Nonlinear optical materials , See

This investigation shows that an organized assembly ranging from isolated molecules to expanded structures stabilized inside a sodalite host matrix (Figure 1) can be readily fabricated out of a material that is normally a I-VII semiconductor. The (8-2n)Na,2nAg,2X-SOD sodalites might find applications as electronically tunable nonlinear optical materials (see later). 

These mixed oxides have been considered as nonlinear optical materials (see Nonlinear Optical Materials). They crystallize as ordered derivatives of the cristobalite structure. As early X-ray structural studies were performed on twinned crystals grown from congment melts, their true symmetry was not firmly established. Untwinned single crystals have been produced by hydrothermal methods, and the space group has been convincingly established as 14. 

The cadmium chalcogenide semiconductors (qv) have found numerous appHcations ranging from rectifiers to photoconductive detectors in smoke alarms. Many Cd compounds, eg, sulfide, tungstate, selenide, teUuride, and oxide, are used as phosphors in luminescent screens and scintiUation counters. Glass colored with cadmium sulfoselenides is used as a color filter in spectroscopy and has recently attracted attention as a third-order, nonlinear optical switching material (see Nonlinear optical materials). DiaLkylcadmium compounds are polymerization catalysts for production of poly(vinyl chloride) (PVC), poly(vinyl acetate) (PVA), and poly(methyl methacrylate) (PMMA). Mixed with TiCl, they catalyze the polymerization of ethylene and propylene. 

The material system is a Langmuir-Blodgett film of the S enantiomer of a chiral polymer deposited on a glass substrate. The polymer is a poly(isocyanide)30 functionalized with a nonlinear optical chromophore (see Figure 9.14). In this particular system the optical nonlinearity and chirality are present on two different levels of the molecular structure. The chirality of the polymer is located in the helical backbone whereas the nonlinearity is present in the attached chromophores. Hence, this opens the possibility to optimize both properties independently. 

In the fields of organometallic polymer see Polymer) chemistry , in which complexes may have particularly interesting physical properties (liquid crystallinity, optical nonlinearity see Nonlinear Optical Materials), etc.), or of molecular electronics , metal alkynyl complexes play a significant role. These areas have been the subject of recent reviews, thus only a brief overview of methods to prepare iron alkynes will be given here. Liu has also recently reviewed the cyclization chemistry of alkynyl organometaUics, including those of iron. ... 

Phosphates showing a bulk polarization (i.e. ferroelectric phases) may be used for nonlinear optical processes see Nonlinear Optical Materials) such as second harmonic generation and electro-optic switching. KTP (Section 5.2.2) and related phases (NH4T10P04 and KTi0As04) are very efficient nonlinear materials. The ferroic phosphates described above also show nonlinear properties. KDP materials are inferior to KTP types but they find use in electro-optics as they are very transparent over a wide frequency range. 

See Fig. 7 ofB. Champagne and B. Kirtman, ia Handbook of Advanced Electronic and Photonic Materials and Devices, Vol. 9, Nonlinear Optical Materials, H. S. Nalwa, ed., Academic Press, San Diego, 2001, Chapter 2, p. 63. 

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