Explorations of New Second-Order Nonlinear Optical Materials in the KI-MII -IV-O Systems

Explorations of new second-order nonlinear optical (NLO) materials in the KI-MII -IV-O systems led to four novel mixed metal iodates, namely, K2M(IO3)4(H2O)2 (M = Mn, Co, Zn, Mg). The four compounds are isostructural and crystallize in space group I2 which is in the chiral and polar crystal class 2. Their structure features zero-dimensional {M(IO3)4(H2O)2}2− anions that are separated by K+ cations. The M(II) centers are ligated by two aqua ligands in trans fashion and four monodentate iodate anions. The K+ cation is eight-coordinated by two iodate anions in bidentate chelating fashion and four other iodates in a unidentate fashion. Second harmonic generation (SHG) measurements indicate that K2Zn(IO3)4(H2O)2 and K2Mg(IO3)4(H2O)2 display moderate SHG responses that are approximately 2.3 and 1.4 times of KH2PO4 (KDP), respectively, and they are also phase-matchable. The SHG response of K2Co(IO3)4(H2O)2 is much weaker (about 0.3×KDP), and no obvious SHG signal was detected for K2Mn(IO3)4(H2O)2. Results of optical property calculations for the Zn and Mg phases revealed SHG responses of approximately 5.3 and 4.7 times of KDP, respectively, the order of Zn > Mg is in good agreement with the experiment data.

对KI-MII-IV-O系统中新型二阶非线性光学(NLO)材料的探索，衍生出四种新型的混合金属碘酸盐，分别为K2M(IO3)4(H2O)2（M = Mn, Co, Zn, Mg）。这四种化合物结构相同，以空间群I2结晶，属于手性和极性晶体类别2。其结构特征为零维的{M(IO3)4(H2O)2}2−阴离子，由K+阳离子分隔。M(II)中心以反式通过两个水合配体和四个单齿碘酸根阴离子配位。K+阳离子以双齿螯合方式由两个碘酸根阴离子配位，并与其他四个碘酸根以单齿配位。二次谐波产生(SHG)测量表明，K2Zn(IO3)4(H2O)2和K2Mg(IO3)4(H2O)2表现出适度的SHG响应，分别为KH2PO4 (KDP)的2.3倍和1.4倍，并且它们也是相位匹配的。K2Co(IO3)4(H2O)2的SHG响应相对较弱（约为0.3×KDP），而K2Mn(IO3)4(H2O)2未检测到明显的SHG信号。Zn和Mg相的光学性质计算结果表明，SHG响应分别约为KDP的5.3倍和4.7倍，Zn > Mg的顺序与实验数据良好一致。