Strong influence of packing density in terahertz metamaterials

TL;DR

This study reveals that the packing density of split-ring resonator metamaterials critically influences their resonance quality, with an optimal density maximizing the Q factor due to radiative and non-radiative coupling effects.

Contribution

It demonstrates the dependence of terahertz metamaterial resonance quality on unit cell density and identifies an optimal packing density for maximum Q factor.

Findings

Maximum Q factor at one-third resonance wavelength period

Radiative coupling dominates at low densities

Strong inter-resonator coupling increases non-radiative losses at high densities

Abstract

We investigate the response of terahertz metamaterials made of split-ring resonators depending on the unit cell density. It is shown that the fundamental resonance has its highest Q factor for a period of one-third the resonance wavelength. Increasing or decreasing the period from that optimal period reduces the Q factor. All observations are explained by understanding radiative coupling as the dominant loss mechanism at low densities, whereas the strong inter SRR coupling enhances non-radiative losses at high densities. Our results allow designing metamaterials with adjustable Q factors and possibly suggesting that an optimal package density exists to induce the strongest dispersion.