This PhD thesis focuses on the study of mode locked laser diodes based on novel optimized InAs Quantum Dash structures grown on InP substrates. It covers several important modelling aspects, the clean room processing of single and two section shallow ridge waveguide lasers, characterization of the fabricated devices and the evaluation of their performance in different application scenarios. Systematic characterization experiments and subsequent analyses have allowed to gain a much deeper comprehension of the physical mechanisms related to the mode locking regime in these devices, thus far not completely understood. This has allowed to better control most of the main physical phenomena limiting device performance, resulting in first demonstrations of record peak power, sub-picosecond pulse, low radio frequency linewidth and high repetition frequency mode locked lasers grown on InP substrates, opening the way to a vast number of potential applications in the 1.55 µm telecommunication window

Ce travail de thèse concerne le développement d’un laser à fibre générant des impulsions rectangulaires très énergétiques et accordables à l’échelle du temps et des impulsions géantes à haute énergie. En premier temps,nous avons développé un modèle numérique pour étudier la génération des impulsions rectangulaires dans un laser à fibre en forme de huit à double amplificateur.L’objectif est de montrer l’impact de l’effet non linéaire induit par la fibre micro structurée sur le contrôle de la durée d’impulsion rectangulaire générée par le laser. Un ensemble de paramètres laser nous a permis ainsi de générer des impulsions rectangulaires à haute énergie dans le régime de la résonance du soliton dissipatif (DSR). En plus, plusieurs expériences ont été mises en place pour optimiser la génération de l’impulsion DSR en termes d’énergie et de durée.Toujours sur le plan expérimental, des impulsions géantes à haute énergie à partir du laser à fibre verrouillé en phase couplé à un retard optique ont été obtenues. Cela nous a permis de générer une large plage de durée d’impulsion à l'échelle de μs à taux de répétition faible dans des cavités utilisant des absorbants saturables artificiels. / This work deals with the development of a fiber laser generating high energy and width tunable square pulses and high-energy giant pulses. First, we have developed a numerical model to study the generation of rectangular pulses in a double amplifier fiber laser. The objective is to study the impact of the non-linear effect induced by the microstructured optical fiber on the control of the square pulse duration. A set of laser parameters allowed us to generate high energy square pulses in the dissipative soliton resonance (DSR) regime. In addition, several experiments have been set up to optimize the generation of the DSR pulse in terms of energy and duration. Experimentally, high energy giant pulses from a passively mode-locked fiber ring laser coupled to a long external cavity are obtained. This allowed us to generate a wide range of pulse duration of μs at a low repetition rate in cavities using artificial saturable absorbers.

Made available in DSpace on 2016-03-15T19:37:29Z (GMT). No. of bitstreams: 1 Henrique Guimaraes Rosa.pdf: 986364 bytes, checksum: 89d6b316a537ef2cd3088d9200fd7183 (MD5) Previous issue date: 2010-08-06 / In this work we present a study about ultrashort pulse-train generation in Erbiumdoped fiber lasers, by the passive mode-locking technique, with the use of carbon nanotubes saturable absorbers. Carbon nanotubes were incorporated into laser cavities by two techniques: thermophoresis optically-driven deposition and thin films incorporating carbon nanotubes. The second technique has become more advantageous than the first one, because is possible to control carbon nanotubes concentration and thin films thicknesses. Additionally, we present a study about thin films incorporating carbon nanotubes optimization, in order to maximize generated output bandwidths in passively mode-locked Erbium-doped fiber lasers. We used 0.8 and 1.0 nm diameters carbon nanotubes, fabricated thin films with different transmission values (different αL product values), laser cavities with different features, such as total cavity length, total accumulated dispersion, repetition rate. In this context, best results were achieved with thin films containing 1.0 nm diameter carbon nanotubes, with films transmission about 37% (αL product close to 1.0), in 9 m long laser cavity (0.8 m of highly- Erbium-doped fiber and 8.2 m of SMF) of total accumulated dispersion of 0.153 ps/nm. The largest bandwidth measured, with those characteristics cavity parameters, was 5,7 nm. / Neste trabalho, apresentamos um estudo sobre a geração de trem de pulsos ultracurtos em lasers à fibra dopada com Érbio, utilizando a técnica de acoplamento passivo de modos com o uso de nanotubos de carbono como absorvedores saturáveis. Os nanotubos de carbono foram incorporados à cavidade laser através de duas técnicas: deposição guiada por termoforese e na forma de filmes finos contendo nanotubos de carbono, tendo a segunda técnica se mostrado mais vantajosa, pois por ela podemos ter controle sobre a concentração de nanotubos de carbono no filme e espessura do filme. Adicionalmente, apresentamos um estudo sobre a otimização da produção de filmes finos contendo nanotubos de carbono para maximização da largura de banda gerada em lasers à fibra dopada com Érbio. Utilizamos nanotubos de carbono de diâmetros de 0,8 nm e 1,0 nm, fabricamos filmes finos com transmitâncias diferentes (distintos valores para o produto αL), cavidades laser com diferentes características, tais como comprimento da cavidade, dispersão total acumulada, taxa de repetição. Neste contexto, os melhores resultados foram obtidos com filmes finos contendo nanotubos de carbono com 1,0 nm de diâmetro, em filmes cuja transmissão foi de 37% (produto αL aproximadamente 1,0), numa cavidade laser de aproximadamente 9 m de comprimento (basicamente composta de 80 cm de fibra altamente dopada com Érbio e 8,2 m de SMF), dispersão total acumulada da cavidade de aprox. 0,153 ps/nm. A maior largura de banda obtida, com estes característicos parâmetros da cavidade, foi de 5,7 nm.

