Electromagnetic wave funneling through λ/10,000,000 nanogaps for microwave regime

We observe microwave funneling through few nanometer-wide gap arrays. Nanogaps having rectangular ring shaped geometries are fabricated by atomic layer lithography technique. Microwave transmittance in 10~40 GHz range is measured by vector network analyzer (VNA) connected with pairs of rectangular waveguides supporting TE₁₀ mode. The peak transmittance of 2 nm width gap is about 45% and it corresponds to the electric field enhancement factor of over 10,000. Terahertz transmittance is also measured by time domain spectroscopy to further verify the funneling phenomena in microwave regime.