The thulium fiber laser has gained interest due to its long emission wavelength, large bandwidth (~1.8 – 2.1 µm), high efficiencies (~60 %), and high output power levels both in cw as well as pulsed regimes. Applications like remote sensing, machining, medical tissue ablation, and mid-infrared generation benefit from high peak power thulium laser sources. Pulsed thulium fiber laser systems are advancing rapidly towards higher peak power levels and are becoming the preferred sources for these applications. This dissertation work describes the development of novel nanosecond pulsed thulium fiber laser systems with record high peak power levels targeting mid-infrared generation. The peak power scaling in thulium fiber lasers requires new fiber designs with larger mode field area (MFA) than commercially available step index large mode area (SI-LMA) fibers. Two different prototypes of thulium doped photonic crystal fibers (PCF) were investigated for high peak power generation. The first prototype is a flexible-PCF with MFA twice as large as SILMA fiber and the second prototype is a PCF-rod with six times larger MFA. A robust single stage master oscillator power amplifier (MOPA) source based on flexible-PCF was developed. This source provided narrow linewidth, tunable wavelength, variable pulse duration, high peak power, and high energy nanosecond pulses. The PCF-rod was implemented as a second stage power amplifier. This system generated a record level of ~1 MW peak power output with 6.4 ns pulse-duration at 1 kHz repetition rate. This thulium doped PCF based MOPA system is a state of the art laser source providing high quality nanosecond pulses. iv The single stage MOPA system was successfully implemented to pump a zinc germanium phosphide (ZGP) crystal in an optical parametric oscillator (OPO) cavity to generate 3 - 5 µm wavelengths. The MOPA source was also used to demonstrate backside machining in silicon wafer. The PCF based laser system demonstrated an order of magnitude increase in the peak power achievable in nanosecond thulium doped fiber laser systems, and further scaling appears possible. The increase in peak power will enable additional capabilities for mid-infrared generation and associated applications.

We develop a theory of higher-order exact real number computation based on Scott domain theory. Our main object of investigation is a higher-order functional programming language, Real PCF, which is an extension of PCF with a data type for real numbers and constants for primitive real functions. Real PCF has both operational and denotational semantics, related by a computational adequacy property. In the standard interpretation of Real PCF, types are interpreted as continuous Scott domains. We refer to the domains in the universe of discourse of Real PCF induced by the standard interpretation of types as the real numbers type hierarchy. Sequences are functions defined on natural numbers, and predicates are truth-valued functions. Thus, in the real numbers types hierarchy we have real numbers, functions between real numbers, predicates defined on real numbers, sequences of real numbers, sequences of sequences of real numbers, sequences of functions, functionals mapping sequences to numbers (such as limiting operators), functionals mapping functions to numbers (such as integration and supremum operators), functionals mapping predicates to truth-values (such as existential and universal quantification operators), and so on. As it is well-known, the notion of computability on a domain depends on the choice of an effective presentation. We say that an effective presentation of the real numbers type hierarchy is sound if all Real PCF definable elements and functions are computable with respect to it. The idea is that Real PCF has an effective operational semantics, and therefore the definable elements and functions should be regarded as concretely computable. We then show that there is a unique sound effective presentation of the real numbers type hierarchy, up to equivalence with respect to the induced notion of computability. We can thus say that there is an absolute notion of computability for the real numbers type hierarchy. All computable elements and all computable first-order functions in the real numbers type hierarchy are Real PCF definable. However, as it is the case for PCF, some higher-order computable functions, including an existential quantifier, fail to be definable. If a constant for the existential quantifier (or, equivalently, a computable supremum operator) is added, the computational adequacy property remains true, and Real PCF becomes a computationally complete programming language, in the sense that all computable functions of all orders become definable. We introduce induction principles and recursion schemes for the real numbers domain, which are formally similar to the so-called Peano axioms for natural numbers. These principles and schemes abstractly characterize the real numbers domain up to isomorphism, in the same way as the so-called Peano axioms for natural numbers characterize the natural numbers. On the practical side, they allow us to derive recursive definitions of real functions, which immediately give rise to correct Real PCF programs (by an application of computational adequacy). Also, these principles form the core of the proof of absoluteness of the standard effective presentation of the real numbers type hierarchy, and of the proof of computational completeness of Real PCF. Finally, results on integration in Real PCF consisting of joint work with Abbas Edalat are included.

