Transmission characteristics of finite-size, two-dimensional metallic photonic crystals studied by THz time domain spectroscopy

Two-dimensional metallic photonic crystals (2D-MPC) are composed of an equilateral array of hexagonally close packed circular waveguides. This type of 2D-MPC has been used as band-pass filters or frequency selective surfaces in the millimeter region. The band-pass characteristics are determined from several parameters, i.e. diameter of the circular holes (0.69 mm), spacing between the centers of them (1.13 mm), and length of the circular waveguides (0.5 mm). The air-filling fraction of this 2D-MPC is 34%. We measured the transmission spectra of the 2D-MPC in the frequency range from 0.1 to 1 THz using the THz time domain spectroscopy.