Delay induced instabilities of cavity solitons in passive and active laser systems

Summary form only given. Cavity solitons are localized spots of light in the transverse section of passive and active optical devices: broad area lasers and semiconductor cavities with external coherent pumping. Under certain conditions a drift instability can appear in these devices leading to a transverse motion of cavity solitons. Such motion in distributed dynamical systems of different nature can be induced by various effects, e.g., walk-off, convection, phase gradient, vorticity, finite carrier relaxation times, the so-called Ising-Bloch transition, symmetry breaking due to off-axis feedback or resonator detuning. Recently it was shown within the framework of the Swift-Hohenberg equation [1] that a drift instability leading to a spontaneous motion of localized structures in arbitrary direction can be induced by a delayed feedback term. More recently the appearance of nontrivial instabilities resulting in the formation of oscillons, soliton rings, labyrinth patterns, or moving structures was demonstrated in this system [2].First, we study the effect of delayed feedback on the mobility properties of transverse cavity solitons in a broad area semiconductor microcavity. We present analytical and numerical analysis of the dependence of the drift instability threshold and on the feedback strength, feedback phase, and carrier relaxation time. In particular we demonstrate that due to finite carrier relaxation rate the delay induced drift instability can be suppressed to a certain extent. We give analytical estimation of the soliton velocity near the drift instability point which is in a good agreement with numerical results obtained using the full model equations. Next, the effect of delayed optical feedback on the dynamics of cavity solitons in a broad area semiconductor laser with a saturable absorber is investigated theoretically. It is shown analytically that the threshold of delay induced drift instability can be considerably reduced in a laser with broad spectr- l bandwidth of the gain medium. Furthermore, it is demonstrated that depending on the feedback phase it is possible not only to destabilize cavity solitons via the delay induced drift instability but also to suppress another drift instability [3] related to the finite relaxation rates of the gain and absorber sections.