Polymeric materials, advantages nonlinear optical material

A number of other polymeric solids have also been the subject of much interest because of their special properties, such as polymers with high photoconductive efficiencies, polymers having nonlinear optical properties, and polymers with piezoelectric, pyroelectric and ferroelectric properties. Many of these polymeric materials offer significant potential advantages over the traditional materials used for the same application, and in some cases applications not possible by other means have been achieved. 

The strong interest in nonlinear optical (NLO) properties of organic materials in the past two decades is due to the electronic nature of the nonlinearity and the related fast response. Possible applications are for second-harmonic generation (SHG) and for electro-optic modulation due to the Pockels effect. The advantage of polymeric materials is easy processibility (especially to obtain thin films), which allow the realization of integrated optical elements and higher flexibility in molecular engineering [15,129]. 

This article introduces the field of nonlinear optics and the electronic nonlinear optical (NLO) response of polymers and pol5mier composites. Both second- and third-order NLO phenomena are included, with primary emphasis on harmonic generation, the intensity-dependent refractive index, and nonlinear (multiphoton) absorption effects. The beginning sections introduce the phenomena and explain how the order of the nonlinearity can be understood from a series expansion of the polarization in powers of the electric-field. In addition to listing the variety of nonlinear optical phenomena and some applications, some of the advantages of polymeric materials for NLO applications are also surveyed. 

Because of these advantages as well as orientational enhancement effects and the superior compositional flexibility of pol5nners, the number of studies of polymers for photorefraction grew rapidly during the 1990s and into the current decade. It is now common to see a chapter on polymeric photorefraction in treatises that once emphasized only inorganic crystalline materials (for example, see References 23-27) and to see specific sections on photorefraction in overviews of nonlinear optical properties of pol5nners (for example. See references 28-31). 

Combinations with Liquid Crystais. Because polymeric photorefraction is greatly enhanced by the fast reorientation of the nonlinear optical component, many researchers have investigated the use of liquid crystals as ingredients in polymer-composite photorefractives (149-152). Readers looking for a more detailed understanding of liquid crystalline polymers should also see Liquid Crystalline Polymers, Side-Chain. A major advantage with these materials is that... 

Polymeric materials can be formed into efficient second-order nonlinear optical materials. These materials simultaneously take advantage of the large... 

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