Abstract

Following a brief review of laser frequency and time domain techniques for overcoming inhomogeneous broadening of optical transitions in solids, recent studies on the failure of the optical Bloch equations (OBE) in describing saturation and coherent transient phenomena in ruby will be discussed. Experiments using free induction decay (FID), as in the original work on the system Pr³⁺:LaF₃ by DeVoe and Brewer¹, as well as extensions to rotary echos² and hole-burning³ will be described. At low fields (~ 0.4 T), the time and frequency domain linewidth variation with Rabi frequency agree provided care is taken to avoid line broadening caused by spectral diffusion⁴. Recent work at high fields (~ 5 T), where Cr-Cr electron spin flipping is suppressed⁵, shows that spectral diffusion decreases and the dephasing time increases. Observed frequency domain hole widths as narrow as 18 kHz (FWHM) have been obtained for the ⁴${\text{A}}_2(-1/2)\to \overline{\text{E}}(-1/2)$ optical transition in dilute ruby using a pump-probe technique⁴. Work with such narrow holes emphasizes the fundamental limits imposed by the uncertainty principle and as an aside, a thought experiment where single photons are transmitted through "frequency slits" will be discussed.

© 1992 Optical Society of America