▎ 摘　　要

A super-resolution (with lambda/50 resolution ability at mid-infrared region) device that consists of a monolayer graphene sandwiched between two dielectric materials with two alternate chemical potentials in graphene (which can be obtained by alternately applying two biased voltages to graphene) is proposed and analyzed. When the subwavelength resolution is achieved, the graphene-based device can be viewed as an effective optical medium with alternate arrangement of positive and negative refractive indices. And the isofrequency dispersion curves of the effective optical medium have the hyperbolic form. Furthermore, the super-resolution at different desired frequencies can be reached by merely changing the chemical potentials of graphene. The proposed devices have potential applications in multi-functional material, real-time subwavelength imaging, and high-density optoelectronic components for using the abnormal diffraction feature. (C) 2014 Optical Society of America