Analysis of diffractive optical elements using a nonuniform finite-difference time-domain method

We present the analysis of diffractive optical elements (DOEs) using a two-dimensional nonuniform finite-difference time-domain (FDTD) method. Because the feature sizes in a DOE profile are in general irregular, their analysis using a conventional formulation of the FDTD, i.e., a uniform orthogonal grid, typically requires a high spatial sampling. This in turn raises the computational time and memory requirements for analysis. However, by using a nonuniform grid configuration one can more accurately represent the computation boundary of the DOE, and consequently reduce computational costs. To this end we apply our method to the analysis of both multilevel and subwavelength DOEs to illustrate its utility. (C) 2001 Society of Photo-Optical Instrumentation Engineers.