Bandpass Filters Outfit Pyroelectric Detectors

March 29, 2017

LASER COMPONENTS introduces five bandpass filters for pyroelectric detectors that include reference filters (B) and filters for the detection of CO2 (A), water vapor (M), methane (S), and alcohol (O), and are either mounted directly inside the fixed cap of the detector or available as a separate cap, which is then mounted to an existing pyroelectric detector. A reference filter should not have any gas absorption. Filter B can be used when SO2 is part of the gas mixture (peak wavelength = 3.86 µm, Full Width-Half Max (FWHM) = 90 nm). The CO2 filter A with a peak wavelength of 4.265 µm is the filter with the best possible signal and simple linearization (FWHM = 110 nm). Water vapor is in almost every gas mixture, which often leads to a disturbing background noise. An attempt to measure this with a 2.94 µm filter, for example, leads to problems of cross-sensitivity with CO2. The M filter has proven more reliable in such practical applications: peak wavelength = 5.78 µm, FWHM = 180 nm. Methane is primarily measured at 3.33 µm; however, this is not particularly specific. An excellent alternative is the S filter, which operates at a longer-wave band: peak wavelength = 7.91 µm, FWHM = 160 nm. With the increased popularity of breath alcohol measurement, the new standard filter S (peak wavelength = 9.50 µm, FWHM = 450 nm) has become beneficial. For more info, go to

Laser Components USA Inc.
Bedford, NH


Company Laser Components USA, Inc.
Country United States (USA)