Metamaterials

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Volume-04 ISSN: 2455-3085 (Online)
Issue-04 RESEARCH REVIEW International Journal of Multidisciplinary
April -2019 www.rrjournals.com [UGC Listed Journal]
RRIJM 2015, All Rights Reserved 664 | P a g e
Negative Index Materials: Metamaterials
Ms. Vandana Kaushik
Assistant Professor,School of Physical Sciences,Straex University, Gurugram (India)
ARTICLE DETAILS
ABSTRACT
Article History
Published Online: 15 April 2019
In the past few years, new advances in structured electromagnetic materials have given
growth to materials with negative refractive index, which have both negative dielectric
permittivity and negative magnetic permeability in some frequency ranges. These negative
refractive index materials exhibit exotic properties which are not easily achieved using
naturally occurring materials. This awareness of a negative refractive index opens up new
theoretical frontiers in optics, electromagnetism, physics, material sciences,
nanotechnology, engineering and many other branches of sciences. One much discussed
case is the concept of a perfect lens that allows imaging with sub wavelength image
resolution. According to researchers, controlling negative refraction will help in the
development of superlenses that magnify the objects too small to see with a conventional
optical microscope. Here in this paper we review the basic concepts and ideas of a negative
refractive index material.First we will present the ideas of Metamaterials, which enable to
design the new materials with negative dielectric permittivity, negative magnetic permeability
and negative refractive index then we will discuss the various types and applications of
metamaterials.
Keywords
Negative Refractive Index, Negative
refractive index materials,
Metamaterials, permittivity, permeability.
1. Introduction
1.1 What is negative refractive index?
Refractive index is recognized as ratio of the phase
velocity of a wave in a reference material (for light, we take
vacuum as reference material) to the phase velocity of the
wave in any another material. In almost entirely
undergraduates and graduate level texts on the topics of optics
or electricity and magnetism the refractive index of a material is
always expected to be positive. But nature has concealed
numerous great secrets from us, first described by Victor
Veselago a Russian Physicist in 1967 [1]. Veselago revealed
the unusual and interesting property that if material has
negative values of both of permittivity (ε < 0) and permeability
(µ < 0) then refractive index (ɳ = µ𝜀) of that material will also
be negative (ɳ < 0).When a wave travels into a material with a
negative refractive index then the direction of the phase
velocity of the wave will be opposite to the direction of incident
wave.
As we all areconversant with the definition of refractive
index, it is the ratio of velocity of light in vacuum to that of
velocity of light in any given medium. It is also known that the
ray of light bends on the way to the normal as the medium gets
denser. When light travels in any usual material medium, its
velocity gets slowed down. The amount up to which velocity of
light slowed down depends upon the refractive index „ɳ‟ of the
material. Light wave travelling from air to any ordinary material
like water many theoretical calculations and experiments have
shown that light ray bent as it enters into a new material, the
process is known as refraction.
Fig 1: Refraction of light wave through an ordinary medium with
positive refractive index.
Here Ɵ1 and Ɵ2 are the angles which incident and
transmitted rays makes with normal to the surface satisfying
Snell‟s law:
ɳ1 sinƟ1 = ɳ2 sinƟ2 (1)
Snell‟s law is still contentedeven when one of the materials
has negative refractive index but the direction of light ray is
mirror imaged about the normal to the surface as shown in fig
given below:

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RRIJM 2015, All Rights Reserved 665 | Page
Fig 2: When a ray of light coming from vacuum hits a
negative index material (right side), the refractive beam inside
the place is on similar aspect of the surface area typical as the
event beam. This's unlike the situation for regular positive
index materials (left side).
From the fig given below we can see the difference
between refraction and negative refraction.
Fig 3: Refraction versus Negative Refraction
1.2 What are negative index materials (NIM)?
Wikipedia defines a metamaterials as follows [2]:
A metamaterial is a material which gains its properties
from its structure rather than directly from its
composition.To distinguishesmetamaterials from other
composite materials; the metamaterial label is usually
used for a material which has unusual properties.
