mirror substrates

Mirror substrates are made of optical materials and used in reflection not refraction so optical properties of material have no influence on the mirror properties. Substrate material is chosen mostly in due to mechanical properties and environment where finished element will work. When B270 or BK7 are commonly used for mirrors substrates working in room temperature, Zerodur or quartz glass are recommended for all these performances where changes in the mirror caused by temperature fluctuations must be taken into account.
Mirror substrates are usually one-side polished and one-side plane and matt.