Abstract

Optical bistability is a well-known phenomenon in optical systems of many kinds. However observations of intrinsic bistability are rare and have not been reported previously in rare earth systems for nonlinear dynamics due to inter-atom coupling which arises at high impurity concentrations. Typically, nonlinear response by this mechanism is too weak to give rise to sizeable nonlinearities. Here we present observations of cooperative upconversion emission from crystals of Yb³⁺ Cs₃Y₂Br₄ at low temperatures however, in which hysteresis without mirrors provides evidence of strong cooperative nonlinear response.

© 1994 Optical Society of America