Abstract

We have demonstrated a passive device that removes in one pass the aberrations incurred by a light wave in propagating through a distorting medium.¹ Light from the extended object of interest and a nearby reference point source pass through a thin phase aberrator located near the entrance pupil of the optical system. By imaging the aberrator into the nonlinear medium, the image-bearing and reference wavefronts at the nonlinear medium contain information about the aberrator only in identical exponential phase factors, which cancel out in the nonlinear polarization induced in the nonlinear medium. Consequently, the wave generated by this nonlinear polarization is free of the effects of the aberration and can be split off to recover the unaberrated image. This aberration-correction device is an implementation using real-time degenerate four-wave mixing of an idea advanced by Goodman et al.² One example of an application of this method is the improvement in the quality of astronomical observations by removing some of the effects of atmospheric turbulence. A significant component of the distortion incurred by astronomical images occurs at the interface between the telescope structure itself and the surrounding atmosphere. The principal hindrance to implementing this scheme is the difficulty of nonlinear mixing of light which is weak and temporally or spatially incoherent, or both, as in the case of starlight.

© 1988 Optical Society of America