Augmented sensitivity of an IR-absorption gas sensor employing a metal hole array

We demonstrate the use of plasmonic extraordinary transmission at IR wavelengths for surface-enhanced infrared absorption (SEIRA) spectroscopy in gas sensing. Gas detection was performed through non-dispersive infrared (NDIR) absorption. The sensitivity of SF6 gas detection is increased around ∼27 times with metal hole array (MHA) microstructures placed on the gas cell mirrors, as compared with non-structured mirrors; an absorption change of 2% per 100 ppm was obtained on a standard commercial pyroelectric detector. Down-sizing of IR-sensors to a sub-1 mm gas cell width, delivering ∼ 40 nM (or 1 ppm) of SF6 sensitivity, can be foreseen with a simple source-detector setup.