Plasmonics
https://doi.org/10.1007/s11468-019-01031-7
Plasmonic Micro-Antenna Characteristics Using Gold Grating
Embedded in a Panda-Ring Circuit
A. E. Arumona 1,2,3 & I. S. Amiri 4 & P. Yupapin 1,2
Received: 6 June 2019 / Accepted: 3 September 2019
# Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract
An investigation of the plasmonic micro-antenna characteristics using an optical modified add–drop multiplexer embedded gold
grating is proposed. A device consisting of a main microring and two nano-ring phase modulators is known as a Panda-ring
resonator. A gold grating is embedded at the main ring center to induce plasmonic polariton, which is the plasmonic wave that
oscillates with plasma frequency. At the resonance, the whispering gallery mode (WGM) of propagation light fields can be
obtained by controlling the two suitable side ring parameters, from which the plasma resonant frequency is obtained by the
graphical method called the Optiwave program. In manipulation, the light source with the wavelength of 1.55 μm is fed into the
system. The input power was varied from 1 to 10 mW, from which the Bragg wavelength at the resonant peak is employed for all
calculations. The directivity and gain of the plasmonic micro-antenna of 2.8 mW (4.47 dBm) and 0.78 mW (− 1.08 dBm) are
obtained. The motivation for this study is that the plasmonic micro-antenna enhances the performance of optical/communication
devices due to its extraordinary properties. The key finding is the operation of the plasmonic micro-antenna at optical frequencies
using the Panda-ring circuit, which has dual modes for wireless and cable connections. In applications, the large-area antenna
(multi-antennas) has the potential for atom, cell, and brain communication network investigations; regarding the linear relationship trend of the output gain, the use of the circuit for application in sensors is also possible.
Keywords Plasmonic antenna . THz frequency . Add–drop multiplexer . Panda ring . Gold grating
Introduction
A plasmonic antenna is made of plasmonic materials such as
silver, gold, and grapheme, which usually is a nanostructure
* P. Yupapin
preecha.yupapin@tdtu.edu.vn
A. E. Arumona
186219005@student.tdtu.edu.vn
I. S. Amiri
amiri@bu.edu
1
Computational Optics Research Group, Advanced Institute of
Materials Science, Ton Duc Thang University, District 7, Ho Chi
Minh City, Vietnam
2
Faculty of Applied Sciences, Ton Duc Thang University, District 7,
Ho Chi Minh City, Vietnam
3
Division of Computational Physics, Institute for Computational
Science, Ton Duc Thang University, Ho Chi Minh City 700000,
Vietnam
4
Division of Materials Science and Engineering, Boston University,
Boston, MA 02215, USA
metal that can be referred to as the optical (dielectric) nanoantenna [1–6]. The plasmon wave at nanoscale makes use of
the interaction between light and free electrons in the plasmonic metal. They convert optical radiation that is freely
propagating into localized energy and vice versa [7–11]. The
plasmonic antenna’s design is different from that of the RF
and microwave antenna since it operates in the high-frequency
regime which is the optical frequency. The electromagnetic
field penetrates the metal at a depth called skin depth that
results in increasing the inertia as shown by the conduction
electrons when an illumination occurs, leading to a delay in
their response. The electrons are modeled by the light that
strikes the metal and couples to the electron plasma, which
leads to the formation of rapid oscillation. The effect of the
metallic electrons only responds to the effective wavelength,
which is a function of the plasma wavelength and incident
beam wavelength [12–15]. Plasmonic antennas are also applied in the field of nanoscale imaging and spectroscopy
[16–21], where the efficiency of light emission and absorption
can be increased by plasmonic antennas [22–24]. They are
also applied in the field of coherent ultrafast nanophotonics,
where the fast emission can be used in femtosecond on-chip
Plasmonics
Fig. 1 The microplasmonic antenna circuit: a a Panda-ring resonator with gold embedded inside the center ring; b a device fabrication structure, where
Ein, Eth, Eadd, and Ed are the input port, throughput port, add port, and drop port. Rd, R1, and R2 are radii. ĸ1, ĸ2, ĸ3, and ĸ4 are the coupling coefficients
electronics [25], and so much more. Several researchers reported different designs of plasmonic antennas. For example,
Dattoma et al. [26] used a gold nanorod placed on top of
gallium nitride substrate, and studied the dependence of the
gold nanorod’s resonant wavelength. In this case, the optical
nanoantenna is formed in the wavelength from 500 to
1400 nm. Sasmita et al. [27] studied the performance of
graphene plasmonic antenna, where the graphene is placed
on top of SiO2/Si substrate, in which the frequency ranging
from 2.56 to 4.98 THz is studied. Gaetano et al. [28] designed
a Vivaldi plasmonic antenna placed on a silicon substrate for
wireless optical communication, wherein the performance of
the plasmonic antenna in the wavelength of 1550 nm is reported. Seyed et al. [29] designed a graphene plasmonic antenna placed on the gallium arsenide substrate, in which
Table 1 The selected parameters
of the system used in the
simulation
radiation efficiency of this antenna in the frequency of 1–
5 THz was studied and obtained. Vincenzo et al. [30] studied
the scattering efficiency of the plasmonic antenna made of a
semiconductor in the frequency ranging from 1 to 3 THz, in
which the near-field enhancement was studied as well.
