Le sujet de cette thèse se rapporte à la génération d’impulsions ultracourtes dans une cavité laser fibrée à travers l’optimisation automatique de ses paramètres par un algorithme d’évolution. L’intérêt pour cette problématique provient de la difficulté à explorer les dynamiques impulsionnelles de manière systématique dans un large domaine de paramètres expérimentaux. Nous avons montré que l’implémentation d’un algorithme d’évolution sur une cavité laser fibrée de ce type peut être réalisée, en prenant les précautions adéquates pour que cette association soit la plus efficace possible. Nous avons démontré expérimentalement pour la première fois le verrouillage de modes depuis la seule optimisation des contrôleurs de polarisation utilisant une procédure automatique d’auto-apprentissage. Nous avons démontré que la sélection du blocage de modes depuis son spectre radio-fréquence permet de sélectionner le taux de répétition desimpulsions à l’intérieur de la cavité. Ces résultats préliminaires démontrent les potentialités de notre méthode employée dans des situations de dynamique non linéaire ultrarapide de grande complexité, particulièrement sensibles aux paramètres. / This thesis deals with the generation of ultrashort pulses within a fiber laser cavity through the automatic optimization of its parameters by an evolutionary algorithm. The interest of this subject comes from the difficulty to systematically explore dynamics in a large domain of experimental parameters. We have shown that it is possible to implement an evolutionary algorithm on fiber laser cavity with appropriate precautions. We have experimentally demonstrated for the first time the mode locking of a laser cavity only using the optimization of polarization controllers through an automatic and self-learning procedure. We also have demonstrated that selecting the mode locking from it radio-frequency spectrum allow to select the pulses repetition rate within the cavity. These preliminary results show the promising aspect of our method used in situations of non linear ultrafast dynamics with high complexity which are particularly sensitive to parameters.

Made available in DSpace on 2016-03-15T19:37:45Z (GMT). No. of bitstreams: 1 Heidi Kaori Sato Pertile.pdf: 2322047 bytes, checksum: aaee9a054b94e9557394faaf3251bec9 (MD5) Previous issue date: 2013-01-24 / In this work we present a study on the generation of pulse train in an Erbium doped fiber laser in the hybrid mode-locking regime operating with short pulses at high repetition rates. The short pulses are generated by passive mode-locking technique using carbon nanotubes as saturable absorbers. High repetition rates are generated by active mode-locking technique using a phase modulator. We built cavities with three different mode-locking regimes: active, passive and, finally, hybrid, to compare results. In active and hybrid cavities we used an electro-optical modulator. In passive and hybrid cavities we used a homemade film of a polymer containing carbon nanotubes with diameter of 1 nm. With the cavity operating in the hybrid regime we obtained pulse durations of 1.77 ps with repetition rate of 10 GHz. / Neste trabalho apresentamos um estudo sobre a geração de trem de pulsos em laser à fibra dopada com Érbio operando em regime de acoplamento híbrido de modos, com pulsos curtos a altas taxas de repetição. Os pulsos curtos são obtidos pela técnica de acoplamento passivo de modos utilizando absorvedores saturáveis de carbono. As altas taxas de repetição são obtidas pela técnica de acoplamento ativo de modos através de um modulador. Construímos três cavidades distintas: ativa, passiva e finalmente a híbrida para comparação de resultados. Nas cavidades ativa e híbrida foi utilizado um modulador eletro-óptico de fase e, nas cavidades passiva e híbrida foi utilizado um filme de um polímero (NOA 73TM) contendo nanotubos de carbono com diâmetro de 1 nm por nós fabricado. Com a cavidade em regime híbrido de modos, foi obtida uma duração de pulso de 1,77 ps com uma taxa de repetição de 10 GHz.

