Dissertations / Theses on the topic 'Lasers à fibre – Innovation'
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1
Tiabi, Nadia. "Synthèse de préformes dopées ytterbium par voie poudre pour la réalisation des lasers à fibre de haute puissance." Electronic Thesis or Diss., Limoges, 2023. http://www.theses.fr/2023LIMO0049.
Abstract:
Les travaux présentés dans ce manuscrit s’inscrivent dans le cadre d’une thèse CIFRE en colla-boration entre le laboratoire Xlim et le centre technologique optique & lasers « ALPhANOV ». L’objectif principal de cette thèse consiste à développer des préformes dopées à l’ytterbium, conçues pour résister au phénomène de photo-noircissement (PN), en vue de leur utilisation dans des applications laser à haute puissance. Ce phénomène dégrade les performances des lasers et entraîne une réduction de leur puissance de sortie. Les travaux de cette thèse sont articulés autour de deux principaux axes. Le premier vise à définir la composition du cœur ainsi que la méthode de synthèse appropriée pour fabriquer des cœurs de préformes résistant face au photo-noircissement (PN). Le deuxième axe repose sur l’élaboration, la caractérisation et l’évaluation des performances optiques de la fibre obtenue. La matrice choisie pour être étudiée est la matrice alumino-phosphosilicate. Elle a été obtenue par une méthode de synthèse appelée « poudre en suspension ». Les différentes étapes de ce procédé de fabrication ont été validées depuis la synthèse de la préforme jusqu’à l’étirage de la fibre optique. Les tests optiques effectués sur la fibre optique ont révélé d’excellentes performances, avec une faible atténuation de 0.1 dB/m et une efficacité de conversion optique- optique très prometteuse de 76 %. L’évaluation de cette fibre face au phénomène de photo- noircissement a révélé une résistance exceptionnelle. Aucune décroissance en puissance n’a pu être constatée au cours des expériences effectuées sur plus de 100 hThe work presented in this manuscript is part of a PhD thesis carried out by CIFRE in collabora-tion between the laboratory of Xlim and the technological center of optics and lasers "ALPhA-NOV". The main objective of this thesis is to design ytterbium doped preforms that are resistant to the photodarkening (PD) phenomenon for use in high power laser applications.This phenomenon degrades laser performance and leads to reduced output. Two main areas are focused in this thesis. The first is the definition of the core composition and the appropriate synthesis method for the production of preform cores which are resistant to photodarkening (PD). The second is to develop, characterize and evaluate the optical performance of the resulting fiber. The matrix that has been chosen for the study is the alumino-phosphosilicate matrix. To obtain this matrix, a synthesis method called "powder in suspension" was used.From the synthesis of the preform to the drawing of the optical fiber, the different stages of the process have been validated. Excellent performance, with low attenuation of 0.1 dB/m and a very promising optical-to-optical conversion efficiency of 76%, was obtained from the optical tests performed on the fiber. The evaluation of the fiber against photodarkening showed an exceptional resistance. No performance degradation was observed over 100 hours
2
Baker, Stephen Ross. "Optical fibre lasers." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239585.
3
Pendock, Graeme John. "Optical fibre dye lasers." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308241.
4
Alvarez-Chavez, Jose Alfredo. "High-power fibre lasers." Thesis, University of Southampton, 2003. https://eprints.soton.ac.uk/15478/.
Abstract:
This thesis reports on the experimental study of high-power, high-energy, cladding-pumped, rare-earth (Yb3+, Er3+/Yb3+)-doped fibre lasers. Some of the main capabilities of fibre lasers such as: High brightness and thermal properties were exploited for the development of a variety of continuous wave (CW) and Q-switched devices, whose characteristics also includes compactness. Our devices could already be considered an option for several applications. The 25-year long scientific and commercial evolution that fibre lasers have experienced is discussed in the first two chapters. The invention of Erbium-doped fibre amplifiers (EDFA's) and Internet were two major breakthroughs, which launched the need of WDM systems and laser sources. Fibre lasers, are now considered a flexible and powerful device whose technology has finally reached its maturity. Cladding pumping is the technique employed in these experiments in order to pump double clad fibre lasers using high power, broad stripes and bars. In this work, several inner cladding shapes have been used to overcome the normally high mismatch between diode laser beams and inner cladding areas of fibre lasers. Chapter Three consists of a review of cladding-pumped fibre lasers. It describes how inner cladding geometry and pump absorption limits the output power scalability of these devices. Nonlinear effects and amplified spontaneous emission are also studied due to their implication they have over fibre lasers performance. Results on conventional, continuous wave (CW) fibre lasers including fibre characterization and employed launching techniques are described in Chapter Four. A new method to obtain high intensity laser beam output from an Yb3+-doped, cladding-pumped, highly multimode fibre laser has been proposed. In this experiment, we propose the use of fibre tapers to increase intensity and improve beam quality. In CW regime, our results show an intensity increase of ~3.5 times with a low power penalty of ~1 dB. Also, without tapering, a maximum output power of 21-W was reached with a slope efficiency of >80%. Using a simple set of optic elements such as a l/2 waveplate, a polarizing beam-splitter and a bulk grating, we investigated the polarization characteristics of an Yb3+ fibre laser, from which we obtained 6.5 W of single polarization tunable output in the range of 1070 to 1106 nm. As a free running laser, the system produced 18 W at 1090 nm and showed a threshold of 1.8 Watts. The experiment is our first approach for developing a reliable high-power Yb3+-doped fibre source, that could be used in conjunction with optical parametric oscillators (OPO) and amplifiers (OPA) to frequency convert to a broad band of wavelengths. Using a new design of ytterbium-doped fibre made in-house with the conventional modified chemical vapor deposition (MCVD) process, we explored the possibilities of energy storage with such a large mode area (LMA) fibre. The fibre system was capable of delivering energetic pulses of >2 mJ, which could suggest the feasibility of a pulsed fibre laser in the region of tens of milli-Joules. The experiment is described in Chapter Six, on which the experiment that uses the tapered fibre laser in Q-Switched regime is also described and compared to LMA fibre laser. Gaussian-type pulses were obtained which reached pulse energies of 0.6 mJ at 4 kHz using a tapered fibre laser and 1.3 mJ at 500 Hz using conventional laser, corresponding to average powers of 2.1 Watts for the tapered laser and 0.8 watts for the conventional laser. Er3+/Yb3+-doped fibre lasers were part of our experimental work. This co-doping technique allows pumping of Yb3+ ions using broad-stripe high-power pump sources to reach much higher output power levels. Efficient energy transfer from excited Ytterbium ions into Erbium is achieved. From a preliminary study, the fibre laser showed a threshold of 160 mW and a slope efficiency of 49% with respect to absorbed pump power. The maximum output power was 6.2 watts at 1535 nm and a linewidth of 1 nm. One of our co-doped fibre devices produced 16.8 W of continuous wave, multimode laser power at the interesting wavelength of operation of 1550 nm. Finally, conclusions and future work are included in Chapter Eight.
5
Malleville, Marie-Alicia. "Évaluation du potentiel des fibres apériodiques à très large aire modale pour la réalisation de sources laser impulsionnelles." Thesis, Limoges, 2020. http://www.theses.fr/2020LIMO0009.
