Proton irradiation robustness of dielectric mirrors for high-finesse Fabry-P\'erot resonators in the near-infrared spectral range

TL;DR

This study shows that dielectric mirrors used in high-finesse Fabry-Pérot resonators maintain their optical quality with less than 5% finesse degradation after proton irradiation simulating space conditions, indicating robustness for space applications.

Contribution

It provides the first experimental evidence of the robustness of dielectric mirrors under proton irradiation comparable to space mission environments.

Findings

Less than 5% change in finesse after irradiation.

No impact on coupling efficiency (~70%).

Irradiation spectrum mimics 5-year space mission conditions.

Abstract

We demonstrate that a proton irradiation with fluences of $3.6\times10^{10}$/cm$^{2}$ at low energy ($<$ 36 MeV) and $1.46 \times 10^{10}$/cm$^{2}$ at high energy (40 MeV and 90 MeV combined) on the dielectric mirrors of Fabry-P\'erot 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 [\url{http://sci.esa.int/ste-quest/}].