Made available in DSpace on 2016-03-15T19:38:49Z (GMT). No. of bitstreams: 1 2012_Lucia Akemi Miyazato Saito.pdf: 7872621 bytes, checksum: 4898bb89f5642047c4e878b18fc4f31a (MD5) Previous issue date: 2012-11-01 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / We investigated the mechanisms responsible for pulse formation and evolution in Erbium-doped fiber lasers with cavity lengths varying from 16.4 m to 100.8 km that were actively mode-locked at repetition rate of 1 GHz. The variation of pulse widths and the peak powers in these lasers defined three regimes of propagation inside the cavities and we identified the mechanisms responsible for the pulse formation and evolution in each one of these regimes depending on the ratio between the cavity length (Lcav) and the dispersion length (LD) and nonlinear length (LNL). When Lcav is shorter than LD and LNL, there is neither dispersive nor nonlinear effect during pulse evolution (pulse has a duration of approximately 30 ps). In this regime, its final duration is determined by the standard theory of active modelocking. For Lcav shorter than LD but ~ LNL, the pulse evolution is in the nonlinearity-dominant regime where the self-phase modulation leads to spectral broadening. In addition, for cavities longer than 12.6 km, Lcav ~ LD and also longer then LNL. The pulse evolution is in the dispersion-dominant regime with its duration depending on the accumulated dispersion. In this regime the soliton effect takes place and the final pulse duration depends on the cavity length. Also, we present a comparison between an in-field and in-laboratory 50 km ultralong Erbium fiber lasers actively mode-locked with repetition rate varying from 1 to 10 GHz generating pulses from 35.2 to 68.7 ps. The pulse widths generated at higher frequencies are in agreement with Kuizenga-Siegman theory. However, for lower frequencies the pulses have higher intracavity peak power which allows the soliton effect to take place. Depending on the pump power level, the repetition rate and the cavity length, both lasers can operate in active mode-locking or under the influence of the soliton regime that locks the pulse duration according to the dispersion and cavity length. Due to the soliton robustness, this condition eliminates most of the environmental influence in the in-field mode-locking regime and makes both lasers very similar. / O laser de fibra dopada com Érbio é apresentado nesta tese numa nova configuração: cavidade ultralonga, com dimensão da ordem de dezenas de quilômetros. Foram investigados os mecanismos responsáveis pela formação e evolução do pulso em cavidades com comprimentos de 16,4 m a 100,8 km operando em regime de acoplamento de modos ativo na taxa de repetição de 1 GHz. A variação da largura dos pulsos e da potência de pico nestes lasers definem três regimes de propagação no interior das cavidades sendo possível identificar os mecanismos responsáveis pela formação e evolução em cada um destes regimes, dependendo da relação entre o comprimento da cavidade (Lcav) e o comprimento de dispersão (LD) e também em relação ao comprimento não-linear (LNL). Quando Lcav é menor que LD e LNL, não há efeito dispersivo e não-linearidades apreciáveis na evolução do pulso, obtendo-se aproximadamente 30 ps. Neste regime, a duração final é determinada pela teoria de acoplamento de modos ativo. Para Lcav menor que LD mas ~LNL, a evolução do pulso é dominado pela não-linearidade onde a automodulação de fase resulta em alargamento espectral. Além disso, para cavidades mais longas que 12,6 km, Lcav ~ LD e Lcav mais longo que LNL, a duração do pulso na saída aumenta proporcionalmente com a dispersão acumulada e ocorre a propagação de pulsos sob efeito solitônico. Complementando o estudo, o laser na configuração em laboratório é comparado com o laser montado em campo, sendo utilizado em ambos 50 km de fibra padrão. O laser à fibra dopada com Érbio é modulado ativamente com taxa de repetição variando entre 1 e 10 GHz gerando pulsos de 35,2 a 68,7 ps. A duração dos pulsos gerados em frequências altas está de acordo com a teoria de Kuizenga-Siegman. No entanto, em baixas frequências os pulsos têm potência de pico intracavidade alta o que permite que haja a formação de pulsos solitônicos na propagação. Dependendo do nível da potência de bombeamento, da taxa de repetição e do comprimento da cavidade, os dois lasers podem operar em acoplamento de modos ativo ou sob a influência do regime solitônico que trava a duração do pulso de acordo com a dispersão e comprimento da cavidade. Devido à robustez do sóliton, esta condição elimina a maior parte da influência do ambiente no acoplamento de modos do laser na configuração em campo, tornando os dois lasers muito similares.

