Abstract

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. Much attention recently was paid to the investigation of the influence of the delayed optical feedback on the properties of these structures. In particular, it was demonstrated that in a driven passive cavity with delayed feedback a drift instability of a cavity soliton can develop leading to a motion in the transverse direction and some other instabilities [1,2]. The influence of the feedback phase and carrier relaxation rate on the drift instability threshold was investigated [3]. In this presentation we study analytically and numerically the effect of delayed optical feedback on the dynamics of cavity solitons in an active optical system: a broad area laser with a saturable absorber. Both the cases of adiabatically eliminated carrier variables and finite carrier relaxation rates are considered. We show that in the case of adiabatically eliminated carrier densities depending on the feedback phase two different scenarios of destabilization of a stationary transverse cavity solitons are observed, see Fig. 1. When the feedback phase is larger than π, the soliton is destabilized via a drift bifurcation similar to that reported earlier in a driven passive cavity with delayed feedback [2]. However, unlike the case of passive cavity the threshold value of the feedback strength is much lower and is proportional to the small diffusion coefficient describing spectral filtering in the cavity. In particular, we have demonstrated analytically that the threshold of delay induced drift instability can be considerably reduced in a laser with broad spectral bandwidth of the gain medium. In the case when the feedback phase is smaller than π, the the instability takes place via an Andronov-Hopf bifurcation leading to the undamped pulsations of the soliton transverse coordinate [4,5]. We have demonstrated the evidence of the existence of the codimension-two bifurcation point of the cavity soliton and, hence, the presence of a soliton homoclinic bifurcation in the model equations. We have developed an analytical approach to the analysis of the effect of the finite carrier relaxation rates and feedback phase on the delay induced drift and Andronov-Hopf soliton bifurcations and demonstrated the existence of snaking behavior and multistability of the soliton branch in the presence of large feedback [6]. Application of the results of our theoretical analysis to real laser systems are discussed.

© 2015 IEEE