Up-conversion mechanisms in Er3+ doped YbAG crystals

Up-conversion phenomena leading to the red, green and violet emissions in erbium doped ytterbium-aluminum garnet (YbAG) are investigated. Absorption and emission spectra and luminescence dynamics from various excited states of YbAG:Er3+ were registered. The low temperature absorption spectra were used to determine Stark levels energies of Er3+ ion in the investigated host. Emissions from the high lying excited states 2G9/2, 4S3/2 and 4F9/2 of Er3+ were characterized under pulsed multi-photon IR excitation in the region of wavelength corresponding to the strong 2F7/2 → 2F5/2 absorption transition of Yb3+ ions. Using the rate equations formalism the dynamics of the observed emissions were modeled. From the comparison of the measured and calculated decays the energy transfer rates between Yb3+ and Er3+ ions were evaluated. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)