Enhancement and depression in second-order optical nonlinearity of Ba ₂TiGe₂O₈ in crystallized glass prepared in a high magnetic field

A magnetic field of H=10 T was applied perpendicularly or parallel to the surface of the 30BaO.15TiO₂.55GeO₂ (BTG) glass during its crystallization, and the effect of the magnetic field on the crystal orientation and second-order optical nonlinearity of the Ba₂TiGe ₂O₂ crystals formed at the glass surface was examined. Compared with the sample prepared by conventional crystallization in zero magnetic field, the c -axis (polarization axis) orientation and second-harmonic intensity of the Ba2 TiGe₂O₈ crystals at the surface were enhanced in the sample fabricated with the field perpendicular to the surface and, by contrast, were depressed in the sample fabricated with the field parallel to the surface. The present study indicates that the application of high magnetic fields during crystallization is a technique to control the crystal orientations and optical properties of BTG crystallized glasses.