A Tunable Dual-Band and Polarization-Insensitive Coherent Perfect Absorber Based on Double-Layers Graphene Hybrid Waveguide

Xin Luo,Jian-Ping Liu,Yan-Hong Zhou,Ling-Ling Wang,Qi Lin,Si-Qi Li,Zhi-Min Liu,Zi-Qiang Cheng,Xiang Zhai

doi:10.1186/s11671-019-3155-z

Abstract

A suspended monolayer graphene has only about 2.3% absorption rate in visible and infrared band, which limits its optoelectronic applications. To significantly increase graphene’s absorption efficiency, a tunable dual-band and polarization-insensitive coherent perfect absorber (CPA) is proposed in the mid-infrared regime, which contains the silicon array coupled in double-layers graphene waveguide. Based on the FDTD methods, dual-band perfect absorption peaks are achieved in 9611 nm and 9924 nm, respectively. Moreover, due to its center symmetric feature, the proposed absorber also demonstrates polarization-insensitive. Meanwhile, the coherent absorption peaks can be all-optically modulated by altering the relative phase between two reverse incident lights. Furthermore, by manipulating the Fermi energies of two graphene layers, two coherent absorption peaks can move over a wide spectrum range, and our designed CPA can also be changed from dual-band CPA to narrowband CPA. Thus, our results can find some potential applications in the field of developing nanophotonic devices with excellent performance working at the mid-infrared regime.

Highlights

As a crucial issue for nanophotonics and optoelectronics, efficient light-matter interaction has widely caused concerns in recent years [1, 2], in the atomically thin two-dimension (2D) materials
By manipulating the Fermi energies of two graphene layers, two coherent absorption peaks can move over a wide spectrum range, and our designed coherent perfect absorber (CPA) can be changed from dual-band CPA to narrowband CPA
Since the graphene-based CPA is in the symmetry environment, the combined reflection and transmission coefficients can be expressed as r = η and t = 1 + η, respectively, where η is the self-consistent amplitude related to the graphene hybrid waveguide

Summary

Introduction

As a crucial issue for nanophotonics and optoelectronics, efficient light-matter interaction has widely caused concerns in recent years [1, 2], in the atomically thin two-dimension (2D) materials. As a prototypical 2D material, graphene can interact with light in a wide (ultraviolet to terahertz) wavelength range. The optical bandgap of graphene can be opened up by doping or using the other special methods, which results. Among these devices based on graphene, optical absorber takes an important role in the field of developing advanced optoelectronic devices, such as solar energy-trapping devices and emitters. As mentioned above, most of these absorbers are focused on the terahertz and infrared regimes, because graphene with special processes can excite SPPs, leading

Methods

Results

Conclusion