Tunable Metamaterial and its application

1. Pre-Registration Seminar
On
Presented By
Neha Niharika
Roll No:185EC16
Department of Electronics and Communication Engineering
National Institute of Technology
Patna 800005
Under the Supervision of
Dr. Sangeeta Singh
Tunable Terahertz Devices

2. 2
Outline
 Introduction
 Metamaterial based absorber
 Literature review
 Problem identification
 Approaches to be followed
 Implementation of paper
 Future work
 References

3. Introduction to Metamaterials
A periodic material that derives its properties from its structure rather than its components.
Fig 1a Fig 1b

4. • “Meta-” means “altered, changed” or “higher, beyond”
• Existing materials only exhibit a small subset of electromagnetic properties
theoretically available
• Metamaterials can have their electromagnetic properties altered to something
beyond what can be found in nature.
• Can achieve negative index of refraction, zero index of refraction, magnetism at
optical frequencies, etc.
• “Metamaterial” coined in the late 1990’s
Introduction to Metamaterials

5. Historical overview of Metamaterial
• 1948: E.Kock tailored εeff and µeff by periodically arranging the
conducting disks, strips and spheres
• 1968: Veselgo predicted the existance of LHM
• 1996:realization of negative permittivity practically by Pendry
• 2001:First experimental demonstration of LHM by Smith
Introduction Contd …
• 1999: realization of negative permeability practically by Pendry

6. Application of Metamaterials
Fig 2a. super lens imaging [6] Fig 2b. cloaking [7]
Fig 2c. tunable MTMs [8]
1) N.Fang, H.Lee, C.Sun, and X.Zhang, “Sub–Diffraction-Limited Optical Imaging with a Silver
Superlens”, Science, Vol. 308, no. 5721, pp. 534-537,April 2005.
2) S.A.Cummer, B.I.PopaD.Schurig, D.R.Smith, and J.B.Pendry, “Full-wave simulations of
electromagnetic cloaking structures”, Phys. Rev. Lett. (E), Vol. 74, pp. 036621,May 2006.
3) M.Lapline, “Tunable metamaterials: the key step to practical application”, (Online web page, SPIE
Newsroom, 2009.

7. • Terahertz radiation, also called submillimeter radiation, terahertz waves,
terahertz light, T-rays, T-waves, T-light, T-lux, or THz
• consists of electromagnetic waves at frequencies from 0.3 to 10 terahertz
(THz).
• The term applies to electromagnetic radiation with frequencies between the
high-frequency edge of the millimeter wave band, 300 GHz and the low
frequency edge of the far-infrared light band, 3000 GHz.
• Some of the application Terahertz devices:
Absorber
Polarizer
Transmitter
Sensor etc
Terahertz Devices

8. Metamaterial Based Absorber
• Artificial effective homogeneous structures with unusual electromagnetic properties
characterized by the effective permittivity (εeff) and permeability (µeff) which measure the
effects of electric and magnetic field on and by the medium by suitably adjusting its structural
parameters..
• The structure of the MA is basically composed of unit cells arranged in a periodic manner.
The structure consists of a top conducting layer and a bottom ground plane isolated by a
dielectric interlayer.
Fig (3)
Fig4. metamaterial perfect absorber made of electric/magnetic metasurface on top of a metallic ground
plate. Reproduced from the reference [9]
.
Introduction Contd …

9. Absorption in Metamaterial
When an electromagnetic wave is incident upon a metamaterial structure, the electric field is
coupled with the top metallic structure and controls the electric permittivity (εr). The counter
propagating circulating currents at the top and the bottom ground layers couples with the
magnetic field and controls the magnetic permeability (µr) of the structure. Therefore, by
optimizing the physical parameters of the top metal layer and the thickness of the dielectric
substrate, the electric and magnetic fields can be effectively coupled in a specific frequency
range where the input impedance Z (ω) can be matched with free space impedance (Z0) at the
interface resulting minimization of S11 of the structure
Reproduced from reference [10]
Introduction Contd …
𝐴 𝑤 = 1 − |𝑆11|2 − |𝑆21|2
= 1 − |𝑆11|2
𝑆11 =
𝑍 𝑤 − ηo
𝑍 𝑤 + ηo
|𝑆21|2 =0
Z(w)=ηo
(1 + 𝑆11)2 − S2
21
(1 − 𝑆11)2 − S2
21

10. Development in Metamaterial based application
Fig 4 Current trends in metasurface absorber. Reproduced from reference [11]
Introduction Contd …

11. STATE OF ART:
Various studies have been done for enhancement of bandwidth absorption of metamaterial
and one of the approach is frequency tunable metamaterial and this can be done by using the
material whose property can be tuned according to the requirement rather than making
changes in geometry of absorber.
Some of the approaches are:
• Tuning via thermo-optic effect.
• Tuning via free carrier effects
• Tuning via Phase Transition material
• Chalcogenide glass.
• Graphene.

