Gamma-radiation-induced photodarkening in ytterbium-doped silica glasses

Experimental evidence for the formation of divalent ytterbium in the photodarkening process of Yb-doped fiber lasers

“…A possible interpretation of the previous reported observations is that excitation to the first (lowest in energy) CT-state result in a temporal (non-stable) Yb 2+ ion and a localized hole (h temp ) on a nearby oxygen ligand whereas excitation to the second (higher in energy) CT sub-band corresponds to the formation of a permanent (stable) Yb 2+ ion and a bound hole (h bound ). The nature of the bound hole is most likely an Al-OHCs situated in the vicinity of the Yb ion, which has previously been identified by Arai et al [8] in photodarkened preform and fiber samples by performing Electron Spin Resonance (ESR) measurements. Now, for a permanent Al-OHC to form in the PD process a charge compensating (electron related) trap also need to form.…”

“…The presented results show a strong support for the model that the valence stability of the Yb ion play a key role for the PD kinetics in Yb-doped fiber lasers. Furthermore, the Yb 2+ ions can act as electron traps, which can charge compensate the Al-OHCs that has earlier been identified to be responsible for the induced absorption bands in the visible-and NIR range [8].…”

“…The first model implies that the valence instability of the Yb-ion is the origin of PD where a valence state change is believed to occur through a charge transfer (CT) process [6,7]. This will result in pair generation of divalent Yb ions together with bound hole centers, which most likely can be assigned to aluminum oxygen hole centers (Al-OHCs) [8]. The second model is related to intrinsic defects such as Oxygen Deficiency Centers (ODCs), which are believed to form during the silica preform and fiber fabrication.…”

Effect of Li2O substitution on structures and properties of Nd3+‐doped Al(PO3)3‐Li2O glasses

“…As previously reported, X-ray absorption fine structure (XAFS) indicates that oxygen atoms fully occupy the first coordination shell of Yb 3+ ions in Yb 3+ /Al 3+ co-doped silica glass. 37 The absence of oxygen signals in APLx glasses is due to their extremely low natural abundance (∼0.038%). 38 All spectra in Figure 9 were obtained under the same testing conditions, thus the relative intensity of all signals could be compared.…”

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“…Данный эффект обусловлен наведением дефектов в сетке стекла, имеющих широкую полосу поглощения с максимумом в видимой области спектра [12-13]. Природа дефектов связана с образованием кислородо-дырочных центров как результата фотоиндуцированного возбуждения состояния переноса заряда ионов Yb 3+ [14][15][16][17] [18]. Однако как введение оксида фосфора, так и совместное введение оксида алюминия с оксидом церия приводит к увеличению показателя преломления сердцевины относительно уровня кварцевого стекла и, следовательно, ограничивает максимальный диаметр сердцевины одномодового световода.…”