Tellurite And Fluorotellurite Glasses For Active And Passive

6. Optical properties; MDO 170
In reality the signal consisted of a range of frequencies, therefore the total intensity at the
detector is given by equation (6.5) [3].
~ ~ ~
I ( δ ) = I(
f )( 1+
cos 2πfδ
) df
(6.5)
∫0 ∞
To provide a useful spectrum, the variation in intensity with wavenumber, I( f ~ ),must be
found. This was obtained by a Fourier transform integration step shown by equation (6.6)
[3].
~
1 ~
( f ) = 4 [ I(
δ ) − I(
0)]
cos( 2πfδ
) dδ
(6.6)
0 2
I ∫ ∞
This integration was performed here by the FTIR spectrometer computer, which
displayed the output, I( f ~ ) against f ~ , which formed the spectra of the sample.
The major advantage of the FTIR spectrometer is that all of the radiation detected
from the sample is continuously monitored. Therefore, the FTIR is highly sensitive and
fast compared to spectrometers where a monochromator discards most of the radiation.
The resolution, ∆ f ~ , is defined by equation (6.7) [3].
~ 1
∆f =
(6.7)
2δ
max