Synthesis and ultraviolet upconversion fluorescence of Tm³⁺ doped YbF₃ microparticles

Abstract

YbF₃ microparticles doped with Tm³⁺ were synthesised by coprecipitation method, from which intense ultraviolet and blue emission bands are observed under 980 nm excitation. It is found that the upconversion fluorescence intensity of YbF₃:Tm³⁺ synthesised by coprecipitation method is efficiently enhanced comparing with that prepared by solid state reaction method. The dependence of the emission intensity on pumping power was investigated in the Tm³⁺ doped YbF₃. It is believed that two- and three-photon processes perform populations of ¹G₄ and ¹D₂ levels of Tm³⁺ respectively. The dominant upconversion mechanism may be attributed to a cooperative sensitisation process, which makes two Yb³⁺ ions in excited states cooperatively transfer their energy to a Tm³⁺ ion. The dependence of the emission intensity on the concentration of Tm³⁺ was also discussed.

Keywords:

• Tm³⁺
• Cooperative upconversion
• Energy transfer

Acknowledgements

This work was supported by National Natural Science Foundation of China (grant no. NSFC51032002), the key Project of the National High Technology Research and Development Program (‘863’Program) of China (grant no. 2011AA050526) and the Science and Technology Support Plan of Jiangsu Province (grant no. BE2011191).