Comparative Investigation of Green and Red Upconversion Luminescence in Er ³⁺ Doped and Yb ³⁺ / Er ³⁺ Codoped La OC l

Abstract

Pure tetragonal La OC l: Er 3+ and La OC l: Yb 3+ / Er 3+ samples possessing upconversion ( UC ) luminescence behavior were synthesized using a simple solid‐state reaction method and the structural properties were investigated using X ‐ray diffraction, crystal structure analysis, and SEM, respectively. The UC spectroscopic properties of Er 3+ doped and Yb 3+ / Er 3+ codoped La OC l were studied in terms of UC emission spectra. The intense green and red emissions around 528, 550, and 662 nm corresponding to the 2 H 11/2 →4 I 15/2 , 4 S 3/2 → 4 I 15/2 , and 4 F 9/2 → 4 I 15/2 transitions of Er 3+ ions were observed for La OC l: Er 3+ sample under excitation at 980 nm, and the power studies indicated that two‐photon processes were responsible for the green and red upconversion luminescence. The bright green emission is visible to the naked eyes for La OC l: Er 3+ . A great enhancement of the visible upconversion emissions in Yb 3+ / Er 3+ ‐codoped sample was observed, furthermore, it is interesting to find the bright red emission for La OC l: Yb 3+ / Er 3+ samples. The mechanisms for the green and red UC luminescence, especially the enhancement of red UC emission were discussed based on the law of UC intensity versus pump power and their lifetimes.