Abstract This paper reports an organic crystal of a New Nonlinear Optical (NLO) material, L-Arginine Semicarbazone dihydrate (abbreviated as LASC). The crystals were grown by slow evaporation from an aqueous solution and crystallize in monoclinic form which is confirmed by single crystal x-ray diffraction analysis. The molecular weight of the grown crystal was estimated by mass spectrometry. The FTIR spectra con-firm the presence of the functional groups in the crystal while The UV–vis–NIR spectrum of grown crystal LASC reveals its transparent nature. The optical absorption in the grown crystal is almost negligible in the UV and visible spectral regions with the lower cut off wavelength at around 350 nm. Minimum amount of optical absorption suggests that the LASC crystal is highly transparent in the UV–visible spectral region and is useful for nonlinear optical applications. The second harmonic generation is confirmed by the emission of green light and its efficiency is found to be 0.51 times that of KDP crystal. The photoconductivity study shows that the grown crystal exhibit negative photoconductivity. Primary studies show that the grown crystals are appropriate for optoelectronics applications and Second Harmonic Generations. *Author for correspondence Indian Journal of Science and Technology, Vol 7(7), 1014–1017, July 2014 ISSN (Print) : 0974-6846 ISSN (Online) : 0974-5645 Studies on the Growth and Characterization of Organic L-Arginine Semicarbazone Dihydrate NLO Single Crystal B. Anitha 1 , S. Rathakrishnan 2 , R. Umamaheswari 3 and A. Joseph Arul Pragasam 3* 1 Department of Physics, SRR Engineering College, Chennai, Tamil Nadu, India 2 Department of Chemistry, SRR Engineering College, Chennai, Tamil Nadu, India 3 Department of Physics, Sathyabama University, Chennai, Tamil Nadu, India; drjosephsu@gmail.com 1. Introduction An optical communication device uses nonlinear opti- cal (NLO) materials. Inorganic, semiorganic and organic crystals have nonlinear optical property. Inorganic crys- tals like ADP, KDP are promising NLO crystals, but they have less nonlinear activity; also synthesizing crystals are somewhat diicult. Among organic, semiorganic and inorganic crys- tals, organic NLO materials are found to have large NLO coeicients. A series of organic NLO crystals with high nonlinear susceptibility have been synthesized and characterized 1–10 . If we take organic materials, Amino acid family crystals are found to have NLO materials. Amino acid contain dual functional group which has a carboxyl group (-COOH) and an amino group(-NH 2 ). hey exist as zwitter ions. Because of this reason, amino acids possess many unusual properties (Both physi- cal and chemical) which make researchers to think more on amino acids. he concrete form of all amino acids (except glycine) have Centrosymmetric space group which is the major criteria for NLO applica- tions. L-Arginine crystals such as L-Arginine Acetate, L-Arginine Phosphate and semi organic crystals such as L-Arginine Phosphate, L-Arginine Di Phosphate, L-Arginine hydrochloride etc. 11–14 . In this paper, new L-Arginine Semicarbazone dihydrate NLO single crys- tal is grown by slow solvent evaporation technique is reported. he grown crystal has been given for various characterizations. Keywords: FTIR, NLO, Optical Absorption, Photoconductivity Study, Solution Growth