Polarization-independent energy exchange and phase conjugation

A polarization independent energy exchanger transfers optical energy from a first coherent beam of optical energy to a second coherent beam of optical energy where the second beam is coherent with respect to the first beam, the second beam is counterpropagating with respect to the first beam, and the second beam possesses substantially the same polarization as the first beam. The energy exchanger includes a nonlinear optical uniaxial crystal having electro-optic coefficients r13 and r23 of equal magnitude and having a sufficiently large photorefractive charge density to achieve efficient contradirectional two-beam coupling, independent of the polarization states of the first and second beams. The crystal is oriented to receive the first and second beams therein such that the optic axis of the crystal is aligned parallel to the propagation directions of the first and second beams. The invention also envisions a polarization-independent backscattering phase conjugator for transferring optical energy from a first coherent beam of optical energy to a second coherent beam of optical energy where the second beam is the counterpropagating phase-conjugate reflection of the first beam. In this embodiment, a nonlinear optical uniaxial is provided with electro-optic coefficients r13 and r 23 of equal magnitude and having a sufficiently large photorefractive charge density to achieve efficient phase-conjugate backscattering, independent of the polarization state of the first beam.