Browsing by Subject "Nanocavities"

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    Fano resonances in THz metamaterials composed of continuous metallic wires and split ring resonators
    (Optical Society of America, 2014) Li, Z.; Cakmakyapan, S.; Butun, B.; Daskalaki, C.; Tzortzakis, S.; Yang, X.; Özbay, Ekmel
    We demonstrate theoretically and experimentally that Fano resonances can be obtained in terahertz metamaterials that are composed of periodic continuous metallic wires dressed with periodic split ring resonators. An asymmetric Fano lineshape has been found in a narrow frequency range of the transmission curve. By using a transmission line combined with lumped element model, we are able to not only fit the transmission spectra of Fano resonance which is attributed to the coupling and interference between the transmission continuum of continuous metallic wires and the bright resonant mode of split ring resonators, but also reveal the capacitance change of the split ring resonators induced frequency shift of the Fano resonance. Therefore, the proposed theoretical model shows more capabilities than conventional coupled oscillator model in the design of Fano structures. The effective parameters of group refractive index of the Fano structure are retrieved, and a large group index more than 800 is obtained at the Fano resonance, which could be used for slow light devices. (C) 2014 Optical Society of America
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    Lithography-free planar band-pass reflective color filter using a series connection of cavities
    (Nature Publishing Group, 2019-01) Ghobadi, Amir; Hajian, Hodjat; Soydan, Mahmut Can; Bütün, Bayram; Özbay, Ekmel
    In this article, a lithography-free multilayer based color flter is realized using a proper series connection of two cavities that shows relatively high efciency, high color purity, and a wide view angle. The proposed structure is a metal-insulator-metal-insulator-semiconductor (MIMIS) design. To optimize the device performance, at the frst step, transfer matrix method (TMM) modeling is utilized to fnd the right choices of materials for each layer. Simulations are carried out later on to optimize the geometries of the layers to obtain our desired colors. Finally, the optimized devices are fabricated and experimentally characterized to evaluate our modelling fndings. The characterization results of the fabricated samples prove the successful formation of efcient and wide view angle color flters. Unlike previously reported FP based designs that act as a band-stop flter in refection mode (absorbing a narrow frequency range and refecting the rest of the spectrum), this design generates a specifc color by refecting a narrow spectral range and absorbing the rest of the spectrum. The fndings of this work can be extended to other multilayer structures where an efcient connection of cavities in a tandem scheme can propose functionalities that cannot be realized with conventional FP resonators.