In-situ Laser-based Diagnostics of Atoms, Molecules, and Particles Using Continuous Wave to Femtosecond-duration Lasers

Abstract

New developments in advanced laser-based diagnostics have enabled non-intrusive probing of reactive chemical species and particles in a variety of engineering applications, ranging from fundamental flames to advanced engines, explosions, and novel materials characterization methods. The first part of this talk outlines the applications of nanosecond-duration laser pulses in understanding combustion dynamics of various flames, characterizations of dust cloud explosions. In addition, a novel ultra-high-speed burst-mode laser system with repetition rates ranging from 10 kHz to 1 MHz, in detecting particles in energetic materials reactions is also discussed. In the second part of the talk, we will present our recent work in utilizing ultrashort, femtosecond-duration laser pulses for interference-free, kHz-rang imaging of atoms and molecules. Highly reactive atomic species such as H, O and N, as well as radicals such as CO and OH, play pivotal roles in chemical reaction pathways in combustion and plasma systems. Quantitative in-situ imaging diagnostics of these species are incredibly challenging because of their low number densities and laser-generated interferences. In recent years, we have developed a femtosecond two-photon laser-induced fluorescence method overcoming several of these challenges, especially in high-temperature, high-pressure turbulent combustion environments of practical relevance.

Speaker

Dr Yejun Wang is a research associate professor in the Institute of Mechanics at Chinese Academy of Science, China. His primary research activities are focused on the development and application of advanced optical and laser-based diagnostics for combustion, propulsion, plasma, and remote sensing applications. In recent years, he has made contributions to the development of ultrafast femtosecond-duration laser pulses in imaging measurements for highly reactive species, and the potential application of ultra-high-speed burst-mode laser system in high-turbulent combustion and supersonic/hypersonic flow fields. Dr Wang has published nearly 20 peer-reviewed journal articles and presented his work at numerous national and international conferences. He earned his PhD in Mechanical Engineering from Texas A&M University, College Station, United States, and then continued to work in the same laboratory as a postdoctoral researcher. He was awarded Ralph E. James Fellowship and Emil Buehler Aerodynamic Analog Fellowship.