Chiral electromagnetic waves at the boundary of optical isomers: Quantum Cotton-Mouton effect

We demonstrate that the boundary of two optical isomers with opposite directions of the gyration vectors (both parallel to boundary) can support propagation of electromagnetic wave in the direction perpendicular to the gyration axes (Cotton-Mouton geometry). The components of electromagnetic field in this wave decay exponentially into both media. The characteristic decay length is of the order of the Faraday rotation length for the propagation along the gyration axis. The remarkable property of the boundary wave is its chirality. Namely, the wave can propagate only in one direction determined by the relative sign of non-diagonal components of the dielectric tensor in contacting media. We find the dispersion law of the boundary wave for the cases of abrupt and smooth boundaries. We also study the effect of asymmetry between the contacting media on the boundary wave and generalize the results to the case of two parallel boundaries. Finally we consider the arrangement when the boundaries form a random network. We argue that at a point, when this network percolates, the corresponding boundary waves undergo quantum delocalization transition, similar to the quantum Hall transition. PACS numbers: 72.15.Rn, 73.40.Hm, 78.20.Ek Typeset using REVTEX 1 Optical properties of gyrotropic and optically active media are well known and described in many textbooks (see e.g. Ref. 1). A homogeneous gyrotropic medium is characterized by the following relation between the displacement vector and electric field D = ε̂E, where the tensor ε̂ has the following form