Local structure around Er3+ in Si O2 -Hf O2 glassy waveguides using EXAFS

Er3+ -doped Si O2 -Hf O2 glassy waveguides with Hf O2 concentrations ranging from 10 to 50 mol % were prepared using the sol-gel route and deposited on v-Si O2 substrates using the dip-coating technique. The local environment around Er3+ ions was determined from Er L3 -edge extended x-ray-absorption fine-structure (EXAFS) measurements. The first coordination shell around Er3+ ions is composed of oxygen atoms. Hafnium is the main constituent of the second coordination shell of Er3+, differing from the cases of pure Si O2 and Si O2 -Ti O2 glassy hosts, in which silicon is the main atomic species. The local structure around Er3+ ions has been found to be independent on Hf O2 concentration within the studied composition range. This fact implies that Er3+ ions are preferentially dispersed in Hf O2 -rich regions of the glassy waveguide, even at the lowest Hf O2 concentration. For all samples, no Er3+ - Er3+ coordination shell has been detected by EXAFS. The presented structural results allow us to understand some spectroscopic properties typical of Er3+ -doped Si O2 glassy waveguides co-doped with Hf O2.