Abstract:
Ces travaux de thèse s’inscrivent dans une collaboration long-terme entre le laboratoire Xlim et l’entreprise EOLITE Systems dans le but de développer de nouvelles fibres optiques à très grande aire modale typiquement capables de délivrer une puissance moyenne supérieure à 200 W et une puissance crête de l’ordre de 1 MW avec une émission monomode transverse à 1030 nm. Pour cela, des fibres optiques à microstructuration apériodique (FA-LPF) ont été développées en vue d’améliorer les performances des fibres commerciales, en repoussant en particulier le seuil des instabilités modales transverses. Une étude expérimentale sans précédents a été menée pour mettre en évidence l’influence de la structure de la fibre, de l’architecture de la source et du diamètre de champ modal sur le seuil d’apparition du phénomène. Par ailleurs, la fibre commerciale a été remplacée par une FA-LPF dans un prototype laser industriel, et a donné lieu à une validation de principe, tant du point de vue des performances pures que du vieillissement. La faisabilité d’une fibre micro-structurée courte et efficace (de 50 cm de long), a également été étudiée, en passant par une augmentation de la concentration en ions ytterbium dans le coeur de la FA-LPF ou encore par l’amélioration du ratio coeur/gaine. Finalement, un concept de fibre à coeur enterré a permis d’atteindre des dimensions de coeur supérieures à 110 μm tout en maintenant une émission monomode transverseThese Ph.D work is conducted in the context of a long-term collaboration between Xlim laboratory and the company EOLITE Systems in order to develop new large mode area fibers typically capable of providing up to 200 W of average output power and a peak power of 1 MW while maintaining a transverse single-mode emission at 1030 nm. For that purpose, optical fibers with an aperiodic microstructuration (FA-LPF) were developed in order to improve the performances of commercial fibers, mainly by pushing further the transverse mode instabilities power threshold. An unprecedented experimental study has been conducted to investigate the influence of the fiber structure, the laser source architecture and the mode field diameter. Furthermore, by replacing the commercial fiber by a FA-LPF in an industrial laser prototype, as a proof-of-concept, the FA-LPF permits to obtain a laser source with at least similar properties as those of the laser sources of the company regarding the laser efficiency or the lifetime test. The feasibility of a microstructured fiber shorter and still efficient (50 cm-long), has also been studied, by increasing the ytterbium ions concentration in the FA-LPF core or by improving the core to clad ratio. Finally, a new concept of fiber with a depressed-index core led to core diameters higher than 110 μm while maintaining a transverse single-mode emission
6
Gloag, Andrew John. "Tunable erbium doped fibre lasers." Thesis, University of Strathclyde, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249838.
7
Zhu, Yanjun. "Novel fibre lasers and amplifiers." Thesis, King's College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392685.
8
Lin, Jin Tong. "Polarisation effects in fibre lasers." Thesis, University of Southampton, 1990. https://eprints.soton.ac.uk/404646/.
Abstract:
Single-mode fibre lasers are a new class of active fibre device, which play a remarkable role in optical fibre communications and sensors. They also exhibit a number of new phenomena, one of the most important being polarisation effects. In this thesis, new unexpected fundamental polarisation effects in fibre lasers have been discovered. The phenomena are fluorescence depolarisation, the existence of orthogonal polarisation eigenmodes, and the dependence of the output polarisation on the pump polarisation state. A unified theoretical model, incorporating the electric dipole model for rare-earth ions in a glass matrix, is formulated. The concept of effective pump power is introduced and can be applied to existing laser theory; thus laser performance characteristics such as thresholds, slope efficiencies and the polarisation state of the output can be predicted accurately. The good agreement between theory and experiment enables the derivation of the polarised cross-section ratio. This has been done for Nd3+ and Er3+ ions in silica fibres. From the theoretical analysis the optimum condition for single polarisation operation is deduced. An effective technique for making single-polarisation single-mode (SPSM) fibre lasers has been developed using an integral fibre polariser. The advantages of this technique are low insertion loss, high polarisation extinction ratio and compatibility with existing single-mode fibre components. Laser-diode-pumped SPSM fibres of high performance, both in continuous-wave and Q-switched operations, have been achieved.
9
Mears, Robert Joseph. "Optical fibre lasers and amplifiers." Thesis, University of Southampton, 1987. https://eprints.soton.ac.uk/396453/.
Abstract:
This thesis describes the development and characterisation of single-mode optical fibre lasers and amplifiers. Although the fibre laser configuration was first employed over twenty years ago, its application to conventional optical fibre technology has not been demonstrated previously. The new devices are based on single-mode fibres doped with rare-earth ions, notably neodymium and erbium. The combination of strong absorption bands, long fluorescence lifetimes; low fibre losses in the infra-red and small fibre cores have made possible very low threshold and efficient fibre lasers. Experiments on the tunability, output spectra and pulsed operation of these devices are described. A number of world firsts, including the Lowest, threshold and widest tuning range of a doped glass laser, and the efficient CW operation of an erbium-doped three level laser, have been achieved. High-gain amplification at 1.54µm, the preferred wavelength for optical communication, has also been demonstrated. The results have been modelled by adapting conventional laser theory to the single-mode fibre configuration, and some simple design criteria are considered.
10
Hu, Tomonori. "Ultrafast Mid-infrared Fibre Lasers." Thesis, The University of Sydney, 2015. http://hdl.handle.net/2123/13885.
Abstract:
Laser light has enabled some of the most important scientific discoveries and innovations, and research in newer types of lasers continues to reveal more applications. Mid-infrared light, which interacts strongly with naturally occurring molecules, holds many promises in sensing and medical technologies and their applications are now beginning to appear. This surging development will strongly benefit with the availability of field-usable, compact and robust sources of mid-infrared light. The fibre lasers have the extreme potential to achieve this; however their performance in terms of generating ultrafast pulses of mid-infrared light has not yet been demonstrated. Here we explore the potential fluoride fibre lasers have in the ultrafast pulsed regime. We have demonstrated this via the production of nanosecond, to picosecond, and finally femtosecond pulses from fluoride fibre lasers using a variety of methods. These demonstrations reveal that fluoride fibres lasers are strong candidates to be an ultrafast mid-infrared source, with applications ranging from frequency comb based molecular sensing to next generation laser scalpels.
11
Kelleher, Edmund J. R. "Advancements in mode-locked fibre lasers and fibre supercontinua." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9584.
Abstract:
The temporal characteristics and the spectral content of light can be manipulated and modified by harnessing linear and nonlinear interactions with a dielectric medium. Optical fibres provide an environment in which the tight confinement of light over long distances allows the efficient exploitation of weak nonlinear effects. This has facilitated the rapid development of high-power fibre laser sources across a broad spectrum of wavelengths, with a diverse range of temporal formats, that have established a position of dominance in the global laser market. However, demand for increasingly flexible light sources is driving research towards novel technologies and an improved understanding of the physical mechanisms and limitations of existing approaches. This thesis reports a series of experiments exploring two topical areas of ongoing research in the field of nonlinear fibre optics: mode-locked fibre lasers and fibre-based supercontinuum light sources. Firstly, integration of novel nano-materials with existing and emerging fibre-based gain media allows the demonstration of ultrafast mode-locked laser sources across the near-infrared in a conceptually simple, robust, and compact scheme. Extension to important regions of the visible is demonstrated using nonlinear conversion. Scaling of pulse energies in mode-locked lasers can be achieved by operating with purely positive dispersion for the generation of chirped pulses. It is shown unequivocally, through a direct measurement, that the pulses generated in ultra-longmode-locked lasers can exist as highly-chirped dissipative soliton solutions of the cubic (and cubic-quintic) Ginzburg Landau equation. The development of a numerical model provides a framework for the interpretation of experimental observations and exposes unique evolution dynamics in extreme parameter ranges. However, the practical limitations of the approach are revealed and alternative routes towards achieving higher-energy are proposed. Finally, an experimental and numerical study of the dependence of continuous-wave pumped supercontinua on the coherence properties of the pump source shows an optimum exists that can be expressed as a function of the modulation instability period. A new and simplified model representing the temporal fluctuations expressed by continuous wave lasers is proposed for use in simulations of supercontinua evolving from noise. The implications of the experiments described in this thesis are summarised within the broader context of a continued research effort.
12
Chestnut, David Alexander. "Fibre lasers and amplifiers with nonlinearity." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410006.
13
Cowle, Gregory John. "Narrow-linewidth erbium-doped fibre lasers." Thesis, University of Southampton, 1991. https://eprints.soton.ac.uk/399361/.