Meta implies beyond, which the title was given to materials
with negative refractive index because these substances are
beyond standard materials. The phrase of metamaterial was
provided by Rodger M. Walserin 1999, that defined
metamaterials as Macroscopic composites having a synthetic,
three dimensional, periodic cellular structure created to create
an enhanced combination, unavailable in nature, of 2 plus
responses.Another means of expressing the significance of the
growth is emphasizing the objective of metamaterials, that is
achieving material functionality beyond the limits of traditional
composites [three]. The very first Metamaterial proficient of
bending electromagnetic radiation is made by Dr. Smith and
the staff of his at the Faculty of California in 2000.A great deal
of current investigations were centered on a brand new
category of components referred to as left handed materials or
maybe negative index components, and they exhibit extremely
uncommon electromagnetic clasp and properties promise for
brand new unit uses. This most prominent home and that isn't
previously found is damaging refractive index. Negative-index
material (NIM) is a metamaterial whose refractive index for an
electromagnetic trend has a bad quality over several frequency
range.Metamaterials might possess qualities which are a lot
more apparent than those found in natural substance with good
refractive index. These metamaterials don't happen naturally.
They are able to just be fabricated artificially and for this main
reason, these substances are called metamaterials. The
special qualities of negative refractive index metamaterials
aren't influenced by the essential physical qualities of the
components of theirs, but by the design Materials and
distribution of the precise plans bundled in them.Negative
refractive index metamaterials may also be known as Left
Handed Metamaterials (LHM). Metamaterials could be meant
to display both magnetic and electric resonances which can be
distinctly tuned to transpire in frequency bands from megahertz
to terahertz frequencies, along with expectantly on the
noticeable area of the electromagnetic spectrum.
Veselago seen that the planar sheet of content of correct
material plus thickness parameter with negative refractive
index may be utilized as a lens.
Fig 4: Slab of Negative refractive index material can be
used as a perfect lens.
Veselago predicted the electromagnetic plane waves in a
medium having simultaneously detrimental permittivity and also
bad permeability[4], that propagate in a direction reverse to
which of the flow of power. This result follows not from the
trend equation that remains unaffected in the absence of
options but from the single Maxwell curl equations. The
Maxwell curl equation for the electric powered field gives a
clear cut "right hand" (RH) principle between the instructions of
the electric field' E', the magnetic induction' B' and also the
path of the propagation vector' k'. The guidance of energy flow,
provided by' E XH', forms a right handed product just if the
permeability is higher compared to zero. When the permeability
is unfavorable, the path of propagation is inverted with regard
to the direction of electricity flow, the vectors E, H, and also k
building a left handed system. Thus, Veselago pointed out such
substances as "left handed".
1.3 Types of Metamaterials:
There are various types of metamaterial explained as
follows [5]:
1.3.1 Electromagnetic Metamaterials:
Electromagnetic metamaterials are made up of conductive
particles and havetraces inside a dielectric matrix.
Thesemetamaterials have zero or even negative
permeability and/or permittivity. Kymeta,
MetamaterialTechnologies, Fractal antenna system,
Imperial Universityof and duke Faculty London are
definitely the recentfront runner of thethis type of
metamaterials. These metamaterials are now being
applied to the arena of microwave and also optics
including beam steerers,antenna radomes, lenses,
microwave couplers, modulators, as well bandpass filters.
Electromagneticmetamaterials greatly influence
theelectromagnetic waves with little wavelength as
opposed to the wavelength of electromagnetic radiation.
1.3.1 (a) Single Negative Metamaterials:These type of
electromagnetic metamaterials have either negative
permeability or negativepermittivity, but not both.

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RRIJM 2015, All Rights Reserved 666 | Page
1.3.1 (b) Double Negative Metamaterial:The
metamaterials which have both the negative permittivity
and negative permeability withthe negative refractive
index. These are also recognized as backward wave
media.
1.3.1 (c) Photonic Metamaterial:These types of
Electromagnetic metamaterials are designed to interact
with optical frequencies and arealso known as the optical
metamaterials. Photonic metamaterials have zero
refractive index. These metamaterials are the dynamic
area of study in the field of optics.
1.3.1 (d) Bi-isotropic and Bi-anisotropic Metamaterials:
Depending on the independent electric and magnetic
responses discussed by the parameters permittivity and
magnetic permeability, the electromagnetic metamaterials
are classified into double or single negativemeta materials.
In numerous instances of electromagnetic metamaterials,
the electrical field causes magnetic polarization as well as
the magnetic field comes an electric polarization. Such
media denoted as bi isotropic metamaterials since it shows
magneto electric coupling which is anisotropic and also
named as bi anisotropic.