This thesis describes developments in atomic vapour loading in hollow core photonic crystal fibre (HC-PCF) for fabrication of atomic vapour loaded photonic microcells (PMC). These developments have been targeted at addressing some of the issues associated with loading atomic vapours in confined waveguiding geometries such as increased dephasing and physio-chemical wall absorptions. Atomic vapour loaded HC-PCF and PMC’s have applications in laser metrology, coherent optics and magneto optical spectroscopy. State of the art HC-PCF have been fabricated for loading with atomic vapour including both photonic bandgap (PBG) guiding and inhibited coupling (IC) hypocycloidal core shape Kagome HC-PCF. Record loss of 70 dB/km has been achieved in IC hypocycloid core shape Kagome HC-PCF in the spectral region centred at 800 nm. This fibre retains excellent single mode propagation combined with large core and increased optical bandwidth in comparison with specialist PBG HC-PCF optimised for operation around 800 nm. Aluminosilicate sol-gel coatings have been developed and successfully applied to the inner core wall of HC-PCF’s to reduce the atomic vapour surface interaction. Confining atomic vapours in micron scaled HC-PCF results in increased dephasing rates because of the frequent atom wall collisions. Anti relaxation coating materials have been applied to the inner core wall and the longitudinal relaxation time has been measured in coated and uncoated fibres utilising a magneto optical technique. Additionally sub Doppler transparencies are investigated in anti relaxation coated and uncoated HC-PCF.

In a wireless network, the medium is a shared resource. The nodes in the network negotiate access of the shared resource using the Medium Access Control (MAC) protocol. The design of a MAC protocol for a sensor node is not the same as that for a wireless transceiver. Due to the transceiver characteristics, the MAC protocol design is limited in terms of medium access methods. However, in most cases, the protocols rely on simple access methods i.e. Time Division Multiple Access (TDMA) or Carrier Sense Multiple Access / Collision Avoidance (CSMA / CA). Control and monitoring applications, running over a wireless network, are typical examples of Wireless Sensor Actuator Network (WSAN) application in industries. In an industrial network, the message deliveries must be time-bounded otherwise, they are of no use. This report aims to present the thesis work carried out at ABB AB, Västerås. The purpose of this thesis was to compare the performance of WLAN and WirelessHART when it comes to control applications. For the purpose of WLAN, the media access schemes are analyzed in terms of deadline misses. There are other metrices for the performance evaluation but our focus was on the latency, since it is very important in the field of industrial automation. NS-2 was used for the purpose of MAC layer analysis and it is also shown that PCF gives better performance as compared to DCF, in terms of deadline misses. Finally, WLAN is proven to accommodate more control loops as compared to WirelessHART for a given scenario.

In the field of optical fiber sensors, one of the most versatile structures is the Fabry-Perot interferometer. This thesis will present a novel sensor based on an Intrisnic Fabry-Perot Inferferometer (IFPI) cavity to measure axial acceleration, refractive index, and temperature. The sensor structure is based on previous work done by R. Wang at the Center for Photonics Technology. This work suggests its flexibility in many different roles with a sensitivity to axial acceleration of 70 pm/unit of acceleration, to refractive index of 60 nm/Refractive Index Unit, and to temperature of 7.8 pm/°C. Future work is also discussed in measuring tangential acceleration with direction using a PM fiber as the lead-in and observing the reflections on the slow and fast axes. / Master of Science

Birefringent fibers have attracted considerable attention in recent years for their potential applications in communication and sensing. In this thesis we selectively infiltrate high-index liquids or liquid crystals (LCs) into specified air holes of the photonic crystal fibers (PCFs) by using a selective blocking technique and the vacuum filling method to form half-filled birefringent PCFs and central-filled liquid crystal PCF (LCPCF). We first measure the bending loss of the half-filled PCF. Smaller bending loss was obtained as the PCF was bent in 0¢X due to the dominat index-guiding. Compared with the full-filled PCF, the half-filled PCF possesses a smaller bending loss for the reduction of liquid-filled air holes. The birefringent properties of the half-filled PCF and the LCPCF were then measured in cooperation with the Sagnac fiber loop. We can obtain the birefringence of the half-filled PCF of 2.39¡Ñ10^-4 at £f = 1411 nm, and the sensitivity to temperature, strain, and torsion can be obtained as -0.614 nm/¢XC, 0.466 pm/£g£`, and -0.316 nm/deg. These large sensitivities make the half-filled PCF useful in sensing applications. We also measured the birefringence of the central-filled LCPCF with variant laser irradiation and temperature. The optical and thermal birefringence variations from 2.8¡Ñ10^-3 to 4.12¡Ñ10^-3 and from 2.3¡Ñ10^-3 to 3.3¡Ñ10^-3 can be oberserved, respectively. The optically and thermally tunable birefringence of the central-filled LCPCF was experimentally demonstrated.

No description available.

In this dissertation, we propose numerical techniques to explain physical phenomenon of nonlinear photonic crystal fiber (PCF). We explain novel physical effects occurred in PCF subjected to very short duration pulses including soliton. To overcome the limitations in the analytical formulation for PCF, an accurate and efficient numerical analysis is required to explain both linear and nonlinear physical characteristics. A vector finite element based model was developed to precisely synthesize the guided modes in order to evaluate coupling coefficients, nonlinear coefficient and higher order dispersions of PCFs. This finite element model (FEM) is capable of evaluating coupling length of directional coupler implemented in dual core PCF, which was supported by existing experimental results. We used the parameters extracted from FEM in higher order coupled nonlinear Schrödinger equation (HCNLSE) to model short duration pulses including soliton propagation through the PCF. Split-step Fourier Method (SSFM) was used to solve HCNLSE. Recently, reported experimental work reveals that the dual core PCF behaves like a nonlinear switch and also it initiates continuum generation which could be used as a broadband source for wavelength division multiplexing (WDM). These physical effects could not be explained by the existing analytical formulae such as the one used for the regular fiber. In PCF the electromagnetic wave encounters periodic changes of material that demand a numerical solution in both linear and nonlinear domain for better accuracy. Our numerical approach is capable of explaining switching and some of the spectral features found in the experiment with much higher degree of design freedom. Numerical results can also be used to further guide experiments and theoretical modeling.