Abstract:
This thesis describes research towards narrow-linewidth and single-longitudinal-mode erbium-doped fibre lasers operating on the 1.55µm region. The work is concerned with the physics and technology of narrow-linewidth fibre lasers. Factors which affect the spectral width and number of modes oscillating in an erbium-doped fibre laser are described, with particular reference to spatial holeburning, the primary cause of multi-mode oscillation. Novel resonator configurations for narrow-linewidth operation are described, in both standing-wave and travelling-wave arrangements, with linewidths as narrow as 10Hz being achieved. The development of narrow-bandwidth distributed Bragg reflectors is discussed. Resonator configurations discussed include short fibre lasers with narrow bandwidth reflectors, polarimetric coupled-cavity fibre lasers, travelling-wave fibre ring lasers and travelling-wave fibre loop lasers. Travelling-wave operation is demonstrated to be a powerful technique for realising single-frequency fibre laser operation. Linewidths as narrow as 10kHz are demonstrated in long fibre laser resonators. The potential for high efficiency and broad tuning ranges are illustrated. The statistics of phase noise in erbium-doped fibre amplifiers are characterised, by measurements of spectral broadening of a signal passing through the amplifier. The process of spectral broadening is modelled using a rotating vector approach. The implications for amplification of narrow bandwidth signals are discussed.
14
Gray, Stuart. "Fibre soliton lasers and their applications." Thesis, University of Southampton, 1997. https://eprints.soton.ac.uk/394565/.
Abstract:
This thesis presents experimental and theoretical studies of picosecond soliton generation in passively modelocked optical fibre lasers and their transmission in optical fibre systems. Chapter 2 describes an investigation into the timing jitter of a self-stabilized, passive harmonically modelocked fibre laser. It is demonstrated that the mechanism for self-stabilization is the resonant enhancement of acoustic waves excited by the soliton pulses within the cavity and that timing jitter as low as 600 fs can be achieved with this technique. A new fibre laser cavity configuration incorporating a multi-quantum-well saturable absorber to achieve improved self-starting characteristics is presented in chapter 3. The presence of the multi-quantum-well also creates a self-stabilization effect through carrier induced refractive index changes. This laser generates transform limited pulses at repetition rates of up to 3 GigaHertz with very low levels of background radiation. The development of a simple and stable source of picosecond solitons allowed studies of the properties of these pulses in long distance transmission systems which share many characteristics with fibre lasers. In chapter 4, a Raman amplifier with a pump wavelength of 1535 nm was designed to provide a distributed gain for the investigation of soliton properties over distances of 100 dispersion lengths. The pump source developed for the amplifier was a superfluorescent amplified spontaneous emission source capable of delivering up to 1300 MW of power in a 0.5 nm bandwidth. Experiments on picosecond soliton pulse propagation using Raman amplification are described in chapter 5 and we demonstrate that the properties of individual pulses can be maintained over distances of greater than 150 dispersions lengths. This chapter also presents investigations of the behaviour of soliton pulse pairs reveals several limitations to high bit rate soliton communications over such long distances. These restrictions are caused by pulse energy fluctuations in combination with the soliton self frequency shift and the build up of dispersive radiation emitted by the solitons.
15
Burns, David. "Fibre-compatible modelocked lasers at 1.5μm." Thesis, University of St Andrews, 1991. http://hdl.handle.net/10023/14158.
Abstract:
This thesis describes techniques for the generation of ultrashort optical pulses using semiconductor lasers. Active modelocking through gain modulation is applied to 1.?m InGaAsP semiconductor lasers which utilise microlensed optical fibres as external-cavity components, and tunable optical pulses of ~5ps duration have been generated. Particular attention has been given to suppression of the noisy subpulse features associated with low-frequency modelocked semiconductor lasers. This has led to two suppression methods applicable to symmetric (or balanced) and asymmetric cavity configurations, allowing the generation of clean, single feature short pulses of 7-10ps duration with peak powers in excess of 300mW. The physical phenomena relating to such processes will be outlined. Further amplification of these pulses using an erbium- doped fibre amplifier has resulted in output peak powers in the 5W range. A study of the phase-noise characteristics of these modelocked laser systems was undertaken using a high-speed photodetector and wide-band spectrum analyser arrangement. This characterisation allowed improvements in the rms pulse timing jitter from >2ps to below 300fs in the frequency range 50-5000Hz. Novel modelocked laser configurations were also constructed where the cavity components included both a semiconductor amplifier and an erbium-doped fibre amplifier. Linear and ring hybrid lasers were investigated with resultant pulse durations as short as 3ps with high peak power and excellent stability. CW and mechanical Q-switched doped fibre lasers were configured in diffraction grating tuned cavities with high output coupling (R=4%). Unprecedented output powers of up to 700mW tunable over ~100nm around 1.55mum, and 800mW tunable around 1.08mum were obtained. Also the value of 800W peak power for the 80ns output pulses from the Q-switched erbium-doped fibre laser amounts to the most intense pulse created thus far from any fibre laser device. Optimisation of the total tuning range attainable from erbium-doped fibre lasers via length tuning resulted in a variety of nonlinear phenomena, namely self Q-switching and optical bistability at the long wavelength tail of the tunable range.
16
Leung, Ian Kin-Hay Electrical Engineering & Telecommunications Faculty of Engineering UNSW. "Development of composite cavity fibre lasers for fibre laser hydrophone systems." Publisher:University of New South Wales. Electrical Engineering & Telecommunications, 2008. http://handle.unsw.edu.au/1959.4/41248.
Abstract:
In this thesis, my main focus was to establish a novel composite-cavity fibre laser (CCFL) and to apply it in sensing, particularly in the hydrophone application. The CCFL that I have proposed is formed by writing three wavelength matched fibre Bragg gratings directly into a continuous length of doped fibre. I have also examined the relative advantages and disadvantages of interferometric and intensity-based hydrophone systems, and have established a hydrophone system that can be switched between the two modes of operation, by making use of digital signal processing. I have established a theoretical model to study the lasing and spectral characteristics of the CCFL. My analysis showed that whilst the CCFL have significantly different phase and threshold conditions from the common semiconductor diode lasers with external cavity, the CCFL also have mode-limiting properties that are often sought after. Through simulations, I was able to identify that a non-uniform straining scheme, that is, when one of the sub-cavities of the CCFL is restrained from strain, can improve the sensitivity with respect to existing single cavity fibre lasers, in both the frequency and intensity domains. My simulations also showed that the sensitivity of such a straining scheme can be optimised by tuning the reflectivity of the gratings, sub-cavity lengths, doping concentration and pump power. I have fabricated multiple CCFLs using the in-house grating writing facilities, and have experimentally assessed their power and spectral related lasing characteristics. Whilst having a significantly longer total cavity length compared to typical fibre lasers, the CCFLs demonstrated stable single longitudinal mode operation and narrow linewidth in the order for a few tens of kHz. Asymmetric output power and frequency as a result of unequal sub-cavity lengths were also examined. Finally, I conducted sensing experiments by applying the CCFLs in strain monitoring and intensity-based hydrophone. My results showed that the non-uniform straining scheme had significantly improved the intensity response of the CCFL, and that the acoustic pressure and frequency can be determined by directly sampling and applying Fourier transform to the output intensity of the fibre laser.
17
Xiang, Dao. "Study of Random Fibre Lasers and Applications." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32767.
Abstract:
The properties of two novel random fibre lasers, in which stimulated Brillouin scattering supplies the effective gain mechanism and Rayleigh scattering along the standard telecommunication optical fibre provides random distributed feedback, are characterised. Firstly, ultra-narrow microwave signals with a Dirac delta function profile are successfully created by beating two random-lasing near-Gaussian beams, arising from the synchronization of optical modes from two Stokes signals with random phase accumulated over the ultra-long optical fibre. This finding provides a completely new approach to synthesise high spectral purity microwave signals from Brillouin fibre lasers with randomised feedback. In addition, we also develop a theoretical model of the random fibre Fabry-Pérot resonator based on the fact that the pump depletion effect naturally selects out the effective Rayleigh feedback regions localised in both ends of this long fibre. A narrow random-laser output with the linewidth of ~860 Hz is experimentally demonstrated and is employed to characterise the linewidth of the pump light. Furthermore, the random laser dynamics is studied and one application towards the physical entropy source is eventually achieved.
18
Rulkov, Andrey. "All-fibre lasers for nonlinear wavelength conversion." Thesis, Imperial College London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501290.
