Generation of arrays of bright and dark spatial solitons in a photorefractive

Summary form only given. We study the propagation of a sinusoidal pattern, with a visibility of one, in a photorefractive Bi/sub 12/TiO/sub 20/ crystal under an external electric field to excite a focusing or defocusing nonlinearity. When a self focusing applied voltage is used an array of fundamental bright solitons is produced and when a self defocusing one is used an array of dark spatial solitons is formed for a determined magnitude of the field. Increasing the external field creates an array with a doubling frequency with to respect to the initial one.