Tellurite And Fluorotellurite Glasses For Active And Passive

6. Optical properties; MDO 171
where δmax = maximum pathlength difference of the inferometer. Therefore, a resolution
of 0.2 cm -1 , gives δmax = 2.5 cm.
Detectors
The detector in a spectrometer converts the incident radiation received from the sample
into an electronic signal to be processed. Much like the source, the detector type depends
on the region of the electromagnetic spectrum being investigated. However,
semiconductor detectors are commonly used in the ultraviolet (UV), visible and IR. One
popular type of semiconductor detector is known as a charge coupled device (CCD) [3].
In higher frequency regions, such as the visible and UV, a photomultiplier is alternatively
used. This photomultiplier works by releasing an electron from a photosensitive screen
each time it is struck by an incident photon. This electron is accelerated by a current,
striking further screens creating a cascade effect, resulting in an amplified signal.
Although semiconductor devices are becoming more frequently used, thermocouple
detectors are sometimes used for the IR [3].
Intensities of absorption bands and the Beer-Lambert law
An empirical equation, known as the Beer-Lambert law, can be used to calculate the
intensity of absorption, I, with sample thickness, l. This is shown by equation (6.8) [3].
log
I
I
0
= −ε[
J ] l
(6.8)