Underwater irradiance fluctuations of a laser beam after transmission through a wavy sea surface

H. Michael Tulldahl

doi:10.1117/12.519769

22 September 2003 Underwater irradiance fluctuations of a laser beam after transmission through a wavy sea surface

H. Michael Tulldahl

Proceedings Volume 5149, Laser Applications in Medicine, Biology, and Environmental Science; (2003) https://doi.org/10.1117/12.519769
Event: International Conference on Lasers, Applications, and Technologies 2002, 2002, Moscow, Russian Federation

Abstract

The effects of surface waves on laser beam transmission through the sea surface are experimentaly examined. The purpose is to obtain experimental data for comparison with laser propagation models. Simultaneous measurements of the time and space variability of the air-sea interface are performed. A submerged screen, filmed by an underwater video camera, is used to measure the downwelling irradiance profiles. The measurements are made in calm winds, in a sheltered harbor environment. Calibrated values of downwelling irradiance are obtained by reference measurements in laboratory. Two significant consequences of transmission through the sea surface are investigated: beam width at different depths averaged over several surface wave periods, and surfce wave focusing or defocusing quantified by the irradiance fractional fluctuations (standard deviation divided by the mean). We compare the irradiance fractional fluctuations from our experiment with published data from underwater sunlight measurements and from laser beam simulations. The irradiance fractional fluctuations show a near-surface maximum and decay with depth. Low wind speed is expected to increase the fractional fluctuations caused by wave focusing effects. Our measurements qualitatively agree with the compared data, but exhibit larger fractional fluctuations.

Citation Download Citation

H. Michael Tulldahl "Underwater irradiance fluctuations of a laser beam after transmission through a wavy sea surface", Proc. SPIE 5149, Laser Applications in Medicine, Biology, and Environmental Science, (22 September 2003); https://doi.org/10.1117/12.519769

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