The sol-gel process has been employed to prepare highly doped Er3+ silica glasses, up to 5-wt% for homogeneous doping distribution. The optical characteristics of the silica glasses including the UV/VIS absorption and fluorescence emission spectra under excitation of 488 nm and 520 nm lights were measured. Micro-Raman spectra of these silica glasses heated at different temperatures from 200 degree(s)C to 1100 degree(s)C under 632.8 nm laser beam excitation of the He-Ne laser also recorded. The green up conversion emission from Er3+ ion doped into the silica glasses heated to 1000 degree(s)C under red light (632.8 nm) excitation has been observed. Two green and weak emission bands, centered at 525 and 550 nm, for the 2H11/2 yields 4I15/2 and 4S3/2 yields 4I15/2 transitions, respectively, have been observed. The blue upconversion emission er3+ at 300 K centered at 460 nm was observed rather strength depends on the He-Ne laser pump powers and the Er3+ concentration. The pump wavelength is far from any electronic absorption from the ground state of the Er3+ ion, but corresponds to the excited state absorption. This upconversion process was interpreted by the excited state absorption and an upconversion mechanisms is proposed.
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