Abstract

Transverse structures in the radiation field are well-known in optical systems,^[1] and may show very complex features.^[2] Recent theoretical work^[3] predicts that in a passive resonator even the interaction of a few modes produces interesting patterns (“Transverse Optical Bistability”). A confocal Fabry-Perot resonator filled with sodium vapour was illuminated by a circularly polarized, spatially filtered cw dye laser beam, slightly detuned from the D₁ line. The amount of energy input into the different transverse modes of the empty resonator was controlled. By coupling about 75% of the energy in the TEM₀₀, and about 20% in the TEM₁₀ (Gauss-Languerre) modes, and for small sodium densities (<5·10¹² cm^–3), we obtain the patterns of Fig. 1, which appear, accompanied by hysteresis, by scanning either the input power or the resonator phase.

© 1992 IQEC