High transmittance and wide pass-band filter based on a three-layer structure of metal-dielectric-metal hole arrays

In this paper, square lattices of air holes were fabricated on a three-layer structure of metal-dielectric-metal using micromachining technology. The metal-dielectric-metal structure is based on RT/duroid 5870 produced by Rogers corporation. The square period is 400 μm and the radius of circular hole is 100 μm. The thickness of the structure is about 863 μm with metal thickness of 39.2 μm and dielectric layer thickness of 785 μm. The loss and dispersion of the dielectric layer with the dielectric constant of 2.33 are low at microwave frequencies. Terahertz transmission spectra through the sample were measured by the state-of-the-art THz-TDS system. Experimental results show that there is a transmittance centered at 1 THz with a wide pass-band exceeding 100 GHz. Transmission spectra calculated by FDTD method were given for comparisons and showed good agreements with the experimental results. Through analysis, the extraordinary transmission phenomena are caused by both the Febry-Parot effect and surface plasmon polaritons existing on the metal arrays.