Bandpass filters are usually used in gas detection. They transmit only a specific band wavelength (i.e. where the gas molecules vibrate) and block the rest.
The FWHM (Full Width Half Maximum) of the filter specifies the width of the filter.
The less FWHM the more restrictive it is and, therefore, it is more specific to the target gas, placed at a central wavelength (CWL).
The peak transmission (T) is also an important parameter.
The highest it is, the more energy is available from the input source.
Narrow bandpass filters are optical components that select a narrow wavelength range of a much broader light spectrum. In mid-infrared region they are used in gas sensors, spectrometers or thermal cameras to detect gases.
Typical applications are gas leak detection and hazardous gas monitoring in industry, environmental monitoring, gas identification in aerospace or in medical applications, among others.
Mapsi Photonics manufactures all-silicon filters which, in addition to being suitable for conventional applications, are particularly interesting in harsh environments, such as those involving high temperatures and/or high pressures. For instance, measuring gases in industrial chimneys.