arXiv subjects

Christophe Finot

Publications and source records attributed to Christophe Finot.

At least 19 recordsLinked to original sources

arXiv2026

Unified model for breathing solitons in fibre lasers: Mechanisms across below- and above-threshold regimes

The emergence of breathing solitons in mode-locked lasers presents a fundamental challenge for the theoretical modelling of mode locking, with the mechanisms underlying below- and above-threshold breathing solitons, and the origins of their distinct nonlinear dynamics, remaining poorly understood. Here, we develop a model that incorporates both spatial and temporal gain dynamics, enabling us to elucidate the origins of these two classes of pulsating states. We show that below-threshold breathing solitons arise from the interplay between Q-switching and soliton shaping, whereas Kerr nonlinearity and dispersion dominate the formation of above-threshold breathers. The model further captures the markedly different dynamical properties of these regimes. Experimental observations corroborate the simulations, validating the predictive power of the framework. Beyond providing a refined theoretical basis for ultrafast laser design, this work advances the broader understanding of non-equilibrium dynamics in mode-locked lasers and offers new perspectives on breathing soliton phenomena across diverse physical systems.

physics.optics↗

arXiv2025

Nonlinear dynamics in breathing-soliton lasers

We review recent advances in the study of nonlinear dynamics in mode-locked fibre lasers operating in the breathing (pulsating) soliton regime. Leveraging advanced diagnostics and control strategies -- including genetic algorithms -- we uncover a rich spectrum of dynamical behaviours, including frequency-locked breathers, fractal Farey hierarchies, Arnold tongues with anomalous features, and breather molecular complexes. We also identify a novel route to chaos via modulated subharmonic states. These findings underscore the utility of fibre lasers as model systems for exploring complex dissipative dynamics, offering new opportunities for ultrafast laser control and fundamental studies in nonlinear science.

physics.optics↗

arXiv2025

Timing-injection locking in a self-starting Mamyshev oscillator induced by the dissipative Faraday instability

Mamyshev oscillators (MOs), a novel class of passively mode-locked fiber lasers, serve as an excellent platform to explore complex nonlinear dynamics, ranging from localized structures to chaos. Despite their versatility, achieving self-starting mode-locking remains a significant challenge. In this study, we unveil the critical role of the dissipative Faraday instability (DFI) in facilitating the self-starting process of MOs, where the DFI triggers the symmetry breaking of the homogeneous solution to overcome the initiation barriers. A panoramic view of several distinct operational regimes with distinct DFI patterns is provided, namely the non-self-starting states, the irregular patterns, the harmonic mode locking regime, the stable single pulse and the stable multi pulse regime. For the lattest case, we uncover the origins of randomness in these pulse sequences through analyzing the causality between the timing of the random pulses and the initial seeding conditions. Building upon these findings, we propose the novel time-injection locking technique to customize the temporal locations of the pulses as well as the pattern timing in MOs, thus demonstrating its potential for applications in all-optical data storage and tunable ultrashort pulse sources.

physics.optics↗

arXiv2025

Langevin model for soliton molecules in ultrafast fiber ring laser cavity: investigating experimentally the interplay between noise and inertia

The dynamics of soliton molecules in ultrafast fiber ring laser cavity is strongly influenced by noise. We show how a parsimonious Langevin model can be constructed from experimental data, resulting in a mathematical description that encompasses both the deterministic and stochastic properties of the evolution of the soliton molecules. In particular, we were able to probe the response dynamics of the soliton molecule to an external kick in a sub-critical approach, namely without the need to actually disturb the systems under investigation. Moreover, the noise experienced by the dissipative solitonic system, including its distribution and correlation, can now be also analyzed in details. Our strategy can be applied to any systems where the individual motion of its constitutive particles can be traced; the case of optical solitonic-system laser presented here serving as a proof-of-principle demonstration.

physics.optics↗

arXiv2025

Unveiling the complexity of Arnold's tongues in a breathing-soliton laser

Synchronization occurs ubiquitously in nature and science. The synchronization regions generally broaden monotonically with the strength of the forcing, thereby featuring a tongue-like shape in parameter space, known as Arnold's tongue. Such a shape is universal, prevailing in many diverse synchronized systems. Interestingly, theoretical studies suggest that under strong external forcing, the shape of the synchronization regions can change substantially and even holes can appear in the solid patterns. However, experimentally accessing these abnormal regimes is quite challenging, mainly because many real-world systems displaying synchronization become fragile under strong forcing. Here, we are able to observe these intriguing regimes in a breathing-soliton laser. Two types of abnormal synchronization regions are unveiled, namely, a leaf- and a ray-like shape. High-resolution control of the loss allows holes to be revealed in the synchronization regions. Our work opens the possibility to study intriguing synchronization dynamics using a simple breathing-soliton laser as a testbed.

