Giant THz surface plasmon polariton induced by high-index dielectric metasurface

TL;DR

This paper demonstrates a novel high-index dielectric metasurface that induces a giant THz surface plasmon resonance, offering enhanced tunability and field enhancement for sensing and spectroscopy.

Contribution

It introduces a dielectric TiO2 grating as a tunable coupler for THz surface plasmons, revealing a stronger resonance than metallic gratings and detailed mechanisms.

Findings

Discovery of a giant resonance with enhanced electric field

Resonance tunability via dielectric grating parameters

Strong surface plasmon excitation modulated by phase and amplitude

Abstract

We use computational approaches to explore the role of a high-refractive-index dielectric TiO2 grating with deep subwavelength thickness on InSb as a tunable coupler for THz surface plasmons. We find a series of resonances as the grating couples a normally-incident THz wave to standing surface plasmon waves on both thin and thick InSb layers. In a marked contrast with previously-explored metallic gratings, we observe the emergence of a much stronger additional resonance. The mechanism of this giant plasmonic resonance is well interpreted by the dispersion of surface plasmon excited in the air\TiO2\InSb trilayer system. We demonstrate that both the frequency and the intensity of the giant resonance can be tuned by varying dielectric grating parameters, providing more flexible tunability than metallic gratings. The phase and amplitude of the normally-incident THz wave are spatially modulated by the dielectric grating to optimize the surface plasmon excitation. The giant surface plasmon resonance gives rise to strong enhancement of the electric field above the grating structure, which can be useful in sensing and spectroscopy applications.