Whispering gallery mode of light is a phenomenon where
light waves are trapped inside a ring or microring. The effect
of nonlinearity in whispering gallery mode made it have many
applications ranging from sensing to optical wireless communication [31]. Yang and Li applied the concept of whispering
gallery mode in plasmonic nanocavity that is made of gold
nanospheres and quantum dots to study the dependence of
light emission on whispering gallery mode [32]. Ernst and
Albert made use of plasmonic whispering gallery cavities
made of gold in studying the surface plasmon resonant modes
Parameters
Symbols
Values
Units
Input signal power (Gaussian pulse)
Si-linear waveguide length
Si center ring radius
GaAs small ring radius
GaAs small ring radius
Gold thickness
Gold dielectric constant [40]
Gold permittivity [40]
Gold length
Gold refractive index [40]
P
L
R
R1
R2
d
ϵo
ϵ
L
n
1.0–10.0
16
3
1.12
1.12
0.1
6.9
10.0
0.5
1.80
mW
μm
μm
μm
μm
μm
Coupling coefficient
Refractive index Si [41]
GaAs linear refractive index [42]
GaAs nonlinear refractive index [42]
Input light wavelength
Waveguide core effective area [41]
Waveguide loss
Grating period
κ
n
n0
n2
λ
Aeff
α
Λ
0.5
3.42
3.14
1.3 × 10−13
1.55
0.30
0.50
0.50
μm
–
–
m2 W−1
μm
μm2
dB (mm)−1
μm
Plasmonics
Fig. 2 The input power is 10 mW, where the used parameters are center
wavelength (1.55 μm), RSi (3 μm), and R1 = R2 (1.12 μm). The other used
parameters are given in Table 1: a the graphical result, b the propagation
beam. DFT, the discretized Fourier transform used in getting the response
(spectral response) of a single wavelength from a time series
of the plasmonic whispering gallery cavities which have potential applications in optical nano-antennas [33]. Trong and
Chang studied the whispering gallery mode resonances in
ZnO microspheres embedded with gold nanoparticles and
how these WGM resonances can be enhanced [34].
The Optiwave program was used to study the system leading to the formation of whispering gallery modes that have the
advantage of dual-mode operations: (i) the wireless link called
light fidelity (LiFi) network and (ii) the cable network via the
fiber optic network. For simplicity, the used parameters extracted from the Optiwave program will be used in the Matlab
program to study the plasmonic antenna’s directivity and gain
as a wireless antenna for wireless communication. The related
background is also given.
The response in metals such as gold is described by the dielectric function that is frequency dependent. By using the
Drude model [35, 36], the frequency-dependent dielectric
function of the solid (gold) is given by:
ϵðωÞ ¼ 1−
ne2
ϵ0 mω2
ð1Þ
Where ϵ0 is the relative permittivity; n, e, and m are the
electron density, charge, and mass, respectively. ω is the angular frequency. The resonant frequency (ωp) is called the
plasma frequency.
The dielectric function changes its sign from negative to a
positive and real part of the dielectric function to 0, where the
plasma resonant frequency is expressed by:
−1= 2
Background
ne2
ωp ¼
ϵ0 m
In metals, conduction electrons respond fast when they are
illuminated by light or excited by electromagnetic radiation
which can cause the electrons to move quasi-freely in metals.
The surface plasmon (SP) wave is a wave that travels in the
direction of the metal–dielectric interface and in the orthogonal direction to it while decaying evanescently [37], where the
Fig. 3 Plot of the output (wavelength domain) at the input signal, drop
port signal, and throughput port signal and the WGM at the center system
(grating)
Fig. 4 Plot of the output (frequency domain) at the input signal, drop port
signal, and throughput port signal and the WGM at the center system
(grating)
ð2Þ
Plasmonics
Fig. 5 Plot of the output (time domain) at the input signal, drop port
signal, and throughput port signal and the WGM at the center system
(grating)
Drude model accounts for free electron conduction of the
bound electrons in the metal. The SP wave oscillation is obtained by using an electric field that is the longitudinal oscillation. By using the Maxwell equations, the TM polarization
and exponential decay of the electric field are obtained. In this
work, the resonant plasma frequency is obtained from the
graphical result, where the WGM output at the resonant frequency is obtained. The input electric field in the system in
Fig. 1 is given by Eq. (3) [38].
