Plasmonic Terahertz Waveguide Based on Anisotropically Etched Silicon Substrate

We experimentally examine anisotropically etched silicon surfaces for terahertz (THz) plasmonic guided wave applications. Highly doped silicon surfaces are anisotropically etched to form a one-dimensional array of subwavelength concave pyramidal troughs. The plasmonic wave guides are found to support highly confined guided modes both in transverse and longitudinal directions. The resonant frequencies of the modes can be controlled by adjusting the geometrical parameters of the troughs. The existence of guided modes in plasmonic wave guides is also established through finite-element-based numerical simulations. These wave guides could provide a silicon-based alternative to metallic wave guides for use in future THz devices.