Ultrashort-Pulse Laser Diagnostics for Combustion in Extreme Environments
14:00 - 14:30
Level 0 lecture hall between Al-Jazri and Al-Kindi (buildings 4 and 5)
Laser diagnostics have a long history of enabling fundamental and applied combustion research, providing noninvasive space- and time-resolved measurements of virtually any parameter of interest, and offering two- and even three-dimensional imaging capabilities. Many of these techniques have employed nanosecond-duration pulsed lasers or continuous-wave laser systems.
While powerful, diagnostics based on these laser sources exhibit limitations in extreme environments, such as high-pressure and particle-laden flames. Short-pulse diagnostics based on femtosecond and picosecond laser sources offer a multitude of advantages for measurements in extreme environments. Pulse durations are often much shorter than time scales for collisional effects to take hold, simplifying spectroscopic measurements in elevated-pressure environments, and the extremely high peak powers available often permit detection at much lower pulse energies, minimizing interferences from laser-induced breakdown and photolysis. Braodband, transformlimited bandwidths offered by femtosecond sources provide efficient, low-noise driving of multiphoton processes, which significantly improves signal-to-noise and measurement precision. This talk will provide an overview of the advantages of short-pulse lasers for combustion and gas-phase diagnostics, followed by the specific examples of femtosecond/picosecond coherent anti-Stokes Raman scattering (CARS) in particle-laden and high-pressure flames and laser-induced fluorescence (LIF) for background-free imaging.