Experimental study of optical properties of Black Sea water for laser probing applications
M.A. Karpov1, N.V. Tcherniega1, A.D. Kudryavtseva1, S.F. Umanskaya1, N.A. Kleopova1, K.V. Kulikovsky2, T.V. Baikova2
1P.N. Lebedev Physical Institute of the Russian Academy of Science, Moscow, Russia
2Moscow Technological University, Moscow, Russia
Keywords: seawater, Black Sea, light scattering, laser probing of water surface
Abstract
The objective of this study was to determine an optimal radiation wavelength for scanning marine surface from air, which provides minimal radiation absorption, parasitic fluorescence, beam divergence, and scattering in the water column. These parameters depend on the probing laser type used. The research focused on water samples from the Black Sea collected 200 m from the shore immediately before the experiment and water samples stored for one year in light-protected hermetically sealed containers. For both sets of samples, the following were examined: scattering phase function, spectral transmission coefficients, laser beam divergence, particle size distribution of organic matter in the samples, and its effect on fluorescence spectra. Commercial semiconductor lasers with wavelengths of 450, 520, and 660 nm were used. The study shows a 450-nm laser to be optimal for underwater probing tasks since it exhibits the lowest radiation attenuation in the water column (0.5 dB/m), the smallest scattering spot, and minimal fluorescence. Organic particles do not significantly affect hydro-optical properties of seawater in the samples both immediately collected before the experiment and stored for one year. The results can be used in the design of above-water and underwater laser probing systems for marine surface analysis.
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