Radial distribution of proton-induced effects in erbium-doped optical fibers: micro-luminescence study

We compare the visible and infra-red luminescence spectra obtained by a green (514.5 nm) and infra-red (830 nm) excitation of an erbium-doped fiber before and after irradiation with 105 MeV protons to an equivalent dose of 0.6 kGy(Si). For the irradiated fiber, we measured an increase of the luminescence intensity in this wavelength range due to the generation of additional color centers. Radiation defects such as Ge-NBOHC, Si-NBOHC are generated in both the fiber core and the cladding by the 105 MeV protons. They contribute through their luminescence bands at 1.84 eV (FWHM=0.2 eV) and 2 eV (0.2 eV) to the fiber emission spectra. Two other pre-existing luminescence bands at 1.75 eV (0.32 eV) and 2.1 eV (0.37 eV), associated to host-matrix-point-defects, are enhanced by proton-irradiation. The Er³⁺ ions luminescence in both visible and infra-red spectral ranges is also affected by the irradiation.