Anisotropic waveguides induced by photorefractive (2+1)D solitons

Abstract

We present theoretical and experimental investigations of the anisotropic character of the refractive-index modulation that is induced by a light beam propagating in a photorefractive strontium barium niobate crystal. Such a structure creates a so-called spatial screening soliton that is able to carry a second wave of a different wavelength and therefore can act as a waveguide. We show in numerical simulations as well as in experimental investigations the anisotropic property of refractive-index modulation. Furthermore, the noncircular shape of the induced waveguide is justified by the excitation of higher-order modes, which were found to be asymmetric in both transverse directions. Whereas in the direction perpendicular to the applied electric field the TEM 01 and TEM 02 modes can easily be excited, excitement of the TEM 10 mode in the direction of the applied field is rather difficult. This effect can be explained by the constricted extension of the waveguide in this direction.

Solitonic lattices in photorefractive crystals

“…However, ordered arrays of Gaussian beamlets (∼10 µm), launched in conditions appropriate to the generation of spatial screening solitons [2], form much more stable solitonic lattices. Weakly interacting pixel-like arrangements of solitons that can individually be addressed are interesting for applications as self-adaptive waveguides [3,4].Adaptive waveguides are of particular interest in alloptical information processing for their potential to generate large arrays, as well as for allowing many configurations with different interconnection possibilities. Spatial optical solitons are natural candidates for such applications, owing to their ability for self-adjustable waveguiding and versatile interaction capabilities, as demonstrated in light-induced Y and X couplers, beam splitters, directional couplers and waveguides.…”

“…However, ordered arrays of Gaussian beamlets (∼10 µm), launched in conditions appropriate to the generation of spatial screening solitons [2], form much more stable solitonic lattices. Weakly interacting pixel-like arrangements of solitons that can individually be addressed are interesting for applications as self-adaptive waveguides [3,4].…”

“…Early experimental results on an incoherent control were presented in Refs. [3,4,7,10]. Here we display the comparison with experiment, using an incoherent control beam acting on a pair of coherent pixels (Fig.…”

Interactions in large arrays of solitons in photorefractive crystals

“…Every single channel is scanned separately, and the individual images are superimposed electronically. Coupling efficiency for the amount of energy coupled into a single waveguide is measured to be around 56% [3]. Apparently the radiated light is not trapped by the adjacent channels.…”

“…If, however, one launches an ordered array of Gaussian beamlets in conditions appropriate to the generation of spatial screening solitons [2], a much more stable solitonic lattice can be formed. Weakly interacting pixel-like arrangements of solitons that can be individually addressed are interesting for self-adaptive waveguiding [3,4]. Furthermore, such lattices present natural examples of selfproduced reconfigurable two-dimensional photonic crystals, although on a much larger scale.…”