Plasmonic analog of electromagnetically induced transparency in nanostructure graphene

Xi Shi,Dezhuan Han,Yunyun Dai,Yong Sun,Hong Chen,Zongfu Yu,Xiaohan Liu,Jian Zi

doi:10.1364/oe.21.028438

Abstract

Graphene has shown intriguing optical properties as a new class of plasmonic material in the terahertz regime. In particular, plasmonic modes in graphene nanostructures can be confined to a spatial size that is hundreds of times smaller than their corresponding wavelengths in vacuum. Here, we show numerically that by designing graphene nanostructures in such deep-subwavelength scales, one can obtain plasmonic modes with the desired radiative properties such as radiative and dark modes. By placing the radiative and dark modes in the vicinity of each other, we further demonstrate electromagnetically induced transparency (EIT), analogous to the atomic EIT. At the transparent window, there exist very large group delays, one order of magnitude larger than those offered by metal structures. The EIT spectrum can be further tuned electrically by applying a gate voltage. Our results suggest that the demonstrated EIT based on graphene plasmonics may offer new possibilities for applications in photonics.

Highlights

Optical analogs of electrically induced transparency (EIT) in atomic systems have been proposed in a variety of optical structures [1,2,3,4,5,6]
Plasmonic modes in graphene nanostructures can be confined to a spatial size that is hundreds of times smaller than their corresponding wavelengths in vacuum
By placing the radiative and dark modes in the vicinity of each other, we further demonstrate electromagnetically induced transparency (EIT), analogous to the atomic EIT

Summary

Introduction

Optical analogs of electrically induced transparency (EIT) in atomic systems have been proposed in a variety of optical structures [1,2,3,4,5,6]. Plasmons in a single graphene layer surrounded by two dielectrics can be approximately described by ω = 4αcEF k / (ε1 + ε2 ) [12,13,14], where ω is the angular frequency, k is the wave vector, EF is the Fermi energy of the graphene layer, α is the finestructure constant, ħ is the reduced Planck constant, c is the speed of light in vacuum, and ε1 and ε2 are the dielectric constants of the two dielectrics Such a dispersion relation shows two unique features. For a plasmon mode with a frequency of 20 THz (corresponding to a wavelength of 15 μm in vacuum) supported by a graphene layer in air the corresponding plasmon wavelength is smaller than 400 nm for EF = 0.15 eV Such small modal sizes may open up new opportunities for engineering optical modes at a deep-subwavelength length scale

Methods

Results

Conclusion