12. Tuning via Phase Transition material
TOPIC AUTHORS YEAR OF
PUBLICATION
OBSERVATION
A tunable hybrid
metamaterial absorber
based on vanadium
oxide films
Qi-Ye Wen, Huai-Wu
Zhang, Qing-Hui
Yang, Zhi Chen, Yang
Long, Yu-Lan Jing,
Yuan Lin and Pei-Xin
Zhang
Journal of Physics :D
Applied Physics
(2012)
Amplitude and
frequency of the
device has been tuned
by make phase
transition of V02.
Switchable and
tunable metamaterial
absorber in THz
frequencies
Dang Hong Luu,
Nguyen Van Dung,
Pham Hai, Trinh Thi
Giang, Vu Dinh Lam
Journal of Science:
Advanced Materials
and Devices (2016)
The absorption
intensity and
absorption frequency
has been tuned with
modification of the
conductivity of V02
while the absorption
frequency is tuned by
changing the
temperature of InSb
material filled into
two slits of SRR.
• Vanadium Oxide (Vo2)

13. TOPIC AUTHORS YEAR OF
PUBLICATION
OBSERVATION
Development of a
tunable terahertz
absorber based on
temperature control
Liu Jianjun ,Fan
Lanlan
Microwave and
Optical Technolgy
Letters (2019)
Phase transition of
thermally triggered
VO2 thin films is used
to control the
absorption rate of
metamaterial absorber
Study on Temperature
Adjustable Terahertz
Metamaterial
Absorber Based on
Vanadium Dioxide
Yubing Zhang ,
Pinghui Wu , Zigang
Zhou , Xifang Chen ,
Zao Yi , Jiayi Zhu ,
Tiansheng Zhang ,
and Huge Jile
2020 three tunable terahertz
metamaterial
absorbers based on
VO2 were designed,
providing flexible
control over the
absorption
performance

14. TOPIC AUTHORS YEAR OF
PUBLICATION
OBSERVATION
Tunable broadband
terahertz
metamaterial
absorber using
multi-layer black
phosphorus and
vanadium dioxide
Tongling Wang ,
Lizhi Qu , Lingfei
Qu , Yuping Zhang
, Huiyun Zhang and
Maoyong Cao
Journal of Physics
D: Applied Physics
(2020)
The proposed device
uses two independently
controllable methods to
achieve absorption
tuning from 34.64 to
98.8% and from 8 to
98.8% by adjusting the
electron doping of BP
and conductivity of Vo2
Dual-controlled
switchable
broadband
terahertz absorber
based on a
graphene-
vanadium dioxide
metamaterial
Tongling Wang,
Yuping Zhang,
Huiyun Zhang, and
Maoyong Cao
Optical Material
Express (2020)
A dual-controlled
switchable broadband
terahertz (THz)
metamaterial absorber
which shows tuning of
absorptance from 26 to
99.2% by varying the
graphene Fermi energy
and from 9 to 99.2% by
increasing the
conductivity of the VO2.

15. Switchable and tunable metamaterial absorber in THz frequencies
Luu, Dang Hong; Van Dung, Nguyen; Hai, Pham; Giang, Trinh Thi; Lam, Vu Dinh “Switchable and tunable
metamaterial absorber in THz frequencies”, Journal of Science: Advanced Materials and Devices, 1(1), 65–68
(2016)
Fig 5a. schematic diagram of MMA structure Fig 5b. absorption spectra of MM structure with different
conductivity values of VO2 film.
Fig 5c. schematic diagram of MMA structure with InSb filled
Fig 5d. the simulated absorption spectra
of MMA structure with different
temperature

16. Dual-controlled switchable broadband terahertz absorber based on a graphene-vanadium
dioxide metamaterial
Wang, Tongling; Zhang, Yuping; Zhang, Huiyun; Cao, Maoyong “Dual-controlled switchable broadband terahertz
absorber based on a graphene-vanadium dioxide metamaterial” Optical Materials Express, 10(2), 369 (2020)
• To achieve dynamically dual-controlled switchable broadband Thz absorptance,
metamaterials with both graphene and Vo2 has combined.
Fig 6a. schematic of graphene and Vo2 -based metamaterial broadband absorber
Fig 6b. absorptance spectra of the proposed absorber
at various VO2 conductivities
Fig 6c. absorptance spectra of the proposed absorber at various
fermi energy of Graphene

