Two-photon resonantly enhanced self-defocusing in Cs vapor at 1.06 μ

Abstract

The electronic nonlinear refractive index in Cs vapor at 1.06 μ is shown to be negative and to consist of two distinct contributions. One of these contributions arises from a two‐photon resonance in the susceptibility and can be made comparable in magnitude to the positive n₂ in laser glass. The other term arises from population redistributions between the ground and first excited state. We present measurements of self‐defocusing of a single pulse from a Nd: YAG mode‐locked laser that are in agreement with the theoretical predictions.