Sapphire (Al₂O₃)

Sapphire as an optical substrate refers to single-crystal aluminum oxide manufactured into durable optical windows, lenses, and protective components. Known for its exceptional hardness, mechanical strength, and resistance to harsh environmental conditions, sapphire provides optical transmission across the ultraviolet (UV), visible, and portions of the infrared (IR) spectrum. It is commonly used in aerospace, defense, high-temperature optical systems, and protective sensor windows.