Model for a hybrid CO2 laser with two rotational lines and additional amplification in 'hot zones'

A model is described for a two-rotational-level hybrid CO2 laser containing two amplifying cells at high and low pressure in a single resonator. The model leads to a system of rate equations for the populations of the molecular vibrational levels (assuming weak excitation) and treats the coupling between the symmetric and deformation vibrational modes of CO2 molecules in detail. The overlapping of the R23(01/1/1-11/1/0) and P20(00/0/1-10/0/0) line contours is also treated (this overlap is responsible for the anomalously high gain for the P20 line). The model satisfactorily describes the experimentally observed behavior of the radiation pulse, in which the P20 line dominates the initial laser line (determined by the low-pressure cell) during the latter part of the laser pulse.