Effect of annealing on microstructure and laser-induced damage threshold of ZrO2 Coatings

ZrO2 coatings were deposited on different substrates of Yb∶YAG and fused silica by electron beam evaporation. After annealed for 12 hours at 673 K and 1 073 K respectively, weak absorption of coatings was measured by surface thermal lensing, and then laser-induced damage threshold was determined. The crystalline phase of ZrO2 coatings and the size of the crystal grain were investigated by X-ray diffraction. It is found that microstructure of ZrO2 coatings is dependent on both annealing temperature and substrate structure, anneal at high temperature helps to produce monoclinic phases, and coatings containing monoclinic phases have higher damage threshold than others. Due to the strong absorption of Yb∶YAG, damage threshold of coatings on Yb∶YAG is much less than that on fused silica.