Articles written in Pramana – Journal of Physics

    • Terahertz broadband metamaterial absorber enabled by SiO$_{2}$, polyimide and PET dielectric substrates


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      A broadband polarisation-insensitive terahertz (THz) metamaterial absorber (MMA) is presented in this paper. The MMA consists of a simple planar structure as a unit cell and an optically transparent indium tin oxide (ITO) ground plane, both are separated by a 50 $\mu$m dielectric substrate. We designed three combinations of MMA here, which are ITO–polyimide–ITO, ITO–polyethylene terephthalate (PET)–ITO and ITO–silicon dioxide (SiO$_{2}$)–ITO for the same planar structure. By changing the substrate of the structure, the resonant frequency and bandwidth of the absorber structure can be varied. The numerical simulation of the absorber shows that the absorptivity is $>$ 96% for all three substrates. Polyimide, PET and SiO$_{2}$ based absorbers demonstrated the bandwidth of 0.558 THz,0.603 THz and 0.658 THz with covered broadband frequency range of 0.4254–0.9829 THz, 0.457–1.16 THz and 0.511–1.169 THz respectively. ITO–PET–ITO absorber structure produced optical transparency. These bandwidths are compatible and convenient for electronic sources in the terahertz region. This study also provides applications in THz sensing and imaging, communication and detection systems.

    • Terahertz single dual multi-band metamaterial absorber


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      In this study, a new multifunctional terahertz (THz) metamaterial absorber (MMA) has been presented which is controlled by the thickness of the substrate used. The proposed structure consists of copper as the ground plane and polyimide dielectric layer is placed in between the ground panel and the top radiating patch. The resonant frequency and number of resonating modes of the proposed absorber can be changed by varying the thickness of thesubstrate from 10 to 100 μm for the same planar structure. Depending on the thickness of the substrate, this MMA gives a narrow (10 μm), double (20 μm), triple (30 μm), quad (50 μm) and hexa (100 μm) number of resonating modes. In order to analyse the physical mechanism of the proposed absorber, we took 10, 20 and 30 μm-based MMA and their electric and magnetic fielddistributions are demonstrated. We compared the resonant frequency ranges and the number of bands with the previously reported papers. The polarisation and angle insensitivity of the design have been validated by numerical simulation up to 90$^◦$ of oblique incidence. The effects of variationin geometrical parameters and sensing habits have been studied in the narrow band (10 μm) MMA structure. The designed multifunctional absorber has the advantage of using the same MMA to produce multiple (narrow, double,triple, quad and hexa) band absorbers.

    • Design, fabrication and characterization of terahertz five-band metamaterial absorber


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      This research presents the simulation, fabrication, and measurement of a new terahertz (THz) metamaterial absorber (MMA). Copper and polyimide are the materials used in this project. The polyimide substrate is sandwiched between the two copper conductor layers. Theoretical results reveal that the absorber has five distinct and significant absorption peaks at 0.994, 0.97, 0.947, 0.904 and 0.892 THz, respectively, with absorption rates of 94%, 99.9%, 99.9%, 97%, and 92%. The electric field, magnetic field, and surface current distributions are used to investigate the structure’s physical mechanism. The incident and polarisation angles of the structure are modified from 0 to 90 degrees to examine the insensitive behaviour of the incident angle and polarisation angle. Laser micromachining and terahertz time-domain spectroscopy are used to build and examine the structure. This work is compared with previous works. It has numerous scientific and sensory applications.

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