17. • Liquid Crystal
LC is probably the most widely used active material in optics. Its large optical birefringence,
which can be controlled by thermal or electrical stimuli, makes it an obvious potential option
as a tuning medium for metasurfaces
TOPIC AUTHORS YEAR OF
PUBLICATIO
N
OBSERVATION
Liquid Crystal
Tunable
Metamaterial
Absorber
David Shrekenhamer,
Wen-Chen Chen, and
Willie J. Padilla
Physical Review
Letter (2013)
Incorporation of active liquid
crystal into strategic locations
within the metamaterial unit
cell, absorption has been
tuned.
Terahertz
characterization of
tunable
metamaterial based
on electrically
controlled nematic
liquid crystal
Rafał Kowerdziej,
Marek Olifierczuk,
Janusz Parka, and
Jerzy Wróbel
Applied Physics
(2014)
The proposed tuning system is
based on the use of the NLC.
Its properties can be
controlled by reorienting the
LC molecular direction with
the application of bias voltage.

18. TOPIC AUTHORS YEAR OF
PUBLICATION
OBSERVATION
A Tunable
Metamaterial
Absorber Based on
Liquid Crystal
Intended for F
Frequency Band
Guangsheng Deng,
Tianyu Xia,
Shuaicheng Jing,
Jun Yang, Hongbo
Lu, and Zhiping Yin
IEEE Antenna and
Propagation Letter
(2017)
The orientation of the
liquid crystal
molecules can be
macroscopically
controlled by voltage
between top metal
pattern layer and metal
ground. Thus, the
permittivity of the LC
layer, dynamically
changed which helps
in tuning of absorption
frequency.
Electrically tunable
terahertz dual-band
metamaterial
absorber based on a
liquid crystal
Zhiping Yin, Yujiao
Lu, Tianyu Xia,
Weien Lai, Jun
Yang, Hongbo Lu
and Guangsheng
Deng
Royal Society of
Chemistry (2018)
A liquid crystal (LC)
based tunable
metamaterial absorber
with dual-band
absorption is presented
which shows
frequencies can be
dynamically tuned by
adjusting the bias
voltage of the LC layer

19. TOPIC AUTHORS YEAR OF
PUBLICATION
OBSERVATION
Fast-Tunable
Terahertz
Metamaterial
Absorber Based on
Polymer Network
Liquid Crystal
Jhiping Yin , Chaofan
Wan , Guangsheng
Deng, Andong
Zheng, Peng Wang,
Yang Yang, Sheng
Gao, Jun Yang,
Fei Cai , Zelun Li and
Hongbo Lu
Applied Science
(2018)
A tunable metamaterial
absorber (MA) based on
polymer network liquid
crystal (PNLC) in the
terahertz (THz)
frequency band. Under
the optimal
polymerization
condition, through
electrical control of the
orientation of the PNLC
embedded in the
frequency selective
surface, the resonant
frequency of the
absorber can be tuned

20. Electrically tunable terahertz dual-band metamaterial absorber based on a liquid crystal
Zhiping Yin, Yujiao Lu, Tianyu Xia, Weien Lai, Jun Yang, Hongbo Lu and Guangsheng Deng “ Electrically
tunable terahertz dual-band metamaterial absorber based on a liquid crystal” Royal Society of Chemistry
4197-4023 (2018)
Fig 7a. schematic of a unit cell of the proposed tunable dual-
band metamaterial absorber based on the liquid crystal.
Fig 7b. absorption spectrum of the
proposed metamaterial absorber

21. A Tunable Metamaterial Absorber Based on Liquid Crystal Intended for F Frequency Band
Guangsheng Deng, Tianyu Xia, Shuaicheng Jing, Jun Yang, Hongbo Lu, and Zhiping Yin “A Tunable
Metamaterial Absorber Based on Liquid Crystal Intended for F Frequency Band” IEEE Antenna and
Wireless Propagation Letter (16) (2017)
(c)
Fig 8c. measured absorptivity for different bias voltage
Fig 8b. simulated spectra of absorptivity with
no bias and fully bias voltage
Fig 8a. schematic of LC based absorber

