▎ 摘　　要

Considering the dielectric permittivity of graphene can be tuned to be negative by external electric field, we propose to construct alternating graphene/dielectric multilayer based optical hyperlens for far-field subdiffraction imaging at mid-infrared frequencies. For such a scheme, hyperbolic dispersion curve can be achieved under the condition that the thickness of dielectric layer is made comparable to that of graphene layer, which is capable of supporting the propagation of evanescent wave with large wave vector. Simulation results by finite-element method demonstrate that two point sources with separation far below the diffraction limit can be magnified by the systems to the extent that conventional far-field optical microscopy can further manipulate. Such a hyperlens has the advantage of operating in a wideband region due to the tunability of graphene's dielectric permittivity as opposed to previous metal based hyperlens, enabling the potential applications in real-time super-resolution imaging, nanolithography, and sensing. (C) 2013 Optical Society of America