EZ ¼ E0 e−ikz z−ωt
ð3Þ
Where E0 is the initial electric field amplitude; kz ¼ 2π
λ is the
wavenumber in the direction of propagation (z-axis); λ is the
input light source wavelength. ω = 2πγ is the angular frequency, γ is the linear frequency, and t is time.
The relationship between the plasma polarization density
(P) and the electric field (E) is given by Eq. (4):
P¼−
ne2
E
mω2
ð4Þ
Different kinds of the microcircuit design used gold nanorods to study various parameters of the plasmonic antennas
[29]. The plasmonic gold is embedded at the center ring,
which consists of two bus waveguides and two smaller rings
attached side by side to a center ring. The output fields can be
described by the following equations [39]:
E th ¼ m2 E in þ m3 E add
Fig. 6 Plot of the WGM at the
center system with input power is
10 mW: a WGM in wavelength
domain, b WGM in frequency
domain. a Bragg wavelength is
1.60 μm. b Calculation peak
plasma frequency is 1.20 ×
1015rads−1
ð5Þ
Fig. 7 Plot of the directivity and gain using the MATLAB program at the
center system
E drop ¼ m5 Eadd þ m6 Ein
ð6Þ
Where mi and the related terms are the constants and found
in the given references. Eth, Edrop, Eadd, and Ein are the
throughput, drop, add, and input ports, respectively. The whispering gallery mode of the Panda ring will be controlled by the
two side rings (phase modulators) at the resonant values, from
which the normalized intensities at the throughput port and
drop port are obtained.
The normalized output intensities of the system are shown
in Fig. 1, which are given by:
2
I th
Eth
¼
ð7Þ
I in
Ein
I drop
Edrop 2
¼
ð8Þ
I in
Ein
The initial input light source wavelength is λ. The induced
change of the coupling power within each nanograting depends on the grating dimension, which is related to the
Bragg wavelength and given by λB= 2ne⋀, where ne is the
effective refractive index of the grating in the waveguide, and
⋀ is the grating period. The other effect is the Kerr effect,
which is given by the refractive index equation, and whose
relationship is given as n = n0 + n2I = n0 + n2P/Aeff, where n0
and n2 are the linear and nonlinear refractive indices, respectively. I is the optical intensity and P is the optical power,
where Aeff is the effective mode core area of the device. For
Plasmonics
Fig. 8 Plot of the gain and the input power which varied from 1.0 to
10.0 mW based on Fig. 2, where the simulation data (dot) and the curve
fitting (solid line) are plotted, in which the linear trend is observed
the microring resonator, the effective mode core areas range
from 0.1 to 0.50 μm2.
Results and Discussion
From Fig. 1, the initial input light source with a wavelength of
1.55 μm is fed into the system via the input port. By using the
other selected parameters as shown in Table 1, the plasmonic
polaritons are generated at the resonance by the coupling light
(photons) into the gold grating structure and material, from
which the beam of the propagation wave with the Bragg
wavelength is formed at the center of the system. The plasmonic micro-antenna performed by the oscillating dipoles of
the polariton waves. The other output signals can also be obtained at the throughput and drop ports, where the required
information can multiplex/demultiplex to/from the add port/
drop port. In manipulation, firstly, the Optiwave FDTD 32 bit
version 12.0 [43] program is employed, in which light can be
Fig. 9 Smith chart of Fig. 7,
where a directivity and b gain are
plotted
trapped in the center ring at a particular wavelength and resonance. The grid size used is 0.045 for Δx, Δy, and Δz, respectively. The boundary condition of the anisotropic perfect
matched layer (APML) is applied, in which the number of
APML is 15 with a theoretical reflection coefficient of
1.0°× 10−12 and real tensor APML parameter of 1. The whole
dimension of the simulation model has 308, 55, and 353 mesh
cell sizes, in x, y, and z axes, respectively. From Fig. 2, the
whispering gallery mode output is observed at the center
wavelength of 1.60 μm, which is the wavelength shifted by
the Bragg grating. This trapping of light was made possible by
the nonlinearity/nonlinear effect exhibited by gallium arsenide
(GaAs) on the silicon center ring. The generated WGM beam
can be applied in wireless communication, from which the
plasmonic gold grating at the center ring can form the
electro-optic conversion, in which the dipole oscillation and
the wireless antenna can perform. The parameters extracted
from the first simulation using the Optiwave program were
used in the Matlab program to obtain the directivity and gain
of the wireless antenna manipulation. The wireless antenna
has a range of 1.2–1.90 μm and 170–250 THz in the wavelength and frequency domains, respectively. To confirm the
resonant results, the number of round trips was 20,000. By
using the electro-optic conversion of the Drude model, the
relationship between the plasmonic and electrical waves can
