Influence of temperature on the post-irradiation temporal loss evolution in Yb-doped aluminosilicate fibers, photodarkened by 488 nm CW irradiation

Photodarkening (PD) in optical fibers is a serious concern for the development and maintenance of the reliable operation of high-power ytterbium fiber lasers (YDFL), over a long period of time. Formation of colour centres in the silica glass host is often believed to be the reason behind PD [1]. Yb-doped aluminosilicate fiber suffers PD as a permanent excess optical loss (unless optically or thermally photo-bleached) having a low-energy absorption tail extending into the 0.9-1.0 mum absorption band and 1.1 mum emission band of YDFLs [2,3]. Our previous studies emphasised on oxygen deficient centres (ODC) as a precursor of PD in Yb-doped aluminosilicate fiber [4] under a 488 nm CW pump and also revealed the post-irradiation temporal evolution of the induced loss [5]. To the best of our knowledge, our present report is the first of its kind to show the temperature dependance of the post-irradiation induced excess loss in VIS-NIR in Yb-doped aluminosilicate fiber, even after stopping the 488 nm CW pump.