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 ⁴I_9/2→⁴I_15/2 transition of Er³⁺. The peaks situated at ∼520 and 550 nm can be assigned to the transition from ²H_11/2/⁴S_3/2 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. [ABSTRACT FROM AUTHOR]