Transportable automated ammonia sensor based on a pulsed thermoelectrically cooled quantum-cascade distributed feedback laser

A compact ammonia sensor based on a 10-μm single-frequency, thermoelectrically cooled, pulsed quantum-cascade laser with an embedded distributed feedback structure has been developed. To measure NH₃ concentrations, we scanned the laser over two absorption lines of its fundamental v₂ band. A sensitivity of better than 0.3 parts per million was achieved with just a 1-m optical path length. The sensor is computer controlled and automated to monitor NH₃ concentrations continuously for extended periods of time and to store data in the computer memory.