Counterpropagating self-trapped beams in optical photonic lattices

M Belić,D Arsenović,M Petrović,D Jović,S Prvanović

doi:10.1364/opex.14.000794

Abstract

Dynamical properties of counterpropagating (CP) mutually incoherent self-trapped beams in optically induced photonic lattices are investigated numerically. A local model with saturable Kerr-like nonlinearity is adopted for the photorefractive media, and an optically generated two-dimensional fixed photonic lattice introduced in the crystal. Different incident beam structures are considered, such as Gaussians and vortices of different topological charge. We observe spontaneous symmetry breaking of the head-on propagating Gaussian beams as the coupling strength is increased, resulting in the splitup transition of CP components. We see discrete diffraction, leading to the formation of discrete CP vector solitons. In the case of vortices, we find beam filamentation, as well as increased stability of the central vortex ring. A strong pinning of filaments to the lattice sites is noted. The angular momentum of vortices is not conserved, either along the propagation direction or in time, and, unlike the case without lattice, the rotation of filaments is not as readily observed.

Highlights

An intense interest was generated recently in the propagation and interactions of self-focused light in photonic lattices imbedded in photorefractive (PR) crystals, giving rise to the discrete diffraction and offering intriguing waveguiding possibilities [1,2,3]
A local model with saturable Kerr-like nonlinearity is adopted for the photorefractive media, and an optically generated two-dimensional fixed photonic lattice introduced in the crystal
An especially interesting geometry from the applications point of view is the photonic crystal fiber (PCF), in which a finite hexagonal lattice of holes is infused into a silica fiber, with the central hole absent [8]

Summary

Introduction

An intense interest was generated recently in the propagation and interactions of self-focused light in photonic lattices imbedded in photorefractive (PR) crystals, giving rise to the discrete diffraction and offering intriguing waveguiding possibilities [1,2,3]. An especially interesting geometry from the applications point of view is the photonic crystal fiber (PCF), in which a finite hexagonal lattice of holes is infused into a silica fiber, with the central hole absent [8]. Such a 2D PCF with a central defect, referred to as the “holey fiber”, offers a different scenario of waveguiding from the perfectly periodic infinite photonic crystal (PC) with dielectric rods or beams of light, in that it displays huge refractive index step, and that the light is pinned to the defect. For some values of the coupling strength an indefinite rotation of the central vortex filaments is observed

The model

Counterpropagating Gaussian beams

Counterpropagating vortices

Findings

Conclusions