Eckhaus instability induced by nonuniformities in a laser -: art. no. 061801

We show that the Eckhaus instability induced by spatial nonuniformities, observed in hydrodynamics, can also destabilize optical systems. On the example of a one-dimensional parametric system (a modulated multimode laser), we show numerically that the nonuniformities select a wave number outside the Eckhaus-stable band, leading to periodic or irregular phase slips. The instability is confirmed experimentally by using a modulated fiber laser.