High-damage-threshold antireflection coatings on diamond for CW and pulsed CO2 lasers

A multilayer antireflection coating for diamond optics that allows work in the infrared spectral range of 8 -12 µm with minimal optical losses is developed. The optical transmittance of a chemical vapour deposition diamond plate coated with this film on both sides exceeds 94% over the whole specified wavelength range. The coatings deposited on the diamond plate were damage-tested by coherent-wave and pulsed (τ = 90 ns) CO2 lasers. Results of the tests demonstrated that the coating can withstand prolonged radiation loads with intensity above 3 MW cm−2 in a continuous-mode laser exposure. In the case of a nanosecond pulsed action, destruction of the coating begins at intensities greater than 50 MW cm−2.