Study of resonant modes for sensing in a multimode planar plasmonic terahertz waveguide

We examine the refractive index sensing capability of the resonant modes in a planar plasmonic terahertz (THz) waveguide. The waveguide is comprised of one dimensional array of periodically arranged rectangular subwavelength grooves. The waveguide configuration supports resonant surface modes at certain frequencies depending on groove parameters and the refractive index of analyte filled in them. The change in refractive index leads to a linear shift in the fundamental as well as higher order modes for fixed parameters of the waveguide structures. Sensitivity and corresponding figure of merit (FoM) of terahertz modes are calculated to analyse the performance of the device.