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A new two-wave-mixing interaction with gain through a Bi(12)SiO(20) liquid-crystal light valve is presented. We show that the diffraction of a pump beam in the direction of a weak signal leads to a net amplification of the signal beam, with no need for a phase shift between the interference pattern and the induced index grating. A two-wave-mixing gain of 10 and a 150-ms response time are obtained with a 8.8-microm -thick liquid-crystal layer, a total intensity of the interacting beams of only 200 muW/cm(2), and an ac external voltage of +/-6 V . Image amplification is also demonstrated.

Pulse propagation in optical fibers may electrostrictively excite acoustic waves as a result of cladding Brillouin scattering, transversally propagating with respect to the fiber axis in the fiber's cladding, and mechanical coating. We show, for the first time to our knowledge, experimentally and theoretically that these transverse resonances within finite frequency ranges may cooperatively couple with the acoustic longitudinal modes of a fiber resonator, giving rise to stable trains of either spread or compressed three-wave Brillouin solitons and propose a first stability map for the rich four-wave dissipative dynamics.