Excited state relaxation dynamics and up-conversion phenomena in Gd3(Al,Ga)5O12 single crystals co-doped with erbium and ytterbium

Single crystals of Gd3(Al,Ga)5O12 (GAGG) doped with Er3+ or Yb3+ ions and co-doped with Er3+ and Yb3+ ions were grown successfully by the Czochralski technique. Their optical properties were investigated in detail. Rates of radiative transitions, branching ratio values and radiative lifetimes for excited multiplets of incorporated Er3+ were determined based on the Judd-Ofelt treatment of optical absorption spectra recorded at room temperature. Obtained parameters Ωt (t=2, 4, and 6) are 1.47×10−20 cm2, 1.38×10−20 cm2, and 1.19×10−20 cm2 respectively. Low energy crystal levels of Er3+ in GAGG were determined employing absorption and luminescence spectra recorded at 5 K. Consequently, the energy diagram constructed was used to substantial discussion of obtained experimental data. Up-conversion of infrared radiation at 980 nm into visible emission in crystals co-doped with erbium and ytterbium was observed and discussed. It was concluded that gathered spectroscopic data point at the potential of the GAGG:Yb3+, Er3+ system for application as a laser active material operating around 1500 nm within the 4I13/2→4I15/2 transition of Er3+.