Window material optical properties

Optics Electrochromic displays, optical filters (windows with adjustable transparency), materials with non-linear optical properties... 

Single-crystal diamond is the ideal material with remarkable optical properties, high heat resistance, extreme hardness, and excellent chemical resistance. But, because of its high cost and size limitation, it is only used in exceptional cases, such as the window... 

Fig. 14. Examples of optical properties of materials (reflectance, transmittance) for window structures. When used in conjunction with solar spectral distributions, energy savings can be...

The optical properties of ceramics are useful in the ultraviolet, visible, and infrared ranges of the electromagnetic spectrum, and one key quantity used to describe the optical property of a material is the refractive index, which is a function of the frequency of the electromagnetic radiation. Other quantities used to characterize optical performance are absorption, transmission, and reflection these three properties sum to unity and are also frequency dependent. The last three properties govern many aspects of how light interacts with materials in windows, lenses, mirrors, and filters. In many consumer, decorative, and ornamental applications, the esthetic qualities of the ceramic, such as color, surface texture, gloss, opacity, and translucency, depend critically on how light interacts with the material. 

The optical properties of diamond films have been studied quite extensively, too. In the spectral range from about 220 to 1000 nm pure diamond does not show any absorption at aU. This transparency renders it an attractive material for spectroscopic appUcations Uke as windows or lens systems in spectrometers. 

Optical properties are of most relevance for plastics, although color and gloss can be important for any of the material classes for products where aesthetic considerations are of intere.st. In fact for most plastics products it is the aesthetic properties, such as surface texture, color, gloss, and reflectance, that are important. Light transmission characteristics and refractive index measurements are needed for only a relatively few products such as lenses and windows where the transparency or transluccncy of the material is a paramount consideration. This is unfortunate, as light transmission and refractive index are a good deal easier to define and and to correlate with visual experience than the other properties mentioned. Meeten [I] has edited a detailed text on the optical properties of polymers. 

Considerable progress has been achieved in recent years on improving the optical properties of CVD diamond and in making this material available in large sizes and with reproducible and consistent properties [4,5,35] so that its use in actual laser systems has become a practical reality [48]. This section reviews the technical issues relevant to the performance of windows for high power lasers comparing the specific case of CVD diamond and ZnSe for the transmission of CO2 laser beams. 

Because the performance of spinel windows is also very sensitive to the quality of the precursor materials (both purity and morphology), there have been researches that can be found in the open literature. To produce better spinel precursor powders, various methods have been developed. For example, a new method has been used to synthesize spinel powders from boehmite, in which Mg " ion was metal exchanged onto the surface of boehmite particles [208]. In this method, particle size, size distribution, purity, and stoichiometry of the Mg-doped boehmite powders could be well controlled. Such powders exhibited good sinterability and resulted in spinel ceramics with desired optical properties. 

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