Abstract:
High power fibre laser technology is a promising and rapidly developing branch of photonics. The recent progress in speciality fibres and high power ultrafast fibre sources opened an attractive possibility for the extension of the operating wavelength of fibre lasers to both the visible and infrared through the controlled action of nonlinear optical effects. This work describes experiments on highly integrated fibre optic sources extending the wavelength of high power fibre lasers towards 590 nm in the visible, which is inadeqately covered by existing high power light sources. Another major aim of the experimental work was the utilisation of the process of supercontinuum generation in fibre to create more than mW/nm level spectral brightness extremely broadband sources with a continuous coverage over a selectable wavelength range in both the visible and near infrared regions. In order to fulfil the experimental programme, speciality fibre lasers, optimised for efficient nonlinear wavelength conversion, had to be developed. A secondary aim to benefit from the advantages of all-fibre configurations whenever possible. For the supercontinuum generation, all-fibre modelocked laser sources were developed and amplified to 50 kW peak power with 5 ps duration. The amplified output was spliced to a speciality photonic crystal fibre to produce a picosecond supercontinuum spanning from 530 to 1750 nm with 1.5 W average power. Additionally, supercontinuum generation in the 1.5-2.0 pm wavelength range was demonstrated using simple CW laser pump sources and highly nonlinear step index fibre.
19
BOETTI, NADIA GIOVANNA. "Nd3+ doped phosphate glass optical fibre lasers." Doctoral thesis, Politecnico di Torino, 2014. http://hdl.handle.net/11583/2543408.
Abstract:
In this thesis a Nd3+-doped phosphate glass was developed in-house in order to obtain a glass stable, robust, able to incorporate high amount of RE ions and suitable for fibre drawing. Several Nd3+-doped phosphate glass samples were fabricated by doping the developed host glass with concentrations of Nd3+ up to 10 mol%. The samples were then characterized in order to measure their physical, thermal and spectroscopic properties. The effect of Nd3+ doping concentration on emission spectra and lifetimes was investigated in order to study the concentration quenching effect on luminescence performance.
With the aim to fabricate a Nd3+-doped double cladding (DC) optical fibre laser emitting at 1.06 µm, three different phosphate glasses using a custom designed glass composition, were fabricated. By changing properly the concentration and constituents present in our phosphate glass, the refractive indexes of the three glasses were adjusted in order to obtain an adequate numerical aperture between core and inner cladding, and between inner and outer cladding, while maintaining similar thermo-mechanical properties in view of the fibre drawing process.
A Nd3+-doped DC optical fibre was fabricated by preform drawing using a drawing tower facilities available in the research group laboratory. Morphological and optical characterisation of the fibre were carried out in order to evaluate fibre quality.
In order to optimize Nd3+-doped fibre laser design, a numerical analysis of the lasers was performed.
At last, a CW cladding pumped fibre laser based on 9 cm of fabricated Nd3+-doped optical fibre was experimentally demonstrated.
20
Cranch, Geoffrey Alan. "Large-scale remotely interrogated arrays of fibre-optic interferometric sensors and fibre lasers." Thesis, Heriot-Watt University, 2001. http://hdl.handle.net/10399/1197.
Abstract:
The development of fibre-optic interferometric sensor arrays for application in underwater acoustics has been an area of active research since the late 1970's. The technology has reached a level whereby prototype arrays have been successfully demonstrated in sea-trials. However, the recent development of several new technologies may significantly increase the size and performance of these arrays. We demonstrate the potential increase in multiplexed array sizes using architectures based on combining dense wavelength division multiplexing and time division multiplexing. These architectures also include erbium doped fibre amplifiers for post, pre, inline and remote amplification in order to increase the standoff distance between the array and electronics unit. We also theoretical investigate the limitations imposed on the number of sensors that can be multiplexed, due to nonlinear transmission effects in the link fibre in the presence of high optical powers and multiple wavelengths. We also demonstrate novel DFB erbium doped fibre lasers as optical sources. These sources exhibit linewidths significantly narrower than semiconductor DFB lasers, which are currently used in many sensor arrays, and thus may provide a significant improvement in sensor resolution. We investigate the intensity and frequency noise properties of these lasers, their modulation properties and successfully develop intensity noise and frequency noise reduction techniques. We also investigate the potential of fibre-optic acoustic vector sensors and demonstrate fibre-optic flexural disk accelerometers. Finally, we demonstrate polymer coated in-fibre Bragg gratings as pressure and temperature sensors and investigate polymer coatings as a means to increase the acoustic responsivity of fibre laser acoustic sensors.
21
Wright, Fiona Cameron. "Highly polarised ytterbium doped photonic crystal fibre lasers." Thesis, University of Strathclyde, 2010. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=11869.
22
Olivier, Michel. "Interactions de solitons dans les lasers à fibre." Thesis, Université Laval, 2008. http://www.theses.ulaval.ca/2008/25290/25290.pdf.
23
Burns, David. "Fibre-compatible modelocked lasers at 1.5#mu#m." Thesis, University of St Andrews, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317786.
24
Kallimani, Klio I. "Modelling of external cavity lasers using fibre gratings." Thesis, University of Essex, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336948.
25
Ye, Chen Chun. "Spectroscopy of erbium-doped fibre amplifiers and lasers." Thesis, University of Southampton, 1995. https://eprints.soton.ac.uk/399077/.
Abstract:
This thesis describes work done in investigating Er3+-doped fibre amplifiers and lasers, with emphasis on the spectral properties and diagnosis of ion-ion interaction processes in the glasses and fibres. Ion-pair upconversion and uniform upconversion in Er3+-doped silicate fibres have been directly and separately observed for the first time, by examining upconversion fluorescence. An upper limit to the Er3+ ion-pair lifetime of a few microseconds has been determined. Different effects of the two upconversion mechanisms on the 1.54µm fluorescence have been examined. Ion-pair upconversion in an Al/Ge/Si or an Al/Si host increases far less with increasing Er3+ concentration than in a Ge/Si host, while there is no significant difference in uniform upconversion between them for a given Er3+ concentration. Uniform upconversion constants for various fibres are determined through measuring the maximum decay rate of the 1.54µm fluorescence. The 1.7µm ESA spectrum from the 4H13/2 level has been measured for Er3+-doped silicate fibre and ion-exchanged silicate planar waveguides, and the uniform upconversion constants are estimated. The existence of dual excited-state energy transfer (DESET) in Er3+/Yb3+- doped phospho-silicate fibres has been inferred from measurement of the ESA spectrum around 1.1µm. The absence of ESA at pump wavelength 1.064µm has also been confirmed. The DESET process has been examined for the first time by measurements of 1.064µm pump throughput characteristics of the fibre. Short Er3+/Yb3+ amplifiers pumped at around 970nm have been numerically characterized. The advantage of codoping of Yb3+ is shown to be the potential for higher gain at shorter amplifier length. By examining Er3+-doped fibre preforms with differing co-dopant ions, Ta5+- codoped fibre is shown to be competitive with Al3+-codoped fibre for Er3+-doped fibre devices. A SiGeTaEr fibre laser has been demonstrated for the first time. Spectral properties of Er3+-doped Ga2S3:La2S3 have been studied. Emission and absorption spectra, including for the first time the 2.7µm emission, are measured. Radiative and non-radiative transition rates are calculated and compared with the measured lifetimes. Characteristics of ion-ion energy transfer processes in the glass are discussed. A numerical model has been developed to predict the Performance of Er3+:Ga:La:S fibre devices, including short amplifiers operating at 1.54µm, 980nm upconversion lasers.
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Selvas-Aguilar, Romeo de Jesus. "Cladding-pumped neodymium and ytterbium doped fibre lasers." Thesis, University of Southampton, 2004. https://eprints.soton.ac.uk/41526/.
