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

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.