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The study of temporal solitons has revolutionized fiber optics, yielded new classes of ultrafast laser and opened multiple interdisciplinary applications.

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 constitue un mode de fonctionnement alternatif [1,2] au cas bien répandu où une impulsion aux propriétés toujours identiques est émise à chaque tour de cavité. L’excitation des solutions à respiration déclenche donc spontanément l’émergence d’une seconde fréquence caractéristique dans le système. Cette deuxième fréquence sera plus faible que la fréquence associée à la cavité, i.e. la fréquence de répétition. Or les systèmes non linéaires à deux fréquences concurrentes peuvent conduire à un verrouillage de fréquence, conduisant à une réponse périodique résonante avec un rapport de fréquence rationnel [3].Bien que les phénomènes de verrouillage de fréquence aient fait l’objet d’études théoriques et expérimentales approfondies dans de nombreux systèmes physiques, y compris les lasers à semi-conducteurs dans le domaine de l’optique, les recherches menées jusqu’à présent concernent essentiellement des systèmes dans lesquels une modulation externe, contrôlable avec précision, ajoute une nouvelle fréquence caractéristique au système. Le cas d’une seconde fréquence émergeant naturellement a par contre été très peu discuté. Cela s’explique en grande partie par la difficulté expérimentale d’atteindre de manière précise ces régimes à respiration. Pour simplifier cette tache laborieuse, nous avons mis en place une approche d’apprentissage automatique basée sur l’utilisation d’un algorithme évolutionnaire pour l’optimisation de la fonction de transfert non linéaire intra-cavité [4]. Nous démontrons alors qu’un laser à fibre verrouillé par un mode de respiration est un système montrant un verrouillage de fréquence [5]. Ces états sont caractérisés par une robustesse à la variation des paramètres (puissance de pompage et polarisation) et un rapport signal/bruit nettement amélioré. Ils se produisent dans l’ordre où ils apparaissent dans l’arbre de Farey et dans un intervalle de puissance de pompagedonné par la largeur de la marche correspondante dans l’escalier du diable.[1] J. Peng, S. Boscolo, Z. Zhao, H. Zeng, Sci. Adv. 5 (2019), eaax1110.[2] J. Peng et al., Laser Photon. Rev. 15 (2021), 2000132.[3] M.H. Jensen, P. Bak, T. Bohr, Phys. Rev. Lett . 50 (1983), 1637.[4] X. Wu et al., Laser Photon. Rev. 16 (2), 2100191[5] X. Wu et al., Nat. Commun. 13 (1), 5784

L’équation de Schrödinger non linéaire régit l’évolution des ondes dans de nombreux domaines non linéaires tels que l’hydrodynamique, la physique des plasmas, les condensats de Bose-Einstein et l’optique fibrée. Dans ce dernier cas, l’onde subit des changements dans un milieu dispersif combiné à un déphasage non linéaire dépendant de l’intensité. Le processus clé sous-jacent est le mélange à quatre ondes, qui décrit l’échange d’énergie entre des composantes de fréquence discrètes. En raison de la croissance des bandes latérales additionnelles et des pertes optiques qui limitent la distance d’interaction potentielle, il est notoirement difficile d’observer expérimentalement la dynamique idéale de mélange à quatre ondes. Afin de résoudre ce problème, nous proposons de modifier itérativement les conditions de phase et d’amplitude d’un signal composé de trois raies spectrales également espacées qui est ensuite injecté dans un court segment de fibre optique [1]. Une telle approche segmentée nous permet d’imiter une propagation idéalisée sur des dizaines de kilomètres - une distance qui dépasse largement la fibre de 500 m utilisée. Notre étude expérimentale révèle la topologie complète de l’espace de phase présentant plusieurs cycles de récurrence de Fermi-Pasta-Ulam-Tsingou, l’existence d’une onde stationnaire ainsi que la présence d’une séparatrice qui marque la transition entre deux régimes d’évolution spatio-temporelle distincts [2]. Lorsqu’elle est tracée sur un portrait de phase, la dynamique des ondes suit des orbites proches qui sont définies de manière unique par les conditions initiales, et qui ne se croisent pas. En changeant brusquement au cours de la propagation les paramètres de contrôle, tels que la puissance moyenne, nous démontrons à la fois théoriquement et expérimentalement qu’il est possible de connecter deux états qui ne sont pas initialement situés sur la même trajectoire fermée [3]. Enfin, nous étudions également les avantages des techniques d’apprentissage automatique supervisées de deux manières différentes. Tout d’abord, nous combinons des mesures non itérées avec un réseau neuronal [4]. Les résultats démontrent que le réseau peut extraire les caractéristiques clés de la topologie de l’espace des phases et peut prévoir avec précision la dynamique non linéaire. Deuxièmement, nous avons mis en œuvre les techniques d’identification clairsemée de la dynamique non linéaire. À partir d’un ensemble de plusieurs trajectoires pouvant être potentiellement affectées par le bruit, nous sommes en mesure de récupérer quantitativement les termes directeurs dans les systèmes d’équations différentielles [5].[1]A. Sheveleva et al., Optica 9, 656-662, 2022.[2]G. Cappellini and S. Trillo, J. Opt. Soc. Am. B 8, 824-838, 1991.[3]A. Sheveleva et al. Optics Communications, in press, 2023, arXiv:2303.08469.[4]A. Sheveleva et al., Opt. Lett. 47, 6317-6320, 2022.[5]A. V. Ermolaev et al., Sci Rep, 12, 12711, 2022.