Abstract:
This thesis details my work on both high-power neodymium-doped fibre lasers (at around 1.1 μm and around 0.9 μm) and ytterbium-doped fibre lasers (at 980 nm). The main subjects were the study of efficient three-level compact continuous-wave fibre lasers and their power scaling.Ytterbium-doped fibre lasers (YDFLs) with emission at 980 nm were also investigated. I, in collaboration, obtained the highest reported output power from any compact single-mode 980 nm laser to this point. For this, speciality fibres, with special core and inner-cladding designs, were developed, notably the jacketed-air-clad (JAC) fibre, with properties that are not attainable in conventional double-clad fibres. The JAC structure allows for a small pump waveguide (inner cladding) with a high NA. This is an essential advantage for lasers operating on a transition to the ground state, such as YbThere are many considerations involved with making practical, reliable, and usable 980 nm fibre devices. The integration of all required functions into a single fibre device with a small, high-NA, inner cladding is a challenge that required a large research effort to solve. A thorough and careful design and characterisation effort led to the milestone achievement of an all-fibre pigtailed fibre laser at 980 nm, which later on was used in practice as a pump source for an 8-channel DFB fibre laser transmitter array. In addition, a 980 nm Q-switched fibre laser is realised in a cladding-pumped configuration for the first time.Furthermore, a fibre laser cladding-pumped by a high brightness intra-cavity beam-combined diode was demonstrated. Here, a multi-stripe, multi-mode diode was set-up for intra-cavity beam combination and used for cladding-pumping of fibre lasers with a small inner cladding. This high-brightness pumping scheme with a multi-emitter diode appears very attractive for power scaling of three-level fibre lasers.
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Debut, Alexis. "Cohérence temporelle des lasers Brillouin à fibre optique." Lille 1, 2000. http://www.theses.fr/2000LIL10094.
Abstract:
Le travail presente dans ce memoire porte sur l'etude theorique et experimentale de la coherence temporelle des lasers brillouin a fibre optique. Dans le cadre du modele coherent a trois ondes decrivant le comportement dynamique des lasers brillouin, nous etablissons une relation analytique liant la phase de l'onde stokes a celle de l'onde de pompe. Contrairement aux lasers classiques, nous montrons que le bruit de phase du laser de pompe est transfere a l'onde stokes emise apres avoir ete filtre et reduit. Il en resulte que le temps de coherence de l'onde stokes est beaucoup plus important que celui de l'onde de pompe. Le rapport entre ces deux temps de coherence est donne par un facteur k 2. Ce facteur depend simplement et uniquement du taux de perte de la cavite et du taux d'amortissement de l'onde acoustique. Nous presentons ensuite un protocole experimental dans lequel nous enregistrons la reponse du laser brillouin a une modulation de frequence du laser de pompe. Le rapport entre l'indice de modulation de l'onde de pompe et celui de l'onde stokes nous donne la valeur du coefficient k. Les resultats experimentaux confirment avec succes nos predictions theoriques. Pour terminer, nous appliquons nos methodes d'analyse a un laser brillouin injecte optiquement. Nous demontrons experimentalement et theoriquement que celui-ci emet un rayonnement stable en intensite quelque soit le regime de fonctionnement du laser brillouin.
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Ivanenko, Aleksey. "Ultra-long mode-locked Er-droped fibre lasers." Thesis, Aston University, 2013. http://publications.aston.ac.uk/20855/.
Abstract:
The development of ultra-long (UL) cavity (hundreds of meters to several kilometres) mode-locked fibre lasers for the generation of high-energy light pulses with relatively low (sub-megahertz) repetition rates has emerged as a new rapidly advancing area of laser physics. The first demonstration of high pulse energy laser of this type was followed by a number of publications from many research groups on long-cavity Ytterbium and Erbium lasers featuring a variety of configurations with rather different mode-locked operations. The substantial interest to this new approach is stimulated both by non-trivial underlying physics and by the potential of high pulse energy laser sources with unique parameters for a range of applications in industry, bio-medicine, metrology and telecommunications. It is well known, that pulse generation regimes in mode-locked fibre lasers are determined by the intra-cavity balance between the effects of dispersion and non-linearity, and the processes of energy attenuation and amplification. The highest per-pulse energy has been achieved in normal-dispersion UL fibre lasers mode-locked through nonlinear polarization evolution (NPE) for self-modelocking operation. In such lasers are generated the so-called dissipative optical solitons. The uncompensated net normal dispersion in long-cavity resonatorsusually leads to very high chirp and, consequently, to a relatively long duration of generated pulses. This thesis presents the results of research Er-doped ultra-long (more than 1 km cavity length) fibre lasers mode-locked based on NPE. The self-mode-locked erbium-based 3.5-km-long all-fiber laser with the 1.7 µJ pulse energy at a wavelength of 1.55 µm was developed as a part of this research. It has resulted in direct generation of short laser pulses with an ultralow repetition rate of 35.1 kHz. The laser cavity has net normal-dispersion and has been fabricated from commercially-available telecom fibers and optical-fiber elements. Its unconventional linear-ring design with compensation for polarization instability ensures high reliability of the self-mode-locking operation, despite the use of a non polarization-maintaining fibers. The single pulse generation regime in all-fibre erbium mode-locking laser based on NPE with a record cavity length of 25 km was demonstrated. Modelocked lasers with such a long cavity have never been studied before. Our result shows a feasibility of stable mode-locked operation even for an ultra-long cavity length. A new design of fibre laser cavity – “y-configuration”, that offers a range of new functionalities for optimization and stabilization of mode-locked lasing regimes was proposed. This novel cavity configuration has been successfully implemented into a long-cavity normal-dispersion self-mode-locked Er-fibre laser. In particular, it features compensation for polarization instability, suppression of ASE, reduction of pulse duration, prevention of in-cavity wave breaking, and stabilization of the lasing wavelength. This laser along with a specially designed double-pass EDFA have allowed us to demonstrate anenvironmentally stable all-fibre laser system able to deliver sub-nanosecond high-energy pulses with low level of ASE noise.
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Alcon, Camas Mercedes. "Applications of ultralong Raman fibre lasers in photonics." Thesis, Aston University, 2011. http://publications.aston.ac.uk/15795/.
Abstract:
This thesis presents a numerical and experimental investigation on applications of ultralong Raman fibre lasers in optical communications, supercontinuum generation and soliton transmission. The research work is divided in four main sections. The first involves the numerical investigation of URFL intra-cavity power and the relative intensity noise transfer evolution along the transmission span. The performance of the URFL is compared with amplification systems of similar complexity. In the case of intracavity power evolution, URFL is compared with a first order Raman amplification system. For the RIN transfer investigation, URFL is compared with a bi-directional dual wavelength pumping system. The RIN transfer function is investigated for several cavity design parameters such as span length, pump distribution and FBG reflectivity. The following section deals with experimental results of URFL cavities. The enhancement of the available spectral bandwidth in the C-band and its spectral flatness are investigated for single and multi-FBGs cavity system. Further work regarding extended URFL cavity in combination with Rayleigh scattering as random distributed feedback produced a laser cavity with dual wavelength outputs independent to each other. The last two sections relate to URFL application in supercontinuum (SC) generation and soliton transmission. URFL becomes an enhancement structure for SC generation. This thesis shows successful experimental results of SC generation using conventional single mode optical fibre and pumped with a continuous wave source. The last section is dedicated to soliton transmission and the study of soliton propagation dynamics. The experimental results of exact soliton transmission over multiple soliton periods using conventional single mode fibre are shown in this thesis. The effect of the input signal, pump distribution, span length and FBGs reflectivity on the soliton propagation dynamics is investigated experimentally and numerically.
30
Wong, Yuk Lun. "Short optical pulses from injection lasers." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293009.
31
Horikis, Theodore. "Soliton radiation in optical fibre." Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251957.
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Richards, Billy Donald Orac. "Tellurite glass mid-infrared (1.9 - 2.1 um) fibre lasers." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.493606.
Abstract:
Tellurite glass has certain material properties which overcome some of the drawbacks of other established fibre laser host glasses such as silica, fluoride and germanate fibre. For this reason, developing fibre lasers using tellurite fibre is of interest for applications such as light detection and ranging (lidar), sensing and medicine.
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Lapointe, Marc-André. "Lasers à fibre de puissance opérés en régime continu." Thesis, Université Laval, 2010. http://www.theses.ulaval.ca/2010/27088/27088.pdf.
Abstract:
Le présent projet de recherche porte sur les lasers à fibre de haute puissance opérés en régime continu. L’objectif premier est la conception et la réalisation d’un laser de 400 W de puissance de sortie utilisant une fibre dopée à l’ytterbium. La grande variété de lasers fabriqués au cours de ces travaux a permis l’étude des effets thermiques, des limitations en puissance et du comportement de la raie spectrale d’émission.
