# Addressable Refraction and Curved Soliton Waveguides Using Electric Interfaces
## 1 Introduction  
A great deal of attention over the years has been given to the implications and technological applications that could develop from optical spatial solitons [1; 2; 3; 4]. With the expression \"spatial soliton\", we mean light beams that, by modifying the refractive index of the host material, self-confine themselves. That is, these light beams achieve a balance between natural diffraction and nonlinear self-focusing. The result is the writing of modified refractive index channels that behave like waveguides, both for the light that wrote them and for other signals that are injected inside them [5; 6]. Being self-written, the solitonic waveguides exhibit very low propagation losses [7], and above all can be made anywhere in the volume of the host material (i.e., they are perfect 3D structures), in contrast to traditional waveguides, which are instead superficial [8; 9]. Therefore, the use of solitonic guides opens up the possibility of realizing volume circuits with low losses, even if a great limitation to their development is represented by the impossibility of bending such guides and consequently creating complex configurations. In actuality, photorefractive spatial solitons show natural bending [10], the control of which, through the application of background illuminations, is not reliable. Writing complex circuits simply by exploiting natural bending seems like a titanic job. In thepast, [PERSON] et al. [11; 12] have made specular reflections of beams and solitonic guides from the physical edges of the crystals within which they were made, with propagation losses mainly linked to the quality of the surfaces' polishing. This method was effective and expedient, but did not yet allow for the realizing of real complex integrated circuits.  
Studies on liquid crystals, which have extremely high nonlinearities, have shown that it is possible to make nematicons [13] and reflect them on electric interfaces [14]. Such reflections and/or refractions are extremely interesting, because they are addressable, and therefore facilitate acute control of the direction of propagation of the beam. Under the total reflection regime, Giant Goos-Hanchen shifts of the self-confined beams were observed [15; 16]. It was shown that self-confined beams do not behave like light rays, but as \"massive\" entities, and therefore show important inertia in the total reflection process, much more similar to an elastic bump than standard light reflection [17].  
Recently, [PERSON] et al. [18] observed for the first time the total reflection of a photorefractive spatial soliton in pyroliton configuration on an electric interface. In the present work, we investigate, from a numerical perspective, both the refraction and reflection of spatial solitonic waveguides obtained in materials with saturable electro-optic nonlinearity, i.e., those associated with the photorefractive screening solitons. The focus here is on the analysis of the waveguide properties, demonstrating how a fine-tuning of the interfaces would allow for increased control of the guides' reflection and refraction, and therefore their active addressing.