A mirror blank is an optical material base that is polished to high precision and coated with a high-reflection film. When selecting a blank, key performance parameters are considered: the Coefficient of Thermal Expansion (CTE)—the degree to which a material expands or contracts with temperature change; Thermal Conductivity—its ability to conduct heat; Specific Stiffness—the ratio of its Young's modulus to density; Manufacturabilit; along with material homogeneity and internal defects.
Fused silica.
Low-expansion glass-ceramic(e.g., Zerodur, ULE).
Special crystals (sapphire).
| Material | Fused Silica |
| Surface Flatness | λ/10@633nm |
| Backside Surface | Polished |
| Thickness Tolerance | ±0.2mm |
| Diameter Tolerance | +0.0,-0.1mm |
| Angle of Incidence | 45° |
| Parallelism | ＜3 arc min |
| Surface Quality | 20/10-15/5 |
