Irradiation-induced switch power drift in optically bistable nonlinear interference filters at 514 and 830 nm

Light-induced changes in the switch power of optically bistable ZnSe nonlinear interference filters have been studied experimentally at 514 and 830 nm wavelengths. This drift was found to be mainly caused by an irreversible change in the peak wavelength and transmission of the filter and is associated with high internal operating irradiances. These changes are apparently due to photostructural modifications of the material forming the central spacer layer. The drift was shown to be dependent on the spacer thickness, incident spot size and the deposition technique used to grow the filter structures. The rate of switch power drift was also found to be reduced considerably when using an illuminating wavelength well removed from the band edge of the spacer material, e.g., 830 nm.