Infrared detector

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An infrared detector is a photodetector that reacts to infrared (IR) radiation. The two main types of detectors are thermal and photonic.

The thermal effects of the incident IR radiation can be followed through many temperature dependent phenomena. Bolometers and microbolometers are based on changes in resistance. Thermocouples and thermopiles use the thermoelectric effect. Golay cells follow thermal expansion. In IR spectrometers the pyroelectric detectors are the most widespread.

The response time and sensitivity of photonic detectors can be much higher, but usually these have to be cooled to cut thermal noise. The materials in these are semiconductors with narrow band gaps. Incident IR photons can cause electronic excitations. In photoconductive detectors, the resistivity of the detector element is monitored. Photovoltaic detectors contain a p-n junction on which photoelectric current appears upon illumination. A few detector materials:

[edit] Types

Type	Spectral range (μm)
Indium gallium arsenide (InGaAs) photodiodes	0.7-2.6
Germanium photodiodes	0.8-1.7
Lead sulfide (PbS) photoconductive detectors	1-3.2
Lead selenide (PbSe) photoconductive detectors	1.5-5.2
Indium arsenide (InAs) photovoltaic detectors	1-3.8
Platinum silicide (PtSi) photovoltaic detectors	1-5
Indium antimonide (InSb) photoconductive detectors	1-6.7
Indium antimonide (InSb) photodiode detectors	1-5.5
Mercury cadmium telluride (MCT, HgCdTe) photoconductive detectors	2-25
Mercury zinc telluride (MZT, HgZnTe) photoconductive detectors	?