Upconversion luminescence of Er3+ in highly transparent YAG ceramics

Transparent Er3+ doped YAG ceramic was prepared by the vacuum sintering technique. Scanning electron microscope and transmission electron microscope measurements reveal that the pore volume in our sample is approximately 1 ppm, the average grain size is about 10 μm and the grain boundary width is about 1 nm. With the excitation of a 960 nm laser diode, intense green and red upconversion emissions were observed in our sample. Based on the intensity dependence of the upconversion emissions on the pump power, the upconversion mechanisms were discussed.