Next Article in Journal
Synergistic Interaction of Clusters of Iron Oxide Nanoparticles and Reduced Graphene Oxide for High Supercapacitor Performance
Next Article in Special Issue
Alkaline Electro-Sorption of Hydrogen Onto Nanoparticles of Pt, Pd, Pt80Pd20 and Cu(OH)2 Obtained by Pulsed Laser Ablation
Previous Article in Journal
Geometric Optimization of Perovskite Solar Cells with Metal Oxide Charge Transport Layers
Previous Article in Special Issue
Reconfigurable, Stretchable Strain Sensor with the Localized Controlling of Substrate Modulus by Two-Phase Liquid Metal Cells
 
 
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Tunable Optimal Dual Band Metamaterial Absorber for High Sensitivity THz Refractive Index Sensing

1
Department of Communication, School of Electronics Engineering, Vellore Institute of Technology, Vellore 632014, India
2
Department of Electronics and Communication Engineering, Sri Manakula Vinayagar Engineering College, Puducherry 605107, India
3
School of Electrical Engineering, Vellore Institute of Technology, Vellore 632014, India
4
Functional Materials and Microsystems Research Group, Royal Melbourne Institute of Technology University, Melbourne, VIC 3001, Australia
5
School of Computer Science and Engineering, Vellore Institute of Technology, Vellore 632014, India
6
School of Electronics Engineering, Vellore Institute of Technology, Chennai 600127, India
*
Author to whom correspondence should be addressed.
Nanomaterials 2022, 12(15), 2693; https://doi.org/10.3390/nano12152693
Submission received: 15 July 2022 / Revised: 26 July 2022 / Accepted: 28 July 2022 / Published: 5 August 2022

Abstract

:
We present a simple dual band absorber design and investigate it in the terahertz (THz) region. The proposed absorber works in dual operating bands at 5.1 THz and 11.7 THz. By adjusting the graphene chemical potential, the proposed absorber has the controllability of the resonance frequency to have perfect absorption at various frequencies. The graphene surface plasmon resonance results in sharp and narrow resonance absorption peaks. For incident angles up to 8°, the structure possesses near-unity absorption. The proposed sensor absorber’s functionality is evaluated using sensing medium with various refractive indices. The proposed sensor is simulated for glucose detection and a maximum sensitivity of 4.72 THz/RIU is observed. It has a maximum figure of merit (FOM) and Quality factor (Q) value of 14 and 32.49, respectively. The proposed optimal absorber can be used to identify malaria virus and cancer cells in blood. Hence, the proposed plasmonic sensor is a serious contender for biomedical uses in the diagnosis of bacterial infections, cancer, malaria, and other diseases.

1. Introduction

The extraordinary qualities of graphene have inspired investigators to learn more about its many potential uses [1,2,3]. The most interesting property of graphene is the perfect absorption of terahertz (THz) radiation, which makes it suitable for applications such as sensors [4], detectors [5], cloaking devices [6], thermal emitters [7], modulators [8], and so on. The ease in tuning the graphene operating frequency by varying the electric field or chemical doping paves the way for designing the narrow and multi-band absorbers suitable for high sensitivity THz sensing. Recently, researchers have been looking into the use of ultrathin [9], ultrasensitive absorption-based sensors [10,11,12], and biosensors with a narrow [13] and ultra-narrowband response [14,15,16]. THz sensors have wide range of medical applications [17,18]. They are also called optical biosensors, which detect biomolecules directly in real-time [19]. Fluorescence and label-free detection are two techniques of sensing using the optical biosensors. The label-free technique, which uses surface plasmon resonance (SPR), is a low cost method compared to the fluorescence method [20]. The interaction of incident photons and free electrons on the surface of the metal results in the non-radiative electromagnetic mode is known as surface plasmon resonance (SPR). On the medium and metal surface, it is an excited state that spreads locally. It is only present on the surface of the medium or metal, where the surface intensity is greatest, and it gradually weakens on both sides in the direction perpendicular to the surface [21,22,23]. A wide-band absorber made up of a metal plate and a patterned vanadium dioxide film separated by a dielectric layer is proposed in [24], in which the temperature control enables the absorption intensity to be changed from 0 to 0.999. The absorber structure is the basis of these sensors. The absorbers having a sensitive absorption spectrum and narrow bandwidth are used to produce high sensitivity sensors [25].
Numerous graphene based absorbers have been proposed with multilayer structures and wideband absorption. One of the strong interactions that has recently been included into the metasurface system is bound states in the continuum (BIC), which is capable of encapsulating electromagnetic wave energy in the metasurface without radiation leakage [26]. To lessen plasmonic wave power loss, Vanani et al., have introduced a double waveguide THz sensor made of graphene and GaAs. Instead of using the standard double waveguide mode, they have placed a tiny ring in place of one of the waveguides to increase the structure’s sensitivity by using constrained supermodes [27]. In [28], a graphene based multi-layer absorber structure was proposed. By using a Al2O3 layer between two patterned graphene layers, four narrow absorption peaks are achieved. However, the bands have a large full width half maximum (FWHM) range, and the patterned graphene is more difficult to fabricate than the graphene sheet. In [29], using different patterns in three layers, a wideband absorber was proposed. It exhibits an absorption range of 0.3 THz to 3 THz. Using cross-over elliptic dielectric structures above the graphene layer, a wideband absorber was reported in [30]. However, the structure is not simple to fabricate. It was suggested in [31] that it is hard to fabricate the absorber with a multilayer structure. A narrowband absorption peak with simple structure was reported in [25]. The proposed structure exhibits only one narrowband. Hence, it is desired to have a simple structure absorber with narrow and multi-band absorption peaks for efficient sensing.
With this motive, some THz sensors have been proposed using graphene [32] and using other methods [33,34]. A gold ring and a graphene disk was used to produce Fano type resonances, thereby enabled ultrasensitive sensing in [35]. In [10], a high figure of merit (FOM) and sensitivity sensor was proposed by integrating a Fabry-Perot cavity and graphene based gratings.
In this study, a rather simplistic and compact absorber structure with a dual absorption peak for sensing applications is suggested. A single layer of graphene and an incredibly thin layer of SiO2 substrate with a thickness of 3 μ m make up the suggested absorber. On top of the graphene sheet, there are four gold bars. Dual narrow band absorption peaks are produced by this configuration. Due to the narrow bandwidth of both of the dual absorption peaks, it is suitable for sensing applications. The structure of this paper is as follows: First, we describe the basic construction of the absorber and how different parameters affect the absorption peaks. Second, a highly sensitive sensor application based on the absorber has been suggested and evaluated. The dual narrow-band, uncomplicated structure, tunability, and controllability of the proposed absorber are its key benefits.

