Dipole and quadrupole solitons in optically-induced two-dimensional defocusing photonic lattices

TL;DR

This paper predicts, observes, and analyzes the stability of dipole and quadrupole solitons in two-dimensional defocusing photonic lattices, combining theoretical, numerical, and experimental approaches.

Contribution

It provides the first combined theoretical, numerical, and experimental study of dipole and quadrupole solitons in 2D defocusing photonic lattices, including stability analysis.

Findings

Stable in-phase nearest-neighbor dipoles exist at intermediate intensities

Numerical quadrupoles can be stable, out-of-phase ones are unstable

Experimental self-trapping of these structures is demonstrated in a 10 mm crystal

Abstract

Dipole and quadrupole solitons in a two-dimensional optically induced defocus- ing photonic lattice are theoretically predicted and experimentally observed. It is shown that in-phase nearest-neighbor dipole and out-of-phase next-nearest-neighbor dipoles exist and can be stable in the intermediate intensity regime. The other types of dipoles are always unstable. In-phase nearest-neighbor quadrupoles are also numerically obtained, and may also be linearly stable. Out-of-phase, nearest-neighbor quadrupoles are found to be typically unstable. These numerical results are found to be aligned with the main predictions obtained analytically in the discrete nonlinear Schroedinger model. Finally, experimental results are presented for both dipole and quadrupole structures, indicating that self-trapping of such structures in the defocusing lattice can be realized for the length of the nonlinear crystal (10 mm).