Abstract

Quadratic spatial solitons (QSSs) form a family of self-trapped beams that consist of multifrequency waves that are coupled via strong phase and energy exchange between interacting waves.¹·² The experimental observation of such waves in a three-dimensional bulk medium was first demonstrated for second- harmonic generation (SHG) in KTP.³ In this early experiment, a type II crystal was utilized to allow for a three-wave interaction between the second harmonic (SH) and two fundamental waves (FW). However, the powers in the two orthogonal polarizations for the FW were equal, which led to a single family of solitons for a given phase mismatch and incident intensity. This current work demonstrates experimentally that these solitons are only a small part of an extended family of quadratic solitons with different compositions of the three fields, which can propagate under type II phase-matching conditions, as predieted by Buryak et al.⁴ The soliton threshold and the equilibrium composition of these solitons was investigated for conditions of different phase matching and energy in the two input fundamental beams.

© 1998 Optical Society of America