MAE Seminar: Pumping Air - FLEET, Radar REMPI and Backward Lasing - New Methods for Measuring Flow Properties and Contaminants in Air

Abstract:  We breathe, live in and fly through air, but we know little about it since it is transparent. What is in the air can affect our health and provide warnings of the presence of hazardous materials including explosives and narcotics. The motion of air around aircraft produces lift, but, at high speeds, turbulent air can cause excess heat loading and shock interactions can lead to component failure. The design of advanced aircraft and the development of validated computational fluid dynamic models require the knowledge of airflow properties.

This talk will present new methods for the measurement of air including trace contaminants and transport properties. Femtosecond Laser Electronic Excitation Tagging (FLEET) creates points, lines, crosses or more complex patterns in air that can be imaged at up to megahertz rates as they move and distort with the flow. This approach is of use for ground and flight-testing as well as for model development and validation. Radar REMPI is a method for high sensitivity detection of trace species in air that uses the combination of selective laser ionization and radar detection. Sensitivities to trace contamination can exceed tens of parts per billion. Backward lasing in air is achieved by excitation of either nitrogen or oxygen and leads to a method for creating a remotely located lasing region in air that sends a laser beam back. This “round trip” capability opens new approaches to pollution and trace species detection. These methods all use nonlinear optical interactions and take advantage of short-pulsed laser properties. 

Biography:  Professor Miles received his Ph.D. in 1972 from Stanford University with a thesis in the area of nonlinear optics. He served on the faculty at Princeton from 1972 until his retirement in 2013, and he continues to oversee his research group as a research staff member and professor emeritus. From 1980 to 1996 he served as chair of engineering physics at Princeton. His research focuses on the use of lasers, electron beams, low temperature plasmas, microwaves and magnetic devices to observe, control, accelerate, extract power and precondition gas flows for subsonic, supersonic and hypersonic fluid dynamics, combustion, propulsion and homeland defense applications. His research group is widely recognized for inventing new linear and nonlinear optical diagnostics, developing new understanding of plasma aerodynamic and combustion interactions and exploring new concepts for hypersonic ground-test facilities. Miles is a member of the National Academy of Engineering and a Fellow of the AIAA and the Optical Society of America. He serves on the Hertz Foundation Board of Directors, the Pacific University Board of Trustees and the Air Force Scientific Advisory Board. He was the recipient of the AIAA Aerodynamics Measurement Award and Medal in 2000 and the AIAA Plasma Dynamics and Lasers Award and Medal in 2012.