Mid-Infrared Optical Cavity-Based Spectrometer for Multispecies Airborne and Ground-Based Atmospheric Monitoring

73193-Recent advances in both mid-infrared laser sources and ultrasensitive optical detection technologies promise to allow trace atmospheric species such as formaldehyde to be studied with unprecedented detail and accuracy. The availability of such instrumentation for both airborne and ground-based monitoring applications would have a wide ranging impact on our understanding of atmospheric chemistry and dynamics. The proposed solution combines a novel tunable high-power, single-frequency, mid-infrared laser source with an ultrasensitive optical cavity-based absorption method known as off-axis integrated cavity output spectroscopy. The combination of these two innovative technologies will allow many important atmospheric constituents to be monitored with unprecedented sensitivity (<25 pptv mixing ratio) in real time (<30 s), including formaldehyde, CO, ethylene, acetylene, and N2O. During Phase I, a widely tunable mid-infrared laser producing over 2 milliwatts of power in the 2.7 micron spectral region was constructed from all room-temperature solid-state components. This source was used in conjunction with off-axis integrated cavity output spectroscopy to achieve ultrasensitive detection of gas phase isotopic water. In Phase II, the basic laser design will be refined to produce in excess of 15 milliwatts in the 3.3 micron spectral region. The laser again will be used in conjuction with off-axis integrated cavity absorption spectroscopy to detect hydrocarbons and other species at the parts-per-trillion level. Commercial Applications and Other Benefits as described by awardee: The instrument should have a wide ranging impact on our understanding of atmospheric chemistry and dynamics. Commercial applications include trace gas monitoring, pollution monitoring, and industrial process monitoring.