Semi-transparent barium borate surface crystallization for second harmonic generation

Abstract Glasses from the barium borate system, x B 2 O 3 –(100 − x )BaO (50 x λ = 435.8 nm) and densities ranging from 3.85 g cm −3 to 3.75 g cm −3 , were synthesized by a conventional melting-quenching method. 75 × 75 × 5 mm 3 samples were prepared from the barium borate glass, which was transparent in the visible region and very stable. The characteristic temperatures of the BBO60 ( x = 60) glass, which were determined by differential thermal analysis at 10 °C min −1 , were T g = 570 °C, T x = 671 °C, and T p = 685 °C (±2 °C). The glass samples were then heat-treated for controlled crystallization. 57B 2 O 3 –43BaO planar samples, measuring 15 × 15 × 3 mm 3 , heat-treated at 610 °C for periods varying from 24 h to 60 h, exhibited a surface crystallization mechanism. The crystalline layers were analyzed by X-ray diffraction and identified as β-BaB 2 O 4 . These crystallized layers showed second harmonic generation (SHG) when irradiated by a 1064 nm laser beam (Nd:YAG) with 300 mW of power. The SHG intensity was compared with a Y-oriented single crystal α-quartz plate.