This document provides an overview of optical nano antennas. It begins by defining nano antennas and their role in transmitting and receiving optical signals at the nanoscale. Next, it discusses the characteristics of metallic and dielectric nano antennas, including their directivity, radiation efficiency, gain, and ability to enhance localized electric fields. Applications mentioned include medicine, photovoltaics, spectroscopy, and near-field microscopy. The document concludes by introducing seebeck nano antennas for solar energy harvesting and discusses limitations of current photovoltaic technology.

1. Adviser : karim mohammad pour aghdam
author : Fatemeh Habibi
Nano Antenna

2. ● Introduction
● Characteristics of optical Nano antennas
● Metalic Nano antennas
● Dielectric Nano antennas
● Applications of optical Nano antennas
● Seebeck Nanoantennas for Solar Energy Harvesting
● simulation
● Resources
CONTENTS OF THIS PRESENTATION

3. What is an antenna?
The IEEE defines the antenna or aerial as “a means for radiating or receiving radio waves.”
The antenna is the transitional structure between free space and a guiding device.
An antenna is usually required to optimize or accentuate the radiation energy in some directions and
suppress it in others.
What is a Nano antenna?
the transmission and reception of optical signals by submicron and even nanometer-sized objects .
The sources and detectors of radiation in Nano-optics are Nano elements themselves.
The receiving Nano antenna is a device effectively converting incident light (optical frequency
radiation) into a strongly confined field. The transmitting antenna converts the strongly confined field
in the optical frequency range created by a certain (weakly emitting or almost Nonemitting) source
into optical radiation.
INTRODUCTION

4. Incident light on the antenna causes electrons in the antenna to move back and forth at the
same frequency as the incoming light. This is caused by the oscillating electric field of the
incoming electromagnetic wave.
The movement of electrons is generate alternating current in the antenna circuit
The wavelengths in the solar spectrum range from approximately 0.3-2.0 nm.
Thus, in order for a rectifying antenna to be an efficient electromagnetic collector in the solar
spectrum, it needs to be on the order of hundreds of nm in size.
THE THEORY OF NANO ANTENNA

5. A transmitting Nano antenna, like its classical analog, has to redistribute the electromagnetic energy in
space. The receiving Nano antennas designed to effectively excite quantum detectors of radiation
(hereinafter called detectors) that absorb only the small power of radiation incident on them due to their
extremely small size compared with the wavelength. A Nano antenna creates a strongly localized field
near the detector and thereby markedly enhances the power being detected. Moreover, a receiving
Nano antenna has the property of directivity that depends on specific practical applications of the
device.
CHARACTERISTICS OF OPTICAL NANO ANTENNA
Principal applications of Nano antennas (exemplified by a dipole). Near
field (a) or waveguide mode (b) transformation into freely propagating
optical radiation; (c, d) illustrate a reception regime.

6. Directivity : The directivity diagram is a real positive function coinciding in the spherical
coordinate system (𝜃, 𝜑) with the Poynting vector distribution (directivity diagram in terms of
intensity) in the far radiation zone (𝑟 ≫ 𝑙𝑎𝑚𝑏𝑑𝑎).
Radiation efficiency, directivity, and gain
A Nano antenna operating as a transmitter is characterized by the radiation efficiency, directivity, and gain.
(Color online) Typical directivity diagrams. (a) Electric or magnetic
dipole is small compared with the emitted wavelength, (b) Huygens
element, and (c) Yagi±Uda antennas.
𝐷 𝜃, 𝜑 =
4𝜋𝑝(𝜃, 𝜑)
𝑃𝑟𝑎𝑑

7. Gain :The radiation efficiency and directivity are related to one more antenna characteristic,
called antenna gain.
Efficiency : Dissipative losses in the material of elements of a nanoantenna are inevitable
during its operation. The level of these losses is characterized by the quantity called the
radiation efficiency.
A Nano antenna operating as a transmitter is characterized by the radiation efficiency, directivity, and gain.
Radiation efficiency, directivity, and gain
𝜀 𝑟𝑎𝑑 =
𝑃𝑟𝑎𝑑
𝑃𝑟𝑎𝑑 + 𝑃𝑙𝑜𝑠𝑠
𝐺 = 𝜀 𝑟𝑎𝑑 𝐷

