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

TL;DR

This paper revisits the phenomenon of photodarkening in Yb-doped fibers, proposing that trace Tm impurities significantly influence defect formation, which may explain conflicting observations in previous studies.

Contribution

It introduces the hypothesis that Tm impurities affect photodarkening in Yb fibers and reconciles previous literature discrepancies based on spectroscopic evidence.

Findings

Tm traces impact defect creation in Yb fibers

Literature results are consistent with the Tm hypothesis

Proposes Tm as a key factor in photodarkening variability

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.