High Temperature form BBO ( a -BaB 2 O 4 ) is a negative uniaxial crystal. It has large birefringence over the broad transparent range from 189 nm to 3500 nm. The physical, chemical, thermal and optical properties of a-BBO crystal are similar to those of b-BBO. However, the nonlinear optical properties of a-BBO crystal is vanished due to the centric symmetry with its crystal structure. It is not recommended to use for NLO processes.

a -BBO is an excellent crystal to replace Calcite, TiO 2 , and LiNbO 3 , etc. in Glan-Taylor and Glan-Thompson polarizers as well as walk-off beam splitters, especially for high power and UV polarizer, due to its unique UV transparency, good mechanical properties and high damage threshold.Claser manufactures and supplies Glan-Laser, Glan-Taylor, Glan-Thompson Polarizers and other beam displacers from high quality a -BBO crystals to replace Calcite in many applications, especially in UV and high power operations.