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Optics and Lasers in Engineering 181 (2024) 108426
Available online 10 July 2024
0143-8166/© 2024 Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Modelling and analysis of a triple-band metamaterial absorber for
early-stage cervical cancer HeLa cell detection
S.M. Anowarul Haque a
, Meraj Ahmed b
, Abdulrahman Alqahtani c,d
,
Mahmudur Rahman Maruf b
, Mohammad Tariqul Islam a
, Md. Samsuzzaman e,f,*
a
Dept. of Electrical, Electronic and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, Bangi 43600, Selangor,
Malaysia
b
Dept. of Electrical and Electronic Engineering, Mymensingh Engineering College, Mymensingh, Bangladesh
c
Department of Biomedical Technology, College of Applied Medical Sciences, Prince Sattam Bin Abdulaziz University, Al-Kharj 11942, Saudi Arabia
d
Department of Medical Equipment Technology, College of Applied Medical Sciences, Majmaah University, Majmaah City 11952, Saudi Arabia
e
Dept. of Computer and Communication Engineering, Faculty of Computer Science and Engineering, Patuakhali Science and Technology University, 8602 Patuakhali,
Bangladesh
f
Faculty of Graduate Studies, Daffodil International University, Daffodil Smart City, Birulia, Savar, Dhaka 1216, Bangladesh
A R T I C L E I N F O
Keywords:
Triple-band
Metamaterial absorber
Cervical cancer cell detection
A B S T R A C T
The paper introduces a unique design and analysis of a terahertz metamaterial absorber (MMA) that can be used
for early detection of cervical cancer by employing microwave imaging techniques. Computer Simulation
Technology (CST) is used to design and analyze the proposed absorber. The MMA operates in the frequency range
of 6–8 THz and can absorb energy in three specific spectral bands: 6.606 THz, 6.824 THz, and 7.426 THz, with
absorption peaks of 99.75 %, 99.87 %, and 99.73 % correspondingly. The working principle of the absorber is
described using the impedance matching and interference theory. The electric field (E), magnetic field (H), and
surface current of the MMA are also examined. Finally, detecting cancerous HeLa cells is also being investigated
by analyzing the E-field and H-field using microwave imaging. The suggested biosensor features a high-quality
factor of 494.3, a frequency shifts per refractive index of 1.08 THz/RIU, and a figure of merit (FOM) of 42. The
suggested MMA-based sensor has numerous advantages and can be utilized for early-stage cervical cancer
detection.
1. Introduction
Cancer is defined as a disease where body cells multiply themselves
unrestrictedly. A cervical cancerous growth originates in the epithelium
of the uterine cervix, where a solitary cell undergoes neoplastic trans
formation. Typically, the process commences in the transitional or
transformation zone, an anatomical region characterized by the merging
of the non-keratinizing squamous epithelium of the exterior cervix, the
exo-cervix, with the columnar epithelium of the inner cervix, the
endocervix. Cervical cancer ranks as the second most prevalent malig
nant condition among women on a global scale, with around 80 % of
reported cases emanating from less developed nations [1]. Globally,
cervical cancer kills more than 300,000 people every year and diagnoses
over half a million women. Most disease occurrences are caused by
high-risk subtypes of the human papillomavirus (HPV). In 2015, 270,
000 people lost their lives to cervical cancer. The mortality rate in low-
and middle-income countries (LMIC) is 18 times greater than in devel
oped countries [2]. Estimates put the lifetime risk of cervical cancer in
Americans at 0.6 % [3]. In 2020, there were an anticipated 604,127
cases of cervical cancer diagnosed worldwide, accounting for 341,831
deaths [4]. By the year 2023–24, it is projected that over 13,960 women
in the United States will receive a diagnosis of incurable cervical cancer,
leading to around 4310 fatalities caused by this condition [5]. Vacci
nation and routine screening have made cervical cancer one of the few
cancers that can be prevented to a significant degree at this time.
Nevertheless, it continues to be a significant burden in numerous cul
tures, especially in places with low economic resources [1].
Early identification significantly improves pre-cancer and cervical
cancer treatment outcomes. Maintaining awareness of cervical cancer
symptoms can reduce delays in detection. The American Cancer Society
* Corresponding author.
E-mail address: sobuz@pstu.ac.bd (Md. Samsuzzaman).
Contents lists available at ScienceDirect
Optics and Lasers in Engineering
journal homepage: www.elsevier.com/locate/optlaseng
https://doi.org/10.1016/j.optlaseng.2024.108426
Received 26 March 2024; Received in revised form 24 June 2024; Accepted 3 July 2024

2
states that people may need additional diagnostic procedures if they
have specific symptoms that point to cancer or if their HPV or Pap test
results show abnormal cells. Colposcopy and cone biopsy are the sug
gested biopsies for a thorough assessment and precise diagnosis. A pelvic
exam performed under anaesthesia, X-ray imaging, CT, MRI, PET, or
PET-CT scans, as well as tumor biomarker testing, are other techniques
used to identify cervical cancer [5]. Cervical cancer is currently most
reliably diagnosed through cervical biopsy; nevertheless, this procedure
is not without its drawbacks, including time requirements, chance for
harm, and dependence on operator expertise. The operation of THz
sensing comes into play at this point. THz sensing is an emerging tech
nique for detecting cervical cancer that provides non-ionizing, non-in
vasive, and timely monitoring of cancer with outstanding sensitivity to
biomolecules and water content. The THz domain is commonly defined
as ranging from 0.1 to 10 THz. It has emerged as a novel research topic in
biology, chemistry, physics, materials research, and healthcare. Ter
ahertz radiation has shown significant promise in biomedical uses for
the last thirty years, primarily because it is non-invasive and does not
require labelling. Radiation from THz has low particle energy, insuffi
cient to induce chemical damage to molecules or dislodge particles from
atoms. It can only penetrate a few hundred micrometres into human
skin. Therefore, it does not induce damaging ionization in biological
tissues, making it highly appealing for medical purposes [6].
Metamaterials are artificially produced substances of sub-
wavelength structural components that exhibit unique electromagnetic
properties not seen in natural materials. The electromagnetic attributes
of such substances are derived based on their design instead of their
chemical composition or band structures [7]. They are artificial mate
rials engineered to provide properties such as perfect lensing [8],
invisibility [9], negative refractive index [10], cross-polarization con
version [11], liquid sensing [12] and perfect absorption [13], etc., which
are not readily available in nature. Metamaterials are more suitable for
terahertz radiation than normal substances due to their electromagnetic
solid reaction, making them highly appealing for future applications
[14]. Xie et al. [15] created a THz metasurface concept allowing
quantitative and qualitative bio-detection. They detected kanamycin
sulfate levels as minimal as ~100 picogram/L by utilizing an array of
square-shaped slits on a silicon substrate at ~0.3 THz, which was ~1010
times more sensitive than the design without a metallic component. Jing
et al. [16] introduced a novel graphene-based absorber with five distinct
peaks in the far infrared spectrum. The suggested absorber has excep
tional controllability and sensitivity, with a determination capability of
up to 22.04 THz/RIU. The absorber’s great sensitivity enables its
application in photothermal detection and thermal radiation. Park et al.
[17] showed the precise identification of viruses employing terahertz
split-ring resonators. They identified two distinct kinds of malware,
PRD1 (60 nm) and MS2 (30 nm), at tiny amounts on the metamaterial
interface. Chen et al. [18] introduced a new design featuring an Eit-like
resonance. It consists of a separated ring resonator with four voids,
supported by a centrosymmetric stacked square ring resonator. The
theoretical values of quality factor (Q), sensitivity (S), and figure of
merit (FOM) were determined to be 30.5, 0.280 THz/RIU, and 8.54,
respectively. The sensor is highly stable to polarization and incident
angles. Wenxin et al. [19] introduced a monolayer graphene absorber
that exhibits significant absorption throughout the frequency range of
3THz to 6 THz. The suggested absorber demonstrates polarization
neutrality and exceptional adjustability. Wenxin et al. [20]have pre
sented a tunable absorber made of an AlCuFe quasicrystal grating
structure, which exhibits a high Q-factor and sensitivity to changes in
refractive index. Parvin et al. proposed a novel spectro-optical sensor
specifically developed for the detection of cancerous cells in various
regions of the human body [21]. The sensitivity values for cervical
cancer, adrenal gland cancer, skin cancer, blood cancer, and type I and
type II breast cancer are 94.96 %, 95.15 %, 94.13 %, 94.84 %, 95.40 %,
and 95.51 % correspondingly, in X-polarization. The authors Saadeldin
et al.have presented and analyzed a novel design of an ideal
metamaterial absorber specifically for terahertz sensing purposes [22].
The structure has a high absorption rate of 99 % at a frequency of 2.249
THz. This absorption is characterized by a narrow and intense resonant
peak, with a Q-factor of 22.05. In addition, the described metamaterial
design can be used as a detector for refractive index (RI), with a high
resolution of 300 GHz/RIU and a FOM of 2.94 over an RI range of 1.0 to
1.39. Shiri Liang et al. [23] introduced a layered structure that includes
Vanadium Dioxide, which shows distinct radiative properties. The sug
gested framework exhibits exceptional temperature, polarization, and
incident angle stability. Using MEMS technology, Zhong et al. [24]
introduced an adjustable terahertz metamaterial (TTM). TTM has a
sensitivity of 0.379 THz/RIU, with mean Q-factor and FOM values of
66.01 and 63.83, respectively. Rahaman et al. [25] created a
hollow-core photonic crystal fibre (HC-PCF) for molecular sensing. By
modifying its physical layout, the recommended HC-PCF acquired an
enhanced absolute response of 96.25 % at an operating frequency of 1
THz. Huang et al. [26] suggested a high-sensitivity sensor of four
semi-elliptic nano-disk graphene structures to measure refractive index.
The sensor’s sensitivity is 11.5 µm/RIU, and the FOM is 3.9 as deter
mined by mathematical estimations. Li et al. [27] proposed an alterna
tive biological sensor utilizing an unbalanced double-ring resonator to
achieve electromagnetic-induced oscillation. The computational study
indicates that the relative sensitivity of each of the three resonance
peaks of the structure is 103.7 GHz/RIU, 107.1 GHz/RIU, and 112.05
GHz/RIU, respectively. The ideal average FOM value for the sensor
formants is 7 (RIU− 1). Hlali et al. [28] proposed studying and evalu
ating a graphene-based sensor that can be adjusted for detecting breast
tumours in the terahertz frequency range. The proposed sensor has a
sensitivity of 7.11 THz/RIU for normal breast tissue and 8.21 THz/RIU
for breast tumours, with merit values of 17.51 and 20.23 RIU− 1
,
respectively. Yang Sui et al. [29] introduced a sensor with a segmented
design capable of detecting cancer cells and identifying glucose solu
tions in both the forward and reverse directions. The layered structure
comprises an analyte layer that serves as a sensor zone containing either
malignant cells or glucose solution. Guo et al. [30] proposed an
ultra-broadband unidirectional absorber based on graphene-embedded
photonic crystals. The structure is developed by arranging the layered
dielectric and graphene materials in a periodic sequence in the THz
frequency range. The device’s relative absorption bandwidth can ach
ieve a remarkable maximum of 94.53 %. The suggested device has ap
plications in optical sensing, solar energy harvesting, and other fields.
Liao et al. [31] created a versatile device capable of converting circular
to linear polarisation and achieving perfect absorption. The device’s
functionality relies on the conductive properties of silicon material,
which are regulated by light. When the device is in PC mode, it has a
relative bandwidth of 38 %. However, when it is in optimal absorption
mode, the device achieves a 77 % absorption rate.
This research uses microwave imaging to introduce a new THz
metamaterial absorber to detect cervical cancer HeLa cells in the 6–8
THz range. In this method, the HeLa cells are investigated using the E
and H fields of the designed material. The study also intends to show the
MMA’s absorption analysis, polarization mechanism, and polarization
and incident angle dependency.
2. MMA unit cell design
The proposed configuration comprises three separate layers: the
uppermost layer (resonator), a dielectric region and a metallic substrate
layer at the bottom. The resonator film and the ground slab are posi
tioned on opposing sides, separated by a dielectric spacer. Gold (Au) is
employed in the resonator and substrate layer. The choice of gold as a
material is based on its high electrical (σ = 4.561e7 Sm-1
) and thermal
conductivity (k = 314.0 W/K/m), which helps to acquire resonance in
the desired frequency band due to its capability of generating induc
tance and capacitance [32]. The gold metal exhibits the following
physical properties: specific heat capacity (Cs) = 0.13 J/K/kg, density =
S.M.A. Haque et al.

