Performance of Yb- versus Tm-doped fiber lasers for anti-Stokes fluorescence cooling in space

This study compares two fiber-laser oscillator solutions, one operating at 1020 nm with an Yb-doped gain medium and the other at 2070 nm based on a Tm-doped gain medium, in the context of anti-Stokes fluorescence cooling of Yb:YLF or Ho:YLF crystals placed aboard a low-Earth-orbit satellite. We measured the radiation-induced attenuation (RIA) in a passive configuration on both Yb-doped and Tm-doped single-mode fibers for a cumulated dose of 100 Gy. Incorporating the RIA values into laser-oscillator simulations and coupling these results with an electrical-to-optical efficiency analysis, we show that the 2070 nm Tm-based system can achieve a higher cooling efficiency.