Photoconductivity in Yb-doped oxides at high excitation densities

Photoconductivity has been found in the dielectric laser materials Yb3+:YAG and Yb3+:Lu2O3 under 940 nm irradiation with an unexpected high photocurrent up to several 100 nanoampères. The nonlinear intensity dependence points to the occurrence of a cooperative upconversion mechanism with 2–3 excited Yb3+-ions in YAG and 2 excited Yb3+-ions in Lu2O3 being involved. According to the results two tentative models of this upconversion process are discussed.