Morphology of the polar twin structure in Czochralski grown α-SrB4O7 crystals

The arrangement of a polar twin structure in Czochralski grown α-SrB4O7 crystals has been investigated. The transversal twin boundaries are stretched along [101] and [100] directions. The lateral twin boundaries are parallel to (010) plane. The twin structures have an extension up to centimeter size in all directions. Supposedly, they originate from polysynthetic polar microtwins revealed to form in (101¯) and (1¯01¯) growth pyramids. The dimensions, planarity and thickness stability of each individual twin are favorable for organizing quasi-phase matching conditions for nonlinear optical doubling of high-aperture beams.