3
19,320 kg/m3
, Young’s modulus = 78 GPa, and Poisson’s ratio = 0.42.
Teflon (PTFE) is chosen as the dielectric layer because of its low elec
trical permittivity and low loss tangent, which make it an appropriate
dielectric for THz absorbers. Besides, Teflon (PTFE) has exceptional heat
resistance and notable flexural strength [32]. The optical source for the
MMA is a THz Transverse Electric (TE) wave whose polarization angle
and angle of incidence are zero degrees. Fig. 1 illustrates the unit cell
model of the suggested design, while Table 1 outlines the essential pa
rameters utilized in the design.
Symmetrical design makes an absorber insensitive to polarization
and helps achieve a near-zero polarization conversion ratio (PCR).
Therefore, the resonator structure was designed symmetrically. The foot
area of the unit cell is 75 × 75 μm2
. Fig 1(a) depicts the parameters of the
hexagonal shapes where it can be seen that the size of each inner and
outer arm are a1=12 um and a2=15 um. f1 and f2 are distances across
flats, which are 20.78 um and 25.98 um, respectively. The distances
across the corners for the inner and outer sides are d1=24 um and
d2=30 um, respectively. At the very center, a plus shape consisting of
two flat unsymmetric hexagonal shapes with sharp edges can be
observed, each having the most significant distance across corners of
m1=30 um, whereas m1=15 um and m3=7.94 um are the most sig
nificant and most miniature arms, respectively. Fig. 1(c) illustrates the
thicknesses of different layers of the unit cell. T1=2 um, T2=10.5 um,
T3=1 um, and T4=3 um are the thicknesses of the ground, substrate,
resonator, and cylindrical shape, respectively. The thickness of the
ground layer (T1=2 um) is taken in such way that it can completely
block the terahertz transmission. Usually, transmission is blocked when
the thickness of the ground metallic plate is greater than the skin depth
or penetration depth of the THz wave. Since the bottom metal plate can
entirely obstruct terahertz transmission, augmenting its thickness
should not substantially affect the absorption spectrum. This is because
the transmission has already been decreased to zero, and increasing the
thickness would not alter the material’s absorption properties. Thus, in
theory, the absorption spectrum remains constant despite the increase in
the thickness of the bottom metal plate, provided that it is already thick
enough to prevent terahertz transmission. To validate and verify the
accuracy of the simulation result of the proposed structure, it is neces
sary to investigate the behaviour of the structure under different
boundary conditions. The reliability and consistency of the results can
be ensured by comparing simulations with different boundary condi
tions against analytical solutions, experimental data, or simulations
conducted using other software. All numerical results of the proposed
structure were simulated using the CST Studio Suite software, which
Fig. 1. Design parameters of (a) Hexagonal Shape; (b) Plus and Cylindrical shape; (c) Thicknesses of each layer; of the proposed unit cell shape and the proposed
unit cell.
Table 1
Necessary Parametric Values of the suggested model.
Parameters Hexagonal Shape Plus Shape
L1 a1 d1 f1 a2 d2 f2 θ1 m1 m2 m3 m4 θ2 θ3
Sizes (μm) 75 12 24 20.78 15 30 25.98 120 30 15 7.94 5.2 160.89 38.21
Parameters Cylindrical Shape Thicknesses
Sizes (μm) c1 T4 T1 T2 T3
6 3 2 10.5 1
Fig. 2. Unit cell boundary condition of the proposed unit cell.
S.M.A. Haque et al.

