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Formation of Elemental Distribution in Glasses by Femtosecond Laser Irradiation

We report on the fabrication of optical waveguides and the precipitation of nonlinear optical crystals inside glass caused by local element migration with high-repetition femtosecond laser irradiation. Elements that contribute to the high refractive index migrated to the center of the focal region because of the femtosecond laser irradiation in phosphate and borate glasses. Based on this result, we successfully wrote optical waveguides in these glasses, where element distributions were continuously induced along a path traversed by the focal point. Furthermore, we succeeded in space-selective precipitation of nonlinear optical crystals such as β-BBO inside glass by controlling the thermophysical property (crystallization temperature).