Dipole-mode vector solitons in anisotropic photorefractive media

Kristian Motzek

Institute of Applied Physics, Darmstadt University of Technology,
Hochschulstraße 4A, 64289 Darmstadt, Germany

Abstract: The self-trapping of light in biased photorefractive crystals eventually leading to (2+1)D optical spatial solitons is being intensely studied by numerous experimental and theoretical groups around the world. For theoretical calculations the photorefractive effect is mostly modelled by a local isotropic saturable nonlinearity. Recent research has shown that this model cannot explain some effects experimantally observed, but that a nonlocal anisotropic model is needed[1]. We use the latter model to find vector solitons and compare the results to experimental data. We find that the anisotropic model yields better agreement to experimental results than the isotropic model.

We present numerically exact solitary solutions to the propagation equations of two incoherently coupled light beams in media with nonlocal anisotropic photorefractive nonlinearity. The vector solitons we studied consist of a nodeless beam and a dipole that is oriented perpendicular to the electric field applied to the photorefractive crystal. The solutions form a continuous set that ranges from vector solitons with negligible dipole contribution to vecor solitons with negligible contribution of the nodeless beam[2]. The theoretical results are compared to experimental data, showing qualitative agreement. Furthermore we show that vector solitons consisting of a nodeless beam and a dipole oriented parallel to the externally applied field do exist, but are far more difficult to obtain experimentally and eventually get unstable.

[1] C. Weilnau, M. Ahles, C. Denz, A. Stepken, K. Motzek, F. Kaiser, "Higher order optical (2+1)dimensional spatial vector solitons in an anisotropic medium", Phys. Rev. E, submitted.

[2] K. Motzek, A. Stepken, F. Kaiser, M. R. Belic, M. Ahles, C. Weilnau, C. Denz, "Dipole-mode vector solitons in anisotropic photorefractive media", Optics Commumications, submitted.