Numerical Modeling of Radiation Focusing by Dielectric Microcylinders with Several Layers

In this paper, the light focusing by dielectric microcylinders with several layers was numerically studied by using the finite element method implemented in COMSOL Multiphysics. Different materials for the top layer were proposed during the research (refractive indices are 1.59, 1.8, 1.9) while the core was proposed from fused silica glass (refractive index is 1.45). It was shown that the dielectric shell allows to increases the maximum intensity of the formed photonic nanojet. Choosing the design of a two-layered microcylinder it is possible to form a compact focal spot (TE-polarization) or increase the length of the produced photonic nanojet. Obtained results were verified by another software package FullWAVE which implements a finite difference time domain method. The simulation results are in good agreement.