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IEEE Journal of Lightwave Technology
Volume 18 Number 2, February 2000

Measurements of Thermal Effects in Fibers Doped with Cobalt and Vanadium

Page 161.

Abstract:

Thermal index changes due to nonradiative relaxation in optically pumped Co²⁺-doped and Vⁿ⁺ -doped fibers are studied experimentally by an interferometric method. In both dopants these effects are shown to be very strong and to mask any residual resonantly enhanced nonlinearity. The measured magnitude and time constants of thermal effects are well explained by a new theoretical model, which confirms its validity and usefulness. These measurements also demonstrate a new and simple method to differentiate between nonlinear and thermal phase shifts in doped fibers based on the dependence of the phase change on the pump pulsewidth. This study provides new information on the spectroscopy of these two dopants, including the percentage of absorbed power they transform into heat (38% for Co²⁺ and 56% for Vⁿ⁺), and the likely presence of clusters in Co²⁺-doped silica even at very low concentrations (8 wt ppm CoO).

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