Gas Analysis Gas Analysis

Gas analysis using infrared (IR) detectors

Explore how Hamamatsu's latest innovative multi-stage detector design makes for a faster, more reliable, and stable gas detection in the mid-IR region. Without harmful materials, it also reduces our ecological footprint and consumption costs, without compromising on performance.

Gas analysis is used in many fields including environmental monitoring, process control, energy, and healthcare. Compared to other methods, gas analysis based on the absorption of gases at specific near- and mid-infrared wavelengths has advantages such as non-contact measurement, higher sensitivity, and long product lifetimes. Absorption-based gas analyzers require an infrared detector. We offer many choices of infrared detectors including RoHS-compliant InAsSb photovoltaic detectors.

Lineup of detection elements

Gas Analysis detector graph

Infrared (IR) detectors

Hamamatsu offers many infrared detector choices for absorption-based gas analyzers, including RoHS-compliant InAsSb photovoltaic detectors. When selecting an appropriate detector, it is important to match the gases’ absorption bands to the detector’s spectral sensitivity. Other detector characteristics to consider include:

  • Sensitivity
  • Specific detectivity (D*)
  • Noise
  • Linearity
  • Speed
  • Package
  • Cooling

There are detectors optimized for room temperature operation, but in highly analytical applications, cooling may be required. There are two methods to cool infrared detectors: 1) using a built-in thermoelectric (TE) cooler, and 2) adding liquid nitrogen. While TE-cooling is more convenient and requires less frequent replacement, liquid nitrogen’s deeper cooling gives a detector higher D* values, indicating better performance.


We offer a diverse lineup of IR detectors. Their cutoff wavelength and D* values are shown in the table below.

    D* values at peak wavelength (cm·Hz1/2/W)
Cutoff wavelength Detector Uncooled Thermoelectric cooling Liquid nitrogen cooling
14 µm Type II superlattice -- -- Up to 1.6 x 1010
11 µm InAsSb photovoltaic (RoHS compliant) Up to 1 x 109 Up to 6 x 109 --
6.7 µm InSb photoconductive -- Up to 1 x 1010 --
5.5 µm InSb photovoltaic -- -- Up to 1.6 x 1011
20 µm Thermopiles Up to 1.3 x 108 -- --
3.6 µm InAs photovoltaic Up to 4.5 x 109 Up to 3.2 x 1010 Up to 6 x 1011
2.6 µm InGaAs PIN photodiodes Up to 1 x 1012 Up to 8.5 x 1012 --


InAsSb photovoltaic detectors

Unfortunately, many detectors in the MIR space rely on hazardous materials outlined by RoHS standards. These materials are also prone to high variance at high volumes. Hamamatsu's product line is fully RoHS compliant, relying on indium arsenide antimonide (InAsSb) material. Mercury, cadmium, or lead are not used. Our InAsSb detectors’ cutoff wavelengths span from 5.3 µm up to 11 µm. Customizations for these detectors include built-in filters and window material.


With so much information in the longer wavelengths, the boundaries needed to be pushed. Hence the development of type II superlattice, a new innovation for InAsSb material. Our proprietary layering design presents new characteristics that yield high sensitivity out to 14 microns. Currently available with liquid nitrogen cooling with TEC versions under development.

InSb photoconductive detectors

Our indium antimonide (InSb) photoconductive detectors are sensitive to IR wavelengths up to 6.7 µm, and all are TE-cooled.

InSb photovoltaic detectors

Sensitive up to 5.5 µm, indium antimonide (InSb) photovoltaic detectors can be used to detect gases below the 5 µm wavelength band. All of our InSb detectors are cooled with liquid nitrogen.


Our thermopiles have a spectral range of 3-20 micron, and we also offer a two-stage thermopile with filters catered to CO2 measurements. Although they are less expensive than photovoltaic or photoconductive detectors, they have lower D* values and much slower response speed.

InAs photovoltaic detectors

Sensitive up to 3.6 µm, indium arsenide (InAs) photovoltaic detectors feature low noise, high sensitivity, high-speed response, and high reliability. They are available in uncooled, TE-cooled, or liquid-nitrogen-cooled models.

InGaAs PIN photodiodes

Indium gallium arsenide (InGaAs) PIN photodiodes are suitable for gas sensors operating in the near-infrared region. They feature high D* values, low noise, high-speed response, and high reliability.

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Type Ⅱ superlattice infrared detector

High-sensitivity and high-speed infrared detector with 14 μm cutoff wavelength.

InAsSb photovoltaic detectors deliver high sensitivity in the 5 μm, 8 μm, and 11 μm band due to our unique crystal growth technology.

Infrared product conversations part 3: IR detector deep dive

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