When people think of transparent materials, they often think first of glass or plastic. Indeed, for everyday applications, these materials are hard to beat: They offer excellent optical properties, adequate mechanical properties, and can be fabricated easily and affordably on an industrial scale.

In extreme environments, however, these materials fall short of the mark. Glasses and plastics simply cannot withstand the extreme thermal and mechanical loads encountered during hypersonic flight or when monitoring experimental fusion reactors, for example.