1.3.2 Acoustic Metamaterials: These metamaterials are
ready from 2 plus materials with various bulk modulus plus
mass density. These types‟ of metamaterials have
negative highly effective mass density as well as bulk
modulus. The Faculty of Liverpool and Hong Kong
University of Technology and Science is definitely the
recent front runner in re-search of Acoustic metamaterials,
having excessive interest for their target uses of these
metamaterials as vibration damping, Anti sonar, wireless
energy transfer and seismic protection. These
metamaterials are theartificially designed metamaterial to
direct, operate and also regulate sound waves in gases,
solids, and liquid. Almost any kind of sound waves could
be managed by managing the mass density and also bulk
modulus of the acoustic metamaterials.
1.3.3 Mechanical Metamaterials: These are the artificial
composite metamaterial which consists of various types of
mechanical properties. Mechanical metamaterials have
negative Poisson‟s ratio, negative modulus of elasticity,
frictional properties and zero modulus of rigidity and are
made up of materials with a precise pored structure or
inclusion of secondary materials. The scientists of
HarvardUniversity and Northwestern University have a
great concern in the new research application of these
metamaterials in the area of aerospace and defense.
1.3.4 Tunable Metamaterials: They've power to randomly
change the frequency of a refractive index. An incident
electromagnetic wave offers varying response with such
metamaterials. The framework of these metamaterials can
be transformed in real time which helps make it easy to
reconfigure an unit during operation [six]. Tuning in the
near infrared range is achieved by altering the permittivity
of nematic liquid crystal. These metamaterials could be
tuned from bad index values, to zero index or maybe good
index values, additionally to this particular damaging index
values might be enhanced or perhaps decreased.
Negative Refractive Index Materials as Perfect Lenses:
GREAT thinkingis usually both graceful and simple. Such
suggestion was produced by Sir John Pendry that an ideal lens
[seven], totally free from any type of loss or deformation of info,
may be created whether it wasprobable to constructa material
that had specific incredible properties. On November
seventeen, 2005 scientists showed animportant step towards
making such material for visible light.When a ray of light
crosses a fringe, like that between air along with a block of
glass, then the ray transformed its course. In the situation of
cup plus air, the light is bent towards the boundary. This
bending, together with utilizing a rounded exterior, is exploited
to create the standard lenses utilized in digicams, telescopes
and optical microscopes. These traditional lenses can't ever be
ideal because they often don't refocus the gentle rays which
originate from the item under examination in the form of
decaying waves. The image thus can't make up the info about
the item toted by these waves.
The rangeup to that the ray of light is bent is referred to as
the material's refractive index. This's partly based on the result
of the components on the electrical element of the partially by
and light material's reaction to the magnetic component. The
refractive index of the cup is aproximatelly 1.4; this's practically
solely determined by the power result of the cup. When the
light was bent far from the boundary, the material would've a
refractive index under a single. When the light was bent back
on itself, within the form of a hairpin, the refractive index will be
damaging. Sir John discovered that when the refractive index
were negative after that it will be easy to create a great lens.
His vision was very authentic he received a knighthood for it.
Geometrically, this thought isn't as tough to envisage as
shown diagram. In a material with a refractive index of -1, the
perspective of refraction of the gentle ray will be comparable to
the angle of incidence however in the complete opposite path.
The very same thing would occur at the 2nd boundary. A flat
slab of material would thus send all of the gentle rays initiating
from one point to a mirror image issue on the reverse side of
the slab. It will serve as a lens without demanding the
specifically curved surfaces that regular lenses require.
Furthermore, it wouldn't confront the issues which compel the
accuracy of curved lenses therefore may make a great lens.
Fig 5: Negative refraction explained- How a perfect lens would bend
light
Unfortunately, the only material with a negative refractive
index to be developed so far functioned only at wavelengths

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RRIJM 2015, All Rights Reserved 667 | Page
very much longer than the wavelength of visible light. A team of
investigators led by Alexander Grigorenko of the University of
Manchester took a step closer towards producing a material
with a negative refractive index which works for visible light
rays. Their goal was to produce the elusive magnetic response
required to turn the refractive index negative.
The scientists covered a small glass plate with little gold
pillars, each about 100 Nano meters high. They found that
these structures performed like bar magnets when light shone
on them, abandoning the magnetic component of the incident
light ray. In other words, the material had negative
permeability, one of the two factors of a negative refractive
index.
Further work is required to produce a material that
negatively refracts visible light. But the result is animportant
step towards generating a perfect lens that could focus
imageries to show features smaller than the wavelength of light
itself.
