Negative refraction and backward wave in chiral mediums: Illustrations of Gaussian beams

Abstract

We investigate the phenomena of negative refraction and backward wave in chiral mediums, with illustrations of Gaussian beams. Due to symmetry breaking intrinsic in chiral mediums, there exist two circularly polarized eigenwaves with different wave vectors. The two waves begin to split from each other as the chirality parameter increases from zero. The right (left)-handed circularly polarized wave tends to move toward (away from) the normal to the interface. As the chirality exceeds a critical value, the left-handed wave is flipped to the other side of the interface normal, that is, negatively refracted, and becomes a backward wave. These features are illustrated with Gaussian beams based on Fourier integral formulations. The special condition of perfectly negative refraction in chiral mediums is also discussed.