Laser patterning and preferential orientation of two-dimensional planar β-BaB2O4 crystals on the glass surface

The laser-induced crystallization method is applied to pattern two-dimensional planar β-BaB2O4 crystals on the surface of Sm2O3–BaO–B2O3 glass. By scanning Yb:YVO4 fiber lasers (wavelength: 1080 nm) continuously with a small step (0.5 μm) between laser irradiated areas, homogeneous planar β-BaB2O4 crystals are patterned successfully, and a preferential growth orientation of β-BaB2O4 crystals is confirmed from linearly polarized micro-Raman scattering spectrum and second harmonic intensity measurements. It is found that the crystal growth direction is perpendicular to the laser scanning direction. This relation, i.e., the perpendicular relation, is different from the behavior in discrete crystal line patterning, where the crystal growth direction is consistent with the laser scanning direction. The present study proposes the possibility of the control of crystal growth direction in laser-induced crystallization in glasses. - Graphical abstract: This figure shows confocal scanning laser microscope and polarized optical microscope photographs for β-BaB2O4 crystals obtained by laser irradiations. The laser scanning was repeated with a step of 0.5 μm between the lines using the condition of the power of P=0.8 W and a laser scanning speed of S=8 μm/s. It is suggested that β-BaB2O4 crystals in the overlapped laser-irradiated region are highly oriented and the c-axis direction of β-BaB2O4 crystals is perpendicular to the laser scanning direction. Highlights: ► Laser-induced crystallization method is applied to pattern β-BaB2O4 crystals. ► Two-dimensional planar crystals are patterned on the glass surface. ► Preferential growth orientation of β-BaB2O4 crystals is confirmed. ► Crystal growth direction is perpendicular to the laser scanning direction.