22. • Chalcogenide Glasses
Among various kinds of nonvolatile PCMs, ChGs such as germanium–antimony–tellurium (GST)
are the most common choice in photonic applications for their quick responses to external stimuli
and reliable data retentions
TOPIC AUTHORS YEAR OF
PUBLICATION
OBSERVATION
A Switchable
Mid‐Infrared
Plasmonic
Perfect
Absorber with
Multispectral
Thermal
Imaging
Capability
Andreas Tittl, Ann
Katrinn U, Michel
Martin, Xinghui Yin,
Behrad Golipur and
Harald Geissien
Advanced Material
(2015)
Utilizing the
amorphous‐to‐crystalline
phase transition in GST,
the proposed structure
offers switchable
absorption with strong
reflectance contrast at
resonance and large
phase‐change‐induced
spectral shifts

23. TOPIC AUTHORS YEAR OF
PUBLICATI
ON
OBSERVATION
Dynamic Thermal
Emission Control
Based on Ultrathin
Plasmonic
Metamaterials
Including Phase-
Changing Material
GST
Yurui Qu, Qiang
Li, Kaikai Du, Lu
Cai, Jun Lu, and
Min Qiu
Laser &
Photonics
(2017)
An ultrathin plasmonic
thermal emitter is
experimentally demonstrated
to dynamically control
thermal emission with low-
power-consumption. The
dynamic low-power-
consumption control is
implemented by
incorporating phase-
changing material
Ge2Sb2Te5 (GST),
Tunable near-
infrared perfect
absorber based on
the hybridization of
phase-change
material and
nanocross-shaped
resonators
Ce Li, Wei Zhu,
Zhe Liu, Shi Yan,
Ruhao Pan, Shuo
Du, Junjie Li, and
Changzhi Gu
Applied Physics
Letter (2018)
A tunable GST-based MPA in
the near infrared region was
demonstrated. Dielectric
environment engineering,
which is equivalent to tuning
the permittivity of the
capacitance of the LC circuit
result in the change of
resonance.

24. TOPIC AUTHORS YEAR OF
PUBLICATION
OBSERVATION
Near-field
imaging of the
multi-resonant
mode induced
broadband
tunable
metamaterial
absorber
Lulu
Chen, Liaoxin
Sun, Hongxing
Dong, Nanli
Mou, Yaqiang
Zhan, Qisong
Li, Xiongwei
Jiang and Long
Zhang
Royal Society of
Chemistry (2019)
The proposed absorber shows
the dynamic tunability due to the
phase change of ultrathin GST
layer. The absorptive
wavelength will shift to longer
wavelength after converting the
GST thin film from amorphous
to crystalline phase
Tunable perfect
absorber based
on gold grating
including phase-c
hanging material
in visible range
Lei Zhang,
Ying Wang,
Le Zhou,
Fang Chen
Applied Physics
(2019)
A tunable GST-based gold
grating structure which show the
absorption can be dynamic
controlled by inserting phase-
changing material.

25. TOPIC AUTHORS YEAR OF
PUBLICATION
OBSERVATION
Large-scale, low-
cost, broadband
and tunable
perfect optical
absorber based on
phase change
material
Nanli Moua,b,
Xiaolong Liuc
Tao Weia ,
Hongxing
Donga , Qiong
Hed,e, Lei
Zhoud,e,
Yaqiang
Zhanga,Long
Zhanga and
Shulin Sunc
Royal Society of
Chemistry (2020)
broadband,
polarization-
insensitive and tunable
optical metamaterial
absorber which utilise
the optical properties
of the PCMs tune the
working band of the
proposed metamaterial
absorber via varying
temperature,

26. Tunable near-infrared perfect absorber based on the hybridization of phase-change material
and nanocross-shaped resonators
Fig 9a schematic of nanocross-shaped MPA and the incident light polarization configuration. 9b and 9c top view
and side view of the MPA unit cell (c) experimental and simulated performance , the black line and the red line
are the reflection and absorption spectra, respectively
Fig 9a
Fig 9b
Fig 9c
Ce Li, Wei Zhu, Zhe Liu, Shi Yan, Ruhao Pan, Shuo Du,Junjie Li, and Changzhi Gu “Tunable near-infrared
perfect absorber based on the hybridization of phase-change material and nanocross-shaped resonator”
Applied Phys. Lett. 113, 231103 (2018)

27. • Strontium Titanate
TOPIC AUTHORS YEAR OF
PUBLICATION
OBSERVATION
Thermal tunability
in terahertz
metamaterials
fabricated on
strontium titanate
single-crystal
substrates
Ranjan Singh
Abul K. Azad
Q. X. Jia
Antoinette J.
Tayloran Hou-
Tong Chen
Optics Letters
(2011)
A planar gold SRR array
fabricated on single-crystal bulk
STO shows the resonant
behavior in Thz freq range with
the variation in temperature
Frequency tunable
metamaterial
absorber at deep-
subwavelength scale
Ben-Xin Wang,
Xiang Zhai,Gui-
Zhen Wang,
Wei-Qing Huang
and Ling-Ling
Wang
Optic Express (2014) A frequency tunable and deep-
subwavelength scale terahertz
metamaterial absorber formed by
a square metallic patch and a
strontium titanate dielectric layer
on top of a ground plane which
shows The shift of the resonance
frequency is attributed to the
temperature-dependent refractive
index of the dielectric layer

