Switch-power Drift and Pre-damage Effects in Optically Bistable ZnSe Nonlinear Interference Filters

Abstract

Drift of the input power levels at which optically-bistable nonlinear interference filters switch between their transmission states has been studied experimentally. In addition to the small initial drift already observed by various groups, we have monitored, and characterised, a slower irreversible drift associated with the high internal operating irradiances. This pre-damage effect appears to be photo-structural in origin. The results show a small increase in refractive index (∼0·35%) and a decrease in the absorption coefficient (∼20%) over periods ranging from a few minutes to approximately one hour, depending on operating conditions. We have shown that the drift rate can be minimized by going to thicker spacer devices and by using molecular beam deposition techniques to grow the multilayer structures in place of conventional thermal evaporation.