Experimental test of the optical Bloch equations for solids using free-induction decay

Abstract

Recent studies by DeVoe and Brewer [Phys. Rev. Lett. 50, 1269 (1983)] have shown that the conventional optical Bloch equations markedly fail to describe the optical saturation behavior of the $D_1$ line in the solid ${\mathrm{Pr}}^{3+}$:${\mathrm{LaF}}_3$. In this paper we extend these studies to another solid, ruby, using free-induction-decay observations obtained by pulse excitation of the $R_1$ line at 693.4 nm with an ultranarrow-linewidth dye laser. Comparison of the results with Gauss-Markov and random-telegraph-dephasing theories shows approximate agreement for a fluctuation correlation time ${\tau }_c$=$T_2$, the dephasing time. This result is remarkably similar to that obtained for ${\mathrm{Pr}}^{3+}$:${\mathrm{LaF}}_3$. However, for theoretical and experimental reasons, we conclude that the theories do not consistently explain the current as well as other data. A qualitative discussion of another dephasing model is given.