摘要 |
A thin film type optical device comprises a substrate formed of lithium niobate crystal or lithium tantalate crystal, and a light waveguide path layer comprising protons introduced into the surface of the substrate and having a refractive index higher than that of the substrate. The absorption peak of the infrared absorption spectrum of OH radical by the protons in the light waveguide path layer exists in the range of wave number 3480 cm-1 to 3503 cm-1.
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