Metamaterials to improve the efficiency of wireless
transmission:
In modern era, wireless power transmission is one of the
transmissions, which is undergoing with lots of investigation
and have many applications, including wireless charging of
electronic devices, electrical vehicles and powering on of fixed
bio medical devices. Wireless power transmission uses
magnetically attached resonant circuit to transfer the power
without use of any wiring medium. However, efficiency of
transmission decreases sharply due to the divergence of
magnetic field, specifically under coupled areas.
Electromagnetic metamaterial can influence the direction of
electromagnetic fields due to its abnormal permittivity or
permeability [8].
We live in a world of technological development. New
technologies arearising every day to make our lives more
comfortable. Despite all these, we still depend on on the
conventional wire system to charge our low power machineries
such as cell phones, digital camera and digital watches etc.
and even the devices with mid power such as laptops. When it
comes to charge several devices simultaneously the
conventional wire system produces a chaos and It also require
a lot of electric sockets and each device has different design
for the charging port. At this point a question might arise.
―What if only one charger can be used to charge many
devicesat the same time without the use of wiring system and
without producing a chaos in the process? We gave it a
thought and came up with an idea. The answer to all these
dilemma lies with inductive coupling, a simple and more
efficient way of transferring power without use of wires[9][10].
Wireless Power Transmission is the effective transmission of
electric power from one point to another through vacuum or an
atmosphere.The power can be transmitted effectively with the
use of Inductive coupling for short range devices, resonant
Induction for mid-range devices and electromagnetic wave
power transfer for high range devices. Wireless transmission of
the power can be possible by using metamaterials.
Metamaterialscan improve the effectiveness by its property
through space and charge a chosen low power device. The
system using resonant coils can be used to transmit power
from an AC line to a resistive load. Investigation of numerous
geometrical and physical form factors calculated in order to
increase coupling between transmitter and receiver using
metamaterials. An achievement in doing this would remove the
usage of cables in the charging process hence making it much
easier to charge a low energy device. It'd also verify the
security of the unit since it'd eradicate the risk of short circuit.
Use of metamaterials will in addition earn simple to impose
multiple minimal energy devices instantly using a source which
could utilize one power outlet [10][11][12].Metamaterials are
produced from musters of several elements created from
compound components like plastics or metals. The supplies
are generally organized in repeating patterns. The patterns are
set up at scales which are smaller compared to the
wavelengths on the phenomena that they influence.
Metamaterials develop the properties of theirs from their newly
created configurations not from the attributes of the starting
materials. The accurate figure, geometry, dimension,
arrangement and alignment of the metamaterials provides
intelligent qualities, that create them proficient in manipulating
electromagnetic waves by blocking, absorbing, enhancing, or
perhaps bending waves, to achieve advantages that go beyond
what's achievable with standard materials. Properly designed
metamaterials are able to affect electromagnetic radiation or
maybe sound waves in a fashion that isn't observed in
standard materials. The supplies which display a bad refractive
index for certain wavelengths have fascinated many significant
researches. These substances are called negative refractive
index metamaterials.
Dr. Shiva Kumar and his staff created metamaterials in 2
shapes with Computer Simulation Technology Suite (CST
MWS) software program and after that compared their
simulation results [thirteen]. Fig six shows the shapes of square
shaped split ring resonator, circular shaped split ring resonator
and 2X2 slabs of circular and square split ring resonators
respectively that had been created by Dr. Shiva Kumar and the
staff of his in 2018 to improve the electrical power
transmission. They developed a metamaterial with Square
shape and also circular shape short range systems. In their
designs metamaterial unit cell was miniaturized deep into the
sub-wavelength selection and also a compressed content that
comprise of those device cell was fabricated. Experimentations
with a reasonable 2 coil power transfer system offered that
proficiency increases were achievable no matter if the total
separation between the coils were better and also the
metamaterial was positioned near the getting and transmitting
coil. This could provide considerable latitude within the style of
small range wireless power transmission devices and also
makes it possible for greatest remedies being discovered within
the restraints of exact applications [14].

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RRIJM 2015, All Rights Reserved 668 | Page
Fig6: Different shapes of metamaterials to increase the efficiency of power transmission system
Dr. Shiva and his staff demonstrated that the Square
shaped split ring resonator had far more efficiency than
Circular shaped split ring resonator. They found that use of a
metamaterial slab might relieve the consequences of coil
offsets on system efficacy. Consequently, use of a small
metamaterial slab could be a feasible strategy to boost the
expertise associated with a wireless power transfer program
and also might be useful in applications like wireless charging
and powering implantable biomedical devices.
4. Other Applications:
Applications of Metamaterials are discovered in different
fields which includepublic safety, sensor detection, higher
frequency battle field communication, enhancing ultrasonic
sensors, solar energy management, for increased gain
antennas and remote aerospace applications [fifteen].
