  We report on experimental study of the exciton-polariton emission (PE)
polarization noise below and above the polariton lasing threshold under
continuous wave nonresonant excitation. The experiments were performed with a
high-Q graded 5{\lambda}/2 GaAs/AlGaAs microcavity with three quantum wells in
the strong coupling regime. The PE polarization noise substantially exceeded in
magnitude the shot noise level and, in the studied frequency range (up to 650
MHz), had a flat spectrum. We have found that the PE polarization noise
magnitude dependence on the pump intensity showed specific features that had no
analogy in power dependences of the PE intensity and intensity noise.
Particularly, the linear polarization fluctuations normalized by the emission
intensity showed a remarkably non-monotonic dependence on the pump power. A
theoretical model describing the observed peculiarity of the PE polarization
noise is proposed.
