Structural, optical and electrical characteristics of a new NLO crystal E.D. D’silva a,n , G. Krishna Podagatlapalli b , S. Venugopal Rao b , S.M. Dharmaprakash a a Department of Studies in Physics, Mangalore University, Mangalagangotri, Mangalore 574199, India b Advanced Centre of Research in High Energy Materials (ACRHEM), University of Hyderabad, Hyderabad 500046, India article info Article history: Received 21 October 2011 Received in revised form 23 December 2011 Accepted 12 January 2012 Available online 4 February 2012 Keywords: Nonlinear optical material Third-harmonic generation Laser damage threshold abstract A new nonlinear optical (NLO) organic crystal 1-[4-({(E)-[4-(methylsulfanyl)phenyl]methylidene}ami- no)phenyl]ethanone (MMP) has been grown by slow evaporation technique at ambient temperature. The crystal structure of MMP was determined by single crystal X-ray diffraction. MMP crystallizes in non-centrosymmetric monoclinic system with space group P2 1 . The FT-IR spectrum recorded for new crystal confirmed the presence of various functional groups in the material. MMP was found to be thermally stable up to 300 1C. The grown crystal was optically transparent in the wavelength range of 400–1100 nm. The second harmonic generation (SHG) efficiency of the crystal was measured by the classical powder technique using Nd:YAG laser and was found to be 4.13 times more efficient than reference material, urea. Third order nonlinear parameters were measured by employing the Z-scan technique. The laser damage threshold for MMP crystal was determined to be 4.26 GW/cm 2 . The Brewster angle technique was employed to measure the refractive index of the crystal and the values for green and red wavelengths were found to be 1.35 and 1.33, respectively. The dielectric and electrical measurements were carried out to study the different polarization mechanisms and conductivity of the crystal. & 2012 Elsevier Ltd. All rights reserved. 1. Introduction The development of optical devices, such as photonic inte- grated circuitry, depends strongly on the design of highly efficient nonlinear optical (NLO) materials. Among such NLO materials, organic materials are shown to be superior to their inorganic counterparts in terms of synthesis, crystal fabrication, potential to create large devices and much faster optical nonlinearities [1,2]. Various organic single crystals like stilbazolium crystals [2], OH1 [3] and crystals of other charge transfer complexes [4], such as chalcones [5], have been attractive for frequency conversion, integrated circuitry and terahertz (THz) applications [6]. Organic derivatives having polarizable electrons (e.g., p-electrons) spread over a large distance with various combinations of terminal electron donor and/or acceptor groups have been the objective of recent research, particularly in view of their large molecular hyperpolarizabilities and good crystallizability [7–11], which may lead to a wide range of applications in integrated optics (second harmonic generation (SHG), frequency mixing, electro-optic mod- ulation, parametric effects, etc.) [12,13]. The design and synthesis of organic molecules exhibiting second-order nonlinear optical (NLO) properties has also been motivated by their tremendous potential for application in optical communications, optical com- puting, data storage, dynamic holography, harmonic generators, frequency mixing and optical switching [10,14]. In this perspec- tive the synthesis, growth and various characterization studies of crystal (MMP), possessing p-conjugated donor–p–acceptor system is imperative to explore its possible applications in non- linear optics. The nonlinearity in the organic materials originates from a strong delocalization of ‘p’ electrons along the length of molecules [15]. It is, therefore, possible to tune or tailor the molecular structure to enhance the nonlinear optical properties. Most of the optical device applications also require a thorough understanding of its third order nonlinear optical properties, which is an important part of this investigation. Second harmonic generation (SHG) efficiency of crystalline materials depends both on the magnitude of molecular hyperpolarizability (b) and on the orientation of the molecules in the crystal lattice [16]. Organic molecules, in general, are potentially more attractive and versatile than inorganic compounds because of their large b-values, fast response time, high resistance to optical damage and almost unlimited possibilities of designing molecules suitable for SHG [17,18]. But practical applications are limited due to poor chemical stability, absorption of visible light due to conjugation, poor phase matching properties and inability to grow bulk crystals. This paper deals with the details of synthesis, growth, structure and characterization of a new organic material MMP. Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/optlastec Optics & Laser Technology 0030-3992/$ - see front matter & 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.optlastec.2012.01.017 n Corresponding author. Tel.: þ91 8970093263; fax: þ91 8242287367. E-mail address: deepak.dsilva@gmail.com (E.D. D’silva). Optics & Laser Technology 44 (2012) 1689–1697