Instability and chaos in two-mode oscillation of aCO2laser modulated by a saturable absorber

Abstract
Two-mode instability in a CO2 laser with a saturable absorber is investigated both experimentally and theoretically. A strong correlation is found between the mode competition and the passive Q-switching behavior. The observed two-mode instability is nicely reproduced by our rate-equation model in which the vibrational relaxation processes and the spatial mode coupling are considered. Furthermore, numerical calculation predicts existence of chaos in the two-mode oscillation with a higher fractal dimension than the single-mode chaos.