Simulation and lithographic fabrication of a triple band terahertz metamaterial absorber coated on flexible polyethylene terephthalate substrate

Hu D., Meng T., Wang H., Fu M.

A tunable metamaterial absorber (MA) with dual-broadband and high absorption properties at terahertz (THz) frequencies is designed in this work. The MA consists of a periodic array of flower-like monolayer graphene patterns at top, a SiO2 dielectric spacer in middle, and a gold ground plane at the bottom. The simulation results demonstrate that the designed MA has two wide absorption bands with an absorption of over 90% in frequency ranges of 0.68 THz–1.63 THz and 3.34 THz–4.08 THz, and the corresponding relative bandwidths reach 82.3% and 20%, respectively. The peak absorptivity of the absorber can be dynamically controlled from less than 10% to nearly 100% by adjusting the graphene chemical potential from 0 eV to 0.9 eV. Furthermore, the designed absorber is polarization-insensitive and has good robustness to incident angles. Such a high-performance MA has broad application prospects in THz imaging, modulating, filtering, etc.

Mohanty A., Acharya O.P., Appasani B., Mohapatra S.K., Khan M.S.

This paper presents and evaluates a new terahertz metamaterial absorber (MMA) for sensing applications. Because of its unique properties, metamaterial-based sensors are widely employed in a variety of applications. The reported structure comprises of two identical metallic patches, a dielectric spacer and a ground metal plane. The finite element approach has been utilized to simulate and analyse the design. It is found that the MMA offered a prominent resonant peak with near 100% absorbance at frequency 4.5 THz due to the resultant effect of coupling between the two identical patches. In addition, surface current distribution, absorption mechanism and structural parametric analysis has also been investigated. The peak is designated as ‘A’, with a line width of 0.02 THz and a quality factor (Q-factor) of 225, which is sensitive to the refractive index of the environment (RI). As a result of its highly sensitive sensing capabilities, the proposed design can be employed as a sensor for refractive index, having 1.6 THz per refractive index unit (RIU) sensitivity and figure of merit (FoM) of 80 in terms of change in RI of the environment. The majority of biomedical samples have RI of 1.3 to 1.36, which is worth highlighting. Thus, biomedical applications may be possible with the suggested sensor.

Ryu M., Ng S.H., Anand V., Lundgaard S., Hu J., Katkus T., Appadoo D., Vilagosh Z., Wood A.W., Juodkazis S., Morikawa J.

Capabilities of the attenuated total reflection (ATR) at THz wavelengths for increased sub-surface depth characterisation of (bio-)materials are presented. The penetration depth of a THz evanescent wave in biological samples is dependent on the wavelength and temperature and can reach 0.1–0.5 mm depth, due to the strong refractive index change ∼0.4 of the ice-water transition; this is quite significant and important when studying biological samples. Technical challenges are discussed when using ATR for uneven, heterogeneous, high refractive index samples with the possibility of frustrated total internal reflection (a breakdown of the ATR reflection mode into transmission mode). Local field enhancements at the interface are discussed with numerical/analytical examples. Maxwell’s scaling is used to model the behaviour of absorber–scatterer inside the materials at the interface with the ATR prism for realistic complex refractive indices of bio-materials. The modality of ATR with a polarisation analysis is proposed, and its principle is illustrated, opening an invitation for its experimental validation. The sensitivity of the polarised ATR mode to the refractive index between the sample and ATR prism is numerically modelled and experimentally verified for background (air) spectra. The design principles of polarisation active optical elements and spectral filters are outlined. The results and proposed concepts are based on experimental conditions at the THz beamline of the Australian Synchrotron.

Abdulkarim Y.I., Özkan Alkurt F., Awl H.N., Muhammadsharif F.F., Bakır M., Dalgac S., Karaaslan M., Luo H.

