Investigation of propagation properties of plasmonic nanostructures with nonparaxial Gaussian beam illumination

An optical probe with a single aperture flanked by depth-tuned grooves is presented. It is employed as an example to investigate propagation properties of the plasmonic nanostructures with a nonparaxial Gaussian beam illumination. The propagation through the subwavelength aperture is the process that a near-field diffraction of the Gaussian beam interferes with the surface plasmon polaritons (SPP) wave induced wavelets on surface of the grooves. An enhanced optical transmission at the exit side of a subwavelength aperture and a degraded reflection at top side of the compound dielectric/metal nanostructure (air/glass/C/Ag/air) of the probe can be generated with this illumination. Characteristics of the Gaussian beam illumination have been studied numerically via analysis of the transmission and reflection issues. In contrast, the results for plane wave illumination were given as well. Two-dimensional (2D) finite-difference time-domain (FDTD) algorithm is employed for the 2D simulation.