Polarization independent lattice-coupled terahertz toroidal excitation

Abstract

The toroidal dipole excitation is important for metamaterial research because of its low-loss attribute. In this study, we demonstrate numerically and experimentally, a unique toroidal metasurface that modulates a broad resonance into a sharp mode, independent of the polarization of the incident terahertz radiation, by coupling the inherent toroidal dipole excitation to the lattice mode of the metasurface. The advantage of polarization independence enables the excitation of lattice-coupled toroidal mode for both the orthogonally polarized states of the incident terahertz radiation in the metasurface. The interaction of the two resonances results in the enhancement of the quality factor of the metasurface at the point of resonance matching. The surface current profile as well as multipole analysis of scattered powers by electric, magnetic, and toroidal dipoles confirm the domineering effect of toroidal dipole excitation for both the polarization states of incident terahertz radiation. Such a lattice-matched toroidal excitation-based device has the potential to impact the development of polarization-independent terahertz components for ultrasensitive sensors, lattice-enhanced equipment, and slow light devices for light-matter interaction.

Terahertz binary computing in a coupled toroidal metasurface

“…The final metasurface configuration was fabricated for four different geometries for values of of and corresponding to (10 m, 10 m), (10 m, 20 m), (20 m, 10 m), and (20 m, 20 m) respectively. The fabricated samples were then characterized using a THz-time domain spectroscopy (THz-TDS) setup consisting of two fibre-coupled photo-conductive antennas 37 . The response of the bare quartz substrate, termed as reference, is first analyzed followed by analyzing the response of the metasurface (sample).…”

A study on the electromagnetic mechanism of a flexible terahertz toroidal dipole metasurfaces

“…The dielectric materials were used to design the metamaterials, and the Q-factor is relatively high due to the low loss of the dielectric materials. Some of them can be realized both in the simulation and experiment, and the unit cell structure is often consisted of metallic pattern layer fabricated on the silicon/quartz substrate [34][35][36][37]. The asymmetry structure including Fano structure is designed to construct the toroidal dipole resonance.…”