In this work, a new metamaterial design is proposed to yield an ultra-thin and dual band metamaterials perfect absorber (MPA) to be operated in the frequency range from 15 to 35 THz. The proposed structure is consisted of a copper resonator deposited on a very thin Zinc Selenide ZnSe (0.6 μm) substrate, where the backside of the structure is covered with a metal plate to block the transmission of electromagnetic waves. Computer Simulation Technology (CST) was used to design and investigate the proposed structure. The absorption response of the proposed structure was found to be high enough with absorptivity of 98.44 and 99.28 at 22.46 THz and 28.95 THz, respectively. Results showed that the absorber is insensitive to the incident angle of 0°–60° in both transverse electric (TE) and transverse magnetic (TM) modes, respectively. The MPA was seen to be highly independent on the angles of polarization of the incident waves. The working mechanism of the proposed design was revealed by multiple reflection interference theory and a good agreement was confirmed between the calculated and simulated results. The proposed design can be used for possible applications of stealth technology and imaging.

Molero G., Tsai C., Liu C., Sue H., Uenuma S., Mayumi K., Ito K.

The mechanical and scratch behaviors of polyrotaxane (PR) modified poly(methyl methacrylate) (PMMA) were investigated. PR is a necklace-like supramolecule with rings threaded onto a linear backbone chain that is capped by bulky end groups. Cyclodextrin (CD) serves as the ring structure and can be functionalized to induce specific interactions with the hosting polymer matrix. To systematically investigate the effect of CD functionalization on the mechanical properties of PMMA, PR with polycaprolactone (PCL) grafted chains on CD, and PR with methacrylate functional groups at the terminal of the PCL grafted chains on CD were chosen for this study. Tensile and compressive true stress–strain tests, ASTM scratch test, and coefficient of friction measurements were conducted to fundamentally understand how PR influences the mechanical and scratch behaviors of PMMA. Additionally, dielectric relaxation spectroscopy and dynamic mechanical analysis were conducted to explore how PR influences the relaxation dynamics of PMMA. The above findings suggest that the methacrylate functional group on PR induces favorable molecular interactions with PMMA matrix, leading to enhanced molecular cooperativity during deformation, which in turn improves tensile and compressive properties and achieves greatly improved scratch resistance.

Wang J., Lang T., Hong Z., Xiao M., Yu J.

We presented and manufactured a triple-band terahertz (THz) metamaterial absorber with three concentric square ring metallic resonators, a polyethylene terephthalate (PET) layer, and a metallic substrate. The simulation results demonstrate that the absorptivity of 99.5%, 86.4%, and 98.4% can be achieved at resonant frequency of 0.337, 0.496, and 0.718 THz, respectively. The experimental results show three distinct absorption peaks at 0.366, 0.512, and 0.751 THz, which is mostly agreement with the simulation. We analyzed the absorption mechanism from the distribution of electric and magnetic fields. The sensitivity of the three peaks of this triple-band absorber to the surrounding is 72, 103.5, 139.5 GHz/RIU, respectively. In addition, the absorber is polarization insensitive because of the symmetric configuration. The absorber can simultaneously exhibit high absorption effect at incident angles up to 60° for transverse electric (TE) polarization and 70° for transverse magnetic (TM) polarization. This presented terahertz metamaterial absorber with a triple-band absorption and easy fabrication can find important applications in biological sensing, THz imaging, filter and optical communication.

Zamzam P., Rezaei P.

In this paper, a new model of multi-layer metamaterial perfect absorber (MPA) in the terahertz region has been introduced. This model is similar to the classic absorber model, ie the three traditional layers of metal-dielectric-metal. The difference is that the middle layer has changed in height and consists of 3 separate layers with the same material. Therefore, the middle layer of the proposed structure is metamaterial. Numerical results of the simulation show that the absorption rate of the perfect absorber at 6.86 THz is 99.99%. Also, by changing the width of the two middle layer columns w, a dual-band perfect absorber with an average absorption rate of 97.18% is obtained at frequencies of 4.24 THz and 6.86 THz. A significant advantage of this paper over other works is that this absorber is adjustable, in addition to obtaining a nearly perfect dual-band absorber with a narrow-band peak by adjusting the parameters and also a nearly broad-band absorber can also be obtained by changing the parameters without re-manufacturing the structure. We believe that the proposed absorber has potential in filtering, detection and imaging.

