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.

This 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 as PowerPoint slide