Gaussian soliton pairs in an unbiased photorefractive crystal due to the pyroelectric effect

Abstract

The characteristics of the dynamical evolution of incoherently coupled Gaussian soliton pairs in unbiased photorefractive media forming solely due to the pyroelectric effect are studied for the first time. A parameter space spawning a large set of bright Gaussian soliton pairs in unbiased photorefractive crystals having a large pyroelectric coefficient has been found. These soliton pairs can exist if the light beams have similar polarization, equal wavelength and are mutually incoherent. A change in the temperature of the photorefractive crystal induces a temporary pyroelectric field resulting in the formation of a space-charge field. The existence curve for these soliton pairs is studied for different values of the temperature change. It is also established that both individual components of the soliton pair should have equal spatial widths for stable propagation. The whole parameter space in which these soliton pairs exist as a changeless entity has been investigated in terms of the spatial width of the soliton pair, their peak power, and the magnitude of temperature change of the crystal. The magnitude of the temperature change profoundly affects the evolution characteristics of these Gaussian soliton pairs. The stability of such soliton pairs has been demonstrated using the paraxial theory. Bistable states have been shown to exist in the system irrespective of the magnitude of the temperature change for the case when both components of the soliton pair have equal power. A lithium niobate (LN) crystal has been considered to illustrate the relevant results.