Poorgholam-Khanjari S., Zarrabi F.B.

Demand for an antenna with high gain and directivity for medical sensing is necessary so the Vivaldi antenna in the THz spectrum with reconfigurable characteristics is a proper solution. Antenna design with a higher gain and bandwidth can be a remarkable choice for THz sensing. Thus, in this work, a Vivaldi antenna is developed for 0.5 to 2 THz with more than 120% bandwidth. To obtain the reconfigurable characteristics, the graphene slabs can be used for this type of antenna to improve the bandwidth when the chemical potential is changed from 0.1 to 0.7 eV. Using the graphene slabs can affect both the gain and return loss of the antenna. Therefore, to modify the return loss, the graphene plasmonic nano-ribbons are used and silicon slabs are improvised between the graphene to reduce its drawback by providing a hyperbolic metamaterial lens. The hyperbolic metamaterial lens can concentrate the electric field to compensate for the graphene loss. The final antenna gain is increased up to 11.5 dBi, which makes it attractive for biosensing. This antenna is used for recognizing the cancerous and healthy skin tissue in the THz spectrum. • Antenna with high gain and directivity for medical sensing is necessary so the Vivaldi antenna in the THz spectrum. • A Vivaldi antenna is developed for 0.5 to 2 THz with more than 120% bandwidth. • To obtain the reconfigurable characteristics, the graphene slabs can be used for this type of antenna. • The graphene plasmonic nano-ribbons are used and silicon slabs are improvised between the graphene to reduce its drawback by providing a hyperbolic metamaterial lens.

Zhu H., Zhang Y., Ye L., Li Y., Xu Y., Xu R.

In this paper, we propose and demonstrate a switchable terahertz metamaterial absorber with broadband and multi-band absorption based on a simple configuration of graphene and vanadium dioxide (VO2). The switchable functional characteristics of the absorber can be achieved by changing the phase transition property of VO2. When VO2 is insulating, the device acts as a broadband absorber with absorbance greater than 90% under normal incidence from 1.06 THz to 2.58 THz. The broadband absorber exhibits excellent absorption performance under a wide range of incident and polarization angles for TE and TM polarizations. Moreover, the absorption bandwidth and intensity of the absorber can be dynamically adjusted by changing the Fermi energy level of graphene. When VO2 is in the conducting state, the designed metamaterial device acts as a multi-band absorber with absorption frequencies at 1 THz, 2.45 THz, and 2.82 THz. The multi-band absorption is achieved owing to the fundamental resonant modes of the graphene ring sheet, VO2 hollow ring patch, and coupling interaction between them. Moreover, the multi-band absorber is insensitive to polarization and incident angles for TE and TM polarizations, and the three resonance frequencies can be reconfigured by changing the Fermi energy level of graphene. Our designed device exhibits the merits of bi-functionality and a simple configuration, which is very attractive for potential terahertz applications such as intelligent attenuators, reflectors, and spatial modulators.

Yuan C., Yang R., Wang J., Tian J.

We report an all-graphene-dielectric terahertz metamaterial absorber/reflector, whose absorption bandwidth and absorptivity can be tuned by applying the bias voltage to regulate the Fermi energy of the patterned graphene. When no bias voltage is applied, it acts as a reflector; when regulating the bias voltage applied to the different parts of the patterned graphene, its bandwidth of over 90 % absorptivity can be increased to 1.75 THz, correspond to relative absorption bandwidth to 60.9 %.The mechanism for tunable enhanced absorption bandwidth is analyzed through the impedance matching and the surface current distributions. In addition, the broadband absorber is insensitive to both the polarization angle and the incident angle. Our research provides a candidate for designing tunable broadband graphene-based absorbers in terahertz frequencies.

