Anti-Stokes cooling of Yb-doped KYF4 single crystals

Truly vibration-free, optical cooling of solids, relying on annihilation of lattice phonons via anti-Stokes fluorescence, is a rapidly advancing technology with a huge potential impact on a variety of space and terrestrial applications. In this paper, we focus on investigation of active media and we report on the first observation of anti-Stokes cooling in a novel material, a Yb-doped KYF4 single-crystal, promising in relation to its multi-site structure and low phonon cut-off energy. The cooling efficiency of the sample was measured, external quantum efficiency and background absorption were evaluated and compared to other fluoride active media. Bulk cooling by similar to 1.8 degrees C was observed under similar to 1.5 W laser excitation, tuned close to 1025 nm, in single-pass configuration.