Birefringence imaging and orientation of laser patterned β-BaB2O4 crystals with bending and curved shapes in glass

• β-BaB2O4 crystals with bending and curved shapes were patterned by laser irradiations.
• The orientation was examined from the birefringence imaging.
• Highly c-axis oriented crystals follows along laser scanning direction.
• The c-axis direction changes gradually at the bending point.
• The laser-induced crystallization opens a new door in crystal growth engineering.

Nonlinear optical β-BaB2O4 crystals (β-BBO) with bending and curved shapes were patterned at the surface of 8Sm2O3–42BaO–50B2O3 glass by laser irradiations (Yb:YVO4 laser with a wavelength of 1080 nm, power of 0.8 W, and scanning speed of 4 μm/s), and the orientation state of β-BBO crystals was examined from the birefringence imaging obtained by polarization optical microscope (POM) observations. The formation (crystallization) of β-BBO crystals follows along laser scanning direction even if the laser scanning direction changes at a certain point within the bending angle of 60°. The birefringence images indicate that the formation of highly c-axis oriented β-BBO crystals follows along laser scanning direction even if the laser scanning direction changes, and in particular the direction of the c-axis of β-BBO crystals changes gradually at the bending point. The model for the orientation of the c-axis of β-BBO near the bending point is proposed. The present study proposes that the laser-induced crystallization opens a new door for the science and technology in crystal growth engineering.

This figure shows the birefringence images obtained by the Abrio IM imaging system (λ=546 nm) for the laser-patterned β-BaB2O4 crystal line with the bending angle of 45° in the glass. The relation between the direction of slow axis and color is also shown. It is demonstrated that the formation (crystallization) of highly c-axis oriented β-BaB2O4 crystals follows along laser scanning direction even if the laser scanning direction changes. Figure optionsDownload as PowerPoint slide