Effect of Hf4+ doping on structure and enhancement of upconversion luminescence in Yb:Tm:LiNbO3 crystals<xref rid="cpb_27_11_114217_fn1" ref-type="fn">*</xref><fn id="cpb_27_11_114217_fn1"><label>*</label>Project supported by Special Funds of Harbin Innovation Talents in Science and Technology Research, China (Grant No. 2015RQQXJ045) and Science Funds for the Young Innovative Talents of HUST, China.</fn>

Effect of Hf⁴⁺ doping on structure and enhancement of upconversion luminescence in Yb:Tm:LiNbO₃ crystals**

Project supported by Special Funds of Harbin Innovation Talents in Science and Technology Research, China (Grant No. 2015RQQXJ045) and Science Funds for the Young Innovative Talents of HUST, China.

Dai Li^{1, †}, Liu Chunrui¹, Han Xianbo¹, Wang Luping², Shao Yu¹, Xu Yuheng³

(color online) The energy levels of Yb³⁺ and Tm³⁺ ions as well as the upconversion luminescence mechanism of Hf:Yb:Tm:LiNbO₃ crystals.