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.