Heterodyne measurements of light propagation through atmospheric turbulence

Experiments on the phase perturbation of optical beams due to atmospheric turbulence were carried out using coherent radiation at 6328 Å, and 1.15 µ. The measurements were accomplished using a modulated interferometer to produce Doppler beats between a reference beam and one reflected from a plane mirror at a distance. This paper presents preliminary results of the phase measurements taken over total horizontal paths of 4.0 km and 23.8 km. The experimental data were consistent with a propagation theory based on the accepted model of atmospheric turbulence. Perturbation free apertures up to 10 cm were observed in good seeing conditions and as low as 1 mm under poor conditions. The corresponding variance of refractive index of the atmosphere showed a magnitude and diurnal variation consistent with published observations of temperature fluctuations.