Photonics and Optoelectronics (P&O) Volume 3, 2014 www.jpo‐journal.org doi: 10.14355/jpo.2014.0301.02 9 Optical Studies on L ‐ Tartaric acid and L ‐ Prolinium Tartrate K. Moovendaran 1 , V.Jayaramakrishnan 2 , S. Natarajan *1 1 School of Physics, Madurai Kamaraj University, Madurai‐625 021, India 2 Department of Physics, PSG College of Arts and Science, Coimbatore ‐ 641 014, India 1 moovendaran@gmail.com; 2 jayaram.si@gmail.com; *1 s_natarajan50@yahoo.com Received 15 June 2013; Revised 7 August 2013; Accepted 21 August 2013; Published January 2014 © 2014 Science and Engineering Publishing Company Abstract Bulk‐size single crystals of the nonlinear optical (NLO) materials: L‐tartaric acid (LTA) and L‐prolinium tartrate (LPT) were grown from aqueous solution using a home made crystal growth setup. Characterization of the crystals was investigated using single crystal X‐ray diffraction. UV‐ vis‐NIR spectra showed that the crystals have excellent transparency in the visible and infrared regions. Tentative assignments were made for the IR absorption peaks. The birefringence of the crystals was measured in the visible region and it was found to be varying with wavelength. Photoluminescence excitation studies showed that the emission occurred at 397 and 375 nm respectively, for LTA and LPT. The second harmonic generation (SHG) conversion efficiency of the powder samples of the crystals were measured as about 40% and 95% respectively, compared to that of the standard KDP crystals. Keywords L‐Tartaric Acid; L‐Prolinium Tartrate; MKN Setup; UV‐vis‐NIR; IR Spectra; Birefringence; SHG Introduction In recent years, several studies dealing with organic, inorganic and semiorganic materials for nonlinear optics (NLO) have been reported, due to the increasing need for cheap and easily processable materials for applications in photonics. Among these, organic nonlinear materials will be the key elements for future photonic technologies. A number of such materials have been reported in literature for their applications as NLO materials [Pal, Kar, Bocelli and Rigi, 2003, Natarajan, Martin Britto Dhas and Ramachandran, 2006]. L‐ Tartaric acid (LTA) and L‐Prolinium tartrate (LPT) are good organic nonlinear optical materials. Reports are already available on the growth of the single crystals of LTA using slow evaporation, hanging seed, submerged seed solution techniques and Sankaranarayanan‐ Ramasamy method [Suresh and Arivuoli, 2011, Martin Britto Dhas, Suresh, Bhagavannarayana and Natarajan, 2007, Ramesh Kumar, Gunaseelan, Kumararaman, Baghavannarayana and Sagayaraj, 2011]. Recently, the unidirectional growth of LTA using a home made crystal growth setup (MKN setup) and its characterization were reported from our laboratory [Moovendaran and Natarajan, 2013]. Crystals of LPT were grown using submerged seed solution method by Martin Britto Dhas and Natarajan (2007), from our laboratory. The present communication deals with the following: (i) the growth of bulk‐ size single crystals of LTA and LPT using the MKN setup, (ii) their characterization using single crystal X‐ray diffraction, UV‐vis‐NIR and infrared (IR) spectroscopic methods, (iii) measurements of birefringence and second harmonic generation (SHG) efficiencies and (iv) photoluminescence (PL) studies. Crystal Growth Experiments A new setup was designed in our laboratory to conduct several crystal growth experiments simultaneously [Moovendaran, Kalyana Sundar and Natarajan, 2011]. The home made setup (named as MKN setup) is made up of two large tanks and consists of several ampoules, dimmerstat, temperature controller, heating coil and thermometer. Constant temperature and uniform temperature gradient were maintained to increase the growth rate and quality of the crystal grown. The details of this setup and the growth of LTA single crystal have been reported elsewhere [Moovendaran and Natarajan, 2013]. LPT was synthesized using L‐proline and L‐tartaric acid taken in the equimolar ratio. The reactants were thoroughly dissolved in distilled water using a