Fluorophosphate glass
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 theoritical loss of 0.001 dB/km, longer fluorescent lifetime of rare earths, lower coefficient of thermal expansion of ~13×10−6/°C.
Some fluorophosphate glasses are used as low dispersion glasses. Some show anomalous partial dispersion. [1] One such glass is composed of Ba(PO3)2, Al(PO3)3, AlF3, and alkaline earth fluorides MgF2, CaF2, SrF2, and BaF2, with possible addition of titanium, sodium, potassium, and/or hydrogen. The components by wt.% are 0.5–3% Mg, 8–10% Ca, 12–20% Sr, 9–12% Ba, 7–9% Al, 5–9% P, 8–12% O, and 35–38% F.[2]
Some doped fluorophosphate glasses are used in laser technology. They are attractive here for their small refractive index nonlinearity. [3] Rare-earth elements are popular dopants. One of the applications is for optical amplifiers.
Exotic dopants like fullerenes [4] and quantum dots [5] can be employed.
Tungsten-doped tin-fluorophosphate glasses (SnO-SnF2-P2O5) can be used for hermetic sealing of organic light-emitting diodes and other devices. [6]
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