Eric Louvergneaux

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PhD - Master - Postdoc

 

 

Research activities

 

Current research fields

Dissipative solitons and localized structures

Opticall rogue waves

Convective-absolute instabilities and Noise-sustained structures in optical systems

Effects of noise on spatiotemporal dynamics

Modulational instabilities in passive optical fibre resonators

Pattern formation in nematic liquid crystals with optical feedback

 

Other research fields

Transverse mode competition in a CO2 laser

Dynamics of a diode laser subject to weak phase-conjugate feedback from a rubidium vapour cell

 

 

 

Current research fields

Optical rogue waves

 

We study pattern formation in an optical system composed of a Kerr medium subjected to optical feedback but in a regime very far from the modulational instability threshold. In this highly nonlinear regime, the dynamics is turbulent and the associated one-dimensional patterns depict rare and intense localized optical peaks. We analyse numerically and experimentally the statistics and features of these intense optical peaks and show that their probability density functions (PDF) have a long tail indicating the occurrence of rogue events

10.01.22.20h07m52_5.6400_0_0_013_2Dyn

 

Dissipative solitons and localized structures

 

23mai2008g_8_recadre

 

Convective-absolute instabilities and Noise-sustained structures in optical systems

 

In a liquid crystals feedback system: Translational transverse shifts drastically affect pattern formation in a noisy system with optical feedback. These strong nonlocal interactions may give rise to large domains of convective instability resulting in various types of two-dimensional 2D noise-sustained structures. These “basic patterns” are investigated and their thresholds and properties are analytically derived. Corresponding 2D experimental patterns are shown to be in complete agreement with theory. Surprisingly enough, some patterns that are purely sustained by noise are found to be nondrifting in contrast with the commonly widespread situation in which convective instabilities lead to travelling patterns.

2D NSS

 

beta3

In a fibre ring cavity: We theoretically and experimentally evidence that fibre systems are convective systems since their nonlocal inherent properties, such as the dispersion and Raman effects, break the reflection symmetry. Theoretical analysis and numerical simulations carried out for a fibre ring cavity demonstrate that the third-order dispersion term leads to the appearance of convective and absolute instabilities. Their signature is an asymmetry in the output power spectrum. Using this criterion, experimental evidence of convective instabilities is given in a fibre cavity pumped by a pulsed laser.

 

Effects of noise on spatiotemporal dynamics

 

Noisy spatial bifurcation: A universal behaviour for the generic bifurcations of one-dimensional systems in the presence of additive noise is studied. In particular, an analytical expression for the supercritical bifurcation shape of transverse one-dimensional 1D is given. From this universal expression, the shape of the bifurcation, its location, and its evolution with the noise level are completely defined. Experimental results obtained for a 1D transverse Kerr-type slice subjected to optical feedback are in excellent agreement

NoiseBifSemII

 

Modulational instabilities in passive optical fibre resonators

 

 

Control and removal of modulational instabilities in low-dispersion photonic crystal fibre cavities: Taking up to fourth-order dispersion effects into account, we show that fibre resonators become stable for a large intensity regime. The range of pump intensities leading to modulational instability becomes finite and controllable. Moreover, by computing analytically the thresholds and frequencies of these instabilities, we demonstrate the existence of a new unstable frequency at the primary threshold. This frequency exists for an arbitrary small but nonzero fourth-order dispersion coefficient. Numerical simulations for a low and flattened dispersion photonic crystal fibre resonator confirm analytical predictions and open the way to experimental implementation.

 

Pattern formation in nematic liquid crystals with optical feedback

 

Pattern-Dislocation-Type Dynamical Instability in 1D Optical Feedback Kerr Media with Gaussian Transverse Pumping:
We study experimentally and numerically the secondary instability corresponding to the destabilization of stationary transverse roll patterns appearing in a 1D liquid crystal layer subjected to optical feedback. This dynamical instability appears as roll dislocations in the spatiotemporal diagrams. We show that it originates from the Gaussian spatial transverse dependence of a control parameter and that its corresponding mechanism is the selection of a local unstable wave number. This instability is the optical counterpart of the ramp-induced Eckhaus instability observed in hydrodynamics.

image008

 

10bk01b

Other research fields

Transverse mode competition in a CO2 laser

 

During my PhD, I studied the transverse mode competition occurring in large aspect ratio CO2 lasers with self-imaging cavity configuration. Both stable and unstable cavity configurations were explored close to the frequency degeneracy of all the transverse modes

THESE CO2

 

Dynamics of a diode laser subject to weak phase-conjugate feedback from a rubidium vapour cell

 

During my postdoctoral position at the Vrije Universiteit of Amsterdam in the theoretical group of professor D. Lenstra, I was involved in experiments on a phase conjugate mirror based on a rubidium vapour cell. The aim was to achieve the study of the dynamical behaviour of a diode laser subjected to phase-conjugate feedback (IEEE J. Quantum Electron. 35).

 

10bk01b

 

 

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