NONLINEAR OPTICAL AND ELECTROOPTIC CERAMICS

NLO effects result when the polarization response of the valence electrons becomes significantly anharmonic, usually in intense light beams where the magnitude of E is very large. The magnitudes of the coefficients of the terms in equation 2 diminish rapidly at higher orders, and thus readily observable NLO effects are either second-order third-order (X ) processes. Most NLO appHcations rely on second-order processes. However, 

Materials. NLO materials possess a high degree of optical nonlinearity, physical durabiHty and chemical inertness, and high threshold to optical damage. In addition, it must be possible to process the materials into the form required by the intended appHcation. 

Here N is the number of bonds or molecules of a given type in the crystal, and is a geometric tensor associated with a particular microscopic polarizabiHty P this tensor is related to the crystallographic orientation of the bond. In extended systems such as covalent soHds it becomes difficult to define a species to which one can assign a unique value of P, and thus the value of P for a given group can only be an approximate representation. In 

Kirk-Othmer Encyclopedia of Chemical Technology (4th Edition) 

Nonoxide NLO ceramics include Si and compound semiconductors (qv) having the silicon stmcture, eg, GaAs, InP, and InSb, as weU as ferroelectrics such as SbSI. These materials tend to be more highly nonlinear than oxide ceramics, although lack of transparency at visible and uv wavelengths prevents them from competing with the oxides for the same appHcations. 

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CERAMCS-ELECTHONICPROPERTIESANDMATERIALSTHUCTURE] (Vol5) [CERAMCS - NONLINEAR OPTICAL AND ELECTROOPTIC CERAMICS] (Vol 5)... 

Nonlinear optical and electrooptic ceramics. Electronic properties and material stmcture. 

Perovskites have the chemical formula ABO, where A is an 8- to 12-coordinated cation such as an alkaU or alkaline earth, and B is a small, octahedraHy coordinated high valence metal such as Ti, Zr, Nb, or Ta. Glass-ceramics based on perovskite crystals ate characteri2ed by their unusual dielectric and electrooptic properties. Examples include highly crystalline niobate glass-ceramics which exhibit nonlinear optical properties (12), as well as titanate and niobate glass-ceramics with very high dielectric constants (11,14). 

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