Polarization-Dependent gain saturation and nonlinearity-induced anisotropy in the 3.39-µ He-Ne laser amplifier

Polarization dependence of the nonlinear behavior of a high-gain strongly saturated 3.39-μ He-Ne laser amplifier is experimentally investigated. It is found that while circularly and linearly polarized signals propagate through the medium with their polarization unchanged, elliptically polarized signals undergo a change of eccentricity. In addition, the nonlinear gain depends on the input polarization: saturation is strongest for circular and weakest for linear polarization. Excellent agreement is found between the experiment and theoretical predictions.