A wideband hybrid plasmonic fractal patch nanoantenn

1. International INTERNATIONAL Journal of Electronics and JOURNAL Communication Engineering OF ELECTRONICS & Technology (IJECET), AND
ISSN 0976 –
6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 9, September (2014), pp. 01-08 © IAEME
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ISSN 0976 – 6464(Print)
ISSN 0976 – 6472(Online)
Volume 5, Issue 9, September (2014), pp. 01-08
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A WIDEBAND HYBRID PLASMONIC FRACTAL PATCH NANOANTENNA
1
Riffat T.Hussien1, Dheif I.Abood2
Department of Electrical Engineering, University of Technology, Baghdad, Iraq
1R.T.Hussein@uotechnlogy.edu.iq, 2dheifibraheem@yahoo.com
ABSTRACT
A proposed wideband plasmonic optical fractal patch antenna is presented for use in
intra/inter chip optical interconnects.The suggested plasmonic optical fractal patch antenna covering
3 optical communication bands: L-band (1565-1625nm), C-band (1530-1565nm), S-band (1460-
1530nm), and most of E-band (1360-1460nm).The proposed antenna has a promising future use in
inter and intra chip optical communications to eliminate electrical interconnection limitations such as
interconnect density, power consumption and also increasing data rate.The proposed antenna is a
rectangular tree-shaped fractal based.The performance of this antenna has been calculated using full
wave simulation CST Microwave software.The bandwidth is largely enhanced by the first and
second iterations rectangular tree-shaped external cut brick. The impedance bandwidth
( ) of the second iteration is about 38.5 THz, which is about 4 times greater the
bandwidth of initiator with a gain up to 7.5 dB and about 97% radiation efficiency throughout the
operational bandwidth.
1. INTRODUCTION
The nanoantenna, also known the optical antenna it is similar to the conventional antenna in
fact, it deals with electromagnetic waves except that nanoantenna operates in the Infrared (IR)
frequency portion of the electromagnetic spectrum. Antenna dimensions are comparable to the
operating wavelength so that in order to achieve resonance at IR frequencies antennas should be
shrinking to the nanoscale dimension. Nanoantenna can be defined as a nanometer scale metallic
structure which is capable of enhancing the optical radiation interaction with the matter [1].
At 1959 an imaginative paper entitled There's Plenty of Room at the Bottom was presented
by Richard Feynman. He talked about the problem of manipulating materials on a nanoscale
dimensions. This paper presented an inspired scientific ideas contributed to open researcher's eyes on
the nanotechnology a few decades later. Feynman discussed the problem of manipulating material on
the nanoscale. He wondered about the possibility of building nanoscale electric circuits and he also
posed the question is it possible to emit light from nanoantenna array, like we emit radio waves
from an antenna array to beam the radio programs to Europe? Which is similar to beam the light out

