Abstract:
In the present thesis, we have tried to elucidate the proper parameters upon
which the nonlinear optical properties of materials depend. The thesis is
divided into five chapters.
The first chapter provides a brief introduction to Nonlinear optics and
its various applications. In the next chapter we have developed a model
considering the orientation effects of the molecules in an assembly and discuss
briefly how such different orientations can lead to changes in the optical
properties of the molecular assemblies. We have also outlined the methods
for stablilization of such assemblies due to Hydrogen - bonding interactions.
In the third chapter we consider a series of push-pull type organic chromophores and consider their various dipolar orientations and suggest the
best orientation for maximizing their NLO responses based on the theory
developed in chapter 2.
In the fourth chapter, we consider a series of bridged push-pull chromophores where orientation of the dipoles are restricted by the degrees of
freedom (bonds connecting the push-pull moieties) and try to understand
the factors that govern their behaviors in an electric field. We also suggest
modifications to the experimental systems that will maximize their optical polarizations.
Finally, in the fifth chapter, we extend our dipole interaction theory to
finite-sized metallic clusters. These hetero-atomic metal clusters are interesting because of the ease by which they can be polarized due to out-of-plane
charge transfer contrary to TT- conjugated organic polymers which are polarized due to delocalization of the vr-electrons. We compare and contrast the
NLO properties of the conventional organic 7r-conjugated molecules to that
of these metal clusters of similar sizes and geometries. We show that the
NLO properties for these metal-clusters are orders of magnitude higher than
their organic counterparts. We conjecture that these metal-clusters are good
candidates for next generation NLO materials.
