Crystal Growth and Characterization of a New NLO Material: p-Toluidine p-Toluenesulfonate

Single crystals of p-Toluidine p-Toluenesulfonate (PTPT), an organic nonlinear optical (NLO) material, have been grown by slow evaporation method at room temperature using ethanol as solvent. The crystal system was confirmed from the single crystal X-ray diffraction analysis. The functional groups were identified using FTIR spectroscopy. UV-Vis-NIR spectrum showed that the UV cut-off wavelength of PTPT occurs at 295 nm and it has insignificant absorption in the wavelength region of 532–800？nm. The SHG efficiency of PTPT was measured by employing Kurtz and Perry powder technique using a Q-switched mode locked Nd: YAG laser emitting 1064？nm for the first time and it was found to be 52% of standard KDP. Thermal and mechanical properties of PTPT were examined by TG/DTA and Vickers microhardness test, respectively. 1. Introduction Materials with large nonlinear optical susceptibilities are of current interest in the area of harmonic generation and optical modulation. In recent years, some polar organic crystals, which form a noncentrosymmetric structure which exhibit second-order nonlinear optical properties that far surpassed those of the conventional materials, have led to the synthesis and evaluation of a wide range of potentially useful solids [1]. Materials showing high optical nonlinearity have potential applications in signal transmission, data storage, optical switching, laser printing, displays, inflorescence, photolithography, remote sensing, chemical and biological species detection, high resolution spectroscopy, medical diagnosis, and underwater monitoring and communication [2]. Different types of molecular and bulk materials have been examined for nonlinear optical properties. Organic nonlinear materials are attracting a great deal of attention, as they have large optical susceptibilities, inherent ultrafast response times, and high optical thresholds for laser power as compared with inorganic materials [3]. Organic molecules with significant nonlinear optical activity generally consist of a π-electron conjugated structure. The conjugated π-electron moiety provides a pathway for the entire length of conjugation under the perturbation of an external electric field. Fictionalization of both ends of the π-bond systems with appropriate electron donor and acceptor group can increase the asymmetric electronic distribution in either or both the ground and excited states, thus leading to an increased optical nonlinearity [4–7]. In the present investigation, we report the growth and characterization especially the SHG efficiency of p-Toluidine