Influence of an optical discharge plasma on the stability of a CO2 laser with an unstable resonator

An experimental investigation was made of fluctuations in the output power of a CO₂ laser when laser radiation reflected from a target was returned to the unstable resonator. It was found that a small fraction of the laser radiation (less than 10^–4) reflected by an optical discharge plasma, whose density was much lower than the critical density, led to strong fluctuations (of the order of 100%) in the laser emission. A theoretical model predicting the possibility of the appearance of the experimentally observed fluctuations in the laser emission was proposed.