We describe the vibration pattern of a soliton-molecule using the Langevin’s model, i.e. noise source combined with a deterministic model. This simpler model allows investigating the interplay between fl uctuation and dissipation mechanisms at play.

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.

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.

The noise-like pulse regime of optical fiber lasers is highly complex, and associated with multiscale emission of random sub-picosecond pulses underneath a much longer envelope. With the addition of highly nonlinear fiber in the cavity, noise-like pulse lasers can also exhibit supercontinuum broadening and the generation of output spectra spanning 100’s of nm. Achieving these broadest bandwidths, however, requires careful optimization of the nonlinear polarization rotation based saturable absorber, which involves a very large potential parameter space. Here we study the spectral characteristics of a broadband noise-like pulse laser by scanning the laser operation over a random sample of 50,000 polarization settings, and we quantify that these broadest bandwidths are generated in only $$\sim$$ ∼ 0.5% of cases. We also show that a genetic algorithm can replace trial and error optimization to align the cavity for these broadband operating states.

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., Comment: 18 pages, 4 figures

We propose an experimental technique aimed to reveal a fundamental four-wave mixing process resulting in a complete reconstruction of the phase-space topology. The analysis is accompanied by training of a neural network on the experimental data.

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 featuring a rational frequency ratio, and quasi-periodicity following the hierarchy of the Farey tree and the structure of the devil’s staircase [3]. Whilst frequency-locking phenomena have been extensively studied theoretically and experimentally in many physical systems including semiconductor lasers in the field of optics, all the investigations so far relate to systems where an external, accurately controllable modulation adds a new characteristic frequency to the system. Conversely, the link between breathers and frequency locking in fibre lasers is largely missing, arguably because tuning the breathing frequency is a laborious task when done manually, requiring precise control of multiple laser parameters. Here we circumvent this difficulty by a machine-learning approach based on the use of an evolutionary algorithm for the optimisation of the intra-cavity nonlinear transfer function steered by electronically driven polarisation control [4], and we demonstrate that a breather mode-locked fibre laser is a passive system showing frequency locking at Farey fractions [5]. The frequency-locked states, characterised by robustness against parameter (pump power and polarisation) variation and a high signal-to-noise ratio of the breathing frequency, occur in the sequence they appear in the Farey tree and within a pump-power interval given by the width of the corresponding step in the devil’s staircase. The breather laser may therefore serve as a simple model system to explore universal synchronisation dynamics of nonlinear systems. Furthermore, frequency-locked breather lasers can generate wide radiofrequency combs with a line spacing that is not constrained by the length of the laser cavity and can reach the sub-megahertz range, thus representing an attractive alternative to long, unstable fibre cavities for many applications such as in high-resolution spectroscopy. [1] J. Peng, S. Boscolo, Z. Zhao, H. Zeng, Sci. Adv. 5 (2019), eaax1110.[2] J. Peng, Z. Zhao, S. Boscolo, C. Finot, S. Sugavanam, D.V. Churkin, H. Zeng, Laser Photon. Rev. 15 (2021), 2000132.[3] M.H. Jensen, P. Bak, T. Bohr, Phys. Rev. Lett. 50 (1983), 1637.[4] X. Wu, J. Peng, S. Boscolo, Y. Zhang, C. Finot, H. Zeng, Laser Photon. Rev. 1

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.

