Sapphire (crystalline Al2O3)
is free of absorption in the range 240 nm – 4 µm. Optical components generally have c-cut (0001-orientation).
It stands out by strength, hardness, chemical and thermal stability and is often used as high pressure and high temperature window material and for viewports.
Compared to Fused Silica it has 20 times higher heat conductivity. In addition it is insoluble in most common acids.
LASEROPTIK offers ultrahard coatings that parallel the material hardness and allow best environmental durability.
Yttrium Aluminium Garnet (Y3Al5O12) has nearly the same IR transmission as Sapphire, but is not birefringent and has a high optical homogeneity.
It is pulled from the melt in the same manner as the Nd:YAG rods by Czochralski method, which produces high quality crystalline boules without any inclusions and bubbles.
Due to a special thermal treatment, the YAG material has a minimum of internal stress.