Download (4Mb) - Etheses - Saurashtra University

Chapter VI UV-Vis Spectroscopic….
The SHG efficiency is estimated with respect to standard KDP and
listed in table (6.1) for different samples. It can be noticed from table (6.1) that
as the doping of L-histidine, L-threonine and DL-methionine increases in KDP
crystals, the SHG efficiency increases. The amino acid doping is beneficial for
SHG efficiency. The SHG of the doped crystals is found to be more than the
pure one.
Table: 6.1 SHG efficiency of pure, L-histidine, L-threonine
and DL-methionine doped KDP crystals.
Samples SHG Efficiency
Pure KDP Crystal 1
KDP + 0.3% L-histidine 1.33
KDP + 0.4% L-histidine 1.61
KDP + 0.5% L-histidine 1.80
KDP + 0.3% L-threonine 1.11
KDP + 0.4% L-threonine 1.24
KDP + 0.5% L-threonine 1.46
KDP + 0.3% DL-methionine 1.17
KDP + 0.4% DL-methionine 1.26
KDP + 0.5% DL-methionine 1.71
Attempts have been made to explain the origin of optical non-linearity
in terms various chemical bond contributions. Lin et al [35] studied the
mechanism of the optical behavior of KDP crystals theoretically by using the
plane wave pseudo-potential total energy software package. The origin of
non-linear effects has been explained through the real space atom cutting
analysis of KDP. The contribution of PO4 group to the SHG effects is
dominant. And the hydrogen bonds contribute much for birefringence. In
another study, Xue and Zhang [36] have studied the hydrogen bonds such as
O-H---O, N-H---O in KDP and ADP. The second order NLO behavior of
crystals studied and it is found that hydrogen bonds play very important roles
in NLO contributions to the total nonlinearity. Moreover, Xue and Ratajczak
235