Abstract

Atoms are diffracted at Standing light waves in a temporal and spatial Bragg regime. The standing light field represents a light crystal with a complex index of refraction for the atomic matter-waves. By adjusting the light frequency near an open transition of our metastable argon atoms, we can select a negative, a positive, or a purely imaginary (absorptive) interaction potential. Since light crystals can be easily overlapped, it is possible to generate very unusual crystal potentials, both in space and time, by superposing different light frequencies.

© 1998 IEEE