Morphology and orientation of β-BaB2O4 crystals patterned by laser in the inside of samarium barium borate glass

•β-BaB2O4 crystal lines were patterned in the inside of a glass by lasers.•Laser focal position was moved gradually from the surface to the inside.•Birefringence imaging was observed.•Morphology, size, and orientation of crystals were clarified.•Crystal lines with long lengths (e.g., 20 mm) were patterned at the depth of 200 μm.

Nonlinear optical β-BaB2O4 crystal lines (β-BBO) were patterned in the inside of 8Sm2O3–42BaO–50B2O3 glass by irradiations of continuous-wave Yb:YVO4 lasers with a wavelength of 1080 nm (power: P=0.8–1.0 W, scanning speed: S=0.2–2.5 μm/s), in which the laser focal position was moved gradually from the surface to the inside. The morphology, size, and orientation of β-BBO crystals were examined from polarization optical microscope and birefringence imaging observations. It was demonstrated that c-axis oriented β-BBO crystals with long lengths (e.g., 20 mm) were patterned in the inside of the glass. The morphology of β-BBO in the cross-section of lines was a rectangular shape with rounded corners, and the volume of β-BBO formed increased with increasing laser power and with decreasing laser scanning speed. The maximum depth in the inside from the surface for β-BBO patterning increased with increasing laser power, e.g., Dmax~100 μm at P=0.8 W, Dmax~170 μm at P=0.9 W, and Dmax~200 μm at P=1 W. The present study proposes that the laser-induced crystallization opens a new door for applied engineering in glassy solids.

Graphical abstractThis figure shows the POM photographs for β-BaB2O4 crystal lines patterned by cw Yb:YVO4 fiber laser irradiations with a laser power of P=0.8 W and a laser scanning speed S=2 μm/s in the glass. The laser focal point was moved gradually from the surface into the inside. The results shown in Fig. 1 demonstrate that it is possible to pattern highly oriented β-BaB2O4 crystals even in the inside of glasses.Figure optionsDownload full-size imageDownload as PowerPoint slide