Optics and Optical Materials

Fundamentals of Infrared and Visible Detector Operation and Testing, Second Edition. John David Vincent, Steven E. Hodges, John Vampola, Mark Stegall, and Greg Pierce. 2016 John Wiley Sons, Inc. Published 2016 by John Wiley Sons, Inc. Companion Website www.wiley.com/go/vincent/fundamentals/2e 

Windows, lenses, and mirrors are used in the IR just as they are in the visible. Only the choice of materials is different common glass is opaque beyond 2 pm, so it is not useful as an IR optical material. Many IR transmitting materials are available for windows and lenses, but we will discuss only window materials here. 

Vendors of suitable windows and filters change frequently enough that we will not attempt to include that information here. A quick check on the Web will identify several sources, and we recommend that you compile a list of vendors and search periodically for new vendors to keep that list current. 

Of the many materials available for IR windows, none will be best in all respects. Generally, we must choose the material with the fewest or least objectionable limitations. Factors to consider when selecting a material include the following  

1 Material, Description The common name and the chemical symbol are given. Irtran is the name given by the Eastman Kodak company to their line of hot-pressed polycrystalline compacts. They heat and compress pure, powdered, 

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The following publications provide useful information about optics and optical materials. These are intended to be a starting point rather than exhaustive bibliographies. They are arranged chronologically within each topic. We have tried to provide some early papers for historical interest, as well as some more current material. 

Most of the envisioned practical applications for nonlinear optical materials would require solid materials. Unfortunately, only gas-phase calculations have been developed to a reliable level. Most often, the relationship between gas-phase and condensed-phase behavior for a particular class of compounds is determined experimentally. Theoretical calculations for the gas phase are then scaled accordingly. 

P. A. Tick and P. L. Bocko, "Optical Fiber Materials," The Handbook of Optical Materials, Vol. 3, Marcel Dekker, New York, 1988. 

N. J. Kreidl and J. Rood, in R. Kinglake, ed.. Optical Materials, Applied Optics and Optical Engineering, Academic Press, Inc., New York, 1965. 

Enclosure also changes the redox properties of a compound, its color, and other physical properties (1,2). On this basis nonlinear optical materials, luminescence markers, controlled light switches, and other high-tech devices might be designed and prepared (15,17,137). 

Further subclassification of nonlinear optical materials can be explained by the foUowiag two equations of microscopic, ie, atomic or molecular, polarization,, and macroscopic polarization, P, as power series ia the appHed electric field, E (disregarding quadmpolar terms which are unimportant for device appHcations) ... 

Fig. 1. Representative device configurations exploiting electrooptic second-order nonlinear optical materials are shown. Schematic representations are given for (a) a Mach-Zehnder interferometer, (b) a birefringent modulator, and (c) a directional coupler. In (b) the optical input to the birefringent modulator is polarized at 45 degrees and excites both transverse electric (TE) and transverse magnetic (TM) modes. The appHed voltage modulates the output polarization. Intensity modulation is achieved using polarizing components at the output.

Another growing apphcation that overlaps the electrically functional area is the use of transparent conductive coatings or tin oxide, indium—tin oxide, and similar materials in photovoltaic solar ceUs and various optic electronic apphcations (see Photovoltaic cells). These coatings are deposited by PVD techniques as weU as by spray pyrolysis, which is a CVD process. 

Refractory coatings extensively used in the semiconductor and optical materials industry have an annual add-on value exceeding 10. ... 

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. 

Vinyl neopentanoate is used in the preparation of adhesives and binders (44—46), optical materials for plastic lenses (47), gas permeable membranes for oxygen enrichment (48), and in coating appHcations (49,50). 

Several instmmental methods are available for quantitative estimation of from moderate to trace amounts of cerium in other materials. X-ray fluorescence is widely available, versatile, and suitable for deterrninations of Ce, and any other Ln, at percent levels and lower in minerals and purer materials. The uv-excited visible luminescence of cerium is characteristic and can be used to estimate Ce content, at ppm levels, in a nonluminescing host. X-ray excited optical luminescence (15), a technique especially appropriate for Ln elements including cerium, rehes on emissions in the visible, and also measures ppm values. Atomic emission spectrometry is appHcable to most lanthanides, including Ce (16). The precise lines used for quantitative measurement must be chosen with care, but once set-up the technique is suitable for routine analyses. 

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