ACS Nano 7, 4810–4817 (2013)

Graphene, a truly two-dimensional gapless semiconductor, has been recognized as a revolutionary material for optoelectronic applications. Several uses of graphene have been proposed in various devices, such as transparent electrodes, ultrafast lasers, polarizers and photodetectors. The low absolute value of the absorption of graphene (2.3% of the incident light is absorbed in a graphene layer) limits the photocurrent efficiencies of graphene-based photodetectors. Therefore, one of the challenges is to enhance its optical absorption. Now, Luis Martín Moreno, Jaime Gómez Rivas and colleagues experimentally demonstrate a broadband enhancement of the light absorption in graphene over the whole visible spectrum. This enhanced absorption is obtained in a multilayer structure by using an attenuated total reflectance configuration and is explained in terms of coherent absorption arising from interference and dissipation. The interference mechanism leading to the phenomenon of coherent absorption can be precisely controlled by varying the refractive index and/or thickness of the medium surrounding the graphene.