Second-order optical nonlinearities of metastable BiBO3 phases in crystallized glasses

Metastable BiBO3 and rare-earth (RE)-doped RExBi1−xBO3 crystals were prepared through the crystallization of 50Bi2O3·50B2O3 and xRE2O3·(50−x)Bi2O3·50B2O3 glasses (RE=Y, La, Gd, Yb), and their second harmonic (SH) intensities were examined using the Kurtz powder method. It was confirmed that BiBO3 has two different crystalline forms, i.e., BiBO3(I) and BiBO3(II), and that BiBO3(I) transforms into BiBO3(II) at temperatures around 500 °C. Both phases were found to be nonlinear optical crystals with a phase matchable character, and the SH intensity of BiBO3(II) powders was approximately 110 times as large as α-quartz powders. The incorporation of RE3+ into BiBO3(II) was confirmed from X-ray diffraction analysis, and in particular, GdxBi1−xBO3(II) showed an enhanced SH intensity of approximately 145 times as large as α-quartz.