2. Design Structure and Model

In this section, the proposed absorber unit cell structure is depicted with a single sheet of graphene and four small sized gold bars. Figure 1a shows the 3D view of the proposed absorber. It consists of a gold metasurface array at the top. Gold bars with height h g and width w are placed in the form of a 2 × 2 array. Beneath the gold bars and above the substrate there is a graphene layer which has a thickness t g and chemical potential ( μ c ). Due to a dependence of the graphene surface plasmon’s (GSPs) properties on the substrate, the graphene layer is grown on a silicon dioxide SiO2 substrate with thickness h s and ε r = 2.25 [10]. Hence, the GSPs properties and absorption peaks will vary for a small variation in dielectric [36,37]. The GSPs structure’s key benefits are variation in its conductivity by bias voltage or chemical doping, low loss, and tunability [38,39]. To lessen the transmission, a gold layer with thickness h g and conductivity σ = 4.56 × 10 7 S / m [31] is used.
Figure 1b shows the top view of the absorber. The distance between the gold bars in the x   axis and y   axis is kept at d g and y g , respectively. At the centre, the graphene layer is placed with a dimension of l g × w g . The increased absorption in SiO2 is due to the high conductivity of the graphene.
The Fabry-Perot cavity between gold layers and graphene traps the incident wave that passes through SiO2 layer. As shown in the Figure 1a, the incident wave is applied in the z-axis. To excite the GSPs, the incident wave’s electric field is polarised in the x-direction at the graphene-substrate interface. Due to GSPs and incident wave interaction, perfect absorption is achieved by graphene. Furthermore, the high confinement of GSPs makes the Fabry-Perot cavity resonance strong and results in the perfect absorption by the proposed absorber. The Kubo’s formula can be used to estimate the conductivity of the graphene as follows:
σ ω = j e 2 μ c π h ω + j τ 1 + j e 2 4 π h ln 2 μ c h ω + j τ 1 2 μ c + h ω + j τ 1
where e = 1.6 × 10 19   C , ω , μ c , τ , and h are the electron charge, angular frequency, graphene chemical potential, relaxation time, and reduced Planck constant. We assume 1   p s as the value of the relaxation time [40]. Graphene supports surface plasmons by acting as a thin metal layer due to the graphene’s positive imaginary part conductivity and dominant intra-band, i.e., the first term in (1) [10,41]. Using [40], the graphene tenability can be obtained as follows:
μ c = h v f π ε 0 ε r V g e t g
where V g is the external bias voltage and v f = 10 6 m s is the Fermi velocity. From (2), it is obvious that by varying V g , the μ c can be varied. This allows for the graphene responding in many ways. Table 1 provides the optimum parameters for the required absorption peaks.

