器会出现振荡或非振荡现象，本文从CVL理想化三能级系统的速率方程出发，采用以下理论方法分析了这些现象，其中引入了自终止金属蒸气激光器（ST-MVL）的速率方程，讨论了其瞬态特性.解析解的小信号逼近，2。精确解的数值积分（大信号理论），3。大信号近似（小信号近似和大信号理论的结合）的解析解和数值解，这些分析结果很好地解释了实验中CuCl蒸气激光器输出波形的变化。

The phenomenon of relaxation oscillations has been observed in a variety of lasers, although not so frequently in gas lasers. Relaxation oscillations are not generally observed because the decay rate of the upper laser level is large Nh most gas lasers compared to that in solid-state lasers, semiconductor lasers, and certain other laser systems in which the recovery time of the excited population inversion is substantially longer than the laser cavity decay time. However, in certain circumstances the condition for the relaxation oscillation can be satisfied even in gas lasers because in the metal-vapor laser, the decay rate of the upper laser level varies over a wide range through the resonance-radiation trapping effect owing to the resonance transition between the ground and the upper laser level.We observed an oscillatory/nonoscillatory waveform in the 510.6nm laser output of a discharge-pumped CuCl vapor laser. An undulation with a time separation of the resonator transit time is frequently observed in the copper vapor laser (CVL) output. However, the undulation observed in our experimentsis not due to this effect. Either oscillatory or nonoscillatory behavior appeared, depending on the operating temperature of the laser.These behaviors were analyzed based on the rate equations of the idealized 3-level system of the CVL by the following theoretical methods ; where the rate equations for the self-terminating metal vapor laser (ST-MVL) were newly introduced to discuss the transient features.1. analytical solutions by the small-signal approxination, 2. exact solutions by the numerical integration (by the large-signal theory), 3. analytical and numerical solutions of large-signal approximation (the combined method of the small-signal approximation and the large-signal theory).These results of the analysis of 1-3 well explained the waveform variation of the CuCl vapor laser output in the experiments.