Observation of Optical Tristability in Sodium Vapors

Optical tristability via optical pumping has been observed in the transmission of a Fabry-Perot interferometer containing Na vapor irradiated by light from a cw dye laser on the high-frequency wing of the $D_1$ line. For linearly polarized incident light, three stable states appear in the polarization of the transmitted light: ${\sigma }_{+}$ dominant, ${\sigma }_{-}$ dominant, and linear polarization.