Abstract
High-energy burst-mode lasers have enabled the development of kHz–MHz rate, multi-dimensional diagnostics for characterizing highly dynamic and transient phenomena in reacting and non-reacting flows. In addition to their high power, which enables frequency conversion and tunability over a wide range of the electromagnetic spectrum, the master oscillator power amplifier (MOPA) architecture enables ample flexibility in the shape of the pulse train through selection of the oscillator temporal and spectral characteristics. This article reviews both the development and application of burst-mode lasers, whose design has evolved significantly over a half century to include pulse widths from 250 femtoseconds to 50 microseconds, burst durations up to 0.1 s for sequences of up to 100,000 pulses, energies up to 2 J per pulse, and frequency conversion from the deep ultraviolet to the near-infrared, and repetition rates up to 5 MHz. Such performance characteristics have laid the foundation for the advancement of a wide array of ultra-high-speed laser-based diagnostics including (i) linear techniques such as laser-induced fluorescence, particle image velocimetry, Mie scattering, Rayleigh scattering, Raman scattering, and laser-induced incandescence; (ii) nonlinear techniques such as coherent anti-Stokes Raman scattering, multiphoton fluorescence, and molecular tagging velocimetry; (iii) and multi-dimensional imaging from planar (2D) slices to volumetric (3D) tomography. The development of high-power and multileg burst-mode lasers has also enabled simultaneous multi-parameter measurements (temperature, species, and velocity) and extension to 4D imaging (3D in space + time) using many of the aforementioned techniques. More specialized configurations include multi-pulsing (from doublets to quadruplets), pulse-to-pulse wavelength tuning, and multi-pulsewidth approaches combining femtosecond and picosecond amplification. The pace of development and transition to robust operation continues to expand through advances in opto-electronics, predictive modeling of laser performance, and more compact/portable laser architectures. Future prospects include growing utilization of burst-mode laser-based diagnostics in hypersonic flows, detonations, energetic reactions, plasmas, high-pressure combustion, turbulent flames, and other extreme aerodynamic and thermochemical environments.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call