23 September 2016 Tuning Fano resonances of graphene-based gratings
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We present a strategy to control Fano resonances in hybrid graphene-silicon-on-insulator gratings. The presence of a mono- or few-layer graphene film allows to electrically and/or chemically tuning the Fano resonances that result from the interaction of narrow-band, quasi-normal modes and broad-band, Fabry-Perot-like modes. Transmission, reflection and absorption spectra undergo significant modulations under the application of a static voltage to the graphene film. In particular, for low values of the graphene chemical potential, the structure exhibits a symmetric Lorentzian resonance; when the chemical potential increases beyond a specific threshold, the grating resonance becomes Fano-like, hence narrower and asymmetric. This transition occurs when the graphene optical response changes from that of a lossy dielectric medium into that of a low-loss metal. Further increasing the chemical potential allows to blue-shift the Fano resonance, leaving its shape and linewidth virtually unaltered. We provide a thorough description of the underlying physics by resorting to the quasi-normal mode description of the resonant grating and retrieve perturbative expressions for the characteristic wavelength and linewidth of the resonance. The roles of number of graphene layers, waveguide-film thickness and graphene quality on the tuning abilities of the grating will be discussed. Although developed for infrared telecom wavelengths and silicon-on-insulator technology, the proposed structure can be easily designed for other wavelengths, including visible, far-infrared and terahertz, and other photonic platforms.
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Domenico de Ceglia, Domenico de Ceglia, Maria A. Vincenti, Maria A. Vincenti, Marco Grande, Marco Grande, Giuseppe Valerio Bianco, Giuseppe Valerio Bianco, Giovanni Bruno, Giovanni Bruno, Antonella D'Orazio, Antonella D'Orazio, Michael Scalora, Michael Scalora, "Tuning Fano resonances of graphene-based gratings", Proc. SPIE 9921, Plasmonics: Design, Materials, Fabrication, Characterization, and Applications XIV, 99212Y (23 September 2016); doi: 10.1117/12.2237960; https://doi.org/10.1117/12.2237960

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