Specifications:
| Materials | Silicon crystals | Diameter Range | ~ 300mm |
| Aperture | >90% | Dimension Tolerance | +0.0/-0.2mm |
| Thickness Tolerance | +/-0.1mm | Surface Quality | 60/40 S/D |
| Parallelism | 1 arc minute | Chamfer | 0.3-0.5mmx45degree |
| Coating | AR/AR or DLC/AR |
Basic Properties:
| Transmission Range | 1.2 to 15 μm (1) | Refractive Index | 3.4223 @ 5 μm (1) (2) |
| Reflection Loss | 46.2% at 5 μm (2 surfaces) | Absorption Coefficient | 0.01 cm-1 at 3 μm |
| Reststrahlen Peak | n/a | dn/dT | 160 x 10-6 /°C (3) |
| dn/dμ = 0 | 10.4 μm | Density | 2.33 g/cc |
| Melting Point | 1420 °C | Thermal Conductivity | 163.3 W m-1 K-1 at 273 K |
| Thermal Expansion | 2.6 x 10-6 / at 20°C | Hardness | Knoop 1150 |
| Specific Heat Capacity | 703 J Kg-1 K-1 | Dielectric Constant | 13 at 10 GHz |
| Youngs Modulus (E) | 131 GPa (4) | Shear Modulus (G) | 79.9 GPa (4) |
| Bulk Modulus (K) | 102 GPa | Elastic Coefficients | C11=167; C12=65; C44=80 (4) |
| Apparent Elastic Limit | 124.1MPa (18000 psi) | Poisson Ratio | 0.266 (4) |
| Solubility | Insoluble in Water | Molecular Weight | 28.09 |
| Class/Structure | Cubic diamond, Fd3m |
Silicon (Si) Windows manufactured from optical grade silicon are popular for the 1.2 - 7μm spectral region due to their low cost and low density. Due to its low density (half that of germanium or zinc Selenide), silicon is ideal for weight sensitive applications, especially those in the MWIR thermal imaging 3 - 5μm region. Density is 2.329 g/cm3 and Knoop Hardness is 1150, making it harder and less brittle than germanium.
Curves:
1. Transmission curve of the Silicon windows (no coating)
2. Transmission curve of the Silicon windows with AR/AR coating at 3-5μm
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 Windows01-50x40.jpg)