Gang Zhang

A New Mixed Halide, Cs2HgI2Cl2: Molecular Engineering for a New Nonlinear Optical Material in the Infrared Region

A new mixed halide, Cs(2)HgI(2)Cl(2), which contains the highly polar tetrahedron of anion (HgI(2)Cl(2))(2-), has been designed and synthesized by reaction in solution. In its single crystal, the isolated (HgCl(2)I(2))(2-) groups are arranged to form chains. The chains are then further connected into a three-dimensional framework through the Cs atoms that occupy the empty spaces surrounded by halide atoms. All the polar (HgCl(2)I(2))(2-) groups align in such a way that gives a net polarization, leading it to show a phase matchable second harmonic generation (SHG) effect as strong as that of KH(2)PO(4) (KDP) based on the powder SHG measurement. It also displays excellent transparency in the range of 0.4-41 μm with relatively high thermal stability. A preliminary measurement indicates that its laser-induced damage threshold is about 83 MW/cm(2), about twice that of AgGaS(2). This study demonstrates that Cs(2)HgI(2)Cl(2) is a promising nonlinear optical material in the infrared region.

NaSb3F10: A new second-order nonlinear optical crystal to be used in the IR region with very high laser damage threshod

This paper reports the second-order nonlinear optical (NLO) property of NaSb3F10, a potential new NLO material in the infrared region. The compound exhibits a phase-matchable second harmonic generation (SHG) efficiency of about 3.2 times that of KH2PO4 based on the powder SHG measurement. A measurement indicates that its laser damage threshold is as high as about 1.3 GW/cm2, which is much higher than all those IR NLO crystals reported in the literature. It also shows excellent transparency in the range of 0.25–7.8 μm with relativity high thermal stability. Single crystal of the size 12×10×8 mm3 has been grown in aqueous solution by a slow evaporation technique.

Mercury Bromide (HgBr2): A promising nonlinear optical material in IR region with a high laser damage threshold

Nonlinear optical (NLO) crystals have played a key role in laser technology, and the existing materials for the IR range showed relatively low laser damage threshold in common. A NLO material HgBr2 is presented here. It shows a powder second harmonic generation about ten times as large as that of KH2PO4, a wide transparency in whole mid-IR region (from 2.5 to 25 μm), and a good stability to the environment. Most importantly it exhibits a high laser damage threshold of about 0.3 GW/cm2. Therefore, it is believed that HgBr2 is a promising candidate for NLO materials in the IR region.

A facile and clean synthesis of pure bismuth sulfide iodide crystals

Pure BiSI (bismuth sulfide iodide) crystals were synthesized directly from the reaction of BiCl3, (NH2)2CS, and I2 through a mild hydrothermal process (160°C for 30 h) after simple filtration and washing. The as-prepared crystals were characterized by XRD, IR, XPS, and SEM. The band gap of the product was calculated to be about 1.8 eV from UV-Vis-NIR results. A possible reaction mechanism was proposed.