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Chapter I Brief Introduction...
memory [28], two photons scanning microscope [29] and demonstrated the
3D micro-modification and tera bit /cm 3 3D optical data storage.
The nonlinear optical phenomenon of SHG has intrinsic sensitivity to
the voltage across a biological membrane. The second order NLO process
has been used to monitor membrane voltage by Bouevitch et al [30].
1.7 Materials for Nonlinear Optics
As the technological importance and applications of NLO materials is
continuously increasing the quest is going on to develop the most suitable
NLO material. The understanding of the nonlinear polarization mechanisms
and their relation to the structural characteristics of the materials has been
considerably improved. The new development of techniques for the
fabrication and growth of artificial materials has dramatically contributed to
this evolution. The aim is to develop materials presenting large nonlinearities,
at the same time, not only all the technological requirements for applications
such as, wide transparency range, fast response and high damage threshold,
but also satisfying the processability, adaptability and interfacing with other
materials.
Advances in the development of NLO materials can be divided into
three different areas.
(i) Discovery of new NLO materials
(ii) Growth of promising NLO crystals
(iii) Improving the characteristics of NLO crystals
From materials point of view, the NLO materials can be broadly
classified in three different categories as, inorganic, organic and semi-organic
or metalorganic materials. Inorganic and organic possess their own set of
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