L’étude comprend des simulations numériques caractérisant le comportement des lasers à fibre opérés en régime continu. Différentes configurations de lasers ont été expérimentées à une puissance de signal de 100 W. Les échanges de chaleur dans les fibres à double gaines ont été analysés pour contourner les difficultés engendrées par la grande puissance de ces lasers. Le concept de résistance de contact est amené pour expliquer l’élévation de température des fibres actives. Les travaux ont abouti à la réalisation de lasers monomodes de plus de 350 W de puissance de sortie, et cela, limités uniquement par la disponibilité des pompes. Parce que la photodégradation est la principale difficulté des lasers à fibre de puissance, plusieurs compromis, notamment sur le choix technologique des composants, ont été nécessaires pour atteindre les objectifs de puissance et de qualité de faisceau.
Un outil pour prédire l’élargissement spectral des lasers à fibre de haute puissance a été développé. Il est montré que le mélange à quatre ondes élargit la raie d’émission de ces lasers. L’élargissement du spectre de sortie, selon une fonction de la puissance, a été vérifié expérimentalement dans diverses configurations d’oscillateur.This research project focuses on high power fiber lasers operated in the continuous regime. The main objective is the implementation of a 400-W fiber laser using ytterbium- doped double clad fiber. The wide variety of high power fiber lasers assembled during this work has enabled the study of the thermal effects, the power limitations and the behavior of the output spectrum. The study includes simulations that characterize the behavior of fiber lasers operated in the continuous regime. Different laser configurations were tested at a signal power of 100 W. The heat transfer in double clad fibers was analyzed to circumvent the difficulties caused by the important amount of heat generated by these lasers. The concept of contact resistance is brought in to explain the temperature rise of active fibers. This was necessary for the realization of single-mode fiber lasers with over 350W of output power. The output power was only limited by the availability of pumps. Several compromises were necessary to achieve the high output power and the diffraction-limited beam quality. Thus, the photodarkening of the ytterbium doped fiber is still an issue for this kind of lasers. A tool to predict the spectral broadening of high power fiber lasers has been developed. It is shown that four-wave mixing broadens the outpu t spectrum of these lasers as a function of output power. The broadening of the output spectrum has been experimentally verified by the implementation of various lasers with different configurations. A theoretical model is presented, which shows a good agreement with experimental data.
34
O, Cochlain Ciaran R. "Tunable erbium doped fibre lasers for lightwave communication systems." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283935.
35
Runcorn, Timothy. "Extending the wavelength coverage of frequency-doubled fibre lasers." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/61332.
Abstract:
The unique coherence properties of laser light has revolutionised modern life through fields as diverse as materials processing, optical communications and scientific research. Despite the enormous engineering progress made in developing laser systems into tools used in a wide range of applications, there are still many spectral regions where suitable laser sources are demanded. This thesis describes progress made towards developing practical and efficient nonlinear frequency conversion techniques to access some of these spectral regions, whilst exploiting the inherent benefits that master oscillator power fibre amplifier (MOPFA) systems offer. In particular, two of the developed sources were designed to satisfy the depletion beam requirements for stimulated emission depletion microscopy using the green fluorescent protein. The sources operated at 560 nm and were based on a frequency-doubled Raman amplifier that was pulse-pumped by an ytterbium MOPFA system. The first source developed proved that this architecture was effective at generating picosecond pulse trains at megahertz repetition rates with nanojoule pulse energy in a compact and alignment-free system. The second source improved on the design by adding temporal flexibility, increasing the efficiency and pulse energy and demonstrated that it was a completely turn-key solution. The third source extended the frequency-doubled pulse-pumped Raman amplifier concept to operation around 590 nm by utilising cascaded Raman amplification, whilst maintaining similar output characteristics. The final source developed operated around 780 nm and was based on direct frequency-doubling of an erbium MOPFA system. It was designed for subsequent nonlinear frequency conversion and featured high average power with flexible wavelength and temporal characteristics. Watt-level average powers and pulse energies of hundreds of nanojoules were obtained at every wavelength region, demonstrating that the implemented nonlinear frequency conversion techniques are a viable method for extending the wavelength coverage of MOPFA systems.
36
Kbashi, Hani. "Vector optical rogue waves in mode-locked fibre lasers." Thesis, Aston University, 2018. http://publications.aston.ac.uk/37771/.
Abstract:
The project consists of an experimental characterisation of optical vector rogue wave (RW) events by using three different testbed fibre laser setups. The first testbed is a long cavity fibre laser (615 m). Here, we have demonstrated for the first time, a new type of vector resonance multimode instability that inherits some features of modulation and multimode instability. This instability leads to emerging different pulse laser regimes from longitudinal modes synchronization to different types of optical RW events. Using the same testbed fibre laser, we have also shown experimentally for the first time fibre twist-based chiral symmetry breaking. This leads to versatile laser dynamics tuneable from a periodic pulse similar mode-locked regime to chaotic oscillations which are revealed as a mechanism for the emergence of RW events. The observed optical RW events have been classified as fast optical RWs or slow optical RWs depending on the autocorrelation function of the experimental data. The classified optical RWs have been studied by collecting experimental data of a 19x19 grid of polarization positions through tuning both intra-cavity and pump polarization controllers. The second testbed is a passively mode-locked fibre laser. Using this system, the control, appearance and disappearance of the soliton rain flow were demonstrated for the first time using a low range of pump power. Harmonics soliton rain, soliton fission and soliton-soliton interactions leading to the emergence of optical RWs have also been demonstrated in this experiment at a different pump power and intra-cavity birefringence. High harmonic (902 MHz) mode-locked fibre laser based on acoustic-optic effect has been realized in the same laser experiment. In the third laser testbed experiment with, a stretched mode-locked fibre laser, vector bright-dark optical RWs were observed experimentally for the first time. These bright-dark RWs have formed in the laser cavity due to modulation instability at close pump power threshold or due to the polarization instability (incoherent coupling) at higher pump power.
37
Hideur, Ammar. "Etude et réalisation de lasers à fibre de puissance." Rouen, 2001. http://www.theses.fr/2001ROUES043.
Abstract:
Ce travail est consacré à l'étude d'un laser à fibre double gaine dopée à l'ytterbium, pompé transversalement à travers une encoche, dans différents régimes de fonctionnement autour de 1. 06 mm. Sont d'abord présentés les lasers à fibre de puissance incluant les nouvelles structures des fibres double gaine ainsi que les techniques de pompage par diode. Puis une étude détaillée du fonctionnement du laser à fibre double gaine dopée à l'ytterbium dans différentes configurations optiques est présentée. Différents régimes impulsionnels résultants des effets non-linéaires dans la fibre ont été identifiés. L'influence des pertes de la cavité ainsi que la puissance de pompage est également étudiée. Nous montrons que le laser est efficacement stabilisé en utilisant une cavité en anneau unidirectionnelle où la diffusion Brillouin contra-propagative est supprimée. L'utilisation d'une telle configuration nous a permis de concrétiser une source laser avec une intensité continue délivrant une puissance de 800mW et accordable dans la gamme 1. 04-1. 1 mm. La largeur de la raie laser est d'environ 0. 1 nm. La troisième partie porte sur l'étude et la réalisation d'une source laser à fibre dopée à l'ytterbium à verrouillage de modes passif par rotation non-linéaire de la polarisation. Nous avons étudié les différents régimes de fonctionnement du laser en cavité en anneau unidirectionnelle contenant un isolateur optique inséré entre deux lames de phase demi-onde. Nous montrons, qu'en fonction de l'orientation respective des deux lames de phase, le laser peut fonctionner en régime continu, en régime à verrouillage de modes ou en régime déclenchéThis work deals with the study of an ytterbium-doped double-clad fibre laser side-pumped using the v-groove technique operating in different regimes around 1. 06mm. In the first part, we present the last developments in the field of high-power diode-pumped fibre laser including the double-clad structures and the pumping techniques. In the second part we investigate experimentally the dynamics of a high power ytterbium-doped double-clad fibre laser in various optical configurations. Different self-pulsing regimes are identified resulting from third-order non-linear effects. The third part is devoted to the study and the realisation of a passively mode-locked ytterbium-doped fibre laser using the non-linear polarisation rotation technique
38
Lhermite, Jérôme. "Auto-synchronisation et combinaison cohérente de lasers à fibre." Limoges, 2008. https://aurore.unilim.fr/theses/nxfile/default/71cfaacc-0380-4854-a1a0-1a1586b5ef3b/blobholder:0/2008LIMO4049.pdf.