28. TOPIC AUTHORS YEAR OF
PUBLICATION
OBSERVATION
Tunable silicon-based
all-dielectric
metamaterials with
strontium titanate thin
film in terahertz range
Yanjiao Zhao,
Baiwei Li,
Chuwen Lan, Ke
bi, and Zhaowei
Qu
Optic Express
(2017)
A tunable silicon all-dielectric
metamaterials in THz ranges by
covering the SAMs with a layer
of STO showing the resonance
frequencies is tuned on the basis
of temperature dependent
complex relative permittivity.
Bi-tunable terahertz
absorber based on
strontium titanate and
Dirac semimetal
C. Kadalec,
V.Sokoromets,
F.Kadlec,
H.Nemec,
H.Chen,
V.Jurka,
K. Hruška and
P.Kužel
Journal of Physics
D: Applied Physics
Year (2018)
A frequency-tunable
metamaterial in the THz range,
consisting of metallic
subwavelength resonators
patterned on an active thin layer
of strained SrTiO3 which shows
a resonance near 0.5 THz, which
is determined both by the
geometric shape of the resonators
and by the permittivity of the
active layer
.

29. TOPIC AUTHORS YEAR OF
PUBLICATIO
N
OBSERVATION
Metamaterial
absorber with
independently
tunable amplitude
and frequency in the
terahertz regime
Xin Huang, Fan
Yang, Bing Gao,
Qi Yang, Jiamin
Wu, and Wei He
Optics Express
(2019)
Effective combination of graphene
and strontium titanate (STO) in one
metamaterial structure, the tunable
properties of the amplitude and
center frequency are implemented.
The amplitude can be tuned by
adjusting the chemical potential of
graphene sheet, and center
frequency can get a shift through
temperature changes in the STO
material
Bi-tunable terahertz
absorber based on
strontium titanate
and Dirac semimetal
Han xiong,
Yuehong Peng, Fan
Yang
Zhijing Yang, and
Zhenni Wang
Optics Express
(2020)
A polarization-insensitive absorber
based on strontium titanate (STO)
and bulk Dirac semimetal (BDS) in
the terahertz (THz) region. The
center frequency of the absorption
peak can be independently
regulated by temperature or Fermi
energy level of STO or BDS,
respectively

30. Thermally tunable metamaterial absorber based on strontium titanate in the terahertz regime
Xin Huang, Wei He, Fan Yang, Jia Ran, Qi Yang and Shengyi Xie “Thermally tunable metamaterial absorber based
on strontium titanate in the terahertz regime” optical materials express 1377, vol 9 (2019)
Fig 10a. schematic of the absorber
(c)
Fig 10c. absorption spectra of absorber with different temperature
Fig 10b. absorption spectra under normal incidence at temp 400k

31. Metamaterial absorber with independently tunable amplitude and frequency in the terahertz
regime
Xin huang, Fan yang, Bing gao, Qi yang, Jiamin Wu, and Wei He “Metamaterial absorber with independently
tunable amplitude and frequency in the terahertz regime” Optics Express Vol.19 (2019)
Fig 11b. central frequency tunable spectra
by changing temperature
Fig 11a. schematic representation (top view) of unit cell
Fig 11c. amplitude tunable spectra under different chemical potential

32. Tuning via Free-Carrier Effects
According to the Drude model, plasma frequencies, and thus refractive indices of semiconductors
can be tuned by altering their carrier densities and effective masses.
TOPIC AUTHORS YEAR OF
PUBLICATI
ON
OBSERVATION
Thermal
broadband
tunable Terahertz
metamaterials
Jun Zhu, Jiaguang
Han ,Zhen Tian ,
Jianqiang Gu ,
Zhongyong Chen,
Weili Zhang
Optics
Communication
(2011)
Incorporation of the semiconductor
into the gap of metallic SRRs, where
precise patterning of semiconductors
permits frequency tuning of the
metamaterial resonance by changing
the external temperature
Temperature
tunable
metamaterial
absorber at THz
frequencies
Ben-Xin Wang, ·
Gui-Zhen Wang
Journal Material
Science (2017)
A wide frequency tunable range of
terahertz absorber formed by a metallic
patch resonator and a metallic board
spaced by an InSb dielectric layer is
demonstrated. The frequency of the
absorber can be tuned actively by
varying the temperature of the
absorber, and finally a 80.4%
frequency tuning rang is obtained.