Made available in DSpace on 2016-03-15T19:38:55Z (GMT). No. of bitstreams: 1 CLAUDIA BARROS DOS SANTOS DEMORI.pdf: 3640553 bytes, checksum: 13700107293ec12ced27c0e70d6fb334 (MD5) Previous issue date: 2015-08-25 / This work shows an Erbium doped-fiber Laser with many frequencies and many operation regimes based on integration of two paired arrayed waveguide gratings (AWGs) into a ring cavity. The AWGs are highlighted, since 2000, as key technology for multifrequencies lasers for optical communications, spectroscopy, image, astronomy and others applications. Fundamentally, gratings work splitting waveguide signal and since insertion in the cavity they allow simultaneous operating of tens of wavelength. We explore each one of these wavelength withing Erbium gain region, doing channels in different regimes of operation. These regimes may be continuous or pulsed. The advantage is that each channel may be modulated independently. Simultaneous operation with high repetition rates at 10 and 40 GHz were demonstrated, as continuous wave. The laser is stable, versatile and multifunctional. It is possible that more operating regimes, as passive mode-locking, be explored. We showed by this work efficient way to passive mode-locking by carbon nanotubes as saturable absorbers. Soon, the passive mode-locking is a potential regime for the demonstrated laser. As the new bi-dimensional materials, that look efficient for passive mode-locking and in the future, hybrid mode-locking, as graphene and black phosphor. / Esta tese trata de demonstrar um Laser de fibra dopada com Érbio com múltiplas frequências e múltiplos regimes de operação simultâneos baseados na integração de duas grades de difração pareadas (Arrayed Waveguide Gratings, AWGs) dentro de uma cavidade de laser de fibra. As AWGs são apontadas, desde o ano 2000, como tecnologia fundamental em lasers de múltiplas frequencias para as comunicações ópticas, para espectroscopia, imageamento, astronomia, e outras aplicações. Fundamentalmente, as grades funcionam como divisores do sinal óptico e quando inseridas dentro da cavidade de um laser de fibra permitem a operação simultânea de dezenas de comprimentos de onda. Neste trabalho, exploramos cada comprimento de onda, dentro da região de ganho do Érbio, com um regime de operação diferente. Esse regime pode ser pulsado ou contínuo. A vantagem do laser apresentado é que cada comprimento de onda é um canal que pode ser modulado de forma independente. Pôde-se demonstrar operação simultânea com regimes a altas taxas de repetição como 10 GHz e 40 GHz, assim como CW. O laser é estável, versátil e multifuncional. É possível que mais regimes de operação, como o regime de acoplamento de modos passivo sejam explorados. Mostramos ao longo deste trabalho maneiras eficientes de acoplar modos passivamente, utilizando nanotubos de carbono como absorvedores saturáveis, logo a técnica de acoplamento de modos passivo é um dos regimes em potencial para este laser. Assim como, o uso de novos materiais bidimensionais, que se mostram eficientes para o acoplamento de modos passivo e futuramente híbrido, como o grafeno e o fósforo negro.

Les gaz quantiques dégénérés des atomes neutres sont d’excellentssystèmes avec les applications importantes dans les études de la physique à plusieurs corps, de la matière condensée, de la mesure de haute précision et de l'information quantique. Dans cette thèse, nous démontrons la production des condensats de Bose-Einstein de 87Rb dans les différents modes transverses de la cavité qui a une configuration en papillon (bow-tie cavity). La cavité est résonante à deux longueurs d'onde, 1560 nm et 780 nm. Nous utilisons la radiation à 1560 nm, une longueur d'onde accessible dans la télécommunication (bande C) pour obtenir le condensat de Bose-Einstein dans un piège dipolaire intra-cavité. La cavité optique permet de réaliser un piège dipolaire profond à partir d'une source optique à puissance modérée (3W), grâce à l'amplification de la puissance au sein du résonateur. Les modes non dégénérés du résonateur permettent d'obtenir de multiples condensats dans les modes transverses supérieurs. Comme exemples représentatifs, nous avons réalisé le condensat de Bose-Einstein dans le mode fondamental et le mode TEM01 de la cavité. L'utilisation de ces modes nous permet d'avoir un et deux puits de potentiels pour le piégeage où l'échantillon atomique ultra-froid est couplé au mode du résonateur. En contrôlant la puissance relative entre le mode fondamental et les modes transverses supérieurs (TEM01, TEM10), nous arrivons à réaliser la division et la recombinaison d’un 'ensemble atomique ultra-froid. De plus, dans ce manuscrit nous présentons le développementd'un système d'asservissement autour de la cavité optique qui nous permet d'obtenir les deux radiations asservies sur le résonateur ainsi que la stabilisation de la longueur de la cavité sur les atomes de rubidium. La deuxième longueur d'onde provient du faisceau à 1560 nm après le doublage de fréquence. Par la suite, les deux longueurs d'onde sont asservies sur la cavité par la technique de Pound-Drever-Hall. Une partie du composant doublé en fréquence est comparée en fréquence avec un laser à 780 nm asservi sur les atomes de rubidium par la technique de battement optique. Ensuite, le signal de battement est converti par un synthétiseur de fréquence et est envoyé vers le contrôleur de transducteur piézo-électrique