Browsing by Author "Tzortzakis, S."

Now showing 1 - 3 of 3

Open Access
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
Open Access
In-volume laser direct writing of silicon—challenges and opportunities
(Wiley-VCH Verlag GmbH & Co. KGaA, 2021-11) Chambonneau, M.; Grojo, D; Onur, Tokel; İlday, Fatih Ömer; Tzortzakis, S.; Nolte, S.
Laser direct writing is a widely employed technique for 3D, contactless, and fast functionalization of dielectrics. Its success mainly originates from the utilization of ultrashort laser pulses, offering an incomparable degree of control on the produced material modifications. However, challenges remain for devising an equivalent technique in crystalline silicon which is the backbone material of the semiconductor industry. The physical mechanisms inhibiting sufficient energy deposition inside silicon with femtosecond laser pulses are reviewed in this article as well as the strategies established so far for bypassing these limitations. These solutions consisting of employing longer pulses (in the picosecond and nanosecond regime), femtosecond-pulse trains, and surface-seeded bulk modifications have allowed addressing numerous applications.
Open Access
Optically implemented broadband blueshift switch in the terahertz regime
(American Physical Society, 2011-01-18) Shen, N. H.; Massaouti, M.; Gokkavas, M.; Manceau J. M.; Özbay, Ekmel; Kafesaki, M.; Koschny, T.; Tzortzakis, S.; Soukoulis, C. M.
We experimentally demonstrate, for the first time, an optically implemented blueshift tunable metamaterial in the terahertz (THz) regime. The design implies two potential resonance states, and the photoconductive semiconductor (silicon) settled in the critical region plays the role of intermediary for switching the resonator from mode 1 to mode 2. The observed tuning range of the fabricated device is as high as 26% (from 0.76 THz to 0.96 THz) through optical control to silicon. The realization of broadband blueshift tunable metamaterial offers opportunities for achieving switchable metamaterials with simultaneous redshift and blueshift tunability and cascade tunable devices. Our experimental approach is compatible with semiconductor technologies and can be used for other applications in the THz regime.