Formulation and application of the finite-difference time-domain method for the analysis of axially symmetric diffractive optical elements

We formulate and apply an efficient finite-difference time-domain algorithm to the analysis of axially symmetric diffractive optical elements. We disc uss aspects relating to minimizing numerical dispersion in the incident fie ld, application of absorbing boundary conditions in the radial direction, c onvergence to a steady state, and propagation of the steady-state electroma gnetic fields from the finite-difference time-domain region to the plane of interest. Incorporation of these aspects into a single finite-difference t ime-domain algorithm results in an extremely efficient and robust method fo r diffractive optical element analysis. Application to the analysis of subw avelength and multilevel lenses, both with and without loss, for focusing p lanar and Gaussian beams is presented. (C) 1999 Optical Society of America [S0740-3232(99)00805-4].