de la cavité via un régulateur PI pour éviter la dérive à long terme liée aux fluctuations de la température. La résonance à 780 nm sera utilisée comme faisceau de sonde intra-cavité. Cela nous permettra de réaliser une mesure quantique non-destructive et de générer des états comprimés de spins induits par cette mesure / Quantum degenerate gases of neutral atoms are excellent systems with important applications in the study of many body quantum physics, condensed matter physics, precision measurements, and quantum information processing. In this thesis we demonstrate the creation of 87Rb Bose-Einstein condensates (BECs) in different transverse modes of a bow-tie cavity. The cavity resonant at two wavelengths, 1560 and 780 nm. We are using the radiation 1560 nm accessible in telecom (C band) to create BEC in the cavity enhanced optical dipole trap with only 3 W of optical power from the source. The non-degenerate cavity modes enable the creation of arrays of BECs in the higher transverse modes. As representative examples we realize the BEC in the fundamental TEM00 and the TEM01 mode of the cavity which are the single well and double well trapping configuration with ultra-cold atomic simple well coupled to the cavity modes. By controlling the relative power between the fundamental and the higher transverses cavity modes (TEM01, TEM10), splitting and merging of ultra-cold atomic ensemble is shown. Moreover, in this manuscript we present the development of a lock system around the optical cavity which allows us to obtain both radiations locked to the cavity as well as the lengthe of the optical resonator is referenced on the rubidium atoms. The second wavelength is derived from 1560 nm beam by frequency doubling and then both radiations are locked to the cavity by Pound-Drever-Hall technique. One part of the frequency doubled 780 nm is referenced to an independent 780 nm laser locked on the rubidium atoms. The beat signal between these two lasers is frequency synthesized and through the PI controller is sent to the piezo-electric transducer driver to avoid long-term drifts of the cavity due to temperature fluctuations. The cavity resonance at 780 nm will be used as a probe beam for cavity aided quantum non-demolition measurements to generate measurement induced spin squeezed states.

Ce travail concerne le développement d’une fibre optique à structure originale permettant la montée en puissance moyenne et crête dans les systèmes lasers à 2μm. La gestion des effets thermiques est devenue aujourd’hui un enjeu primordial notamment pour essayer de repousser le seuil d’apparition des instabilités modales transverses. Le principe mis en avant ici est basé sur la rupture de symétrie de la gaine microstructurée de la fibre afin d’améliorer la délocalisation des modes d’ordre supérieur vers l’extérieur du milieu à gain. Ainsi une propagation quasi-monomode est obtenue dans une fibre apériodique passive avec un coeur de 140μm à 2μm. Un travail de modélisation a été mené de manière à proposer d’autres structures basées sur une modulation contrôlée de l’indice de réfraction dans le milieu à gain afin de repousser encore plus le seuil du régime multimode. En outre, la fabrication de la première fibre dopée thulium à large aire modale (Dcoeur = 18μm) par la méthode REPUSIL a montré une efficacité de 50%. Ensuite, la fabrication de la première fibre rigide complètement apériodique à gaine réduite dopée thulium a été réalisée. Une fibre avec un coeur de 29μm et un diamètre extérieur de 769μm et une longueur de 86cm a été caractérisée en configuration laser et a permis d’obtenir une émission laser à 2μm de 3,8W (puissance limitée par la puissance de la diode de pompe disponible) avec un rendement de 20% et une qualité de faisceau quasi-monomode. De plus, une fibre passive complètement apériodique à polarisation unique avec un coeur de 140μm a également été réalisée et a permis d’obtenir un ratio d’extinction de polarisation de 16,5dB à 2μm. / This work deals with the development of an original leaky structure of optical fiber aiming at generating a high power laser radiation at 2μm in CW and pulsed regimes. The management of thermal effects in high power/energy regime became a major issue, in particular to push further the transverse modal instabilities threshold. Our approach consists in breaking the symmetry of the microstructured fiber cladding for to improve the delocalization of the high order modes outside of the gain medium. Thus, an effective single-mode propagation at a 2μm operating wavelength was first demonstrated into a passive aperiodic fibers whose the core diameter reaches up to 140 μm. After implementing some Stress Applying Parts over our aperiodic design, a PER of 16.5dB was achieved at 2μm using a single polarization passive FA-LPF with a core of 140 μm. Thence, a numerical study on the tailoring the active core refractive index has been carried out so as to fend off the threshold of multimodedness. Additionally, the first LMA Tm-doped fiber (Dcoeur = 18μm) fabricated by the REPUSIL method and showing an efficiency of 50% is demonstrated. Thereafter, the fabrication of the first rod-type Tm-doped FA-LPF with reduced cladding is shown. A 29 μm core FA-LPF was characterized in laser configuration, leading to an effective single-mode emission of 3.8W of average power at 2μm strictly restricted by the available pump power and an efficiency of 20%.