Baqir M.A., Naqvi S.A.

This communication investigates the spectral features of metamaterial-based absorber operating in the terahertz frequency band. Metamaterial-based absorber is comprised of copper (Cu) and graphene strips loaded over a silicon dioxide (SiO2) glass substrate. The absorptivity of the proposed absorber is analyzed by varying the chemical potential of the graphene and the slant angle of Cu strips. The results demonstrate that absorption band can be tuned by varying the chemical potential of graphene and the slant angle of copper strip. Such an absorber would be useful for the terahertz filtering and sensing applications in integrated optics.

Cheng X., Huang R., Xu J., Xu X.

Broadband terahertz (THz) absorbers are highly desired in detection, modulation, receiving, and imaging devices. We report the design and successful implementation of a novel broadband THz metasurface with a near-perfect absorption. Different from the traditional metal/dielectric/metal three-layer structures, the as-designed THz absorber has one more metal layer and a dielectric spacer on top, both of which are 200 nm thick. Although the total thickness increased by ∼7%, the near-perfect THz absorption band significantly broadened by 4×, achieving a broadband absorption of 270 GHz. Broadband, polarization-insensitive, and near-perfect THz absorptions were also observed over wide incident angles in these meta-absorbers, where the electric field and power loss were mainly concentrated in the additional thin dielectric layer. Such a broadband THz absorption was achieved through electromagnetic coupling between the top and middle metal layers and the resultant overlapping of the resonance frequencies. This strategy can be adapted to other spectrum-shaping devices.

Tadesse A.D., Acharya O.P., Sahu S.

Yuan Y., Dong C., Gu J., Liu Q., Xu J., Zhou C., Song G., Chen W., Yao L., Zhang D.

Sophisticated metastructures are usually required to broaden the inherently narrowband plasmonic absorption of light for applications such as solar desalination, photodetection, and thermoelectrics. Here, nonresonant nickel nanoparticles (diameters < 20 nm) are embedded into cellulose microfibers via a nanoconfinement effect, producing an intrinsically broadband metamaterial with 97.1% solar-weighted absorption. Interband transitions rather than plasmonic resonance dominate the optical absorption throughout the solar spectrum due to a high density of electronic states near the Fermi level of nickel. Field solar purification of sewage and seawater based on the metamaterial demonstrates high solar-to-water efficiencies of 47.9-65.8%. More importantly, the solution-processed metamaterial is mass-producible (1.8 × 0.3 m2 ), low-cost, flexible, and durable (even effective after 7 h boiling in water), which are critical to the commercialization of portable solar-desalination and domestic-water-purification devices. This work also broadens material choices beyond plasmonic metals for the light absorption in photothermal and photocatalytic applications.

Ou H., Lu F., Liao Y., Zhu F., Lin Y.

We present two types of tunable terahertz (THz) metamaterials (TTM-1 and TTM-2) to explore their extraordinary optical properties. The proposed TTMs are composed of Au layers with 300 nm in thickness on Si substrates. The designs of TTMs exhibit superior properties in adjustability for high-efficiency THz switching characteristic. By changing the geometrical dimensions of TTMs, the corresponding electromagnetic responses could be tuned and switched between single-band and dual-band resonances. TTM-1 exhibits three switching windows with higher switching ratios by embedding different materials into the cavity underneath the complementary metamaterial. TTM-2 can be tuned to have two resonances and then merge into one resonance by increasing the height between the inner and outer rings. The transmission intensity of TTM-2 can be tuned from 0 to 0.7 at 0.57 THz by changing the sizes of inner and outer rings. TTM-2 exhibits tunable filter, single-/dual-band switch, tunable free spectrum range, and tunable bandwidth characteristics by varying the radius of the inner and outer rings. This study paves a way to the possibility of tunable high-efficiency switch, filter, polarizer, and other THz applications.

Anwar S., Ali G., Khan M., Bozorgzadeh F.

