BBO Crystal is a one of the most important nonlinear optical crystals, beta-barium borate (ß-BaB2O4,ß-BBO) combines many outstanding features such as its high nonlinear optical coefficients, low group-velocity dispersion, broad transparency range (189–3500 nm) and high damage threshold. This unique combination ensures ß-BBO crystal a promising candidate for a wide range of nonlinear optical applications such as frequency converters and optical parametric oscillators. In the realm of quantum optics, ß-BBO crystal can be used to generate entangled photon pairs and ten-photon entanglement.