Polarization rotation and exact transverse electromagnetic wave solutions in topological insulators

In the context of $\ensuremath{\theta}$ electrodynamics we find transverse electromagnetic wave solutions forbidden in Maxwell electrodynamics. Our results attest to different signatures of the topological magnetoelectric effect in topological insulators, resulting from a polarization rotation of an external electromagnetic field. Unlike Faraday and Kerr rotations, the effect does not rely on a longitudinal magnetic field, the reflected field, or birefringence. The rotation occurs due to transversal discontinuities of the topological magnetoelectric parameter in cylindrical geometries. The dispersion relation is linear, and birefringence is absent. Exact transversality allows electromagnetic waves to propagate in an optical fiber without successive total internal reflections, diminishing losses, and regardless of acute bends of the fiber. These results may open other possibilities in optics and photonics by utilizing topological insulators to manipulate light.