Sensitized red emission from Mn2+ ions in phosphate glass via silicon-induced defects

This paper reports on the sensitization of the red Mn2+ emission in phosphate glasses via luminescent defects induced by silicon. Glasses of barium-phosphate matrix were prepared by melting and analyzed by X-ray diffraction, Fourier transform-infrared spectroscopy, optical absorption , and photoluminescence spectroscopy with focus on decay dynamics and time-resolved assessment. A comparative investigation was performed with singly-MnO2 doped glasses within 4–8 mol% and counterparts which were also co-doped with Si powder in the same amount. Silicon co-doping resulted in: ( i ) improved UV transparencies; ( ii ) significant reduction of MnO2 facilitating Mn2+ stabilization; and ( iii ) the formation of luminescent defects with emission overlapping Mn2+ excitation (e.g. 6A1(S) → 4E(G),4A1(G) transitions around 410 nm). Consequently, the Si-induced defects gave rise to a new Mn2+ excitation band around 270 nm leading to the red 4T1(G) → 6A1(S) band emission from Mn2+ ions. The decay kinetics of the defects as well as the Mn2+ ions were analyzed via time-resolved measurements aiming to elucidate the physical interactions. A UV-to-visible down-conversion pathway originating at Si-related defects is ultimately proposed.