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A novel third-order nonlinear optical (NLO) crystal based on the organic borate carboxylate ester, with formula [Na4(H2O)5][B{O2CCH(O)Ph}2]4(abbreviated as LMBNa), has been prepared in aqueous solution. Single-crystal X-ray diffraction analysis reveals that the boron atom is coordinated with two l-mandelic ligands by alkoxide and carboxylate groups, forming the [B{OOCCH(O)C6H5}]−anion. The sodium cation supports its structural framework of borate anions in the formation of a cross-linked structure. Bulk single crystals of LMBNa were grown from acetonitrile/water by the temperature lowering method. Studies of its third-order NLO properties using a Z-scan technique demonstrate that the LMBNa crystal possesses a strong saturable absorption and the self-focusing effect. Its second molecular hyperpolarizability (γ) at 532 nm is calculated to be (3.9 ± 0.2) × 10−31esu. Furthermore, dielectric experiments reveal that LMBNa has a quite low-dielectric constant (∼3.43) and shows an anisotropy of frequency dependence along the different crystallographic directions. Such dielectric behaviors will favor the application of the LMBNa crystal under the electric field. All the results indicate that LMBNa might be a potential candidate material for the third-order NLO applications. [ABSTRACT FROM AUTHOR]

It is challenging to explore deep-ultraviolet (deep-UV) nonlinear optical (NLO) materials that can achieve a subtle balance between deep-UV transparency and high NLO activity. Known deep-UV NLO materials are almost exclusively limited to borates, except few newly discovered phosphates despite their small NLO activities. Here we report two asymmetric phosphates, RbBa2(PO3)5 (I) and Rb2Ba3(P2O7)2 (II), which feature [PO3]∞ chains and [P2O7]4- dimers formed by condensation of [PO4]3- units, respectively. Remarkably, I achieves the desired balance, with the shortest deep-UV absorption edge at 163 nm and the largest NLO activity of 1.4 × KDP (KH2PO4) in deep-UV NLO phosphates. According to first-principles calculations, the enhanced macroscopic SHG response of I can be attributed to the [PO3]∞ chains which exhibit significantly larger microscopic SHG coefficients as compared with the [P2O7]4- dimers. [ABSTRACT FROM AUTHOR]

A new noncentrosymmetric borate CsZn2B3O7 was synthesized by the solid-state reaction techniques. The crystals were obtained by flux method and are of block shape without layering tendency. Single-crystal X-ray diffraction analysis reveals that the crystal structure is composed of [Zn2BO5]8 two-dimensional layers that are bridged by [B3O6]3- groups to form a three-dimensional framework with one-dimensional channels occupied by Cs+ cations along the a and c axes. Thermal analysis indicates that CsZn2B3O7 melts incongruently. UV-visible-near-IR diffuse reflectance spectrum gives a short absorption edge at 218 nm. CsZn2B3O7 is phase-matchable, with a powder second-harmonic generation (SHG) efficiency of 1.5 × KDP (KDP, potassium dihydrogen phosphate) at 1064 nm, based on the Kurtz-Perry method. These results show that CsZn2B3O7 may have prospects as a UV nonlinear optical material. Interestingly, the SHG efficiency of CsZn2B3O7 is about twice that of ?-KBe2B3O7, a structurally analogous alkaline and alkaline earth borate. First-principles calculations combined with atom-cutting analysis reveal that the ZnO4 tetrhedral groups in CsZn2B3O7 account for the SHG enhancement. [ABSTRACT FROM AUTHOR]