High temperature form BBO (α-BaB2O4) is an excellent negative uni-axial birefringent crystal. It has large birefringence coefficient and good transmission over a broad range, from 189nm to 3500nm. Unlike ß-BBO, α-BBO is not useful for NLO application due to the centric symmetry with its crystal structure.
α-BBO is excellent crystal in Glan Taylor, Glan Laser and Glan Thompson polarizer as well as walk-off beamsplitters, especially for high power and UV polarizers. This is due to their unique UV transparency, good mechanical properties and high damage threshold. Union Optic manufactures many Glan polarizers and beam displacers from high quality α-BBO crystals for UV and high power operations.