TRANSVERSE OPTICAL BISTABILITY AND FORMATION OF TRANSVERSE STRUCTURES IN A SODIUM-FILLED FABRY-PEROT RESONATOR

We report the observation of transverse optical bistability (TOB) in a sodium-filled Fabry-Perot resonator, pumped by circularly polarized light, nearly resonant with the D1 line, in the presence of a buffer gas, for low vapor density. A sequence of circularly symmetric patterns, ascribable to superpositions of resonator modes, is obtained. The appearance of TOB can be explained in terms of a self-induced intensity-dependent lens formed in the medium by the interaction with the laser light. A simple model that considers the transverse diffusion of the atoms inside the cell provides predictions in good qualitative agreement with the observations.