Tellurite And Fluorotellurite Glasses For Active And Passive

6. Optical properties; MDO 166
75-52-12VDC FT-IR Purge Gas Generator. Due to the sensitivity of the FTIR, a small
amount of moisture was still present after this drying and an absorption band was
observed in some of the spectra at around 3600 cm -1 (2.78 µm) due to atmospheric water
[1]. Later in the work more careful purging was carried out on the sample chamber and
the atmospheric water could be removed. A band observed around 2800 cm -1 (3.57 µm)
was attributed to CH, CH2 or CH3 also [1] which is an artefact from the polishing process
due to mounting wax and / or polishing oil, because this band was not present in the fibre
loss spectra (see chapter 8). To prepare bulk glass samples, opposite sides were ground
flat and parallel using SiC powder in an oil suspension. The samples were then polished
using diamond paste to a 1 µm finish, resulting in a sample of around 3 mm thickness,
washing in between stages with acetone (Fisher). The raw absorption data from the
spectrometer was divided by sample thickness (in cm) to give the absorption coefficient
in cm -1 . Background loss was therefore not meaningful. Absorption bands, which were
believed to be made up of a number of overlapping bands, were Gaussian deconvoluted
using the method described in section 4.1.1.3 in Microcal Origin software.
6.1.1.2. Theory of operation
Spectroscopy is a group of techniques which measure the interaction of electromagnetic
radiation with matter. The infrared (IR) region of the electromagnetic spectrum (100-
5000 cm -1 ) has sufficient energy to excite molecular vibrations or phonons [2].
Absorption bands in infrared spectra can therefore be used to identify structural units and
organic groups in a material. Absorption spectroscopy measures the total absorption of a