Nonlinear optical crystal-line writing in glass by yttrium aluminum garnet laser irradiation

Crystal lines with second-order optical nonlinearity have been successfully fabricated at the surface of 10Sm2O3.35Bi2O3.55B2O3 glass by continuous irradiation of Nd:YAG laser. The laser-induced crystalline phase was confirmed to be Bi0.7Sm0.3BO3 by x-ray diffraction measurements, and second-harmonic generation (SHG) from the phase was clearly observed. An array structure of crystal lines was fabricated by laser writing under automatic computer control, and Maker fringe patterns of SHG were observed, indicating that the direction of polarization in the structure with a crystal line array was parallel to the sample surface. In addition, we measured polarization optical microphotographs, and found uniform phase retardation for a whole length of crystal lines. It is strongly suggested from these results that crystal lines by laser irradiation are formed in single-domain crystalline phase (single crystal) with second-order nonlinearity.