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 theoretical loss of 0.001 dB/km, longer fluorescent lifetime of rare earths, lower coefficient of thermal expansion of ~13{{e|-6}}/°C.{{cite journal |last1=Stokowski |first1=S. E |last2=Martin |first2=W. E |last3=Yarema |first3=S. M |title=Optical and lasing properties of fluorophosphate glass |journal=Journal of Non-Crystalline Solids |date=1 July 1980 |volume=40 |issue=1 |pages=481–487 |doi=10.1016/0022-3093(80)90123-4 |bibcode=1980JNCS...40..481S }}

Some fluorophosphate glasses are used as low dispersion glasses. Some show anomalous partial dispersion.{{cite patent |country=US |number=4859635 |status= |title=Optical fluorophosphate glass having anomalous positive partial dispersion and process for its production |pubdate= |gdate= |fdate= |pridate= |inventor= |invent1= |invent2= |assign1= |assign2= |class= |url=}} 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.{{cite patent |country=US |number=4857487 |status= |title=Optical fluorophosphate glasses possessing positive anomalous partial dispersion and improved physico-chemical properties, and a process for their preparation |pubdate= |gdate= |fdate= |pridate= |inventor= |invent1= |invent2= |assign1= |assign2= |class= |url=}}

Some doped fluorophosphate glasses are used in laser technology. They are attractive here for their small refractive index nonlinearity.{{cite journal |last1=Balda |first1=R. |last2=Fernández |first2=J. |last3=De Pablos |first3=A. |title=Optical properties of Nd 3+ ions in fluorophosphate glasses |journal=Le Journal de Physique IV |date=April 1994 |volume=04 |issue=C4 |pages=C4–509–C4-512 |doi=10.1051/jp4:19944122 |url=https://hal.archives-ouvertes.fr/jpa-00252573/file/ajp-jp4199404C4122.pdf }} Rare-earth elements are popular dopants. One of the applications is for optical amplifiers.

Exotic dopants like fullerenes{{cite journal |last1=Lin |first1=Fucheng |last2=Mao |first2=Sen |last3=Meng |first3=Zhicong |last4=Zeng |first4=Heping |last5=Qiu |first5=Jianqing |last6=Yue |first6=Yong |last7=Guo |first7=Ting |title=Fullerene doped glasses |journal=Applied Physics Letters |date=14 November 1994 |volume=65 |issue=20 |pages=2522–2524 |doi=10.1063/1.112623 |bibcode=1994ApPhL..65.2522L }} and quantum dots can be employed.{{fact|date=June 2022}}

Tungsten-doped tin-fluorophosphate glasses (SnO-SnF2-P2O5) can be used for hermetic sealing of organic light-emitting diodes and other devices.{{cite patent |country=WO |number=2008045249 |status= |title=Durable Tungsten-Doped Tin-Fluorophosphate Glasses |pubdate= |gdate= |fdate= |pridate= |inventor= |invent1= |invent2= |assign1= |assign2= |class= |url=}}