Sequential formation of incoherent multiple gray solitons in biased photorefractive-photovoltaic crystals

We show that incoherent gray soliton splitting is possible in biased photorefractive-photovoltaic crystals. If the full width half maximum (FWHM) of the incoherent beam's intensity or the incoherent beam's grayness is small, only a Y-junction soliton is generated, corresponding to the lowest order in even-number soliton sequence. If the intensity FWHM of the incoherent beam or the incoherent beam's grayness is increased, the gray soliton beam splits into an even-number sequence of multiple gray solitons. The properties of incoherent gray soliton splitting in biased photorefractive-photovoltaic crystals are discussed and we find that it is incoherent gray screening soliton splitting when the bulk photovoltaic effect is neglectable and incoherent gray photovoltaic soliton splitting when the external bias field is absent.