Download (4Mb) - Etheses - Saurashtra University

Chapter VI UV-Vis Spectroscopic….
Chapter VI
UV-Vis Spectroscopic and SHG Efficiency Studies of Pure and
L-histidine, L-threonine and DL-methionine Doped KDP
6.1 Introduction
Crystals
Nonlinear optical (NLO) materials play a vital role in the fabrication of
optoelectronic devices. Recent interest is focused on the development of
materials which have suitable NLO properties for use as the active media in
efficient second harmonic generators, tunable parametric oscillators and
broadband electro-optic modulators. In this regard, a large number of
compounds are needed to be screened for NLO applications. The Kurtz
powder technique represents the first real means of screening experimentally
large numbers of unknown materials for non linear activity without the need of
growing good quality crystals of each material. In 1968 Kurtz and Perry [1, 2]
showed that it is possible, by measurements on powders, to ascertain
whether a crystal has large or small nonlinearity as well as it can be phase
matched or not. From this information and the commonly known data of
crystal properties, the probability of selecting a particular material for crystal
growth to achieve NLO application is drastically increased. Kurtz and Perry [2]
also proposed a powder SHG method for comprehensive analysis of the
second order nonlinearity. Employing this technique, Kurtz surveyed a very
large number of compounds.
A good NLO crystal should also possess good transmission in ultra-
violet and visible region. It is also important to find the UV cut-off limit for
particular crystal. For this purpose UV-Vis spectroscopy is usually employed.
223