Bigbaghlou R.G., Salahandish M., Nasiri H., Hashemzadeh E., Pourziad A.

Dasi S., Manmadha Rao G.

A graphene metamaterial-based absorber that can be tuned to three distinct frequencies and is not affected by any polarization angle has been proposed for THz applications. The design of the polarization-insensitive metamaterial absorber includes two split ring resonators and a circular slot with minus shaped strip on the graphene material. Simulation findings using the finite element method demonstrate that the developed absorber has absorption efficiencies greater than 90%. Graphene’s surface plasmon resonances confine the field, resulting in three ideal narrow absorption peaks at 7.07, 7.57, and 9.49 THz with efficiencies of 91.08%, 99.15%, and 99.85%, respectively. Moreover, it has been shown that the absorber’s performance can be enhanced and the resonance frequencies shifted by altering the chemical potential of the graphene sheet. The suggested THz absorber’s response is the same for both transverse (TE) and transverse (TM) polarizations, and it is also angularly stable (up to 90 degrees).

Kumar R., Gupta R., Mishra A.K., Singh N., Pandey P.C., Singh B.K.

We have theoretically investigated the engineering of a highly efficient metamaterial (MTM) absorber with nanocircular ring resonators of nickel (Ni) metal for the absorption of visible to far-infrared (400 nm to 4000 nm). A metal–insulator-metal structure is used in the design of the proposed MTM absorber. We have observed the high absorption values with varying top resonator designs Ni-metal compared to other considered metals. The proposed absorber exhibits an average absorption of 95.34% for transverse electric (TE) and transverse magnetic (TM) modes for wavelengths 400 nm to 4000 nm. The CST simulation software analyzes the absorber’s properties for different structural parameters. The average absorption is attained over 90% at different incidence angles and independent of polarization angles. Moreover, we have investigated the absorption performance using various structural characteristics. Short-circuit current densities (Jsc) are investigated using a global air mass of 1.5 (AM1.5) solar spectrum at various incidence angles. The proposed absorber containing Ni metal nanoresonators is designed as an alternative for thermal, emission, photovoltaic, and energy harvesting applications due to its attractive functionality, including geometry, cost, polarization insensitivity, large bandwidth, and thermal robustness.

Zhang L., Kong X., Chen L., Zhang W., Lin X., Wang C., Jiang Y., Li J., Qu F.

Tang Y., Liu W., Cheng Y., Pan P., Liu X., Liu Z., Liu G.

Tan L., Wang D., Xu K.

Metamaterials, an artificial electromagnetic (EM) material, have exhibited unique characteristics, enabling innovations in terahertz (THz) wavefront shaping, polarization modulation, surface wave manipulation, and spectrum modulation. In this review, we focus on the advancements in THz metamaterials for spectrum modulation, emphasizing their structural design, special materials, and applications. The review discusses various structural designs, including metal-dielectric composite structures, all-metal structures, and all-dielectric structures, each offering distinct advantages for THz applications. Key special materials such as graphene, vanadium dioxide (VO2), molybdenum disulfide (MoS2), and flexible materials are highlighted for their significant contributions to enhancing the performance and functionality of THz metamaterials. The applications of THz metamaterials in EM stealth and sensing are thoroughly introduced, with a particular focus on biosensing, pesticide detection, and other sensing applications. The review emphasizes the potential of THz metamaterials in developing highly sensitive and selective sensors, as well as efficient THz absorbers and filters. Future perspectives include the continuous development of novel materials, advanced fabrication technologies, and the integration of multifunctional capabilities to further expand the applications and efficiency of THz metamaterials. These advancements are expected to drive significant progress in THz technology, impacting fields such as medical diagnostics, environmental monitoring, food safety, wireless communication, and security.

Qin X., Fang S., Duan G., Xu C., Jiang J., Xiong H., Wang B.

An integrated terahertz metamaterial absorber, based on thermal and electrical dual-modulation strategies, with two different and tunable absorption functions is demonstrated.

