Sapphire
Sapphire optical blanks and wafers are ideal for applications where high pressure, vacuum, or corrosive atmospheres are a consideration. Sapphire, a single crystal form of Al2O3, is resistant to attack by strong acids. It has high comprehensive strength and a high melting point. It is also resistant to UV radiation darkening.
Calypso Resources, Inc. offers Sapphire windows, meniscus lenses, prisms, wafers of any sizes and configurations for broad spectral ranges.