Simultaneous detection of CO and CO 2 using a semiconductor DFB diode laser at 1.578 μm

One single semiconductor distributed-feedback (DFB) laser is used to demonstrate the possibility of si- multaneous detection of two different molecular species. Direct absorption and low-wavelength modulation (LWM) spectroscopy were employed to investigate weak overtone transitions of CO2 and CO at a wavelength of λ = 1578 nm. Sensitivity measurements under different conditions have been performed and the detection limit of the apparatus was measured to be less than 10 m T or r over a 1-m path length. In addition, we measured for the first time environmentally and spectroscopically relevant self-broadening and nitrogen- broadening coefficients for CO2 and CO in this spectral region and we discuss different possibilities for increasing the sensitivity of the apparatus.