Upconversion luminescence in Er~(3+) doped and Er~(3+)/Yb~(3+) codoped zirconia and hafnia nanocrystals excited at 980 nm

摘要

Frequency upconversion (UC) luminescence in nanocrystalline zirconia (ZrO_2) and hafnia (HfO_2) doped with Er~(3+) and Yb~(3+) was studied under continuous-wave excitation at 980 nm. Samples of ZrO_2:Er~(3+), ZrO_2:Er~(3+)/Yb~(3+), and HfO_2:Er~(3+)/Yb~(3+) were prepared by the sol-gel technique and characterized using x-ray diffraction and electron microscopy. A study of the infrared-to-green and infrared-to-red UC processes was performed including the analysis of the spectral and the temporal behavior. The mechanisms contributing to the UC luminescence were identified as excited state absorption and energy transfer among rare-earth ions.