3. Results and Analysis

The proposed gold metasurface based absorber for sensor application is simulated using CST Microwave Studio software based on three dimensional (3D) FDTD techniques. The unit cell’s z-direction is surrounded by an open boundary condition, whereas, in the x and y direction, the periodic boundary condition has been used. The absorption coefficient ( A ) is determined using A = 1 S 11 2 S 21 2 , where S 11 and S 21 are the reflection coefficient and transmission coefficients, respectively. The evolution process is represented by the three stages in Figure 2. Figure 3 depicts an improvement in absorption peaks for different evolutionary phases from Figure 2. The figure shows that, in the absence of gold bars, the absorption weakens at f = 11.7 THz. After placing the gold bars, nearly 100% absorption is found with two discrete resonant peaks. The first peak with a resonance frequency of 5.1 THz has an FWHM of 0.3223 THz, where FWHM is full width at half maximum. Here, FWHM corresponds to 50% absorption. As per the definition of quality factor Q [4,42,43], the first peak Q value is 15.823. The resonance frequency of the second peak is observed at 11.7 THz, with an FWHM of 0.308 THz. The corresponding second peak Q value is 38.407. The second peak is narrower and has a high Q value when compared with the first peak. The simple structure absorbers in the literature do not possess two discrete narrowbands with high Q value.
Further, to evaluate the dependency of resonance frequency on structural parameter and to produce the optimized design, parametric analysis has been carried out. The proposed absorber will have a perfect absorption if the Fabry-Perot cavity resonance is coupled to GSP resonance. This can be achieved through the optimal selection of μ c . Hence, the effect of μ c on the resonance is given in Figure 4. It can be noticed that at μ c = 0.5 , the absorption is maximum at two frequencies, i.e., f = 5.1   and   11.7 THz. The other values of μ c have resulted in imperfect absorption. However, it has been reported in [25] that, through proper selection of w g and μ c , any desired resonance frequency can be achieved.
As mentioned, w g impacts the electromagnetic wave confinement in the absorber. Hence, the effect of w g is studied and depicted in Figure 5. It is noticed that by varying w g , the desired frequency of operation can be achieved. However, the second resonance, i.e., f = 11.7 THz, shifts with the diminished absorption.
Hence, w g = 5   μ m is chosen in the final design. Next, the effect of variation in substrate height h s is analysed and presented in Figure 6. On changing h s , the absorption bandwidth is varied at the cost of reduced absorption. This can be observed from the Figure 6. The optimized value is chosen as h s = 3 , since it provides a compromise between narrow bandwidth and perfect absorption at two resonance frequencies.
The impact of incidence angle on the absorption spectrum is seen in Figure 7. Although the suggested absorber depends on the polarisation of the incoming wave, it is clear from the figure that it is independent of incident angles below 80°. Figure 8 depicts the sensing process using an analyte medium. The properties of graphene surface plasmons change with the changing refractive index of the analyte medium. Hence, we analysed different analyte thickness in THz region using the proposed absorber.
The frequency shift of the proposed sensor depends on the analyte thickness. It can be seen from Figure 9 that a maximum shift in frequency occurs when t a = 2   μ m . When the thickness is increased further, the shift in absorption becomes saturated. Hence, we have chosen t a = 2   μ m for analysing the sensing capabilities of the proposed dual band absorber.
Figure 10 shows the shift in resonance frequency when the refractive index changes from n = 1 to n = 2 . It can be observed that without much deterioration in absorption, there is a shift in absorption frequency. This proves that refractive index sensing can be performed with the help of the presented absorber structure.
Figure 11 displays the observed electric field magnitude ( | E | ) distribution at the absorption frequencies of 5.1 THz and 11.1 THz. It seems to be that the electric component of the incident wave is orthogonal to the graphene and dielectric interface, where the GSPs are stimulated. As can be seen in Figure 5, the excited GSP and, consequently, the absorption structure are affected by the value of w g .

4. Refractive Index Sensing of Glucose

Sensing quality of THz sensors can be measured by two main parameters, sensitivity ( S ) and figure of merit F O M . The sensitivity ( S ) can be found using S = Δ f / Δ n   THz / RIU . The figure of merit is determined using F O M = S / F W H M . Here, FWHM is full width at half maximum. The refractive index of water is n w = 1.3198 and that of 25% glucose in water is n g w = 1.3594 [37]. For the analyte thickness of t a = 2   μ m , we have obtained the value mentioned in Table 2. It can be noticed that the proposed dual band absorber structure has attained a sensitivity of 2.08 THz / RIU and 4.72 THz / RIU in sensing water with 25% glucose at I and II resonant peak, respectively. This high value of sensitivity is due to the narrow bandwidth of the absorption spectrum.

