Simple guidelines to predict self-phase modulation patterns

International audience; We present a simple approach to predict the main features of optical spectra affected by self-phase modulation (SPM), which is based on regarding the spectrum modification as an interference effect. A two-wave interference model is found sufficient to describe the SPM-broadened spectra of initially transform-limited or up-chirped pulses, whereas a third wave should be included in the model for initially down-chirped pulses. Simple analytical formulae are derived, which accurately predict the positions of the outermost peaks of the spectra.

Characterisation and Mitigation of Self-Phase Modulation in Optical Fibres

International audience

Tailored waveform generation in mode-locked fiber lasers by in-cavity pulse shaper

International audience; We numerically show the possibility of pulse shaping in a mode-locked fiber laser by inclusion of an amplitude-phase spectral filter into the laser cavity. Various advanced temporal waveforms are generated, including parabolic, flat-top and triangular pulses.

Optical Nyquist pulse generation in mode-locked fibre laser

International audience

Offsetting Self-Phase Modulation in Optical Fibre by Sinusoidally Time-Varying Phase

We report on our recent experimental and theoretical results on the use of a sinusoidally time-varying phase to suppress undesirable self-phase modulation of optical pulses propagating in fibre-optic systems.

Recent machine-learning applications in ultrafast nonlinear fibre photonics

Compression spectrale dans les fibres optiques en présence de dispersion normale

National audience; Nous étudions numériquement le phénomène de compression spectrale se déroulant dans une fibre optique à dispersion normale. Les conditions conduisant à une impulsion en quasi-limite de Fourier sont déterminées et nous montrons que loin de dégrader les performances, la présence de dispersion normale permet une amélioration significative des résultats.

Dissipative Optical Breather Molecular Complexes

We demonstrate different types of breathing soliton complexes in a mode-locked fibre laser: multi-breather molecules, and molecular complexes arising from the binding of two breather-pair molecules or a breather-pair molecule and a single breather.

Frequency locking of a breather fibre laser, fairy tree and devil's staircase

Breathing solitons exhibiting periodic oscillatory behaviour form an important part of many different classes of nonlinear wave systems. Recently, thanks to the development of real-time detection techniques, they have also emerged as a ubiquitous mode-locked regime of ultrafast fibre lasers [1,2]. The excitation of breather oscillations in a laser naturally triggers a second characteristic frequency in the system, which therefore shows competition between the cavity repetition frequency and the breathing frequency. The theoretical model describing nonlinear systems with two competing frequencies predicts frequency locking, in which the system locks into a resonant periodic response featurin…

Nonlinear spectral compression in optical fiber: A new tool for processing degraded signals

International audience; We propose two new applications of the spectral focusing by self-phase modulation that occurs in a nonlinear optical fiber. We numerically show the possibility of using nonlinear spectral compression to improve the optical signal to noise ratio and mitigate the amplitude jitter of the signal pulses. We also demonstrate experimentally that use of spectral focusing in a combination with an external sinusoidal phase modulation achieves efficient suppression of coherent spectral background.

Temporal and Spectral Nonlinear Pulse Shaping Methods in Optical Fibers

The combination of the third-order optical nonlinearity with chromatic dispersion in optical fibers offers an extremely rich variety of possibilities for tailoring the temporal and spectral content of a light signal, depending on the regime of dispersion that is used. Here, we review recent progress on the use of third-order nonlinear processes in optical fibers for pulse shaping in the temporal and spectral domains. Various examples of practical significance will be discussed, spanning fields from the generation of specialized temporal waveforms to the generation of ultrashort pulses, and to stable continuum generation.

Nonlinear sculpturing of optical pulses with normally dispersive fiber-based devices

International audience; We present a general method to determine the parameters of nonlinear pulse shaping systems based on pulse propagation in a normally dispersive fiber that are required to achieve the generation of pulses with various specified temporal properties. The nonlinear shaping process is reduced to a numerical optimization problem over a three-dimensional space, where the intersections of different surfaces provide the means to quickly identify the sets of parameters of interest. We also show that the implementation of a machine-learning strategy can efficiently address the multi-parameter optimization problem being studied.

