Influence of Grating Parameters on the Field Enhancement of an Optical Antenna under Laser Irradiation

In this study, a new approach for simulation of electric field enhancement of plane wave laser around optical antenna was used to convert free-propagating optical radiation to localized energy. A tapered gold tip design as a novel geometry of optical antenna is introduced and numerically analyzed based on particle swarm optimization (PSO) by solving the Maxwell equations with FDTD simulation Lumerical Software. Five simulation stages of grating parameters to reach the maximum output intensity at the gold tip hot spot were performed with 90° laser incident angle. The optimal values of the grating period “a”, distance of the last circular grating from tip apex “b”, depth of etched grating “T” and duty cycle of grating “D.C” were obtained a=262.2 nm, b=759.5 nm, T=30.1 nm, and D.C.=0.31 respectively. By using these optimal parameters for the gold tapered tip with a cone angle of 30° at room temperature, the maximum output intensity (|Emax|2) at the hot spot was obtained 52.4751.