<title>Biased photovoltaic spatial solitons and their application in nonlinear guided waves</title>

Abstract

ABSTRACT We study theoretically the properties of waveguides induced by one-dimensional steady-state biased photovoltaic spatialsolitons, and show that the waveguides can be induced by both bright and dark spatial solitons in the biased photovoltaic-photorefractive crystal such as LiNbO3. We also derive wave equations for the probe beam in the general condition andlow-amplitude condition.Keywords: Spatial Optical Solitons, Nonlinear Waveguide, Photorefractive Effects, Photovoltaic Effects 1. INTRODUCTION The guiding of light by light using dark photovoltaic solitons in unbiased photovoltaic-photorefractive crystal', such asLiNbO3, and using both dark and bright screening solitons in biased photorefractive crystal2, such as SBN, has beenreported. This is important because it proves the possibility of developing all-optical circuits. Up to now, three types ofphotorefractive solitons have been reported, they are quasi-steady-state soliton3, screening soliton4 and photovoltaic soliton5.Recent works have shown that another type of photorefractive solitons is possible in biased photovoltaic-photorefractivecrystal and these solitons are known as biased photovoltaic or screening-photovoltaic (SP) solitons6 because they resultfrom both the photovoltaic effect and spatially nonuniform screening of the applied field. As a typical photovoltaic crystal,LiNbO3 can support dark spatial solitons alone if the crystal is unbiased. However, both dark and bright biased photovoltaicsolitons are possible in biased LiNbO3 As a result, the waveguides can be induced in LiNbO3 by both dark and brightspatial solitons ifthe crystal is biased. Although the major advantage ofusing dark spatial solitons rather than bright ones toform waveguides is their much greater stability', the number of possible guided modes in a waveguide induced by a brightsoliton is more than that induced by a dark one2. In this paper,we study theoretically the properties of waveguides inducedby one-dimensional steady-state biased photovoltaic spatial solitons and show that the waveguides induced by both dark andbright solitons are possible in the biased LiNbO3 crystal.