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

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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.