Made available in DSpace on 2016-03-15T19:37:36Z (GMT). No. of bitstreams: 1 Paulo Guilherme Komninos.pdf: 1970255 bytes, checksum: df0cedf278c145259aed73c5d3775f90 (MD5) Previous issue date: 2011-02-21 / This work presents a study based on the numerical analysis of Erbium-doped fiber lasers using the technique of passive mode-locking for the laser working in pulsed regime. The equation describing the dynamics of a laser cavity is known as Ginzburg-Landau Equation, that in this work is solved numerically by the Split-Step Fourier Method. By this method, an algorithm was developed which was incorporated into the MATLAB environment so taht numerical calculations were made. The method was validated by comparing the results generated by the program (temporal pulse width due to the gain of the cavity with and without dispersion and nonlinearity) with the results published in literature. After validation of the method an experimental results were reproduced of an Erbium-doped fiber laser using thin films of carbon nanotubes as saturable absorbers. The laser generates a bandwidth of 5.7 nm for a cavity with a total length of 9 m. This experimental result was used as a calibration parameter in the initial simulations. Just by varying the length of the cavity in the simulation, results very close to the experiment were obtained. These results have helped in understanding some of the experimental variables. / Neste trabalho é apresentado um estudo baseado em análise numérica de lasers à fibra dopada com Érbio utilizando a técnica de acoplamento passivo de modos para que o mesmo opere em regime pulsado. A equação que descreve a dinâmica de uma cavidade laser é conhecida como Equação de Ginzburg-Landau, que neste trabalho é resolvida numericamente pelo Método Split-Step Fourier. Por este método, foi desenvolvido um algoritmo que foi incorporado ao ambiente MATLAB para serem feitos os cálculos numéricos. O método foi validado comparando os resultados gerados pelo programa (largura temporal do pulso devido ao ganho da cavidade com e sem dispersão e não-linearidade) com os resultados publicados na literatura. Após a validação do método, foram reproduzidos resultados experimentais de um laser a fibra dopada com Érbio usando como absorvedor saturável filmes finos de nanotubos de carbono. O laser gera uma largura de banda de 5,7 nm para uma cavidade de comprimento total de 9 m. Este resultado experimental foi utilizado como parâmetro de calibração inicial nas simulações. Apenas variando o comprimento da cavidade na simulação, foram obtidos resultados bem próximos ao do experimento. Esses resultados ajudaram na compreensão de algumas variáveis do experimento.

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.

Dans cette thèse, nous étudions expérimentalement la génération d'impulsions carrées très énergétiques et accordable à l’échelle nanosecondes et d'impulsions ultracourtes à haute puissance moyenne de sortie dans les lasers à fibre utilisant les nanomatériaux comme absorbant saturable. Tout d'abord, puisque la dynamique des impulsions est dominée par l'interaction de la non linéarité et de la dispersion chromatique cubique de la fibre avec un mécanisme de discrimination d'intensité appelé absorbant saturable, la stabilité d'une distribution harmonique en mode verrouillé est étudiée par injection externe d'une onde continue.Enfin, nous avons utilisés des absorbant saturable à base de nanomatériaux déposés sur des tapers optiques dans les lasers à fibre pour générer des impulsions ultracourtes avec une puissance de sortie moyenne élevée. / In this thesis, we investigate experimentally the generation of high energy nanosecond tunable square pulses and high output power ultrashort pulses in fiber lasers. First, since pulse dynamics are dominated by the interaction of the fiber's cubic Kerr nonlinearity and chromatic dispersion with an intensity-discriminating mechanism referred to as a saturable absorber, the stability of a harmonic mode-locked distribution is studied by external injection of a continuous wave. Finally, we implemented nanomaterial based saturable absorbers in fiber laser configuration to generate ultrashort pulses with high average output power. Different techniques of achieving such components are explicitly detailed: ultrashort pulse generation in ring cavities where graphene and topological insulators are deposited on optical tapers to form a saturable absorber.

