Study of Al2O3/MgF2 HR coatings at 355Â nm

With the present work we tried to study the effective methods to improve the laser-induced damage threshold (LIDT) and reflectance of HR coatings at 355 nm. The work presented in this paper was part of an ongoing study about vacuum annealing. It was dedicated to study the effects of vacuum annealing with different temperature gradients on the structure, optical properties and laser-induced damage threshold (LIDT) of 355 nm Al2O3/MgF2HR coatings. A number of samples were prepared by electron beam evaporation using the same deposition process with an optimal deposition temperature of 280 °C. After deposition, samples were annealed in the coating chamber for 3 h with different temperature gradients. Morphologies of the samples were observed by Leica-DMRXE Microscope. Structure of the samples had been characterized by X-ray diffraction (XRD). Transmittance and reflectance of the samples were measured by Lambda 900 Spectrometer. The LIDT of the samples was measured by a 355 nm Nd:YAG laser with a pulse width of 8 ns. It was found that the temperature gradient of vacuum annealing had significant effects on the morphology, structure, absorption, and LIDT of the samples.