Nonlinear spectrum broadening cancellation by sinusoidal phase modulation

International audience; We propose and experimentally demonstrate a new approach to dramatically reduce the spectral broadening induced by self-phase modulation occurring in a Kerr medium. By using a temporal sinusoidal phase modulation, we efficiently cancel to a large extend the chirp induced by the nonlinear effect. Experimental validation carried out in a passive or amplifying fiber confirm the interest of the technic for the mitigation of spectral expansion of long pulses.

Parabolic similaritons in optical fibers

International audience

New fiber laser architecture with transform-limited nonlinear spectral compression

International audience; We numerically demonstrate a new fiber laser architecture supporting spectral compression of negatively chirped pulses in passive normally dispersive fiber. Such a process is beneficial for improving the energy efficiency of the cavity as it prevents narrow spectral filtering from being highly dissipative. The proposed laser design provides an elegant way of generating transform-limited picosecond pulses.

Shaping Light in Nonlinear Optical Fibers

International audience; This book is a contemporary overview of selected topics in fiber optics. It focuses on the latest research results on light wave manipulation using nonlinear optical fibers, with the aim of capturing some of the most innovative developments on this topic. The book’s scope covers both fundamentals and applications from both theoretical and experimental perspectives, with topics including linear and nonlinear effects, pulse propagation phenomena and pulse shaping, solitons and rogue waves, novel optical fibers, supercontinuum generation, polarization management, optical signal processing, fiber lasers, optical wave turbulence, light propagation in disordered fiber medi…

Farey-Fraction Frequency Locking of a Breather Ultrafast Fibre Laser

Farey Tree and Devil's Staircase of a Breather Mode-Locked Fibre Laser

Pulsating Solitons in Mode-Locked Fibre Lasers

International audience; We report on our direct experimental observation of a new regime of operation of passively mode-locked fibre lasers where the laser oscillator generates pulsating solitons with extreme ratios of maximal to minimal intensities in each period of pulsations. The soliton spectra also experience large periodic broadening and compression. Spatio-temporal intensity and dispersive Fourier-transformation measurements enable us to capture such transient dynamics in real time.

Performance optimisation of dual-pump NALM fibre laser using machine learning inference

We apply predictive regression to find optimum operating regimes in a recently proposed layout of a flexible Figure-8 laser having two independently pumped segments of active fibre in its bidirectional ring.

Self-Optimising Breather Ultrafast Fibre Laser

We demonstrate the self-optimisation of the breather regime in an ultrafast fibre laser through an evolutionary algorithm. Depending on the specified merit function, single breathers with controllable breathing ratio and period, and breather molecular complexes with a controllable number of constituents can be obtained.

Simple model of self-phase modulation spectral patterns in optical fibres

Self-phase modulation (SPM) has been extensively studied for several decades in optical fibers. This phenomenon manifests itself by a change of the frequency spectrum of a pulse, owing to the nonlinear index variation that follows the temporal evolution of the pulse. In the general case, the spectrum of the transmitted pulse cannot be calculated analytically and only approximate or rms expressions giving the bandwidth of the transmitted spectrum are used. In this paper, we present a novel theoretical treatment of SPM based on a spectral interference model. We show that a two-wave interference process is sufficient to describe the main features of the SPM-broadened spectra of initially Fouri…

Control of complex nonlinear wave dynamics in dissipative systems by machine learning

Ultrafast mode-locked fibre lasers exploiting nonlinearity in the pulse formation process are well-known to display a rich landscape of "dissipative soliton'' dynamics, which results from the interplay of the nonlinearity with dispersion and dissipation. Reaching a desired operating regime in a fibre laser generally depends on precisely adjusting multiple parameters in a high-dimensional space, in connection with the wide range of accessible pulse dynamics, which is usually performed through a trial-and-error experimental procedure, due to the lack of analytic relationship between the cavity parameters and the pulse features. The practical difficulties associated with such a procedure can b…

Nonlinear spectral shaping and optical rogue events in fiber-based systems

International audience; We provide an overview of our recent work on the shaping and stability of optical continua in the long pulse regime. Fibers with normal group-velocity dispersion at all-wavelengths are shown to allow for highly coherent continua that can be nonlinearly shaped using appropriate initial conditions. In contrast, supercontinua generated in the anomalous dispersion regime are shown to exhibit large fluctuations in the temporal and spectral domains that can be controlled using a carefully chosen seed. A particular example of this is the first experimental observation of the Peregrine soliton which constitutes a prototype of optical rogue-waves.