be obtained. Finally, dual-operation modes of the proposed
circuit can be achieved. In the applications, the input power
varied from 1 to 10 mW; the excitation signal is the Gaussian
pulse, with a suitable coupling coefficient of 0.5. To ensure the
accuracy and optimization of the study, all simulations including the Optiwave program that makes use of the FDTD algorithm and the Matlab program were done with a 32-GB RAM
high-performance computer. From the simulation, the input,
throughput, and drop ports, including the WGM signal in the
wavelength domain, frequency domain, and time domain, are
shown in Figs. 3, 4, and 5. The WGM resonant output plotted
with wavelength and frequency domains is shown in Fig. 6
Plasmonics
Fig. 10 The polar plot of Fig. 7: a
directivity and b gain
with the input power of 10 mW. The antenna directivity is a
required characteristic parameter. The gold grating is responsible for the shifting of the center wavelength of light at
1.55 μm to a wavelength called the Bragg wavelength at
1.60 μm and from the peak value of the intensity at the plasma
frequency of 1.20 × 1015rads−1 calculated using the relevant
equation. Therefore, the comparison of the directivity with
gain is shown in Fig. 7, with the input power of 10 mW. The
directivity and gain of 2.8 mW (4.47 dBm) and 0.78 mW (−
1.08 dBm) are obtained, respectively. The directivity is obtained when the plasmonic micro-antenna radiated power into a
propagation direction, which is calculated from the ratio of
beam propagation of the wave formed at the center of the
panda-ring circuit to the radiation intensity. The gain is calculated from the ratio of radiation intensity to the total input
intensity in the direction of the beam propagation of the wave.
In Fig. 8, the gain increases when the power is varied from 1 to
10 mW, in which the linearity trend is obtained [44, 45].
Directivity and gain are plotted in the Smith chart as well in
Fig. 9, which gives the frequency response of the plasmonic
micro-antenna in vector form rather than in scalar form and
also the reflection coefficient of the antenna. Figure 10 is the
polar plot of the directivity and gain, which gives the radiation
pattern of the plasmonic micro-antenna and used in determining the quantity of power radiated in any given direction. In
applications, the dual modes of application are as wireless and
cable connections, where the wireless can link by the shortrange light fidelity (LiFi) network via the WGM output as the
antenna operation, and the cable connection can connect to the
link via the device ports. Therefore, broad communication link
networks can perform, in an instant, and the transmitted signals can connect to the throughput port, while demultiplex and
multiplex signals can connect to the add and drop ports of the
circuit, respectively. During the operation, the LiFi transmission can link with the plasmonic micro-antenna, in which the
up- and downlinks can form the transmission with the network. Moreover, the use of plasmonic micro-antenna for atom
or molecule (cell) sensor communication can also be possible;
for example, it can be applied in the scheme of communication
known as the quantum cellular automata. The use of the proposed circuit for sensor application is also available, in which
the linear relationship of the obtained result convinces that it
can perform as a required sensor using a design circuit.
Conclusion
A microcircuit design for plasmonic antenna characteristics
studies is proposed, where the simulation results have shown
the confirmation that using such a circuit is promising for
micro-antennas. The knowledge of whispering gallery mode
of light and the nonlinear effect within the system is the key to
the investigation. The advantage is the proposed system can
have dual modes of applications, where it can be employed for
(i) LiFi or (ii) cable connections. Based on the Drude model,
the proposed circuit uses the electro-optic conversion of signals obtained by gold grating and plasmonic wave (polariton)
interaction. By using the simple method, the parameters are
extracted from the graphical method called Optiwave program
and employed in the Matlab program. The optimum result
shows that the highest directivity and gain of 2.8 mW
(4.47 dBm) and 0.78 mW (− 1.08 dBm) are achieved, respectively. The resonant plasma frequency of 1.20 × 1015rads−1 is
obtained. Moreover, the Panda-ring resonator has the nonlinear ability to use its nonlinearity effect, which is a unique
design that can have two inputs and outputs that lead to suitability for various applications. This design circuit can be used
for various applications, in an instant, for directivity and highfrequency range of wireless communication, micro-antenna
for atom (cell) sensors and communication, and quantum cellular automata.
Funding Information One of the authors (Mr. Arumona) received financial support from Ton Duc Thang University, Vietnam.
Plasmonics
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