Laser-induced dichroism and birefringence in two- and three-level systems of neon

We have observed the Doppler-free dichroism and birefringence induced by a linearly polarized laser beam (pump beam) by monitoring the polarization and amplitude changes of a weak probe beam through an analyzer. The effects have been observed in two-level systems and also in three-level systems of Ne I. At rather low pump power, a typical refractive-index anisotropy of 10−8 has been measured. We have shown that, when the normal resonance curve exhibits a broad background due to collisions, our method allows the elimination of this background. In addition, using a rotating analyzer, we have obtained simultaneously the dichroism and birefringence curves, i.e., the imaginary and real part of the anisotropic-induced susceptibility.