Enhanced nonlinear spectral compression in fibre by external sinusoidal phase modulation

International audience; We propose a new, simple approach to enhance the spectral compression process arising from nonlinear pulse propagation in an optical fibre. We numerically show that an additional sinusoidal temporal phase modulation of the pulse enables efficient reduction of the intensity level of the side lobes in the spectrum that are produced by the mismatch between the initial linear negative chirp of the pulse and the self-phase modulation-induced nonlinear positive chirp. Remarkable increase of both the extent of spectrum narrowing and the quality of the compressed spectrum is afforded by the proposed approach across a wide range of experimentally accessible parameters.

Machine learning approach for nonlinear pulse shaping in optical fibres

We use a supervised machine-learning approach to solve both the direct and inverse problems relating to the nonlinear shaping of optical pulses in optical fibres.

Temporal and spectral nonlinear pulse shaping in normally dispersive optical fibers

The combination of the third-order optical nonlinearity with chromatic dispersion in optical fibers offers an extremely rich variety of possibilities for tailoring the temporal and spectral content of a light signal, depending on the regime of dispersion that is used. Because the nonlinear dynamics of pulses propagating in fibers with normal group-velocity dispersion is generally sensitive to the initial pulse condition, it is possible to nonlinearly shape the propagating pulses through control of the initial pulse temporal intensity and/or phase profile. Here, we review recent progress on the use of third-order nonlinear processes in normally dispersive fibers for pulse shaping in the temp…

Nonlinear Sculpturing of Optical Pulses in Fibre Systems

The interplay among the effects of dispersion, nonlinearity and gain/loss in optical fibre systems can be efficiently used to shape the pulses and manipulate and control the light dynamics and, hence, lead to different pulse-shaping regimes [1,2]. However, achieving a precise waveform with various prescribed characteristics is a complex issue that requires careful choice of the initial pulse conditions and system parameters. The general problem of optimisation towards a target operational regime in a complex multi-parameter space can be intelligently addressed by implementing machine-learning strategies. In this paper, we discuss a novel approach to the characterisation and optimisation of …

Breather Molecular Complexes in a Passively Mode‐Locked Fiber Laser

International audience; Breathing solitons are nonlinear waves in which the energy concentrates in a localized and oscillatory fashion. Similarly to stationary solitons, breathers in dissipative systems can form stable bound states displaying molecule-like dynamics, which are frequently called breather molecules. So far, the experimental observation of optical breather molecules and the real-time detection of their dynamics are limited to diatomic molecules, that is, bound states of only two breathers. In this work, the observation of different types of breather complexes in a mode-locked fiber laser: multibreather molecules, and molecular complexes originating from the binding of two breat…

Pulse Generation and Shaping Using Fiber Nonlinearities

Nonlinear pulse shaping in normally dispersive fibers : experimental examples

International audience; While the combination of Kerr nonlinearity with dispersion in optical fibers can seriously impair high speed optical transmissions, it also provides an attractive solution to generate new temporal and spectral waveforms. We explain in this talk how to take advantage of the progressive temporal and spectral reshapings that occur upon propagation in a normally dispersive fiber. We base our discussion on several experimental results obtained at telecommunication wavelengths.

Modelling Nonlinear Propagation of Periodic Waveforms in Optical Fibre with a Neural Network

We deploy a neural network to predict the spectro-temporal evolution of a periodic waveform upon nonlinear fibre propagation and demonstrate efficient probing of the input-parameter space for on-demand comb generation or significant spectral/temporal focusing occurrence.

Pulse transition to similaritons in normally dispersive fibre amplifiers

selected by the editors of Journal of Optics as a Highlight of 2013a video linked to the experiments can be seen at : http://youtu.be/thbXaW91D5g; International audience; A detailed experimental characterization of the transition process of an initially Gaussian pulse to the asymptotic self-similar parabolic solution in optical fibre amplifiers operating in the normal dispersion regime is performed.

