We have investigated five types of atmospheric optical-turbulence inner scales for their effects on normalized laser irradiance variance in the Rytov and early saturation regimes: (1) zero inner scale, (2) Gaussian inner scale, (3) Hill’s viscous-convective enhancement inner scale, (4) Frehlich’s parameterization of the viscous-convective enhancement, and (5) turbulence spectrum truncation because of the discrete grid representation. Wave-optics computer simulations yielded normalized irradiance variances within 2% of the results from numerical integrations of the Rytov–Tatarskii predictions. In the Rytov regime a Gaussian inner scale reduces the normalized irradiance variance compared with the zero-inner-scale case, and the viscous-convective inner scale first raises, then lowers the irradiance variance as the inner-scale size increases. In the saturation regime all inner-scale models increase the intensity variance for a spherical wave.
© 1994 Optical Society of America
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