Analysis of temperature dependence of photodarkening in ytterbium-doped fibers

Abstract

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. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

Mathematical Model of Photodarkening in Rare-Earth-Doped Fiber

“…where N cc,max (T) is the final equilibrium state of the density of the CCs related to the core temperature [7,45]. Temperature is used to describe the degree of thermal movement of microparticles, which has an important impact on the stability of PD precursors and CCs.…”

Progress and Summary of Photodarkening in Rare Earth Doped Fiber

“…When the time went to infinity, the saturation loss was obviously depended on the fiber temperature. In 2011, Ponsoda et al [30] examined the temperature dependence of PD in Yb-doped silica fibers. A series of continuous PD experiments were carried out on the same fiber samples.…”

“…Therefore, it is possible to repeat the experiment without replacing the optical fiber sample. This device is most commonly used in PD experiment [14,22,25,28,30,33,37,73]. It cannot only measure the characteristic wavelength absorption, but also can be used in absorption spectrum measurement and refractive index measurement.…”