Effect of Yb co-doping on the spectral properties of Er:YVO4 single crystal: A Judd Ofelt analysis

Abstract

Single crystals of 0.7 at% Er:YVO4 co-doped with varied concentrations of Yb (1.5, 3.0 and 8.0 at%) were grown by optical floating zone technique. The absorption spectra of the grown crystal are characterized by the prominent absorption at 985 nm due to Yb ion and multiple absorption due to Er ions. The overall characteristic absorption for π-polarization (E||c) is stronger than that for σ-polarization (E┴c) due to alignment of dipole moments along c-direction. The line strength of all the transitions of Er ions decreases as the doping concentration of Yb increases. Judd Ofelt parameter Ω2, which strongly depends on the environment of ligand, decreases with increasing Yb concentration in the lattice. The value of spectroscopic quality factor was found to be nearly invariant (~ 1.80) with respect to the Yb doping concentration but better than that for Er doped YVO4 (~1.31) [1]. The radiative lifetime and emission cross-section of 4I13/2→4I15/2 transition of Er ions was also found to be independent of Yb doping concentration. This is one of the biggest advantages of Yb co-dopant as a good sensitizer in the Er:YVO4 as it results in high population density in upper level of Er ions making it. The emission cross-section of 4I13/2→4I15/2 line for excitation at 985 nm is ~ 2.33 × 10−20 cm2. Further, the values of emission cross-section for both the excitation at 808 nm (Er absorption line) and 985 nm (Yb absorption line) were found nearly same.