Terahertz super-resolution imaging using four-wave mixing in graphene

A perfect lens made from negative refraction (NR) materials is utilized to overcome the diffraction limit. However, these NR lenses are realized by metamaterials, which suffer from high losses, and the volume is bulky. In this Letter, we propose a terahertz NR lens by using a four-wave mixing (FWM) process in graphene. NR is demonstrated because of the phase matching along the surface of graphene. Evanescent waves that store high spatial frequency information can be converted into propagating waves in the nonlinear NR process. An image with subwavelength resolution is reconstructed at the FWM wavelength. Theoretical analysis and numerical simulations are performed to demonstrate the capability of such imaging. The lens has a subwavelength resolution of around lambda/5. The lens needs low field intensity due to the strong nonlinear response of graphene in the terahertz frequency. This Letter may have applications in terahertz microscopy. (C) 2018 Optical Society of America