Highly efficient saturated visible up-conversion photoluminescent Y2O3:Er3+ microspheres pumped with a 1.55 μm laser diode

Highly efficient saturation up-conversion (UC) luminescent Y2O3:Er3+ microspheres have been successfully prepared via a hydrothermal-homogeneous precipitation method. Bright visible luminescence can be clearly seen with a 1.55 μm laser diode excitation power as low as ∼0.03 W cm−2. The up-conversion (UC) emission spectra indicate that the strongest red emission with a peak situated at ∼660 nm originated from the 4I9/2 → 4I15/2 transition of Er3+. The peaks situated at ∼520 and 550 nm can be assigned to the transition from 2H11/2/4S3/2 state to the ground state of Er3+. The high efficient saturation up-conversion emission is related to the highly crystalline structure. These results indicate a new way to enhance UC radiation in rare-earth ion-doped materials prepared using a hydrothermal-homogeneous precipitation method.