Phase locking of two light beams in a phase conjugate mirror based on four-wave Mandelstam-Brillouin enhanced mixing is investigated. Such a mirror consists of two cells filled with a nonlinear medium. Two laser beams of orthogonal polarization pass through the first cell at a small angle to each other. One of them is then focused at the second cell with the same medium and is reflected from it due to stimulated Mandelstam-Brillouin scattering (SMBS). The reflected beam of orthogonal polarization returns to the first cell where a hypersound is excited as a result of the electrostrictive Interaction between the reflected beam and one of the incident beams of the same polarization. Each of the two incident beams is reflected from this hypersound in the direction opposite to the direction of the other incident beam propagation. This mutual scattering of the reflected beams at the same hypersound results in their phase locking. For this to take place, it is important that the incident beams have equal intensities and that the wave reflected from the second cell has a rather low intensity so as not to disturb the phase matching arising between the powerful beams when they are reflected from the hypersound in the first cell.

© 1989 Optical Society of America

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