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 O H 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 4 I 11/2 and 4 I 13/2 levels of Er 3+ , and thus, OH – ions can shorten the fluorescence lifetime of Er 3+ - 4 I 11/2 level by the phonon-assisted cross-relaxation process between the Er 3+ and OH – ions. Our current results confirm that a certain content of OH – ions can enhance the energy transfer process from Yb 3+ to Er 3+ and subsequently promote fluorescence output in 1.5–1.6 μm.