DYNAMICS AND SPECTROSCOPY OF INFRARED-TO-VISIBLE UP-CONVERSION IN ERBIUM-DOPED CESIUM CADMIUM BROMIDE (CSCDBR3-ER3+)

Trivalent erbium ions in CsCdBr3 exist predominantly as dimers along one-dimensional lattice chains. Very efficient upconversion from near-infrared to various visible wavelengths was observed. H-2(9/2) --> 4I15/2 (414 nm) and 4F7/2 --> 4I15/2 (493 nm) fluorescence dominated for 4I15/2 --> 4I9/2 (801 nm) and 4I15/2 --> 4I11/2 (984 nm) excitation, respectively. Simultaneous excitation at 801 and 984 nm preferentially populated 4F5/2, giving 4F5/2 --> 4I15/2 (455 nm), 4F5/2 --> 4I13/2 (651 nm), and, by cross relaxation, 4F9/2 --> 4I15/2 (671 nm). The efficiency of multiple-color upconversion is attributed to low phonon energies and close coupling between ions. Upconversion mechanisms are proposed, and energy-transfer rates determined from the temporal transients.