This report presents the synthesis, growth, crystal structure determination, and hyperpolarizability studies of l-argininium-4-nitro phenolate monohydrate (LARP) single crystals for the first time in the literature. Density functional theory at the B3LYP/HF6-31G (d,p) level has been used to compute the first-order hyperpolarizabilty of LARP. The second harmonic generation efficiency of the title compound is very high. Planar molecular structure and better conditions for electron conjugation and charge transfer result in larger values of β for this title crystal.

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A new non linear optical material, Bis-Glycine Hydro bromide (BGHB), has been synthesized. Single crystals of BGHB have been grown successfully by slow evaporation method. The solubility of the material was measured in various solvents such as ethanol, acetone and water. It was found to have extremely low solubility in ethanol and acetone. The grown crystals were characterized by recording the powder diffraction and identifying the diffracting planes. Using single crystal diffractometer the morphology of BGHB crystal was identified. Fourier transform infrared (FTIR) spectroscopic studies, optical behavior such as UV-visible-NIR absorption, Thermogravimetic (TG) and differential scanning calorimetric (DSC) analyses have been performed to show that BGHB is thermally stable up to 168.5 o C and there is no phase transition and decomposition till 168.5 o C. Anisotropy in the hardness behavior has been observed while measuring at different crystal planes by Vicker hardness test.

The synthesis and crystal structure of rhodamine 590 acid phthalate (RhAP) have been reported. This novel solid-state rhodamine derivative not only has a longer fluorescence lifetime compared to rhodamine solid-state matrixes where emission is quenched but also possesses strong nonlinear optical characteristics. The static and dynamic first- and second-order hyperpolarizabilities were calculated using the time-dependent density functional theory at the B3LYP/6-31+G* level. The computed static values of β and γ of RhAP by the X-ray diffraction (XRD) structure were 31.9 × 10 –30 and 199.0 × 10 –36 esu, respectively. These values were about 62 times larger than the corresponding values in urea, an already well-known nonlinear optical material. The second-order hyperpolarizability of the compound was determined experimentally by measuring the two-photon absorption cross section using intensity-modulated light fields. The reported compound, excitable at near-infrared, exhibited frequency upconversion with the two-photon absorption coefficient enhanced by two orders of magnitude compared to that of the dye solution. Hosting the dye in the solid, at high concentrations, exploits the nonlinearity of the dye itself as well as results in significant excitonic effects including formation of broad exciton band and superradiance.

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