Beta barium borate (BaB2O4, BBO) crystal
MolTech

ß-Barium Borate (ß-BaB2O4 or BBO) is an excellent optical non-linear crystal recently developed. It exhibits broad phase matching range, high non-linearity (about 6 times more than that of KDP), high optical damage threshold, good mechanical and temperature stability. This trigonal uniaxial crystal possesses wide transparency range from 0.19 to 3.3 µm. Its useful transmission range (<5%/cm) is 0.21 to 2.1 µm and it has been demonstrated to be efficient for the generation of second harmonic radiation down to about 0.21 µm. It is also useful for broadly tunable optical parametric oscillators (OPOs) and amplifiers (OPAs). Autocorrelation applications may be performed down to 0.19um. Its exceptional IR transmission and wide thermal acceptance bandwidth allow high average power OPO/OPA operation, with minimal heating from long wavelength idler radiation.
BBO's relatively narrow angular acceptance bandwidth (especially in the UV) may limit its usefulness in certain applications involving lasers with less than diffraction limited beam quality. Its mild hygroscopicity should not limit its usefulness in most circumstances.