Energy tunnelling through an ultrasmall epsilon-near-zero channel in circular waveguide

Based on the conservation of complex power technique, the authors demonstrate theoretically that electromagnetic waves can be squeezed and tunnelled through very small circular channel waveguides at cut-off frequency, which mimics the response of epsilon-near-zero (ENZ) materials. Owing to the infinite phase velocity (zero phase delay) of the wave propagating in the ENZ material, this tunnelling phenomenon is shown to be fundamentally independent of the length and location of the channel guide.