Spectroscopic Investigation of Yb-doped Silica Glass for Solid-State Optical Refrigeration

We have argued that a high-purity Yb-doped silica glass can potentially be cooled via anti-Stokes fluorescence optical refrigeration. This conclusion is reached by showing, using reasonable assumptions for the host material properties, that the non-radiative decay rate of Yb ions can be made substantially smaller than the radiative decay rate. Therefore, an internal quantum efficiency of near unity can be obtained. Using spectral measurements of the fluorescence emission from a Yb-doped silica optical fiber at different temperatures, we estimate the minimum achievable temperature in Yb-doped silica glass for different values of internal quantum efficiency.