A review of Brillouin-enhanced four-wave mixing

When a Brillouin-shifted signal interacts with a two strong counterpropagating pump beams in a Brillouin active medium, a conjugate field will grow exponentially in time until it depletes the power of the pump beams and hence produce very high reflectivities (>10/sup 6/). The technique can be used to conjugate very weak signals (<10/sup -13/ J), or alternatively a large fraction of the pump power can be transferred into the conjugate beam. A review of the technique is presented and aspects such as the exponential growth rate, the minimum signal requirement, the beam quality, and the threshold for parasitic oscillation between the four-wave mixing cell and a reflecting surface are discussed.<>