Up-conversion of SrF2:Ho3+and SrF2:Ho3+/Yb3+powders under 1940 nm laser excitation
Fluorescent powders of SrF2:Ho3+and SrF2:Ho3+/Yb3+were prepared using high-temperature solid-state reaction method. The up-conversion luminescence of SrF2:Ho3+and SrF2:Ho3+/Yb3+was observed under 1940 nm laser excitation,and visualization of 2 μm laser was performed. The crystal structure of the sample was tested by XRD. The introduction of certain amount of Pb2+and rare earth Ho3+(Yb3+) into SrF2 does not change the crystal structure,but the up-conversion performance of Ho3+ions was improved. Under appropriate Pb2+concentration doping,the up-conversion intensity of the sample can be increased by up to 18.8％. The effect of Ho3+ion concentration on the up-conversion luminescence was studied in an optimized SrF2 substrate. With the increase of Ho3+concentration,the luminescence intensity first increases and then decreases,and the optimal molar concentration of Ho3+ion is 0.054. Based on this result,Yb3+ions were further doped to achieve color control of the upconversion emission light. As the doping of Yb3+ions increases,the green emission at 545 nm gradually increases,and the upconversion color also changes from red to yellow. Based on the spectral performance of the up-conversion,the mechanism of the up-conversion luminescence and the process of energy transfer were discussed. It is suggested that the prepared up-conversion material has potential in near-infrared laser detection at around 2 μm.
up-conversionrare earthIR visualizationenergy transfer
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