Tunable enhanced optical absorption of graphene using plasmonic perfect
absorbers
Yijun Cai,
1,2
Jinfeng Zhu,
2,a)
and Qing Huo Liu
3
1
Institute of Optoelectronic Technology, Department of Electronic Engineering, Xiamen University,
Xiamen 361005, China
2
Institute of Electromagnetics and Acoustics, Department of Electronic Science, Xiamen University,
Xiamen 361005, China
3
Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708, USA
(Received 15 November 2014; accepted 19 January 2015; published online 29 January 2015)
Enhancement and manipulation of light absorption in graphene is a significant issue for
applications of graphene-based optoelectronic devices. In order to achieve this purpose in the visi-
ble region, we demonstrate a design of a graphene optical absorber inspired by metal-dielectric-
metal metamaterial for perfect absorption of electromagnetic waves. The optical absorbance ratios
of single and three atomic layer graphene are enhanced up to 37.5% and 64.8%, respectively. The
graphene absorber shows polarization-dependence and tolerates a wide range of incident angles.
Furthermore, the peak position and bandwidth of graphene absorption spectra are tunable in a wide
wavelength range through a specific structural configuration. These results imply that graphene in
combination with plasmonic perfect absorbers have a promising potential for developing advanced
nanophotonic devices.
V
C
2015 AIP Publishing LLC.[http://dx.doi.org/10.1063/1.4906996]
Graphene, a monolayer of carbon atoms in a two-
dimensional honeycomb lattice, has been shown to possess
exceptional electrical and optical properties for developing
advanced nanoelectronic and nanophotonic devices.
1
Particularly, research of graphene with a thickness of 3.4 A
˚
has boosted the development of advanced optics from nano-
optics to angstrom-optics. In the terahertz and infrared regions,
graphene with appropriate doping can generate surface plas-
mon polaritons (SPPs) and lead to strong light-graphene inter-
actions.
2
In contrast, in the visible and near-infrared range,
graphene does not support SPPs and acts as a lossy dielectric
material with wavelength-independent absorption.
3
Over the
past few years, several graphene-based optoelectronic devices
have been demonstrated, such as photodetectors, optical mod-
ulators, and photovoltaic cells.
4–6
However, in the visible and
near-infrared range, suspended graphene only absorbs about
2.3% of light at normal incidence due to its conical electronic
band structure,
7
and it does not show spectral selectivity
because of wavelength-independent absorption. This property
is promising for developing flexible transparent electrodes, but
the poor light-graphene interaction limits its further applica-
tions in optoelectronic devices. In order to enhance the light-
graphene interaction, conventional plasmonic nanostructures
based on noble metals can be combined with graphene for
developing novel nanophotonic devices with high perform-
ance.
8
Therefore, a systematic structural design in combina-
tion with electromagnetic simulation is quite essential in order
to enhance the light-graphene interaction and manipulate the
optical spectra of graphene-metal hybrid nanostructures.
In view of the ultra-thin physical structure of graphene,
we propose to take advantage of the nanostructure of a metal-
dielectric-metal (MDM) perfect light absorber, which demon-
strates tunable zero reflectance due to effects of a plasmon
guided mode within an extra small dielectric gap.
9–11
Therefore, in this paper, we discuss the design of a nanostruc-
ture of metal/dielectric/graphene/dielectric/metal (MDGDM)
to enhance and manipulate the light-graphene interaction in
the visible region. Compared with other plasmonic nanostruc-
tures for graphene absorption enhancement,
12,13
the proposed
nanostructure provides extraordinarily large absorption
efficiency.
The MDGDM nanostructure consists of periodic gold
nanoribbons on a SiO
2
layer coated with graphene supported
by a flat gold substrate, and the graphene is sandwiched
between two hexagonal boron nitride (h-BN) layers, as illus-
trated in Fig. 1. The geometry of the gold nanoribbon is
FIG. 1. Schematic drawing of an MDGDM nanostructure. The symbols d
and p correspond to the thickness of the SiO
2
dielectric layer and periodic
spacing of the gold nanoribbons, respectively.
a)
Author to whom correspondence should be addressed. Electronic mail:
nanoantenna@hotmail.com
0003-6951/2015/106(4)/043105/5/$30.00
V
C
2015 AIP Publishing LLC106, 043105-1
APPLIED PHYSICS LETTERS 106, 043105 (2015)
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
218.193.57.47 On: Fri, 06 Feb 2015 05:06:33