An infrared detector is a photodetector that reacts to infrared (IR) radiation. Photosensors or photodetectors are Sensors of Light or other Electromagnetic energy Infrared ( IR) radiation is Electromagnetic radiation whose Wavelength is longer than that of Visible light, but shorter than that of Radiation, as in Physics, is Energy in the form of waves or moving Subatomic particles emitted by an atom or other body as it changes from a higher energy 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. A bolometer is a device for measuring the energy of incident Electromagnetic radiation. A microbolometer is a specific type of Bolometer used as a detector in a Thermal camera. Thermocouples and thermopiles use the thermoelectric effect. In Electrical engineering and industry thermocouples are a widely used type of temperature sensor and can also be used as a means to convert thermal Potential A thermopile is an electronic device that converts Thermal energy into Electrical energy. The thermoelectric effect is the direct conversion of temperature differences to electric Voltage and vice versa Golay cells follow thermal expansion. In IR spectrometers the pyroelectric detectors are the most widespread. A spectrometer is an Optical instrument used to measure properties of Light over a specific portion of the Electromagnetic spectrum, typically used
The response time and sensitivity of photonic detectors can be much higher, but usually these have to be cooled to cut thermal noise. Johnson–Nyquist noise ( thermal noise, Johnson noise, or Nyquist noise) is the electronic noise generated by the thermal agitation The materials in these are semiconductors with narrow band gaps. A semiconductor' is a Solid material that has Electrical conductivity in between a conductor and an insulator; it can vary over that Incident IR photons can cause electronic excitations. In photoconductive detectors, the resistivity of the detector element is monitored. Photoconductivity is an optical and electrical phenomenon in which a material becomes more conductive due to the absorption of electro-magnetic radiation Electrical resistivity (also known as specific electrical resistance) is a measure of how strongly a material opposes the flow of Electric current. Photovoltaic detectors contain a p-n junction on which photoelectric current appears upon illumination. Photovoltaics ( PV) is the field of technology and research related to the application of Solar cells for Energy by converting Sunlight directly A p-n junction is a junction formed by combining P-type and N-type Semiconductors together in very close contact A few detector materials:
|Type||Spectral range (μm)|
|Indium gallium arsenide (InGaAs) photodiodes||0. Indium gallium arsenide ( InGaAs) is a Semiconductor composed of Indium, Gallium and Arsenic. 7-2. 6|
|Germanium photodiodes||0. Germanium (dʒɚˈmeɪniəm is a Chemical element with the symbol Ge and Atomic number 32 8-1. 7|
|Lead sulfide (PbS) photoconductive detectors||1-3. 2|
|Lead selenide (PbSe) photoconductive detectors||1. Lead selenide () or lead(II selenide, a Selenide of Lead, is a Semiconductor material. 5-5. 2|
|Indium arsenide (InAs) photovoltaic detectors||1-3. Indium arsenide, InAs, or indium monoarsenide, is a Semiconductor material, a Semiconductor composed of Indium and Arsenic 8|
|Platinum silicide (PtSi) photovoltaic detectors||1-5|
|Indium antimonide (InSb) photoconductive detectors||1-6. Platinum silicide () is a Semiconductor material used in Infrared detectors It is used in detectors for Infrared astronomy. Indium antimonide ( is a Narrow gap Semiconductor material from the III - V group used in Infrared detectors including Thermal 7|
|Indium antimonide (InSb) photodiode detectors||1-5. Indium antimonide ( is a Narrow gap Semiconductor material from the III - V group used in Infrared detectors including Thermal 5|
|Mercury cadmium telluride (MCT, HgCdTe) photoconductive detectors||0. HgCdTe or mercury Cadmium Telluride (also cadmium mercury telluride, MCT or CMT) is an Alloy of 8-25|
|Mercury zinc telluride (MZT, HgZnTe) photoconductive detectors||?|
Vanadium pentoxide is frequently used as a detector material in uncooled microbolometer arrays. Mercury zinc telluride ( HgZnTe, MZT) is a telluride of mercury and Zinc, an alloy of Mercury telluride and Zinc telluride Vanadium(V oxide ( vanadia) is the Chemical compound with the formula V2O5 A microbolometer is a specific type of Bolometer used as a detector in a Thermal camera.
conclusion THERMOCOUPLE-Di similar stripes of metals, BOLOMETER- Metal or semiconductor, THERMISTOR-Metallic oxide(not used in open environment), GOLAY CELL - Black metal plates (commercially used)