RADIATION PRESSURE IN A RUBIDIUM OPTICAL LATTICE - AN ATOMIC ANALOG TO THE PHOTOREFRACTIVE EFFECT

Probe gain in a rubidium optical lattice is observed when the probe an d lattice beams have identical frequencies. This effect is shown to ar ise from the radiation pressure that shifts the atomic density distrib ution with respect to the optical potential. This effect is compared w ith two-beam coupling in photorefractive materials. The experimental r esults obtained by changing the parameters of the optical lattice (int ensity, detuning, periodicity) are in reasonable agreement with numeri cal simulations based on the model case of a 1/2 --> 3/2 atomic transi tion.