The propagation characteristics of THz radiation in hollow circular waveguides coated with different material films

In the present study, the propagation characteristics of terahertz radiation in both metallic film-coated and dielectric film-coated hollow waveguides have been theoretically analyzed. The dominant modes in metallic film-coated and metal/dielectric film-coated hollow waveguides are respectively TE11 and HE11 modes. Theoretical attenuation coefficients of terahertz radiations in hollow waveguides with a bore diameter of 1mm film-coated with Au, Pb and Ni at different incident frequencies are compared. The dominant mode, i.e. TE11 mode, as a function of bore diameter in hollow waveguides film-coated with different metals are calculated at a given incident frequency. An additional dielectric film with appropriate thickness on the metal films can effectively enhance the wave reflection, resulting in decreased attenuation of the terahertz radiation propagating in hollow waveguides. Calculated results indicate that the attenuation of the terahertz radiation in metal/dielectric film-coated hollow waveguide with a bore diameter of 1mm for a given incident wavelength of 200μm is about 4 times lower than that in metal hollow waveguide with the same bore diameter.

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