Terahertz propagation in structured metals

Electromagnetic wave propagation in structured metals has attracted strong attention in wide wavelength regions from microwave to visible. We have investigated transmission properties of metal hole arrays and related structures in the terahertz region by using the terahertz time-domain spectroscopy (THz-TDS). We have found a variety of transmission properties depending on the periodic structure of metals, i. e. extraordinary transmission, large polarization conversion, large optical activity, etc. Some of the properties are explained by the surface plasmon-polariton and/or the local structure of holes.