Mode-medium instability in pulsed CO2 lasers

Evidence of mode-medium instability in a pulsed CO2 laser is presented. The evidence is based on recent experimental observations of focusability loss due to initial inhomogeneities in a pulsed CO2 laser operating in the 10.6-micron wavelength. The pumping energy for the CO2 laser was provided by an electron-beam-sustained discharge. A theoretical model is developed to explain the far-field energy loss characteristics of the CO2 laser in terms of perturbations in gain, density, and intensity. The theoretical predictions are found to be in good agreement with the experimental results. The far-field and near-field energy distributions before lasing at a total laser gas pressure of 1 atm are given in a series of graphs.