5. Detection of Malaria

Around 250 million individuals worldwide contract malaria each year, making quick malaria screening essential [44]. A healthy red blood cell (RBC) has a refractive index of 1.399. Additionally, as malaria progresses, an infected RBC’s refractive indices are 1.383 and 1.373 in the trophozoite and schizont phases, respectively. As demonstrated in Table 3, the proposed sensor is capable of detecting various stages of malaria. The previous section claimed that a 2 μ m analyte thickness offers good sensing capability. In order to identify malaria, we therefore set the analyte thickness to 2 μ m . The proposed sensor has comparably achieved a high sensitivity value of 1.76 THz / RIU and 3.72 THz / RIU at the I and II resonant peak, respectively.
The proposed sensor can be fabricated using standard techniques. Additionally, because it has undergone extensive research, the recommended sensor has the capacity for ultra-high sensing for a variety of applications, including the detection of water contaminants or the detection of malaria.
In Table 4, a comparative analysis is shown. Recent reported structures in the literature are compared to the suggested work. Comparing the suggested absorber to recently reported alternative sensors, it performs better in terms of sensitivity, FOM, and Q-factor. In addition, the suggested tunable absorber offers a narrow geometry with superior angular and polarisation stability.
Recent fabrication and reporting of several biosensors based on metamaterials demonstrates a strong agreement between the results of simulation and measurement [42,51,52]. The belief that the absorber/sensor described in this article will function as anticipated if experimentally implemented in the future is reinforced by this latest research [42,51,52]. In addition, this structure can be constructed using a clear and precise method that is fully described in [53]. Using a shadow mask during the graphene’s plasma enhanced chemical vapour deposition (PECVD), the suggested method makes it possible to fabricate graphene in any shape on a SiO2 substrate. Other strategies and approaches for producing graphene with dimensions less than a nanometer have been researched and are presented in [54].

6. Conclusions

In this study, we suggest a THz absorber for sensor use. Due to the confinement of the graphene surface plasmon, the suggested absorber exhibits an extremely precise and condensed absorption peak. The simulation findings demonstrate the response’s tunability by adjusting the graphene chemical potential, which aids in having a perfect absorption at a specific frequency. Additionally, it is demonstrated that the response is insensitive to the angles of incidence up to 80°. With a high sensitivity of 4.72 THz/RIU, FOM of 13.88, and high Q value of 32.49, the proposed absorber can be a suitable candidate for bio-medical applications. This sensor is a suitable choice for THz sensing, such as glucose detection and malaria illness diagnosis, because of its simple design, ease of production, and good responsiveness.

Author Contributions

Conceptualization and Methodolgy, M.K.; validation, M.K. and P.J.; software, S.S.D.; formal analysis, S.R. and T.S.; data curation, M.P.; writing original draft preparation, M.K. All authors have read and agreed to the published version of the manuscript.

