TIME-DEPENDENT PROCESSES IN CO2 LASER AMPLIFIERS

Measurements have been made of the small signal gain of CO 2-N2-He laser amplifiers excited either by short pulses or a 50 Hz rectified a.c. waveform. A model, based on the known vibrational energy-level scheme appropriate to this laser, is developed and applied to the data. The relaxation times of the upper and terminal laser states, the relaxation rate of the first vibrational state of nitrogen and the nitrogen to carbon dioxide energy transfer rate are determined. Gas heating which limits laser gain is described in terms of a phenomenological thermal time constant, and the value of this quantity is deduced from the a.c. data under various conditions. The data presented permits the excitation conditions for optimum amplification of pulses from a Q-switched oscillator to be determined under non-saturating conditions.