Chaotic and periodic passiveQswitching in coupledCO2lasers with a saturable absorber

Two ${\mathrm{CO}}_2$ lasers with ${\mathrm{SF}}_6$ as an intracavity saturable absorber were optically coupled, and their passive Q-switching dynamics were investigated. The amount of coupling used induced transitions from two unsynchronized periodic oscillating lasers into two synchronized chaotic ones. Conversely, the uncoupled lasers set in the chaotic regime could be made synchronized with a periodic pulsation after their coupling. Numerical solutions for the laser equations agree with the observations.