We experimentally demonstrate an optical fiber testbed enabling the quantitative study of ideal four-wave mixing. We directly measure the complex phase-space topology including features such as the separatrix, Fermi Pasta Ulam recurrence, and stationary waves.

Les couleurs nous entourent et sont indispensables à notre existence. Elles peuvent tirer leur origine et leurs propriétés de mécanismes très différents : le pigment de peinture a physiquement peu de points communs avec les processus à l’œuvre dans la formation d’un arc en ciel. Pour mieux comprendre ces différents aspects, nous reviendrons sur ce qu’est la lumière ainsi que les différentes sources de lumières désormais disponibles. Nous évoquerons également les couleurs « invisibles » pour l’œil mais qui sont néanmoins exploitées dans de nombreuses applications modernes.

We describe the use of a neural network to investigate a very well-known problem of wave optics, i.e. the diffraction of an opaque semi-infinite screen. The inverse problem is also discussed.

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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.

We use the machine learning technique of spars eregression to “reverseengineer” dynamical data to discover the underlying physical model of four wave mixing in nonlinear fibre optics.

Near-ideal four wave mixing dynamics are observed in a nonlinear Schr{��}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.

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International audience; The study of the combination of Kerr nonlinearity with dispersion in optical fibers has been stimulating much interest since the 80s. If such a combination can seriously impair the quality of high speed optical transmissions, it can on the contrary become 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. We base our discussion on several experimental results obtained in the last decade at the Laboratoire Interdisciplinaire Carnot de Bourgogne. Examples exploiting both the normal and anomalous regimes of dispersion will be analyzed in the theoretical context of the nonlinear Schrödinger equation. In order to provide a rapid but pedagogical overview of the vast possibilities of nonlinear shaping in optical fibers, we will more precisely describe the following experiments carried out at telecommunication wavelengths :-The generation of parabolic and triangular temporal waveforms in normally dispersive fibers.- The generaton of high-quality ultrashort pulses in the regime of anomalous dispersion.- The generation of optical rogue events

International audience

International audience

National audience; Nous décrivons ici un projet visant à explorer avec un groupe d'étudiants en physique de niveau licence l'utilisation d'un réseau neuronal pour simuler un problème traditionnel de l'optique ondulatoire, i.e. la diffraction d'un bord d'écran dont la solution analytique est connue. Par cette première approche de l'intelligence artificielle, nous avons pu mettre l'accent sur les étapes essentielles nécessaires pour mettre en oeuvre ces nouvelles technologies numériques. Mots clés : diffraction de Fresnel ; apprentissage par réseau neuronal.

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.

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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 freedom involved, optimising nonlinear pulse shaping for application purposes may require extensive numerical simulations based on the integration of the nonlinear Schr¨odinger equation (NLSE) or its extensions. This is computationally demanding and potentially creates a severe bottleneck in using numerical techniques to design and optimise experiments in real time. Here, we present a solution to this problem using a supervised machine-learning model based on a feedforward neural network (NN) to solve both the direct and inverse problems relating to pulse shaping, bypassing the need for numerical solution of the governing propagation model. Specifically, we show how the network accurately predicts the temporal and spectral intensity profiles of the pulses that form upon nonlinear propagation in fibres with both anomalous and normal dispersion. Further, we demonstrate the ability of the NN to determine the nonlinear propagation properties from the pulses observed at the fibre output, and to classify the output pulses according to the initial pulse shape. We also expand our analysis to the case of pulse propagation in the presence of distributed gain or loss, with a special focus on the generation of self-similar parabolic pulses [6]. The results show that the network is able to accommodate to and maintain high accuracy for a wide dynamic range of system parameters. Although demonstrated here in a fibre optics context, the principle of using NN architectures to solve wave equation-based inverse problems is expected to apply to many physical systems.