4
Fig. 3. The absorption properties of the unit cell for different designs.
S.M.A. Haque et al.

5
uses the Finite Integration Technique (FIT) [33]. The boundary condi
tions for the Transverse Electromagnetic (TEM) mode consist of a perfect
electric conductor (PEC) in the y-z plane, a perfect magnetic conductor
(PMC) in the x-z plane, and the x-y plane is maintained as an open area
for the propagation of THz waves. The other two analytic techniques, TE
and Transverse Magnetic (TM), employ a Floquet port in the z-direction
and a master-slave relationship in the different dimensions, X and Y. The
X and Y directions are subject to boundary conditions defined as a unit
cell, while an open boundary for the suggested metamaterial absorber
characterizes the Z direction. Fig. 2 depicts the suggested boundary
condition of the metamaterial absorber. The interaction can be
explained using Snell’s law, according to which the reflected light will
be on the same region as the incident wave if the wave propagates from a
right-handed material to a negative indexed material, as shown in Fig. 2.
The conservation of the tangential components of the incident and
refracted wave vectors, as well as the requirement that energy flows
away from the interface (causality principle), are the reasons behind this
[34]. The THz TE wave of zero-degree polarization angle (phi=0◦
) and
normal incidence (Theta=0◦
) wave propagates in the Z direction with a
vertically polarized electric field (Ex) and a horizontally polarized
magnetic field (Hy).
3. Results analysis
3.1. Absorption analysis
The effectiveness of the metamaterial sensor is heavily influenced by
the absorption within the specified frequency range. CST is utilized to
derive performance characteristics like s-parameters and absorption
coefficients through the FIT. The following equation represents the ab
sorption of the suggested metamaterial absorber [33]:
A(ω) = 1 − R(ω) − T(ω) (1)
Here, A(ω) represents the absorption coefficient, R(ω) = |ryy(ω)|2
+
|rxy(ω)|2
= |rxx(ω)|2
+ |ryx(ω)|2
represents the reflected power. |ryy(ω)|2
and |rxx(ω)|2
are the reflectivity of the co-polarized wave, while |rxy(ω)|2
and |ryx(ω)|2
are the reflectivity of the cross-polarized wave [35,36].
T(ω) denotes the transmitted power. The absorber contains a bulk gold
layer at its base that is double the size of the resonator, effectively
preventing the transmission of THz vibrations, resulting in T(ω) = 0.
The revised absorption formula is displayed below:
A(ω) = 1 − R(ω) (2)
To get the best absorption performance, this part explores the critical
study of resonator structures in metamaterial sensor design. To advance
sensor functionality in various applications, it is crucial to understand
the significant effect of resonator configurations on absorption proper
ties. This work clarifies the critical role that resonator design plays in
attaining near-unity absorption by methodical analysis and repeated
refinement. Firstly, an analysis of a resonator consisting exclusively of a
“Plus” shape with sharp edges is presented in Fig. 3(a). This resonator
exhibits absorption peaks at 6.472 THz and 6.716 THz, although it does
not achieve absorption close to unity. Following this, the absorption
properties are improved in Fig. 3(b), where the inclusion of four sym
metrical cylindrical shapes at each sharp edge results in the appearance
of four separate absorption peaks, the highest of which approaches 85 %
absorption. Subsequent investigations entail the incorporation of novel
geometries that preserve the symmetrical nature of the unit cell struc
ture. However, the introduction of triangular shapes in Fig. 3(c) signif
icantly reduces absorption in comparison to Fig. 3(b). Following
iterations, pentagonal forms are introduced, which unveil two absorp
tion peaks that approach unity at 6.823 THz and 7.485 THz. However,
iterative refining was necessary to achieve more peaks with near-unity
absorption. The negative effects of using square and circular shapes
are demonstrated in Figs. 3(e) and 3(f), which show decreased
absorption performance. In the end, the best results are obtained when
hexagonal shapes are used on each side keeping the cylindrical shapes in
the center of each hexagon. At 6.606 THz, 6.82 THz, and 7.42 THz the
three absorption peaks approach unity. The discovery of the best reso
nator structure is the culmination of this rigorous design evaluation
process, which is critical for achieving excellent absorption character
istics in real-world applications.
The proposed absorber can be described in three modes: TE, TM, and
TEM. Eq. (1) quantifies the absorption properties of these modes of
operation based on the s-parameter. Approximately 99.42 %, 99.99 %,
and 99.47 % absorption are found in the TE mode for the resonant
frequency at 6.606 THz, 6.82 THz, and 7.42 THz. Resonant frequencies
at TM modes show a slight positive shift for the first two bands and show
absorption of approximately 99.17 %, 99.81 %, and 99.74 % at 6.608
THz, 6.826 THz, and 7.43 THz. To simulate the proposed absorber in the
TEM mode, PEC and PMC are provided in the x and y-axis, with the z-
axis remaining open. The THz TEM wave propagates towards the posi
tive to the negative z-axis of the absorber. In this mode, the absorber
shows 99.05 %, 99.9 %, and 99.53 % absorption, respectively, 6.604
THz, 6.824 THz, and 7.42 THz. Due to the ultra-symmetrical construc
tion of the overall structure, the absorption characteristics are nearly
identical for the three modes. Fig. 4 illustrates the absorption coefficient
in these three modes. The input electromagnetic wave propagates
perpendicular to the surface of the MMA, resulting in transmission
diffraction according to the generalized Snell’s law (GSL) [20] and
first-order reflection diffraction such as [0, +1] and [0, − 1]. The
transmission diffraction can be disregarded due to the bottom metallic
plate. In this context, the 0th-order reflection refers to the metamaterial
absorber’s reflection coefficient (S11) being considered. In their study,
Zhang et al. [37] demonstrated that the metamaterial absorber exhibits
significantly reduced intensity in the higher-order diffraction modes
when the incident wave is normal to the MMA. This implies that higher
order diffraction may be present, but their effectiveness would be lesser
than spatial reflection or the 0th order diffraction.
The PCR quantifies the effectiveness of a metamaterial or metasur
face in transforming the polarization of an incoming electromagnetic
wave. The PCR value of the suggested MMA is calculated to confirm that
it functions as an absorber rather than a polarization converter. The PCR
value must be close to zero to verify the insensitivity of the suggested
meta-structure unit cell to polarization conversion. Fig. 5(a) indicates
that the cross-polarization component has a negligible value on the
linear magnitude scale, indicating that no waves were transformed by
this design. The validity of this statement can be demonstrated by
computing the PCR values for the suggested structure in both TE and TM
modes, utilizing Eqs. (3) and 4.
Fig. 4. Absorption coefficients in TE, TM and TEM modes.
S.M.A. Haque et al.

6
y to x polarized wave, PCRy =
⃒
⃒rxy(ω)
⃒
⃒2
⃒
⃒ryy(ω)
⃒
⃒2
+
⃒
⃒rxy(ω)
⃒
⃒2
(3)
x to y polarized wave, PCRx =
⃒
⃒ryx(ω)
⃒
⃒2
|rxx(ω)|2
+
⃒
⃒ryx(ω)
⃒
⃒2
(4)
Fig. 5 depicts the co- and cross-polarization components of PCR and
the PCR value obtained at approximately zero in the entire frequency
range.
3.2. Working principle of the MMA
Two widely accepted theories—impedance matching and interfer
ence theory—can elucidate the principles underlying the complete ab
sorption of electromagnetic waves.
3.2.1. Impedance matching
A well-known phenomenon when electromagnetic waves move from
one medium to another is the matching of impedance, in which some
energy is reflected, and the remainder is transmitted. When the char
acteristic impedance of the incident and reflected media are the same,
reflection is reduced. Since air is typically the first medium with a
characteristic impedance of about 377 Ω, near unity absorption can only
be achieved when the absorber’s impedance is close to this value at the
target frequency. S-parameters can be utilized to determine the equiv
alent impedance of the suggested absorber. Here is the formula [38]:
Z =
̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅
(1 + S11)2
− S2
21
(1 − S11)2
− S2
21
√
(5)
Fig. 6 displays the equivalent impedance of the suggested absorber.
The impedance at a frequency of 6.606 THz has a real component of
1.088Ω and an imaginary part of 0.106 Ω. At frequencies of 6.824 THz
and 7.426 THz, the impedance has a real portion with values of 0.92 Ω
and 0.87 Ω and corresponding imaginary values of 0.043 Ω and − 0.22
Ω. At resonance frequencies, the real part of the equivalent impedance is
about equal to one, while the imaginary part is approximately equal to
zero. In other words, the real and imaginary components of the equiv
alent impedance of the suggested absorber exhibit excellent impedance
matching with the surrounding free space. Thus, the absorber exhibits
Fig. 5. (a) Co-polarization and cross-polarization components and (b) PCR for TE and TM modes.
Fig. 6. Equivalent Impedance of the suggested absorber.
Fig. 7. (a) Layered configuration and (b) validation using interference theory and impedance matching.
S.M.A. Haque et al.

7
the most minor reflection in resonance frequency, while the metal layer
prevents transmission, resulting in near-perfect absorption. The de
pendency of absorption upon impedance matching can be understood by
the following equation [39]:
A(ω) =
2z0
Re|Z| + j. Im|Z| − z0
(6)
Here z0 is the impedance of free space. Near unity absorption is achieved
when Real |Z| ≈ 377 ohm and Img |Z| ≈ 0 ohm.
3.2.2. Interference theory
In impedance matching theory, the composite MMA is considered to
be a homogeneous material. As a result, this theory is not appropriate for
analyzing the interaction between the resonator and ground plane [40].
In order to have a deeper understanding of absorption, it is necessary to
quantitatively investigate the mechanism by which the absorber oper
ates. The interference theory is utilized to objectively evaluate the
mechanism of broadband absorption. The structure consists of two
layers: layer 1 and layer 2. We assume that layer 1 is considered a surface
with zero thickness and layer 2 is a perfect reflector. S11 = |S11|ejθ11
is the
reflection coefficient of layer 1 from air to air, S22 = |S22|ejθ22
is the
reflection coefficient of layer 1 from the Perfectly Matched Layer (PML)
to PMI. S21 = |S21|ejθ21
is the transmission coefficient of layer 1 from air
to PML, S12 = |S12|ejθ12
is the transmission coefficient of layer 1 from
PML to air. According to the interference theory [41] and the ground
plane being a perfect reflector total S11 is written as [42]:
∑
S11 = |S11| eJθ11
+
|S12|
2
eJ(θ12+θ21− 2β− π)
1 − |S22|eJ(θ22+θ21− 2β− π)
(7)
Here, β complex propagation phase and β = kd, where k indicates the
wavenumber in the Teflon (PTFE) layer. The peak frequencies of
absorbance derived from the suggested interference theory are
compatible with the simulated frequencies of 6.606, 6.824, and 7.426
THz. The primary cause of the minor changes in frequency can be traced
to the approximation of the complex wave number in the dielectric
medium [43]. Fig. 7 illustrates the absorption curve using interference
theory and impedance matching theory.
3.3. Polarization insensitivity and angular stability
The absorption properties of the proposed absorber were analyzed by
manipulating the polarization and incident angle of the THz wave. The
incident THz wave’s polarization angle was varied from 0 to 90◦
in order
to investigate the parameters of the absorption coefficient. The ab
sorption properties of the suggested absorber stay constant until a po
larization angle of 90◦
is reached. The absorber that was hypothetically
presented is polarization insensitive. This is due to the fact that the
suggested unit cell contains resonators that display rotational symmetry
in both vertical and horizontal orientations. Fig. 8 illustrates the sug
gested absorber’s resistance to polarization effects. Further investigation
was performed to investigate the absorption qualities by altering the
angle at which THz waves were incident. Fig. 9(a) depicts the trans
mission of the incoming wave towards the meta-surface. Fig. 9(b)
Fig. 8. (a) Change of polarization angle in THz wave, (b) absorption characteristics, and (c) color plot for polarization angle insensitivity.
Fig. 9. (a) Changes in the incident angle of the THz wave, (b) absorption characteristics, and (c) colour plot for angular stability.
S.M.A. Haque et al.

