Colloquium: Mark Phillips

    Thursday, April 26, 2018 - 3:30pm - 5:00pm
    Meinel 307

    Infrared laser spectroscopy for rapid chemical sensing


    Infrared laser spectroscopy is a technique which measures characteristic vibrational and rotational absorption resonances for nearly any molecule, in both gas- and condensed-phases.  However, turning this technique into a practical and reliable sensor system presents many challenges.  For detection of trace gases, sensors must detect, identify, and quantify concentrations of various molecular species.  Enhancing signal strength via long absorption path lengths and reducing noise via modulation techniques is often required to detect trace concentrations.  At the same time, reducing drift in sensor signals is essential for reliable performance over long time scales.  Robust and real-time spectral analysis algorithms are needed to quantify gas concentrations in mixtures and avoid false detections.

    This presentation will discuss efforts over the past decade to develop high-performance trace gas sensors using rapidly-swept external cavity quantum cascade lasers.  The laser technology will be described, and its optimization for broad spectral tuning at high speed and high-resolution.  Sensor design and construction for point- and standoff-sensing configurations will be presented, as will results for detection of transient plume sources, complex chemical mixtures, and isotope ratios.

    Speaker Bio(s): 

    Dr. Mark C. Phillips is a senior-level scientist at Pacific Northwest National Laboratory (PNNL), leading research and development of laser spectroscopy and sensing techniques.  He received a Ph.D. in Physics in 2002 from the University of Oregon, where he worked in the lab of Hailin Wang researching quantum optics in semiconductor systems.  Following graduation, Mark was employed as a postdoctoral fellow at Sandia National Laboratory from 2002-2005, and studied quantum coherence effects in semiconductor quantum dots.  He joined PNNL in 2005, where he has developed high-performance external cavity quantum cascade laser systems for mid-infrared spectroscopy and sensing of trace gases, active hyperspectral imaging, and standoff detection of explosives.  In particular, Mark has led development of portable trace gas sensors based on external cavity quantum cascade lasers, taking them from initial conception to field deployment and testing.  He developed waveguide characterization techniques applicable to infrared wavelengths for mid-infrared photonics research based on chalcogenide glasses.  He has been a principal investigator and project manager for multiple research projects and he is currently leading investigations into optical spectroscopy in laser-induced plasmas, optical modeling and measurements of atomic and molecular spectra in high-temperature conditions, optical spectroscopy of solids and liquids for standoff detection, and new applications of quantum cascade lasers for spectroscopy and sensing.