Enhanced 1.53 μm emission of Er³⁺ ions in phosphate glass via energy transfer from Cu⁺ ions

Optimizing the efficiency of Er³⁺ emission in the near-infrared telecommunication window in glass matrices is currently a subject of great interest in photonics research. In this work, Cu⁺ ions are shown to be successfully stabilized at a high concentration in Er-containing phosphate glass by a single-step melt-quench method, and demonstrated to transfer energy to Er³⁺ thereby enhancing the near-infrared emission about 15 times. The spectroscopic data indicate an energy conversion process where Cu⁺ ions first absorb photons broadly around 360 nm and subsequently transfer energy from the Stokes-shifted emitting states to resonant Er³⁺ absorption transitions in the visible. Consequently, the Er³⁺ electronic excited states decay and the ⁴I_3/2 metastable state is populated, leading to the enhanced emission at 1.53 μm. Monovalent copper ions are thus recognized as sensitizers of Er³⁺ ions, suggesting the potential of Cu⁺ co-doping for applications in the telecommunications, solar cells, and solid-state lasing realizable under broad band near-ultraviolet optical pumping.