Adiabatic compression of parallel-plate metal waveguides for sensitivity enhancement of waveguide THz time-domain spectroscopy

Abstract

We demonstrate the efficient coupling of THz pulses into and out of an adiabatically compressed parallel-plate metal waveguide. The plate separation of the 63.5-mm long, compressed waveguide was fixed at 103μm at the entrance and exit ends for efficient coupling, but could be reduced in the middle. The experimental results show strong transmission of the THz signal through the compressed waveguide for a minimum midpoint separation of only 8μm. This technique can be used to achieve efficient coupling together with higher sensitivity for waveguide THz-TDS.