Limit of sensitivity of laser ellipsometry for the detection of magnetically-induced birefringence

The technique to detect small birefringence has been developed and systematic measurements on the magnetically-induced birefringence of the gaseous samples oxygen, nitrogen, and the noble gases, have been made. In the present paper we describe a noise reduction technique to attain the shot-noise limit. Our approach is based on a light extinction ratio which is good enough to reduce the noise due to fluctuations of the light source intensity and on an proper adjustment of the polarization state of incident light.