Design and preparation of white light emission from up-conversion transitions in Er³⁺/Tm³⁺/Yb³⁺ co-doped cubic zirconia single crystals

High-quality cubic YSZ crystals were designed with various contents of Er3+, Tm3+ and Yb3+ to produce white light emission, and grown by the optical floating zone method. The up-conversion luminescence spectra of the crystals under 980 nm laser irradiation show three distinct groups of emission peaks at -473 nm (blue) generated by the Tm(3+ 1)G(4)-> H-3(6) transition, 531 and 547 nm (green) from the Er3+ H-2(11/2) -> I-4(15/2) and S-4(3/2) -> I-4(15/2) transitions, and 640 and 662 nm (red) from the Er3+ F-4(9/2) -> I-4(15/2) transition. The optical power curve obtained by plotting the up-conversion luminescence intensity against the laser power shows that the blue emission involves a three-photon process, whilst both the green and red emissions are the results of two-photon processes. Overall white light emission was observed with the crystal prepared with 0.05 mol% Er2O3, 0.5 mol% Tm2O3 and 2.0 mol% Yb2O3, and this crystal is suitable for use in highly efficient white light emission devices.