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Grande M.,Polytechnic of Bari | Vincenti M.A.,National Research Council Italy | Stomeo T.,Italian Institute of Technology | De Ceglia D.,National Research Council Italy | And 6 more authors.
IEEE Photonics Journal

We investigate the linear response of single and multiple graphene sheets embedded in quarter-wave one-dimensional photonic crystals (PhCs) in terms of absorption and losses. In particular, we show that it is possible to achieve near-perfect narrowband absorption when a single monolayer graphene is sandwiched between two PhC mirrors with optimized pair numbers. The simulations reveal that the resonant wavelength and the total absorption frequency may be tuned by tilting the angle of incidence of the impinging source. We also show that the losses, related to the dielectric materials constituting the one-dimensional PhC, can degrade the optical performance of the device. Conversely, by arranging the same dielectric slabs in a different order (supercell), it is possible to achieve a broadband absorption that is almost constant over a wide range of angle of incidence. In this configuration, the absorption and the bandwidth can be tuned by varying the supercell geometry. These features make these devices attractive for different applications ranging from tunable and saturable absorbers for short-pulse lasers to graphene-based photodetectors. © 2009-2012 IEEE. Source

Garbugli M.,Polytechnic of Milan | Porro M.,Italian Institute of Technology | Porro M.,Polytechnic of Milan | Roiati V.,Polytechnic of Milan | And 9 more authors.

We propose a new approach for converting light energy into electrical energy, based on the photogeneration of nano-dipoles at donor-acceptor interfaces. The nano-dipoles are oriented in space so as to contribute to a collective polarization that induces a potential difference across the material, sandwiched between electrodes. A current is detected in the external circuit upon illumination. Such a device would exploit many advantages of organic semiconductors and get rid of the main limitation, namely transport. We provide a proof of concept and we discuss the ideal limit of the device based on numerical simulations. This provides design guidelines to the achievement of best performances. Simulations show that the proposed device can be an appealing opportunity with giant conversion efficiency provided some technological issues are overcome. © The Royal Society of Chemistry 2012. Source

Todaro M.T.,National Nanotechnology Laboratory NNL | Sileo L.,National Nanotechnology Laboratory NNL | Epifani G.,National Nanotechnology Laboratory NNL | Tasco V.,National Nanotechnology Laboratory NNL | And 3 more authors.
Journal of Micromechanics and Microengineering

In this work, we demonstrate a fully integrated three-axis Hall magnetic sensor by exploiting microfabrication technologies applied to a GaAs-based heterostructure. This allows us to obtain, by the same process, three mutually orthogonal sensors: an in-plane Hall sensor and two out-of-plane Hall sensors. The micromachined devices consist of a two-dimensional electron gas AlGaAs/InGaAs/GaAs multilayer which represents the sensing structure, grown on the top of an InGaAs/GaAs strained bilayer. After the release from, the substrate, the strained bilayer acts as a hinge for the multilayered structure allowing the out-of-plane self-positioning of devices. Both the in-plane and out-of-plane Hall sensors show a linear response versus the magnetic field with a sensitivity for current-biased devices higher than 1000 V A-1 T-1, corresponding to an absolute sensitivity more than 0.05 V T -1 at 50 μA. Moreover, Hall voltage measurements, as a function of the mechanical angle for both in-plane and out-of-plane sensors, demonstrate the potential of such a device for measurements of the three vector components of a magnetic field. © 2010 IOP Publishing Ltd. Source

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