33. TOPIC AUTHORS YEAR OF
PUBLICATION
OBSERVATION
InSb-Enhanced
Thermally
Tunable
Terahertz
Silicon
Metasurfaces
Daquan Yang ,
Chao Zhang ,
Xiaogang Li , and
Chuwen Lan
IEEE Access (2019) Thermally tunable THz all-
dielectric grating structure consists
of two dielectric layers in which
the posterior is silicon grating and
the former is InSb thin film. The
thermal tunability of the grating
structure is also dependent on the
temperature and thickness of the
InSb thin film, which we can
speculate from the enhanced
frequency shift in the absorber
structure
Design of a six-
band terahertz
metamaterial
absorber for
temperature
sensing
application
Haijun Zou, Yongzhi
Cheng
Optics Material
(2019)
A six-band terahertz MMA, which
consists of a metallic cross-cave-
patch (CCP) structure array and an
InSb dielectric substrate layer
backed by a ground-plane which
shows tuning of resonance
frequency is achieved using
temperature dependent refractive
material Insb

34. TOPIC AUTHORS YEAR OF
PUBLICATION
OBSERVATION
Thermally tunable
terahertz metasurface
absorber based on all
dielectric indium
antimonide resonator
structure
Hao Luo,
Yongzhi cheng
Optical materials
(2020)
A novel design of temperature
tunable metasurface absorber
(MSA) based on all dielectric
indium antimonide (InSb)
resonator structure in terahertz
(THz) regionhe is proposed in
which dielectric property of the
InSb can be actively adjusted
through the external environment
heat with different temperature.
Temperature Tunable
Seven Band Terahertz
Metamaterial Absorber
Using Slotted Flower–
Shaped Resonator on
an InSb Substrate
Bhargav
Appasani
Plasmonics (2021) A seven-band temperature tunable
terahertz metamaterial absorber is
proposed, whose unit cell consists
of a slotted flower–shaped
resonator (S-FSR) on InSb
dielectric substrate which shows
temperature tenability is because
of the changes in the plasma
frequency of the dielectric.

35. Thermal broadband tunable Terahertz metamaterials
Jun Zhu, Jiaguang Han, Zhen Tian, Jianqiang Gu, Zhongyong Chen , Weili Zhang “Thermal broadband tunable
Terahertz metamaterials” Optics Communications 284 3129–3133 (2011)
(c)
Fig 12a. unit cell of proposed absorber
Fig 12b. Simulated transmission with quartz substrate Fig 12c. Simulated transmission with sillicon substrate

36. • Graphene
Graphene, a two-dimension material consisting of one monolayer of carbon atoms, has been
recently applied in electronic and photonic devices due to its exotic properties, such as optical
transparency, flexibility, high electron mobility.In addition, its sheet conductivity can be
continuously tuned in a broad frequency range by shifting the electronic Fermi level via
chemical or electronic doping, which enables fast electrical modulation and on-chip
integration.This makes the continuous or structured graphene sheet a promising candidate for
designing tunable THz metamaterial.
TOPIC AUTHORS YEAR OF
PUBLICATION
OBSERVATION
Tunable THz perfect
absorber using
graphene-based
metamaterials
Mahboobeh Faraji,
Mohammad
Kazen, Moravvej
Farshi and Leila
Yousefi
Optics
Communication
(2015)
Tunable and switchable
absorber using two patterned
graphene layers (i.e., fishnet
plus microribbons) both in
one unit cell shows perfect
absorbances of 96–99%
obtained at various
frequencies centered about
2.14–9.94 TH

37. TOPIC AUTHORS YEAR OF
PUBLICATION
OBSERVATION
A Tunable
Ultrabroadband
Ultrathin Terahertz
Absorber Using
Graphene Stacks
Yanfei Dong,
Peiguo Liu,
Dingwang Yu,
Gaosheng Li
and Liang
Yang
IEEE Antenna and
Wireless
Propagation Letter
(2016)
dynamic tuning of the
absorption band, is achieved by
combining two concentric
circular split-rings encircling a
split circular resonator with
graphene stacks embedded in a
SiO 2 dielectric. the frequency
response can be dynamically
tuned by varying the graphene
gate voltage to reduce the need
for complex bias network
Based on graphene
tunable dual-band
terahertz metamaterial
absorber with wide-
angle
Mulin Huang,
Yongzhi
Cheng,
Zhengze
Cheng,
Haoran Chen,
Xuesong Mao
and Rongzhou
Gong
Optics
Communication
(2018)
A tunable MMA based on the
SGP for THz waves, which
yields dual-band and wide-angle
absorption properties has been
demonstrated
.