Cette thèse concerne l'étude de la dynamique des structures optiques dissipatives observées dans une cavité à gestion de dispersion utilisant l'évolution non linéaire de la polarisation comme technique de blocage de modes. Nous avons montré expérimentalement l'existence d'une transition graduelle entre le régime de fonctionnement continu et le régime de fonctionnement multi-impulsionnel. Nous nous sommes intéressés à l'état intermédiaire où il nous a été possible d'obtenir divers régimes inédits et d'étudier ainsi le comportement collectif des solitons dissipatifs en présence d'un fond continu. La dynamique de "la pluie de solitons" est une manifestation complexe et fascinante constituée de trois composantes de champ : le fond continu, les solitons de dérive et la phase condensée. Elle s'accompagne d'une circulation d'énergie à travers ces trois composantes. Le mouvement relatif des solitons de dérive ainsi que l'asymétrie temporelle présentent les caractéristiques majeures qui distinguent cette dynamique des autres. D'autres types d'auto-organisation ont été observés et étudiés, comme "le relargage des solitons de la phase condensée" ou bien encore "la vobulation du train de solitons". Nous nous sommes intéressés aussi à la propagation d'une seule impulsion dans la cavité. Pour la première fois, une importante dynamique de respiration spectrale a été prédite dans une cavité à gestion de la dispersion. Nous avons montré qu'une compression temporelle de l'impulsion est accompagnée d'un élargissement spectral d'une grande ampleur dans la partie passive de la cavité et que la largeur de l'impulsion peut dépasser la largeur de la bande passante du milieu amplificateur. Nous avons étudié la dynamique de la respiration spectrale, l'extraction et l'optimisation du signal laser en fonction des paramètres de la cavité et nous avons présenté les caractéristiques d'une cavité qui permet la génération d'une impulsion dont sa largeur spectrale est supérieure à la largeur de la bande passante de l'amplificateur d'un facteur de 2.4. Les dynamiques présentées dans cette thèse témoignent de la complexité et de la richesse de la dynamique dissipative des lasers à fibre fonctionnant en régime de blocage de modes passif par évolution non linéaire de la polarisation. / This thesis presents a study of the nonlinear dissipative dynamics of localized of self organized structures in passively mode-locked fiber laser through nonlinear polarization evolution. We reveal the existence of a gradual transition from the quasi-cw to mode locked dynamics in the multi-pulsing regime. We emphasize on the intermediate state, where various new dynamics are observed. We study collective behaviors of dissipative solitons in the presence of a continuous background. One of the complex and attractive dynamics presented is the "soliton rain", which composed of three field components : continuous modes of background, drifting of solitons and condensed phase solitons. This dynamic appears when the energy flows through the three components. The relative motion of the drifting solitons and the temporal asymmetry present the major characteristics that distinguish this dynamic. Other types of self-organizations of solitons were observed and studied as the "release of the solitons from the condensed phase" and the "chirped trains with condensed soliton phase". We were also interested in the single pulse propagation. For the first time, an important dynamics of spectral breathing was predicted in a dispersion-managed cavity. We showed that pulse compression dynamics in the passive anomalous fiber can be accompanied by a significant enhancement of the spectral width and that the width of the pulse can exceed the amplifier bandwidth. We studied, the extraction and the optimization of the signal laser according to the parameters of the cavity and we presented the characteristics of a cavity delivering ultra short pulses with a spectral width exceeding the amplifier bandwidth by a factor of 2.4. The dynamics presented in this thesis show the complexity and variety of the dissipative dispersion-managed dynamics in fiber laser mode locked through nonlinear polarization evolution.

