Graphene optical-to-thermal converter

Abstract : Infrared plasmons in doped graphene nanostructures produce large optical absorption that can be used for narrow-band thermal light emission at tunable frequencies that strongly depend on the doping charge. By virtue of Kirchhoff's law, thermal light emission is proportional to the absorption , thus resulting in narrow emission lines associated with the electrically controlled plasmons of heated graphene. Here, we show that realistic designs of graphene plasmonic structures can release over 90% of the emission through individual infrared lines with 1% bandwidth. We examine aniso-tropic graphene structures in which efficient heating can be produced upon optical pumping tuned to a plasmonic absorption resonance situated in the blue region relative to the thermal emission. An incoherent thermal light converter is thus achieved. Our results open a radically different approach for designing tunable nanoscale infrared light sources. V C 2014 AIP Publishing LLC. [] The fabrication of intense, tunable infrared sources remains a challenge, despite the availability of quantum-cascade laser, 1 free-electron lasers, 2 and thermal emission bulbs. In particular, thermal emission has been extensively studied, leading to advances such as the control over its angular distribution from heated gratings 3 and fundamental insights on the coherence properties of the associated electromagnetic field near the emitting surfaces. 4 Additionally, thermal emission has been shown, in combination with resonant metamaterial designs, to be confined within infrared peaks of high quality factor –the ratio of the energy width to the central energy of a peak– Q $ 5, which can be tuned by modifying the geometry. 5 Alternatively, fast electro-optical modulation can be achieved through the use of doped graphene, which has been demonstrated to display plasmons that are frequency-controlled via electrostatic gating, 6–11 reaching Q > 50. 10 By conveniently shaping the graphene, it is possible to reach plasmon-mediated complete optical absorption over large areas. 12 Conversely, by virtue of Kirchhoff's law, black-body light emission occurs in heated graphene at frequencies corresponding to the full-absorption resonances. Recently, conversion of broadband light to quasi-monochromatic emission has been achieved, 13 while electrical modulation of the resulting emission has been successfully demonstrated. 14 Electrical modulation of the emissivity has been also predicted using quantum wells 29 and recently demonstrated at 600 kHz. 20
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Article dans une revue
Applied Physics Letters, American Institute of Physics, 2014, 105 (21), pp.211102. 〈10.1063/1.4902429〉
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Alejandro Manjavacas, Sukosin Thongrattanasiri, Jean-Jacques Greffet, F.G. Garcia de Abajo. Graphene optical-to-thermal converter. Applied Physics Letters, American Institute of Physics, 2014, 105 (21), pp.211102. 〈10.1063/1.4902429〉. 〈hal-01335131〉



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