Al2O3 crystals (Sapphire), featuring broad optical transmission from 150-5500nm spanning from UV to MWIR spectrum, and robust mechanical/thermal properties, are excellent for applications involving harsh and variant environments or requiring a broad transparent wavelength range (e.g. windows of sensors and detectors, IR applications, etc.). The material's most distinguishing attribute is its unequaled mechanical strength, being the second hardest material after diamond, single sapphire crystals have a Knoop Hardness of 1800-2200, making the windows made from single crystals sapphire resistant in extreme to chemical corrosion and abrasions. Sapphire windows might be produced into thin optics without fracturing because of the tight internal covalent bonding of single-crystal sapphire while demonstrating good thermal stabilities due to its high thermal conduction.