Proton irradiation robustness of dielectric mirrors for high-finesse Fabry-Pérot resonators in the near-infrared spectral range

We demonstrate that a proton irradiation with fluences of 3.6 × 1010/cm2 at low energy (<36 MeV) and 1.46 × 1010/cm2 at high energy (40 and 90 MeV combined) on the dielectric mirrors of Fabry-Pérot cavities with a finesse of about 700,000 causes less than 5 % change in the finesse. Furthermore, no influence on the coupling efficiency to the cavities was observed, the efficiency being approximately 70 %. The irradiation was carried out with a spectrum approximating the proton energy spectrum of a highly elliptic Earth orbit with duration of 5 years, proposed for the Space-Time Explorer and Quantum Equivalence Space Test (STE-QUEST) mission [http://sci.esa.int/ste-quest/].