Impact of amplitude jitter and signal-to-noise ratio on the nonlinear spectral compression in optical fibres

International audience; We numerically study the effects of amplitude fluctuations and signal-to-noise ratio degradation of the seed pulses on the spectral compression process arising from nonlinear propagation in an optical fibre. The unveiled quite good stability of the process against these pulse degradation factors is assessed in the context of optical regeneration of intensity-modulated signals, by combining nonlinear spectral compression with centered bandpass optical filtering. The results show that the proposed nonlinear processing scheme indeed achieves mitigation of the signal's amplitude noise. However, in the presence of a jitter of the temporal duration of the pulses, the perfo…

Optical waveform tailoring in passive and laser cavity fibre systems

International audience; The interplay among the effects of dispersion, nonlinearity and gain/loss in optical fibres is a powerful tool to generate a broad range of pulse shapes with tuneable properties. Here we propose a method to optimise the systems parameters for a given pulse target. By reducing the system complexity and applying machine-learning strategies, we show that it is possible to efficiently identify the sets of parameters of interest. Two configurations are numerically investigated: pulse shaping in a passive normally dispersive fibre and pulse generation in a dual-pump nonlinear-amplifying-loop-mirror mode-locked fibre laser.

Impact of a temporal sinusoidal phase modulation on the optical spectrum

International audience; We discuss the effects of imparting a temporal sinusoidal phase modulation to a continuous wave on the frequency spectrum. While a practical analytical solution to this problem already exists, we present here a physical interpretation based on interference processes. This simple model will help the students better understand the origin of the oscillatory structure that can be observed in the resulting spectrum and that is characteristic of Bessel functions of the first kind. We illustrate our approach with an example from the field of optics.

Self-phase modulation in optical fibres

International audience

Nonlinear spectral compression in fibre as a power-limiting device

Spectral compression (SC) by self-phase modulation in optical fibre has been known for a long time and has since been reported for various parameters [1]. In this paper, we analyse the impact of amplitude fluctuations and a degraded optical signal-to-noise ratio (OSNR) of the seed pulses on the SC process by means of extensive nonlinear Schrodinger equation numerical simulation. Remarkably, our results show that the SC is rather stable against these pulse degradation factors, thereby revealing its potential for use in the context of optical regeneration of intensity-modulated signals. We therefore propose an optical scheme combining SC with an optical bandpass filter (OBPF) centred at the c…

Machine learning for ultrafast nonlinear photonics

Recent years have seen the rapid growth of the field of smart photonics where the deployment of machine-learning strategies is the key to enhance the performance and expand the functionality of optical systems. Here, we review our recent results obtained in collaboration with the University of Aston (S. Boscolo) and the University of Franche-Comté (J.M. Dudley) by providing several examples of advances enabled by machine-learning tools such as neural networks (NNs).We describe the use of a supervised feedforward NN paradigm to solve the direct and inverse problems relating to nonlinear pulse shaping in optical fibres, bypassing the need for direct numerical solution of the governing propaga…

Propagation non-linéaire dans les fibres optiques par réseaux de neurones artificiels

National audience; Nous mettons en œuvre différents réseaux de neurones artificiels pour prédire l’évolution des profils temporels et spectraux d’intensité après propagation dans une fibre optique en présence de non-linéarité forte. Le problème inverse est également considéré.

Effects of fourth-order fiber dispersion on ultrashort parabolic optical pulses in the normal dispersion regime

International audience; We propose a new method for the generation of both triangular-shaped optical pulses and flat-top, coherent supercontinuum spectra using the effect of fourth-order dispersion on parabolic pulses in a passive, normally dispersive highly nonlinear fiber. The pulse re-shaping process is described qualitatively and is compared to numerical simulations.

Auto-setting breather mode-locked fibre laser

International audience

Amplifier similariton fiber laser with nonlinear spectral compression

International audience; We propose a new concept of a fiber laser architecture supporting self-similar pulse evolution in the amplifier and nonlinear spectral pulse compression in the passive fiber. The latter process allows for transform-limited picosecond pulse generation, and improves the laser's power efficiency by preventing strong spectral filtering from being highly dissipative. Aside from laser technology, the proposed scheme opens new possibilities for studying nonlinear dynamical processes. As an example, we demonstrate a clear period-doubling route to chaos in such nonlinear laser system.

Artificial neural networks for nonlinear pulse shaping in optical fibers

International audience; We use a supervised machine-learning model based on a neural network to predict the temporal and spectral intensity profiles of the pulses that form upon nonlinear propagation in optical fibers with both normal and anomalous second-order dispersion. We also show that the model is able to retrieve the parameters of the nonlinear propagation from the pulses observed at the output of the fiber. Various initial pulse shapes as well as initially chirped pulses are investigated.

