Acetylene measurement using quantum cascade lasers at 14μm

The monitoring of acetylene (C 2 H 2 ) concentrations is important for many chemical processes. Industrial trace gas measurements are usually performed using gas chromatographs (GC) which have time constants of several minutes. Optical analyzers are expected to yield faster response times with lower maintenance costs. We investigated the use of quantum cascade laser (QCL) spectroscopy in the 14μm range for the sensitive and fast detection of C 2 H 2 . This spectral range is favorable, as it avoids spectral interferences by other components which could be present in typical process gases. We developed new custom DFB QCLs and characterized their spectral properties. We determined the performance of our QCL gas analyzer setup and demonstrate a noise equivalent concentration of 10 ppb in 20 s average time.