Physical Insight into the 'Growing' Evanescent Fields of Double-Negative   Metamaterial Lenses Using their Circuit Equivalence
  Pendry in his paper [Phys. Rev. Lett., 85, 3966 (2000)] put forward an idea for a lens made of a lossless metamaterial slab with n = -1, that may provide focusing with resolution beyond the conventional limit. In his analysis, the evanescent wave inside such a lossless double-negative (DNG) slab is 'growing', and thus it 'compensates' the decaying exponential outside of it, providing the sub-wavelength lensing properties of this system. Here, we examine this debated issue of 'growing exponential' from an equivalent circuit viewpoint by analyzing a set of distributed-circuit elements representing evanescent wave interaction with a lossless slab of DNG medium. Our analysis shows that, under certain conditions, the current in series elements and the voltage at the element nodes may attain the dominant increasing due to the suitable resonance of the lossless circuit, providing an alternative physical explanation for 'growing exponential' in Pendry's lens and similar sub-wavelength imaging systems. 
Andrea Alu, and Nader Engheta