R. Nagalakshmi

Studies on crystal growth, vibrational and optical properties of organic nonlinear optical crystal: p-Aminoazobenzene

p-Aminoazobenzene (p-AAZB), an organic nonlinear optical (NLO) crystal having good optical quality has been grown by slow evaporation solution technique using ethanol as a solvent. Solubility studies were performed at different temperatures. The structural characterization of the grown crystals was carried out by X-ray diffraction. Group theoretical analysis was carried out to calculate the number of modes of vibration. The lowering of the wave numbers of azo group suggests the existence of strong intermolecular N-H...H hydrogen bonding. This has been analysed based on the vibrational spectral features. Optical absorption studies show the effective transmission in the entire UV-vis region. The second harmonic generation results show the suitability of this material for NLO applications.

Crystal growth and characterization of N-hydroxyphthalimide (C8H5NO3) crystal.

Single crystals of N-hydroxyphthalimide (NHPH) were obtained from saturated aqueous solutions of methanol and acetonitrile by slow cooling method. The grown crystals were bright and transparent. From the crystal structure analysis it can be inferred that the crystal belongs to monoclinic system. The grown crystals were subjected to FTIR analysis for vibrational assignments. The optical transmission spectra showed excellent transmittance from 200 to 1100 nm. The thermal stability and thermal decomposition of NHPH crystal have been investigated by means of thermogravimetric analysis and differential thermal analysis.

Effect of doping an organic molecule ligand on TGS single crystals

Good quality single crystals of thiourea-doped triglycinesulphate (TuTGS) a new semiorganic nonlinear optical (NLO) crystal has been successfully grown from aqueous solution by slow evaporation method. The solubilities under various solvents in different proportions have been studied. The structural characterization of the grown crystals was carried out by X-ray diffraction. The grown crystals were subjected to FTIR and Raman analyses for vibrational assignments. The optical absorption coefficient alpha was analysed and interpreted to be allowed in the direct transition. The values of allowed direct energy gap (Eg) for undoped and doped crystals were calculated. It was found that Eg values were decreased with organic molecule doping. The powder technique of Kurtz and Perry confirm the NLO property of the grown crystal.

Probes on l-lysine monohydrochloride dihydrate: A semiorganic nonlinear optical crystal

L-Lysine monohydrochloride dihydrate (LLMHCl), a semiorganic potential nonlinear optically active crystal possessing large hyperpolarizability and which belongs to noncentrosymmetry class has been grown and studied. The XRD analysis shows that it belongs to the auspicious symmetric space group P2(1) with two molecules in the asymmetric unit. FTIR and FT Raman of the title crystal have been studied at room temperature. The polarization light and oriented single crystals are used to assign the lines observed in the Raman spectra of the studied material. The vibrational spectral characterization has been carried out and interpreted in the light of crystal structure data and factor group analysis. The second harmonic generation (SHG) measurements have allowed identifying the C2 space group symmetry of the compound corroborating very good propensity for green emission. The optical and mechanical responses have been studied with respect to UV visible and Vickers microhardness measurements.

Investigations on the physicochemical properties of the nonlinear optical crystal for blue green laser generation

Bisglycinehydrogenchloride (BGHC) an intriguing material for frequency conversion has been grown by slow evaporation solution growth technique at room temperature. Their structural, optical and physicochemical properties were characterized by X-ray powder diffraction, FTIR, Raman and UV-vis spectra. The title crystal has found to crystallize into noncentrosymmetric orthorhombic P2(1)2(1)2(1) space group. The material has a wide transparency in the entire visible region. It is found that the cutoff wavelength lies in the UV region. The mechanical response of the crystal has been studied using Vickers microhardness technique. The Kurtz powder second harmonic generation test shows that the compound is a prospective crystalline material for second order nonlinear optical application.

Polarized Raman and Hyperpolarizability studies of Hydroxyethylammonium (L) tartrate monohydrate for quadratic nonlinear optics

Hydroxyethylammonium (L) tartrate monohydrate was synthesized and crystals were grown using slow evaporation solution growth technique. Theoretical value of hyperpolarizability was calculated. Factor group analysis was carried out and is associated with the polarized Raman spectra.