Effect of curing temperature on green light emission from Er3+-doped sol-gel silica glass

Green and less intense red emissions from Er3+ (4f(11))-doped sol-gel silica samples (prepared from tetraethylorthosilicate at room temperature and dried at 70 degrees C) under 488 nm excitation were monitored as a function of sample curing temperature. These green and red emission bands, centered at 550 and 660 nm, are the S-4(3/2) --> I-4(15/2) and F-4(9/2) --> I-4(15/2) transitions in Er3+ ions, respectively. The emission intensities were found to increase with increasing sample curing temperature ranging from 200 to 1000 degrees C. Green upconversion emission from Er3+ ions in the same samples was also recorded under 647.1 nm light excitation. Its efficiency was enhanced with increased sample curing temperature. This enhancement is attributed to the Er3+-coordination environment produced by different sample curing temperatures. Increasing curing temperatures produces increasing degrees of dehydration and de-alcoholation around the Er3+ ions, thus resulting in a decrease in the non-radiative emission rate.