Fiber-optic delivery of high-peak-power Q-switched laser pulses for in-cylinder flow measurement

Timothy J. Stephens, Martin J. Haste, David P. Towers, Martin J. Thomson, Mohammed R. Taghizadeh, J. D C Jones, Duncan P. Hand

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)


A bundle of optical fibers was constructed to deliver Q-switched frequency-doubled Nd:YAG laser pulses for the purpose of particle image velocimetry. Data loss that is due to fiber speckle was reduced by ensuring that each fiber was different in length by more than the coherence length of the laser being delivered. Hence, their speckle patterns will overlap but not interfere, producing more even illumination that is shown to reduce data loss. A custom-made diffractive optical element and careful endface preparation help to reduce damage to the fibers by the required high peak powers. With this method, pulse energies in excess of 25 mJ were delivered for a series of experimental trials within the cylinder head of an optically accessed internal combustion engine. Results from these trials are presented along with a comparison of measurements generated by conventionally delivered beams. © 2003 Optical Society of America.

Original languageEnglish
Pages (from-to)4307-4314
Number of pages8
JournalApplied Optics
Issue number21
Publication statusPublished - 20 Jul 2003


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