Portable mid-infrared gas sensors: Development and applications

Several novel compact architectures of diode laser based absorption gas sensors have been developed, characterized and applied to real world applications. The motivation for this research has been the need to develop highly sensitive, selective and rapid response gas sensors that operate reliably in a non-laboratory environment. The gas sensors utilize rare earth doped fiber amplified near infrared diode lasers and are difference frequency mixed in periodically poled LiNbO3 to generate narrow linewidth muW to mW-level mid infrared light in the molecular fingerprint region from 3 to 5 mum. In particular, the spectroscopic performance of an automated widely tunable (3.3--4.4 mum) multi-species and a high-power single species (3.5 mum) gas detection sensor are discussed. Sensitive, selective and real-time detection of over 10 gas species including CH4, H2CO, CO2, CH 3OH, NO2, N2O; SO2, HCl, C6H 6, and H2O using extractive gas sampling in a multi-pass cell was demonstrated. The gas sensors were used for an evaluation of a trace contaminant catalyst system at TDA Research, Wheat Ridge, Colorado, and successfully applied to the detection of volcanic gases at Masaya volcano, Nicaragua