Photorefractive Photovoltaic Spatial Solitons in Slab LiNbO₃ Waveguides

Abstract

In the past few years, photorefractive spatial solitons that exist at low power level have been predicted [1] and experimentally confirmed in transient regime [2]. Later, by addition of a background illumination, steady-state screening solitons have been demonstrated [3]. Photorefractive solitons have since been the subject of an intensive work. In addition to SBN crystals in which photorefractive solitons were first observed, different materials (BTO, KNbO₃, LiNbO₃ or InP) can support photorefractive solitons. Spatial solitons relying on the photovoltaic effect have also been studied and observed in bulk crystals [4–8]. In the widely used material LiNbO₃ light induces a photovoltaic space charge field effect that diminishes the index of refraction. This allows dark soliton observation. Dark photovoltaic 1 -D soliton were first obtained in Bulk LiNbO₃ crystals [6] and have been used to create Y-junction [7]. Recently, 2-D photovoltaic solitons have also been reported in a KNSBN crystal [8].