Up-conversion emission in triply-doped Ho3+/Yb3+/Tm3+ KGd(WO4)2 single crystals

► Triply doped KGd(WO4)2:Ho3+/Yb3+/Tm3+ single crystals were grown. ► The up-converted emission spectra were studied in details. ► Efficient multi-colored emission of Ho3+ and Tm3+ ions was observed. ► Dependence of the up-converted luminescence intensity on the excitation power was studied.