The University of Arizona: Plumes, flames, and explosions: molecular sensing in extreme environments using tunable infrared lasers

OSC Colloquium presented by Mark C. Phillips Solving problems with optical spectroscopy often requires measurement of highly dynamic systems and probing extreme physical/chemical environments in the presence of turbulence and high temperatures. In this presentation, I will discuss challenges for spectroscopy in these dynamic systems, and how high-speed tunable lasers overcome these issues. Molecular species and their temperatures are detected through their broadband infrared absorption spectra, and machine-based spectral analysis methods are used to extract quantitative chemical and physical information from complex systems. Instrumentation enabling these measurements relies on custom-built swept-wavelength external cavity quantum cascade lasers (swept-ECQCLs) developed by Dr. Phillips, which provide a unique combination of narrow-linewidth and high-speed scanning over broad spectral regions. Examples of sensing extreme environments using swept-ECQCLs and associated sensors will be presented which include: (1) Thermal decomposition of chemical warfare simulants exposed to explosions, (2) In-situ measurement of methane flaring efficiency, and (3) Remote detection of trace gas plumes propagating through complex terrain. Bio Mark C. Phillips is currently an associate research professor at the James C. Wyant College of Optical Sciences, University of Arizona. His research interests include developing new techniques and instrumentation for laser-based spectroscopy and sensing of materials in all phases of matter. He is currently developing swept-wavelength external cavity quantum cascade lasers (ECQCLs) for high-performance infrared spectroscopy and sensing of gases and solids and uses these systems for measurements around the country. Applications include standoff chemical plume detection, trace gas sensing, and measurements in extreme environments including combustion and explosive fireballs. He is also researching new laser spectroscopy techniques for measurement of atoms in laser-induced plasma systems, including isotopic resolution and standoff detection capabilities. To enable quantitative analysis, he develops custom spectral fitting algorithms, especially for high-temperature plasma and explosive fireball conditions. He received a Ph.D. in Physics in 2002 from the University of Oregon, was employed as a postdoctoral fellow at Sandia National Laboratory from 2002-2005, and was a senior-level scientist at Pacific Northwest National Laboratory from 2005-2018. From 2019-2024 he was the chief scientist at a startup company, where he led efforts toward commercialization of the swept-ECQCL technology. He is a fellow of Optica.