38. TOPIC AUTHORS YEAR OF
PUBLICATION
OBSERVATION
Ultra-thin and
broadband tunable
metamaterial
graphene absorber
Han Xiong, Ying-
Bo Wu, Ji Dong,
Ming-Chun Tang,
Yan-Nan Jiang, and
Xiao-Ping Zeng
Optics Express
(2018)
an ultra-thin and broadband
metamaterial absorber which
is frequency tuned by
graphene in the far-infrared
region is designed. By
varying an external bias
voltage applied to the
graphene and geometric size
of each patch, absorption
band and spectral position of
the proposed absorber can be
controlled
The design of a
graphene-based
wideband tunable
metamaterial absorber
in THz regime.
L Wang, C Ding,
D Xia, X Ding
and Y Wang
IOP Conference
series: Material
series &
Engineering
(2019)
A wideband tunable MMA
based on graphene in
Terahertz regime using a
single layer of multiple split-
ring resonators (SRRs) has
been demonstrated

39. TOPIC AUTHORS YEAR OF
PUBLICATION
OBSERVATION
Graphene-based dual-
band tunable perfect
absorber in THz range
Zhaoyang Liu,
Jian Li, Lingjuan
He and Tianbo
Yu
2021 Absorber is composed of a
circular graphene layer with
an ellipse cut out in the centre,
separated by a dielectric layer
in the middle and a gold
mirror at the bottom. position
of the absorption peak can be
changed by adjusting the
Fermi level and geometric
parameters of the graphene
pattern. Furthermore, the
absorber is insensitive to the
polarized incident light with a
wide incident angle.
Tunable terahertz
perfect absorber with
a graphene-based
double split-ring
structure
Zhendong Wu,
Bijun Xu,
Mengyao Yan,
Bairui Wu, Pan
cheng and
Zhichao Sun
Optical Material
Express (2021)
The impact of different Fermi
energies and the disparate
relaxation times on the
regulation of absorption along
with the optimal structure
parameters has been explored
required to achieve perfect
absorption.

40. Based on graphene tunable dual-band terahertz metamaterial absorber with wide-angle
M.Huang, Y.Cheng, H.Chen, X. Mao, R. Gong “Based on graphene tunable dual-band terahertz metamaterial
absorber with wide-angle” ,Optics Communications, Vol 415, 194-201 (2018)
Fig 13a. schematic of MMA Fig 13b. unit cell of absorber
Fig 13c. absorbance of the MMA with (a) non-SGP and SGP; (b) lossfree and loss dielectric

41. Ultra-thin and broadband tunable metamaterial graphene absorber
Xiong, Han; Wu, Ying-Bo; Dong, Ji; Tang, Ming-Chun; Jiang, Yan-Nan; Zeng, Xiao-Ping
(2018). Ultra-thin and broadband tunable metamaterial graphene absorber. Optics Express, 26(2)
Fig 14b. Reflection spectra with different Fermi level
Fig 14a. schematic diagram and geometric parameters of
the proposed MGA unit cell

42. Indium Antimoninde (InSb)
• Semiconductor material from III-V group
• Band gap 1.44ev
• Thermally tuning medium as its electromagnetic properties are very sensitive to
temperature.
• The complexed value of permittivity of InSb is temperature dependent given by Drude
model [48-49];
𝜀 𝑤 = ε∞− ω2
p/(ω2+iωϒ)
where, ε∞ =high freq. permittivity
ϒ= damping constant
ω= angular frequency
ωp= plasma frequency

43. Strontium Titanate (STO)
• Incipient ferroelectric materials
• Dielectric material having unique properties including high dielectric constant, low
dielectric loss, superior insulation, and good chemical stability .
• The most attractive property is that the high dielectric constant of the STO can be
adjusted dynamically by varying external environment temperature or by changing
the applied electric field.
• The permittivity of STO can be calculated by [50];
𝜀 𝑤 = ε∞− F/(𝑘0
2
- 𝑘2 −i 𝑘ϒ)
where, ε∞ =high freq. permittivity=9.6
F(cm-2)= 2.3*106
ko (cm-1) = soft mode wave no
ϒ(cm-1)= damping constant
The relationship between soft mode wave number k0 and damping constant γ with the
external temperature can be expressed as follows:
ϒ 𝑇 = −3.3 + 0.094𝑇
𝑘0 𝑇 = 31.2(𝑇 − 42.5)

