Addressable refraction and curved soliton waveguides using electric interfaces

A great deal of interest over the years has been directed to the optical space solitons for the possibility of realizing 3D waveguides with very low propagation losses. A great limitation in their use for writing complex circuits is represented by the impossibility of making curved structures. In the past, solitons in nematic liquid crystals, called nematicons, were reflected on electrical interfaces, and recently on photorefractive spatial solitons as well. In the present work we investigate refraction and total reflection of spatial solitons with saturable electro-optic nonlinearity, such as the photorefractive ones, on an electric wall acting as a reflector. Using a custom FDTD code, the propagation of a self-confined beam was analyzed as a function of the applied electric bias. The electrical reflector has been simulated by applying different biases in two adjacent volumes. We have observed both smaller and larger angles of refraction, up to the critical π/2-refraction condition and then total reflection. The radii of curvature of the associated guides can be varied from centimeters down to hundreds of microns. The straight guides showed losses down to 0.07 dB/cm as previously observed, while the losses associated with single curves were estimated down to 0.2 dB.