Abstract

Despite its relatively rare use in such problems, we have found that coherence theory explains the major phenomenon associated with enhanced backscatter (partial phase conjugation processes). Consider the case where a coherent wave field is scattered by a moving diffuser and then reflected back through the same diffuser by an ordinary mirror. Through the use of coherence theory we have shown that, to within a complex proportionality factor, the incident wave field can be inferred from coherence measurements made on the doubly scattered wave field. Specifically, the mutual intensity of the doubly scattered wave field is given by J₁₂ = J_incoherent + J_coherent. The first term corresponds to a spatially incoherent wave field of the kind that would be observed if the incident wave field were scattered by two different moving diffusers. In the far field this incoherent contribution produces an essentially uniform background intensity. The second term, on the other hand, corresponds to a wave field with exactly the same coherence properties as the incident coherent wave field. If the incident wave is a uniform plane wave, the doubly scattered wave field contribution corresponding to J_coherent will in the time average focus to a point of light in the far field.

© 1991 Optical Society of America