ANALYSIS OF DIFFRACTED WAVES FROM ISOTROPIC CHIRAL GRATINGS

This paper proposes an analysis method of diffracted waves in isotropi c chiral gratings with periodicity in an arbitrary three-dimensional d irection. In this method, the spatial harmonic expansion method applie d to the analysis of anisotropic dielectric gratings is extended. By F ourier transform of the periodicity of the chiral admittance, a system atic matrix form is used for rigorous formulation. In the numerical ex amples given here, calculations are carried out for the density modula ted grating in which the relative dielectric constant and the chiral a dmittance distributions are varied sinusoidally. A coupling between th e circularly polarized diffracted waves due to the Bragg condition and an anomalous diffraction phenomenon due to the chiralty of the medium are presented. This coupling is not observed in the case of nonchiral isotropic dielectric gratings.