Four-wave wavefront reversal in a coded reference wave field

A quantitative theory is developed for wavefront reversal in four-wave interaction in a field of coded reference waves, i.e., of waves having substantial fine-structure spatial inhomogeneity. It is found that by using conjugate coded waves, it is possible to reverse a weak signal with transfer of up to $50\%$ of the reference wave energy to the reversed component and to eliminate the self-focusing instability of conventional four-wave wavefront reversal. Possible methods of producing conjugate coded waves are indicated.