This study deals with unconventional materials cutting technology with a fo-cus on abrasive water jet cutting and CO2 laser. The thesis is divided into theoretical and experimental section. The theoretical part describes principles and functions of nonconventional technologies, the basic division and practical applications. The practical part is focused on choosing the best technology with the production of samples and their subsequent comparison. The thesis recommends producer and type of the machine which best meets requirements on basis of the test results.

The thesis compares oxidation and fusion laser cutting methods in the production of sheet components called Trager consoles. Individual methods of laser cutting are compared in terms of achieved quality and properties of cutting areas. Consequently, the effect of these properties on consecutive technological operations, which are mainly threading and pressing the nuts into components, are evaluated. In the experimental part of the thesis the roughness of cut surfaces was measured and the cuts were classified into quality classes according to the ČSN EN ISO 9013 standard. Metallographic samples were taken in order to measure hardness and determine its course in the direction from the cutting edge into the material. The metallographic samples were further used for capturing detailed images on the microscope and assessing the quality of nuts pressing. Afterwards, the cut moments affecting taps were measured in order to verify the impact of cutting edge properties on threading. These measurements provided sufficient data for comparing the influence of cutting edge properties in individual methods of laser cutting on consecutive operations. Finally, individual methods were compared in terms of production costs. According to all the data and the conclusions reached, fusion method was identified as the most suitable method of laser cutting for components manufacturing.

At the Dawn of the 21st century, the field of specialty optical fibers experienced a scientific revolution with the introduction of the stack-and-draw technique, a multi-steps and advanced fiber fabrication method, which enabled the creation of well-controlled micro-structured designs. Since then, an extremely wide variety of finely tuned fiber structures have been demonstrated including novel materials and novel designs. As the complexity of the fiber design increased, highly-controlled fabrication processes became critical. To determine the ability of a novel fiber design to deliver light with properties tailored according to a specific application, several mode analysis techniques were reported, addressing the recurring needs for in-depth fiber characterization. The first part of this dissertation details a novel experiment that was demonstrated to achieve modal decomposition with extended capabilities, reaching beyond the limits set by the existing mode analysis techniques. As a result, individual transverse modes carrying between ~0.01% and ~30% of the total light were resolved with unmatched accuracy. Furthermore, this approach was employed to decompose the light guided in Large-Mode Area (LMA) fiber, Photonic Crystal Fiber (PCF) and Leakage Channel Fiber (LCF). The single-mode performances were evaluated and compared. As a result, the suitability of each specialty fiber design to be implemented for power-scaling applications of fiber laser systems was experimentally determined. The second part of this dissertation is dedicated to novel specialty fiber laser systems. First, challenges related to the monolithic integration of novel and complex specialty fiber designs in all-fiber systems were addressed. The poor design and size compatibility between specialty fibers and conventional fiber-based components limits their monolithic integration due to high coupling loss and unstable performances. Here, novel all-fiber Mode-Field Adapter (MFA) devices made of selected segments of Graded Index Multimode Fiber (GIMF) were implemented to mitigate the coupling losses between a LMA PCF and a conventional Single-Mode Fiber (SMF), presenting an initial 18-fold mode-field area mismatch. It was experimentally demonstrated that the overall transmission in the mode-matched fiber chain was increased by more than 11 dB (the MFA was a 250 ?m piece of 50 ?m core diameter GIMF). This approach was further employed to assemble monolithic fiber laser cavities combining an active LMA PCF and fiber Bragg gratings (FBG) in conventional SMF. It was demonstrated that intra-cavity mode-matching results in an efficient (60%) and narrow-linewidth (200 pm) laser emission at the FBG wavelength. In the last section of this dissertation, monolithic Multi-Core Fiber (MCF) laser cavities were reported for the first time. Compared to existing MCF lasers, renown for high-brightness beam delivery after selection of the in-phase supermode, the present new generation of 7-coupled-cores Yb-doped fiber laser uses the gain from several supermodes simultaneously. In order to uncover mode competition mechanisms during amplification and the complex dynamics of multi-supermode lasing, novel diagnostic approaches were demonstrated. After characterizing the laser behavior, the first observations of self-mode-locking in linear MCF laser cavities were discovered.