44. Temperature dependent permittivity of STO
Real and imaginary value of relative permittivity has been obtained using MATLAB
software [51]
Fig 15a. real part of permittivity of STO with
different temperatures and frequencies
Fig 15b. imaginary part of permittivity of STO with
different temperatures and frequencies

45. Germanium Antimont Telluride (Ge-Sb-Te)
• Phase change material
• Two states: amorphous and crystalline with different electromagnetic characteristics
• The crystallization temp. of GST is 1600c and melting temp. is 6000c.
• GST-based systems provide nearly perfect absorption in the IR and visible light regimes
• Refractive index of GSTs is wavelength-dependent and Dielectric constant of GST is given by
[52-53]:
𝜀𝑥 − 1
𝜀𝑥 + 2
= 𝑥
𝜀𝑐 − 1
𝜀𝑐 + 2
+ 1 − 𝑥
𝜀𝑎 − 1
𝜀𝑎 + 2
where εc = 6.3 & εa = 4.3 are dielectric constant of crystalline (x=1) and
amorphous (x=0) states
GST alloys are known to have advantages over other phase changing material having relatively
lower dissipative loss in near infra red regime and nonvolatility i.e. preserving the
amorphous/crystalline state even in the absence of the input power
• Tunable metamaterials can be realized by the material crystalline phase change, which leads
to the change of dielectric properties. The crystalline phase transition leads to electrical and optical
property changes such as resistivity, color, and refractive indices

46. Graphene
• Graphene, a two-dimensional version of graphite, consists of
a planar atomic layer of carbon atoms bonded in a hexagonal structure.
• Thinnest material having unique property such as optical transparency, flexibility,
high electron mobility .
• Graphene sheet can be managed to have a great conductivity amount due to its high
electron mobility. The electron mobility of this platform can be adjusted either by
chemical doping or gate voltage to produce desired conductivity in the frequency
region of interest
Fig 17. hexagonal lattice of graphene
• Permittivity of graphene given as: [54-55]
𝜀𝑔= 1+i
𝑁𝜎
𝑤𝜀0𝑡𝑔
Where, N =the number of graphene layers
tg= thickness of the graphene plate
ɛ0= permittivity of vacuum
σ = conductivity of graphene

47. Problem Identification
• Dynamic control of EM resonant response for the real time
manipulation in THz radiation
• Dynamic control of THz devices

48. Approaches to be followed
• Hybridization of two or more techniques.
• Use of tunable dielectrics

49. Some of the paper implemented in CST
Equivalent circuit model of an ultra-thin polarization independent triple band
metamaterial absorber
Bhattacharyya, S., Ghosh, S. and Srivastava, K.V., Equivalent circuit model of an ultra-thin
polarization-independent triple band metamaterial absorber. AIP Advances, 4(9), p.097127
(2014).
a= 10mm
w=0.2mm
r1=4.625
r2=3.075mm
r3= 2.15mm
fig 18. top view of unit cell of the proposed absorber

50. Fig 19. comparison of simulated result with that of proposed results

51. Graphene pixel-based polarization-insensitive metasurface for almost
perfect and wideband terahertz absorption
Pankaj kumar,Akhlesh lakhtakia,& Pradip k. Jain Graphene pixel-based polarization-
insensitive metasurface for almost perfect and wideband terahertz absorption Vol. 36, No. 8
/ August 2019 / Journal of the Optical Society of America
a=9.6µm
b=3µm
d=0.2µm
Lsub=9.6µm
Fig 20. top view of meta atoms

52. Fig 21. comparison of simulated result with that of proposed results

53. Sambit Kumar Ghosh, Vinit Singh Yadav, Santanu Das, & Somak Bhattacharyya Tunable Graphene-Based
Metasurface for Polarization-Independent Broadband Absorption in Lower Mid-Infrared (MIR) Range
IEEE Transactions on Electromagnetic Compatibility 1-9
,
Tunable Graphene-Based Metasurface for Polarization-Independent
Broadband Absorption in Lower Mid-Infrared (MIR) Range
a=6µm
q=1µm
d=1µm
n=1µm
c=1.75µm
b=2.5
m=0.125
e=0.25µ
Fig 22a. top view of unit cell Fig 22b. front view of unit cell

54. Fig 23. comparison of simulated result with that of proposed results

55. Future work
• Study of other tunable materials
• Incorporation of materials in devices

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62. 62
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