Sapphire Windows are made from Sapphire material, which has transparent range from 180-4500nm. The refractive index is 1.755 at 1000nm.

Specifications:
Material: --------------------------------------------------------- Sapphire
Diameter Tolerance: ------------------------------------------ +0.0, -0.1mm
Thickness Tolerance: ---------------------------------------- ±0.2mm
Clear Aperture: ------------------------------------------------->80%
Parallelism:------------------------------------------------------- 1 arc minute
Wavefront Distortion:-------------------------------------------λ per 25mm@633nm
Surface Quality:------------------------------------------------- 80/50 scratch and dig
Protective Bevel:--------------------------------------------------<0.25x45deg
Coating:-------------------------------------------------------------Uncoated