Enhanced three-photon near-infrared quantum splitting in β-NaYF4:Ho3+ by codoping Yb3+

An efficient three-step sequential three-photon near-infrared (NIR) quantum splitting (QS), involving the emission of three NIR photons from an absorbed ultraviolet (UV) photon in β-NaYF4:Ho3+, has been demonstrated. Codoping Yb3+ can increase the NIR emissions significantly through the first- and second-step cross-relaxation. The involved mechanisms of three-step NIR QS in Ho3+-Yb3+ have been well demonstrated by the static and dynamic photoluminescence, monitored excitation and time-resolved fluorescence spectra. An internal quantum yield (QY) of 246% for the Yb3+ codoped β-NaYF4:Ho3+ is estimated on the basis of experimental data and theoretical considerations, which is much more than the total QY of 124% for the β-NaYF4:Ho3+ three-photon NIR QS. This research may open up promising new perspectives for designing efficient photonic devices.