Extreme events are characterized by rare and high amplitude excursions of a given variable characterizing a physical system with respect to its long time average. Its study in optics has been primarily motivated by the analogy with rogue waves in hydrodynamics and includes ingredients such as spatial instabilities, nonlinearities and noise.
Here we consider a spatially extended microcavity laser with integrated saturable absorber in the self-pulsing regime. This system, thanks to its short typical timescales, allows large recordings and accurate statistics. Moreover, it does not display irregular or aperiodic dynamics without spatial coupling. Hence, the role of spatial coupling in the emergence of extreme events can be studied. With the help of a model and of numerical analysis together with the experimental observations, we unveil the dynamical origin of the extreme events in the occurrence of spatiotemporal chaos , rather than through collisions of coherent structures. Moreover, by investigating the fine structure of the maximum Lyapunov exponent, of the Lyapunov spectrum and of the Kaplan-Yorke dimension of the chaotic attractor, we are able to deduce that intermittency plays a key role in the proportion of extreme events measured. We assign the observed mechanism of generation of extreme events to quasi-periodic extended spatiotemporal intermittency . The understanding of the formation mechanism of these extreme phenomena is an important step to devise strategies to control them.
 Selmi et al, Phy. Rev. Lett. 116, 013901 (2016).
 Coulibaly et al, Phys. Rev. A 95, 023816 (2017).
Stochastic resonance is a paradoxical phenomenon whereby a weak signal can be amplified by application of noise. Stochastic resonance occurs in a number of nonlinear systems, in neurobiology, mesoscopic physics, photonics, atomic physics, mechanics,... The classical picture of stochastic resonance involves the stochastic synchronisation of the motion of a fictious particle (representing the system's state) in a bistable potential subjected to a weak amplitude harmonic modulation (the input signal) and to amplitude noise. Stochastic amplification of the weak signal is revealed in the spectral amplification at the signal frequency for a non zero input noise strength.
We report on the observation of phase stochastic resonance in a nanomechanical, photonic crystal membrane with integrated electrical actuation. The nanomechanical oscillator is forced by a coherent driving signal which results in a bistable behavior. Bistability occurs in a bidimensional phase space since the system has a response in amplitude and in phase. We subject the oscillator to an additional slow phase modulation and to phase noise. We evidence a stochastic resonance phenomenon with amplification of the phase or amplitude response of the system for a non-zero input noise. Moreover, a theoretical analysis reveals that phase noise acts in a multiplicative fashion. This has important consequences on the optimal parameters for stochastic resonance to occur and explains the observed noise-induced detuning in the system. Phase stochastic resonance may have impact on several domains, including signal transmission telecommunication with coherent protocols such as Phase Shifting Keying, or metrology with improved detection.
Using self-induced vortex-like defects in the nematic liquid crystal layer of a light valve with photo-sensible wall, we demonstrate the realization of programable optical vortices lattices with arbitrary configuration in space. On each lattice site, every matter vortex acts as a photonic spin-to-orbital momentum coupler and an array of circularly polarized input beams is converted into an output array of vortex beams with topological charges consistent with the vortex matter lattice. The vortex arrangements are explained the basis of light-induced matter defects and topological rules.
Cavity solitons are localized light peaks in the transverse section of nonlinear resonators. These structures are usually formed under a coexistence condition between a homogeneous background of radiation and a self- organized patterns resulting from a Turing type of instabilities. In this issue, most of studies have been realized ignoring the nonlocal eﬀects. Non-local eﬀects can play an important role in the formation of cavity solitons in optics, population dynamics and plant ecology. Depending on the choice of the nonlocal interaction function, the nonlocal coupling can be strong or weak. When the nonlocal coupling is strong, the interaction between fronts is controlled by the whole non-local interaction function. Recently it has shown that this type of nonlocal coupling strongly aﬀects the dynamics of fronts connecting two homogeneous steady states and leads to the stabilization of cavity solitons with a varying size plateau. Here, we consider a ring passive cavity filled with a Kerr medium like a liquid crystal or left-handed materials and driven by a coherent injected beam. We show that cavity solitons resulting for strong front interaction are stable in one and two-dimensional setting out of any type of Turing instability. Their spatial profile is characterized by a varying size plateau. Our results can apply to large class of spatially extended systems with strong nonlocal coupling.