Extraordinary transmission in metamaterial-loaded waveguides: effective-medium models, microwave experiments and tight binding studies

We show that a metallic waveguide behaves as an electric (magnetic) plasma for transverse-electric (transverse-magnetic) polarized electromagnetic (EM) waves at frequencies below cut-off value. Inserting anisotropic resonance structures of either electric or magnetic type into a waveguide, we find extraordinary transmissions of EM waves with different polarizations through the waveguide at frequencies well below the waveguidepsilas cut-off value, following two different mechanisms. Microwave experiments, in excellent agreements with finite-different-time-domain simulations, are performed to successfully demonstrate all theoretical predictions. We then perform a systematic study based on tight-binding approximation to understand the underlying physics behind such unusual behaviors.