From waveguiding to spatial localization of THz waves within a plasmonic metallic grating

In this paper, we have derived the dispersion relations for terahertz (THz) waves propagating in a direction parallel to the surface of a perfect conducting plane hosting an array of 1-D grooves having a constant depth. Since the dispersion relations for the fundamental surface mode resemble those for the surface plasmon polaritons (SPPs) at optical frequencies, such a uniform grating can be used to effectively guide THz waves. The dispersion relations for these spoof SPPs can be tailored by choosing the geometric parameters of the surface structures. We show that a graded metallic surface grating can be used to trap THz waves at different locations of the surface grating corresponding to the different wavelengths of the waves.