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.

Les solitons dissipatifs (SD) sont des paquets d'onde auto-localisés qui apparaissent dans les systèmes dissipatifs spatialement étendus. En optique, tous les SD observés jusqu'à présent dans des systèmes propagatifs peuvent être classés en deux catégories, suivant la présence ou non d'un forçage externe, i.e. si la symétrie de phase est brisée ou non. Dans les systèmes forcés, les DS sont accrochés en phase au forçage alors que sans forçage, leur phase est libre et peu dériver en fonction du temps. Dans cette thèse nous étudions la formation d'états localisés propagatifs dans deux systèmes expérimentaux qui diffèrent fondamentalement par la présence ou l'absence d'un forçage externe. Le premier système est un laser à semiconducteur à cavité verticale (VCSEL) soumis à une boucle de rétro-action sélective en fréquence, qui accueille des DS se formant dans la dimension transverse à la propagation (2D). Nous analysons comment la synchronisation des fréquences longitudinales du système (verrouillage modal) peut mener à la formation d'un état localisé dans les trois dimensions : balles de lumière. Le deuxième système est un laser en anneau à semi-conducteur fortement multimode le long de la propagation, et forcé par une injection externe. Lorsque le forçage est légèrement désaccordé de la fréquence naturelle du système, il est possible d'observer des états localisés constitués par un tour de phase de 2 pi, immergés dans l'état homogène (synchronisé). Nous reportons ainsi la première observation de SD qui se forment dans la phase de l'onde optique : solitons de phase dissipatifs / Dissipative solitons (DS) are self-localized wave-packets appearing in spatially extended dissipative systems. In optics, all the DS that have been observed in propagative systems can be cast in two categories, depending on the presence or absence of an external forcing, i.e. the phase symmetry is broken or not. In forced systems, DS are locked in phase to forcing whereas without forcing, their phase is free an can wander in the course of time. In this thesis, we study the formation of propagative DS in two different experimental systems that fundamentally differ from the presence or lack of an external forcing. The first one is a Vertical Cavity Surface Emitting Laser (VCSEL) submitted to a frequency selective feedback, in which DS form in the transverse plane of the system (2D). We analyze how the synchronization of the longitudinal frequencies (mode-locking) can give rise to tri-dimensionnal localization of light: light bullets. The second system is a highly multimode semiconductor ring laser with external forcing, whose spatial extension takes place along the propagation dimension. When the forcing frequency is slightly detuned from the natural frequency of the system, we can see the appearance of self-confined 2 pi phase rotations embedded in a homogeneous (synchronized) state. We then report on the first observation of DS that form in the phase of the optical wave : dissipative phase solitons

Lasers find a wide range of applications in many areas including photo-biology, photo-chemistry, materials processing, imaging and telecommunications. However, the practical use of such sources is often limited by the bulky nature of existing systems. By fabricating channel waveguides in solid-state laser-gain materials more compact laser systems can be designed and fabricated, providing user-friendly sources. Other advantages inherent in the use of waveguide gain media include the maintenance of high intensities over extended interaction lengths, reducing laser thresholds. This thesis presents the development of Yb:tungstate lasers operating around 1μm in waveguide geometries. An Yb:KY(WO₄)₂ planar waveguide laser grown by liquid phase epitaxy is demonstrated with output powers up to 190 mW and 76 % slope efficiency. This is similar to the performance from bulk lasers but in a very compact design. Excellent thresholds of only 40 mW absorbed pump power are realised. The propagation loss is found to be less than 0.1 dBcm⁻¹ and Q-switched operation is also demonstrated. Channel waveguides are fabricated in Yb:KGd(WO₄)₂ and Yb:KY(WO₄)₂ using ultrafast laser inscription. Several of these waveguides lase in compact monolithic cavities. A maximum output power of 18.6 mW is observed, with a propagation loss of ~2 dBcm⁻¹. By using a variety of writing conditions the optimum writing pulse energy is identified. Micro-spectroscopy experiments are performed to enable a fuller understanding of the induced crystal modification. Observations include frequency shifts of Raman lines which are attributed to densification of WO₂W bonds in the crystal. Yb:tungstate lasers can generate ultrashort pulses and some preliminary work is done to investigate the use of quantum dot devices as saturable absorbers. These are shown to have reduced saturation fluence compared to quantum well devices, making them particularly suitable for future integration with Yb:tungstate waveguides for the creation of ultrafast, compact and high repetition rate lasers.

