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    Broad-band conical-shaped perfect absorber metamaterial for solar cells
    (Elsevier, 2023) Durmaz, Habibe; Li, Yuyu; Eksiog, Yasa
    In this paper, we present a design, simulation, and measurement of a single broad-band metamaterial absorber composed of a consecutive layer of conical-shaped SiO2/Al/SiO2/Al. The circular symmetry of the conical-shaped resonator makes the metamaterial absorber polarization insensitive so that the full intensity of the sunlight can be harvested. The physical behavior of the broad-band mechanism is investigated both numerically by finite difference time domain (FDTD) and experimentally. The numerical calculations indicate the origin of broadband absorption is due to the couplings between the two metal layers sandwiched in between two dielectric SiO2 layers. The effect of geometrical parameters and the layer thicknesses are studied numerically and experimen-tally. The experimental results show the average absorption strength of the metamaterial absorber is around 80% within the spectral range of 400-1000 nm. The experimental and simulation spectra are well-consistent. The proposed platform has potential use in many potential applications, such as solar cells, photodetectors, cameras, etc.
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    A multiple-band perfect absorber for Seira applications
    (Elsevier Science Sa, 2018) Durmaz, Habibe; Li, Yuyu; Çetin, Arif E.
    Recently perfect absorbers (PAs) have received significant interest due to their characteristics of complex electric permittivity (epsilon) and magnetic permeability (mu). By rationally designing these artificial structures, the impedance of the perfect absorber can be matched to free space with an independent adjustment in the electric and magnetic resonances, where this structure leads to strong absorption from mid- to near-IR wavelength. In this article, we proposed a multiband PA platform, which simultaneously operates with a near unity absorption at different resonances that could be an ideal candidate for multiple sensing of molecular fingerprints. We numerically analyzed the dependence of the optical response of the PA platform through finite-difference time domain (FDTD) simulations for a fine-tuning mechanism of the PA platform. We theoretically demonstrated the surface enhanced infrared absorption (SEIRA) capability of our PA platform by studying its optical response with a thin protein bilayer and a polymethyl-methacrylate (PMMA) film. As an initial step we experimentally showed the vibrational modes of a thin PMMA film. We believe, our findings could open new avenues for reliable SERIA platforms through providing multiple vibrational finger print information compared to its conventional counterparts relying only on a single sensing data.
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    A polarization insensitive wide-band perfect absorber
    (Wıley-V C H Verlag Gmbh, 2019) Durmaz, Habibe; Çetin, Arif E.; Li, Yuyu; Paiella, Roberto
    In this article, a wide-band and polarization-insensitive perfect absorber composed of 4 sandwiched layers of dielectric and metal disks is introduced. Compared to classical perfect absorbers, the system supports near-unity absorption within a wider spectral window through multiple perfect absorption mechanisms that exist due to a constituting inter-metal disk, functioning either as a dipolar antenna or a conducting ground for different perfect absorption mechanisms. Circular shape of the antenna makes the working mechanism of the system polarization insensitive. The working principle of the system is investigated through near- and far-field calculations by finite difference time domain (FDTD) simulations. A fine-tuning mechanism of the wide-range perfect absorption window is introduced through geometrical device parameters. The multilayer perfect absorber system is fabricated through a high-quality fabrication method based on electron beam lithography, lift-off method, and multi-step deposition of metal and dielectric layers. The spectral behavior of the perfect absorber system is finally experimentally investigated through Fourier transform infrared (FTIR) spectroscopy.