8
illustrates the absorption coefficient variation concerning the incidence
angle. The proposed absorber demonstrates that the initial resonance
band remains unaffected by variations in the incidence angle, whereas
the other resonance bands exhibit changes in the absorption peak rela
tive to the incident angle. As the incidence angle is changed from 0◦
to
75◦
, the absorption maxima of the two higher frequency bands shifted
slightly towards higher frequencies while the absorption rate remained
constant. The absorption curve in 9(b) illustrates the changes in ab
sorption qualities as the incidence angle is altered. Fig. 9(c) again
demonstrates the correlation between absorption and incidence angles.
3.4. Parametric study
This part investigates the theoretical assessments of how various
dielectric and resonator materials, the thickness of the dielectric layer,
the thickness of the resonator, and the size of the dielectric layer affect
the absorption properties of the suggested absorber. The selection of
various materials, such as dielectric medium and resonator, can have a
substantial impact on the performance of the proposed absorber.
Exploring different dielectric materials with different absorption co
efficients helps discover how sensitive the absorber is to dielectric
properties. Metals exhibit varying terahertz absorption coefficients,
which directly impact the resonant behavior of metamaterials. An
analysis of several resonator materials assesses their impact on the ab
sorber’s performance. Optimal performance of the absorber is achieved
by altering the dimensions of the dielectric layer. Varying dielectric
layers and resonator thicknesses can potentially modify the performance
of the absorber. By manipulating the thickness of the resonator and
dielectric layers, one can enhance the absorption efficiency by effec
tively managing the coupling between them. The utilization of specific
materials and variations in thickness aids in comprehending the
behavior of the metamaterial absorber and applying it to actual systems.
3.4.1. Effect of different dielectric materials
This section analyzed the absorption properties of the suggested
absorber utilizing various dielectric materials. Teflon (PTFE) with a
permittivity of 2.1 was utilized as a dielectric spacer, revealing three
absorption bands at 6.606 THz, 6.82 THz, and 7.42 THz, each exhibiting
absorption rates of 99.75 %, 99.88 %, and 99.73 % respectively. When
gallium arsenide with a permittivity of 12.94 was utilized as the
dielectric layer, absorption rates of 97.29 % and 60.3 % were observed
at frequencies of 6.128 THz and 6.576 THz. Using GaAs decreased both
the absorption rate and the absorption band. The utilization of the
dielectric polyimide with a permittivity of 3.5 yielded nearly identical
results to those obtained with GaAs. Absorption rates of 99.46 % and
64.52 % were observed at frequencies of approximately 6.08 THz and
6.748 THz. Using polycarbonate (with a permittivity of 2.9) as the
dielectric spacer decreased absorption to 68.17 % at 6.306 THz and
41.64 % at 7.272 THz. Quartz material with a permittivity of 3.75
produced three bands at frequencies of 6.122 THz, 7.186 THz, and 7.72
THz, each having absorption rates of 74.38 %, 58.51 %, and 42.4 %,
respectively. Rogers RT5880 was utilized to detect quad-band fre
quencies of 6.506 THz, 6.718 THz, 7.322 THz, and 7.926 THz, with
absorption rates of 99.99 %, 99.62 %, 64.46 %, and 48.41 %, respec
tively. After examining the absorption properties of several dielectric
materials, it is clear that only Rogers RT5880 closely matched the results
of the Teflon (PETF) substrate. Teflon (PTFE) would be the most effec
tive dielectric material based on the absorption rates of the various
bands. Fig. 10(a) displays the absorption properties of several dielectric
materials.
3.4.2. Effect of varying the thickness of the dielectric layer
This section examines how modifying the thickness of the dielectric
layer impacts absorption properties. The dielectric thickness ranges
from 9 to 11.5 um. When T2 is 9 um, the absorption curve displays four
absorption peaks at 6.058 THz, 6.754 THz, 6.99 THz, and 7.614 THz
Fig. 10. Effect of change in (a) dielectric materials and (b) the thickness of dielectric layer on absorption coefficient.
S.M.A. Haque et al.

9
with absorption rates of 73.22 %, 98.45 %, 98.63 %, and 97.94 %
respectively. Enhancing the thickness to 9.5 results in absorption rates of
58 %, 84 %, 99.3 %, and 90.8 % for frequencies of 6.018 THz, 6.7 THz,
6.928 THz, and 7.546 THz correspondingly. With a 10 um spacer, ab
sorption rates are 96 % at 6.668 THz, 76.9 % at 6.864 THz, and 97.16 %
at 7.496 THz. The triple band with nearly complete absorption occurs at
approximately 6.606 THz, 6.82 THz, and 7.426 THz when a 10.5 um
dielectric spacer is utilized. With a thickness of 11 um, the triple band
remains constant, but the absorption rate reduces to 67.38 % in the
higher band. The absorption rate decreases for the three bands when the
thickness reaches 11.5 um. The analysis indicates that a spacer thickness
of 10.5 um is ideal for the material to exhibit a triple band with near-
unity absorption. Following Fig. 10(b) summarizes the above
description.
3.4.3. Effect of varying the resonator material
The absorption coefficient, A of a metal is related to its complex
dielectric function, ∈ (ω). The Drude model describes the complex
dielectric function which is [44],
∈ (ω) = ε∞ −
ω2
p
ω2 + jω/τ
(8)
Where, ε∞ is the dielectric constant at high frequency, ω2
p is the plasma
frequency and τ is relaxation time. Complex refractive index is defined
as,
N(ω) = n(ω) + jk(ω) (9)
Where, n(ω) is the real part and k(ω) is the imaginary part of the
refractive index. Complex refractive index and complex dielectric con
stant are related by the equation:
N2
(ω) = ϵ(ω) (10)
The absorption coefficient, A(ω) is related to the imaginary part of
the refractive index which is expressed as [45]:
A(ω) =
2ωk(ω)
c
(11)
Where c is the speed of light. Now the imaginary part of the refractive
index is linked with the conductivity of metal via the complex dielectric
constant. At optical frequencies where ω≫1
τ, the absorption coefficient is
written as ([45]):
A(ω) ≈
2τω2
p
2ω2
(12)
The plasma frequency is proportional to the electron density. So,
plasma frequency should be high for a highly conductive metal, and so
should the absorption coefficient [45]. Fig. 11(a) displays the absorption
curve for several metals in the resonator structure. Resonator materials
such as Iron, Tungsten, Aluminum, Gold, Copper, and Silver are utilized,
with respective conductivities of 1E7 S/m, 1.89E7 S/m, 3.56E7 S/m,
4.56E7 S/m, 5.8E7 S/m, and 6.3E7 S/m. The metal’s conductivity
significantly influences the absorption process. Metals with high con
ductivity facilitate better impedance matching, promote robust plas
monic resonance, resulting in heightened local electromagnetic fields
and enhanced absorption. Metals with low electrical conductivity
generally experience significant resistive losses, exhibit poor impedance
matching, and do not facilitate strong plasmonic resonances. Fig. 11(b)
depicts the relationship between conductivity and absorption for several
metals. Metals with high conductivity, such as copper, silver, and gold,
can attain almost perfect absorption, reaching nearly 100 %. Addition
ally, the difference in absorption coefficient among these metals is
minimal. Conversely, materials with lesser conductivity, such as Iron,
Fig. 11. Effect of change in the (a) resonator material on absorption coefficient and (b) relationship between conductivity of metal and absorption.
S.M.A. Haque et al.

10
Aluminum, and tungsten, exhibit reduced absorption compared to gold,
silver, and copper. The graph in 11(b) demonstrates the relationship
between the absorption coefficient and conductivity of different metals.
3.4.4. Effect of varying the size of the dielectric layer
Fig. 12(a) shows the absorption characteristics for different sizes of
the dielectric layer. The absorption response varies slightly while
changing the size of the dielectric layer. An ideal size of 75 μm2
is
selected initially. Reducing the size from 75 μm2
decreases absorption in
the corresponding frequency ranges. Increasing the size to 76 μm2
leads
to a triple band absorption at 6.552 THz, 6.756 THz, and 7.374 THz,
with 87.83 %, 99.22 %, and 99.83 %, respectively. Consuming 77 μm2
leads to a quad-band resonance peak with around 69 % and 66.9 %
absorption levels for the lower and higher bands, respectively. The
absorber will be further analyzed using a size of 75 μm2
.
3.4.5. Effect of varying the thickness of the resonator
Changing the thickness of the resonator impacts the absorption
properties. Fig. 12(b) illustrates how a change in the resonator’s thick
ness affects the absorption curve. Reducing the thickness from 1um
decreases absorption within the corresponding frequency ranges. For a
thickness of 1.4 um, absorption percentages of 75.24 %, 97.5 %, and
99.3 % are observed for frequencies of 6.62 THz, 6.84 THz, and 7.454
THz, respectively. Choosing a thickness of 1.8 micrometers results in
triple-band absorption, with the bottom-band absorption decreasing to
56 %. A resonator material with a 1um thickness was used, resulting in
absorption rates of 99.75 %, 99.87 %, and 99.73 % for frequencies of
6.606 THz, 6.824 THz, and 7.426 THz. Thus, the 1um thickness of the
resonator is chosen for further analysis.
3.5. E-field, H-field and surface current distribution
The electric field (E), magnetic field (H), and surface current distri
bution of the suggested metamaterial absorber are interconnected and
can be explained by Maxwell’s equations [46], which are given below:
∇ × H = J+ ∈
∂E
∂t
(13)
J = σE (14)
Eqs. (13) and 14 establish a relationship between the electric field
and the surface current density. Fig. 13 displays the distribution of the E-
field for the metamaterial absorber being considered. The E-field
strength is detected at the upper and lower edges of the "plus" form when
the frequency is 6.606 THz. This phenomenon is caused by surface
plasmon resonance (SPR) [47]. The region of the substrate’s surface
located between the boundary of the "plus" shape and the cylindrical
form displays a significant electric field due to the occurrence of cavity
surface plasmon resonance (CSPR) [48]. An electric field distribution
arises on the substrate at a frequency of 6.824 THz due to the propa
gation of surface plasmon resonance (PSPR) [49]. Surface plasmons,
when restricted to a metallic structure that is far smaller than the
wavelength of light, become concentrated around the nanostructure at a
particular frequency called localized surface plasmon resonance (LSPR).
When light illuminates a metallic structure, the conduction electrons in
the metal fluctuate in response to the oscillating electric field. When the
electron cloud is moved in relation to the nuclei, a force that pulls the
electrons and nuclei towards each other, called Coulomb attraction, is
generated. This force causes the electron cloud to oscillate in relation to
the nuclear structure. LSPR, an abbreviation for Localized Surface
Plasmon Resonance, refers to the collective oscillation of electrons [50].
LSPR, or localized surface plasmon resonance, enhances absorption by
Fig. 12. Effect of change in the (a) size of the dielectric layer and (b) thickness of the resonator material on absorption coefficient.
S.M.A. Haque et al.

