Silicon (Si)

Silicon has blue-gray appearance. It has peak transmission range of 3 - 5 µm over the total transmission range of 1.2 - 8 µm. Due to high thermal conductivity and low density, it is suitable for laser mirrors and optical filters. Large blocks of silicon with polished surfaces are also employed as neutron targets in physics experiments. Si is low-cost and lightweight material, it is less dense than Ge or ZnSe & has a similar density to optical glass, so it can be used in some circumstances where weight is a concern. AR coating is recommended for most applications. Silicon is grown by Czochralski pulling techniques (CZ) and contains some oxygen which causes a strong absorption band at 9 µm, so it is not suitable for use with CO₂ laser transmission applications. To avoid this, Silicon can be prepared by a Float-Zone (FZ) process.