Photoacoustic CO2 sensor based on a DFB diode laser at 2.7 μm

We present a new detection scheme for carbon dioxide (CO2) based on a custom-made room temperature distributed feedback (DFB) diode laser at 2.7 mu m, currently representing one of the lasers with the highest emission wavelength of its kind. The detector's especially compact and simple set-up is based on photoacoustic spectroscopy (PAS). This method makes use of the transformation of absorbed modulated radiation into a sound wave. The sensor enables a very high detection sensitivity for CO2 in the ppb range. Furthermore, the carefully selected spectral region as well as the narrow bandwidth and wide tunability of the single-mode laser ensure an excellent selectivity. Even measurements of different CO2 isotopes can be easily performed. This enables applications in industrial sensing and medical diagnostics (e. g. C-13-breath tests).