Stable self-guided propagation of two optical harmonics coupled by a microwave or a terahertz wave

We propose a new scheme for self-trapping of (2 + 1)-dimensional optical be ams: parametric interaction between self-guided waves of optical and microw ave (or terahertz) frequencies, which relies on the combination of optical rectification and the electro-optic effect in a bulk noncentrosymmetric med ium. We show that, in spite of strong domination of quasi-cubic terms, quad ratic nonlinearity provides an effective stabilization mechanism to prevent collapse in a large range of parameters where three-wave solitons exist. ( C) 2000 Optical Society of America [S0740-3224(00)00412-4] OCIS codes: 190. 4410, 190.5940.