Coupling between a dark and a bright eigenmode in a terahertz metamaterial

TL;DR

This study investigates the interaction between dark and bright plasmonic modes in a symmetry-broken terahertz metamaterial, revealing how their coupling varies with spectral tuning through spectroscopy and simulations.

Contribution

It provides a systematic analysis of mode coupling in a broken-symmetry metamaterial, highlighting the spectral dependence of dark-bright mode interactions.

Findings

Coupling strength varies with spectral tuning.

Dark and bright modes can be selectively excited.

Symmetry breaking enables mode interaction.

Abstract

Terahertz time domain spectroscopy and rigorous simulations are used to probe the coupling between a dark and a bright plasmonic eigenmode in a metamaterial with broken symmetry. The metamaterial consists of two closely spaced split ring resonators that have their gaps in non-identical positions within the ring. For normal incidence and a fixed polarization both lowest order eigenmodes of the split ring resonators can be excited; although one of them has to be regarded as dark since coupling is prohibited because of symmetry constraints. Emphasis in this work is put on a systematic evaluation of the coupling effects depending on a spectral tuning of both resonances.