L-Arginine diiodate (L-Arg center dot 2HIO(3)) a new semi-organic nonlinear optical (NLO) material was synthesized by the standard method. The synthesized material was purified by repeated recrystallization process. Single crystals were grown by the slow evaporation and slow cooling methods. Crystal with excellent transparency were grown with maximum size of 20 mm x 10 mm x 10 mm and the grown crystals were characterized by single crystal XRD, FT-IR, FT-Raman, TGA-DTA, hardness study, and UV-vis-NIR studies. The second harmonic generation (SHG) of the material was confirmed using Nd:YAG. The L-Arg center dot 2HIO(3) has NLO efficiency 1.3 times higher than the KDP crystal. Laser damage threshold studies revealed that the grown crystals possess high damage threshold values. (c) 2007 Published by Elsevier B.V.