Four-wave hypersonic reversing mirrors in the saturation regime

A four-wave hypersonic reversing mirror pumped up pulses of 5 J energy and 30 nsec duration was used for wavefront reversal of signals of ~ 10 −4 J energy and 30 nsec duration, producing a reversed wave of 1 J energy but of duration reduced to 10 nsec. The relative fraction of the wave which was reversed amounted to ~ 80%, but this decreased to 10% when the signal was lowered to ~6 × 10 −10 J and the energy reflection coefficient increased to 10 6 .