Technique for writing of nonlinear optical single-crystal lines in glass

The technique for the writing of crystal lines in glass by Nd:YAG laser irradiation, selective atom heat processing, is applied to rare-earth (Sm3+, Dy3+) barium borate glasses, and nonlinear optical β-BaB2O4 (β-BBO) crystal lines with a width of ∼5 μm are fabricated. The crystal lines show uniform colors in polarized optical microscope and second-harmonic generation (SHG) measurements. The azimuthal dependence of SHG signals in the crystal lines is the same as that in commercially available β-BBO bulk single crystals. It is demonstrated that the crystal lines written by YAG laser irradiations are β-BBO single crystals with the c-axis orientation along the laser scanning direction.