Funding

All authors would like to thank the authorities of VIT Vellore for extending financial support for this publication.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Geim, A.K.; Novoselov, K.S. The rise of graphene. Nat. Mater. 2007, 6, 183–191. [Google Scholar] [CrossRef] [PubMed]
  2. Peres, N.M.R. Colloquium: The transport properties of graphene: An introduction. Rev. Mod. Phys. 2010, 82, 2673–2700. [Google Scholar] [CrossRef] [Green Version]
  3. Bonaccorso, F.; Sun, Z.; Hasan, T.; Ferrari, A.C. Graphene photonics and optoelectronics. Nat. Photonics 2010, 4, 611–622. [Google Scholar] [CrossRef] [Green Version]
  4. Yahiaoui, R.; Tan, S.; Cong, L.; Singh, R.; Yan, F.; Zhang, W. Multispectral terahertz sensing with highly flexible ultrathin metamaterial absorber. J. Appl. Phys. 2015, 118, 083103. [Google Scholar] [CrossRef]
  5. Wang, J.; Gou, J.; Li, W. Preparation of room temperature terahertz detector with lithium tantalate crystal and thin film. AIP Adv. 2014, 4, 027106. [Google Scholar] [CrossRef]
  6. Shi, H.; Ok, J.G.; Won Baac, H.; Jay Guo, L. Low density carbon nanotube forest as an index-matched and near perfect absorption coating. Appl. Phys. Lett. 2011, 99, 211103. [Google Scholar] [CrossRef] [Green Version]
  7. Diem, M.; Koschny, T.; Soukoulis, C.M. Wide-angle perfect absorber/thermal emitter in the terahertz regime. Phys. Rev. B—Condens. Matter Mater. Phys. 2009, 79, 033101. [Google Scholar] [CrossRef] [Green Version]
  8. Savo, S.; Shrekenhamer, D.; Padilla, W.J. Liquid crystal metamaterial absorber spatial light modulator for THz applications. Adv. Opt. Mater. 2014, 2, 275–279. [Google Scholar] [CrossRef]
  9. Li, H.; Yuan, L.H.; Zhou, B.; Shen, X.P.; Cheng, Q.; Cui, T.J. Ultrathin multiband gigahertz metamaterial absorbers. J. Appl. Phys. 2011, 110, 014909. [Google Scholar] [CrossRef]
  10. Yan, F.; Li, L.; Wang, R.; Tian, H.; Liu, J.; Liu, J.; Tian, F.; Zhang, J. Ultrasensitive Tunable Terahertz Sensor with Graphene Plasmonic Grating. J. Light. Technol. 2019, 37, 1103–1112. [Google Scholar] [CrossRef]
  11. Liu, S.; Li, L.; Bai, Z. Highly sensitive biosensor based on partially immobilized silver nanopillars in the terahertz band. Photonics 2021, 8, 438. [Google Scholar] [CrossRef]
  12. Chen, J.; Nie, H.; Tang, C.; Cui, Y.; Yan, B.; Zhang, Z.; Kong, Y.; Xu, Z.; Cai, P. Highly sensitive refractive-index sensor based on strong magnetic resonance in metamaterials. Appl. Phys. Express 2019, 12, 052015. [Google Scholar] [CrossRef]
  13. Cheng, R.; Xu, L.; Yu, X.; Zou, L.; Shen, Y.; Deng, X. High-sensitivity biosensor for identification of protein based on terahertz Fano resonance metasurfaces. Opt. Commun. 2020, 473, 125850. [Google Scholar] [CrossRef]
  14. Liao, Y.L.; Zhao, Y. Ultra-narrowband dielectric metamaterial absorber with ultra-sparse nanowire grids for sensing applications. Sci. Rep. 2020, 10, 1480. [Google Scholar] [CrossRef] [Green Version]
  15. Wang, B.X.; Huang, W.Q.; Wang, L.L. Ultra-narrow terahertz perfect light absorber based on surface lattice resonance of a sandwich resonator for sensing applications. RSC Adv. 2017, 7, 42956–42963. [Google Scholar] [CrossRef] [Green Version]
  16. Liang, Y.; Lin, H.; Lin, S.; Wu, J.; Li, W.; Meng, F.; Yang, Y.; Huang, X.; Jia, B.; Kivshar, Y. Hybrid anisotropic plasmonic metasurfaces with multiple resonances of focused light beams. Nano Lett. 2021, 21, 8917–8923. [Google Scholar] [CrossRef]
  17. Siegel, P.H. Terahertz technology in biology and medicine. IEEE Trans. Microw. Theory Tech. 2004, 52, 2438–2447. [Google Scholar] [CrossRef]
  18. Shi, Y.Z.; Xiong, S.; Chin, L.K.; Yang, Y.; Zhang, J.B.; Ser, W.; Wu, J.H.; Chen, T.N.; Yang, Z.C.; Hao, Y.L.; et al. High-resolution and multi-range particle separation by microscopic vibration in an optofluidic chip. Lab Chip 2017, 17, 2443–2450. [Google Scholar] [CrossRef]
  19. Khansili, N.; Rattu, G.; Krishna, P.M. Label-free optical biosensors for food and biological sensor applications. Sens. Actuators B Chem. 2018, 265, 35–49. [Google Scholar] [CrossRef]
