A comprehensive survey on nonlinear optical phosphates: Role of multicoordinate groups

Ultraviolet (UV) and deep ultraviolet (DUV) nonlinear optical (NLO) crystals, which could respectively generate UV and DUV lasers with high photon flux, are of great importance to the laser technologies. Phosphates possess short cutoff edges and then are widely regarded as promising UV and DUV NLO candidates. In this review, we aim to present the development of NLO phosphates from the perspective of structure-property relationships. Therefore, we focus on the structural motifs in NLO phosphates, including diverse P-O groups and other multicoordinate anionic groups, and uncover their impact on the second harmonic generation (SHG) effect, cutoff edge and phase-matching (PM) output. Meanwhile, it is proposed that the integration of [LiO4] or [MgO4]/[MgO5] groups into the phosphates might be an effective strategy to achieve the good balance between SHG effect and cutoff edge.