Les peignes de fréquences optiques, issus de diodes à blocage de modes, font partie des candidats potentiels pour les réseaux de transmission à multiplexage en longueurs d’onde (WDM). Cependant, les modes composant leur peigne, exhibent généralement des largeurs de raie optiques relativement élevées ( 1-100 MHz), rendant ainsi incompatible leur utilisation sur un réseau WDM employant des formats de modulation avancés d’ordre supérieur. Cette thèse étudie, une solution pour palier à cette limitation. La technique utilisée, dite d’asservissement à correction aval hétérodyne, effectue un traitement du flux lumineux en sortie du laser sans agir sur ce dernier, permettant de réduire le bruit de fréquence présent sur chacune des raies et par conséquent leur largeur de raie optique. Dans une première approche, la technique est appliquée à un laser mono-fréquence. Cela a permis d’une part de valider son fonctionnement et d’autre part d’identifier les limites intrinsèques du dispositif expérimental mis en place. Ainsi, nous démontrons que le niveau de bruit de fréquence minimum permis par notre système, correspond à un spectre optique de largeur de raie optique instantanée de 50 Hz et une largeur de raie de 1,6 kHz pour un temps d’observation de 10 ms. La technique est par la suite appliquée à une diode à blocage de modes actif. Le peigne de fréquences optiques ainsi généré, est composé de 21 modes, ayant tous une largeur de raie optique intrinsèque inférieure à 7 kHz, dont 9 modes sont sub-kHz. Pour un temps d’observation du spectre optique de 10 ms, ces modes exhibent tous une largeur de raie d’environ 37 kHz. Nous démontrons ainsi l’impact de la gigue d’impulsions sur les performances de la technique et nous soulignons l’intérêt d’une telle cohérence, pour le domaine des télécommunications optiques cohérentes (transmissions WDM cohérentes de type m-QAM avec des constellations d’ordre élevé, compatibles avec des débits multi-Tbit/s par raie). En dernier lieu, nous abordons une seconde technique consistant à pré-stabiliser la fréquence d’un laser par asservissement en boucle fermée. Elle repose sur l’utilisation d’un interféromètre à fibre déséquilibré comme référence pour réduire le bruit de fréquence d’un laser, situé particulièrement en basses fréquences. Appliquée à un laser mono-fréquence, elle a permis de réduire son bruit de fréquence technique conduisant ainsi à une nette amélioration de sa largeur de raie intégrée sur 3 ms, de 224 kHz à 37 kHz. Ce premier résultat représente un bon support vers l’exploration du potentiel des diodes à blocage de modes pour des applications métrologiques. / Optical frequency combs obtained from mode-locked laser diodes are potential candidates for WDM networks. However, their lines exhibit usually a broad optical linewidth ( 1-100 MHz). Thus their use is incompatible for high order modulation formats WDM based systems. This thesis investigates one solution to overcome this limitation. It consists of using a feed-forward heterodyne technique to reduce the frequency noise of each comb-line and consequently their optical linewidths. In a first approach, the technique is applied to a single-mode laser. This allowed us to validate its proper working and to identify the intrinsic limits of the experimental device set up. The latter analysis enabled us to reveal that the minimum achievable frequency noise level by our system, corresponds to a 50 Hz intrinsic optical linewidth spectrum and a 1,6 kHz optical linewidth based on 10 ms observation time. This technique is then applied to an actively mode-locked laser diode demonstrating, at our system output, a 21-line optical frequency comb with intrinsic optical linewidths reduced to below 7 kHz. It is worth noting that 9 among them, exhibit sub-kHz linewidths. For an observation time of 10 ms, all lines share the same optical linewidth, almost equal to 37 kHz. We thus show that the timing jitter impacts the technique performances. We also highlight the relevance of such coherence level for coherent optical communication. Lastly, we study a laser frequency pre-stabilization technique based on a locking to an unbalanced fiber interferometer. When applied to a single-mode laser, the technique showed a reduction of its technical frequency noise, thus leading to a clear improvement of its integrated optical linewidth from 224 kHz to 37 kHz for 3 ms observation time. This first result provides a good support towards the exploration of mode-locked laser diodes potential for metrological applications.