Rogue waves are devastating extreme events that occur in many natural systems, and a lot of work has focused on predicting and understanding their origin. In optically injected semiconductor lasers rogue waves are rare ultra-high pulses that sporadically occur in the laser chaotic output intensity. Here we show that these optical rogue waves can be predicted with long anticipation time, that they are generated by a crisis-like process, and that noise can be employed to either enhance or suppress their probability of occurrence. By providing a good understanding of the mechanisms triggering and controlling the rogue waves, our results can contribute to improve the performance of injected lasers and can also enable new experiments to test if these mechanisms are also involved in other natural systems where rogue waves have been observed. Extreme events are often catastrophic ones, such as tsunamis, earthquakes, supernovas, stock market crashes, etc. [1][2][3][4][5]. Ocean rogue waves, also referred to as freak waves, are several times the average height of surrounding waves and have steep, fast rising, and fast falling sides, like "a wall of water" [6][7][8][9]. They are a topic of intensive research as they can develop suddenly even in calm and apparently safe seas and have been responsible for several boat accidents, representing a major challenge for the design of off-shore platforms for the oil and gas industry.In optics, Solli et al.[10] have shown that extremely broadband radiation can be generated from a narrow-band input, with a long-tailed distribution similar to that of ocean rogue waves. Since then, optical rogue waves have been observed in several systems [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25], and their study has advanced the research in the field, in a way that has been compared to the introduction of optical systems to study chaos in the 1980s [26].In lasers, rogue waves occurring in the form of giant intensity pulses capable of producing catastrophic optical damage have been observed in pump-modulated [19], Raman [20], mode-locked [21][22][23], and optically injected lasers [24]. In Ref.[24] the rogue waves were studied in the framework of a simple and deterministic model that exhibits two types of chaos: one in which rogue waves do not appear consistently and one in which they are relatively frequent [24]. Since a deterministic chaotic system possesses some correlation length, the rogue waves in the system should have some degree of predictability.Here we show, experimentally and numerically, that these optical rogue waves can indeed be predicted with a long anticipation time as compared with the laser characteristic time scales. In addition, we show that an external crisis-like process [27,28], in the form of the crossing of the attractor, developed from one fixed point, with the stable manifold of another fixed point, gives rise to an expanded attractor that supports trajectories with rogue waves. We also show that noise can be exploited for either enhancing or suppressing ...

Crowd synchrony and quorum sensing arise when a large number of dynamical elements communicate with each other via a common information pool. Previous evidence in different fields, including chemistry, biology and civil engineering, has shown that this type of coupling leads to synchronization, when coupling is instantaneous and the number of coupled elements is large enough. Here we consider a situation in which the transmission of information between the system components and the coupling pool is not instantaneous. To that end, we model a system of semiconductor lasers optically coupled to a central laser with a delay. Our results show that, even though the lasers are non-identical due to their distinct optical frequencies, zero-lag synchronization arises. By changing a system parameter, we can switch between two different types of synchronization transition. The dependence of the transition with respect to the delay-coupling parameters is studied.

We present a numerical study of the pulses displayed by a semiconductor laser with optical feedback in the short-cavity regime, such that the external cavity round-trip time is shorter than the laser relaxation oscillation period. For certain parameters there are occasional pulses, which are high enough to be considered extreme events. We characterize the bifurcation scenario that gives rise to such extreme pulses and study the influence of noise. We demonstrate intermittency when the extreme pulses appear and hysteresis when the attractor that sustains these pulses is destroyed. We also show that this scenario is robust under the inclusion of noise.

We study the interplay of polarization bistability, spontaneous emission noise and aperiodic current modulation in vertical cavity surface emitting lasers (VCSELs). We demonstrate the phenomenon of logic stochastic resonance (LSR), by which the laser gives robust and reliable logic response to two logic inputs encoded in an aperiodic signal directly modulating the laser bias current. The probability of a correct response is controlled by the noise strength, and is equal to 1 in a wide region of noise strengths. LSR is associated with optimal noise-activated polarization switchings (the so-called "inter-well" dynamics if one considers the VCSEL as a bistable system described by a double-well potential) and optimal sensitivity to spontaneous emission in each polarization (the "intra-well" dynamics in the double-well potential picture). The robust nature of LSR in VCSELs offers interesting perspectives for novel applications and provides yet another example of a driven nonlinear optical system where noise can be employed constructively.

