New optical nonlinear crystallized glasses and YAG laser-induced crystalline dot formation in rare-earth bismuth borate system

New optical nonlinear transparent surface crystallized glasses have been successfully fabricated in the system of Ln₂O₃-Bi₂O₃-B₂O₃ (Ln=La, Sm, Gd). The second harmonic (SH) generation from the crystalline phases at the surface layers has been confirmed from Maker fringe measurements. It is suggested that the optical nonlinear crystals precipitated through the crystallization of Ln₂O₃-Bi₂O₃-B₂O₃ glasses would be new metastable Bi_xLn_1-xBO₃ phases in which Bi³⁺ ions in BiBO₃ are substituted by Ln³⁺ ions. The thickness of crystallized surface was approximately 5 μm and SH intensity was 0.02 compared with that of the Z-cut α-quartz with a thickness of 0.6 mm. In 12.5Sm₂O₃·30Bi₂O₃·57.5 B₂O₃ glass, the crystalline dots with diameters of 5-65 μm are formed by the irradiation of CW YAG laser with a wavelength of 1064 nm (at 0.6 and 0.7 W, for 1-240 s), and it is found that these crystalline dots generate optical SH waves. This is the first finding on optical nonlinear crystalline dot formation by YAG laser irradiation in bismuth-containing glasses.