Which IR detector is the best?


Unfortunately, there is not a perfect detector for the entire infrared region. As a consequence, there are a number of factors to consider when choosing an infrared detector for your measurement, including

  • Spectral range
  • Sensitivity
  • Cooling method
  • Response speed

It is often not possible to optimize all the desired factors in a single detector; some compromises will be needed. For a detailed description of these factors, please refer to "Characteristics and use of infrared detectors." Some of the more commonly used detectors at our beamline are listed below. For a complete listing of the available infrared detectors, please see our detector list.


Spectral Range / cm-1
Sensitivity (D*) / cm•Hz1/2•W-1
Speed (Time constant) / s
DTGS 10-11,000 (depends on window material)
~2 x 108
Room Temp
650-11,000 ~2 x 1010
Liquid N2 ~10-6
400-11,000 ~4 x 109
Liquid N2 ~10-6
Si Bolometer
3-5000 ~5 x 109
Liquid He ~10-3


Our infrared microscopes (Beamlines 1.4.3 and 1.4.4) are equipped with an MCT A detector because this detector provides the best sensitivity and speed over a broad spectral range covering the entire mid-infrared and most of the near-infrared (up to ~11,000 cm-1). One downside to these detectors is that they require liquid nitrogen. The dewars, however, last > 8 hours and liquid nitrogen is readily available at the ALS. 



Upcoming Events

The Thermo Spectroscopic Solutions Workshop series is a free way to learn about FTIR, Raman and their uses. It's being held across the US and Canada this Spring, including in Fremont on April 15, 2014.

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