Formation and laser patterning of perovskite-type KNbO3 crystals in aluminoborate glasses

Perovskite-type nonlinear optical KNbO3 (KN) crystals are synthesized from 40K2O-25Nb2O5-35B2O3 (KNB) and 40K2O-25Nb2O5-25B2O3-10Al2O3 (KNBA) (mol%) glasses by using a conventional glass-ceramics method. It is found from X-ray diffraction analyses and Raman scattering spectrum measurements that the addition of Al2O3 to glass is effective for the formation of perovskite-type KN crystals. A continuous wave Yb:YVO4 fiber laser (wavelength: 1080 nm) is irradiated onto the surface of CuO-doped (2 mol%) KNB and KNBA glasses, and in particular, perovskite-type KN crystals are patterned in the condition of the laser power of 0.9 W and laser scanning speed of 8 μm/s for KNBA glass containing Al2O3. The formation of metastable (not perovskite-type) KN crystals is also confirmed in the samples crystallized in an electric furnace and in laser-patterned lines. The formation behavior of KN crystals in the glasses is discussed from the point of view of glass composition.