Adaptive-optics systems that use a return-wave concept for compensating for atmospheric turbulence distortions on a transmitted laser beam usually assume that the phase profile of the sensed radiation equals the appropriate phase profile for the laser wavelength. Certainly geometrical optics would predict this to within a scale factor directly related to the index of refraction of the air at the different wavelengths. Diffraction manifests itself in an interference phenomenon and amplitude modulation. Shorter wavelengths are more quickly affected than the longer wavelengths. When amplitude scintillation becomes important, the geometrical-optics-predicted wave-front distortions may differ from the real diffracted beam. The problem reduces to considering the phase difference measured at two different wavelengths after propagating through the same turbulence, and this paper describes these differences.
© 1982 Optical Society of AmericaPDF Article