Article

Dynamics of pump-induced refractive index changes in single-mode Yb-doped optical fibers

Faculté Polytechnique de Mons, Service d'Electromagnétisme et de Télécommunications, Mons, Belgium.
Optics Express (Impact Factor: 3.49). 09/2008; 16(17):12658-63. DOI: 10.1364/OE.16.012658
Source: PubMed

ABSTRACT

We quantify the refractive index changes (RIC) in single-mode ytterbium-doped optical fibers induced by optical pulses at 980 nm and, for the first time, report details of the effect dynamics. The RIC dynamics is shown to follow that of the population of the excited/unexcited ion states with a factor proportional to their polarizability difference (PD). The absolute PD value is evaluated in the spectral range of 1460-1620 nm for different fiber samples and is found to be independent on the fiber geometry and on the ion concentration. The PD dispersion profile indicates to a predominant far-resonance UV rather than near-resonant IR transitions contribution to the RIC.

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Available from: Andrei A. Fotiadi, Jun 08, 2014
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    • "For example, decaying parts of the phase traces [Fig.1 (b)] describe relaxation of the refractive index after the end of the pulse excitation. For non-irradiated fibers they are perfectly fitted by one exponential decay function with the relaxation time constant equal to the Yb-ion excited state life-time ~750 µs, the same for all fiber samples [2] [3]. However, for irradiated fibers the similar curves are observed to decay according to a triple exponential with time constants estimated to be ~750, ~500 and 40µs. "
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    • "To combine the power of all the channels in one single-mode output the fiber amplifiers must be phase-locked together. The effect of refractive index changes (RICs) induced in single mode Yb-doped optical fibers by resonance pumping (that is essentially a side effect of the population inversion) [1] offers a simple solution for all-fiber coherent combining of intense laser beams at any IR wavelength far from Yb-doped ion resonances. Here we report a coherent combining of two 500- mW EDFAs operating at 1550nm with a dynamical phase control provided either by one low-power laser diode at 980nm alone or in combination with a laser at 1060nm both stimulating electron transitions in an Yb-doped optical fiber. "
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