Undoped YAG (Y3Al5O12) is a new substrate and window material for both UV and IR optics.
It is particularly useful for high temperature and high-energy applications.
YAG shows no trace absorption in 2-3micron region where glasses tend to be highly absorbent due to the strong H2O2 band.
The YAG's mechanical and chemical stability is similar to sapphire, but YAG is no birefringence and has higher optical homogeneity.
Physical Properties of Sapphire
Crystal Structure
Cubic:a = 12.01 Å
Crystal Purity
> 99.999 %
Melt Point
1970 oC
Density
4.56 g/cm3
Hardness
8.5 ( mohns )
Thermal Expansion
6.9 x 10-6 / oCat0 - 250 oC
Thermal Conductivity
143 W/(m.k) @ 20 oC
dh / dt
7.4 x 10-6 / oC
Transmission Range
250 ~ 5000 nm without absorption in 2000 - 3000 nm
