Numerical and experimental analysis of a polarization-sensitive plasmonic diffractive metasurface for directional coupling of optical waves

Abstract

Advanced applications in nanophotonics demand precise and effective control over optical fields. For this purpose, a variety of complex plasmonic nanostructures have been designed. While these nanostructures satisfy the need for controlling the directionality of surface plasmons, they are limited as propagation in different directions requires re-fabrication of such nanostructures. Therefore, developing a plasmonic metasurface to allow directional coupling to surface plasmons in a dynamic manner, through controlling the polarization state of the incident light, could overcome this limitation. The main objective of this thesis is to study the near-field interference of lattice plasmon modes with dipolar and quadrupolar nature as a mechanism to have dynamic directional coupling over a broad spectral range. The aim is to dynamically control propagation direction of surface plasmons by using the polarization degrees of freedom and to be able to tune the power in opposite directions with different ratios over a broad range of wavelengths. The results presented in this thesis may have impact on future fundamental and applied plasmonics research field. The diffraction-assisted directionality of the split ring resonator metasurface could hold potential for applications in various polarization-selective couplers such as circular-polarization beam splitters and tunable polarization spectral filters.