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, 5, 6, 7, 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].