Terahertz nanoresonators: Giant field enhancement and ultrabroadband performance

Transmission of terahertz (THz) electromagnetic waves through a series of nanoresonator arrays punctured in a thin metallic film is investigated. Over 30% of normalized transmitted amplitude is observed with only 0.18% of aperture-coverage, implying an electric field enhancement of 170. Increasing the coverage to 0.6% results in a 90% normalized amplitude, with a broader line width. Inspired by log-periodic antenna, we put ten nanoresonators with four different lengths per unit cell, succeeding in an ultrabroadband THz filter with one decade width between 0.2 and 2.0 THz.