Optical spectroscopy of Pr3+ ions in sol-gel derived GeO2-SiO2 planar waveguides

A GeO2-SiO2 planar waveguide, activated with 1% mol Pr3+, has been prepared using a dip-coating technique. The GeO2-SiO2 film was deposited on a substrate consisting of a silicon wafer with a silica buffer layer. After annealing at 800 °C and 900 °C the waveguide luminescence and Raman spectra were measured. The Raman spectra show that complete densification is achieved after annealing at 800 °C. Analysis of the emission spectra and the decay curves from the 3P0 and 1D2 states of Pr3+ indicates that the non-radiative relaxation due to the rare-earth clustering is less important than in massive silica xerogels.