back and forth oscillations Localized structures (in optics or not) are usually studied in a context of bistability. That clearly appears in two paradigmatic visions on dissipative localized states. In the cubic-quintic Ginzburg Landau case, localized solutions coexist with the trivial solutions which is also stable (clearly pointed out by Fauve and Thual (PRL, 1990)). In the homoclinic snaking framework, localized states are envisioned as homoclinic connections and again, this requires stability of a background solution (not necessarily uniform) to begin with. In this paper, we observe localized states with a finite and deterministic lifetime.

The first consideration is then that those states are not stable. Still, their existence and dynamics is completely deterministic and well defined, independently of what triggered them. Thus, they qualify for an analysis in terms of "excitable" localized states. The existence of excitable localized structures has been predicted already some time ago in a model of a Kerr medium enclosed in an optical cavity. In this case, the excitable behavior resulted from the collision of the unstable localized state branch with a stable (but oscillating) localized state branch [Gomila et al, PRL 94, 063905 (2005)]. Another mechanism leading to excitable localized states (completely different in its origin) has also been analyzed theoretically in a variational model. In this case, the oscillatory regime close to which the excitable localized states are found results from the motion of the localized state. This is the kind of observations that we have realized last year in an experimental system.

The paper is on our publications page and it is about drift-induced excitable regime in a system of coupled lasers in an amplifier/absorber configuration.