Abstract
The optical Bloch equations which incorporate the phenomenological population and dipole dephasing times have been tested recently by optical free-induction-decay (FID) measurements on an impurity-ion crystal : at 1.6 K. At low optical fields, the observed optical linewidth is dominated by magnetic fluctuations arising from pairs of fluorine nuclear flip-flops where the condition prevails. At elevated fields, this nuclear broadening mechanism is quenched and the Bloch equations are violated with . In this paper, a microscopic theory appropriate for a low-temperature impurity solid is presented which reveals the above features both for optical and radio frequencies, and a simple physical interpretation of this line narrowing phenomenon is given. Modified Bloch equations of a novel form are derived to second order and yield analytic FID solutions over the entire range of optical-field strength. A discussion of the earlier NMR theories is given, pointing out similarities and differences.
- Received 13 March 1984
DOI:https://doi.org/10.1103/PhysRevA.30.325
©1984 American Physical Society