EFFICIENCY AND QUALITY OF 4-WAVE PHASE-CO NJUGATION OF A SIGNAL WITH A TIME-DEPENDENT SPATIAL STRUCTURE

It is demonstrated theoretically and experimentally that, in four-wave phase conjugation of a spatially incoherent speckle signal, the refle ction coefficient and the conjugated fraction fall on increase in the rate of change of the spatial structure of the-speckle beam. The law o f decay of both these parameters is the same for media with an exponen tial grating erasure rate, but in the-case of double-exponential relax ation the conjugated fraction of the signal decreases much more slowly than the reflection coefficient. Experimental results show that the s tandard model of deep trapping levels can describe the kinetics of for mation of dynamic gratings in a nominally pure crystal of strontium ba rium niobate, but the presence of shallow trapping levels has to be ta ken into account for doped crystals.