Observation of extreme nonreciprocal wave amplification from single soliton-soliton collisions

We report the observation of strong nonreciprocal soliton amplification mediated by a Raman-scattering-like effect in single isolated collisions. A pump soliton is found to lose the greater part of its energy to a signal soliton, irrespective of the pump-signal relative amplitude. The result is an efficient rectifying mechanism able to accumulate energy into extreme waves. Experiments are carried out through photorefractive soliton two-wave mixing with a gain coefficient of up to 80 cm(-1) that emerges in conditions of nonlinear response, leading to the formation of rogue waves.