Circuit-theory interpretation of optical multilayer ENZ metamaterial with enhanced bandwidth

Recently proposed multi-layer optical ENZ metamaterial with enhanced bandwidth is analyzed using a simple transmission-line-based equivalent circuit. It is shown that a differentially short segment of this metamaterial can be thought of as a simple band-pass filter, transversal branch of which is a series combination of N lossy LC tank circuits (N being the number of layers). This equivalent circuit gives a clear picture of the background physics. Furthermore, it also enables a very simple transfer of the basic principle of operation into any frequency regime such as RF, microwaves or THz. The equivalent circuit is used for the analysis of the influence of losses on the ENZ bandwidth.