High-Q terahertz Fano resonance with extraordinary transmission in concentric ring apertures

Jie Shu,Qianfan Xu,Daniel Nickel,Daniel M Mittleman,Jason Dominguez,Weilu Gao,Kimberly Reichel,Igal Brener

doi:10.1364/oe.22.003747

Abstract

We experimentally demonstrate a polarization-independent terahertz Fano resonance with extraordinary transmission when light passes through two concentric subwavelength ring apertures in the metal film. The Fano resonance is enabled by the coupling between a high-Q dark mode and a low-Q bright mode. We find the Q factor of the dark mode ranges from 23 to 40, which is 3~6 times higher than Q of bright mode. We show the Fano resonance can be tuned by varying the geometry and dimension of the structures. We also demonstrate a polarization dependent Fano resonance in a modified structure of concentric ring apertures.

Highlights

Terahertz (THz) on-chip planar metamaterials have emerged as an important active and passive device with different functionalities, such as sensing [1,2,3], extraordinary transmission [4,5,6,7], and asymmetric transmission [8]
We experimentally demonstrate a polarization-independent terahertz Fano resonance with extraordinary transmission when light passes through two concentric subwavelength ring apertures in the metal film
The Fano resonance is enabled by the coupling between a high-Q dark mode and a low-Q bright mode

Summary

Introduction

Terahertz (THz) on-chip planar metamaterials have emerged as an important active and passive device with different functionalities, such as sensing [1,2,3], extraordinary transmission [4,5,6,7], and asymmetric transmission [8]. Several studies have reported polarization insensitive Fano resonances in subwavelength concentric metallic rings in radio frequency region [21,22,23], in optical and near-infrared spectral ranges [24], and theoretically in THz region [25], or concentric ring apertures in the metal film in mid-infrared (MIR) range [26]. We theoretically and experimentally demonstrate a polarization independent Fano resonance in concentric two-ring aperture arrays in a metallic film in the THz spectral range. We show that in a modified structure, the Fano resonance can be switched on and off by changing the polarization of incident THz beam, which reveals the different nature of current flow patterns between the bright and dark modes

Fabrication

Results

Selectively disabling dark mode without affecting bright mode

Conclusions