11
generating intense electromagnetic fields that envelop nanoparticles.
This results in a significant improvement in the interactions between
light and matter [51]. The hexagonal shape displays a distinct electric
field distribution at its arms due to LSPR [49]. The minimum wavelength
of light in this context is 37.5 um, corresponding to a frequency of 8 THz.
It is important to note that this wavelength is larger than that of the
metallic resonator in the MMA. The presence of electric and magnetic
field resonances within the resonator pattern at specific frequencies of
6.806, 6.824, and 7.426 THz suggests the occurrence of LSPR.
Conversely, the presence of such resonances within the gaps of the
resonator pattern indicates the occurrence of CSPR. LSPR is applicable
when the size of the "hexagon" structures is less than the wavelength of
the light that induces the plasmon. The distribution of the electric field is
more noticeable at higher frequencies due to the occurrence of SPR and
CSPR. These phenomena happen at the top and bottom edges of the
"plus" structure and on the surface of the substrate between the edge of
the "plus" shape and the cylindrical shape. The "hexagon" structure
displays substantial electric field dispersion from LSPR in the upper and
lower arm, with minimal PSPR at the bulk of the substrate. An analysis
of the magnetic field distribution is also conducted for the absorber
being suggested, as depicted in Fig. 14.
The suggested absorber exhibits a robust magnetic field distribution
at lower frequencies due to SPR, LSPR, and CSPR. When the incident
wave penetrates the unit cell, ground, and resonator metal, it
experiences back-to-back reflection. The EM wave concentrates mainly
on the dielectric spacer shown in 14(d), indicating that the first-order
SPR dominates the absorption [33,52].. This back-to-back reflection of
EM wave generates an intense magnetic field, which is also called
Fabry-Perot Resonance (FPR) [53]. Around a frequency of 6.824 THz,
there is a notable concentration of high magnetic field around the inner
boundaries of the "hexagon" structure and outer edges of the "plus"
structure, attributed to CSPR. Fig. 14(e) demonstrates that the resonator
structure predominantly contains the magnetic field due to Mie reso
nance. In contrast, a smaller portion of the magnetic field is limited to
the dielectric layer, resulting from the second-order SPR resonance [52].
At higher frequencies, the absorber displays a magnetic field distribu
tion as a result of LSPR. There is also some contribution of magnetic field
owing to CSPR, which happens on the substrate’s body in between the
"cylindrical" and the top and bottom edges of the "plus" shape.
Non-uniform magnetic energy is confined in the dielectric layer shown
in Fig. 14(f), indicating first-order SPR’s domination in the absorption
spectrum. The FPR occurs at frequencies of 6.606 THz and 7.426 THz,
generating a uniform and a non-uniform magnetic field, respectively.
Fig. 15 illustrates the magnetic field distribution due to the previously
mentioned FPR at both frequencies. The surface current distribution of
the recommended metamaterial absorber’s top layers was examined to
study the actual absorption process better. The circular flow of anti
parallel current exhibits a strong magnetic response. Fig. 16 shows the
Fig. 13. E-field distribution at (a) 6.606 THz, (b) 6.824 THz and (c) 7.426 THz.
S.M.A. Haque et al.

12
surface current distribution at different resonance frequencies. Dense
current flows through the envelope of the "hexagon" resonator structures
in both clockwise and anti-clockwise directions at lower frequencies.
The concentrated current vectors create a powerful magnetic field at
6.606 THz. The presence of antiparallel current flow indicates a
powerful magnetic field [54]. A circular current flow at a frequency of
6.824 THz in opposite directions within the top and bottom sections of
the hexagon arrangement. Therefore, a powerful magnetic field is
detected in this area. At higher frequencies, dense antiparallel circular
currents flow in the right and left "hexagon" resonator structures. In
contrast, considerably lower dense antiparallel circular currents flow in
the top and bottom "hexagon" resonator structures. As a result, large
magnetic fields are detected in certain areas. The current distribution
affects the alignment of electric and magnetic fields in the plots, whether
parallel or antiparallel. Parallel flow generates an internal magnetic
field that opposes the external magnetic field (H-field) and vice versa
[54].
Fig. 14. H-field distribution at (a) 6.606 THz, (b) 6.824 THz and (c) 7.426 THz and the confined magnetic energy at (d) 6.606 THz, (e) 6.824 THz and (f) 7.426 THz.
Fig. 15. H-field due to FPR at (a) 6.606 THz: uniform and (b) 7.426 THz: non-uniform.
S.M.A. Haque et al.

13
Fig. 16. Surface current distribution at (a) 6.606 THz, (b) 6.824 THz and (c) 7.426 THz.
Fig. 17. (a) Proposed sensor mode, (b) thickness view of the model and (c) experimental setup.
S.M.A. Haque et al.

14
4. Diagnosis of early-stage cervical carcinoma using
Cervical carcinoma starts in the epithelial cells of the cervix when a
single cell turns into a cancerous one. The area of transition is the part of
the cervix where the squamous epithelium on the outside changes into
glandular epithelium on the inside. 47.1 % of new cases of cervical
cancer arise in women younger than 50 years old, so it primarily affects
young adult women [1,55]. HPV (Human papillomavirus) is present in
99.7 % of cervical cancer cases and contributes to its progression [56].
Initial phases are identified by delicately scraping the cervix using a
wooden spatula to gather cells. The process is popularly known as the
’Pap smear’ test, which is the most often used approach for detecting
cervical cancer [55]. However, chemotherapy or neoadjuvant chemo
therapy is the primary treatment option for individuals with advanced
cervical cancer, as the prognosis is typically quite unfavourable [57].
Magnetic resonance imaging (MRI), Computed tomography (CT), and
positron emission tomography (PET) are well-established diagnostic
techniques for identifying early-stage cervical cancer [56,57]. Optical
detection is a potential approach for detecting malignant cells in the THz
range. In this work, the human cervical cancer HeLa cell line was used as
a sample cell to diagnose early-stage cervical carcinoma [57]. The
proposed MTM sensor includes a sample container for cervical HeLa
cells. The malignant cells are extracted from the patient’s cervix. Once
the cells are placed in the sample container, the sensor can differentiate
between regular HeLa cells and cancerous HeLa cells by analyzing their
refractive index. This is done by observing a slight shift in the resonant
peak of the absorption graph from its initial value. The refractive in
dexes (n) of normal and malignant HeLa cells are 1.368 and 1.392,
respectively [58]. By examining the changes in frequency in each
spectral range, it is possible to differentiate cancerous cells from healthy
HeLa cells. By examining the changes in frequency in each spectral
range, it is possible to differentiate cancerous cells from healthy HeLa
cells. Malignant cells possess a greater refractive index compared to
healthy cells. This leads to variations in the intensity of electric and
magnetic fields. Cancer cells exhibit greater sensitivity to the electrical
and magnetic forces produced by healthy cells [54]. By evaluating the
intensity of the E and H fields, it is possible to distinguish healthy cells
from malignant cells. A coverslip of paper material is placed between the
sample holder and the MTM absorber to obtain error-free results.
Figs. 17(a) and 17(b) illustrate the simulation setup of the suggested
MTM absorber-based sensor and Fig. 17(c) illustrates the experimental
setup for detecting early-stage cervical cancer. In this scenario, the THz
source produces a 6–8 THz plane wave as it interacts with the suggested
sensor. The absorption spectrum is derived from the reflected wave
detected by the spectrometric apparatus. An amplifier enhances the
signal and transmits it to a computer, which analyses and predicts the
refractive index of the sample HeLa cells by examining the changes in
the absorption spectrum.
After placing the cervical HeLa cells in the sample holder, a trans
verse electric wave was used to detect the differences in the absorption
curve between healthy and cancerous HeLa cells. Fig. 18 dissipates the
finding of the proposed sensor for normal HeLa cells and malignant HeLa
cells. It shows that five distinct absorption resonance peaks are found to
be sensitive in the range of 6.3 THz to 7.7 THz. The first peak in Fig. 19
(a) shows 95.987 % absorption in 6.438 THz for healthy cells and 97.786
% absorption in 6.428 THz for cancerous cells. There is a 0.01 THz
frequency shift for malignant cells with a 1.799 % increase in the ab
sorption rate. The second peak in Fig. 19(b) is analyzed in the range of
6.77 THz to 6.80 THz. Placing the healthy cells shows 90 % absorption at
6.794 THz, and malignant cells show 89.78 % absorption at 6.778 THz.
The frequency shift observed here is about 0.016 THz. The third peak in
6.866 THz shows 60.56 % absorption for healthy cells, and for the
malignant cells, there is a shift of 0.008 THz, as shown in Fig. 19(c). This
peak shows 60.64 % absorption at 6.858 THz. The fourth peak in Fig. 19
(d) shows the highest frequency shift of 0.026 THz. It shows 97.85 %
absorption at 7.3 THz for healthy and 98.85 % absorption at 7.274 THz
for cancerous cells. The final peak in Fig. 19(e) shows the absorption of
81 % at 7.604 THz for healthy cells and 83.80 % absorption at 7.582 THz
for malignant cells. Here, the calculated frequency shift is 0.022 THz.
This section summarizes that all the absorption peaks are sensitive to the
refractive index of the sample holder, which is changed by placing the
HeLa cells from the cervix. The fourth peak shows the highest sensitivity
of 0.026 THz, and the lowest sensitivity is seen from the third peak,
which is 0.008 THz. Fig. 19 clearly describes the enlarged view of every
peak with their respective absorption and resonance frequency.
The most essential parameters used to measure a sensor’s perfor
mance are sensitivity (S), quality factor (Q), and figure of merit (FOM).
The sensor’s sensitivity is measured in THz/RIU by relating changes in
resonant frequency (Δf) to changes in refractive index (Δn) [54].
S =
Δf
Δn
(15)
Higher Q factors indicate better sensing performance since they
indicate resonant sharpness. The formula for calculating the Q factor is
mentioned below [59]:
Q =
f
FWHM
(16)
Where FWHM means the full-width half maximum of the resonant peak,
the proposed MTM sensor has five distinct resonant peaks at 6.438 THz,
6.794, 6.866 THz, 7.3 THz and 7.604 THz. The FWHM for each of the
three peaks are 0.03672 THz, 0.0199 THZ, 0.01389 THz, 0.051 THz and
0.0421 THz. The selectivity of a sensor is shown by its figure of merit
(FOM), which is calculated by normalizing the sensitivity to the FWHM
of the resonant dip [54].
FOM =
S
FWHM
(17)
An MTM sensor was developed by Hamza et al. for early-stage
diagnosis of non-melanoma skin cancer [54]. The sensor has Q-factors
of 12.8 and 13.5, a sensitivity of 0.0515 THz/RIU and 0.076 THz/RIU,
and an FOM of 0.86 and 1.15. Jiahao et al. designed a tunable meta
material sensor with Q-factors of 57.4 and 44.7, the sensitivity of 0.54
THz/RIU and 1.12 THz/RIU, and FOM of 50.7 and 40 [60]. Hu et al.
presented a graphene-based metamaterial sensor that has a sensitivity of
450 GHz/RIU and 717 GHz/RIU [61]. Chunjian et al. proposed a
graphene-based metamaterial biosensor for breast cancer diagnosis,
which has a quality factor, sensitivity and FOM of 2.43, 1.21 THz/RIU
and 2.75 RIU-1, respectively [62]. A heptad-band metamaterial sensor
was developed by Prince et al. for biomedical applications [63]. The
designed sensor has a maximum quality factor of 117, a sensitivity of
4.72 THz/RIU and an FOM of 44. Ruchi et al. proposed a metamaterial
biosensor for micro-organism detection in which the sensitivity is
Fig. 18. Detection of cervical cancer using MTM biosensor.
S.M.A. Haque et al.

