We show that the description of light in terms of Stokes operators in combination with the assumption of Gaussian statistics results in a dramatic simplification of the experimental study of fluctuations in the light transmitted through an atomic vapor: no local oscillator is required, the detected quadrature is easily selected by a wave-plate angle, and the complete noise ellipsis reconstruction is obtained via matrix diagonalization. We provide empirical support for the assumption of Gaussian statistics in quasiresonant light transmitted through an
87Rb vapor cell and we illustrate the suggested approach by studying the evolution of the fluctuation ellipsis as a function of laser detuning. Applying the method to two light beams obtained by parting squeezed light in a beam splitter, we have measured the entanglement and quantum Gaussian discord.
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
D1 line. For linearly polarized incident light, three stable states appear in the polarization of the transmitted light: ${\ensuremath{\sigma}}_{+}$ dominant, ${\ensuremath{\sigma}}_{\ensuremath{-}}$ dominant, and linear polarization.