Metal wire waveguide based all plasmonic refractive index sensor for terahertz frequencies

Abstract

A terahertz refractive index sensor for liquid analytes consisting of a copper wire waveguide and co-axial layers of PMMA and PVDF is established numerically. The dispersion behavior of the fundamental core and surface mode and their phase matching has been demonstrated that clearly explains the working mechanism of the sensor. A core mode amplitude sensitivity of 59.9 for unit change in refractive index at 269.8μm is obtained for the proposed sensor. It has a large evanescent field penetration depth of 48μm at the phase matching point that can facilitate sensing of analyte refractive index further away from the interface. A definition for group velocity sensitivity is proposed which is then evaluated for the proposed sensor. The near dispersion free behavior of the sensor core mode except around the phase matching point gives it an excellent group velocity sensitivity of 128.9 for unit change in refractive index.