A Pathway to Subwavelength Imaging Using a Metamaterial Superlens

Abstract

Recent theoretical works have suggested the possibility of constructing a diffraction-free lens by using a negative refractive index medium (NRIM). The key theoretical proposition is that evanescent waves can be greatly enhanced by increasing the thickness of the NRIM. We present here experimental evidence on enhanced transmission of evanescent waves via surface plasmon at a thin silver film operating near surface plasma resonant frequency. We found the transmission of evanescent waves rapidly grows with the film thickness up to about 50 nm, after which it decays as loss becomes significant. These experiments also demonstrated the broadening of enhanced transmission spectrum as photon energy approaches plasma resonance εAg= -1 condition. These findings represent the first step toward the understanding and realization of a diffraction-free lens by using NRIM.