Light sources and detectors for near-infrared analyzers

1 Light sources and detectors for near-infrared analyzers 

The tungsten-halogen lamp operates in a very specific mode, dependent on the detailed chemistry of the atmosphere within the lamp enclosure. The lamp envelope is normally a thin quartz bulb, filled with an inert 

The pyroelectric DTGS detector is a very useful low-cost, general purpose, wideband NIR detector well suited for use in FT-based analyzers. It is not normally used in scanning monochromators where higher sensitivity detectors are needed to match the lower optical throughput and discrete wavelength scanning requirements. 

We now turn to photoconductive and photodiode detectors, both of which are semiconductor devices. The difference is that in the photoconductive detector there is simply a slab of semiconductor material, normally intrinsic to minimize the detector dark current, though impurity doped materials (such as B doped Ge) can be used for special applications, whereas by contrast, the photodiode detector uses a doped semiconductor fabricated into a p-n junction. 

Since photon energies decrease with increasing wavelength, there will be a maximnm wavelength beyond which the photons lack sufficient energy to canse electron transitions into the condnction band, known as the cut-off wavelength, Ag 

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