Existence curves of asymmetric photorefractive holographic spatial optical solitons

It has been proved that there exist asymmetric holographic spatial optical soliton pairs in biased photorefractive crystals. The two solitons from such a pair have equal width and unequal amplitudes. The soliton existence curves of such soliton pairs are given and three regions of different behaviors exist in these curves. That is, for a given value of bias field, the width of holographic solitons depends strongly on the ratio of the total peak input intensity of the two solitons from a pair to the intensity of the background light when the ratio is small or large enough, whereas it remains relatively constant in a middle region. The extent of the middle region for the asymmetric case is smaller than that for the symmetric case.