FS
Fused silica (FS) is glass that consists of pure SiO2. Depending on the manufacturing process, it is transparent in the wavelength range between 0.16 µm and 3.5 µm. The transmission in the ultraviolet range is greater with FS than with other glasses. The transmission in the infrared range depends on the water content in the material and is determined during production. Two different types of FS are distinguished:
UV-grade FS is thermally treated. As a result, it has a higher water content and fewer metallic impurities, which increases its transparency in the ultraviolet range.
IR-grade FS is treated electrically. It has more metallic impurities, which limits its transmission in the ultraviolet range to 0.25 µm. However, the transmission in the infrared range increases to 3.6 µm.
Fused silica has physical properties that allow the material to be used in a wide range of applications. Due to a low coefficient of thermal expansion, FS is resistant to high temperature differences and can be exposed to continuous temperatures of up to 1100 °C. Temperature loads of up to 1700 °C are possible for short periods. Furthermore, the material has a high chemical and mechanical resistance.
Fused silica is used for the production of windows, mirrors and prisms in the UV and IR range. Due to its low thermal expansion, it is also used as a substrate for precision mirrors and mirrors for telescopes.
