Strategies to increase laser damage performance of Ta_2O_5/SiO_2 mirrors by modifications of the top layer design

Abstract

Ta₂O₅/SiO₂ high reflection (HR) interference coatings for λ∼1 μm offer superior performance at high irradiance conditions. However, these coatings are not good candidates for high peak power conditions in comparison to HfO₂/SiO₂ multilayer stacks. Here we show that the modification of the top layers design of a quarter wave Ta₂O₅/SiO₂ high reflector leads to 4-5 fold increase in the laser damage fluence compared to a quarter wave (Ta₂O₅/SiO₂)¹⁵ when tested at λ=1.03 μm using pulse durations of 0.19 and 4 ns and peak power densities of 43.5 and 216 GW/cm². One of the designs achieved a laser damage threshold fluence of 174 J/cm² at 4 ns, which is 10% higher than that of a HfO₂/SiO₂ quarter wave design.