Study of radiative losses of terahertz surface plasmons on plane metal-dielectric interfaces

Radiative losses of terahertz surface plasmons (SPs) on plane metal-dielectric interfaces have been studied. Experiments performed with "gold - zinc sulfate - air" plane structures at a 130 mu m wavelength have shown that a thin-film dielectric coating of the metal of about lambda/500 thickness could double the SP propagation length. In addition, an optimal dielectric layer thickness corresponding to the minimum total SPs energy loss has been found. Experiments with two sets of samples of different quality of preparation combined with atomic force microscopy surface characterization demonstrated the influence of surface structure (roughness, grain, layer thickness uniformity) on the propagation length and optimal dielectric layer thickness.