Counterpropagating optical beams and solitons

Abstract

Physics of counterpropagating optical beams and spatial optical solitons is reviewed, including the formation of stationary states and spatiotemporal instabilities. First, several models describing the evolution and interactions between optical beams and spatial solitons are discussed, that propagate in opposite directions in nonlinear media. It is shown that coherent collisions between counterpropagating beams give rise to an interesting focusing mechanism resulting from the interference between the beams, and that interactions between such beams are insensitive to the relative phase between them. Second, recent experimental observations of the counterpropagation effects and instabilities in waveguides and bulk geometries, as well as in one-and two-dimensional photonic lattices are discussed. A variety of different generalizations of this concept are summarized, including the counterpropagating beams of complex structures, such as multipole beams and optical vortices, as well as the beams in different media, such as photorefractive materials and liquid crystals.

Quantum criticality in photorefractive optics: Vortices in laser beams and antiferromagnets

“…The classification of topological solutions and the vortex Hamiltonian Now we discuss the possible topological solitons in our system. Remember once again that they differ from dynamical solitons such as those studied in [17] and references therein. In order to classify the topologically nontrivial solutions, consider first the symmetries of the Lagrangian (4).…”

“…In optics, they are often called spatial solitons. Dynamical solitons in nonlinear optics are a celebrated and well-studied topic [17][18][19][20][21][22], they show an amazing variety of patterns and phenomena like localization, Floquet states [14], etc. But in general they do not have a topological charge.…”

“…The optical response of the crystal depends nonlinearly on the total intensity of both beams, which means the beams effectively interact with each other. This system has been thoroughly investigated for phenomena such as dynamical solitons [17,31,32], vortex stability on the photonic lattice [18][19][20][33][34][35][36] and global rotation [37]. We will see that the CP beams are an analog of the two-component planar antiferromagnet, which can further be related to some realistic strongly-correlated materials [38][39][40].…”

“…The charge field E on the right-hand side of the equation is the electric field sourced by the charges in the crystal (i.e., it does not include the external electric field of the beams). Its evolution is well represented by a relaxation-type equation [17]:…”

Counter-propagating soliton interactions in photorefractive InP:Fe semiconductor

“…The aim of our experiment was to inject two parallel, counter-propagating infrared laser beams inside the InP:Fe crystal. When the two beams overlap by their evanescent fields, they start interacting via mutual change of the refractive index [4,7]. Good adjustments of the laser parameters are required, mainly because at high light intensities, nonlinear spatio-temporal instabilities can occur [7,8].…”