Photoacoustic CO 2 detection 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 μm, currently representing the laser 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 could enable future applications of this spectroscopic sensor in medical diagnostics (e.g. ¹³C-breath tests).