Unexpected behavior of the 1.54 μm luminescence in Er-doped silica films

• We deposited by PVD Er-doped SiO2 films 1 μm thick with different Er concentration.
• Photoluminescence at 1.54 μm was measured after annealing in the 50–1200 °C range.
• At low annealing temperature, 1.54 μm activity was detected for low Er content.
• The 1.54 μm activity could be related to the SiO2 polymorphs formation.
• The region around Er influencing the 1.54 μm signal has possibly few nm of size.

Materials such as Er:glass are still of great interest in optical communication technology for their applications in photonic devices operating at the standard telecommunication wavelengths. The 1.54 μm emission properties of the Er3 + ions embedded in glassy systems depend on several factors, as for instance the synthesis technique and the thermal history of the material. A photoluminescence investigation, made on Er:SiO2 thin films deposited by PVD for a wide range of different Er concentration and subsequently annealed in the range 50–1200 °C (with 50 °C step), was done to investigate in which way both Er concentration and thermal annealing influence the 1.54 μm emission performance of the Er:SiO2 glass system. For low Er concentration, we evidenced an unexpected 1.54 μm activity also after annealing at temperatures much lower than the usual ones. We suspect that this behavior could be related to the medium/long-range order around the Er3 + ions, as a possible consequence of local silica polymorphs formation.