Silicon – Si
lenses, windows, mirrors, filters and prisms
Silicon is primarily used in optical windows in the 3-5 micron region and as a substrate for optical filters. Silicon has low density and high thermal conductivity making it an ideal material to be used for laser mirrors. Grown by two different techniques, Czochralski (CZ) which contains some oxygen which causes an absorption band. Optical quality Silicon is normally lighted doped (5 to 40 ohm cm) and because it has a high refractive index it must be anti-reflection coated in order to achieve a high optical transmission.
| Transmission Range | 1.2 – 15.0 µ |
| Crystal Structure | Diamond |
| Cleavage Plane | 111 |
| Colour | Metallic lustre |
| Density | 2.329 (25°) |
| Melting Point (°) | 1420 |
| Reflection Loss | 46.1% (10µ) for 2 surfaces |
| Solubility index | insoluble |
| Hardness (Knoop) | 1150 |
| Thermal Conductivity (cal/cm sec°C) | 0.39 (40°C) |
| Thermal Expansion coefficient (/°C) | 4.15×10-6(10-50°C) |
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