Figure 3.

Finite-difference time-domain simulations of the nanogaps between the Au NPs and Au film. (a) Resonant electric field profile of Au NP coupled with different thicknesses of Au film from 5 to 50 nm under p-polarized plane wave illumination incident at 55°. (b) Scattering intensity under unpolarized plane wave illumination at 55° and collected over a cone with numerical aperture NA = 0.8, to replicate the experimental dark-field configuration. (c) Shift of the resonance with increasing Au film thickness.