Fluorophosphate glass is a class of optical glasses composed of metaphosphates and fluorides of various metals. It is a variant of phosphate glasses. Fluorophosphate glasses are very unusual in nature. Fluorophosphate glasses have ultra-low theoretical loss of 0.001 dB/km, longer fluorescent lifetime of rare earths, lower coefficient of thermal expansion of ~13/ðC.
Some fluorophosphate glasses are used as low dispersion glasses. Some show anomalous partial dispersion. One such glass is composed of Ba(PO<sub>3</sub>)<sub>2</sub>, Al(PO<sub>3</sub>)<sub>3</sub>, AlF<sub>3</sub>, and alkaline earth fluorides MgF<sub>2</sub>, CaF<sub>2</sub>, SrF<sub>2</sub>, and BaF<sub>2</sub>, with possible addition of titanium, sodium, potassium, and/or hydrogen. The components by wt.% are 0.5âÂÂ3% Mg, 8âÂÂ10% Ca, 12âÂÂ20% Sr, 9âÂÂ12% Ba, 7âÂÂ9% Al, 5âÂÂ9% P, 8âÂÂ12% O, and 35âÂÂ38% F.
Some doped fluorophosphate glasses are used in laser technology. They are attractive here for their small refractive index nonlinearity. Rare-earth elements are popular dopants. One of the applications is for optical amplifiers.
Exotic dopants like fullerenes and quantum dots can be employed.
Tungsten-doped tin-fluorophosphate glasses (SnO-SnF<sub>2</sub>-P<sub>2</sub>O<sub>5</sub>) can be used for hermetic sealing of organic light-emitting diodes and other devices.