Intense Upconversion Luminescence of Yb3+-Er3+ in Li2O Content Tungsten-tellurite Glasses

The Er3+ -Yb3+ codoped in Li2O content tungsten -tellurite (TWL) transparent glasses are synthesized and measured the absorption, Raman and upconversion luminescence (UPL) spectra. At room temperature intense green emission peak at 560 nm ( S-4(3/2)-> I-4(15/2)) and red emission peak at 670 nm ( F-4(9/2)-> I-4(15/2)) of Er3+ observed even at minimum 86 mW pumping power of infrared 980 nm excitation. For structure of the TWL glass, Raman spectrum result revealed that an important role of WO3 in the formation of glass network linkage with Li2O. Under this influence estimated lifetime of the I-4(11/2) of Er3+ was 1.89 mu s and due to lower phonon energy of the glass produce strong upconversion signal. The effect of Er2O3 concentration on emission intensity result indicated that green emission intensity initially increase in compare to red emission. Under the 980 nm pump power variation measured the relatively increases the red emission to the green emission intensity and analyze the possible upconversion mechanism and process.