The
current advances in science and technology have brought a great demand of
various crystals with abundant applications. A field of multidisciplinary
nature in science has been emerged, known as crystal growth, which deals with
the crystal growth methods, crystals characterizations and crystal growth
theories. There are different types of crystals having various applications
grown by different techniques.

One
such interesting crystal is non linear optical crystal which can be used in wide range of optical
applications including laser harmonic generations (SFG), frequency conversion
(DFG), optical parametric generation (OPG), optical parametric amplification
(OPA) and electro-optical modulation. After the discovery of the NLO effect scientist immediately predicted
that any practical applications of NLO would depend on the development of new
crystals.

Today some scientist are even inclined to think of
NLO crystals as the feature optical semiconductor and research for new
materials are still very active. The demand for nonlinear optical crystals with
superior properties is increasing due to sudden large increase in the design of
nonlinear optical devices with higher performance. The NLO crystals can be classified into Inorganic, Organic and
Semi organic categories. Organic materials are known for their low cost, fast
and large nonlinear response over a broad frequency range, inherent synthetic
flexibility and high optical damage threshold.

Generally,
there are three main categories of crystal growth processes, S – S (process
involving solid – solid phase transitions), L – S (process involving liquid –
solid phase transitions) and V – S (process involving vapor – solid phase
transitions).

 Our work is based on organic and inorganic
crystals by solution growth technique at room temperature. In solution growth,
the chemical components that form the crystal are dissolved in a liquid medium
or flux, and allowed to crystallize slowly as the temperature drops. According
to the solubility of the crystal material, different solution growth techniques
are employed. When large volumes of single crystal materials are needed for
certain applications, solution growth methods may offer an advantage of easier
scaling-up processes.  The synthesis and
deep study of such NLO crystals and reporting the findings would be highly
valuable to the optical applications.

Our
interest is to synthesis some organic and inorganic NLO crystals for XRD, FTIR (Fourier transform
infrared spectroscopy) analysis to confirm the functional group present in the
crystal. Secondly Ultra violet (uv) – visible (vis) -near infrared (NIR)
study is used for optical (reflectance, transmittance and absorbance)
measurements in the wavelength range (175-3300 nm).

Subsequently
IR, Raman Infrared and Raman spectroscopy involve the study of the interaction
of radiation with molecular vibrations, Differential
Thermal Analysis (DTA which measures the relative expansion/ contraction
between a sample and the standard with varying temperature). Thermo gravimetric
analysis (TGA), measures the change in mass of the sample with varying
temperature, Differential scanning Calorimeter (DSC) measures the energy
changes in the sample with varying temperature by measuring the heat flow in
the form of temperature difference between the reference and the sample.

Further, Micro hardness test which is used to determine the
hardness of a material to deformation. Finally, the most common and important
test in NLO phenomenon is the second-harmonic-generation (SHG) to prove the second harmonic efficiency.