Low Refractive Index and Anti-Reflection Effect

Alkaline earth fluorides having low refractive indices are useful, especially as coatings, in optics because of their high optical transparency in a wide range of wavelengths from IR to 

Metal fluoride coatings that are prepared by common techniques such as evaporation or sputtering are normally dense and have refractive indices close to that of bulk fluoride materials. 

Rywak and Burhtch prepared a nanocrystalhne MgF2 sol, abrasion-resistant MgF2 films from it and Si02-MgF2 composites both in the bulk and in the thin-film form [69]. In the synthesis of the composites, MgF2 sols were prepared from methanolic H2O2 and 

100 °C. Because the wet-processed fluoride coatings generally have lower mechanical strength than the dry-processed ones, the nanocomposite with Si02 may be the best way to produce AR coatings with improved performance. 

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