Sapphire is a single crystal of alumina, also known as corundum. As an important technical crystal, sapphire has been widely used in many fields of science and technology, national defense and civil industry. Sapphire glass has very good thermal characteristics, excellent electrical and dielectric properties, and chemical corrosion resistance, it is high temperature resistance, good thermal conductivity, high hardness, infrared penetration, good chemical stability. Therefore, it is commonly used to replace other optical materials to make infrared optical Windows, and is widely used in infrared and far-infrared military equipment, such as: It is used in night vision infrared and far infrared scopes, night vision cameras and other instruments and satellites, space technology instruments and instruments, as well as the window of high power laser, optical window, UV and IR window and observation port of low temperature experiment, and has been fully applied in high precision instruments and meters for navigation, aerospace and aviation.