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Chapter I Brief Introduction...
advantages and disadvantages [31], while in semi-organic or metalorganic
materials the aim is always to combine advantages of the both. All the three
types of NLO materials are briefly out lined here by.
Inorganic NLO Materials
These are covalent and ionic bulk materials where the optical
nonlinearity is a bulk effect. The phenomenon of SHG in inorganic materials
was first reported in 1961, which led to the development of recent NLO
materials such as inorganic systems, semi conductors and inorganic
photorefractive crystals. The examples of this type of crystals are lithium
niobate (LiNbO3), potassium niobate (KNbO3), barium titanate (BaTiO3),
potassium titanly phosphate (KTiOPO4 KTP), potassium dihydrogen
phosphate (KH2PO4,KDP), potassium deuterium phosphate (KD*P),
ammonium dihydrogen phosphate (NH3PO4, ADP), lithium iodate (LiIO3),
etc., and a variety of semiconductors such as gallium arsenide (GaAs),
cadmium sulphide (CdS), cadmium telluride (CdTe), zinc germanium
phosphide (ZnGeP2) and teluride (Te), Cadmium germenium arsenide
(CdGeAs2 ) and Silver gallium selenide (AgGaSe2) are appropriate infrared
NLO materials.
Nikogosyan [32] have carried out detailed survey of all NLO properties of
various materials. BBO is an efficient NLO crystal for second, third and forth
harmonic generation of Nd;YAG lasers and best NLO crystal for fifth harmonic
generations. The conversion efficiency of BBO is 70% for SHG, 60 % for THG
and 50% for FHG. KTP is also well-known NLO crystal with SHG coefficient
about three times of KDP.
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