15
calculated in terms of frequency shift [64]. The sensor showed a fre
quency shift of 103 GHz and 95 GHz. Yadgar et al. proposed a dual-band
metamaterial absorber for sensing applications [65]. The sensor has a
sensitivity of 0.0968 THz/RIU and 0.1182 THz/RIU and Q factors of 70
and 126. Nickpay et al. designed a THz refractive index sensor using
graphene material, which had a Q factor of 13.76 and a sensitivity of 851
GHz/RIU [66]. Liao et al. [67] developed a versatile device that operates
as both an absorber and a polarisation converter (PC) in the THz range,
utilizing the photoconductivity effect of Si material. At a conductivity of
silicon of approximately 3500 S/m, the device has an absorption band
that covers over 90 % of the electromagnetic spectrum, ranging from
0.75 to 1.73 THz. This absorption band has an absolute bandwidth of
0.98 THz and a relative bandwidth of 79 %. At a conductivity of around
1 S/m, indicating no illumination, the two copper arcs generated a
photonic crystal band within the frequency range of 0.96–1.47 THz. This
band had an absolute bandwidth of 0.51 THz and a relative bandwidth
of 42 %. Li et al. [68] introduced a metasurface that allows for highly
wideband PC and narrowband absorption by utilizing the phase transi
tion of vanadium dioxide (VO2). At elevated temperatures (68 ◦
C), the
suggested MS demonstrates a limited-range absorption performance
within the 0.67 THz-0.95 THz spectrum. When the temperature falls
below 68 ◦
C, the VO2 transitions into an insulated state, and the struc
ture can be regarded as a PC. Our suggested biosensor has five distinct
bands in the range of 6.3–7.7 THz. Q factor, sensitivity and FOM are
calculated for each of the bands. The proposed biosensor has a quality
factor of 175.3, 341.4, 494.3, 143, and 180.5, a sensitivity of 0.42
THz/RIU, 0.67 THz/RIU, 0.33 THz/RIU, 1.08 THz/RIU and 0.92
THz/RIU and FOM of 42 RIU-1
, 41.88 RIU-1
, 41.25 RIU-1
, 41.5 RIU-1
and
41.8 RIU-1
. The performance of the proposed biosensor is compared with
other literature in Table 2, which may have different types of
bio-applications such as skin cancer detection, breast cancer diagnosis,
micro-organism detection and so on.
Fig. 19. Enlarged view of the (a) first peak, (b) second peak, (c) third peak, (d) fourth peak and (e) fifth peak.
S.M.A. Haque et al.

16
Table 2
Comparison table of MTM-based biosensors of different applications.
Ref. Techniques used Operating
Frequency (THz)
Q S (THz/RIU) FOM (RIU-1
) Applications Published in Year of
publication
[54] Al/PET/Al 0–1.2 12.8, 13.5 0.0515, 0.076 0.86, 1.15 Non-melanoma skin
cancer detection.
IEEE Access 2023
[60] Au/Poli-Si/Si3N4/
Quartz
0.2–20 57.4, 44.7 0.54, 1.12 50.7, 40 Gas, environmental and
biomedical sensors.
Nanomaterials 2021
[61] SiO2/Ion-gel/Air/
Au/Graphene
0.1–20 – 0.45, 0.717 – Analyte sensing Frontiers in
Physics
2022
[62] Graphene/SiO2 0.5–2.5 2.43 1.21 2.75 Breast cancer detection Nanomaterials 2022
[63] Au/Polyimide/Au 1–8.5 117 4.72 44 Biomedical application Scientific Reports 2023
[64] Au/GaAs/Au 0–4 – 0.103, 0.095 – Microorganism detection Scientific Reports 2023
[65] Al/Photoresist/
PET/Quartz
0–1 70, 126 0.0968, 0.1182 – Biomedical application American
Chemical Society
2022
[66] Graphene/SiO2/
Au
2–6 13.76 0.851 – RI biosensor Research Square 2021
Work Au/PTFE
(Teflon)/Au
6–8 175.3, 341.4,
494.3, 143,
180.5
0.42, 0.67,
0.33, 1.08,
0.92
42, 41.88,
41.25, 41.5,
41.8
Early-stage cervical
cancer detection
2024
Fig. 20. The E-field MWI result at 6.606 THz: (a) healthy HeLa cells, (b) cancerous HeLa cells.
S.M.A. Haque et al.

17
Cervical cancer cells can be detected via terahertz imaging due to a
significant frequency disparity in the absorption spectra between
healthy and malignant HeLa cells. This work discusses terahertz imaging
using the dielectric properties of healthy and malignant HeLa cells in the
cervix. The cells are collected from the patient’s cervix which can be
done using the ’Pap smear’ method. These collected cells are placed in
the sample holder of the MTM sensor. Malignant cells possess a greater
refractive index compared to healthy cells. This leads to variations in the
intensity of electric and magnetic fields. Cancer cells exhibit greater
sensitivity to the electrical and magnetic forces produced by healthy
cells [58]. By evaluating the intensity of the E and H fields, it is possible
to distinguish healthy cells from malignant cells. The biosensor under
consideration utilizes terahertz technology that relies on microwave
imaging (MWI). Changes in refractive index are identified by frequency
domain data, which provide geographic details about the target. When a
THz wave interacts with a material in the frequency domain, it alters its
phase due to variations in the target’s refractive index, leading to phase
alterations in different regions of the target. By examining the phase
changes at different locations on the target, it is possible to infer the
spatial arrangement of the object’s internal structure. The spatial dis
tribution of refractive index variations is utilized for image reconstruc
tion to generate images that depict these variations [58]. The proposed
biosensor utilizes MWI to distinguish between healthy and malignant
cervical HeLa cells, allowing the early detection of cervical cancer. The
unit cell absorber shows three distinct absorption peaks at 6.606 THz,
6.824 THz and 7.426 THz. Fig. 20 shows the electric field distribution
for healthy and malignant HeLa cells at 6.606 THz. As shown in Fig. 20
(a), normal skin detects insignificant electric fields. In contrast, in
Fig. 20(b), the bright red sides of the sample holder indicate a very high
electric field, indicating the presence of malignant HeLa cells in the
sample holder. That means, for an exact value of electric field intensity,
the healthy cells are identical to malignant cells. E-field distribution to
detect malignant HeLa cells at 6.824 THz is shown in Fig. 21. Fig. 21(a)
displays the region with lower electric field density, suggesting the ex
istence of healthy cells. Fig. 21(b) displays a very high electric field
density, suggesting the existence of malignant cells in the sample
container. A diagnosis is conducted at 7.426 THz to detect malignant
HeLa cells in Fig. 22. Fig. 22 illustrates a scenario similar to the one
shown previously. Fig. 22(a) displays a reduced E-field intensity over the
sample holder, indicating the presence of healthy cells. Fig. 22(b) dis
plays intense electric field density in the bright red regions, indicating
the presence of malignant HeLa cells. Additional investigations were
conducted to validate the findings by thoroughly examining the mag
netic field. Fig. 23 describes the H-field distribution for both healthy and
Fig. 23. The H-field MWI result at 6.606 THz: (a) healthy HeLa cells, (b) cancerous HeLa cells.
S.M.A. Haque et al.

