Turbulence spectrum effect on wave temporal-frequency spectra for light propagating through the atmosphere

It has been widely accepted and taken far granted that when a light wave propagates through a locally isotropic turbulent atmosphere the temporal-frequency spectra of the log-amplitude, phase, and angle-of-arrival fluctuations at high frequency have a power law behavior with a scaling index -8/3. However, our experimental results with laser irradiance fluctuation show that if the high-frequency temporal spectrum is fitted to a power law, the scaling index deviates from -8/3 in many cases. Thus we take a new look at the wave propagation theory through numerical evaluation, using Kolmogorov, von Karmin, Hill, and Frehlich turbulence spectrum models. It is found that the main contribution of the turbulence spectrum to the wave log-amplitude, phase, and phase-difference high-frequency temporal spectra is in the dissipation range rather than in the inertial range. Consequently, the turbulence inner scale plays an important role in the wave temporal spectra. The larger the inner scale and the smaller the wind velocity, the more noticeable the effect of the turbulence spectrum in the dissipation range on the wave temporal spectra. (C) 1999 Optical Society of America [S0740-3232(99)00411-1].