Modified optical Bloch equations for solids.

Abstract

In a recent experiment of DeVoe and Brewer [1], it was concluded that the optical Bloch equations are incapable of describing the saturation phenomena observed. Optical free induction decay (FID) measurements of the impurity ion crystal Pr3+:LaF3 were conducted where the Pr3+ ions are coherently prepared by a laser field under steady-state conditions and then freely precess when the driving field is removed. At low optical fields, the observed Pr3+ optical linewidth is dominated by magnetic fluctuations arising from pairs of fluorine nuclear flip-flops. At high optical fields, this nuclear broadening mechanism is quenched and the Bloch equations are seriously violated. On physical grounds, this failure is due to a time-averaging of the magnetic interaction as the optical nutation frequency increases [2]. The phenomenological dipole dephasing time T2 of the Bloch equations is therefore not a true constant but lengthens with increasing field strength.