Polarization-dependent electromagnetic responses of ultrathin and highly flexible asymmetric terahertz metasurfaces

TL;DR

This paper demonstrates how asymmetric ultrathin terahertz metasurfaces exhibit polarization-dependent electromagnetic responses, including high-Q resonances and EIT-like effects, enabling advanced filtering and sensing applications.

Contribution

It introduces a novel design of asymmetric THz metasurfaces that achieve polarization-dependent high-Q modes and electromagnetic induced transparency, advancing metasurface functionalities.

Findings

Secondary mode Q factor nearly 9 times higher than fundamental

Full suppression of secondary mode at polarization angles ≥ 60°

Observation of polarization selective EIT at certain asymmetries

Abstract

We report the polarization-dependent electromagnetic response from a series of novel terahertz (THz) metasurfaces where asymmetry is introduced through the displacement of two adjacent metallic arms separated by a distance $\delta$. For all polarization states, the symmetric metasurface exhibits a low quality (Q) factor fundamental dipole mode. By breaking the symmetry, we experimentally observe a secondary dipole-like mode with a Q factor nearly $9\times$ higher than the fundamental resonance. As $\delta$ increases, the fundamental dipole mode $f_{1}$ redshifts and the secondary mode $f_{2}$ blueshifts creating a highly transmissive spectral window. Polarization-dependent measurements reveal a full suppression of $f_{2}$ for all asymmetries at $\theta \geq 60^\circ$. Furthermore, at $\delta \geq 60 \text{ }\mu\text{m}$, we observe a polarization selective electromagnetic induced transparency (EIT) for the fundamental mode. This work paves the way for applications in filtering, sensing and slow-light devices common to other high Q factor THz metasurfaces with EIT-like response.