Up-conversion in Er3+:Y2O3 Nanocrystals Pumped at 808nm

Er3+ ion-doped Y2O3 nanocrystals were prepared by coprecipitation synthesis technique. Visible emissions at 650, 540, and 523nm have been observed under excitation at 808nm. Comparing with the stokes emission characteristics of the nanocrystals pumped at 488nm, the up-conversion mechanisms excited at 808nm have been investigated in detail. Excitation power dependent behaviors of the up-converted emission intensities indicate that a two-photon excited state absorption process is responsible for the S3∕24(H11∕22)→I15∕24 transition while a no-resonant energy transfer I9∕24+I11∕24→I9∕24+I13∕24 principally performs the red up-conversion of the F9∕24→I15∕24 transition.