Switching of emissivity and photoconductivity in highly doped $Yb3+:Y2O3$ and $Lu2O3$ ceramics

Reversible jump of thermal emission accompanied with jump of photocurrent is observed in highly doped $Yb3+:Y2O3$ and $Lu2O3$ bulk ceramics pumped at $940nm$ wavelength. In contrast, when these materials are heated with a $CO2$ laser at $10.6μm$ wavelength, only a gradual increase of thermal emission and photoconductivity are observed up to the melting point. These results are interpreted as a ytterbium mediated, photoassisted avalanche of thermal emission.