Single crystal sapphire windows are ideal for demanding applications (such as laser systems) because of their extreme surface hardness, high thermal conductivity, high dielectric constant and resistance to common chemical acids and alkalis. Sapphire is the second hardest crystal next to diamonds and, because of their structural strength, sapphire windows can be made much thinner than other common dielectric windows with improved transmittance. Chemically, sapphire is single crystal aluminum oxide (Al2O3) and is useful in a transmission range from 0.15 to 5.5 microns.
| Specification | |
| Material | Optical Sapphire (Al2O3) |
| Surface Accuracy | 2 waves per 25.4mm at 632.8nm over 90% of aperture |
| Surface Quality | 80-50 |
| Roughness | 0.1 micron/inch |
| Parallelism | <=3.5 arc min. |
| Birefringence (no-ne) | 0.008 for visible light orthogonal to optical axis |
| Axis Orientation | Random |
| Coating | None |
