Analysis of a technique to determine absolute values of the stimulated emission cross section in erbium-doped silica fibres from gain measurements
ABSTRACT A method to measure absolute values of the stimulated emission cross section in erbium-doped silica fibres is analysed in this paper. Two models are studied by computer simulations made within the framework of the European project COST 241. Small errors are involved in the measurement, 31 wavelengths near 1530 nm, with moderate values of the pump power and fibre length.
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ABSTRACT: Applications, and is made available as an electronic reprint with permission of SPIE. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. ABSTRACT Photodarkening is a detrimental phenomenon known to affect ytterbium doped fibers. Methods to study the spectral and temporal properties of the photodarkening induced loss were developed. The spectral shape of the photodarkening loss measured from multiple aluminosilicate samples indicate that visible wavelength(s) could be used in benchmarking fibers for their PD induced loss. Two principal methods, core and cladding pumping, were introduced to induce a known and repeatable inversion to fiber samples. The photodarkening rate could be parameterized using a single variable, inversion. More generally, the photodarkening rate was found to follow a simple power law and to be proportional to [Yb*] 7±1 (the excited state Yb ion density). Two methods, stretched exponential and bi-exponential, were used to fit the rate measurements. Both fitting methods were found suitable, with the bi-exponential method having more potential in increasing the understanding of the mechanism(s) behind photodarkening. Coiling induced spatial changes in the inversion and subsequent photodarkening performance were demonstrated for a large-mode-area fiber laser.Proc SPIE 01/2009;
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ABSTRACT: Yb-doped fibers are widely used in applications requiring high average output powers and high power pulse amplification. Photodarkening of the Yb-doped silicate glass core potentially limits the lifetime or efficiency of such fiber devices. In many studies of photodarkening, two principal methods of controllably inducing an inversion are used, namely, cladding pumping and core pumping of the sample. We present simulation results describing the key differences in the inversion profiles of samples of different physical parameters in these two cases, and we discuss the problems and possibilities that arise in benchmarking fibers of various physical parameters. Based on the simulation and experimental work, we propose guidelines for photodarkening benchmarking measurements and show examples of measurements made within and outside of the guidelines.Applied Optics 10/2008; 47(25):4522-8. · 1.69 Impact Factor