Symbiotic solitary-wave attractor in backward quadratic nonlinear interaction

Considering non-degenerate, backward quasi-phase matched parametric interac tion in the presence of dissipation and dispersion, we show that quadratic media support a novel type of symbiotic solitary-wave attractor. We study t he spontaneous generation of the new solitary waves and identify a velocity selection mechanism. The selected velocity depends on the injected continu ous-pump intensity and can take any subluminous Value (positive or negative ). As a particular case, we point out a new mechanism of energy localizatio n through the zero-velocity symbiotic solitary wave which is spontaneously generated from noise fluctuations.