Effects of vacuum annealing on the performance of 355nm Al2O3/MgF2 high reflectance coatings

The effects of vacuum annealing with different temperature gradient on 355nm Al2O3/MgF2 HR coatings were investigated. A number of samples had been prepared by electron beam evaporation using the same deposition process at optimal deposition temperature of 280℃. After deposition samples were annealed in the coating chamber for three hours with different temperature gradient. The structure of samples had been characterized by X-ray diffraction (XRD). Laser-induced damage threshold (LIDT) was measured by a 355 nm pulsed laser with a pulse width of 8 ns. Transmittance and reflectance of the samples were measured by Lambda 900 Spectrometer. It is found that different temperature gradient of annealing leads to different structures，LIDT and absorption of samples. Decreasing the temperature gra