physics.optics↗

arXiv2024

Observation of optical chaotic solitons and modulated subharmonic route to chaos in mode-locked laser

We reveal a new scenario for the transition of solitons to chaos in a mode-locked fiber laser: the modulated subharmonic route. Its universality is confirmed in two different laser configurations, namely, a figure-of-eight and a ring laser. Numerical simulations of the laser models agree well with the experiments. The modulated subharmonic route to chaos could stimulate parallel research in many nonlinear physical systems.

physics.optics↗

arXiv2024

Automating physical intuition in nonlinear fiber optics with unsupervised dominant balance search

Identifying the underlying processes that locally dominate physical interactions is the key to understanding nonlinear dynamics. Machine-learning techniques have recently been shown to be highly promising in automating the search for dominant physics, adding important insights that complement analytical methods and empirical intuition. Here we apply a fully unsupervised approach to the search for dominant balance during nonlinear and dispersive propagation in optical fiber, and show that we can algorithmically identify dominant interactions in cases of optical wavebreaking, soliton fission, dispersive wave generation, and Raman soliton emergence. We discuss how dominant balance manifests both in the temporal and spectral domains as a function of propagation distance.

nlin.PS↗

arXiv2023

Conservation of a spectral asymmetry invariant in optical fiber four-wave mixing

The conservation of spectral asymmetry is a fundamental feature of the ideal four-wave mixing process as it exists in a medium combining quadratic chromatic dispersion and third-order nonlinearity. We test in this paper the robustness of this invariant in an experimental configuration where the excitation conditions of an optical fiber are sequentially updated, mimicking infinite propagation. This theoretical and experimental study reveals the high sensitivity of the asymmetry to very slight deviations from the ideal case, and we show that our idealized system behaves as an intermediate case between the ideal case of non-cascaded fourwave mixing and propagation in a system governed by the nonlinear Schr{\"o}dinger equation.

physics.optics↗

arXiv2023

Synchronisation, desynchronisation and intermediate regime of breathing solitons and soliton molecules in a laser cavity

We report on the experimental and numerical observations of synchronisation and desynchronisation of bound states of multiple breathing solitons (breathing soliton molecules) in an ultrafast fibre laser. In the desynchronisation regime, although the breather molecules as wholes are not synchronised to the cavity, the individual breathers within a molecule are synchronised to each other with a delay (lag synchronisation). An intermediate regime between the synchronisation and desynchronisation phases is also observed, featuring self-modulation of the synchronised state. This regime may also occur in other systems displaying synchronisation. Breathing soliton molecules in a laser cavity open new avenues for the study of nonlinear synchronisation dynamics.

physics.optics↗

arXiv2023

Control of spectral extreme events in ultrafast fibre lasers by a genetic algorithm

Extreme wave events or rogue waves (RWs) are both statistically rare and of exceptionally large amplitude. They are observed in many complex systems ranging from oceanic and optical environments to financial models and Bose-Einstein condensates. As they appear from nowhere and disappear without a trace, their emergence is unpredictable and non-repetitive, which make them particularly challenging to control. Here, we extend the use of genetic algorithms (GAs), which have been exclusively designed for searching and optimising stationary or repetitive processes in nonlinear optical systems, to the active control of extreme events in a fibre laser cavity. Feeding real-time spectral measurements into a GA controlling the electronics to optimise the cavity parameters, we are able to trigger wave events in the cavity that have the typical statistics of RWs in the frequency domain. This accurate control enables the generation of the optical RWs with a spectral peak intensity 32.8 times higher than the significant intensity threshold. A rationale is proposed and confirmed by numerical simulations of the laser model for the related frequency up- and down-shifting of the optical spectrum that are experimentally observed.

physics.optics↗

arXiv2023

Analysis of interaction dynamics and rogue wave localization in modulation instability using data-driven dominant balance

We analyze the dynamics of modulation instability in optical fiber (or any other nonlinear Schr\"{o}dinger equation system) using the machine-learning technique of data-driven dominant balance. We aim to automate the identification of which particular physical processes drive propagation in different regimes, a task usually performed using intuition and comparison with asymptotic limits. We first apply the method to interpret known analytic results describing Akhmediev breather, Kuznetsov-Ma, and Peregrine soliton (rogue wave) structures, and show how we can automatically distinguish regions of dominant nonlinear propagation from regions where nonlinearity and dispersion combine to drive the observed spatio-temporal localization. Using numerical simulations, we then apply the technique to the more complex case of noise-driven spontaneous modulation instability, and show that we can readily isolate different regimes of dominant physical interactions, even within the dynamics of chaotic propagation.

