Coherently coupled solitons in photorefractive media due to pyroelectric effect

The existence of bright-bright, dark-dark and gray-gray coherently coupled soliton pairs is predicted in unbiased photorefractive pyroelectric materials, provided that the two mutually-coherent incident optical beams have the same wavelength and same polarization. The external electric field is replaced by a finite temperature change and hence the space charge field is formed due to pyroelectric effect only. We study the effect of the mutual phase difference and the beam intensity ratio on the soliton profiles. In addition, we find that the magnitude and sign of the temperature change can influence the formation and characteristics of these soliton pairs.