Spectral properties and energy transfer in Er3+/Yb3+ co-doped LiYF4 crystal

Abstract:

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.