Addressable Refraction and Curved Soliton Waveguides Using Electric Interfaces

Abstract

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 more recently photorefractive spatial solitons have been, 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 was simulated by applying different biases in two adjacent volumes. We observed both smaller and larger angles of refraction, up to the critical π/2-refraction condition, and then the 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 as low as 0.07 dB/cm as previously observed, while the losses associated with single curves were estimated to be as low as 0.2 dB.

Episodic Memory and Information Recognition Using Solitonic Neural Networks Based on Photorefractive Plasticity

“…Four equal intensity write beams were injected into the input to create the initial balanced network. These beams cross in pairs and then totally reflect at the substrate boundaries [23][24][25] to recreate the geometry of the network previously described in Figure 3. The result is a perfectly balanced network, which means that if any further signal propagating inside a waveguide reaches the crossing, it will be split 50−50 to the output channels.…”

Solitonic waveguide reflection at an electric interface

“…The concept of critical angle, refraction angle which is close to π/2, is still valid for spatial soliton propagation [24]. Its value is fixed once chosen the E i and E r fields.…”

“…By increasing the value of the E r field, so by increasing the refractive index gradient, the reflected beam starts to bend before along the propagation direction and further and further from the interface along the tranverse one. The stronger effect of the interface allows an increased transverse displacement at the output face of the sample and thus an increased addressability of the beam; detailed analysis is discussed in [24].…”

“…In the past a possible solution was achieved by using total reflection of light from crystal physical borders [14] or from interface between two different self-focusing media [15][16][17]. More recently the possibility of adding electrodes to bend self-confined beams has been investigated both in liquid crystals [18], thanks to their large nonlinearities and in photorefractive materials [24]. An alternative and promising approach takes advantage of intensity modulation inside waveguides to route signals in a stigmergic scheme [19].…”

A Nonstandard Path Integral Model for Curved Surface Analysis

“…To evade these difficulties, an assortment of proficient techniques has been proposed (and summarized in [8]), ranging from curvilinear or nonorthogonal FDTD variations to modified Cartesian and conformal algorithms. Nonetheless, the research on this significant topic is constantly escalating, thus leading to various schemes which offer treatment to many contemporary applications from the microwave and optical regime [19][20][21][22][23][24][25][26][27][28][29][30][31] and paving the way to the trustworthy analysis of many future state-of-the-art scientific fields [32][33][34][35][36][37][38][39][40][41][42][43]. Therefore, the manipulation of arbitrarily-curved surfaces or material interfaces via a staircase model deteriorates the reliability of any FDTD-based approach and, particularly, of the NS-FDTD scheme, whose stencils must be very carefully selected.…”