Efficient Energy Transfer and Enhanced Near-IR Emission in Cu⁺/Nd³⁺-Activated Aluminophosphate Glass

The development of photonic materials for efficient energy conversion and high-power solid-state lasers is currently pursued given the wide range of applicable technologies and the possibility to help meet global energy demands in laser fusion power plants. In this work, Cu⁺ ions successfully incorporated in aluminophosphate glass are recognized as near-ultraviolet (UV) sensitizers of Nd³⁺ ions resulting in remarkable near-infrared (IR) ⁴F_3/2 → ⁴I_11/2 emission at 1.06 μm. Optical absorption, solid-state ³¹P nuclear magnetic resonance, Raman, and photoluminescence spectroscopies characterizations are employed and assessment methods for material optical and structural properties are proposed. The spectroscopic data indicates an efficient (>50%) nonradiative energy transfer where the Cu⁺ ions first absorb photons broadly around 360 nm, and subsequently transfer the energy from the Stokes-shifted emitting states to resonant Nd³⁺ energy levels. Then, the Nd³⁺ electronic excited states decay and the upper lasing state ⁴F_3/2 is populated, leading to enhanced near-IR emission. It is suggested that the physico-chemically robust Cu⁺/Nd³⁺ codoped aluminophosphate glass is a suitable candidate as solid-state laser material with enhanced pump range in the near-UV part of the spectrum and for solar spectral conversion in photovoltaic cells.