Transition dynamics in optical fiber amplifiers operating in the normal dispersion regime

Over the past decade there has been large interest in ultrafast optical fiber amplifiers operating in the normal dispersion regime because of the discovery that, high-energy pulses with a parabolic intensity profile and linear frequency chirp are the asymptotic solution to the system for arbitrary initial conditions [1]. These so-called “similariton” solutions propagate in a self-similar manner, holding certain relations (scaling) between pulse power, duration, and chirp parameter. While the asymptotic similariton features seem now well understood [1], the physics of the transition to this solution from arbitrary initial pulses has not been fully explored yet (most of the previous attempts …

Enhanced nonlinear spectral compression in fibre by sinusoidal phase modulation

International audience

Pulse shaping in mode-locked fiber lasers by in-cavity spectral filter

International audience; We numerically show the possibility of pulse shaping in a passively mode-locked fiber laser by inclusion of a spectral filter into the laser cavity. Depending on the amplitude transfer function of the filter, we are able to achieve various regimes of advanced temporal waveform generation, including ones featuring bright and dark parabolic-, flat-top-, triangular- and saw-tooth-profiled pulses. The results demonstrate the strong potential of an in-cavity spectral pulse shaper for controlling the dynamics of mode-locked fiber lasers.

Temporal and spectral nonlinear shaping techniques in optical fibers

International audience

New developments in the study of optical parabolic pulses in normally dispersive fibers

International audience; We report two recent studies dealing with the evolution of parabolic pulses in normally dispersive fibers. On the one hand, the nonlinear reshaping from a Gaussian intensity profile towards the asymptotic parabolic shape is experimentally investigated in a Raman amplifier. On the other hand, the significant impact of the fourth order dispersion on a passive propagation is theoretically discussed: we numerically demonstrate flat-top, coherent supercontinuum generation in an all-normal dispersion-flattened photonic crystal fiber. This shape is associated to a strong reshaping of the temporal profile what becomes triangular.

Breather Dynamics in Ultrafast Fibre Lasers and Their Intelligent Control

We review our recent work on the dynamics of breathing solitons in fibre lasers, including single breathers, breather molecular complexes, breather explosions and breather frequency locking at Farey fractions, and their control by genetic algorithms.

Performance analysis of dual-pump nonlinear amplifying loop mirror mode-locked all-fibre laser

We numerically characterise, in the three-dimensional space of adjustable cavity parameters, the performance of a recently reported layout of a flexible figure-8 laser having two independently pumped segments of active fibre in its bidirectional ring (Smirnov et al 2017 Opt. Lett. 42 1732–5). We show that this optimisation problem can be efficiently addressed by applying a regression model based on a neural-network algorithm.

Farey Tree and Devil’s Staircase of a Breather Mode-Locked Fibre Laser

We demonstrate frequency locking at Farey fractions of breathing solitons in an ultrafast fibre laser. The ratios of the breathing frequency to the cavity-repetition frequency display the devil staircase’s structure with a 0.906 fractal dimension.

Self-phase modulation patterns in optical fibres

International audience; Self-phase modulation (SPM), one of those very fascinating effects discovered in the early days of nonlinear optics, refers to the phenomenon by which an intense optical beam propagating in a Kerr medium (e.g., an optical fibre) induces through the nonlinearity of the medium a modulation of its phase that is proportional to its own intensity profile [1]. For an input pulsed beam, the induced time-dependent phase change is associated with a modification of the optical spectrum, which depends on the initial frequency modulation (chirp) of the pulse electric field. If the pulse is initially Fourier-transform-limited or up-chirped, SPM leads to spectral broadening, where…

Breathing Solitons in a Passively Harmonic Mode-Locked Fibre Laser

We report on the first experimental observation of breathing solitons in a passively harmonic mode-locked fibre laser. Various features of a 4th-harmonic operation state showing breather oscillations with a period of 5 roundtrips are discussed.

In-Cavity Transformations for New Nonlinear Regimes of Pulse Generation in Mode-Locked Fibre Lasers

International audience; We review recent progress in the research on nonlinear mechanisms of pulse generation in passively mode-locked fibre lasers. These include parabolic self-similar pulse mode-locking, a mode-locking regime featuring pulses with a triangular distribution of the intensity, and spectral compression arising from nonlinear pulse propagation. We also report on the possibility of achieving various regimes of advanced temporal waveform generation in a mode-locked fibre laser by inclusion of a spectral filter into the laser cavity.

