PHASE GRATING OF A COMBINATION PATTERN REFRACTION MODIFICATION TYPE

摘要

The phase grating (1) has dual grating elements (aD) including convex and concave portions of thin layers. The portions have different thicknesses, are regularly arranged and formed of materials which are different in refractive index between the convex and the concave portions. The refractive index of the material forming the convex portion of the dual grating elements can be higher than a refractive index of material forming the concave portion. The convex portion of the dual grating elements is formed in the shape of a square in section.