Silicon (Si), typically in single-crystal form, is a cost-effective, high-thermal-conductivity, and lightweight optical material for the near-infrared (NIR) range. It offers excellent transmittance and favorable thermal properties in the NIR band. It is particularly dominant in the field of high-power laser mirrors. For windows and mirrors operating in the 1–3 μm wavelength range, silicon is arguably the most cost-effective choice.
Excellent thermal conductivity, suitable for high-power applications
Opaque to visible light
Limited to the infrared band
| Transmission Range | 1.2 – 7 μm |
| Refractive Index | 3.4 @ 10 μm |
| Mohs Hardness | 7.0 |
| Uncoated Transmittance | 50 – 55% @ 3–5 μm |
| Fracture Strength | 150 MPa |
