Alpha-Barium Borate (α-BaB2O4, α-BBO) is a negative uniaxial crystal which has large birefringence over a broad transparent range of 190 nm-3500 nm. α-BBO is an excellent crystal especially in UV and high power applications. The physical, chemical, thermal and optical properties of α-BBO crystal are similar to those of β-BBO. However, the nonlinear optical properties of α-BBO crystal are nonexistent due to the centrical symmetry of its crystal structure. α-BBO crystal is recommended for NLO processes.