Optical and thermal radiative properties of topological insulator semiconductor multilayers

Abstract

Topological insulator semiconductors hold unique electronic transport characteristics that allow them behave like graphene at the surface of the nanoscale thin film. Photonic multilayers consisting of alternating layers of topological insulator and layers of its dielectric spacer can be engineered to demonstrate optical and thermal radiative dispersion attributed to electromagnetic metamaterials. This paper presents case studies explain the relationships between material compositions, geometrical factors, spectral functions, and electronic transport mechanisms to the overall visible to far-infrared radiative properties. It shows how topological insulator multilayers could be useful in thermal-photovoltaic components, optoelectronic devices, and radiative coatings. Two multilayer cases are investigated: Bi2Se3-ZnSe, and Bi2Te3-ZnTe. In each, the photon-electron oscillation functions are determined, and spectral dielectric functions are fitted into a modified form of effective medium theory. The spectral and angular radiative properties of different constituent thickness multilayer slabs, reflectance and transmittance, are obtained. The multilayer thin films exhibit good reflection or absorption of visible or infrared wavelength radiation, depending on the tunable constituent film thicknesses and material configurations. Finite-difference time domain simulations demonstrate that these materials could have a negative index of refraction, which results from plasmon polariton coupling between the conductive surface states. The results of these radiative properties indicate that topological insulator multilayers may find their use in solar thermophotovoltaic absorbers, optical band pass filters and sub-diffraction thin film lenses.