Time-delayed systems often exhibit multistability of coexisting attractors, which can result in long chaotic transients on the way to one of the coexisting states. Strong enough noise can transform this transient chaos into noise-sustained dynamics. Here we study the interplay between delay-induced multistability, chaotic transients, and noise, in the case of a semiconductor laser with optical feedback from an external reflector. The time-delayed feedback renders the laser multistable, with a set of coexisting fixed points, and induces dynamical events called low-frequency fluctuations (LFFs), consisting of sudden intensity dropouts at irregular times. The deterministic Lang-Kobayashi model shows that, for a large range of realistic laser parameters, the LFFs are just a transient dynamics toward a stable fixed point. Here we analyze the statistical properties of the transient LFF dynamics and investigate the influence of various parameters. We find that realistic values of the noise strength do not affect the average transient time or its distribution, provided the model includes an explicit delay. On the other hand, nonlinear gain saturation has a strong effect: it increases both the duration of the LFF transients and the probability of noise-induced escapes from the stable fixed point. Our results suggest that the LFFs observed experimentally can be, at least in part, sustained by the interplay of noise and various nonlinear effects, which are phenomenologically represented by a gain saturation coefficient.

Extreme and rare events are nowadays the object of intensive research. Rogue waves are extreme waves that appear suddenly in many natural systems, even in apparently calm situations. Here we study numerically the rogue wave dynamics in an optically injected semiconductor laser with external periodic forcing that is implemented via direct modulation of the laser pump current. In the region of optical injection parameters where the laser intensity is chaotic and occasional ultrahigh pulses occur, our aim is to control the system by applying a weak modulation. We find that for an adequate range of frequency and amplitude parameters, the modulation can completely suppress the extreme pulses. We also show that the interplay between modulation and an external source of noise can significantly modify their probability of occurrence. These results can motivate a range of experimental and theoretical investigations in other natural systems.

We numerically show that extreme events induced by parameter mismatches or noise in coupled oscillatory systems can be anticipated and suppressed before they actually occur. We show this in a main system unidirectionally coupled to an auxiliary system subject to a negative delayed feedback. Each system consists of two electronic oscillators coupled in a master-slave configuration. Extreme events are observed in this coupled system as large and sporadic desynchronization events. Under certain conditions, the auxiliary system can predict the dynamics of the main system. We use this to efficiently suppress the extreme events by applying a direct corrective reset to the main system.

Semiconductor lasers with continuous-wave optical injection display a rich variety of behaviors, including stable locking, periodic or chaotic oscillations, excitable pulses, etc. Within the chaotic regime it has been shown that the laser intensity can display extreme pulses, which have been identified as optical rogue waves (RWs), and it has also been shown that such extreme pulses can be completely suppressed via direct modulation of the laser current, with appropriated modulation amplitude and frequency. Here we perform a numerical analysis of the RW statistics and show that, when RWs are not suppressed by current modulation, their probability of occurrence strongly depends on the phase of the modulation. If the modulation is slow (the modulation frequency, fmod, is below the relaxation oscillation frequency, fro), the RWs occur within a well-defined interval of values of the modulation phase, i.e., there is a "safe" window of phases where no RWs occur. The most extreme RWs occur for modulation phases that are at the boundary of the safe window. When the modulation is fast (fmod > fro), there is no safe phase window; however, the RWs are likely to occur at particular values of the modulation phase. Our findings are of interest for the study of RWs in other systems, where a similar response to external forcing could be observed, and we hope that they will motivate experimental investigations to further elucidate the role of the modulation phase in the likelihood of the occurrence of RWs.