<P> Lithium fluoride, artificially grown as crystal, is clear and transparent and often used in specialist optics for IR, UV and VUV (vacuum UV) applications . It has one of the lowest refractive indexes and the furthest transmission range in the deep UV of most common materials . Finely divided lithium fluoride powder has been used for thermoluminescent radiation dosimetry (TLD): when a sample of such is exposed to radiation, it accumulates crystal defects which, when heated, resolve via a release of bluish light whose intensity is proportional to the absorbed dose, thus allowing this to be quantified . Lithium fluoride is sometimes used in focal lenses of telescopes . </P> <P> The high non-linearity of lithium niobate also makes it useful in non-linear optics applications . It is used extensively in telecommunication products such as mobile phones and optical modulators, for such components as resonant crystals . Lithium applications are used in more than 60% of mobile phones . </P> <P> Organolithium compounds are widely used in the production of polymer and fine - chemicals . In the polymer industry, which is the dominant consumer of these reagents, alkyl lithium compounds are catalysts / initiators. in anionic polymerization of unfunctionalized olefins . For the production of fine chemicals, organolithium compounds function as strong bases and as reagents for the formation of carbon - carbon bonds . Organolithium compounds are prepared from lithium metal and alkyl halides . </P> <P> Many other lithium compounds are used as reagents to prepare organic compounds . Some popular compounds include lithium aluminium hydride (LiAlH), lithium triethylborohydride, n - Butyllithium and tert - butyllithium are commonly used as extremely strong bases called superbase . </P>

What kind of bond is formed in pure lithium