Optimization of surface plasmon polariton generation in a nanocone through linearly polarized laser beams

In this paper we present numerical FDTD calculations, optimizing experimental setup conditions for surface plasmon polariton (SPP) generation. The simulation considers a silver nanocone placed on a Si3N4 membrane, and studies the effects on the apex for a linearly polarized Gaussian light beam impinging from below or from the side of the cone. Radially polarized focused beams already proved to generate efficiently SPPs; in this work, we show that also linear polarization leads to an efficient generation of SPPs on the cone surface, as long as tilt angle and numeric aperture are optimized. In particular, we show that our setup conditions and proposed device, designed for a λ = 633 nm linearly polarized He–Ne laser, can enhance the incoming electric field up to 150 times at the apex of the cone.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► FDTD simulation for a realistic geometry of a silver plasmonic tapered waveguide. ► Under optimized conditions linearly polarized laser beam can produce TM0-like plasmonic modes able to reach the nanocone tip. ► Angle of incidence and objective numeric aperture affect drastically electric field enhancement on the cone apex. ► Electric field enhancement may be higher than 150 for a He–Ne laser.