Minimization of reflection at the boundaries of a finite-size coupled terahertz cavity in a metal air-gap waveguide

We show that reflections at the boundaries of a finite-size coupled terahertz cavity in a metal air-gap waveguide can be minimized by introducing antireflection slits. The optimal values of design parameters for the minimal reflection can be obtained using the one-dimensional antireflection coating theory and finite-difference time-domain simulations. It is experimentally demonstrated that the optimized antireflection slits significantly reduce the finite-size effects such as the strong Fabry-Perot oscillations in the transmission spectrum and the variations in the group velocity curve. (C) 2013 AIP Publishing LLC.