Wavelength Dependence of Laser-Beam Scintillation*

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Abstract
An experiment has been performed to confirm the proportionality between log-amplitude variance and the 7/6 power of wavenumber predicted by Tatarski for horizontal propagation from a spherical-wave transmitter to a point detector. The validity of this proportionality was tested for two wavelengths: 0.632 and 10.6 µ. Beams from a helium-neon and a CO2 laser were simultaneously transmitted over a folded 1.2-km horizontal path and were detected with a photomultiplier and a gold-doped germanium detector. The primary scintillation statistic, log-amplitude variance, was evaluated for each wavelength with a digital computer and the ratio of variances at 0.632 and 10.6 µ was found to be in close agreement with predictions. Power spectral density, autocorrelation, and cumulative probability density were also evaluated for each wavelength. Scintillation statistics at 10.6 µ were found to be log normal, as in the visible.