Tellurite And Fluorotellurite Glasses For Active And Passive

6. Optical properties; MDO 236
addition of PbO or GeO2, without significantly affecting the multiphonon edge, although
OH bands were more intense.
6.3.1.2. Infrared spectroscopy of fluorotellurite glasses
Infrared spectroscopy of series (90-x)TeO2-10Na2O-xZnF2 mol. %, for 5 ≤ x ≤ 30 mol. %
Fig. (6.26) shows the infrared spectra of glasses of the series (90-x)TeO2-10Na2O-xZnF2,
mol. %, for 5 ≤ x ≤ 30 mol. % (glasses MOF001, 004 to 008). Glass MOD013 (80TeO2-
10Na2O-10ZnO mol. %) was also plotted for comparison. As expected the intensity of
the OH spectral absorptions decrease with increasing ZnF2 content and melting time as
the glass is dried in situ (see section 3). Fig. (6.27) illustrates this, by plotting the loss in
dB.m -1 attributed to the free-OH at 2900 cm -1 with increasing ZnF2 content, which
plateaux to a minimum loss of around 20 dB.m -1 at compositions containing more than 15
mol. % ZnF2. The drying effect was significant, as the 5 mol. % ZnF2 glass showed an
optical loss of around 120 dB.m -1 at 2900 cm -1 [5]. Fig. (6.28) shows the effect of melting
time of glass MOF001 (65TeO2.25ZnF2.10Na2O mol. %), on the loss caused by spectral
absorption of the OH band around 2900 cm -1 . After 1 hour of melting the optical loss of
the finished glass MOF001 (65TeO2-10Na2O-25ZnF2 mol. %) was relatively high
(comparable to the pure oxide glass MOD013 - 80TeO2-10Na2O-10ZnO mol. %),
however after 2 hours of melting the loss had decreased by almost two orders of
magnitude (from 705 to 10 dB.m -1 ) showing the importance of melting time for the
drying process [5].