Sensitivity improvement of midinfrared gas sensing system using single-wavelength quantum cascade laser and hollow-waveguide gas cell

The configuration of a gas analysis system using the combination of a single-wavelength quantum cascade laser and a hollow-optical-fiber gas cell was optimized to improve measurement sensitivity. On the basis of theoretical calculation, a 6-m looped fiber gas cell was introduced into the system to more sensitively measure the concentration of nitric monoxide (NO) gas. High-precision measurement is achieved by precisely scanning the wavelength of the laser around the sharp absorption peak of NO gas. Concentrations of NO gas as low as 100 ppb were successfully measured.