We show that double-charge discrete optical vortices may be completely stable in hexagonal photonic lattices where single-charge vortices always exhibit dynamical instabilities. Even when unstable the double-charge vortices typically have a much weaker instability than the single-charge vortices, and thus their breakup occurs at longer propagation distances.
@article{arxiv.0812.3439,
title = {Stable higher-charge discrete vortices in hexagonal optical lattices},
author = {Kody J. H. Law and P. G. Kevrekidis and Tristram J. Alexander and Wieslaw Krolikowski and Yuri S. Kivshar},
journal= {arXiv preprint arXiv:0812.3439},
year = {2009}
}