Effect of Yb doping on the crystal structure, polarization dependent optical absorption and photoluminescence of Yb:YVO4 single crystal grown by optical floating zone technique

Abstract

Single crystals of Yb doped YVO4 with dopant concentration in the range of 0.75–14.3 at.% were grown by optical floating zone technique. The lattice parameters of YVO4 remain unaffected up to 2.94 at.% doping of Yb but a contraction in the lattice volume was observed at higher concentrations. Spectral decomposition analysis of the broad absorption at 985 nm suggests that in addition to the contributions from three transitions from the ground state of the crystal field induced Stark multiplets of 2F7/2 and 2F5/2, it also has contribution from the transition from the first excited Stark level of 2F7/2 to the upper most Stark level of 2F5/2. Further, the absorption spectra exhibited significant polarization dependence. It was found that while for σ- (E⊥c) polarized light the absorption band at ∼972 dominates for π- (E||c) dominant absorption is at ∼985 nm. The absorption cross-section was found to be maximum at 2.94 at.% of doping for both the polarization signifying quenching at higher concentration. The emission spectra of the Yb doped crystals were characterized by two overlapped broad emissions centered at 985 and 1010 nm. The emission at 985 nm dominated over the emission at 1010 nm at lower doping concentrations which reversed at higher doping concentration. It is interesting to note that the PL intensity at 1010 nm is stronger for excitation at 972 nm in comparison to that for 985 nm.