Dynamics of the optically pumped midinfrared NH3laser at high pump power - Part I: Inversion gain

A simple rate-equation model is shown to account for all the major features of gain dynamics in pulsed NH
3
lasers operating with buffer gases. The model is validated by a detailed comparison to measured gain coefficients for two different pumping transitions, and accurately predicts gain distributions as a function of rotational quantum number. The two major concepts embodied in the model are the assumption of rapid thermalization of the rotational populations and the absence of vibrational energy transfer between ortho-NH
3
and para-NH
3
. The parameters which determine the effectiveness of buffer gases are also identified. N
2
and Ar are particularly effective buffer gases and He is much less effective.