Effective medium theory is useful for designing optical elements with a form-birefringent subwavelength structure. We describe a way to determine the effective refractive indices and the directions of their principal axes for two-dimensional (2-D) subwavelength gratings in the normal incidence case. The effective indices and the directions are calculated from finite coupled-coefficient equations that are used in 2-D rigorous coupled-wave analysis. We use the effective medium theory to calculate transmittance of several kinds of 2-D periodic subwavelength gratings. These results are compared with results of rigorous grating analysis to confirm the predictions of the effective medium theory for 2-D subwavelength gratings. # 1998 Optical Society of America [S0740-3232(98)00106-9] OCIS codes: 150.1380,150.1950,050.2770,160.1190,230.5440,230.3990.
展开▼
