Author/Authors :
Chen، نويسنده , , G.Y. and Liu، نويسنده , , Y. and Zhang، نويسنده , , Z.G. and Aghahadi، نويسنده , , B. and Somesfalean، نويسنده , , G. and Sun، نويسنده , , Q. and Wang، نويسنده , , F.P.، نويسنده ,
Abstract :
Room-temperature blue and violet upconversion (UC) emissions of Er3+ at 409 nm (2H9/2 → 4I15/2) and 390 nm (4G11/2 → 4I15/2) were observed in Y2O3:Yb3+–Er3+ nanocrystals by diode laser excitation of 980 nm. At low Yb3+ concentration both wavelengths result from three-photon UC processes. Unexpectedly, a four-photon and a decreased three-photon UC processes were observed at high Yb3+ concentration for the violet and the blue emissions, respectively. The four-photon process supposably results from the cross relaxation 4D7/2 + 4I15/2 → 4G11/2 + 4I13/2 of Er3+ ions with the 4D7/2 state populated by the 22F5/2(Yb) + 4F9/2(Er) → 22F7/2(Yb) + 4D7/2(Er) process, whereas the decreased photon process arises from the larger UC rate at high Yb3+ concentration.
