Vacuum-deposited thin-film interferometers as bistable devices operating continuously at room temperature

Nonlinear thin film interferometers as bistable devices have the advantage of operating at room temperature. A prolonged effect of the input light beam on ZnS interferometers does not cause any changes resulting in a decrease in light induced photorefraction, and this bistable element can remain in any of its stable states until the switching signal appears. In nonlinear thin film interference filters with ZnSe and Na3AlF6 spacers, the switching of the input intensity is first followed by a short term (a few seconds) transient after which operation of the bistable device stabilizes. In all the thin film interferometers studied, the beam profile hysteresis and an unusual form of the hysteresis loop with the negative slope of the upper branch for the on axis zone of the input beam were observed. The decrease in the output intensity as the input intensity increases after the bistable device is switched on is likely to be determined by the difference between the stationary spatial profile of the light field distribution inside the interferometer and the temperature distribution profile.