2. International Journal of Electronics and Communication Engineering Technology (IJECET), ISSN 0976 –
6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 9, September (2014), pp. 01-08 © IAEME
in a definite direction with highdirectivity [2-3]. Due to the advances in nanotechnology, optical
antenna attracts a lot of researchers' attention due to their several applications such as solar cell,
spectroscopy, microscopy, energy harvesting, etc. [3-7]. However, Conventional antenna problems
such as antenna impedance matching, gain and far field properties that are important issues when we
talk about an antenna for wireless communication did not examine a lot. At 2010, the two researchers
Andrea Alu and Nader Engheta suggested the optical antenna for optical wireless broadcasting links
as an alternative mechanism to the optical waveguide for inter and intra chip optical communication
[8]. In contrast to the great development in the microwave antenna field, studies in optical antennas
are relatively at its infancy. In addition to the difficulties in the fabrication of nanometer structures,
the design techniques of microwave circuits do not directly apply to the optical regime and the direct
scaled-down translation of conventional antenna theory and design is not possible, therefore the new
nano scaled-down antenna theory should take into account the different phenomena at the optical
frequencies [9].
Fractals were first defined by Mandelbrot as a way of classifying structures whose
dimensions were not whole numbers [10]. In the antenna design, the use of fractal shapes offer many
attractive features such as miniaturization, multiband frequency response or even wideband
characteristics, frequency independent (consistent performance over huge frequency range) and
reduced mutual coupling in array antenna, since for the same center-to-center spacing, the fractal
antennas have a larger edge-to-edge separation [11].
The idea of using fractal geometries in RF/Microwave antennas had been discussed in detail
and investigated both numerically and practically in many theses and papers [11-14]. Some of these
geometries have been particularly useful to miniaturize the antenna, while other designs aim at
incorporating multiband characteristics [14]. In contrast to microwave antennas, nano fractal antenna
only discussed in a few papers to benefit from fractal geometry features [15-16]. In additional to the
multiband or wideband characteristics and consistent performance over the operating frequency
band, the use of fractal concept in optical antenna give an additional miniaturization, and a potential
importance for reducing mutual coupling in the potential future high density plasmonic circuits for
instance nanoantenna solar cell application, the effective nanoantenna solar panels contain billions of
nanoantennas [17-18].
2
2.MICROSTRIP NANOANTENNA THEORY
A hybrid plasmonic patch nanoantenna was first introduced in [19]. The proposed design in
this paper is a development of the introduced hybrid plasmonic patch antenna for wideband purpose.
The hybrid plasmonic waveguide is a combining of plasmonic and dielectric waveguides [20]. In
hybrid plasmonic structure the TM surface plasmon wave is supported by metal/dielectric interface
couples with the TM mode dielectric waveguide and results a hybrid mode which is also a TM mode.
Figure l: Hybrid waveguide formation and the resulting hybrid mode from coupling of
dielectric and SP mode with silica height

3. at

4. International Journal of Electronics and Communication Engineering Technology (IJECET), ISSN 0976 –
6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 9, September (2014), pp. 01-08 © IAEME
From Figure 1 it is clear that the hybrid mode, power is mainly confined in the 50 nm low
(a) (b)
3
index material (SiO2 in the paper)
The surface plasmon theory [21] showed the validity of the transmission line model to predict
the impedance of the patch antenna [19]. Transmission line model represents the microstrip patch
antenna by two slots of width W and height h separated by a transmission line of length L [22]. The
hybrid TM mode of the hybrid structure approximated as a TEM, note that due to surface plasmon
resonance the ratio of x-component Ex (the direction along the waveguide) to the perpendicular z-component
Ez is given by the boundary condition relation:
!
Where Kx and Kz are the propagation constants in the x and z directions, #and $are
permittivties of metal (which can be gold or silver) and dielectric respectively. At the optical
frequencies the ratio of $ to # is very small, therefore the value of Ex is negligible compared with
the dominant Ez value. Consequently, the TM mode can be approximated to as a TEM mode.
Figure 2 shows the plasmonic patch nanoantenna initiator which is based on hybrid
plasmonic structure. The antenna consists of three materials stacked on top of each other (metal-low
refractive index material-high refractive index material) placed on the Buffer layer with low
refractive index. In this paper the materials are silver (Ag), silicon dioxide (%'() and silicon (%)
substrate and %'( as a buffer layer. The patch is center-fed by a hybrid plasmonic waveguide which
provides a better compromise between loss and confinement better than other plasmonic waveguide
types.
Figure 2: Plasmonic patch nanoantenna (a) 3D view (b) Cross-sectional view
The nanoantenna should be matched to the waveguide to get a good -10 dB%)) performance.
The impedance of patch antenna at the resonance condition (* +,
for the dominant TM010 mode) is
calculated as :
-./01//.
2
34/
2
56
7 6
89
25:;
=2
2
5
?@!(A 5!
Where 6 is the conductance, 89 the width of patch antenna and h is the height of %'( layer.

