  We have studied the noise spectra in a nonlinear magneto-optical rotation
experiment in a rubidium vapor. We observed the reduction of noise in the
intensity difference of two orthogonally polarized components of the laser
beam. The dependence of the noise level on both the frequency and the
longitudinal magnetic field has been studied. We found that the optimal
condition for the noise reduction is to work around zero longitudinal magnetic
field, where the intensity correlation between the two orthogonally polarized
components is maximum. Our results can be used to reduce or eliminate the
atomic excess noise, therefore improving the sensitivity of nonlinear
magneto-optical rotation magnetometers and other atom-optical based
applications.
