Figure 1. Schematic model for FEM simulation and e-field enhancement distribution.

(a) The scheme of the plasmonic tweezers and the nanoparticle. The blue arrow denotes the incident direction and the red one demotes the polarization direction. The direction of the incident laser is vertical to the surface of the gold film where the bowtie nano-aperture (BNA) is milled. The incident light is polarized along the direction where the bowtie dimmer arranges. The diameter of the gold nanparticle is 50 nm. (b) The geometry of the BNA, the thickness of the gold film is 100 nm, A = 180 nm, B = 280 nm, D = 70 nm. (c–f) The e-field distribution under different incident wavelength with the distance between the nanoparticle and the tweezers of (c) 10 nm, (d) 20 nm, (e) 40 nm, (f) 60 nm.