Gray spatial solitons in biased photorefractive media

We provide a detailed analysis of gray spatial optical solitons in biased photorefractive media. The properties associated with these solitons, such as their transverse velocity, spatial width, and phase profile, are obtained as functions of their normalized intensity and degree of "grayness." By employing the stability criterion based on the renormalized field momentum, we investigate the stability regions of gray spatial photorefractive solitons. The process of the soliton Y splitting arising from an initially even field depression is quasi-analytically described by use of a Hamiltonian formalism. (C) 2001 Optical Society of America.