S. G. Dinev, A. A. Dreischuh, S. Balushev
The conditions for propagation of light-pulse-pair with nearly constant temporal and spatio-temporal parameters in nonlinear media are found in a broad range from quasi-cw to subpicosecond pulses. Because of the crucial dependence of the beam/pulse parameters from those of the complementary beam/pulse, the regime exhibits a symbiotic character. A set of balance solitary conditions is found between the signs and the values of the nonlinear susceptibilities for self-phase modulation, cross-phase modulation and the pump powers. The temporal and spatio-temporal modulation stability of the symbiotic light pair are discussed.