An infrared detector is a detector that reacts to

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from aroun ...

(IR)

radiation In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes: * ''electromagnetic radiation'', such as radio waves, microwaves, infrared, vi ...

. The two main types of detectors are thermal and photonic (

photodetector Photodetectors, also called photosensors, are sensors of light or other electromagnetic radiation. There is a wide variety of photodetectors which may be classified by mechanism of detection, such as photoelectric or photochemical effects, or by ...

s). The thermal effects of the incident IR radiation can be followed through many temperature dependent phenomena.

Bolometer A bolometer is a device for measuring radiant heat by means of a material having a temperature-dependent electrical resistance. It was invented in 1878 by the American astronomer Samuel Pierpont Langley. Principle of operation A bolometer ...

s and microbolometers are based on changes in resistance.

Thermocouple A thermocouple, also known as a "thermoelectrical thermometer", is an electrical device consisting of two dissimilar electrical conductors forming an electrical junction. A thermocouple produces a temperature-dependent voltage as a result of th ...

s and thermopiles use the thermoelectric effect. Golay cells follow thermal expansion. In IR

spectrometer A spectrometer () is a scientific instrument used to separate and measure spectral components of a physical phenomenon. Spectrometer is a broad term often used to describe instruments that measure a continuous variable of a phenomenon where th ...

s 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 A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. ...

with narrow band gaps. Incident IR photons can cause electronic excitations. In photoconductive detectors, the

resistivity Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current. A low resistivity indicates a material that readily allows ...

of the detector element is monitored.

Photovoltaic Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commercially ...

detectors contain a p-n junction on which photoelectric current appears upon illumination. An infrared detector is hybridized by connecting it to a

readout integrated circuit A Readout integrated circuit (ROIC) is an integrated circuit (IC) specifically used for reading detectors of a particular type. They are compatible with different types of detectors such as infrared and ultraviolet. The primary purpose for ROICs is ...

with indium bumps. This hybrid is known as a focal plane array.

Detector materials

* Lead(II) sulfide (PbS) * Mercury cadmium telluride (Known as MCT, HgCdTe) * Indium antimonide (InSb) * Indium arsenide *

Indium gallium arsenide Indium gallium arsenide (InGaAs) (alternatively gallium indium arsenide, GaInAs) is a ternary alloy (chemical compound) of indium arsenide (InAs) and gallium arsenide (GaAs). Indium and gallium are ( group III) elements of the periodic table wh ...

* Lead selenide * QWIP * Lithium tantalate (LiTaO3) * Triglycine sulfate (TGS) * Platinum silicide (PtSi)

References

{{reflist Detectors Image sensors Infrared imaging

Detector materials

See also

References