We analyze the frequency-shifted conjugate beam generated by nearly degenerate four-wave mixing in an array of single-mode waveguides. We show that if the array sufficiently samples the signal beam, a high-quality conjugate will be generated when the pump beams are counterpropagating. The ability of a waveguide mode to couple to incoming beams over a range of incident directions relaxes the strict phase-matching requirement present in bulk-media four-wave mixing. A shift in the propagation direction of one of the pump beams changes the propagation direction of the generated beam while maintaining the spatial phase coherence.
© 1989 Optical Society of America
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