Zhang Y., Jia K., Ge H., Ji X., Jiang Y., Bu Y., Zhang Y., Sun Q.

A terahertz metamaterial microfluidic sensing chip for ultrasensitive detection is proposed to investigate the response of substances to terahertz radiation in liquid environments and enhance the molecular fingerprinting of trace substances. The structure consists of a cover layer, a metal microstructure, a microfluidic channel, a metal reflective layer, and a buffer layer from top to bottom, respectively. The simulation results show that there are three obvious resonance absorption peaks in the range of 1.5–3.0 THz and the absorption intensities are all above 90%. Among them, the absorption intensity at M1 = 1.971 THz is 99.99%, which is close to the perfect absorption, and its refractive index sensitivity and Q-factor are 859 GHz/RIU and 23, respectively, showing excellent sensing characteristics. In addition, impedance matching and equivalent circuit theory are introduced in this paper to further analyze the physical mechanism of the sensor. Finally, we perform numerical simulations using refractive index data of normal and cancer cells, and the results show that the sensor can distinguish different types of cells well. The chip can reduce the sample pretreatment time as well as enhance the interaction between terahertz waves and matter, which can be used for early disease screening and food quality and safety detection in the future.

Karim A.S.

In this work, a design for a broadband multi-resonator metamaterial absorber (MTMA) for satellite communications is proposed. This design is based on both numerical and experimental data. Four resonators were used to achieve a broad absorption of more than 99% in the frequency range of 12–16 GHz. The electromagnetic properties (absorption, reflection and transmittance) of the MTMA were analysed and extracted. The parametric effects including the type of substrate, its thickness and the change of the resonator width on the absorption spectrum were studied. Also, surface currents, electric field and magnetic field distributions were investigated and presented at 12.75 GHz. Besides, the proposed design was fabricated by using the LPKFan ProtoMat E33 machine and tested by waveguide connected to a vector network analyzer. It was found that there is a good agreement between the simulation and experimental results. The proposed design can be used for different applications, especially for the application of satellite communications.

Choi J., Lim D., Lim S.

In stealth applications, there is a growing emphasis on the development of radar-absorbing structures that are efficient, flexible, and optically transparent. This study proposes a screen-printed metamaterial absorber (MMA) on polyethylene terephthalate (PET) substrates using indium tin oxide (ITO) as the grounding layer, which achieves both optical transparency and flexibility. These materials and methods enhance the overall flexibility and transparency of MMA. To address the limited transparency caused by the silver nanoparticle ink for the top pattern, a metal mesh was incorporated to reduce the area ratio of the printed patterns, thereby enhancing transparency. By incrementing the fractal order of the structure, we optimized the operating frequency to target the X-band, which is most commonly used in radar detection. The proposed MMA demonstrates remarkable performance, with a measured absorption of 91.99% at 8.85 GHz and an average optical transmittance of 46.70% across the visible light spectrum (450 to 700 nm), indicating its potential for applications in transparent windows or drone stealth.

Sharma P., Ako R.T., Wang Q., Atakaramians S., Walia S., Sriram S.

Abstract Frequency selective surfaces (FSSs) are widely employed in spectrometers, selective absorbers, energy harvesting, and sensing devices. However, in the terahertz range, the performance of this ideal component is frequently constrained by the choice of material, which introduces a certain degree of attenuation, thereby diminishing the signal-to-noise ratio. Moreover, these FSS are often bulky and demonstrate a low extinction ratio, which limits their usage in wearables and miniaturised devices. In this work, a multi-band FSS composed of periodic microstructures on an ultrathin cyclic olefin copolymer sheet is proposed, analysed, fabricated, and evaluated using terahertz-time domain spectroscopy. The unit cell is composed of triple, evenly spaced, horizontal gold strips, linked around the middle by a fourth vertically oriented gold strip. By displacing the vertical strip, the asymmetric metasurface shows dual narrowband transmission at 1.04 THz and 1.67 THz. However, only a single narrowband transmission at 1.07 THz can be observed on a symmetric metasurface, with no displacement. The calculated Q factors are 4.52 and 16.63 at 1.04 THz and 1.67 THz, respectively, for the asymmetric metasurface. While for the symmetric metasurface, the calculated Q factor at 1.07 THz is 3.63. The proposed flexible metasurface can be tailored easily as single or dual narrowband frequency selective metasurface for channel filtering and broadband sources in emerging terahertz wireless systems.

