Transmission Characteristics Of Terahertz Metallic Subwavelength Simple Structure

At present, electromagnetic wave transmission properties of sub-wavelength metallic structures become a hot topic step by step. In this thesis, terahertz transmission properties through three kinds of simple sub-wavelength metallic structures, including single sub-wavelength metallic circular hole, single sub-wavelength metallic slit and double sub-wavelength metallic slits, are experimentally investigated in the far field by using our own THz time-domain spectroscopy (THz-TDS) system and are theoretically analyzed. Conclusions are obtained as follows: (1) a single sub-wavelength metallic circular hole exhibits the same terahertz transmission properties as that of round metallic waveguide, which are influenced by the diameter of circular hole and the thickness of metal foil. (2) When the different polarized terahertz wave gets through a single sub-wavelength metallic slit, the conesponding transmission properties are different. For the TM mode (the polarization direction of terahertz radiation perpendicular to the slit), the resonant transmission has been demonstrated. According to the relation between the thickness of metal foil and the wavelength of incident radiation, this effect is interpreted by the waveguide coupling theory and resonant Fabry-Perot-like cavity theory. In the case of the TE mode (the polarization direction along to the slit), the transmission characteristics are the same as that of the single sub-wavelength metallic circular hole. (3) For double sub-wavelength metallic slits, the transmission phenomenon of TM-mode and TE-mode are also unlike. Likewise, for the TM mode, the structure of double slits represents the resonant transmission. For the TE mode, although non-resonant transmission peaks are present, there is a point of the minimal transmissivity.Terahertz wave modulated by some simple sub-wavelength metallic structures presented in this paper belongs to the basic study of the surface plasmon optics in the terahertz range, which offers relative reliable evidences of investigating the transmission properties of terahertz radiation through more complex sub-wavelength metallic structures in future.