Study of active superlens and evanescent wave amplification using an active metamaterial model

Abstract

We propose a Π -shaped circuit model for active metamaterials using periodic circuit structures with series inductors and shunt capacitors (LC) and series capacitors and shunt inductors (CL). Using the circuit model, we develop a general theory for active metamaterials, revealing the role of active components and demonstrating the principle for metamaterials to be active. By inserting negative and positive resistances in the LC and CL structures, we first attain the active superlens using three slabs of effective media made by such metamaterial circuit structures and show that the amplitude of voltage will be augmented on two interfaces after adding the active/lossy components. Then we realize the active amplification of evanescent waves and show that the transmission coefficient will be larger than 0 dB near the resonant frequency, which evidently illustrates the active feature of the medium. Both of these two applications have to satisfy the anti-matching conditions to fulfill the resonance and tunneling effect.