Understanding Infrared Detectors

Our infrared photodetectors convert light into electricity. We supply so-called quantum (or photonic) type detectors which generate an electrical charge through the absorption of a photon. Quantum detectors exhibit very fast response times and higher sensitivities but suffer with a responsivity that varies with wavelength and other than near infrared devices, generally need to be cooled to improve signal-to-noise levels. Gallium Arsenide (InGaAs) or Germanium (Ge) detectors are generally used at room temperature in the near infrared (wavelengths between 800 to 2200nm). Mercury Cadmium Telluride (MCT) or Indium Antimonide (InSb) detectors work in the mid infrared (wavelengths between 1 to 25 microns). These detectors are cooled to improve signal to noise. Pro-Lite also supplies laser power meters based upon thermal detectors - click here for details.

Near Infrared: InGaAs & Germanium

Indium Gallium Arsenide (InGaAs) detectors are semiconductor photodiodes that produce an electrical charge as a result of the photovoltaic effect. InGaAs diodes work in the near infrared, from 800-1700nm approximately. Special, extended wavelength InGaAs detectors provide for measurements out to 2200nm and beyond. 

Germanium (Ge) detectors are similar to InGaAs but have a slightly reduced sensitivity. Ge detectors do however offer significant economies when large detector areas are required and they also provide improved linearity at high levels of irradiance.

Available options include large area InGaAs detectors, two-colour Si/Ge, custom packages and windows, extended range InGaAs, avalanche Ge photodiodes, as well as high speed InGaAs.

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Mid Infrared: MCT & InSb

Quantum detectors based upon Mercury Cadmium Telluride (MCT, photoconductive) and Indium Antimonide (InSb, photovoltaic) are used in the mid infrared band, between 1 to 5.5 and 1 to 25 microns respectively. 

We supply a variety of standard and custom HgCdTe and InSb detectors, including quadrants and multi-element arrays from 2 to 128 pixels. These detectors must be operated below room temperature; cooling can be made cryogenically (liquid nitrogen in a dewar), using a thermoelectric (multi-stage TE, or Peltier) cooler, or using a Stirling-cycle engine. 

Matched preamplifiers are available for each detector type. 

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