Thin-film ZnSe dielectric interference filters have recently been shown to exhibit optical bistability in conditions of cw laser irradiation. In these filters, absorption in the material produces a temperature rise and in turn a refractive-index change. Typical switching power levels are currently 1-100 mW, mainly due to a restriction on the spacer absorption. There must be sufficient absorption to create the required temperature rise but not so much that the cavity finesse is lost. For many applications of bistability to optical information processing it is important for switching powers to be significantly less than 1 mW. A cavity design which avoids the restriction in spacer absorption by having the absorption in thin metallic mirrors is presented. The heat source still experiences the optical feedback provided by the overall cavity, and thermally dispersive bistability should be obtained. The optical responses of two cavity designs have been demonstrated: (a) metallic mirrors on the front and back face and (b) a dielectric mirror on the front and metallic on the back.
|Publication status||Published - 1987|