Self-trapping of optical vortices at the surface of an induced semi-infinite photonic lattice

Daohong Song,Liqin Tang,Zhigang Chen,Cibo Lou,Zhuoyi Ye,Jingjun Xu,P.G Kevrekidis,Kody J H Law

doi:10.1364/oe.18.005873

Abstract

We demonstrate self-trapping of singly-charged vortices at the surface of an optically induced two-dimensional photonic lattice. Under appropriate conditions of self-focusing nonlinearity, a singly-charged vortex beam can self-trap into a stable semi-infinite gap surface vortex soliton through a four-site excitation. However, a single-site excitation leads to a quasi-localized state in the first photonic gap, and our theoretical analysis illustrates that such a bandgap surface vortex soliton is always unstable. Our experimental results of stable and unstable topological surface solitons are corroborated by direct numerical simulations and linear stability analysis.

Highlights

In recent years, there has been an increased interest in the study of nonlinear discrete surface waves in periodic structures [1,2]
We demonstrate self-trapping of singly-charged vortices at the surface of an optically induced two-dimensional photonic lattice
Under appropriate conditions of self-focusing nonlinearity, a singly-charged vortex beam can self-trap into a stable semi-infinite gap surface vortex soliton through a four-site excitation

Summary

Introduction

There has been an increased interest in the study of nonlinear discrete surface waves in periodic structures [1,2]. The phenomena of nonlinear surface states were enriched by prediction and demonstration of a variety of surface or interface solitons in the 2D domain, including multipole mode surface solitons [11], angular surface solitons [12], lattice interface solitons [13], and surface soliton arrays [14], to name just a few Despite of these efforts on surface solitons, to our knowledge, no experimental work has investigated self-trapping of optical vortices at the surfaces of optical periodic structures. A SCV beam under the single-site excitation evolves into a quasi-localized surface state in the first photonic bandgap In this latter case, our theoretical results from both direct evolution of the system and bifurcation analysis indicate that such self-trapped surface vortices are unstable

Experimental results

Numerical results

Conclusion