31 January 2001 Laser beam propagation through a jet aircraft engine's exhaust
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Abstract
One-, half- and ten-micron wavelength radiation was used to study laser beam propagation through turbojet aircraft engine exhaust. A feature of the methods was that instantaneous distributions of the beam intensity were recorded during the experiment. Analysis of experimental data has shown that turbulent stream has a dramatic impact on spatial characteristics of a laser beam. For example, the averaged angle divergence for 30-mm one-micron beam becomes about ten times higher than its diffraction divergence. Results of different experiments showed that the average angle divergence of the narrow one-micron beam disturbed by the jet plume is several times less than that of the ten-micron beam which is characterized by a large diffraction divergence, and that of the half-micron beam stronger subjected to disturbances. Experiments in which the beam crossed the plume close to a nozzle at (phi) = 90 degree(s), 45 degree(s) and 10 degree(s) have shown that angular divergence increases with decreasing cross-angle, practically doubling the value when coming from the maximal angle of (phi) = 90 degree(s) to the minimal (phi) = 10 degree(s). Mathematical models have been derived, based on the experimental studies. The value of the structural characteristic in a turbulent stream is in the range of Cn2~10-9m-2/3.
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Vladmir S. Sirazetdinov, Anatoly D. Starikov, David H. Titterton, "Laser beam propagation through a jet aircraft engine's exhaust", Proc. SPIE 4167, Atmospheric Propagation, Adaptive Systems, and Laser Radar Technology for Remote Sensing, (31 January 2001); doi: 10.1117/12.413815; https://doi.org/10.1117/12.413815
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