Infrared dielectric metamaterials from high refractive index chalcogenides

TL;DR

This paper demonstrates that chalcogenide topological insulators, specifically Bi$_2$Te$_3$, can serve as high-refractive-index dielectric metamaterials in the mid-infrared, enabling strong resonances and potential for advanced nanophotonic applications.

Contribution

It introduces chalcogenide topological insulators as effective dielectric metamaterials in the infrared, highlighting their high refractive index and unique mode structures for nanophotonics.

Findings

Achieved strong electromagnetic resonances in Bi$_2$Te$_3$ in the 2-10 μm range.

Identified excitation of poloidal surface currents in the metamaterials.

Potential for coupling to topological surface states for enhanced light-matter interaction.

Abstract

High-index dielectric materials are in great demand for nanophotonic devices and applications, from ultrathin optical elements to metal-free sub-diffraction light confinement and waveguiding. Here we show that chalcogenide topological insulators are particularly apt candidates for dielectric nanophotonic architectures in the infrared spectral range by reporting metamaterial resonances in chalcogenide crystals sustained well inside the mid-infrared, choosing Bi$_2$Te$_3$ as case study within this family of materials. Strong resonant modulation of the incident electromagnetic field is achieved thanks to the exceptionally high refractive index ranging between 7 and 8 throughout the 2-10 $\mu$m region. Analysis of the complex mode structure in the metamaterial allude to the excitation of poloidal surface currents which could open pathways for enhanced light-matter interaction and low-loss plasmonic configurations by coupling to the spin-polarized topological surface carriers, thereby providing new opportunities to combine dielectric, plasmonic and magnetic metamaterials in a single platform.