Numerical Calculation of Surface Plasmon Polariton Lens Based on 3D Model of Cloud System

Abstract

A new design scheme of surface plasmon polariton lens is proposed. In this scheme, dielectric gratings are placed on the outer surface of two subwavelength apertures to realize the effective convergence of human beam. The results show that the effective refractive index can be effectively controlled by adjusting the width and dielectric constant of the sub wavelength apertures, so as to realize the control of the propagation properties of the surface plasmon polaritons in the sub wavelength metal plate waveguide structure. The finite-difference time-domain (FDTD) method combined with perfectly matched layer (PML) boundary conditions is used to simulate the light field distribution in the structure. The influence of grating period number on the imaging characteristics is discussed, and the physical mechanism of nano focusing effect is deeply understood. The results show that the focal length and focal spot increase with the increase of the number of surface gratings. When the number of gratings increases from 5 to 11, the focal length increases from 1.715pm to 2.325pm, and the focal spot size increases from 0.615pm to 1.715pm. This structure may be used as nanofocusing devices in future integrated optical circuits.