Quadratic spatial soliton generation by seeded down conversion of a strong pump beam

Quadratic spatial solitons have been generated during second-harmonic generation under easy-to-achieve conditions and should be pervasive in other second-order nonlinear interactions. One of the more interesting cases is the downconversion process, which is the essence of parametric generators and oscillators. In this investigation, we report on the generation of two-dimensional quadratic spatial solitons (QSS) in a KTP crystal near the degeneracy point for the parametric interaction, i.e., the reverse second-harmonic generation. Here we report on the observation of such solitons in a l-cm-long KTiOPO/sub 4/ crystal where the extraordinarily polarized harmonic field interacts with two fundamental fields with both ordinary and extraordinary components.