Optical retardation plate and method of manufacturing the same

摘要

A dielectric substrate having a refractive index n₁ is covered with an amorphous dielectric medium having a refractive index n₂ larger than the refractive index n₁, and a rectangular grating is formed in the amorphous dielectric medium through an etching process. When microcrystal is formed in the amorphous dielectric medium through a thermal treatment to increase the refractive index n₂, a magnitude Deltan of structure double refraction increases accordingly. Hence, a phase refraction DeltaPhi of an irregular grating pattern in the rectangular grating becomes large without increasing a depth D of each trench of the rectangular grating, and thus it is possible to obtain an optical retardation plate having a fine periodic structure and having a desired plate retardation.