Numerical characterization of optical properties of tapered plasmonic structure on a cantilever pyramidal tip for plasmon nanofocusing

Abstract

The plasmon nanofocusing process has been widely implemented in near-field scanning optical microscopy (NSOM) recently because it allows generating a background-free nanolight source at the apex of a metallic tip, enabling high contrast imaging at the nanoscale. In plasmon nanofocusing-assisted NSOM, the metallic tip properties play a vital role in generating an intense and well-confined nanolight source by controlling the plasmons’ behavior. This is why various tip designs have been developed so far. Recently, our group has also developed a metallic tapered tip, composed of a dielectric pyramidal base and a thin metallic layer coated on one side of the pyramid, using a novel fabrication method that allows tuning the optical properties of a tip depending on the requirement. Although our metallic tip has a unique advantage of tuning its optical properties, it has not yet been well studied. In this work, we present a thorough study of the optical properties of our metallic tip that depends on its parameters, such as the dielectric material, metal thickness, and cone angle, using finite-difference time-domain simulations. This particular study will allow us to understand controlling the tip’s optical properties and expand it for a wide range of applications.