Quantum cascade laser-based in situ measurement of atmospheric CO and CO2 in Gandhinagar using 1f and 2f wavelength modulation spectroscopy

We report the design, development and field deployment of a quantum cascade laser-based tunable diode laser spectroscopy (TDLS) system for high-sensitivity measurement of atmospheric CO and CO₂. Two distributed-feedback quantum cascade lasers are used to interrogate the rotational-vibrational transitions of CO at 4594.99 nm and CO₂ at 4319.30 nm. The mean mole fraction values for CO and CO₂ for the measurements made at Gandhinagar from 19-25 July 2019 are 477 ppb and 486 ppm respectively. The detection limit of the system is 3 ppb CO and 45 ppb CO₂ for integration time of 17 s and 69 s respectively.