5. International Journal of Electronics and Communication Engineering
6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue
-B.C1DE4$1
-
F1GG
9, September (2014), pp. 01-
Where - is the characteristic impedance of air and
structure.
The effective refractive index is non
Technology (IJECET), ISSN 0976
dimensions (87 @H4IJ7 @KD7 @H4) have a significant effect
F1GG, propagation distance and power confinement
neff,increase in propagation distance and power confinement values. For the comparison purpose, the
dimensions for Figure2 Initiator have been considered equal
3. THE PROPOSED MODEL DESIGN
The first iteration of the
been constructed by cutting an external brick from the metal patch region and this process continue
until n iterations with following relation:
LMN O
QP!NLM
*MN
QP!N*M
Where LM and *M are the width and length of initiator respectively.
(a)
(c)
Figure 3: Shows the generation of plasmonic fractal patch nanoantenna. (a) First iteration, (b)
Second iteration, (c) Third iteration
4. RESULTS AND DISCUSSION
The FIT (finite integration method) is used with for simulation this antenna with CST
MICROWAVE STUDIO software
simulated for the different iterations. It is clear from Figure 4, as the number of iterations increase
the lower edge of the band is moved to the low frequency and the level of impedance matching over
the operating bandwidth is improved. It is also clear that the third iterative structure has minor effect
on the return loss result therefore, we stopped increasing iterations up to the third
4
F1GGis the effective refractive index of the
non-linearly dependent on structure dimensions. The
on three main parameters
confinement, for instance decreasing h
,to that presented structure in [19].
proposed wideband plasmonic optical fractal patch structure has
software. Figure 4 shows (Return loss). The proposed antenna has been
herefore, (b)
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R!
refractive index
hsio2 lead to decrease in
P!
!
thirditeration.

6. International Journal of Electronics and Communication Engineering
6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue
Frequency THz
Figure 4: Simulated
Technology (IJECET), ISSN 0976
9, September (2014), pp. 01-
results for the different iterations
The radiation pattern of this antenna has been simulated at the selected frequencies 196, 200
and 204 THz for the initiator and 190, 210 and 220 THz for the different iterations. A good
consistent radiation pattern has been
bi-directional broadside radiation pattern due to absence of ground plane with shifted main beam
about 15-20 degrees from (z-communication.
(a) f=186 THz
-axis) which is useful for multilayer optical inter/intra chip
Figure 5
(a) f= 190 THz
(b) f=190 THz (c) f=196 THz
5: 3-D Fairfield gain plot for the initiator
Figure 6: 3
obtained over the operating bandwidth. The antenna exhibits a
(b) f= 200 THz (c) f= 210 THz
3-D Fairfield gain plot for the first iteration
5
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7. International Journal of Electronics and Communication Engineering
6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue
(a) f= 190 THz
Technology (IJECET), ISSN 0976
9, September (2014), pp. 01-
(b) f= 200 THz (c) f= 210 THz
Figure 7: 3-D Fairfield gain plot for the second iteration
a) f= 190 THz
Figure 8: 3-
(b) f= 200 THz (c) f= 210 THz
-D Fairfield gain plot for the third iteration
Figure 9: Plot of maximum gain versus frequency for the Initiator, 1
6
st iteration, 2
3rd Iteration
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nd iteration and
)

8. International Journal of Electronics and Communication Engineering Technology (IJECET), ISSN 0976 –
6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 9, September (2014), pp. 01-08 © IAEME
7
5. CONCLUSION
A wideband hybrid plasmonic fractal patch nanoantenna with hybrid fed waveguide for
plasmonic application are proposed. The FIT (finite integration method) is used for simulation this
antenna with CST MICROWAVE STUDIO software. The simulated nano fractal antenna
demonstrated the possibility of translating the counterpart RF/Microwave fractal antennas to the
nanoscale with relatively the same features. The impedance bandwidth (%)) -10dB) has been
improved and extended by approximately 4 times by applying fractal concept to the nano patch
antenna. The designed antenna exhibits a broadside radiation pattern and provides a good consistent
radiation pattern has been obtained over the operating bandwidth.
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6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 9, September (2014), pp. 01-08 © IAEME
[17] Nanoantenna reinvents solar energy, [online] Engineering.missouri.edu. Available
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