Manipulating optical Tamm state in the terahertz
frequency range with graphene
Leyong Jiang (蒋乐勇)
1
, Jiao Tang (唐 娇)
1
, Qingkai Wang (王庆凯)
2
,
Yuexiang Wu (吴粤湘)
2
, Zhiwei Zheng (郑之伟)
1
, Yuanjiang Xiang (项元江)
2
,
and Xiaoyu Dai (戴小玉)
2,
*
1
School of Physics and Electronics, Hunan Normal University, Changsha 410081, China
2
International Collaborative Laboratory of 2D Materials for Optoelectronic Science & Technology of Ministry of
Education, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China
*Corresponding author: xiaoyudai@126.com
Received October 26, 2018; accepted December 14, 2018; posted online January 29, 2019
The optical Tamm state (OTS), which exists generally at the interface between metal and a dielectric Bragg
mirror, has been studied extensively in the visible and near infrared spectra. Nevertheless, OTS in the terahertz
(THz) region normally receives far less attention. In this Letter, we demonstrate the physical mechanism of OTS
at the interface between graphene and a dielectric Bragg mirror in the THz frequency band by applying the
transfer matrix method and dispersion characteristics. Based on such mechanisms, we propose an efficient
method that can precisely generate and control OTS at a desired angle and frequency. Moreover, we show that
the OTS is dependent on the optical conductivity of graphene, making the graphene–dielectric-Bragg-mirror a
good candidate for dynamic tunable OTS device in the THz frequency range.
OCIS codes: 160.4236, 250.5403.
doi: 10.3788/COL201917.020008.
The optical Tamm state (OTS) is a kind of surface wave
confined at the interface between two different media. It is
an optical analogue of electronic Tamm state predicted by
Tamm and firstly occurs at the boundary between two
periodical dielectric structures
[1,2]
. In the past few years,
OTS has attracted particular attention due to its poten-
tial applications in polariton laser fabrication and
enhanced light–matter interaction , as well as nanolasers,
thermophotovoltaic devices
[3–6]
, etc. Very recently, a
unidirectional all-OTS-based absorption switch has also
been reported
[7]
. In comparison with the conventional sur-
face waves [e.g., surface plasmon polaritons (SPPs)], OTS
can be excited directly for both the TE- and TM-polarized
waves and occur even at normal incidence
[8]
. Therefore,
OTS represe nts an excellent alternative for a variety of
optical elements with a functionality relying on surface
waves. Researchers have been intrigued by the possibility
of using different methods for realizing OTS through
various materials and configuration systems, such as
one-dimensional (1D) magnetophotonic structures
[9–11]
,
two-dimensional (2D) materials
[12,13]
, photonic crystal
(PC) heterostructures
[14–16]
, metal–Bragg-reflector struc-
tures
[17,18]
, and plasmonic waveguides
[7,19]
. It is well known
that the ability to create and manipulate OTS in a tera-
hertz (THz) frequency range is central to the development
of micro/nano optical components. It has been reported
that OTS can be controlled by an external magnetic
field
[20]
, anisotropic materials
[21]
, etc. However, there are
very few reports concerning tunable OTS, especially in
the THz frequency range.
Recently, graphene, a one-atom-thick 2D carbon
material, has attracted intensive interest due to its unique
optical and electrical properties
[22–29]
. Graphene in a micro/
nano structure is extremely promising for various opto-
electronic applications, including a graphene-based
broadband polarizer
[30]
, fiber laser
[31]
, metamaterials
[32–36]
,
etc. Besides, graphene is a zero bandgap material, and
its electromagnetic response can be realized from the
ultraviolet to THz range
[37]
. Therefore, graphene-based
optoelectronic devices could work over a much broader
wavelength range. Apart from being a special bandgap
structure, graphene is also attractive for the possibility
of controlling its carrier concentration via external gate
voltages or chemical doping. It means graphene’s conduc-
tivity can be continuously tuned in a broad frequency
range by shifting the Fermi energy. In addition, graphene
is intrinsically a semimetal with some metallic properties
under certain conditions
[38–40]
. Interesting questions arise as
to whether graphene can be used to realize OTS in a PC
structure or, more importantly, whether such a graphene–
PC composite structure could support the controllable
OTS. To answer these questions, in this Letter, we inves-
tigate theoretically the tunable OTS of a graphene–PC
structure in the THz frequency range using the modified
transfer matrix method
[41]
. It is found that the OTS in this
composite structure can be realized due to electric field
enhancement and the giant linear conductivity of gra-
phene. Furthermore, we have confirmed a way t o manipu-
late OTS by tuning the Fermi energy of graphene,
adjusting the incident angle, and varying the thickness
and permittivity of the top layer. Graphene-based control-
lable optical devices with intrinsic OTS allow us to find
potential applications in optical absorption, optical
sensing, and some other optoelectronics fields.
COL 17(2), 020008(2019) CHINESE OPTICS LETTERS February 10, 2019
1671-7694/2019/020008(6) 020008-1 © 2019 Chinese Optics Letters