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8 November 1996 Fluctuation spectra for an infrared laser beam propagating horizontally in the open atmosphere
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Fluctuation for the laser beams of wavelengths on and off absorption lines were recorded, and the power spectral density function for each record was calculated, and the co- spectrum of the two records as well. A system with a 7 micrometers band lead-salt semiconductor laser that can be changed its wavelength were made up for examining the correlation between the fluctuation of the laser beam of 7859.50 nm and of 7860.27 nm. The former hit two absorption lines of water vapor located at 7859.49 nm and 7859.51 nm and the later were out of them. This experiment was carried out on the in- door corridor using a round-trip propagation path. Three electrical heaters and a humidity source set on the floor under the propagation path, which disturbed the temperature and humidity of the environment. In addition a fan agitated the air. As the results, the power spectral density function for the on-line data had a peak in the lower frequency region at which a contribution of the absorption is strong. The peak frequency agree with a predicted frequency by the integral length scale L0. Moreover, the co-spectrum increased in the frequency region less than 0.1 Hz. On the contrary, it decreased dramatically in the frequency region higher than 10 Hz. The results tell us the lower frequency region reflects the transportation of water vapor in the air.
© (1996) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Naoki Kagawa, Osami Wada, and Ryuji Koga "Fluctuation spectra for an infrared laser beam propagating horizontally in the open atmosphere", Proc. SPIE 2815, Optical Radiation Measurements III, (8 November 1996);


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