A HYBRID FINITE-ELEMENT BOUNDARY-ELEMENT METHOD FOR THE ANALYSIS OF DIFFRACTIVE ELEMENTS

We apply a two-dimensional hybrid finite element-boundary element meth od to the analysis of diffractive optical elements (DOEs). We use the finite element method to solve Helmholtz's equation in the interior of a DOE and use the boundary element method, a Green's function approac h, to determine the fields exterior to the DOE. We couple the two meth ods at the DOE surface by enforcing field continuity conditions. We va lidate our implementation by comparing its results to the analytic sol ution for diffraction from a dielectric cylinder and to the scalar sol ution for far-field diffraction from a dielectric slab. We use the hyb rid method to analyse the diffraction from an eight-level phase lens a nd a binary-phase lens that has subwavelength features.