SIMULTANEOUS DETECTION OF CO AND CO2 USING A SEMICONDUCTOR DFB-DIODE-LASER AT 1.578-MU-M

One single semiconductor distributed-feedback (DFB) laser is used to d emonstrate the possibility of simultaneous detection of two different molecular species. Direct absorption and low-wavelength modulation (LW M) spectroscopy were employed to investigate weak overtone transitions of CO2 and CO at a wavelength of lambda = 1578 nm. Sensitivity measur ements under different conditions have been performed and the detectio n limit of the apparatus was measured to be less than 10 mTorr over a l-m path length. In addition, we measured for the first time environme ntally and spectroscopically relevant self-broadening and nitrogen-bro adening coefficients for CO2 and CO in this spectral region and we dis cuss different possibilities for increasing the sensitivity of the app aratus.