Model for mutually pumped phase conjugation

A model is proposed and demonstrated for mutually pumped phase conjugation when two mutually incoherent laser beams pump each other, producing a pair of phase-conjugate beams through a cross-readout process. The model considers the buildup of two independent counterpropagating oscillations in a ring resonator containing two-beam-cbupling gain media. The experimental demonstration of the model using two photorefractive BaTiO3 crystals in a ring cavity gave simultaneous phase-conjugate images with good fidelity and no image cross talk. As expected, the counterpropagating oscillations were slightly detuned in frequency (∼1 Hz) from the corresponding pumping beams with frequency shifts related to the ring-cavity length. Frequency shifts were also observed in the phase-conjugate beams, with their magnitudes dictated by energy conservation for nondegenerate four-wave mixing.