Efficiency of phase conjugation for highly scattered light

Abstract We present experiments demonstrating reciprocity for conjugation of highly scattered light; if a fraction η of the total scattered light is incident on a phase-conjugate mirror having reflectivity ϱ, then a fraction ϱ η 2 returns back through the scatterer as a phase-conjugate wave, with the remaining fraction ϱ ( η − η 2 ) being lost due to scattering. Low efficiency results from inability to gather a large fraction of scattering, but the efficiency is higher than is possible without conjugation.