Investigations on certain organic single crystalline materials for nonlinear optical and terahertz applications

Abstract

In the last few decades, there has been incessant quest worldwide to design and synthesize the hydrogen bonded novel organic nonlinear optical (NLO) materials for the variety of applications such as frequency conversion, optical switching, optical data storage, linear and quadratic electro-optic, optical power limiting, terahertz wave (THz) generation and detection etc. The organic NLO materials, in particular, could be synthesized through solution route wherein the organic molecules, due to their flexible nature, could crystallize with either centrosymmetric (CS) or non-centrosymmetric (NCS) crystal structure. In general, the applications such as second harmonic generation, linear electrooptic, terahertz generation etc. depend mainly on non-centrosymmetric crystals (lack inversion center and optically anisotropic), optical switching, quadratic electro-optic, optical power limiting etc. depend on centrosymmetric crystals (possess inversion center and optically isotropic). In this direction, in the present work, certain benzoates and phenol based novel NLO materials namely, Morpholinium 2-chloro-4-nitrobenzoate (M2C4N), 4-Dimethylamino)benzaldehyde 4-nitrophenol (4DMAB4NP), Pyrrolidin-1-ium 2-chloro-4-nitrobenzoate 2-chloro-4-nitrobenzoic acid (PCNCN) and Pyrrolinin- 1-ium-2-carboxylate 4-hydroxybenzoic acid (P2C4HBA) were identified and synthesized, crystals were grown and their physico-chemical and nonlinear optical properties were studied. While M2C4N and P2C4HBA crystallized in orthorhombic system with noncentrosymmetric space group P212121 whereas PCNCN and 4DMAB4NP crystallized in monoclinic system with centrosymmetric space group of P21/c space group. Among these, the crystal structure of M2C4N alone was reported by Ishida et al. newline