Abstract

A theory is developed to describe echo phenomena produced by counterpropagating pulses. An atomic ensemble is irradiated by two optical pulses, separated in time by T. Each pulse consists of two counterpropagating pulses having arbitrary polarizations, which create a spatially modulated ground-state population and coherence. Owing to the velocity distribution in the sample, the spatial modulation dephases during the interval between the pulses and rephases after the second pulse. At specific times after the second pulse, the populations or coherences or both can be in phase to produce a macroscopic spatially modulated population or coherence. This spatial modulation is detected by scattering an interrogation pulse off the medium at the appropriate echo times. The scattered intensity is measured as a function of T.

© 1993 Optical Society of America