Optical spectroscopy of Cu⁺/Sm³⁺-activated aluminophosphate glasses: Effect of Cu²⁺ impurities on the Sm³⁺ photoluminescence enhancement

Glasses containing Cu⁺ and Sm³⁺ ions are attractive as luminescent materials with potential for various photonic applications. Yet, the limiting effect of the non-luminescent Cu²⁺ impurities on the activated glasses remains unexplored. In this work, Cu/Sm-containing aluminophosphate glasses are prepared by a simple melt-quench method utilizing divalent tin as aid for incorporating relatively large quantities of monovalent copper. The influence of resultant ionic copper species (Cu⁺ and Cu²⁺) on Sm³⁺ photoluminescence (PL) is evaluated. Optical absorption spectroscopy is employed for estimating residual Cu²⁺ in Cu/Sm-containing glasses via spectrophotometric analysis, aimed for assessing the effect of Cu²⁺ impurities on Sm³⁺ emission. PL spectroscopy data is consistent with a sensitized Sm³⁺ emission due to the presence of Cu⁺ ions. However, with increasing concentration of copper dopant, the degree of PL enhancement exhibits a decrease which correlates with an increase in Cu²⁺ concentration. Moreover, analysis of the Sm³⁺ emission decay dynamics shows a strong correlation between the decay rates and residual Cu²⁺. The data indicates that Cu²⁺ ions are at the origin of the suppression of the PL enhancement and perform effectively as Sm³⁺ emission quenchers. Results imply that for practical applications the Cu²⁺ impurities should be minimized if not removed as these will limit device efficiency. Furthermore, the findings suggest a potential of samarium (III) for optical sensing of copper (II) which could be further exploited analytically.