4.1 WMD Detectors: Army and air Force scientists use
metamaterials to sense the presence of chemical explosives,
biological agents, and pollution.
4.2 Invisible Subs: The metamaterials could affect the
wavelength of sound. It bends sound waves across the
submarine making it invisible to enemy sonar. Civilian spinoffs
also make use of the metamaterials to create sound proof
rooms with great acoustics.
4.3 Biosensor Biosensors: These're really important
resources in a number of places, like green monitoring, food
security and illness diagnostics within the study of natural
phenomena recently metamaterials are employed by
researchers in bio sensing technologies due to its detection of
label free bio molecules and effective cost.
4.4 Metamaterials Absorber: A metamaterial absorber
competently absorbs electromagnetic radiation. Metamaterials
absorbers have numerous benefits over traditional absorbers
such as for instance supplementary miniaturization, broader
adaptableness, and improved effectiveness. To make a high
ratio of electromagnetic radiation absorption, it requires highly
effective medium design, magnetic permeability and
permittivity.
4.5 Metamaterial Antennas: Negative refractive index
metamaterials are utilized in antennas to increase the
functionality of shrunk antenna systems. The metamaterials
antennas are utilized to boost the output of an antenna due to
its distinctive band gap characteristics & periodic structures. In
little standard antennas the maximum of the wavelength echos
the signal to the source whereas the metamaterials antenna
has arrangement which re radiates and shops power making
the size of its tiny and behaves as bigger antenna. Fig.7
exhibits the Z shaped Metamaterials Antenna.
Fig 7: Z- shaped antenna

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The application of metamaterials, properly created to
increase some prescribed antenna characteristics as
impedance matching, competence, increased bandwidth, etc.
Several of metamaterials antennas are below:
4.5.1Zero-Phase-Shift Line Based Antenna: A
circumference of 2 working wavelengths at ultra high frequency
bands for the near field RFID applications runs on the zero-
phase-shift segmented loop antennas since it create a bit
larger even magnetic field. A circularly polarized Omni
directional antenna design with zero-phase-shift type is utilized
for all the apps of wireless neighborhood area network.
4.5.2 Anisotropic High Permittivity Loaded Antenna:
To designa multiple input multiple output systema dipole
antenna is used and is laden with good permittivity anisotropic
metamaterials. In order to reduce the thickness as much as a
great level in arrays of cellular base station idea of this style is
used.
4.5.3 Mushroom Antenna: The antenna that fashioned
with group of many mushroom cells is known as a mushroom
type antenna. This kind of antenna is utilized for all the apps of
Wi Fi.
4.5.4 Gap Capacitor Loaded Antenna: This antenna is
set of a selection of slotted patches with anti phase and also
zero order resonance that presents a series gap capacitance at
center of the spot and at its radiating edges. This kind of
antennas is applucable in L band radar system.
5. Future Scope with Metamaterial:
Metamaterials are artificially created materials getting bad
index of refraction and as a result of this the daydream of
invisibility cloaks is starting to be possible so the 2 measures
have actually been consumed that specific path. Duke Faculty
has already been doing work on changing technology with
metamaterials for hiding obstructive structures or even
designing invisibility cloaks before year 2020. Metamaterial
camera might be created without a lens or even moving parts
that uses compressed microwave images. As metamaterials
have far better absorption featurestherefore Units with
metamaterials may be made that brings down the size of
standard units and can raises the absorption of solar power.
This technological innovation utilizing metamaterials might
work as energy efficient satellite communication devices for
troops on the battleground.
6. Conclusion:
Metamaterials will be the new area of investigation, without
any qualmwe is able to say that metamaterials is now an
incredibly enjoyable investigation area. The area of
metamaterials is a turf of investigation with talent. From
microwave and optical sciences, acoustics, materials science,
nanotechnology and also high performance computing each
are intrigued by the meatmaterials. Since the start of the
century, lots of research papers are written on the subject of
Metamaterials. The scientists from many disciplines are now
being fascinated towards metamaterials due to its distinctive
electromagnetic characteristics. Therefore there's an excellent
area of development and study for the producing brand new
solutions for future development. In this paper, a brief overview
of the metamaterials its many kinds and uses of metamaterials
are talked about. The metamaterials have generated incredible
advancements in electromagnetic response capabilities which
can provide exciting chances of potential look of equipment
plus components applying quiet features of metamaterials.
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