AbstractsPhysics

NLO materials have been researched for nearly five decades from the point of view of understanding the basic mechanisms and also in the pursuit of new materials possessing improved properties. Materials satisfying a set of physico-chemical properties such as wide transmission range, good mechanical hardness, high po-larizablity, noncentric crystal structure, good chemical stability, etc are the ones which are sought after. Several organic and inorganic molecules have been synthe-sized with the hope of finding materials that possess the desired NLO properties. Most of the organic materials are known to possess high figure of merit. However, their poor mechanical strength and needle like growth habit are hindrances to practical applications. Inorganic NLO materials have better mechanical properties but many of them possess small deff and laser induced damage threshold. Semi-organic NLO materials are intended to have the merits of both organic and inorganic counterparts. In this investigation, three important NLO crystals, viz cesium hydrogen L-malate monohydrate (CsLM, CsH[C4H4O5]H2O), cesium lithium borate(CLBO,CsLiB6O10)and near stoichiometric lithium niobate codoped with Nd and Zn (Nd:Zn:LiNbO3)are chosen for detailed study. The thesis is organized into 6 chapters. First chapter contains the theoretical background of the physical and chemical phenomena including a review of nonlin-ear optics, second harmonic generation, multiphoton absorption & refraction con-cepts, single crystal growth, principles of ferroelectricity and the scope of the work involved. For better connectivity, a brief review of the earlier work carried out on the chosen materials is given in the beginning of each chapter. The second chapter discusses the methodology of work and experimental details used in the present study. The third chapter deals with studies on CsLM, the new organometallic NLO crystal. Its structure, electro-optical properties and dielectric properties in FIR region are reported very recently. This material is also reported to show a phase transition at 50 0C though not much is understood about its nature. Further details of crystal growth conditions, nonlinear optical properties and laser damage thresholds are little known on this newly discovered NLO material. In this chapter detailed crystal growth studies and investigations of physical properties are presented. During growth, CsLM crystals manifest in platy and prismatic morphologies depending on level of super saturation invoked. The maximum dimensions of the grown crystal are 20 x15 x35 mm3. It has very good transmission in the range, 250-1300 nm and dislocation density of ≈104/cm2 . The dc conductivity measurements place this crystal between an ionic conductor and a dielectric. Dielectric properties show considerable frequency dispersion and axial anisotropy with є′ being the highest along the polar b axis. Maker fringes experiment reveals that CsLM possesses good second harmonic generation efficiency, an order of magnitude higher than KDP. It also has high laser…