ABSTRACT
Sharing topology with numerous organic molecules, a wire helix bend into a torus gives a curious object with a gyrotropic behavior which is far from obvious. While a continuous constant current in opposite sections of the torus would create mutually cancelling contributions to its gyrotropic response, an array of tori can show strong circular dichroism linked to the excitation of standing current waves. Here we present the experimental study of optical activity in a chiral toroidal metamaterial and discuss its response in terms of multipole moments, including the elusive toroidal moment.
ABSTRACT
A finite-difference time-domain (FDTD) numerical analysis is used to demonstrate that a toroidal solenoid, coaxial with an electric dipole, is a remarkable nonradiating configuration. It can be used to measure the dielectric permittivity of any ambient matter. It becomes a directional radiator at an interface between two dielectric media, depositing energy in the material with the highest polarizability.
ABSTRACT
Beam coupling influenced by nonlinearly induced diffraction, an effect stemming from the div E-->-term in the wave equations, is stressed in the study. The system considered consists of two beams carried by TE-modes at frequencies of omega and 2omega in quadratic nonlinear planar optical waveguides. The power-conservation law, the Lagrangian and the Hamiltonian of the system, as well as the equations governing its stationary states are derived. It is shown that the nonlinearly induced diffraction modifies the second-order nonlinear terms and acts as an effective third-order nonlinearity. The procedure for dealing with modifications caused by effects like the nonlinearly induced diffraction within the framework of a paraxial approach is discussed. The numerical analysis carried out has the nonlinear wave-number shift and the linear phase mismatch as parameters. The influence of the nonlinearly induced diffraction on the shape (the amplitude and the width) of the solitary waves is demonstrated.
