Influence of slits spacing on the terahertz transmission properties of double sub-wavelength metallic slits

In this paper, the influence of slits spacing on the terahertz transmission properties of double metallic slits is investigated experimentally. THz TDS is used to measure the transmission properties of two polarized THz radiation (TM polarization and TE polarization). Structures fabricated in the copper film with thickness of 60 mum are examined. For the TE mode, non-resonant transmission features are present. However, the position of the minimal transmissivity can be varied with the slits spacing. In the case of the TM mode, the resonant transmission of the double slits has been demonstrated. Furthermore, it is shown that the position of the resonant peak is related to the slits spacing. This effect may be interpreted as the coupling of THz radiation with waveguide resonances located in the slits.