ABSTRACT
The field of nonlinear optics became of considerable interest in 1990s with the development of promising organic molecular and polymeric materials [1-4). Nonlinear optical materials are expected to have a wide range of applications in photonic technology, including harmonic generators, optical computing, telecommunications, laser lithography, image processing, switching, sensors, and overall photonic transmission. Organic materials that have been investigated for nonlinear optics can be summarized into several different categories such as single crystals, guest-host systems, Langmuir-Blodgett (LB) films, polymers such as NLO-dye grafted polymers and polar polymers, self-assembled systems, and liquid crystalline materials [5-8]. Recently a great interest in nonlinear optical organometallic compounds has been seen because the metal-to-ligand bonding can be utilized in optimizing photonic functions [6,8]. In particular, organic polymers seem more promising due to their low costs of fabrication and greater compatibility with desired substrates as well as tremendous possibilities for tailoring structures with high mechanical strength and environmental stability. An excellent review dealing with the second-order nonlinear optical polymeric materials has been recently published by Burland et al. [9]. A wide variety of polar polymers or more specifically piezoelectric polymers [10-12] is also available nowadays that can be used for second harmonic generation and electrooptic effects. Polar polymers are important elements in the field of nonlinear optics, as they show temporal stability of second-order NW effects. Second-order nonlinear optical properties of various ferroelectric polymers such as poly(vinylidene fluoride) (PVDF) and its copolymers, vinylidene cyanide copolymers, polyureas, and ferroelectric liquid crystalline polymers will be discussed here.
