Dark Soliton Stripes, Vortices and Soliton-induced Waveguides Formed in Bulk Photorefractive Media

Photorefractive spatial solitons [1-3] are promising for applications in all-optical switching, optical interconnects and the development of novel photonic devices. We report on study of steady-state dark photorefractive screening-solitons, formed when a laser beam containing a dark notch propagates through a bulk strontium barium niobate crystal biased by an electric field. A dark photorefractive soliton, although generated with a weak beam, induces a waveguide in the bulk of the crystal that guides other strong beams of longer wavelengths. Fundamental, Y-Junction and multiple dark photorefractive solitons are observed, so are the waveguides they induce that can guide other beams into multiple channels [3]. A dark photorefractive soliton can also couple with another dark or bright soliton, forming interesting coupled spatial soliton pairs that consist of self-guided propagation of two beams in the photorefractive materials [4]. Recently, we have demonstrated steady-state self-trapping of circular and elliptical optical vortices (in both transverse dimensions) due to two distinctly different nonlinear mechanisms: the bulk photovoltaic effect in an unbiased LiNbO3 crystal, and the photorefractive screening effect in a biased SBN crystal [5].