The first demonstration of the correction of atmospheric turbulence by nonlinear phase-conjugation techniques is presented. It is shown that severely distorted and wandering beams can dynamically be corrected to near-diffraction limit and locked to a prescribed spatial position. These experiments were performed over a 100-M rooftop range. A beam is propagated over the range, becoming aberrated, enters a phase conjugator, is conjugated, and retraverses the atmospheric path canceling the aberrations. The conjugate signal is generated by the nonlinear optical process of four-wave mixing in sodium vapor at 5890 A. In this way the conjugate, or time reversed signal, is produced by a process involving no moving parts in contrast to conventional adaptive optics techniques involving deformable mirrors.

© 1983 Optical Society of America

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