Breather laser dynamics and their intelligent control

Breathers are localized structures showing periodic variations in parameters. They are found in various fields of science, and are currently attracting significant research interest in virtue of their relationship with a rich set of important nonlinear phenomena. They have recently emerged as a universal ultrashort pulse regime in passively mode-locked fibre lasers. Here, we reviewed our recent works in this fast-growing field, including the first observation of breathing dissipative solitons and their complexes in mode-locked fibre lasers[1-3], breather explosions[4], and intelligent control of breathers over breathing periods, breathing ratios, and the number of breathers[5]. Finally, fra…

Multi-parameter optimisation of dual-pump NALM fibre laser using machine-learning approaches

Recently, a new design of a model-locked all-fibre Figure-8 laser employing a nonlinear amplifying loop mirror (NALM) with two active fibre segments and two independently controlled pump-power modules has been proposed and experimentally demonstrated. This laser layout combines the reliability and robustness of conventional Figure-8 lasers with the flexibility of nonlinear-polarisation-evolution (NPE) lasers, providing access to a variety of generation regimes with a relatively wide adjustment range of the pulse parameters. Moreover, it enables reliable and reproducible live electronic adjustment of the lasing regimes, which is practically impossible to do by adjusting fibre-based polarisat…

Impact of initial pulse shape on the nonlinear spectral compression in optical fibre

International audience; We theoretically study the effects of the temporal intensity profile of the initial pulse on the nonlinear spectral compression process arising from nonlinear propagation in an optical fibre. Various linearly chirped input pulse profiles are considered, and their dynamics is explained with the aid of time-frequency representations. While initially parabolic-shaped pulses show enhanced spectral compression compared to Gaussian pulses, no significant spectral narrowing occurs when initially super-Gaussian pulses are used. Triangular pulses lead to a spectral interference phenomenon similar to the Fresnel bi-prism experiment.

Mitigation of self-phase modulation by sinusoidally time varying phase

The propagation of intense ultra-short optical pulses in a Kerr medium such as an optical fibre remains a critical issue for many optical systems. This is because the self-phase modulation (SPM) of the propagating pulse usually causes a severe broadening of the pulse spectrum that is typically accompanied by an oscillatory structure. Several strategies have been proposed and successfully deployed to counteract the deleterious effects of SPM in fiber-optic systems, including spatial or temporal scaling to reduce the impact of nonlinearity. Other approaches rely on the exploitation of the peculiar properties of parabolic shaped pulses and self-similar evolution. However, none of these last te…

Elimination de l’auto-modulation de phase dans un amplificateur à fibre

National audience; Nous introduisons et démontrons expérimentalement une nouvelle approche pour améliorer le taux d’extinction d’une impulsion affectée par un fond continu cohérent. Cette méthode repose sur une modulation temporelle par une phase sinusoïdale suivie d’une étape de recompression spectrale non-linéaire.

Design rules for nonlinear spectral compression in optical fibers

International audience; We present comprehensive design rules to optimize the process of spectral compression arising from nonlinear pulse propagation in an optical fiber. Extensive numerical simulations are used to predict the performance characteristics of the process as well as to identify the optimal operational conditions within the space of system parameters. It is shown that the group-velocity dispersion of the fiber is not detrimental and, in fact, helps achieve optimum compression. We also demonstrate that near-transform-limited rectangular and parabolic pulses can be generated in the region of optimum compression.

Parabolic similaritons in optical fibres

International audience; Recent developments in nonlinear optics have brought to the fore of intensive research an interesting class of pulses with a parabolic intensity prole and a linear instantaneous frequency shift or chirp [1, 2]. Parabolic pulses propagate in optical bres with normal group-velocity dispersion in a self-similar manner, holding certain relations (scaling) between pulse power, duration and chirp parameter, and can tolerate strong nonlinearity without distortion or wave breaking. These solutions, which have been dubbed similaritons, were demonstrated theoretically and experimentally in ber ampliers in 2000. Similaritons in ber ampliers are, along with solitons in passive b…

Nonlinear pulse shaping and polarization dynamics in mode-locked fiber lasers

International audience; We review our recent progress on the study of new nonlinear mechanisms of pulse shaping in passively mode-locked fiber lasers. These include a mode-locking regime featuring pulses with a triangular distribution of the intensity, and spectral compression arising from nonlinear pulse propagation. We also report on our recent experimental studies unveiling new types of vector solitons with processing states of polarization for multi-pulse and tightly bound-state soliton (soliton molecule) operations in a carbon nanotube (CNT) mode-locked fiber laser with anomalous dispersion cavity.

