Effect of OH– on fluorescence properties in 1.5–1.6 μm for Er:Yb:YCOB crystal

Abstract

FTIR absorption spectra indicate that H+ can easily enter the crystal structure and form OH– centers in Er:Yb:YCOB and OH bonds prefer to lie in the a-c plane. Within our current studied concentration level, crystal samples with higher OH– absorption coefficients demonstrate stronger fluorescence intensity and longer fluorescence lifetime at 1535 nm. As the stretching vibration energy of OH– group approximately corresponds to the energy gap between the 4I11/2 and 4I13/2 levels of Er3+, and thus, OH– ions can shorten the fluorescence lifetime of Er3+-4I11/2 level by the phonon-assisted cross-relaxation process between the Er3+ and OH– ions. Our current results confirm that a certain content of OH– ions can enhance the energy transfer process from Yb3+ to Er3+ and subsequently promote fluorescence output in 1.5–1.6 μm.