Growth, optical and electrical properties of L-lysine-L-tartaric acid (LLLT) nonlinear optical single crystals for electro-optic applications N. Y. Maharani 1,2 • I. Vetha Potheher 3 • M. Vimalan 4 • A. Cyrac Peter 5 Received: 21 June 2016 / Accepted: 19 July 2016 Ó Springer Science+Business Media New York 2016 Abstract Optically good quality single crystals of amino acid based organic L-lysine-L-tartaric acid (LLLT) have been grown by slow solvent evaporation technique at room temperature. The single crystal X-ray diffraction study confirms the grown crystal belongs to the noncentrosym- metric space group P2 1 . The presence of various functional groups in the grown crystal has been identified by Fourier transform infrared spectroscopy. Optical transmission studies show that the grown crystal has a fairly wide transparency range which is suitable for nonlinear optical applications and the band gap energy of the sample is found to be 5.39 eV. Thermogravimetric and differential thermal analyses reveal that the crystal is thermally stable up to 201 °C. The second harmonic generation conversion efficiency of LLLT is closely three times that of potassium dihydrogen phosphate. The laser induced sur- face damage threshold for the grown crystal has been found to be 3.46 GW/cm 2 . Normal indentation size effect was confirmed from micro hardness studies. Electrical con- ductivity behavior of the grown crystal was studied from the dielectric constant and dielectric loss measurement as a function of frequency with different temperatures. Photo- conductivity studies of LLLT reveal its negative photo- conducting nature. Also the ac and dc conductivity are measured and the results are discussed for the first time. 1 Introduction Recently, nonlinear optical (NLO) materials have attracted a great deal of attention because of their potential appli- cation in optical devices such as optical switches, optical modulators, electro-optical devices, etc. [1–3]. Inorganic materials were the first to be used for these applications due to their high melting point, high mechanical strength and high degree of chemical inertness, but these materials possess poor optical nonlinearity. Organic materials have subsequently produced a high degree of optical non-lin- earity than inorganic materials. A major drawback of crystalline organic NLO materials is poor mechanical and thermal stability. These crystals are mostly difficult to grow in large size single crystals with optically transparent [4–6]. The primary approach consists of using the intra-molecular salts for the growth of single crystals with higher nonlinear optical susceptibilities. The electron–phonon contribution playing crucial role in the parametrical nonlinear optical susceptibilities, which was confirmed by the polarized Raman spectra of L-lysine monohydrochloride dehydrate (LLMHCL) single crystal [7]. Recently, amino acids and their complexes belong to the family of organic materials have overcome the most of the drawbacks, which are potential candidate materials for NLO applications [8, 9]. However, the presence of Zwitter ions influences the & M. Vimalan myresearch1121@gmail.com & A. Cyrac Peter cyrac.peter@gmail.com 1 Department of Physics, Gopalan College of Engineering and Mamangement, Bangalore, India 2 Research and Development Centre, Barathiyar University, Coimbatore, India 3 Department of Physics, Bharathidasan Institute of Technology (BIT) Campus, Anna University, Tiruchirappalli, India 4 Department of Physics, Thirumalai Engineering College, Kilambi, Kancheepuram, India 5 Department of Physics, Raja Doraisingam Government Arts College, Sivagangai, India 123 J Mater Sci: Mater Electron DOI 10.1007/s10854-016-5406-4