Spectroscopy system based on a single quantum cascade laser for simultaneous detection of CO and CO₂

A quantum cascade laser (QCL) based system for simultaneous detection of CO and CO₂ is developed. The QCL can scan over two neighboring CO (2055.40 cm^-1) and CO₂ (2055.16 cm^-1) lines with a single current scan. The wavelength modulation spectroscopy (f = 20 kHz) is utilized to enhance the signal-to-noise ratio. A white cell with an effective optical path length of 74 m is used. The calibration of the sensor is performed and minimum detection limits of 1.3 ppb (1×10^-9) for CO and 0.44 ppm (1×10^-6) for CO₂ are achieved.