Upconversion luminescence mechanisms of Er3+-doped barium gallogermanate glasses

The absorption, Raman and upconversion luminescence spectra of Er3+-doped barium gallogermanate glasses have been measured and the upconversion mechanisms of E3+-doped barium gallogermanate glasses have been analyzed. The absorption and Raman spectra show that barium gallogermanate glasses have the ultraviolet absorption edge of 275 nm and the maximum vibrational energy of 828 cm(-1), respectively. Intense green and red emissions, excited by 800 nm and 980 nm laser diode, were observed at room temperature. With increasing E3+ ion concentration, the green emission increases initially and then decreases, while the red emissions increases monotonicly. Under the excitation of 800 nm laser diode, the green emission is mainly attributed to the excited state absorption from the I-4(13/2) level and the red emission to the energy transfer between the I-4(13/2) level and the I-4(11/2) level. Under the 980 nm laser diode excitation, the green emission mainly originates from the energy transfer between the I-4(11/2) levels and the red emission from the energy transfer between the I-4(13/2) and I-4(11/2) levels as well as the excited state absorption of the I-4(13/2) level. The calculation results of quantum efficiency for different pumping wavelengths show that the upconversion efficiency of the green emission in barium gallogermanate glass with 1 mol % Er3+ ions reaches a maximum value under the excitation of 800 nm laser diode.