  20. Shi, X.; Zhang, X.; Yao, Q.; He, F. A novel method for the rapid detection of microbes in blood using pleurocidin antimicrobial peptide functionalized piezoelectric sensor. J. Microbiol. Methods 2017, 133, 69–75. [Google Scholar] [CrossRef]
  21. Chen, H.; Chen, Z.; Yang, H.; Wen, L.; Yi, Z.; Zhou, Z.; Dai, B.; Zhang, J.; Wu, X.; Wu, P. Multi-mode surface plasmon resonance absorber based on dart-type single-layer graphene. RSC Adv. 2022, 12, 7821–7829. [Google Scholar] [CrossRef]
  22. Deng, Y.; Cao, G.; Wu, Y.; Zhou, X.; Liao, W. Theoretical Description of Dynamic Transmission Characteristics in MDM Waveguide Aperture-Side-Coupled with Ring Cavity. Plasmonics 2015, 10, 1537–1543. [Google Scholar] [CrossRef]
  23. Deng, Y.; Cao, G.; Yang, H.; Zhou, X.; Wu, Y. Dynamic Control of Double Plasmon-Induced Transparencies in Aperture-Coupled Waveguide-Cavity System. Plasmonics 2017, 13, 345–352. [Google Scholar] [CrossRef]
  24. Zheng, Z.; Luo, Y.; Yang, H.; Yi, Z.; Zhang, J.; Song, Q.; Yang, W.; Liu, C.; Wu, X.; Wu, P. Thermal tuning of terahertz metamaterial absorber properties based on VO2. Phys. Chem. Chem. Phys. 2022, 24, 8846–8853. [Google Scholar] [CrossRef]
  25. Nejat, M.; Nozhat, N. Ultrasensitive THz Refractive Index Sensor Based on a Controllable Perfect MTM Absorber. IEEE Sens. J. 2019, 19, 10490–10497. [Google Scholar] [CrossRef]
  26. Hsu, C.W.; Zhen, B.; Stone, A.D.; Joannopoulos, J.D.; Soljacic, M. Bound states in the continuum. Nat. Rev. Mater. 2016, 1, 16048 . [Google Scholar] [CrossRef] [Green Version]
  27. Vanani, F.G.; Fardoost, A.; Safian, R. Design of double ring label-free terahertz sensor. IEEE Sens. J. 2019, 19, 1293–1298. [Google Scholar] [CrossRef]
  28. Faraji, M.; Moravvej-Farshi, M.K.; Yousefi, L. Tunable THz perfect absorber using graphene-based metamaterials. Opt. Commun. 2015, 355, 352–355. [Google Scholar] [CrossRef]
  29. Rahmanzadeh, M.; Rajabalipanah, H.; Abdolali, A. Multilayer graphene-based metasurfaces: Robust design method for extremely broadband, wide-angle, and polarization-insensitive terahertz absorbers. Appl. Opt. 2018, 57, 959. [Google Scholar] [CrossRef] [PubMed]
  30. Nejat, M.; Nozhat, N. Design, Theory, and Circuit Model of Wideband, Tunable and Polarization-Insensitive Terahertz Absorber Based on Graphene. IEEE Trans. Nanotechnol. 2019, 18, 684–690. [Google Scholar] [CrossRef]
  31. Fu, P.; Liu, F.; Ren, G.J.; Su, F.; Li, D.; Yao, J.Q. A broadband metamaterial absorber based on multi-layer graphene in the terahertz region. Opt. Commun. 2018, 417, 62–66. [Google Scholar] [CrossRef]
  32. Xu, W.; Xie, L.; Zhu, J.; Tang, L.; Singh, R.; Wang, C.; Ma, Y.; Chen, H.T.; Ying, Y. Terahertz biosensing with a graphene-metamaterial heterostructure platform. Carbon 2019, 141, 247–252. [Google Scholar] [CrossRef]
  33. Al-Naib, I. Evaluation of amplitude difference referencing technique with terahertz metasurfaces for sub-micron analytes sensing. J. King Saud Univ.-Sci. 2019, 31, 1384–1387. [Google Scholar] [CrossRef]
  34. Al-Naib, I. Thin-Film Sensing via Fano Resonance Excitation in Symmetric Terahertz Metamaterials. J. Infrared Millime. Terahertz Waves 2018, 39, 1–5. [Google Scholar] [CrossRef]
  35. Zhang, Y.; Li, T.; Zeng, B.; Zhang, H.; Lv, H.; Huang, X.; Zhang, W.; Azad, A.K. A graphene based tunable terahertz sensor with double Fano resonances. Nanoscale 2015, 7, 12682–12688. [Google Scholar] [CrossRef]
  36. Babaei, F.; Javidnasab, M.; Rezaei, A. Supershape nanoparticle plasmons. Plasmonics 2017, 13, 1491–1497. [Google Scholar] [CrossRef] [Green Version]
  37. Li, G.; Chen, X.; Li, O.; Shao, C.; Jiang, Y.; Huang, L.; Ni, B.; Hu, W.; Lu, W. A novel plasmonic resonance sensor based on an infrared perfect absorber. J. Phys. D Appl. Phys. 2012, 45, 205102. [Google Scholar] [CrossRef]
  38. Gómez-Díaz, J.S.; Perruisseau-Carrier, J. Graphene-based plasmonic switches at near infrared frequencies. Opt. Express 2013, 21, 15490. [Google Scholar] [CrossRef] [Green Version]
