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 ofplane wave laser around optical antenna was used to convert free-propagating opticalradiation to localized energy. A tapered gold tip design as a novel geometry of opticalantenna 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 atthe gold tip hot spot were performed with 90° laser incident angle. The optimal valuesof the grating period “a”, distance of the last circular grating from tip apex “b”, depth ofetched grating “T” and duty cycle of grating “D.C” were obtained a=262.2 nm, b=759.5nm, T=30.1 nm, and D.C.=0.31 respectively. By using these optimal parameters for thegold tapered tip with a cone angle of 30° at room temperature, the maximum outputintensity (|Emax|2) at the hot spot was obtained 52.4751.