Nichtlineare optische Materialien In der Zuschrift auf S. 6598 beschreiben K. Ok, G. Zou et al. die Synthese des Fluoridsulfats CsSbF2SO4 aus KTiOPO4 durch chemische Substitution. CsSbF2SO4 zeichnet sich durch eine ausgeprägte Frequenzverdopplung aus.

Discovering new functional genes, designing perfect crystal structures, and developing high‐performance materials are the goals being pursued by scientists. Herein, the first antimony pyrophosphate, K2Sb(P2O7)F, possessing an optimal layered structure, is reported, where the perfect structural arrangement induces excellent optical properties. K2Sb(P2O7)F not only displays a sharply enhanced birefringence (0.157@546 nm) compared to the existing phosphate optical materials, but also exhibits a strong second‐harmonic generation response (4.0×KDP). Remarkably, a new bifunctional gene, the square‐pyramidal SbO4F group, was discovered, and a unique two‐dimensional arrangement of Cairo pentagonal tiling units was observed in inorganic compounds for the first time.

A promising UV nonlinear optical material, beryllium-free nitrate Ba2NO3(OH)3, has been synthesized via modified high-temperature solid state reactions in a self-made high-pressure apparatus which exhibits a perfect balance of a large second harmonic generation coefficient, an appropriate birefringence for phase matching, a short UV absorption cutoff edge and physicochemical stabilities.

Discovering novel sulfate optical materials with strong second-harmonic generation (SHG) and large birefringence is confronted by a great challenge attributed to the intrinsically weak polarizability and optical anisotropy of tetrahedral SO 4 groups. Herein, two superior-performing sulfate optical materials, namely, noncentrosymmetric Hg 3 O 2 SO 4 and centrosymmetric CsHgClSO 4 • H 2 O, have been successfully synthesized through the introduction of a highly polarizable d 10 metal cation, Hg 2 + . The unique component layers in the reported compounds, [Hg 3 O 2 SO 4 ] ∞ layers in Hg 3 O 2 SO 4 and [HgClSO 4 (H 2 O)] À ∞ layers in CsHgClSO 4 • H 2 O, induce enlarged birefringence in each sulfate. Remarkably, Hg 3 O 2 SO 4 exhibits a very large SHG response (14 times that of KH 2 PO 4 ), which is the strongest efficiency among all the reported nonlinear optical sulfates. Detailed theoretical calculations confirm that the employment of highly polarizable Hg 2 + is an effective strategy to design superior optical materials with large birefringence and strong SHG response.

Developing effective strategies to design novel, excellent birefringent materials has become an emerging challenge. Herein, we report a new UV nitrate birefringent material, CsHgNO3Cl2, which is an analogue of the known UV carbonate nonlinear optical crystal KCaCO3F. In CsHgNO3Cl2, a perfect layered structure was produced owing to the alliance of a planar π-conjugated anion NO3 – and highly electropolarized Hg2+ cation. The optimized layered structure that is beneficial in enlarging the optical anisotropy induced a large birefringence (Δn = 0.145@546 nm) for CsHgNO3Cl2, even superior to that of the well-known commercial birefringent material α-BBO in the UV region. The strategy that the optimization of planar functional group arrangement is able to boost birefringence is expected to guide the development of high-performance birefringent materials in the future, especially in the field of UV.