Red-to-green up-conversion in Er-doped SiO2 and SiO2-TiO2 sol-gel silicate glasses

Monolithic Er-doped SiO2-TiO2 binary glasses of high optical quality were used in an investigation of the effects of different annealing conditions and titanium content on fluorescence yields and decay times of the S-4(3/2) level of Er3+. In addition, the characteristics of green upconverted fluorescence from the S-4(3/2) level via excitation with red laser light (655 nm) were studied. Energy transfer up-conversion involving two ions in the I-4(11 2) state was determined to be the dominant up-conversion mechanism. The glasses with TiO2 showed enhanced up-conversion and required lower annealing temperatures for the up-conversion to be observed when compared to SiO2 glasses doped with Al. (C) 2001 Elsevier Science BN. All rights reserved.