Energy Tunneling: A Way to Achieve Highly Sensitive Material Detection With Sub-Wavelength Resolution

The phenomenon of microwave energy tunneling (ET) has been reported in guided microwave structures loaded with either epsilon-near-zero (ENZ) materials or resonant metallic wires [1]-[14]. A bit of confusion sometimes can arise over the term tunneling, which is often used by physicists, so it seems appropriate here to point out the difference between ET and the well-known particle tunneling encountered in quantum mechanics (Figure 1).