Abstract:
La montée en puissance dans les lasers ou amplificateurs à fibres unimodales s’accompagne d’effets non linéaires, liés au fort confinement spatio-temporel du champ dans le guide, qui sont souvent préjudiciables à l’amplification. L’objectif de la thèse est d’étudier l’amplification en parallèle dans les fibres optiques et la recombinaison des champs issus de ces différents amplificateurs. Deux architectures ont été étudiées : Une première configuration interférométrique exploite un filtrage du spectre de fréquences temporelles émis par le laser ramifié pour réaliser la sommation cohérente des champs sur la voie commune de l’interféromètre laser. Les régimes de fonctionnement continu, déclenché et à synchronisation de modes ont été étudiés. Une seconde architecture laser réalise par filtrage spatial interne au résonateur un verrouillage des phases de l’ensemble des amplificateurs disposés en parallèle. Les multiples émissions cophasées sont alors combinées en champ lointainPower scaling in single-mode fiber lasers or amplifiers is accompanied with detrimental nonlinear effects, due to the strong spatial confinement of the field inside the optical guide. A key to achieve high powers is laser beam combining. In this thesis, we have investigated two laser architectures performing coherent combining in a passive way. A first interferometric configuration uses an intracavity frequency filter ensuring the coherent summation of the fields amplified in a tree arrangement. The combined beam emerges from the common arm of the laser interferometer. The continuous, Q-switched and mode-locked regimes, were studied. The second laser architecture realizes the phase locking of the parallel amplifiers by an intracavity spatial filter. The multiple cophased emissions are then combined in far field
39
Papachristos, Thalis. "Generation of microwaves using a mode locked fibre ring laser for radio-over-fibre systems." Thesis, University of Kent, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.344148.
40
Davies, D. A. O. "Twin stripe lasers for switching and logic." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333272.
41
Webb, Andrew. "Novel optical fibre fabrication techniques for Yb-doped high-power fibre lasers and sensing applications." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/349228/.
Abstract:
The work presented in this thesis reports on four novel techniques for fabricating speciality silica preforms and optical fibres. The project aims were to conceive new fabrication methods by adapting conventional Modified Chemical Vapour Deposition (MCVD) and optical fibre drawing equipment, and to demonstrate fibre devices for ytterbium (Yb)-doped high-power fibre lasers (HPFL) and optical sensing applications. Firstly, a new in-situ solution doping technique is presented for fabricating actively-doped fibre-preforms of complex design. The fabrication and characterisation of several multilayered rare-earth (RE)-doped fibres suitable for HPFL applications are reported, including an Yb-doped (>18,000ppm, by weight) fibre with a low effective-NA, which incorporates a pedestal refractive index profile and a unique aluminosilcate (Al:Si) inner-cladding. The vapour-phase deposition of RE ions in fibre-preforms has also been demonstrated using a novel chemical-in-crucible process that is intended for use with precursors of low volatility. Modifications to the standard MCVD setup were made which allows the dopant source to be placed within the substrate glassware and in close proximity to the reaction zone. Preforms with dopant concentrations of up to 25,000 ppm (by weight) of Yb3+ ions have been attained using an organometallic precursor, whilst passive Al:Si preforms containing >16mol% of Al have been achieved using gaseous aluminium chloride. A straightforward fabrication technique for producing silica suspended-core holey fibre (SC-HF) is also presented. The drawn fibre exhibits a relatively low optical loss (of 0.3 dB.m-1 at λ = 1550nm), and the high air-filling fraction, which was predicted as ~30% (for a core size of 0.8μm), is believed to the highest reported value at the time the work was undertaken. The sensing capability of SC-HF has been demonstrated by constructing an all-fibre acetylene-filled gas cell. The final experimental chapter describes the first example of a novel flat fibre concept. Extended lengths of low-loss planar glass substrates were produced using MCVD and conventional fibre drawing equipment. In combination with direct UV-writing, multifunctional planar waveguiding devices can be fabricated that are mechanically flexible. The potential of the flat fibre platform for sensing applications is discussed. The reported fabrication techniques have been implemented through the successful demonstration of several fibre devices suitable for Yb-doped HPFLs and optical sensing applications. The developed techniques have future potential in industry and manufacturing, and it is anticipated that the work presented will enable fibres with novel properties and glass compositions to be researched.
42
Gray, John W. D. "The use of loop mirrors and chirped fibre Bragg gratings in actively-modelocked fibre lasers." Thesis, Aston University, 1998. http://publications.aston.ac.uk/7980/.
Abstract:
The development of an all-optical communications infrastructure requires appropriate optical switching devices and supporting hardware. This thesis presents several novel fibre lasers which are useful pulse sources for high speed optical data processing and communications. They share several attributes in common: flexibility, stability and low-jitter output. They all produce short (picosecond) and are suitable as sources for soliton systems. The lasers are all-fibre systems using erbium-doped fibre for gain, and are actively-modelocked using a dual-wavelength nonlinear optical loop mirror (NOLM) as a modulator. Control over the operating wavelength and intra-cavity dispersion is obtained using a chirped in-fibre Bragg grating. Systems operating both at 76MHz and gigahertz frequencies are presented, the latter using a semiconductor laser amplifier to enhance nonlinear action in the loop mirror. A novel dual-wavelength system in which two linear cavities share a common modulator is presented with results which show that the jitter between the two wavelengths is low enough for use in switching experiments with data rates of up to 130Gbit/s.
43
Inci, M. Naci. "Optical coatings for fibre optic sensors." Thesis, Heriot-Watt University, 1992. http://hdl.handle.net/10399/1455.
44
Smith, Richard. "Optical fibre sensors for radioactive environments." Thesis, University of Liverpool, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318305.
45
Crawford, Stephanie. "The Development of a High Power, Broadly Tunable 3 µm Fibre Laser for the Measurement of Optical Fibre Loss." Thesis, The University of Sydney, 2015. http://hdl.handle.net/2123/13989.
Abstract:
Mid-Infrared Photonics has attracted growing interest in recent years due to the presence of many strong characteristic vibrational transitions that are highly resonance with the low-energy photons of the mid-infrared. As such, a plethora of potential applications stand to benefit from the availability of well-understood and robust sources within this wavelength region including spectroscopy, medicine and defence. The region surrounding 3 µm, corresponding to the antisymmetric stretching vibration of O-H as well as a region of high atmospheric transparency, is of particular interest. However, this spectral region is not yet accessible via readily available devices. As such, the development of well understood, versatile, laser sources at 3 µm remains an area of great scientific interest. In this work, a Ho3+, Pr3+ co-doped fluoride fibre laser is presented that produces an output power of 7.2 W generated at a slope efficiency of 29 %. The excitation source was a power scalable Yb3+-pumped 1.150 µm Raman fibre laser which emitted up to 50 W. The emission linewidth of the system was <0.14 nm and the wavelength of the system was observed to tune between 2.825 µm and 2.975 µm, overlapping with the O-H absorption region of many midinfrared transparent glasses. The system then finds use as a tool for the accurate measurement of the background scattering loss and the degree of water incorporation in the rare earth doped core of a range of commercially available double clad ZBLAN fibres. Furthermore, the spectral location of the O-H absorption feature was observed to be dependent on glass composition shifting from 2.872 µm in undoped ZBLAN to 2.896 µm upon co-doping with Ho3+, Pr3+. Additionally, the chalcogenide glass, As2S3, was observed to have an O-H peak location of 2.911 µm.
46
Duval, Simon. "Laser femtoseconde à fibre optique émettant dans l'infrarouge moyen." Doctoral thesis, Université Laval, 2019. http://hdl.handle.net/20.500.11794/37364.
