Effects of a silicon probe on gold nanoparticles on glass under evanescent illumination

We have numerically investigated the influence of a nanoscale silicon tip in proximity to an illuminated gold nanoparticle. We describe how the position of the high-permittivity tip and the size of the nanoparticle impact the absorption, peak electric field and surface plasmon resonance wavelength under different illumination conditions. We detail the finite element method (FEM) approach we have used, whereby we specify a volume excitation field analytically and calculate the difference between this source field and the total field (i.e., scattered-field formulation). We show that a nanoscale tip can locally enhance the absorption of the particle as well as the peak electric field at length scales far smaller than the wavelength of the incident light.