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Self-Focusing, Switching, and Spatial Solitons in Quasi-Phase-Matched Quadratic Media

Yuri S. Kivshar and Ole Bang, Optical Sciences Centre, Australian National Univ., Canberra, Australia, and Carl Balslev Clausen, Technical Univ. of Denmark, Lyngby, Denmark.

Recently, the study of effects produced by the parametric wave mixing in quadratic nonlinear optical materials has attracted growing attention because of exciting prospects for all-optical switching devices. Many of the theoretically predicted effects, such as large nonlinear phase-shifts and spatial two-component soli-tons (fundamental and second harmonic, mutually trapped), have already been observed experimentally, e.g., in a KTP bulk crystal and LiNbO3 slab waveguides. However, for the quadratic nonlinearity to be effective, the wavevector mismatch between the fundamental and second harmonic must be small. So far the efficiency has been quite low, mainly due to restrictions imposed by the use of birefringent phase-matching techniques, and consequently, the required input power has been high.