  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 result 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.
