Analysis of the interactions of bright photovoltaic low-divergence soliton-like fields in unbiased self-defocusing photorefractive BaTiO3

Optical spatial solitons are of interest at present due their possible application to integrated all optical circuitry where light controls light. This optical circuitry utilises the various novel properties of the optical spatial soliton, such as rewritable waveguides, and phase dependent interactions. Of all the types of optical spatial solitons, photorefractive (PR) solitons are the subject of much research due to their ease of production and stability. They are readily produced in either self-focusing PR media (photovoltaic solitons), or self-defocusing PR media with an applied external bias (screening solitons). The external bias, typically an applied DC filed, is used to manipulate the self-defocusing PR media to act like self-focusing PR media. However, solitons produced in self-focusing PR media run the risk of over focusing causing permanent damage to the PR media, while applying an external bias to the PR media requires many additional components, increasing the complexity of the system. Recently, we outlined for the first time a theoretical model of soliton-like low divergence fields in unbiased self-defocusing PR media. Numerical analysis of these soliton-like fields showed stability over distances well in excess of both the confocal distance of the beam, and the physical size of the PR media. The present research examines the existence of the low-divergence soliton-like fields and the fundamental nature of the interactions of these low-divergence soliton-like fields in unbiased PR self-defocusing media. Here we show that low-divergence soliton-like fields can be produced in unbiased self-defocusing photorefractive media, and that when the two of these soliton-like fields interact within the PR media, they are forced away from each other