  39. Hosseininejad, S.E.; Komjani, N.; Noghani, M.T. A Comparison of Graphene and Noble Metals as Conductors for Plasmonic One-Dimensional Waveguides. IEEE Trans. Nanotechnol. 2015, 14, 829–836. [Google Scholar] [CrossRef]
  40. Huang, M.; Cheng, Y.; Cheng, Z.; Chen, H.; Mao, X.; Gong, R. Based on graphene tunable dual-band terahertz metamaterial absorber with wide-angle. Opt. Commun. 2018, 415, 194–201. [Google Scholar] [CrossRef]
  41. Bahadori-Haghighi, S.; Ghayour, R.; Sheikhi, M.H. Three-Dimensional Analysis of an Ultrashort Optical Cross-Bar Switch Based on a Graphene Plasmonic Coupler. J. Light. Technol. 2017, 35, 2211–2217. [Google Scholar] [CrossRef]
  42. Cong, L.; Tan, S.; Yahiaoui, R.; Yan, F.; Zhang, W.; Singh, R. Experimental demonstration of ultrasensitive sensing with terahertz metamaterial absorbers: A comparison with the metasurfaces. Appl. Phys. Lett. 2015, 106, 031107. [Google Scholar] [CrossRef]
  43. Hu, X.; Xu, G.; Wen, L.; Wang, H.; Zhao, Y.; Zhang, Y.; Cumming, D.R.S.; Chen, Q. Metamaterial absorber integrated microfluidic terahertz sensors. Laser Photon. Rev. 2016, 10, 962–969. [Google Scholar] [CrossRef] [Green Version]
  44. Liu, P.Y.; Chin, L.K.; Ser, W.; Chen, H.F.; Hsieh, C.M.; Lee, C.H.; Sung, K.B.; Ayi, T.C.; Yap, P.H.; Liedberg, B.; et al. Cell refractive index for cell biology and disease diagnosis: Past, present and future. Lab Chip 2016, 16, 634–644. [Google Scholar] [CrossRef]
  45. Chen, C.Y.; Yang, Y.H.; Yen, T.J. Unveiling the electromagnetic responses of fourfold symmetric metamaterials and their terahertz sensing capability. Appl. Phys. Express 2013, 6, 022002. [Google Scholar] [CrossRef]
  46. Wang, B.X.; Zhai, X.; Wang, G.Z.; Huang, W.Q.; Wang, L.L. A novel dual-band terahertz metamaterial absorber for a sensor application. J. Appl. Phys. 2015, 117, 014504. [Google Scholar] [CrossRef]
  47. Taylor, A.J.; Smirnova, E.; Brener, I.; Han, J.; O’Hara, J.F.; Singh, R.; Zhang, W. Thin-film sensing with planar terahertz metamaterials: Sensitivity and limitations. Opt. Express 2008, 16, 1786–1795. [Google Scholar] [CrossRef]
  48. Zhang, B.; Duan, J.; Xu, Y.; Liu, Y. Flexible ultrawideband microwave metamaterial absorber with multiple perfect absorption peaks based on the split square ring. Appl. Opt. 2018, 57, 10257–10263. [Google Scholar] [CrossRef]
  49. Yan, X.; Liang, L.-J.; Ding, X.; Yao, J.-Q. Solid analyte and aqueous solutions sensing based on a flexible terahertz dual-band metamaterial absorber. Opt. Eng. 2017, 56, 27104. [Google Scholar] [CrossRef] [Green Version]
  50. Varshney, G.; Giri, P. Bipolar charge trapping for absorption enhancement in a graphene-based ultrathin dual-band terahertz biosensor. Nanoscale Adv. 2021, 3, 5813–5822. [Google Scholar] [CrossRef]
  51. Padilla, W.J.; Averitt, R.D. Properties of dynamical electromagnetic metamaterials. J. Opt. 2017, 19, 084003. [Google Scholar] [CrossRef]
  52. Gupta, M.; Srivastava, Y.K.; Manjappa, M.; Singh, R. Sensing with toroidal metamaterial. Appl. Phys. Lett. 2017, 110, 121108. [Google Scholar] [CrossRef]
  53. Kim, Y.S.; Joo, K.; Jerng, S.K.; Lee, J.H.; Yoon, E.; Chun, S.H. Direct growth of patterned graphene on SiO2 substrates without the use of catalysts or lithography. Nanoscale 2014, 6, 10100–10105. [Google Scholar] [CrossRef] [PubMed]
  54. Bai, J.; Zhong, X.; Jiang, S.; Huang, Y.; Duan, X. Graphene nanomesh. Nat. Nanotechnol. 2010, 5, 190–194. [Google Scholar] [CrossRef]
Figure 1. (a) 3D view of the graphene based absorber. (b) 2D top view of the presented absorber.
Figure 1. (a) 3D view of the graphene based absorber. (b) 2D top view of the presented absorber.
Nanomaterials 12 02693 g001
Figure 2. Development stages of the proposed absorber. (a) Stage I, (b) Stage II (c) Final design.
Figure 2. Development stages of the proposed absorber. (a) Stage I, (b) Stage II (c) Final design.
Nanomaterials 12 02693 g002
Figure 3. Absorption coefficient (A) of the different structures reported in Figure 2.
Figure 3. Absorption coefficient (A) of the different structures reported in Figure 2.
Nanomaterials 12 02693 g003
Figure 4. Effect of μ c in absorption (A) spectra.
