Double E-shaped toroidal metasurface with high Q-factor Fano resonance and electromagnetically induced transparency

Ting Chen,Jianwei Wang,Tianyu Xiang,Tao Lei,Fushan Lu

doi:10.1063/5.0057480

Abstract

A double E-shaped toroidal dipole metasurface is designed with the high Q-factor Fano and classical electromagnetically induced transparency (EIT) phenomena in the microwave frequency range. With the introduction of an asymmetric structure, the sharp Fano resonance can be excited and acquired a quite high Q-factor of 134 at a lower frequency of 4.58 GHz. It can be numerically and experimentally demonstrated that the singularity Fano response of designed construction is caused by the intensive toroidal dipole. In addition, due to destructive interference between the intensive toroidal dipole and electric dipole, the transmission peak of EIT can reach 0.95 with a Q-factor of 50 at 10.18 GHz. By calculating and comparing the radiated power of multipoles, the enhanced toroidal dipole response can be further verified. The designed planar toroidal dipole metamaterial with simple construction may have many possible applications in toroidal moment generators, sensing, and slow-light devices.

Highlights

A toroidal dipole (TD),1 as the fundamental member of the toroidal multipole family, is the third family different from the traditional electric and magnetic dipoles
A TD is created by the electric currents circulating on a surface of a torus along its meridians, which can be equivalent to the magnetic dipoles arranged head-to-tail along a circle
It was demonstrated that toroidal dipoles at 9.8 GHz were enhanced to produce Fano resonance and that the electromagnetically induced transparency (EIT) resonance appeared at higher frequency due to the destructive interference of electric dipoles and magnetic dipoles

Summary

INTRODUCTION

A toroidal dipole (TD), as the fundamental member of the toroidal multipole family, is the third family different from the traditional electric and magnetic dipoles. When destructive interference takes place between the different level energies of multipoles, the light–matter interactions are drastically altered such that an optically opaque medium becomes transparent.27 It has great potential applications in modulators and slow-light devices. It was demonstrated that toroidal dipoles at 9.8 GHz were enhanced to produce Fano resonance and that the EIT resonance appeared at higher frequency due to the destructive interference of electric dipoles and magnetic dipoles. Gupta and Singh considered introducing two mirrored asymmetric split-ring resonators (TASRs) to excite the toroidal response and realized high Q-factor Fano resonance in the terahertz range. In 2018, Xiang et al. proposed a low-loss planar metamaterial to enhance toroidal dipoles and verified a high Q-factor EIT resonance at 13.4 GHz. In 2019, two and three two-split-ring-resonators (TSRRs) were investigated by Sun et al.. The designed toroidal metamaterial with the high Qfactor Fano resonance and high transmission coefficient of EIT can have a significant influence on the areas of sensing and enhanced light–matter interactions and are expected to extend in terahertz and option ranges

DESIGN AND FABRICATION

CONCLUSION