Analytical Infrared (IR) Analytical Infrared (IR)

Infrared (IR) spectroscopy

Infrared (IR) spectroscopy is an umbrella term for spectroscopic techniques that involve probing of matter with infrared radiation. Typically, the aim of this investigation is the identification of a specific compound and its concentration. In the simplest absorption IR spectroscopy, a broadband IR source illuminates a sample. A molecule absorbs radiation of specific wavelengths depending on the allowed transitions between its quantum mechanical vibrational and rotational states. The configuration of states is unique to a molecule. The spectrum of the transmitted light contains absorption features whose distribution and intensity depend on the chemical composition of the sample. A typical setup for dispersive absorption IR spectroscopy consists, apart from mirrors and lenses, of an IR source, reflection or transmission grating, and image sensor. The technique can be used to analyze solid, liquid, and gaseous samples. Gas emission monitoring and quality control for the presence of impurities are two application examples of IR absorption spectroscopy.


Hamamatsu is a leading manufacturer of essential components for IR spectroscopy. These include InGaAs image sensors covering the 0.9-2.55 μm range and single-element detectors (photovoltaic, photoconductive, and pyroelectric types) covering the wavelength range from visible up to ~20 μm. Hamamatsu also manufactures complete compact spectrometers and FTIR engines with a Michelson-Morley interferometer, an InGaAs PIN photodiode, and a calibration laser inside.

Fourier-transform infrared (FTIR) spectroscopy instruments

Fourier-transform infrared (FTIR) spectroscopy is a popular alternative to the dispersive technique described above. Here, the incident radiation from a broadband IR source, after passing through the sample, is directed to the Michelson-Morley interferometer, and then to a single-element IR detector. The detector produces an interferogram: light level measured by the detector as a function of the mirror position in the interferometer. Applying fast Fourier transform to the interferogram produces the spectrum of the sample and the source. Subtracting the spectrum of the source yields the spectrum of the sample. Compared to dispersive techniques, FTIR offers three advantages that improve signal-to-noise ratio: multiplexing, higher throughput, and higher wavelength accuracy. FTIR can be employed – as an alternative – in all applications where a dispersive technique is used. Because FTIR offers a higher sensitivity and a shorter data acquisition time, additional applications become feasible, for example, hyperimaging, studies of proteins in biological samples, or in-situ 13C/12C ratio analysis in water carbonates.


FTIR remains an extremely popular technique for analytical chemistry. Hamamatsu's infrared detectors have the wide coverage, sensitivity, and price point necessary to give instruments a competitive edge.


Learn more on FTIR

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 is proud to showcase a fully RoHS-compliant product line relying on indium arsenide antimonide (InAsSb) material. No mercury, cadmium, or lead are used.


InAsSb detectors are RoHS compliant, unlike mercury cadmium telluride (MCT) detectors. They also have highly stable characteristics and minimal variations from one detector to another. The cutoff wavelength of our InAsSb detectors ranges from 3 µm up to 14 µm.


When selecting an InAsSb detector, consider these characteristics:

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


Customizations include:

  • Built-in filter
  • Window material

Quantum cascade lasers (QCLs)

QCLs have an extremely narrow emission band in the mid-infrared region, making them suitable for high-accuracy measurements. When selecting QCLs, consider these characteristics:

  • Peak emission
  • Tuning
  • Output power
  • Operating temperature
  • Operating current
  • Package (TO can/HHL/butterfly)


We offer continuous wave (CW HHL package) and pulsed QCLs with emission wavelengths within the 4 – 10 µm band. They feature high output, high-speed response, and high reliability.


Customizations include:

  • Wavelength range or peak emission
  • Output power
  • Operating temperature and current
  • Additional cooling stages

Recommended products

FTIR engine

FTIR engine with a Michelson optical interferometer and control circuit are built into a palm-sized enclosure.

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.

Quantum cascade lasers are semiconductor lasers that offer peak emission in the mid-IR range (4 μm to 10 μm). They have gained considerable attention as a new light source for mid-IR applications such as molecular gas analysis used in environmental measurement.

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