Theoretical Considerations on Plasmonic Enhancement of THz Electric Field in Parallel-Plate Waveguides Coupled to V-groove Tapered Waveguides

Abstract

Plasmonic waveguides of tapered structures such as metallic V-groove and cone have the capability to confine terahertz (THz) electromagnetic waves into an area smaller than the diffraction limit. We experimentally demonstrated that parallel-plate waveguides (PPWGs) coupled to V-groove tapered waveguides are very simple and useful structures to increase the sensitivity of electrooptic sampling technique due to the enhancement of electric field of linearly polarized THz waves1). However, a mechanism of the enhancement is not enough to provide theoretically because plasmonic effects are frequently ignored under the condition of perfect conductor approximation for metallic materials in the THz region. This paper provides a theoretical method to calculate enhancement factors of electric field for THz waves in PPWGs coupled to V-groove waveguides as shown in Fig.1 by considering the voltage reflection coefficient of two plasmonic modes in parallel-plate and V-groove waveguides.