Tellurite And Fluorotellurite Glasses For Active And Passive

2. Literature review; MDO 59
The glasses exhibited two absorption bands attributed to ‘water’, with maxima around 3.2
and 3.5 µm. Both bands are broad and overlap, but are of low intensity, and are
practically non-existent in the glass with 51.81 mol. % ZnF2, due to chemical reactions
which take place during melting as shown by equation (2.16) to (2.18).
Nazabal et al. [30] showed a decrease in OH bands with increasing ZnF2 content in the
glass as shown by fig. (2.15).
Fig. (2.15): Infrared spectra of TeO2-ZnO-ZnF2 glasses [30].
It can be seen the OH bands were reduced by self-drying during melting as described by
equations (2.16) to (2.18). Erbium (III) bands at around 1.55 µm in these glasses were
shown to slightly broaden, and 4 I11/2 and 4 I13/2 lifetimes significantly increase (from 0.4 to
2.2 ms and 3 to 7 ms respectively, for 0 to 35 mol. % ZnF2) with fluorine content. This
was though to be due to a combination of a change in ion-host field strengths, and
reduction in OH content with fluorine addition [31].