Sapphire windows are made from single crystal sapphire, which is ideal for applications used in harsh enviroments such as laser systems and subsea imaging due to its extremely high surface hardness, high thermal conductivity, high dielectric constant and resistance to common chemical acids and bases system. Sapphire crystal is second only to diamond in hardness and due to its structural strength, sapphire windows can be much thinner than other ordinary (K9, JGS1) windows. Chemically, sapphire is single crystal aluminum oxide (Al2O3) with very good transmittance from 180nm to 5500nm.

Sapphire window is widely used in UV to MIR applications, could transmit between UV and IR spectrum at 180nm-5um. But feature a high refractive index at 1.75, we often deposit thin film (Anti-reflection coating) on both sides to improve the transmission.