Theory of topological insulator waveguides: polarization control and the enhancement of the magneto-electric effect

TL;DR

This paper demonstrates that a topological insulator waveguide can significantly enhance the magneto-electric effect, enabling greater polarization control of light with simple multilayer structures, advancing photonic device capabilities.

Contribution

It introduces a waveguide design with a topological insulator layer that amplifies the magneto-electric effect and allows efficient polarization control in photonic applications.

Findings

Achieves polarization rotations of 100-1000 mrad using a three-layer structure.

Rotation angle and ellipticity depend on permittivity contrast and symmetry-breaking strength.

Enhances observability and control of the magneto-electric effect in photonic devices.

Abstract

Topological insulators subject to a time-symmetry-breaking perturbation are predicted to display a magneto-electric effect that causes the electric and magnetic induction fields to mix at the material's surface. This effect induces polarization rotations of between ~1-10 mrad per interface in incident plane-polarized light normal to a multilayered structure. Here we show, theoretically and numerically, that, using a waveguide geometry with a topological insulator guide layer and dielectric cladding, it is possible to achieve rotations of between ~100-1000 mrad and generate an elliptical polarization with only a three-layered structure. Both the rotation angle and ellipticity are dependent on the permittivity contrast of the guide and cladding layers and the strength of the time-symmetry-breaking perturbation. This geometry is beneficial, not only as a way to enhance the magneto-electric effect, rendering it easier to observe, but also as a method for controlling the polarization of light in the next generation of photonic devices.