Upconversion luminescence in Tm3+/Yb3+ co-doped double-clad silica fibers under 980 nm cladding pumping

An investigation is reported of the visible and near-infrared upconversions in Tm3+/Yb3+ co-doped double-clad silica fibers (TYDFs) under excitation at 980 nm. The TYDFs used were fabricated using the modified chemical vapor deposition (MCVD) and solution doping techniques. Three distinct upconversion luminescences were observed at wavelengths of 482, 649 and 816 nm and their intensities found to increase with Yb3+ concentration. The intensity of blue and red fluorescence bands at 482 and 649 nm were found to be the highest with LTY-8 fiber, which had Tm3+ and Yb3+ concentrations of 5.6 x 10(19) and 15.5 x 10(19) ions/cc, respectively. The upconversion luminescence intensity was also observed to decrease with an increase in temperature. The main emission switched from 482 nm to 816 nm as the temperature increased above 200 degrees C