Controlling the direction of propagation of surface plasmons via graded index effective dielectric media

In this work, we propose a mechanism to steer and tailor surface plasmon propagation by using graded index concepts. In this approach, a block of dielectric with fixed thickness is placed on top of a semi-infinite metal. The beam steerers are then designed by simply changing the height of the dielectric in the direction perpendicular to the propagation axis. The analytical design is presented and several structures are evaluated with the ability to steer the incoming surface plasmons at any desired output angle.V.P.-P. is supported by the Newcastle University (Newcastle University Research Fellow)

Angle-susceptible sensing metasurface in terahertz regime

Trabajo presentado a la 3rd International Conference "Terahertz and Microwave Radiation: Generation, Detection and Applications (TERA 2018)", celebrada en Rusia del 22 al 25 de octubre de 2018Nowadays thin-film coatings and structures are widely used in advanced industrial and scientific ap-plications that makes the tasks of thin-film sensing highly demanded in practice. Last decade, stimulated by progress in terahertz (THz) instrumentation, a keen interest has been attracted to the THz spectral range to develop its potential for detecting and measuring properties of thin films. The THz radiation can be an alternative to visible and IR waves when examining optically opaque coatings. Meanwhile, due to a rela-tively large wavelength λ, the conventional spectro-scopic methods (TDS-, FDS-, FTIR-, BWO-based) are ill-suited for direct characterization of films with the thickness d of about 2−4 orders of magnitude smaller than λ. This problem can be solved with met-amaterials, in particular, with plasmonic metasurfaces (PMSs) [1–5]. The plasmonic resonance exhibits a high sensitivity of its spectral response to the dielec-tric environment due to a strong field localization what makes possible measuring of analyte layers sat-isfying d << λ condition. The traditional approach of THz thin-film sensing with PMSs is based on detecting a frequency shift of the resonance when the analyte is deposited onto the PMS. In this work, we present the idea to substitute THz spectral measurements for tracking the PMS re-sponse at a fixed wavelength upon changing the incidence angle θ of the exciting THz beam. This concept works well for the PMS with a narrowband resonance sensitive to θ. The results of the numerical investigations and experimental study of such PMS designed as a single-layer array of hexagon-shaped annular slots (Fig. 1) with angle-susceptible resonant transmission near 0.85 THz are presented.The work is partially supported by the Russian Foundation for Basic Research (Project #17-32-80039)