Investigation of Resonance Modulation of a Single Rhombic Plasmonic Nanoparticle

Optical extinction resonant properties of the silver rhombic plasmonic nanoparticles in visible regime were investigated by means of finite difference time domain method algorithm-based computational numerical calculation. Considering aspect ratio (a/b) of the x- and y-axes of the rhombic particles, the polarization in different angles of the incident light, and the index of the surrounding medium, we studied the extinction properties of a single rhombus. The simulation results show that there is only one clear resonance peak in the visible regime, and the corresponding plasmon mode is a dipolar plasmon mode. Along the direction of the light polarization, with the increase of the aspect ratio (a/b), red shift of the resonant peak occurs and the extinction efficiency increases accordingly. With the polarization angle varying from 0° to 90°, the resonance peaks show a small blue shift and the corresponding extinction efficiency varies slightly consequently. The tailoring ability of the resonance frequency is shown to be improved due to a unique interaction of local geometry with surface charge distributions.