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Abstract: Er-doped Si-SiO2 and Al–Si-SiO2 films have been deposited by rf-sputtering being annealed afterwards. Annealing behavior of the Er3+: 4I13/2→4I15/2 emission of Er-doped Si-SiO2 yields a maximum intensity for annealing at 700–800°C. 4I13/2→4I15/2 peak emission for Er-doped Al–Si-SiO2 at 1525nm is shifted from that for Er-doped Si-SiO2 at 1530nm and the bandwidth increases from 29 to 42nm. 4I13/2→4I15/2 emission decays present a fast decaying component related to Er ions coupled to Si nanoparticles, defects, or other ions, and a slow decaying component related to isolated Er ions. Excitation wavelength dependence and excitation power dependence for the 4I13/2→4I15/2 emission correspond with energy transfer from Si nanoparticles. Populating of the 4I11/2 level in Er-doped Si-SiO2 involves branching and energy transfer upconversion involving two or more Er ions. Addition of Al reduces the populating of this level to an energy transfer upconversion involving two ions. [Copyright &y& Elsevier]

Abstract: The propagation of an optical beam through dielectric media induces changes in the refractive index, Δn, which causes self-focusing or self-defocusing. In the particular case of ion-doped solids, there are thermal and non-thermal lens effects, where the latter is due to the polarizability difference, Δα, between the excited and ground states, the so-called population lens (PL) effect. PL is a pure electronic contribution to the nonlinearity, while the thermal lens (TL) effect is caused by the conversion of part of the absorbed energy into heat. In time-resolved measurements such as Z-scan and TL transient experiments, it is not easy to separate these two contributions to nonlinear refractive index because they usually have similar response times. In this work, we performed time-resolved measurements using both Z-scan and mode mismatched TL in order to discriminate thermal and electronic contributions to the laser-induced refractive index change of the Nd3+-doped Strontium Barium Niobate (Sr x Ba1− x Nb2O6) laser crystal. Combining numerical simulations with experimental results we could successfully distinguish between the two contributions to Δn. [Copyright &y& Elsevier]

Abstract: Desvitrification in a Tm3+ and Yb3+ codoped oxyfluoride glass has been obtained by exciting with a continuous Argon laser radiation increasing the average laser power from 144 to 2900mW. Excitation spectra inside a locally damaged zone in a 1mol% Tm3+ and 2.5mol% Yb3+ codoped glass have been measured under excitation in the wavelength range 750–830nm detecting the 2F5/2 (Yb3+) level. This curve is the result of the contribution of two different kinds of centers, the fluoride nanocrystals and the glassy phase of the glass ceramic sample created due to the irradiation. The weight of the contributions of each of the centers depends on the excitation wavelength, and from the analysis of the decay of the luminescence it can be concluded that approximately 80% of the Tm3+ ions are located in the nanocrystals and therefore less than 20% in the glassy phase. [Copyright &y& Elsevier]