Electromagnetic diffraction analysis of columned grid gratings

Binary optics processing methods may be applied to a glass or silicon substrate to generate an array of small columns in order to enhance transmission. We employ the rigorous vector coupled-wave theory to analyse the electromagnetic diffraction nature of two-dimensional columned grid gratings. By computer simulation and calculation, the relation between the reflectivity and the structure parameters of such gratings is presented. These results show that a glass grating can achieve antireflection over almost the whole visible light waveband for unpolarized light, while a silicon grating with a columned grid substrate can achieve low reflectance over as broad a field of view as a tapered silicon grating structure, but it can be fabricated more simply.