High-quality crystals of BGSe (BaGa4Se7) is the selenide analogue of the chalcogenide compound BaGa4S7, whose acentric orthorhombic structure was identified in 1983 and the IR NLO effect was reported in 2009, is a newly developed IR NLO crystal. It was obtained via the Bridgman–Stockbarger technique. This crystal exhibits high transmittance over the wide range of 0.47–18 μm, except for an absorption peak at around 15 μm.