18
cancerous HeLa cells at 6.606 THz.
Fig. 23(a) shows that the H-field of lower intensity is distributed in
sample holder regions. On the other hand, Fig. 23(b) shows that a highly
intense magnetic field is distributed over a wide area of the sample
holder. The bright red colour indicates a high magnetic field. Due to the
lower intense H-field distribution, Fig. 23(a) indicates the presence of
healthy cells, and due to the high H-field distribution all over the sample
holder region, Fig. 23(b) indicates the presence of cancerous cells.
Fig. 24 illustrates the H-field distribution for both healthy and cancerous
HeLa cells at 6.824 THz. Fig. 24(a) shows lower H-field density, sug
gesting the presence of healthy cells in the sample container. Fig. 24(b)
shows a high magnetic field density in the sensing zone, indicating the
presence of malignant cells on the sample holder. Additional examina
tion is conducted to identify the malignant cells in the specified area of
the sample. There is a significant correlation between the presence of
high magnetic field areas and cancerous HeLa cells. These findings
suggest that magnetic field analysis could serve as a diagnostic tool for
cervical cancer. Fig. 25 shows the H-field distribution in the sample
holder with HeLa cells at 7.426 THz. Fig. 25(a) shows healthy cells in the
sample holder due to the majority of locations having lower magnetic
field intensity. Fig. 25(b) shows malignant HeLa cells in the sample
container due to the majority of its area being covered with an intense
magnetic field distribution. Based on the findings from the MWI
approach, the suggested metamaterial biosensor shows promise in reli
ably and effectively detecting malignant cervical cells. Utilizing this
sensor for early-stage cervical cancer detection allows for fast diagnosis
and treatment. Early detection and treatment will enhance the prospects
and odds of survival of individuals with cervical cancer.
5. Conclusion
The paper demonstrates the modeling and analysis of a novel ter
ahertz metamaterial absorber for detecting early-stage cervical cancer
cells. Various design structures are analyzed, and the selected design
shows 99.75 %, 99.87 %, and 99.73 % absorption rates for frequencies of
6.606 THz, 6.824 THz, and 7.426 THz. The paper examines many ana
lyses, including parametric study, polarization stability analysis, inci
dence angle stability analysis, PCR, E-field, H-field, and surface current
distribution. Finally, early-stage cervical cancer HeLa cells have been
successfully detected utilizing the microwave imaging method. The
S.M.A. Haque et al.

19
suggested biosensor has exceptional quality factors, sensitivity, and
figure of merit. The proposed sensor has numerous advantages and can
be utilized in biomedical applications to distinguish between cancerous
and healthy cervical cells.
Author agreement statement
We the undersigned declare that this manuscript is original, has not
been published before and is not currently being considered for publi
cation elsewhere. We confirm that the manuscript has been read and
approved by all named authors and that there are no other persons who
satisfied the criteria for authorship but are not listed. We further confirm
that the order of authors listed in the manuscript has been approved by
all of us.
We understand that the Corresponding Author is the sole contact for
the Editorial process. He/she is responsible for communicating with the
other authors about progress, submissions of revisions and final
approval of proofs.
CRediT authorship contribution statement
S.M. Anowarul Haque: Writing – review & editing, Writing –
original draft, Visualization, Formal analysis, Data curation. Meraj
Ahmed: Writing – original draft, Investigation, Formal analysis, Data
curation, Conceptualization. Abdulrahman Alqahtani: Writing – re
view & editing, Validation, Methodology, Funding acquisition. Mah
mudur Rahman Maruf: Writing – original draft, Data curation,
Conceptualization. Mohammad Tariqul Islam: Writing – review &
editing, Software, Methodology, Conceptualization. Md. Samsuzza
man: Writing – review & editing, Writing – original draft, Supervision,
Data curation, Conceptualization.
Declaration of competing interest
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
Data availability
No data was used for the research described in the article.
Acknowledgement
This study is supported via funding from Prince Sattam Bin Abdulaziz
University project number (PSAU/2024/R/1445).
References
[1] Bruni L, Alemany L, Diaz M, Bosch FX, de Sanjosé S. Cervical cancer: burden of
disease and risk factors. Women and health. Elsevier; 2013. p. 1159–73.
[2] Cohen PA, Jhingran A, Oaknin A, Denny L. Cervical cancer. The Lancet 2019;393:
169–82.
[3] M. Schwartz and L. Chuang, “Cervical cancer,” 2018.
[4] Singh D, Vignat J, Lorenzoni V, Eslahi M, Ginsburg O, Lauby-Secretan B. Global
estimates of incidence and mortality of cervical cancer in 2020: a baseline analysis
of the WHO global cervical cancer elimination initiative. Lancet Glob Health 2023;
11:e197–206.
[5] Patil DB, Vishwanath T. Integration of deep learning algorithms for precision
cervical cancer analysis from colposcopic images. Int J Intell Syst Appl Engin 2024;
12:539–45.
[6] Yu C, Fan S, Sun Y, Pickwell-MacPherson E. The potential of terahertz imaging for
cancer diagnosis: a review of investigations to date. Quant Imaging Med Surg 2012;
2:33.
[7] Areed NF, El Malt SM, Obayya SS. Broadband omnidirectional nearly perfect
plasmonic absorber for solar energy harvesting. IEEE Photon J 2016;8:1–18.
[8] Fang N, Lee H, Sun C, Zhang X. Sub-diffraction-limited optical imaging with a
silver superlens. Science 2005;308:534–7.
[9] Liu X, Starr T, Starr AF, Padilla WJ. Infrared spatial and frequency selective
metamaterial with near-unity absorbance. Phys Rev Lett 2010;104:207403.
[10] Avitzour Y, Urzhumov YA, Shvets G. Wide-angle infrared absorber based on a
negative-index plasmonic metamaterial. Phys Rev B 2009;79:045131.
[11] Dai L, Zhang Y, Zhang H, O’Hara JF. Broadband tunable terahertz cross-
polarization converter based on Dirac semimetals. Appl Phys Express 2019;12:
075003.
[12] Lin T, Huang Y, Zhong S, Zhong Y, Zhang Z, Zeng Q. Field manipulation of
electromagnetically induced transparency analogue in terahertz metamaterials for
enhancing liquid sensing. Opt Lasers Eng 2022;157:107127.
[13] Wang B-X, Wang G-Z, Huang W-Q. Single metamaterial resonator having five-band
terahertz near-perfect absorption. IEEE Photon Technol Lett 2017;29:1888–91.
[14] Liu C, Yin J, Zhang S. Temperature-tunable THz metamaterial absorber based on
vanadium dioxide. Infrared Phys Technol 2021;119:103939.
[15] Xie L, Gao W, Shu J, Ying Y, Kono J. Extraordinary sensitivity enhancement by
metasurfaces in terahertz detection of antibiotics. Sci Rep 2015;5:8671.
[16] Ma J, Wu P, Li W, Liang S, Shangguan Q, Cheng S. A five-peaks graphene absorber
with multiple adjustable and high sensitivity in the far infrared band. Diam Relat
Mater 2023;136:109960.
[17] Park S, Cha S, Shin G, Ahn Y. Sensing viruses using terahertz nano-gap
metamaterials. Biomed Opt Express 2017;8:3551–8.
[18] Chen T, Zhang D, Huang F, Li Z, Hu F. Design of a terahertz metamaterial sensor
based on split ring resonator nested square ring resonator. Mater Res Express 2020;
7:095802.
[19] Li W, Liu M, Cheng S, Zhang H, Yang W, Yi Z. Polarization independent tunable
bandwidth absorber based on single-layer graphene. Diam Relat Mater 2024;142:
110793.
[20] Li W, Liu Y, Ling L, Sheng Z, Cheng S, Yi Z. The tunable absorber films of grating
structure of AlCuFe quasicrystal with high Q and refractive index sensitivity. Surfac
Interfac 2024;48:104248.
[21] Parvin T, Ahmed K, Alatwi AM, Rashed ANZ. Differential optical absorption
spectroscopy-based refractive index sensor for cancer cell detection. Opt Rev 2021;
28:134–43.
[22] Saadeldin AS, Hameed MFO, Elkaramany EM, Obayya SS. Highly sensitive
terahertz metamaterial sensor. IEEE Sens J 2019;19:7993–9.
[23] Liang S, Xu F, Li W, Yang W, Cheng S, Yang H. Tunable smart mid infrared thermal
control emitter based on phase change material VO2 thin film. Appl Therm Eng
2023;232:121074.
[24] Zhong J, Xu X, Lin Y-S. Tunable terahertz metamaterial with electromagnetically
induced transparency characteristic for sensing application. Nanomaterials 2021;
11:2175.
[25] Rahaman ME, Jibon RH, Mondal HS, Hossain MB, Bulbul AA-M, Saha R. Design
and optimization of a PCF-based chemical sensor in THz regime. Sens Biosensing
Res 2021;32:100422.
[26] McDonnell LP, Viner JJ, Ruiz-Tijerina DA, Rivera P, Xu X, Fal’ko VI. Superposition
of intra-and inter-layer excitons in twistronic MoSe2/WSe2 bilayers probed by
resonant Raman scattering. 2D Materials 2021;8:035009.
[27] Li F, He K, Tang T, Mao Y, Wang R, Li C. The terahertz metamaterials for sensitive
biosensors in the detection of ethanol solutions. Opt Commun 2020;475:126287.
[28] Hlali A, Oueslati A, Zairi H. Numerical simulation of tunable terahertz graphene-
based sensor for breast tumor detection. IEEE Sens J 2021;21:9844–51.
[29] Sui J-Y, Liao S-y, Li B, Zhang H-F. High sensitivity multitasking non-reciprocity
sensor using the photonic spin hall effect. Opt Lett 2022;47:6065–8.
[30] Guo S, Hu C, Zhang H. Unidirectional ultrabroadband and wide-angle absorption in
graphene-embedded photonic crystals with the cascading structure comprising the
Octonacci sequence. JOSA B 2020;37:2678–87.
[31] Liao Sy, Qiao Z, Sui Jy, Zhang Hf. Multifunctional device for circular to linear
polarization conversion and absorption. Ann Phys 2023;535:2300195.
[32] Asgari S, Fabritius T. Multi-band terahertz metamaterial absorber composed of
concentric square patch and ring resonator array. Optics Continuum 2024;3:
148–63.
[33] Shuvo MMK, Hossain MI, Rahman S, Mahmud S, Islam SS, Islam MT. A wide-angle,
enhanced oblique incidence, bend-able metamaterial absorber employed in visible
region with a sun shape resonator. IEEE Access 2021;9:126466–80.
[34] Yao K, Liu Y. Plasmonic metamaterials. Nanotechnol Rev 2014;3:177–210.
[35] Kundu D, Mohan A, Chakrabarty A. Comment on ‘Wide-angle broadband
microwave metamaterial absorber with octave bandwidth. IET Microwaves,
Antennas Propag 2017;11:442–3.
[36] Soliman MM, Islam MT, Alam T, Misran N, Rahim SKA, Alzamil A. Broadband near
unity absorption meta-structure for solar thermophotovoltaic systems and optical
window applications. Nanoscale 2023;15:12972–94.
[37] Zhang Y, Zhou L, Li J-q, Wang Q-j, Huang C-p. Ultra-broadband and strongly
enhanced diffraction with metasurfaces. Sci Rep 2015;5:10119.
[38] Wu Y, Lin H, Xiong J, Hou J, Zhou R, Deng F. A broadband metamaterial absorber
design using characteristic modes analysis. J Appl Phys 2021;129.
[39] Hakim ML, Alam T, Soliman MS, Sahar NM, Baharuddin MH, Almalki SH.
Polarization insensitive symmetrical structured double negative (DNG)
metamaterial absorber for Ku-band sensing applications. Sci Rep 2022;12:479.
[40] Wanghuang T, Chen W, Huang Y, Wen G. Analysis of metamaterial absorber in
normal and oblique incidence by using interference theory. AIP Adv 2013;3.
[41] X.R. Guo, Z. Zhang, J. Wang, and M. Chen, “Design and analysis of frequency
selective surfaces using pinwheel tiling fractal,” 2012, pp. 1901–3.
[42] Chen J, Hu Z, Wang G, Huang X, Wang S, Hu X. High-impedance surface-based
broadband absorbers with interference theory. IEEE Trans Antennas Propag 2015;
63:4367–74.
[43] Zeng X, Gao M, Zhang L, Wan G, Hu B. Design of a triple-band metamaterial
absorber using equivalent circuit model and interference theory. Microw Opt
Technol Lett 2018;60:1676–81.
S.M.A. Haque et al.