Abstract:
Le développement de lasers émettant dans l’infrarouge moyen, une région spectrale où l’onretrouve les résonances fondamentales de la plupart des molécules sur terre, est certainementl’une des avenues les plus prometteuses en science laser. La démocratisation de ce type delaser est toutefois nécessaire afin d’exploiter leur énorme potentiel applicatif en santé, enenvironnement, en industrie et en recherche. En raison de leur simplicité, leur robustesse, leurfiabilité et leurs performances optiques inégalées, les lasers à base de fibres optiques sont parmiles candidats les mieux adaptés pour réaliser ce virage technologique vers l’infrarouge moyen.Dans le cadre de ce projet de doctorat, le premier laser à fibre optique émettant des impulsionsfemtoseconde dans l’infrarouge moyen a été réalisé. Ce laser à grande valeur ajoutée offredes propriétés temporelles, spectrales et spatiales exceptionnelles qui ouvrent la voie à denombreuses applications en spectroscopie et en interaction laser-matière.La conception, l’optimisation et l’étude théorique du laser femtoseconde émettant à 2.8μm sontprésentées aux chapitres 1 et 2 ainsi qu’à l’annexe B. La génération d’impulsions ultrabrèvesavec ce laser est basée sur la synchronisation modale passive par rotation non linéaire de lapolarisation dans une fibre de verre fluoré dopée à l’erbium. Des impulsions de durée inférieureà 300 fs, dont la puissance crête estimée est supérieure à 20 kW, ont été obtenues à partir decet oscillateur.La deuxième partie de cette thèse (chapitres 3 et 4) présente la conception et l’étude théoriquepar simulations numériques d’un amplificateur à fibre optique externe permettant d’améliorerles performances de l’oscillateur présenté dans les chapitres précédents. Cet amplificateuremployant un seul segment de fibre de verre fluoré dopé à l’erbium permet d’amplifier lesimpulsions à des puissances crêtes de plus de 200 kW. Grâce au processus d’auto décalagespectral du soliton dans cet amplificateur, la longueur d’onde centrale des impulsions amplifiéespeut être accordée de 2.8 à 3.6μm. Ce système laser femtoseconde accordable dans l’infrarougemoyen, qui constitue une avancée majeure, peut être simplifié et amélioré davantage en plusd’être adapté à plusieurs autres transitions laser dans l’infrarouge moyen. Ces travaux ouvrentla voie à l’émergence de nouvelles applications autrefois difficilement réalisables en rechercheet en industrie.The development of lasers emitting in the mid-infrared, a spectral region where the funda-mental resonances of several molecules are found, is one of the most promising avenues in laserscience. However, the democratization of these coherent light sources is required for enablingbreakthrough applications in healthcare, environment, industry and research. Thanks to theirsimplicity, robustness, reliability and their unequaled optical performances, fiber lasers are thecandidates of choice for enabling this technological shift toward the mid-infrared.In this project, the first femtosecond fiber laser emitting in the mid-infrared was realized. Thishigh added-value laser offers exceptionnal temporal, spectral and spatial properties that pavethe way for several applications in spectroscopy and laser-matter interaction.The design, optimization and theoretical study of this femtosecond laser cavity emitting at 2.8μm are presented in chapters 1 and 2 as well as in appendix B. The generation of ultrashortpulses in this laser relies on a mode-locking technique based on nonlinear polarization evolutionof the signal propagating inside an erbium-doped fluoride fiber. Pulses with durations below300 fs and estimated peak powers above 20 kW were directly generated from this oscillator.The second part of this thesis (chapters 3 and 4) presents the design and numerical studyof an external fiber amplifier that significantly improves the performances of the oscillator.This amplifier that uses only one segment of erbium-doped fluorozirconate fiber enables thegeneration of ultrashort pulses with peak powers above 200 kW. Due to the soliton self-frequency shift process occuring inside the amplifier, the central wavelength of the outputpulses can be tuned from 2.8 to 3.6μm. This tunable femtosecond system in the mid-infraredcan be further simplified and improved and can also be adapted to other novel laser transitionsin the mid-infrared. This work paves the way for new applications to emerge both in thescientific and the industrial worlds.
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Thipparapu, Naresh Kumar. "Development of bi-doped fibre amplifiers and lasers & broadband Er-doped multi-element fibre amplifiers." Thesis, University of Southampton, 2018. https://eprints.soton.ac.uk/423478/.
Abstract:
The demand for fibre optic communication is continuously increasing over the years. This is due to the increased accessibility to the World Wide Web using internet of things. The capacity of current fibre optic communication through the single mode fibre is limited by the amplification bandwidth of Er-doped fibres. To increase the capacity of fibre optic communication research community around the world are proposing different approaches. One of them is to use the low loss window (1260-1625nm) of silica optical fibres by developing efficient fibre amplifiers and lasers. Another one is to use novel fibres such as multi-core fibres, multi-mode fibres and multi-element fibres (MEFs) for space division multiplexing in the C-band (1525-1565nm). In this thesis, we developed amplifiers and lasers within the wavelength band from 1150-1625nm using Bi-doped and multi-element Er-doped fibres. Here, we investigated the fabrication of Bi-doped optical fibres in different glass hosts (aluminosilicate and phosphosilicate) using MCVD-solution doping technique. Bi-doped aluminosilicate fibres are used to develop an amplifier with 12dB gain at 1180nm. Bi-doped phosphosilicate fibres are used to develop amplifiers and lasers in the second telecommunication band from 1300-1360nm. An all-fibre Bi-doped phosphosilicate amplifier with a 25dB at gain in a 40nm bandwidth from 1320-1360nm is reported. Also, a Bi-doped fibre laser operating at 1360nm with an output power of 110mW, and a picosecond pulsed mode-locked fibre laser operating at 1340nm with a peak power of 1.15W, are demonstrated. These amplifiers and lasers have important applications in medicine, astronomy and optical fibre communication. In addition, we also discussed the novel fibres known as MEFs and developed core and cladding pumped broadband amplifiers covering 1500-1620nm using multi-element Er and Er/Yb-doped fires, respectively.
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Dalloz, Nicolas. "Formation du spectre optique dans les lasers Raman à fibre." Phd thesis, Université des Sciences et Technologie de Lille - Lille I, 2011. http://tel.archives-ouvertes.fr/tel-00628627.
Abstract:
Le travail présenté dans ce mémoire s'inscrit dans la problématique générale de la formation du spectre optique dans les lasers Raman à fibre. Nous avons mené une étude expérimentale sur un laser Raman à fibre oscillant dans une cavité Pérot-Fabry fermée par des miroirs de Bragg. Cette étude montre que la forme du spectre optique diffère selon la puissance du laser. En développant différents modèles, nous avons montré que les miroirs de Bragg sont à l'origine de ce changement de forme du spectre optique. En particulier, à faible puissance, la forme asymétrique du spectre provient d'effets dispersifs lors de la réflexion sur les miroirs de Bragg. A forte puissance, ces effets dispersifs sont dominés par les effets de filtrage des miroirs, ce qui conduit à la symétrisation du spectre du laser observée dans notre expérience. Par ailleurs, nous avons également étudié numériquement la statistique du champ Stokes intracavité. Nous avons montré que celle-ci change fortement selon que l'onde Stokes est incidente ou réfléchie par les miroirs de Bragg. Ce résultat nous a permis de questionner la validité d'un modèle récemment publié sur la formation du spectre optique du laser Raman à fibre. Ce modèle s'appuie sur les outils de la théorie cinétique des ondes, valable uniquement dans le cas de champs possédant une statistique gaussienne. Toutefois, notre étude numérique indique que cette condition n'est pas respectée dans le laser Raman à fibre, et la forme du spectre optique observé dans notre étude expérimentale s'oppose fortement à celle prédite par cette approche statistique de la formation du spectre optique du laser Raman à fibre.
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Brunet, François. "Lasers à fibre de verre fluoré pompés par transitions multiples." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0023/MQ51119.pdf.
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Forster, Richard John. "Development and applications of single frequency erbium doped fibre lasers." Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248516.