Propagation of terahertz surface plasmon polaritons around a convex metal–dielectric interface

The results of experimental studies of the attenuation of surface plasmon polaritons (SPPs) in the terahertz range excited by free-electron laser radiation (λ=129 and 141 μm) on the gold–ZnS–air cylindrical interfaces are presented in this paper. Because of the additional radiation losses, associated with the curvature of the surface, the attenuation of SPPs in this case significantly exceeds the attenuation of SPPs propagating on a flat surface of the metal. An optoacoustic cell and a microbolometer matrix measured the intensity of plasmons propagating around cylinders of radii of 60 and 30 mm as a function of the azimuthal angle via recording the bulk waves emitted tangentially from the plasmon track. The radiation losses increase with decreasing radius of curvature. In the case of a cylinder with a radius of 60 mm, an increase in the thickness of the dielectric film first reduced the losses to the minimum value at a layer thickness of 1.5 μm, and then the losses sharply grew up.