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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.

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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 breather-pair molecules or a breather pair molecule and a single breather is reported. The intermolecular temporal separation of the molecular complexes attains several hundreds of picoseconds, which is more than an order of magnitude larger than that of their stationary soliton counterparts and is a signature of long-range interactions. Numerical simulations of the laser model support the experimental findings. Moreover, nonequilibrium dynamics of breathing solitons are also observed, including breather collisions and annihilation. This work opens the possibility of studying the dynamics of many-body systems in which breathers are the elementary constituents.

International audience; Dispersive shock waves are a universal phenomenon encountered in many fields of science, ranging from fluid dynamics, Bose-Einstein condensates and geophysics. It has been established that light behaves as a perfect fluid when propagating in an optical medium exhibiting a weakly self-defocusing nonlinearity. Consequently, this analogy has become attractive for the exploration of dispersive shock wave phenomena. Here, we observe of a novel class of vectorial dispersive shock waves in nonlinear fiber optics. Analogous to blast-waves, identified in inviscid perfect fluids, vectorial dispersive shock waves are triggered by a non-uniform double piston imprinted on a continuous-wave probe via nonlinear cross-phase modulation, produced by an orthogonally-polarized pump pulse. The nonlinear phase potential imparted on the probe results in the formation of an expanding zone of zero intensity surrounded by two repulsive oscillating fronts, which move away from each other with opposite velocities.

International audience; We analyse the temporal properties of the optical pulse wave that is obtained by applying a set of spectral /2 phase shifts to continuous-wave light that is phase-modulated by a temporal sinusoidal wave. We develop an analytical model to describe this new optical waveform that we name 'besselon'. We also discuss the reduction of sidelobes in the wave intensity profile by means of an additional spectral  phase shift, and show that the resulting pulses can be efficiently time-interleaved. The various predicted properties of the besselon are confirmed by experiments demonstrating the generation of low-duty cycle, high-quality pulses at repetition rates up to 28 GHz.

National audience; L’optique ondulatoire est souvent enseignée à travers ses manifestations dans le domaine spatial : motifs d’interférence, figures de diffraction, propagation en espace libre... En exploitant le domaine de Fourier, il est possible de dresser une analogie formelle entre la diffraction 1D de la lumière et la dispersion subie par impulsion ultrabrève. Cela a permis la transposition de solutions connues de l’optique spatiale à l’optique temporelle. Ainsi, régie par une phase quadratique, la lentille temporelle copie la lentille traditionnelle et a permis ainsi d’imaginer expérimentalement de nouvelles approches de caractérisation d’impulsions ultrabrèves.Dans cette contribution, nous présenterons d’autres configurations où cette analogie peut être mise à profit en se basant sur l’utilisation de fibres optiques. Ainsi, à partir de modèles simples, nous discuterons d’interféromètres temporels de Fresnel ou de Billet [1], d’un analogue temporel à la tâche d’Arago [2], de lentilles temporelles lenticulaires [3] ou bien encore de réseaux temporels dispersifs [4]. Ces différents exemples seront illustrés par différentes expériences menées dans un laboratoire de télécommunications optiques.[1] F. Chaussard, H. Rigneault, and C. Finot, Opt. Commun. 397, 31-38 (2017).[2] C. Finot and H. Rigneault, ArXiv:1902.06138 [3] J. Nuno, C. Finot, and J. Fatome, Opt. Fiber Technol. 36, 125-129 (2017).[4] C. Finot and H. Rigneault, J. Opt. Soc. Am. B 34, 1511-1517 (2017).

