Investigation of optical fibers for high-repetition-rate, ultraviolet planar laser-induced fluorescence of OH.
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We investigate the fundamental transmission characteristics of nanosecond-duration, 10kHz repetition rate, ultraviolet (UV) laser pulses through state-of-the-art, UV-grade fused-silica fibers being used for hydroxyl radical (OH) planar laser-induced fluorescence (PLIF) imaging. Studied in particular are laser-induced damage thresholds (LIDTs), nonlinear absorption, and optical transmission stability during long-term UV irradiation. Solarization (photodegradation) effects are significantly enhanced when the fiber is exposed to high-repetition-rate, 283nm UV irradiation. For 10kHz laser pulses, two-photon absorption is strong and LIDTs are low, as compared to those of laser pulses propagating at 10Hz. The fiber characterization results are utilized to perform single-laser-shot, OH-PLIF imaging in pulsating turbulent flames with a laser that operates at 10kHz. The nearly spatially uniform output beam that exits a long multimode fiber becomes ideal for PLIF measurements. The proof-of-concept measurements show significant promise for extending the application of a fiber-coupled, high-speed OH-PLIF system to harsh environments such as combustor test beds, and potential system improvements are suggested.
author list (cited authors)
Hsu, P. S., Kulatilaka, W. D., Roy, S., & Gord, J. R.
complete list of authors
Hsu, Paul S||Kulatilaka, Waruna D||Roy, Sukesh||Gord, James R