Analysis of temperature dependence of photodarkening in ytterbium-doped fibers

作者：Montiel i Ponsoda Joan J; Ye Changgeng; Koplow Jeffrey P; Soderlund Mikko J; Koponen Joona J; Honkanen Seppo

来源：Optical Engineering, 2011, 50(11): 111610.

DOI：10.1117/1.3640856

• fiber lasers
• rare-earth-doped materials
• ytterbium
• photodarkening
• thermal effects

We examine the temperature dependence of photodarkening in ytterbium-doped silica fibers. A sequence of consecutive photodarkening experiments are performed over the same fiber sample, which shows good repeatability with no apparent changes in the glass structure. We find that during infrared irradiation, the level of saturation of the losses can be determined by the fiber core temperature, independent of the previous state of photodarkening losses and fiber temperature, and also at low temperatures where the thermal bleaching is not activated. We observe that variations in the fiber core temperature, induced by pump absorption due to photodarkening, affect the inversion level and photodarkening processes. These effects in turn cause a discrepancy in determining the ion dependence. We highlight the importance of performing the experiments under isothermal conditions and we propose a new approach to control the fiber temperature at room temperature and at elevated temperatures. The approach is based on an isothermal Galinstan bath. The appropriateness of this method is shown by comparing it to different cooling methods, and the results are supported by simulations.

• 出版日期2011-11