High-Resolution THz Transmission and Reflection Measurements and Consequent Understanding of Resonant Hole-Arrays

We report high-resolution THz-TDS characterization of the transmission and reflection of a thin metal hole-array in optical contact with a 10 mm thick high-resistivity Si plate. It was found that the red-shift of the [±1, 0] spoof surface-plasmon (SSP) transmission peak from the Wood´s anomaly valley indicates the coupling strength of the SSP wave to the metal surface due to the filling factor and shape of the holes, and that the red-shift provides a measurement of the SSP wave velocity. Our measurements of the amplitude transmission peak, and the corresponding reflection dip, of the hole-array agreed with numerical simulation to an accuracy of ±2 GHz, and the measured phase was in good agreement with simulation. However, our reflection measurements showed a second unexplained dip at the frequency of Wood´s anomaly.