Thermal and spectroscopic characterization of copper and erbium containing aluminophosphate glass

Thermal, Raman scattering, optical absorption, and photoluminescence characterizations were carried out on aluminophosphate glass containing Cu⁺/Cu²⁺ along with near-infrared (IR) emitting Er³⁺ ions of interest to photonic applications. Material synthesis was carried out by the melt-quench technique wherein Cu⁺ ions were incorporated at a high concentration by addition of 10 mol% of Cu₂O together with SnO. The copper oxide doping was recognized to result in a decrease of the glass transition temperature of the matrix, however Er³⁺ doping displayed opposite propensity. Raman measurements under 785 nm excitation were consistent with calorimetry data indicating that copper ions modify glass structural features. The degree of copper oxidation during material preparation was assessed quantitatively through the Cu²⁺ absorption feature around 850 nm. The presence of substantial Cu⁺ concurred with the significant red shift in the near-ultraviolet glass absorption edge, and was analyzed in the context of optical band gap determinations. An evaluation of the luminescence decay kinetics of Cu⁺ ions in the presence of Er³⁺ agreed with a non-radiative energy transfer which appeared more effective for excitation of Cu⁺ near the glass absorption edge at 400 nm. Such excitation was confirmed to result in the sensitized near-IR emission from Er³⁺ ions around 1.53 μm of interest to lasers, the telecommunications, and spectral conversion in photovoltaic cells.