Optical properties of diamond and applications as radiation windows

Diamond is an ideal radiation window material in particular for applications involving high power levels and mechanical, thermal or chemical load. Due to its large bandgap (5.5 eV) and the lack of infrared active fundamental vibrational modes, diamond is optically transparent over a large wavelength range. Even at elevated temperatures, diamond remains transparent, since the large bandgap does not allow the formation of free carriers. This Datareview summarizes the properties of chemical vapour deposition (CVD)-diamond relevant to radiation windows applications. Emphasis is put on windows for high-power CO2 lasers and microwave (Gyrotron) tubes. for a more detailed discussion of optical properties and applications the reader is referred to a recent review.