Tests of the Optical Bloch Equations for Solids

Abstract

An optical coherence phenomenon–power- dependent optical line narrowing—is reported for the first known time. The effect is observed in a low-temperature impurity- ion solid, Pr3+:LaF3, using a coherent transient technique for which saturation conditions prevail. Current theories of saturation, based on the optical Bloch equations or on rate equations, fail to explain our experimental results. We have therefore developed a microscopic coherence theory that introduces dephasing into the density-matrix equations of motion in a manner equally valid at low and high power and that agrees closely with our experimental results. This work thus represents the first reported observation of the failure of the optical Bloch equations in a low-temperature impurity-ion solid. © 1984 Optical Society of America