National audience; Des ondes très variées sont régies par l’équation de Schrödinger non-linéaire : la lumière dans les fibres optiques, les vagues océaniques, les ondes dans les plasmas, les condensats de Bose-Einstein… Quand la non-linéarité compense la dispersion, un soliton peut se propager tout en maintenant ses caractéristiques temporelles et spectrales inchangées. En présence d’une onde continue, une autre onde non-linéaire existe : le soliton Peregrine (PS), prédit dès 1983 [1] mais démontré expérimentalement seulement en 2010 [2]. Au contraire du soliton usuel, le PS apparait de nulle part, concentre temporellement et spatialement son énergie, puis disparait sans laisser de trace.Les expériences en optique [2] ou hydrodynamique [3] ont confirmé l’évolution de son profil temporel et spectral d’amplitude. Nous complétons ici ces études en nous intéressant expérimentalement plus précisément à la phase. Nous confirmons ainsi l’existence de sauts caractéristiques [4]. L’universalité du PS est également soulignée par son émergence lors de l’évolution non-linéaire d’impulsions diverses. Nous détaillerons ainsi la propagation d’impulsions super-gaussiennes marquées par l’apparition dans leurs flancs de PS [5].[1] H. Peregrine, J. Austral. Math. Soc. Ser. B 25, 16-43 (1983)[2] B. Kibler et al, Nature Physics 6, 790-795 (2010)[3] A. Chabchoub et al, Phys. Rev. Lett. 106, 204502 (2011)[4] G. Xu et al, Phys. Rev. E 99, 012207 (2019)[5] F. Audo et al, Opt. Lett. 43, 2864-2867 (2018)

National audience; Nous introduisons théoriquement et démontrons expérimentalement une nouvelle approche à même de générer des trains impulsionnels de grande qualité et à haut-débit. Cette méthode repose sur une modulation temporelle par une phase sinusoïdale suivie de l’application d’une phase spectrale triangulaire.

International audience; We report the development of titanium dioxide-based waveguides for applications in the near-and mid-infrared. Thanks to embedded metal grating couplers, we demonstrate error free 10 Gbit/s optical transmissions at 1.55 and 2 µm. We also demonstrate octave-spanning supercontinuum in cm-long waveguides. We explore the way to improve such waveguides through optimized fabrication process.

International audience; Optical supercontinua are a fundamental topic that has stimulated a tremendous practical interest since the early works of Alfano et al. in the 70’s in bulk components. Photonic crystal fibers have then brought some remarkable potentialities in tailoring the dispersive properties of a waveguide while maintaining a high level of confinement over significant propagation distances. The next breakthrough is to further reduce the footprint of the nonlinear component and to achieve the generation of optical supercontinuum on a photonic chip. To reach this aim, several platforms have been successfully investigated such as silicon, silicon germanium, silicon nitride, chalcogenide waveguides to cite a few. Each material has obviously specific advantages but also limitations including strong two photon absorption and the associated free carrier absorption, low refractive index, low handling power, etc…We discuss here the design and fabrication a new component made on an alternative platform that remains relatively unexplored: titanium dioxide (TiO2). This material benefits from a transparency window spanning from the visible to the mid-infrared wavelengths. It combines a high linear and nonlinear refractive index with negligible TPA beyond 800 nm. Therefore, recent experimental studies have confirmed these features and reported the spectral broadening of a femtosecond pulse [1], the parametric wavelength conversion of a continuous wave [2] as well as the efficient generation of third harmonic [3].Our goal is to demonstrate the generation of an octave spanning supercontinuum in a TiO2 waveguide [4]. We consider here anatase TiO2 layers with a thickness of 450 nm. Pumping the component in the slightly anomalous dispersion regime is a major requirement and it therefore dictates the width of our waveguide. The dispersion profile of the fundamental TE mode obtained in a 1.5 µm wide waveguide is presented as well as structure that has been achieved. The input pulses are provided by a 1560 nm femtosecond laser source that is frequency shifted up to 1640 nm In order to optimize the light injection through butt-coupling, two 1-mm long tapers have been included in the TiO2 device. After propagation in the 2.2-cm long waveguide with subwavelength transverse dimensions, an octave-spanning supercontinuum is generated from 1050 nm up to 1900 nm, which represents an improvement by much more than one order of magnitude compared to [1]. The spectral extend of the supercontinuum is ruled by the location of the two zero dispersion wavelengths and we can note the emergence of a strong dispersive wave below 1200 nm. The observed dynamics can be reproduced by numerical integration of the generalized nonlinear Schrödinger equation. The third harmonic is also generated so that visible light is also clearly observed by the naked eye [3].