Rigorous coupled-wave analysis for practical planar dielectric gratings: 3 Increase of higher-order lights owing to degenerated complex diffraction

The diffraction efficiencies by practical dielectric holograms are evaluated with the rigorous coupled-wave analysis. As discussed in Parts 1 and 2, only the first reflection light can be diffracted by general sealed volume reflection holograms. Here we discuss the possibility that complex diffraction, which occurs in multiple-grating-storage holograms, makes diffraction efficiencies of higher-order lights increase drastically, i.e., the degenerated complex diffraction. Although evident in special cases only, they appear frequently in actual holographic use.