Models for the sensitization of thermoluminescence in silica fibres

Several models have been suggested for the sensitization effect, which is the enhancement of the TL sensitivity following irradiation and thermal annealing. The main models are reviewed here, as well as methods by which the appropriate model for the case under study may be established. Some of these methods are demonstrated in relation with a sensitization effect which was recently found in Ge-SiO₂:Nd optical fibres. Initially the TL emission spectrum consisted of a major blue band and a weaker green band. The sensitization effect was much stronger for the green band, and for high doses it exceeded the blue one. It is argued that the sensitization is compatible with the Zimmerman-Chen model which is based on the transfer of electronic charge carriers and a 'competition during heating'.