Figure 4. Effect of μ c in absorption (A) spectra.
Nanomaterials 12 02693 g004
Figure 5. Effect of w g in absorption (A) spectra.
Figure 5. Effect of w g in absorption (A) spectra.
Nanomaterials 12 02693 g005
Figure 6. Effect of h s in absorption (A) spectra.
Figure 6. Effect of h s in absorption (A) spectra.
Nanomaterials 12 02693 g006
Figure 7. Absorption plot for various incident angles and different frequency.
Figure 7. Absorption plot for various incident angles and different frequency.
Nanomaterials 12 02693 g007
Figure 8. Proposed sensors with analyte thickness of t a .
Figure 8. Proposed sensors with analyte thickness of t a .
Nanomaterials 12 02693 g008
Figure 9. Dependency of frequency shift on analyte thickness.
Figure 9. Dependency of frequency shift on analyte thickness.
Nanomaterials 12 02693 g009
Figure 10. Effect of test medium refractive index n in absorption (A) spectra.
Figure 10. Effect of test medium refractive index n in absorption (A) spectra.
Nanomaterials 12 02693 g010
Figure 11. (a) Electric field magnitude distribution monitored at I Peak. i.e., f = 5.1 THz and (b) Electric field distribution monitored at II Peak. i.e., f = 11.7 THz.
Figure 11. (a) Electric field magnitude distribution monitored at I Peak. i.e., f = 5.1 THz and (b) Electric field distribution monitored at II Peak. i.e., f = 11.7 THz.
Nanomaterials 12 02693 g011
Table 1. Proposed absorber’s optimized dimensions.
Table 1. Proposed absorber’s optimized dimensions.
ParameterValueParameterValue
w s 9   μ m d g 2   μ m
l s 5   μ m y g 0.9   μ m
w g 5   μ m h s 3   μ m
l g 2   μ m h g 0.2   μ m
μ c 0.5 ev T 300   K
τ 1   ps t g 0.34   nm
Table 2. Performance of the proposed absorber for sensing 25% glucose in water.
Table 2. Performance of the proposed absorber for sensing 25% glucose in water.
Δ f
THz
F W H M
THz
Δ n S
THz / RIU
FOM Q
Refractive index changes from nw = 1.3198 to ng = 1.3594I Resonant Peak 0.08270.310.3962.086.7014
II Resonant Peak0.1870.340.3964.7213.8832.49
Table 3. Proposed sensor’s sensing parameters for malaria diagnosis.
Table 3. Proposed sensor’s sensing parameters for malaria diagnosis.
n Changes from 1.399 to S
THz / RIU
FOM
( RIU 1 )
Q
I PeakII PeakI PeakII PeakI PeakII Peak
1.3831.523.424.9010.0515.3634.13
1.3731.763.725.6710.9415.4334.28
Table 4. Performance evaluation of the suggested absorber in contrast to the existing absorbers.
Table 4. Performance evaluation of the suggested absorber in contrast to the existing absorbers.
Ref.No of Bands S (I Peak, II Peak)
THz / RIU
FOM
( RIU 1 )
f
THz
TunablilityPolarization Insensitive upto the Angle in °Thickness in
μ m
[27]10.1662.823.82YesNot reported30
[35]11.96.5611.5YesNot reported1
[45]10.131.043.7NoNot reported5
[46]11.4824.63NoNot reported10
[25]14.713.845.71Yes703
[43]20.22,
3.5
1.1,
7
0.71,
6.4
NoInsensitive2
[47]20.0001, –0.5,
1.425
NoNot Reported642
[48]20.1875,
0.360
7.2,
19.1
1.8,
2.26
No308.6
[49]20.147,
0.964
1.21,
17.28
1.08,
2.77
NoNot Reported10.4
[50]21.35,
2.95
4.67,
8.8
4.88,
10.9
YesInsensitive2.52
This
work
22.08
4.72
6.7,
13.88
5.1,
11.7
Yes803
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Karthikeyan, M.; Jayabala, P.; Ramachandran, S.; Dhanabalan, S.S.; Sivanesan, T.; Ponnusamy, M. Tunable Optimal Dual Band Metamaterial Absorber for High Sensitivity THz Refractive Index Sensing. Nanomaterials 2022, 12, 2693. https://doi.org/10.3390/nano12152693

AMA Style

Karthikeyan M, Jayabala P, Ramachandran S, Dhanabalan SS, Sivanesan T, Ponnusamy M. Tunable Optimal Dual Band Metamaterial Absorber for High Sensitivity THz Refractive Index Sensing. Nanomaterials. 2022; 12(15):2693. https://doi.org/10.3390/nano12152693

Chicago/Turabian Style

Karthikeyan, Madurakavi, Pradeep Jayabala, Sitharthan Ramachandran, Shanmuga Sundar Dhanabalan, Thamizharasan Sivanesan, and Manimaran Ponnusamy. 2022. "Tunable Optimal Dual Band Metamaterial Absorber for High Sensitivity THz Refractive Index Sensing" Nanomaterials 12, no. 15: 2693. https://doi.org/10.3390/nano12152693

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop