Phase conjugation by low-power continuous-wave degenerate four-wave mixing in nonlinear optical polymer fibers

We report on the observation of phase conjugation (PC) using low-power, continuous-wave degenerate four-wave mixing in nonlinear polymer multimode fibers. The fibers are made of poly(methyl methacrylate) doped with Disperse Red 1 as the photosensitive chromophore. With a power less than 2.5 mW at wavelength 633 nm for each beam inside the fiber, a maximum PC reflectivity of 1% is obtained. Phase conjugation is observed for both parallel and orthogonally polarized probe and pump beams. Experimental results show that polarization and intensity profile are preserved in the PC wave. The predominant phase conjugation wave is attributed to the formation of sub-refractive-index gratings inside the fibers. (C) 2004 American Institute of Physics.