Sapphire Window

Sapphire has a transmission from 190nm to 5300nm and is very strong compared with other optical materials.  Sapphire windows can be used at very high temperatures, up to 2000°C.

The high refractive index of sapphire will give larger reflection than glass so AR coating is more important for sapphire windows than glass or fused silica.
 
Sapphire has excellent strength and abrasive resistance which enables it to be used in the form of very thin windows and extremely harsh environments.  Sapphire is often used for pressure windows or port windows where conditions are severe such as sandy, salty environments where a softer BK7 window would quickly scratch and become unusable.

Specifications: