1790nm tunable laser for VOC monitoring

Air toxics, which include a number of volatile organic compounds (VOCs), have been linked to severe health impacts ranging from asthma exacerbations to cancer and premature deaths. In many cases, emissions are localized, and are particularly of concern for communities near industrial sites (which tend to be disproportionately low-income, often with predominantly indigenous or minoritized residents). In order to identify and manage health risks from exposure to air toxics, the EPA has called for high-sensitivity, high-specificity air monitoring technologies to provide real-time, continuous measurements of VOC concentration at the neighborhood level. Freedom Photonics is proposing the development of a widely tunable diode laser source, which is a key component of an ultra-sensitive broadband near-infrared (NIR) spectrometer. To date, incorporating our tunable lasers into our commercial partner’s compact, backpack?sized instrumentation has enabled sub-parts per billion detection of ethylene oxide. (The ethylene oxide instruments are currently being evaluated by the Georgia EPA in ambient monitoring applications.) The longer-wavelength tunable laser we have proposed will cover NIR absorption bands for more VOCs, and instruments incorporating multiple overlapping tunable laser sources will be capable of observing more spectral features simultaneously. Quantification of more gases in mixtures with improved specificity extends continuous monitoring capabilities to detect leaks of multiple air toxics in real time. Relative to current EPA methods for volatile toxic organic compound determination, broadband NIR spectroscopy is better suited to ambient monitoring, has a lower detection limit, and does not require sample conditioning. Most current EPA toxic organic determination methods require sample preparation in order to prevent chromatography column contamination – this precludes continuous ambient monitoring, and time consuming chromatographic separation limits sample throughput. Many compounds with similar functional groups may co-elute; fitting multiple peaks introduces more error into quantification by chromatography peak integration. Co-elution also complicates mass spectrometry interpretation, where fragmentation analysis may be needed to distinguish structural isomers. Broadband NIR spectroscopy offers complementary characterization, which can reduce uncertainty when matrix interference is problematic for present organic air toxics methods. The tunable diode laser spectroscopy market was $450M in 2019, and our capabilities with the proposed new source will expand relevance to other industries. Beyond environmental monitoring, industrial hygiene, and public health, which represent global concerns, we foresee applications in chemical process monitoring and oil/gas pipeline monitoring, as well as medical imaging like optical coherence tomography. Our tunable lasers are also suitable for airborne LIDAR applications such as foliage mapping.