Single crystals of zinc magnesium tetra thiocyanate [ZnMg(SCN) 4 ], a bimetallic thiocyanate complex, were grown by slow evaporation solution growth technique at room temperature. The bright, transparent and colourless crystals have well defined faces. The grown crystals were characterized through elemental analysis, powder X-ray diffraction (XRD), thermogravimetric (TG) and differential thermal analysis (DTA), differential scanning calorimetric analysis (DSC), Fourier Transform Infra red (FTIR) and Optical studies. The elemental analysis confirms the stoichiometry of the synthesized crystals. The compound crystallizes under monoclinic structure with lattice parameters a = 10.055 Å, b = 7.44 Å, c = 6.00 Å and β = 90.113°. The TGA indicates 25 % weight loss at 205°C from which the decomposition pattern is formulated. The DSC study indicates that the crystal undergoes only first order phase transitions. The FTIR spectrum indicates among others the presence of metal-nitrogen and metal-sulphur bonds thus confirming the formation of the complex. The second harmonic-generation (SHG) was confirmed by the emission of green radiation using Nd: YAG laser.

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Effect of Rhodamine B dye on the growth and properties of L-Alanine Thiourea Bulk single crystals has been reported. The cell parameters and crystallinity of pure and dye admixtured LATU crystals were confirmed by single crystal, powder X-ray diffraction and high resolution X-ray diffraction analyses. The functional groups present in the crystals were confirmed by FTIR analysis. The UV-vis-NIR transmission studies show the optical transparency in the entire visible region of Rhodamine B dye admixtured LATU crystal. The laser damage threshold value significantly enhanced for dye admixtured crystal in comparison with pure LATU crystal. The crystals were further subjected to other important characterizations such as dielectric measurement, micro hardness, thermal and NLO studies. The relative SHG efficiency of Rhodamine B dye admixtured LATU crystal was found to be 1.46 times higher than that of pure LATU crystal.

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Nonlinear optical (NLO) crystals are classified into organic, inorganic and semi organic crystals and these crystals are used in the fields of optical communication, optical computing, frequency doubling, optical data processing and opto electronics. In this work an organic NLO crystal namely DMU crystal was prepared. Slow evaporation technique was adopted to grow the single crystals of DMU after the growth period of 35 days. The harvested crystals have been subjected to various characterization techniques like XRD, FTIR, FT-Raman, TG/DTA, SHG, EDAX, impedance, optical and Z-scan studies. From the studies, is observed that DMU crystal has orthorhombic structure and it has the melting point at 105 o C and has the decomposition point at 275 o C. The relative SHG efficiency of DMU crystal was found to be more than one and third order NLO parameters were evaluated. The optical band gap of DMU crystal was found to be 5.008 eV.The results from various studies were analyzed.