8. CHARACTERISTICS OF NANO ANTENNA AS A RECEIVER
For a detector described in the dipole approximation, the absorption cross section can be written
out in the form
𝜎 = 𝜎0
(𝑛 𝑝 𝐸)2
(𝑛 𝑝 𝐸0)2
Where 𝜎0 is the absorption cross section in the absence of a Nano antenna, 𝑛 𝑝 is the
orientation of the absorbing dipole, and 𝐸 and 𝐸0 are the electric field strengths at the point of
detector placement in the presence and absence of the Nano antenna, respectively.
the absorption cross section of a detector depends not only on its own cross section 𝜎0 in the
absence of a Nano antenna but also on the quantity:
𝛿 𝑒
=
𝐸
𝐸0
which is termed the enhancement factor of the confined electric field. This quantity marks the
degree of difference between the absolute strength |E| of the electric field at a given point in the
presence of a Nano antenna and its value |E0| in the absence of a Nano antenna.

9. 𝛿 𝑚
=
𝐻
𝐻0
The principle of reciprocity that often simplifies the solution of many problems means in particular that
a Nano antenna operating as a transmitter is equally capable of acting as a receiver. In other words,
its functional characteristics in the reception and transmission regimes must be related. Specifically,
the application of the reciprocity theorem allows the following useful expression to be obtained , which
establishes the relationship between the reception and transmission regimes of the Nano antenna
𝑃𝑒𝑥𝑐(𝜃, 𝜑)
𝑃𝑒𝑥𝑐
0
(𝜃, 𝜑)
=
𝑃𝑟𝑎𝑑
𝑃𝑟𝑎𝑑
0
𝐷(𝜃, 𝜑)
𝐷0(𝜃, 𝜑)
In this expression, 𝑃𝑒𝑥𝑐(𝜃, 𝜑) and 𝑃𝑒𝑥𝑐
0
(𝜃, 𝜑) are the powers absorbed by the detector in the
presence and absence of a Nano antenna. 𝑃𝑟𝑎𝑑 and 𝑃𝑟𝑎𝑑 are integrated powers emitted by this
dipole, while 𝐷(𝜃, 𝜑) and 𝐷0
(𝜃, 𝜑) are directivities in the presence and absence of the Nano
antenna.
CHARACTERISTICS OF NANO ANTENNA AS A RECEIVER

10. Metallic Nano antennas
The history of the development of Nano antennas goes back to the work of Edward Hutchinson Synge,
who was the first to suggest using metallic nanoparticles for optical field confinement in 1928. In 1985,
John Wessel showed that a metallic nanoparticle behaves as an antenna. He revealed that the
presence of a single plasmonic particle makes it possible to overcome the diffraction limit in the
resolution of optical devices and to predict their resolving power up to 1 nm.
Some Types of metallic Nano antennas:
Plasmonic monopole Nano antenna
Plasmonic dimer Nano antennas / dipole Nanoantennas
Plasmonic bowtie Nano antennas
Plasmonic Yagi-Uda antennas

11. Metalic nano antennas

12. Metalic nano antennas

13. Dielectric Nano antenna
Unlike metallic Nano antennas made from an opaque material having plasmonic properties in
the optical range, dielectric Nano antennas are fabricated from optically transparent materials.
Their resonant response is related to the formation of an effective resonator inside the particle.
The antennas based on semiconducting particles are also called dielectric Nano antennas,
because semiconductors are sufficiently transparent in the visible frequency range.
Why are dielectric Nano antennas of interest to researchers? First, dielectric and many
semiconductor materials are characterized by notably low dissipative losses in the optical range.
Second, there is a wavelength range in which a submicron dielectric particle of silicon (a material
with high permittivity) simultaneously exhibits electric and magnetic resonant responses .

14. The main problem facing modern solar power engineering is the development of thin-film solar
cells efficiently converting solar radiation to electric current and significantly reducing the cost
of the electric power thus produced, which is presently 2±3 times that of the power generated
by other sources .The employment of thin photosensitive films in solar cells may decrease the
cost of electric power by an order of magnitude compared with current values due not only to
the reduced consumption of refined semiconductors per unit cell area but also to the possibility
of fabricating ultrathin (less than 1 mm) semiconducting films on organic and/or polymer
substrates by roll-to-roll processing.
Effective therapy for malignant neoplasms is a major unresolved challenge in modern medicine. It may be addressed by
utilizing metallic nanoparticles, e.g., metal nanoshells introduced at the affected site to be irradiated with the
near-infrared light. Radiation causes heating of nanoparticles which transfer the heat to cancer cells and thereby
kill them.
Applications of Nano antennas
Medicine
Photovoltaics
Spectroscopy
Near-field
microscopy
The practical application of this effect for the creation of substrates to study biological samples
required control over rough surfaces with nanoscale accuracy, i.e., the construction of optical
antenna arrays.
Optical nanoantennas may find application as specialized probes in near-field microscopy and
spectroscopy. Classical near-field probes take advantage of light passage through a
subwavelength diaphragm (aperture probes) or the effect of electromagnetic field enhancement
near the tip of a metal needle (apertureless probes). The design of near-field probes based on
optical antennas is extremely complicated; sometimes, it is impossible to distinguish among them
on the basis of the presence or absence of an aperture

