Pulse-Burst Lasers: Towards High-Speed Diagnostics in Reacting and non-Reacting Flows

Understanding gas-phase combustion reactions in turbulent flows requires high-speed planar imaging with multi-kHz frame rates. Continuously pulsed laser systems are insufficient to provide the energy needed for measuring key performance parameters. The alternative to continuously operated pulsed lasers are burst-mode lasers, which produce short bursts of high-energy pulses up to MHz rates. Recently our team has developed burst-mode lasers capable of providing up to 400 J per burst, lasers with extended burst duration up to 100 ms, and pulse duration from 100 ps to 10 ┬Ás. Here we describe the latest advances in burst-mode laser technology and its applications. Specific examples of burst-mode laser diagnostics in reacting and non-reacting flows will be presented including PIV, stereo PIV, and PLIF of formaldehyde, acetone, and OH in model combustors as well as in large-scale facilities. The laser energies achievable with this new laser architecture can also be used for Rayleigh scattering, as well as for pumping an optical parametric oscillator (OPO) to access a variety of other combustion intermediates, such as CH, OH, and NO. The long burst duration render new burst-mode architecture as an alternative for continuous pulse lasers in combustion and non-reacting flows diagnostics.