Parametric lens

Abstract
A self-focusing is observed that arises from a purely second-order nonlinear susceptibility in a phase-matched second-harmonic-generation experiment. Control of the magnitude and sign of the intensity-dependent phase shift is accomplished through a dispersion external to the nonlinear medium. Analytical expressions characterizing the self-focusing and chirp on both beams in the two-wave parametric interaction are presented and compared with experimental values.