금속선을 이용한 THz 도파로의 유도특성 향상

Abstract

Because of low attenuation and group velocity dispersion in THz region, single metal wire waveguides have many possible applications in THz spectroscopy and imaging. The THz field intensity concentrate on the single metal wire surface and reduce along increasing distance from metal surface.

Air gaps between the metal wire waveguide and chips(transmitter and receiver chip) are very important factor to influence variation of measured THz amplitude in THz waveguide system. When the transmitter part air gap increased, THz field intensity rapidly decreased to 10% amplitude compared with contacted case at 275μm air gap. In the receiver part air gap, THz field intensity slowly decreased to 48% amplitude at 275μm air gap as compared with the transmitter part air gap.

On the one hand, single metal wire waveguides have low attenuation and group velocity dispersion for straight area, on the other hand, the waveguides have very high attenuation and group velocity dispersion when the waveguides are curved. If conductivity of waveguide is high, the waveguide has low attenuation. However, because of very small electric field in metal, the waveguide have high attenuation when the waveguide were curved. So, using this property I used copper wire because of high conductivity for straight region and stainless steel wire because of low conductivity for curved region to minimize THz loss. Therefore, guidance property of single metal wire waveguide has improved.

Also, I investigated the coupling properties of between two copper wires. The angle-dependent wire to wire coupling effect was measured using an optical fiber guiding laser beam to the reciever chip. The measured THz pulse intensity rapidly decreased with the increase in the angle. At 15 degrees, the THz intensity decreased by about 50% compared with 0 degree wires. Also, at 75 degrees, the THz intensity almost disappeared because there is not coupling. The distribution of the peak to peak angled THz intensity is a Gaussian distribution on centered at 0 degree.