16. Photovoltaics
One way to get electricity is to burn a fuel
like oil or coal. But They are not renewable
fuels. Another way to make electricity uses
sunlight. Sunshine is free and never gets
used up. A little device called a solar cell can
make electricity right from sunlight. Solar
cells use certain wavelengths of visible light
to make electricity .They need to cover a big
area in order to make more electricity.

17. Photovoltaics

18. Limitations of PV technology
• Band gap (heat loss, reduces efficiency)
• Expensive for large scale (multi junction)
manufacturing
• PV is operational only during daylight hours.
• Delivers DC power
• Low efficiency
• Requires direct incidence(perpendicular to surface) of
solar radiation for optimum efficiency.

19. Seebeck Nano antennas for solar energy harvesting
A successful incorporation of Nano antennas into photovoltaic technology relies on the
implementation of an efficient retrieving mechanism, currently non-existent. Nano antennas
coupled to high-speed rectifiers (known as “Rectennas”), based on tunnel barriers, have been
extensively explored during the last years as optical harvesting devices. In spite of the high
theoretical efficiency they can reach, Rectennas exhibit low efficiencies due to the poor
performance of the current rectifiers at optical frequencies .
They suggested a device which combines the use of Nano antennas with the thermoelectric
properties of their metallic interfaces (in order to recover such energy). The proposed devices
consist of metallic thermocouples shaped as Nano-antennas (Seebeck Nano antennas) sized to
resonate to mid-infrared wavelengths. They show by means of simulations that these devices work
by exploiting the temperature gradient caused by the resonant currents in the structures, which in
turn generate a dc voltage VOC by Seebeck effect at their “open ends” ; hence defining a
mechanism to harvest the optical energy.

20. Dipole Nano antenna
In this section I design and simulate a dipole Nano antenna with CST . The structure consists
of a ground plan which is covered with gold and a silicon dioxide as a substrate and a dipole
with gold materials. The simulation domain is 900*900 nano meters. Width of the dipole is 120
nm and gap has 10 nm values, also length of the dipole is 700 nm. Gold ground plan is due to
increase gain and the directivity of the antenna.
Simulations

21. Patch Nano antenna
My second simulation goes to patch Nano antenna using graphene as patch
material. Why graphene? Graphene is a firm candidate to become “the silicon of
the 21st century” due to its unique electronic properties: Very high electron
mobility, Very high speed switching devices, Very high sensitivity (all atoms
exposed) . The main property of graphene‐based Nano antennas is that the EM
wave propagation speed can be up to 100 times lower than in the free space or in
conventional materials. The antenna consists of 3 components 1- ground
(PEC),2-dielectric (TLX), 3-patch (Graphene).

22. RESOURCES
1. Balanis C A Antenna Theory: Analysis and Design (New York: Harper & Row, 1982)
2. Optical nanoantennas A E Krasnok, I S Maksymov, A I Denisyuk, P A Belov, A E
Miroshnichenko, C R Simovski, Yu S Kivshar
3. Schelkunoff S A, Friis H T Antennas: Theory and Practice (New York: Wiley, 1952)
4. Klimov V Nanoplasmonics (Singapore: Pan Stanford Publ., 2011)
5. Novotny L, Hecht B Principles of Nano-Optics (Cambridge: Cambridge Univ. Press, 2006)
6. Stockman M I Opt. Express 19 22029 (2011)
7. Kneipp K, Moskovits M, Kneipp H (Eds) Surface-Enhanced Raman Scattering: Physics and
Applications (Berlin: Springer, 2006)
8. Novotny L Phys. Today 64 (7) 47 (2011)
9. Bharadwaj P, Deutsch B, Novotny L Adv. Opt. Photon. 1 438 (2009)
10. Wessel J J. Opt. Soc. Am. B 2 1538 (1985)
And more…..

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THANKS!
Do you have any questions?
Fatemeh.habibi75@ut.ac.ir
Tehran university