Saturation characteristics of [Cr.sub.4+]:YAG crystals and dye films for passive Q switches

Measurements of the saturated transmission and the undepleted ground-state population density of both [Cr.sup.4+]:YAG crystals and dye films as saturable absorbers have been experimentally attempted to understand the additional unsaturated losses in a high Q state. The saturated transmission of a saturable absorber is less than its maximum at a high saturation fluence because of the undepleted ground-state population density. Higher saturated transmission and lower undepleted ground-state population density have been observed for [Cr.sup.4+]:YAG crystals than have been observed for dye films at high optical densities. OCIS codes: 140.0140, 140.3540, 140.3580.