Revisiting literature observations on photodarkening in Yb3+doped fiber considering the possible presence of Tm impurities

Abstract

Ytterbium (Yb) doped fiber lasers are known to be affected by the creation of color centers during lasing (socalled photodarkening (PD)). In a previous work, this defect creation was investigated from a spectroscopic point of view, showing the presence of traces (ppb) of thulium (Tm) in the Yb doped fiber. It was shown that Tm has a strong impact on the defect creation process involved in PD. In this paper, we compare the results from the literature with our Tm hypothesis, without finding any contradiction. Moreover, this hypothesis can be an explanation for the discrepancies in the literature.

Deep UV-induced near-infrared photodarkening of Er/Yb-doped and undoped phosphate fibers

“…In addition to PD induced by pump light at 980 nm, PD was also observed to occur under irradiation at 193 and 488 nm [10,11]. Although the exact mechanism of the PD in Yb-doped silica fiber is still under debate, light-induced loss is commonly attributed to the formation of color centers by photoionization via either single-or multi-photon absorption processes, depending on the irradiation wavelength [6,[11][12][13][14]. The peak absorption wavelength observed in different glasses depends on the species of color centers generated and ranges from the visible (VIS) to the UV.…”

Contribution of different factors in heat production in Yb3+-doped fiber laser: a review

“…This could be due to charge transfer, nonbridging oxygen holes, oxygen deficiency centers, Yb 2þ ions, or even Yb 2þ − Yb 3þ pairs. 41 Some dopants, such as aluminum with high concentration or aluminum-phosphor, can suppress the PD effect. 18,39,42 Optimizing the doping composition by codoping with cerium (Ce), P, Al, and Na ions into the fiber could inhibit PD to a certain extent.…”

Progress and Summary of Photodarkening in Rare Earth Doped Fiber

“…When 488 nm light was used to irradiate, the absorption peak of ODCs was 220 nm, which can produce two-photon absorption, then release free electrons, and be absorbed by Yb and Al, forming the color center, leading to the phenomenon of PD. In 2012, Peretti et al [62] showed that trace thulium existed in YDF. They thought that the reason for PD was that thulium ion produced ESA at 488 nm and produced ultraviolet light, reaching the charge-transfer absorption band at 230 nm.…”