21 research outputs found
Photobleaching of photodarkening in ytterbium doped aluminosilicate fibers with 633 nm irradiation
No full textIn the present study, we examined photodarkening loss reduction in Yb3+ doped aluminosilicate fibers by utilizing 633 nm light irradiation. It is demonstrated that the final photobleaching value is intensity dependent, but the percentage of photodarkening reduction does not depend on dopant concentrations for settled bleaching intensity. Further examination was committed to explore the photobleaching starting from different photodarkening loss levels while keeping the same dopant concentration and subsequently the other way around. This approach related photobleaching with the number of photodarkening induced color centers and also showed that photobleaching was dopant concentration dependent. In all experiments an unbleachable residual loss for the bleaching powers up to ~100 W/mm2 was found. To the best of our knowledge this is the most extensive investigation of photobleaching effect
Verres fluores a base de metaux lourds : purification, corrosion par l'eau, determination du coefficient d'extinction molaire de OH-
No full textSIGLECNRS T 58259 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc
Self-similarity of time evolution of photodarkening losses induced in Yb-doped fibers and photodarkening figure of merit
No full textIn this paper we report and summarize an extensive investigation of photodarkening in Yb-doped silica fibers. We made a set of similar fibers in order to cover a large Yb concentration range. The results show that once uniform inversion is reached all along the test fiber it is possible to show self-similarity of the time evolutions. The stretching parameter has a little influence. We can therefore provide two unique numbers to define photodarkening performance: the saturation loss and the time scale parameter. We also propose a possible figure of merit to compare different fibers. This may allow to evaluate the impact of photodarkening on laser/amplifier devices
Temporal evolution and correlation between cooperative luminescence and photodarkening in ytterbium doped silica fibers
No full textThe present work describes photodarkening from the viewpoint of cooperative luminescence. The temporal evolution of both effects was measured simultaneously by means of ytterbium doped aluminosilicate fibers for concentrations up to 1.8 wt% Yb3+. The quadratic dependence of photodarkening and cooperative luminescence versus dopant concentration was observed. The change in the photodarkening and cooperative luminescence mutual dynamics for highly and low doped fibers is ascribed to a different ion number which forms the cluster. Cooperative luminescence is proved to be a natural probe for photodarkening since it provides new pieces of information and contributes to the photodarkening mechanism descriptio
Concentration dependence and self-similarity of photodarkening losses induced in Yb-doped fibers by comparable excitation
No full textWe report on an extensive investigation of photodarkening in Ybdoped silica fibers. A set of similar fibers, covering a large Yb concentration range, was made so as to compare the photodarkening induced losses. Careful measurements were made to ensure equal and uniform inversion for all the tested fibers. The results show that, with the specific set-up, the stretching parameter obtained through fitting has a very limited variation. This gives more meaning to the fitting parameters. Results tend to indicate a square law dependence of the concentration of excited ions on the final saturated loss. We also demonstrate self-similarity of loss evolution when experimental curves are simply normalized to fitting parameters. This evidence of self-similarity also supports the possibility of introducing a preliminary figure of merit for Yb-doped fiber. This will allow the impact of photodarkening on laser/amplifier devices to be evaluate
Photodarkening measurements in Yb-doped silica fibers in correlation with cooperative luminescence
No full text
