Diamond is transparent from the UV (225 nm) to the far infrared. Only minor absorption bands exist resulting from two phonon absorption between 2.5 and 6.5 µm. This makes diamond an ideal material for multispectral optical applications.

Furthermore, its large bandgap (5.45 eV) prevents thermally generated charge carriers at elevated temperatures. Therefore diamond remains transparent even at very high temperatures and radiation intensities.

Beside these properties also its extreme thermal conductivity, hardness, wear and chemical resistance are of importance for various optical applications.

We have summarized the main properties of CVD diamond in our "CVD diamond booklet".