title: Investigation of optical fibers for high-repetition-rate, ultraviolet planar laser-induced fluorescence of OH.
abstract: We investigate the fundamental transmission characteristics of nanosecond-duration, 10 kHz 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, 283 nm UV irradiation. For 10 kHz laser pulses, two-photon absorption is strong and LIDTs are low, as compared to those of laser pulses propagating at 10 Hz. The fiber characterization results are utilized to perform single-laser-shot, OH-PLIF imaging in pulsating turbulent flames with a laser that operates at 10 kHz. 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.
authors.affiliation: Spectral Energies, LLC, 5100 Springfield Street, Suite 301, Dayton, Ohio 45431, USA.
authors.forename: Paul S
authors.initials: PS
authors.lastname: Hsu
authors.forename: Waruna D
authors.initials: WD
authors.lastname: Kulatilaka
authors.forename: Sukesh
authors.initials: S
authors.lastname: Roy
authors.forename: James R
authors.initials: JR
authors.lastname: Gord
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D017665:Hydroxyl Radical / Q000032:analysis* / Q000737:chemistry* / Q000528:radiation effects; D007834:Lasers; D055100:Optical Fibers; D013050:Spectrometry, Fluorescence / Q000295:instrumentation*; D014466:Ultraviolet Rays
chemical_list: D017665:Hydroxyl Radical