Spectroscopic Applications of Phase Conjugation

Abstract

Phase conjugation is an important process¹ that inverts a phase front in space so that it retraces the path through which it came. This can be accomplished either with “rubber mirrors” or with nonlinear optics. It has useful applications in propagation through turbulent media, through bad optics, and through optical fibers. As such, the method interests people in astronomy, military weapons, laser induced fusion, and optical communications. Alternatively, we can turn the technique around to use it to study properties of the conjugating medium. In this paper, we outline this last application, using nonlinear optical techniques. We consider the propagation of two, three, and four-wave electromagnetic fields through “single-photon” two-level media and through two-photon multilevel media. We consider cw fields at first, allowing later treatment of pulsed fields by careful application of Fourier analysis. The approach provides various ways of measuring dipole (T₂) and level (T₁) lifetimes, Stark shifts, and other parameters characterizing the responses of media.

Work supported in part by the Alexander-von-Humboldt Stiftung, and in part by the United States Office of Naval Research under contract N00014-81-K-0754.