nlin.PS↗

arXiv2023

Analysis of Dispersive Fourier Transform dataset using Dynamic Mode Decomposition: evidence of multiple vibrational modes, and their interplay in a three-soliton molecule

We demonstrate that the Dynamic Mode Decomposition technique can effectively reduce the amount of noise in Dispersive Fourier Transform dataset; and allow for finer quantitative analysis of the experimental data. We therefore were able to demonstrate that the oscillation pattern of a soliton molecule actually results from the interplay of several elementary vibration modes.

physics.optics↗

arXiv2023

Predicting nonlinear reshaping of periodic signals in optical fibre with a neural network

We deploy a supervised machine-learning model based on a neural network to predict the temporal and spectral reshaping of a simple sinusoidal modulation into a pulse train having a comb structure in the frequency domain, which occurs upon nonlinear propagation in an optical fibre. Both normal and anomalous second-order dispersion regimes of the fibre are studied, and the speed of the neural network is leveraged to probe the space of input parameters for the generation of custom combs or the occurrence of significant temporal or spectral focusing.

physics.optics↗

arXiv2023

Trajectory control in idealized four-wave mixing processes in optical fiber

The four-wave mixing process is a fundamental nonlinear interaction in Kerr media that can be described by a closed trajectory in the associated phase plane. We show here that it is possible to manipulate these trajectories and to connect two points that are not part of the same orbit. Our approach is based on a localized abrupt modification of the average power of the system. This mechanism is confirmed using different experimental realizations where iterative propagation in a short fiber segments mimics propagation in an idealized optical fiber.

physics.optics↗

arXiv2022

Farey tree and devil's staircase of frequency-locked breathers in ultrafast lasers

Nonlinear systems with two competing frequencies show locking or resonances. In lasers, the two interacting frequencies can be the cavity repetition rate and a frequency externally applied to the system. Conversely, the excitation of breather oscillations in lasers naturally triggers a second characteristic frequency in the system, therefore showing competition between the cavity repetition rate and the breathing frequency. Yet, the link between breathing solitons and frequency locking is missing. Here we demonstrate frequency locking at Farey fractions of a breather laser. The winding numbers show the hierarchy of the Farey tree and the structure of a devil's staircase. Numerical simulations of a discrete laser model confirm the experimental findings. The breather laser may therefore serve as a simple model system to explore universal synchronization dynamics of nonlinear systems. The locked breathing frequencies feature high signal-to-noise ratio and can give rise to dense radio-frequency combs, which are attractive for applications.

physics.optics↗

arXiv2022

Phase space topology of four-wave mixing reconstructed by a neural network

The dynamics of ideal four-wave mixing in optical fiber is reconstructed by taking advantage of the combination of experimental measurements with supervised machine learning strategies. The training data consist of power-dependent spectral phase and amplitude recorded at the output of a short segment of fiber. The neural network is able to accurately predict the nonlinear dynamics over tens of kilometers, and to retrieve the main features of the phase space topology including multiple Fermi-Pasta-Ulam recurrence cycles and the system separatrix boundary.

physics.optics↗

arXiv2022

Ideal Four Wave Mixing Dynamics in a Nonlinear Schr{\"o}dinger Equation Fibre System

Near-ideal four wave mixing dynamics are observed in a nonlinear Schr{\"o}dinger equation system using a new experimental technique associated with iterated sequential initial conditions in optical fiber. This novel approach mitigates against unwanted sideband generation and optical loss, extending the effective propagation distance by two orders of magnitude, allowing Kerr-driven coupling dynamics to be seen over 50 km of optical fiber using only one short fiber segment of 500 m. Our experiments reveal the full dynamical phase space topology in amplitude and phase, showing characteristic features of multiple Fermi-Pasta-Ulam recurrence cycles, stationary wave existence, and the system separatrix boundary. Experiments are shown to be in excellent quantitative agreement with numerical solutions of the canonical differential equation system describing the wave evolution.

physics.optics↗

arXiv2022

Exploring Fresnel diffraction at a straight edge with a neural network

We describe a research project carried out with a group of undergraduate physics students and aimed at exploring the use of a neural network to study a classical problem in wave optics whose analytical solution is well known: the diffraction of light by the straight edge of an opaque semi-infinite screen. Through this exposure to machine learning, the students were able to appreciate the basic steps involved in a machine-learning process.

physics.ed-ph↗