Spectral properties and energy transfer in Er^(3+)/Yb^(3+) codoped LiYF_4 crystal

Laser crystals of LiYF4 (LYF) singly doped with Er3+ in 2.0% and co-doped with Er3+/Yb3+ in about 2.0%/1.0% molar fraction in the raw composition are grown by a vertical Bridgman method. X-ray diffraction (XRD), absorption spectra, fluorescence spectra and decay curves are measured to investigate the structural and luminescent properties of the crystals. Compared with the Er3+ singly doped sample, obviously enhanced emission at 1.5 μm wavelength and green and red up-conversion emissions from Er3+/Yb3+ co-doped crystal are observed under the excitation of 980 nm laser diode. Meanwhile, the emission at 2.7 μm wavelength from Er3+ singly doped crystal is reduced. The fluorescence decay time ranging from 18.60 ms for Er3+ singly doped crystal to 23.01 ms for Er3+/Yb3+ co-doped crystal depends on the ionic concentration. The luminescent mechanisms for the Er3+/Yb3+ co-doped crystals are analyzed, and the possible energy transfer processes from Yb3+ to Er3+ are proposed.

Laser crystals of LiYF4 （LYF） singly doped with Er3＋ in 2.0% and co-doped with Er3＋/yb3＋ in about 2.0%/1.0% molar fraction in the raw composition are grown by a vertical Bridgman method. X-ray diffraction （XRD）, absorption spectra, fluorescence spectra and decay curves are measured to investigate the structural and luminescent properties of the crystals. Compared with the Er3＋ singly doped sample, obviously enhanced emission at 1.5 um wavelength and green and red up-conversion emissions from Er3＋/Yb3＋ co-doped crystal are observed under the excitation of 980 nm laser diode. Meanwhile, the emission at 2.7/am wavelength from Er3＋ singly doped crystal is reduced. The fluorescence decay time ranging from 18.60 ms for Er3＋ singly doped crystal to 23.01 ms for Er3＋/Yb3＋ co-doped crystal depends on the ionic concentration. The luminescent mechanisms for the Er3＋/Yb3＋ co-doped crystals are analyzed, and the possible energy transfer processes from Yb3＋ to Er3＋ are proposed.