Comparative study of Ho:Y$_2$O$_3$ and Ho:Y$_3$Al5O$_{12}$ transparent ceramics produced from laser-ablated nanoparticles

International audienceHo:Y2O3 and Ho:Y3Al5O12 transparent ceramics are fabricated by vacuum sintering at 1780 °C for 20 h from laser-ablated nanopowders (Ho:Y2O3 and Ho:Y2O3 + Al2O3) using ZrO2 and TEOS as sintering aids, respectively. The sesquioxide ceramic exhibits smaller grain size (∼5.4 μm), smaller content of pores (down to 6 ppm) and higher optical transmission (up to 82.2% at ∼1 μm) than the garnet one. A detailed comparative spectroscopic study of the two ceramics is performed. For the 5I7 → 5I8 Ho3+ transition, the maximum stimulated-emission cross-sections and the luminescence lifetimes are σSE = 0.57 × 10−20 cm2 at 2087.1 nm and τlum = 10.92 ms (for the Ho:Y2O3 ceramic) and σSE = 1.70 × 10−20 cm2 at 2090.8 nm and τlum = 7.04 ms (for the Ho:Y3Al5O12 one) The rates of multiphonon relaxation are determined for both ceramics. For the Ho:Y2O3 ceramic, they do not exceed those for single-crystals. The crystal-field splitting of Ho3+ multiplets (5I7 and 5I8) is determined at 12 K and analyzed using the barycenter plot. Due to its broadband emission properties, the Ho:Y2O3 ceramic is suitable for mode-locked lasers emitting above 2 μm