Modeling considerations for rigorous boundary element method analysis of diffractive optical elements

Critical modeling issues relating to rigorous boundary element method (BEM) analysis of diffractive optical elements (DOEs) are identified. Electric-f ield integral equation (EFIE) and combined-field integral equation (CFIE) f ormulations of the BEM are introduced and implemented. The nonphysical inte rior resonance phenomenon and thin-shape breakdown are illustrated in the c ontext of a guided-mode resonant subwavelength grating. It is shown that mo deling such structures by using an open geometric configuration eliminates these problems that are associated with the EFIE BEM. Necessary precautions in defining the incident fields are also presented for the analysis of mul tiple-layer DOEs. (C) 2001 Optical Society of America.