Transparent YAG ceramics with Er and Yb co-doping

YAG-based ceramics represent an interesting alternative to single crystals as laser sources for high power systems. Among the various active elements for YAG, Er is essential for obtaining 1.50-1.65 um eye-safe lasers, which are used for example in long-distance telemetry and ranging. Problem of YAG doped only with Er is low laser efficiency due to low absorption of the Er3+ ions, which cannot be improved by increasing Er3+ content. The output efficiency can be enhanced by the introduction of a sensitizer ion into the host material, improving the absorption of the pump source through a direct energy transfer (DT) mechanism. Yb3+ ions absorb the light in the range 900-1100 nm and can therefore be pumped by InGaAs laser diodes and transfer the energy to Er3+ ions by DT from the 2F5/2 level of Yb3+ to the 4I11/2 level of Er3+. In the present work YAG-based ceramic doped with both Yb3+ and Er3+ has been prepared from oxide powders via solid state sintering in high vacuum with TEOS as a sintering aid. Microstructural analyses of the sintered samples have been carried out to determine the dopants distribution, their influence on the sintering process and on the final properties. Special attention has been paid to the optical properties. The absorption and emission spectra and decay times have been measured under different experimental conditions and were compared to those obtained with a single crystal of the same composition. Laser performance was also evaluated. This research program is supported by a bilateral joint project CNRS-France / CNR-Italy.