Enhanced downconversion luminescence of NaLuF4:Yb3+,Er3+ micrometer hexagonal prismatic crystals under 980 nm excitation

NaLuF 4 :Yb 3+ ,Er 3+ micrometer prismatic crystals are potential materials for the preparation of optical waveguide devices. However, structural defects and OH – groups are generated inside and on their surfaces during growth processes. The structural defects and OH – groups lead to a large depletion of excitation energy and severely quench the downconversion luminescence of Er 3+ . In addition, the Yb 3+ /Er 3+ co-doping ratio significantly affects the downconversion luminescence of the microcrystals, which in turn affects the performance of the optical waveguide amplifiers based on the microcrystals. By adjusting the co-doping ratio of Yb 3+ and Er 3+ in the microcrystals and removing the defects in the crystals, their downconversion luminescence performance was significantly improved. The results showed that the downconversion luminescence under the excitation from a 980 nm laser reached the maximum value when the doping ratio of Yb 3+ and Er 3+ was 20:1.5. In addition, the OH – groups and structural defects in the micrometer crystals were significantly eliminated by ion-exchange and high-temperature annealing treatments, and the crystalline quality was significantly improved. After ion-exchange and high-temperature annealing treatments, the downconversion luminescence enhancement of NaLuF 4 :Yb 3+ ,Er 3+ microcrystals was 2.5 times that of the untreated samples.