Abstract

The prototype situation for both coherent population trapping and electromagnetically induced transparency (BIT) occurs in an ideal three-state atom (Fig. la). But, most often, atoms have additional angular momenta that enlarge the manifold of coupled states. An example of this is ²⁰⁷Pb, where a nuclear spin of I = 1/2 splits the fine structure levels of spinfree ²⁰⁸Pb into their hyperfme components (Fig. 1b). Even though a particular three-state subsystem may be made transparent, other subsystems will produce a prohibitively large change in the complex refractive index, and the medium will be opaque. We show that, to obtain transparency and near unity refractive index, instead of tuning the lasers to a Raman- like subset of the split transitions, one should tune the lasers to the centers of gravity of the splittings that are caused by the spectator momentum. We also report the first demonstration of EIT with pulsed lasers in an optically thick sample of atoms which exhibit hyperfme structure using this approach.

© 1998 Optical Society of America