Measurements of line strengths for NO2 near 6.2 μm using a quantum cascade laser spectrometer

Development of a compact 406 nm diode laser-based cavity-enhanced spectrometer for high-sensitive detection of NO2 levels in exhaust gas

“…Optical spectroscopic methods are believed to be more accurate over the others. Since, NO 2 remains in the atmosphere in the order of few tens of ppb levels, the highly-sensitive methods like cavity ring-down spectroscopy (CRDS) [21,23,24], differential optical absorption spectroscopy (DOAS) [25,26] and newly-developed incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) [27,28] are usually used for the measurement of NO 2 . All the methods have their own advantages and disadvantages, and the methods are usually chosen as per need to the measurements as sensitivity, portability, robustness, cost of the instrument etc.…”

“…Although it can accurately detect trace quantities at ppb to ppt levels with high accuracy, but its data acquisition and optical alignment are critical. Moreover, some measurements use mid infrared (mid-IR) quantum cascade lasers as a light source which has narrow band-width, but at the same time, these lasers are expensive, the optical alignment in the mid-IR region is difficult and requires several high-cost optical components to develop the optical set-up [23,24].…”