Jiang Y., Fu J., Li B., Jiang P.

Current research on the interference of GNSS (Global Navigation Satellite System) array antennas focuses on the single interference effect and the improvement of interference hardware capability, while the multi-degree-of-freedom (DOF) interference model and mechanism remain to be fully studied. Aiming at this problem, this paper analyzes the preconditions for the definition of anti-jamming degrees of freedom and the characteristics of super-DOF interference through formula derivation and simulation. First, by analyzing the influence of the number of interfering signals on the angular resolution, the prerequisite of the definition of anti-interference degrees of freedom in the airspace is proposed. Second, the definition of anti-interference degrees of freedom is used to calculate the change rule of the critical power of the interference under different numbers of interfering signals. Finally, the influence of super-DOF interference on the array antenna is analyzed. The results show that the prerequisite for the anti-interference freedom of the array antenna is that the distribution interval of the interfering signal is greater than 15°, taking a four-array element uniform circular array antenna as an example. The critical interference power of the array antenna decreases by about 15 dB when the number of interfering signals exceeds the degrees of freedom of the array antenna’s interference immunity, provided that the interference resolution is satisfied. The conclusions of this paper give the critical power change rule of multi-DOF interference and the effect of super-DOF interference, as well as the prerequisites for the setting of interference signals, which can be used, for example, in the deployment of distributed interference sources and the development of anti-jamming algorithms.

Bhati R., Malik A.K.

AbstractWe report a multi-resonant terahertz (THz) metamaterial perfect absorber (MPA)-based biosensor in the working frequency range of $$0 - 3.8 THz$$ 0 - 3.8 T H z for sensing of microorganisms (such as fungi, yeast) and wheat pesticides. Nearly $$100\%$$ 100 % absorption is realized at $$f_1= 1.7THz, f_2= 2.8THz, f_3=3.2THz,$$ f 1 = 1.7 T H z , f 2 = 2.8 T H z , f 3 = 3.2 T H z , and $$f_4=3.5THz$$ f 4 = 3.5 T H z . We designed our THz MPA sensor making resonators’ gap area compatible with the microorganisms’ size. To obtain optimum performance of the MPA, a mapping of amplitudes and shifts in the absorption resonance peaks with different structural parameters of the resonators is carried out. A very high-frequency shift is obtained for microorganisms such as Penicillium chrysogenum (fungi), yeast, and pesticides (Imidacloprid, N, N-Diethyldithiocarbamate sodium salt trihydrate, Daminozide, N, N-Diethyldithiocarbamate sodium salt hydrate, and Dicofol). An equivalent circuit model using Advance Design System (ADS) software is developed. The calculated results through the model show similar trends as obtained in the simulations using CST. Investigations of the effect of incidence angle of THz wave on the absorption spectra of the MPA are also carried out. It is found that incidence angle does not impact the stability of the lower resonance absorption peak (1.79THz). Due to the wide working frequency range, the proposed sensor is extremely suitable for the detection of all range of pesticides because their specific absorption fingerprint lies in the frequency range of 0–3.8THz. We believe that our sensor could be a potential detection tool for detecting pesticide residues in agriculture and food products. The THz MPA-based biosensor is capable of detecting a very small change in the effective dielectric constant of the MPA environment. Therefore, it can also offer huge opportunities in label-free biosensing for future biomedical applications.

He Z., Qiu L., Zhang P., Liu Y., Huang S., Deng L.