Bidirectional laser cavity solitons

Cavity solitons in optical systems have been studied for two decades in a large variety of optical systems. In principle, bidirectional lasers can emit only unidirectionally in steady state, as the two-mode solution (non null steady state in the two possible emission directions) is an unstable solution (winner-takes-all competition prevents the bidirectional cw emission). But for a wide aperture cavity this is not necessarily true as, in different regions of the transverse (with respect to the propagation axis) direction, emission in different propagation directions could occur if the fronts separating these domains are stable. In fact this is exactly what happens when the cavity losses for the two propagation directions are different in a few per cent.