Spectroscopic properties of CuO, SnO, and Dy₂O₃ co-doped phosphate glass: From luminescent material to plasmonic nanocomposite

Prospective applications of noble metal and rare-earth co-doped dielectrics in optical devices demand for a comprehensive understanding of the influence of material composition and processing on resulting properties. In this study, we report on the spectroscopic properties of a 50P₂O₅:50BaO glass matrix containing copper, tin, and dysprosium prepared by melting and subsequently subjected to heat treatment (HT). An achievement in terms of material preparation is that addition of stoichiometric amounts of CuO and SnO dopants along with the source of Dy³⁺ ions (Dy₂O ₃) is shown effective for the precipitation of Cu nanoparticles (NPs) during HT. Optical absorption and photoluminescence (PL) spectroscopy including emission decay dynamics are employed in the characterization of the co-doped material as prepared, and as a function of HT. The basic structure of the phosphate host is assessed by ³¹P nuclear magnetic resonance spectroscopy. The optical data suggests the presence of both Cu²⁺ and Cu⁺ ions in the melt-quenched co-doped glass together with the Dy³⁺ ions. Thermal processing is indicated to result in the chemical reduction of ionic copper species via Sn²⁺ and ultimately produces the non-luminescent plasmonic Cu particles. The presence of such NPs is also observed to produce a quenching effect on Dy³⁺ PL, interpreted in terms of an ion-to-particle excitation energy transfer operating via interband transitions in the nanoscale metal. Thus, the glass may act as either a luminescent material or a plasmonic nanocomposite desirable for nonlinear optics dependent upon its thermal history.