| 摘要 |
PURPOSE:To obtain a wavelength plate which is tolerant of contamination and damage and easily formed by providing a substrate dielectric provided with a surface relief grating whose in-use wavelength and grating pitch are specified in certain relation and a dielectric medium which has a refracting index much larger than the substrate dielectric. CONSTITUTION:This wavelength plate is constituted including the substrate dielectric 1 provided with the surface relief grating 2 whose relation between the in-use wavelength lambda and grating pitch (d) is so specified that lambda/d>=1.472 and the dielectric medium 3 which is charged on the surface relief grating 2 of the substrate dielectric 1 and has a flat surface and the refractive index much larger than the substrate dielectric 1. Consequently, large birefringence is obtained as compared with when the grating is exposed to the air, the groove depth of the grating manufactured on the dielectric substrate is reduced, and the manufacture is facilitated; and the grating is covered completely with the high-refractive-index dielectric, so the grating is protected from damage and the interface between the dielectric and air is made flat, so that the wavelength plate becomes tolerant of contamination.
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