Observation of polarization quantum noise of laser radiation in Rb vapor cell

We present experimental study of polarization quantum noise of laser radiation passed through optically think vapor of Rb 87 . We observe a step-like noise spectrum. We discuss various factor which may result in such noise spectrum and prevent observation of squeezing of quantum fluctuations predicted in Matsko et al, Phys. Rev. A 63 , 043814 (2001).