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Chapter I Brief Introduction...
Sapphire laser [104]. The mechanism for linear and nonlinear optical effects in
KBBF crystals has been discussed by Lin et al [102].
Another potential NLO crystal developed is organic crystal DAST
(Dimethylamino-N-methyl-4-stilbazolium tosylate). DAST was first reported by
Marder [27] and still it is recognized as the state of art in organic NLO. DAST
is having high second order NLO and electro optic coefficients, being 10 times
and twice as large as LiNbO3, respectively. Extraordinary high nonlinearity in
combination with low dielectric constant allows DAST for high speed electro-
optic applications and broadband THz wave generation. However, DAST is
also efficient material for generation and detection of THz waves using the
NLO process of optical rectification or difference frequency generation.
Moreover, significant progress has been made in terms of integrated EO
(Electro-Optic) applications of DAST and organic crystals in general, which
have long been hindered due to the difficult growth of their films with a
controlled thickness on appropriate substrates as well as due to the special
chemically compatible photolithiographic process needed for structuring.
Jazbinsek et al [105] have reviewed progress on microstructure techniques
developed for DAST, modified photolithography, photo-bleaching, femto-
second laser ablation, grapho-epitaxial growth, ion implantation and direct
electron beam structuring.
Engineering the domain is a hot topic in condensed matter physics and
photoelectronics. The domain engineered ferro-electric crystal in which the
ferroelectric domain is modulated artificially according to some sequence,
forming so-called Super-lattice structure. The physical properties associated
with third-rank tensors, like nonlinear susceptibility tensor, in such a crystal
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