20
[44] Chubukov AV, Maslov DL. Optical conductivity of a two-dimensional metal near a
quantum critical point: the status of the extended Drude formula. Physi Rev B
2017;96:205136.
[45] Kostova L. Upper-class travel with a political slant: the destinies of nations and
empires through the eyes of lord and lady strangford. Continental tourism, travel
writing, and the consumption of culture. 2020. p. 177–200. 1814–1900.
[46] Hakim ML, Alam T, Almutairi AF, Mansor MF, Islam MT. Polarization insensitivity
characterization of dual-band perfect metamaterial absorber for K band sensing
applications. Sci Rep 2021;11:17829.
[47] Lai R, Shi P, Yi Z, Li H, Yi Y. Triple-band surface plasmon resonance metamaterial
absorber based on open-ended prohibited sign type monolayer graphene.
Micromachines (Basel) 2023;14:953.
[48] Bhattarai K, Silva S, Song K, Urbas A, Lee SJ, Ku Z. Metamaterial perfect absorber
analyzed by a meta-cavity model consisting of multilayer metasurfaces. Sci Rep
2017;7:10569.
[49] Fann C-H, Zhang J, ElKabbash M, Donaldson WR, Campbell EM, Guo C. Broadband
infrared plasmonic metamaterial absorber with multipronged absorption
mechanisms. Opt Express 2019;27:27917–26.
[50] Fattahi Z, Khosroushahi AY, Hasanzadeh M. Recent progress on developing of
plasmon biosensing of tumor biomarkers: efficient method towards early stage
recognition of cancer. Biomed& Pharmacother 2020;132:110850.
[51] Soliman MM, Islam MT, Alam T, Misran N, Chowdhury MEH, Alshammari AS.
Wideband close perfect meta surface absorber for solar photovoltaic and optical
spectrum applications. Surfac Interfac 2024;45:103849. 2024/02/01/.
[52] Feng H, Li X, Wang M, Xia F, Zhang K, Kong W. Ultrabroadband metamaterial
absorbers from ultraviolet to near-infrared based on multiple resonances for
harvesting solar energy. Opt Express 2021;29:6000–10.
[53] Bilal R, Saeed M, Choudhury P, Baqir M, Kamal W, Ali MM. Elliptical metallic
rings-shaped fractal metamaterial absorber in the visible regime. Sci Rep 2020;10:
14035.
[54] Hamza MN, Islam MT. Designing an extremely tiny dual-band biosensor based on
MTMs in the Terahertz Region as a perfect absorber for non-melanoma skin cancer
diagnostics. IEEE Access 2023;11:136770–81.
[55] Bosch FX, De Sanjosé S. Chapter 1: human papillomavirus and cervical
cancer—burden and assessment of causality. JNCI Monographs 2003:3–13. 2003.
[56] Skinner MK. Encyclopedia of reproduction. Academic Press; 2018.
[57] Li H-N, Nie F-F, Liu W, Dai Q-S, Lu N, Qi Q. Apoptosis induction of oroxylin A in
human cervical cancer HeLa cell line in vitro and in vivo. Toxicology 2009;257:
80–5.
[58] Elhelw AR, Ibrahim MSS, Rashed ANZ, Mohamed AE-NA, Hameed MFO,
Obayya SSA. Highly sensitive triple-band THz metamaterial biosensor for cancer
cell detection. IEEE Photon J 2023.
[59] Lu X, Ge H, Jiang Y, Zhang Y. Design and analysis of a dual-band THz metamaterial
sensor with high refractive index sensitivity. Front Phys 2022;10:973033.
[60] Yang J, Lin Y-S. Design of tunable terahertz metamaterial sensor with single-and
dual-resonance characteristic. Nanomaterials 2021;11:2212.
[61] Hu H, Qi B, Zhao Y, Zhang X, Wang Y, Huang X. A graphene-based THz
metasurface sensor with air-spaced structure. Front Phys 2022;10:990126.
[62] Tan C, Wang S, Li S, Liu X, Wei J, Zhang G. Cancer diagnosis using terahertz-
graphene-metasurface-based biosensor with dual-resonance response.
Nanomaterials 2022;12:3889.
[63] Jain P, Chhabra H, Chauhan U, Prakash K, Gupta A, Soliman MS. Machine learning
assisted hepta band THz metamaterial absorber for biomedical applications. Sci
Rep 2023;13:1792.
[64] Bhati R, Malik AK. Multiband terahertz metamaterial perfect absorber for
microorganisms detection. Sci Rep 2023;13:19685.
[65] Abdulkarim YI, Altintas O, Karim AS, Awl HN, Muhammadsharif FF, Alkurt FOz.
Highly sensitive dual-band terahertz metamaterial absorber for biomedical
applications: simulation and experiment. ACS omega 2022;7:38094–104.
[66] Nickpay M-R, Danaie M, Shahzadi A. Highly sensitive THz refractive index sensor
based on folded split-ring metamaterial graphene resonators. Plasmonics 2021:
1–12.
[67] Liao S, Sui J, Zhang H. Switchable ultra-broadband absorption and polarization
conversion metastructure controlled by light. Opt Express 2022;30:34172–87.
[68] Li Y, Zeng L, Zhang H, Zhang D, Xia K, Zhang L. Multifunctional and tunable
metastructure based on VO 2 for polarization conversion and absorption. Opt
Express 2022;30:34586–600.
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