Formaldehyde sensor using interband cascade laser based quartz-enhanced photoacoustic spectroscopy

A novel continuous-wave mid-infrared distributed feedback interband cascade laser was utilized to detect and quantify formaldehyde (H2CO) using quartz-enhanced photoacoustic spectroscopy. The laser was operated at liquid-nitrogen temperatures and provided single-mode output powers of up to 12 mW at 3.53 μm (2832.5 cm-1). The noise equivalent (1σ) detection sensitivity of the sensor was measured to be 2.2×10-8 cm-1 W (Hz)-1/2 for H2CO in ambient air, which corresponds to a detection limit of 0.6 parts in 106 by volume (ppmv) for a 10 s sensor time constant and 3.4 mW laser power delivered to the sensor module.