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

Green and less intense red emissions from Er³⁺ (4f¹¹)-doped sol-gel silica samples (prepared from tetraethylorthosilicate at room temperature and dried at 70°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 ⁴S_3/2 → ⁴I_15/2 and ⁴F_9/2 → ⁴I_15/2 transitions in Er³⁺ ions, respectively. The emission intensities were found to increase with increasing sample curing temperature ranging from 200 to 1000°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.