Energy Transfer and 1.8 µm Emission in Tm³âº/Yb³âº Co-Doped LiYF4Crystal.

LiYF4 single crystals co-doped with various Tm³âº/Yb³âº concentrations were grown using the Bridg- man method. The luminescent properties of the crystals were investigated through emission spectra, emission cross section, and decay curves under excitation by 980 nm. Compared with the Tm³âº single-doped LiYF4 crystal, an enhanced emission band from 1600 to 2150 nm was observed upon excitation of a 980 nm laser diode. The energy transfer from Yb³âº to Tm³âº and the optimum fluo- rescence emission around 1.80 µm of Tm³âº ion were investigated. The maximum emission cross section at 1.8 µm was calculated to be 1.48 x 10⁻²° cm² according to the measured absorption spectrum. The high energy transfer efficiency of 86.5% from Yb³âº to Tm³âº ion demonstrate that the Yb³âº ions can efficiently sensitize the Tm³âº ions.