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Graphene2017 March 28-31, 2017 Barcelona (Spain) Optically Transparent Microwave Absorbers Based on Engineered Graphene Marco Grande 1 G. V. Bianco 2 , M. A. Vincenti 3 , D. de Ceglia 3 , V. Petruzzelli 1 , P. Capezzuto 2 , M. Scalora 4 , G. Bruno 2 , A. D’Orazio 1 1 Dipartimento di Ingegneria Elettrica e dell’Informazione, Politecnico di Bari, Via Re David 200, 70125 - Bari, Italy. 2 Istituto di Nanotecnologia – CNR-NANOTEC, Via Orabona, 4, 70125 - Bari, Italy. 3 National Research Council, Charles M. Bowden Research Center, RDECOM, Redstone Arsenal, Alabama 35898-5000 – USA. 4 Charles M. Bowden Research Center, RDECOM, Redstone Arsenal, Alabama 35898- 5000 – USA. [email protected] We propose an innovative approach for the realization of a microwave absorber fully transparent in the optical regime [1-2]. This device is based on the Salisbury screen configuration, which consists of a lossless spacer (glass) sandwiched between two graphene sheets whose sheet resistances are different and properly engineered (Fig. 1(a)). Experimental results show that it is possible to achieve near-perfect electromagnetic absorption in the microwave X-band (Fig. 1(b)). Engineering and integration of graphene sheets could facilitate the realization of innovative microwave absorbers with additional electromagnetic and optical functionalities. These, in turn, could circumvent some of the major limitations of opaque microwave absorbers exploited in military camouflage and shielding systems as well as successfully integrated in window glass and along with photovoltaics. These findings are also extremely important for micro- and nano- satellite applications where the maximization of the surface area for the solar power collection remains a critical issue. References [1] M. Grande, G. V. Bianco et al., Scientific Reports, 5 (2015) 17083. [2] M. Grande, G. V. Bianco et al., Optics Express, 24 (2016) 22788-22795. Figures Figure 1: (a) Picture of the realized optically transparent graphene-based absorber. (b) Comparison between experimental (dots) and analytical findings (solid lines), in terms of microwave reflectance (blue line), transmittance (red line) and absorption (green line), when the spacer thickness is varied. The measurements are carried out with an operating frequency equal to 9 GHz (in the X band). (c) Normalized optical transmittance of the absorbing layer (bi-layer graphene), mirror (doped four-layer graphene) and the complete absorber, respectively.