Amplifier similariton fibre laser with nonlinear spectral compression

We propose and numerically demonstrate a new concept of fibre laser architecture supporting self-similar pulse evolution in the amplifier and nonlinear pulse spectral compression in the passive fibre. The latter process is beneficial for improving the power efficiency as it prevents strong spectral filtering from being highly dissipative.

Nonlinear Pulse Shaping in Optical Fibres with a Neural Network

We use a supervised machine-learning model based on a neural network to solve the direct and inverse problems relating to the shaping of optical pulses that occurs upon nonlinear propagation in optical fibres.

Model-free modelling of nonlinear pulse shaping in optical fibres

International audience; Machine learning is transforming the scientific landscape, with the use of advanced algorithmic tools in data analysis yielding new insights into many areas of fundamental and applied science. Photonics is no exception, and machine-learning methods have been applied in a variety of ways to optimise and analyse the output of optical fibre systems. In parallel with these developments, pulse shaping based on nonlinear propagation effects in optical fibres has developed into a remarkable tool to tailor the spectral and temporal content of light signals, leading to the generation of a large variety of optical waveforms. Yet, due to the typically large number of degrees of fre…

Propagation non linéaire dans des fibres optiques par réseaux de neurones artificiels

National audience; Les techniques d’apprentissage machine transforment le paysage de la recherche traditionnelle avec l’utilisation d’outils algorithmiques avancés pour l’analyse de données massives offrant de nouveaux angles de vue. Les domaines de la photonique et de l’optique ultra-rapide n’échappent pas à cette révolution. Nous nous intéressons dans cette contribution à la mise en œuvre de telles techniques appliquées à la mise en forme non-linéaire d’impulsions se propageant dans une fibre optique en présence de non-linéarités optiques. En effet, la combinaison de la dispersion et de la non-linéarité au cours de la propagation modifie profondément les profils temporels et spectraux de …

Spectral compression by self-phase modulation

International audience

Machine learning for ultrafast nonlinear photonics

Optical besselon waves

International audience; We theoretically describe a new type of an optical waveform, the ‘besselon’, which is synthesised by the line-by-line application of π/2-spectral phase shifts to sinusoidally phase-modulated continuous-wave light.

Accrochage de fréquence dans un laser à fibre à respiration : observation de l’arbre de Farey et de l’escalier du diable

Contrairement au soliton brillant, les solitons à respiration présentent un comportement oscillatoire périodique. L’utilisation des fibres optiques a grandement facilité leur observation: l’interaction sur une grande distance entre la non-linéarité Kerr et la dispersion, en la quasi-absence de dissipation a ainsi permis la caractérisation fine des solitons à respiration d’Akhmediev, de Ma ou bien encore de leur cas limite, le soliton de Peregrine.Grâce au développement des techniques de détection en temps réel, les cavités laser à fibre offrent une autre plateforme extrêmement intéressante. Dans le contexte des lasers ultrarapides à modes bloqués, la génération d’impulsions à respiration co…

Compression spectrale améliorée par une modulation de phase corrective sinusoïdale

National audience; En exploitant une modulation de phase sinusoïdale temporelle additionnelle, nous montrons qu’il est possible d’améliorer significativement les performances d’une compression spectrale réalisée en régime de propagation hautement non-linéaire. Les simulations numériques indiquent ainsi une amélioration des facteurs de compression ainsi que du rapport de Strehl.

Nonlinear pulse sculpturing in passive and laser cavity fibre systems

International audience; In recent years, there has been a growing interest from the photonics community in the generation of non-conventional optical waveforms because of their applications in all-optical signal processing and microwave signal manipulation. While sinusoidal, Gaussian and hyperbolic secant intensity profiles are now routinely produced by modulators or mode-locked lasers, other signal waveforms such as parabolic, triangular or flat-top pulse shapes remain rather hard to synthesize. Several approaches to the generation of specialized waveforms have been explored, including linear spectral shaping, the use of special Mach-Zehnder modulator architectures, and coherent Fourier sy…

Façonnage optique intra-cavité dans un laser impulsionnel à fibre

National audience