La place de la violence dans l'histoire du XX° siècle est l'objet de nombreuses études depuis la publication des ouvrages de l'historien américain George L. Mosse. Si cet intérêt s'est longtemps concentré sur l'étude des mouvements d'extrême-droite, depuis une décennie la recherche historique se penche sur l'étude des relations qu'entretient le communisme, avec la violence. C'est dans cet environnement historiographique que notre étude vise à éclairer la place tenue par la violence dans la vie du PCF de sa naissance, en 1920, à son interdiction en septembre 1939. Dans un premier temps, après avoir analysé la place de la violence dans le mouvement socialiste et ouvrier avant 1914, il s'agit de percevoir la nouveauté introduite par l'idéologie bolchevique dans cette relation au moment où la société française est confrontée à la Grande Guerre et ses séquelles et de déterminer le rôle de la violence dans la naissance du PCF et dans son développement jusqu'à la fin des années 1920. Nous analysons ensuite la période « classe contre classe » où le PC développe pleinement les potentialités contenues dans la culture de guerre civile qu'il cultive depuis sa naissance. Il essaye alors d'inscrire cette guerre civile dans la réalité française. Le discours qui s'appuie sur la simplification de la perception des réalités politiques, économiques et sociales, décryptée au prisme de la culture de la guerre civile se durcit pour marquer l'imminence de la parousie révolutionnaire. Le PCF prône alors la confrontation directe avec les forces de l'ordre dans le but de conquérir la rue tout en essayant de mettre sur pied une force paramilitaire. L'abandon de l'activisme violent à la fin de 1931 entraîne une période d'hésitation sur la place de la violence dans la stratégie communiste, hésitation qui prend fin à partir de 1934 avec le tournant vers le Front populaire qui fait l'objet de notre troisième et dernière partie. La culture de guerre civile, que porte en lui le communisme, s'intègre alors à la culture républicaine sous le signe de l'antifascisme. Ce processus, qui participe aux succès que connaissent alors les communistes, entraîne une atténuation de la place de la violence dans la politique du PCF, mais non sa disparition. Sa trace se retrouve dans la politique interne de vigilance révolutionnaire, l'usage de la force contre les fascistes et les renégats et le rôle des communistes français sur le front espagnol durant la guerre civile. / The place of violence in history of XX ° century is the object of many studies since the studies of the American historian George L. Mosse. If this interest has concentrated for a long time on the study of the far-right movements, for decade historical research leans over the study of relations communism, with violence. It's in this historiographic environment that our study aims at lighting the place held by violence in the life of PCF since its birth, in 1920 to its ban in September, 1939. At first, having analysed the place of violence in socialist and working movement before 1914 and the novelty introduced by the bolchevik ideology in this relation at the time when the French society is confronted with First World War and its consequences to determine the role of violence in the birth of PCF and in its development during 1920s. We analyse the period «class against class» where the PC develops entirely potentialities contained in the culture of civil war which it cultivates since its birth. He tries to register this civil war in French reality. The speech which leans on the simplification of the perception of political, economic and social realities, having read in prism of the culture of civil war to mark the imminence of the revolutionary parousie. PCF search direct confrontation with police force in the intention of winning the street, while trying to set up a paramilitary force. The end of violent activism at the end of 1931 draws away a period of hesitancy on the place of violence in communist strategy, hesitancy which comes to end from 1934 with turn towards the Popular Front which makes the object of our third and last part. The culture of civil war, that hits in him communism, integrates then with republican culture under the sign of antifascism. This process, which participates in the successes which know then the communists, draws away an alleviation of the place of violence in the policy of PCF, but not its disappearance. Its trace is in the internal policy of revolutionary alertness, the usage of force against the fascists and the renegades and the role of the French communists on the Spanish front during civil war.

The following thesis deals with methods to increase the reliability of the results in life cycle assessment. The paper is divided into two parts. The first part points out the typologies and sources of uncertainty in LCA and summarises the existing methods dealing with it. The methods are critically discussed and pros and cons are contrasted. Within the second part a case study is carried out. This study calculates the carbon footprint of a cosmetic product of Li-iL GmbH. Thereby the whole life cycle of the powder bath Blaue Traube is analysed. To increase the reliability of the result a procedure, derived from the first part, is applied. Recommendations to enhance the product´s sustainability are then given to the decision-makers of the company. Finally the applied procedure for dealing with uncertainty in LCAs is evaluated. The aims of the thesis are to make a contribution to the understanding of uncertainty in life cycle assessment and to deal with it in a more consistent manner. As well, the carbon footprint of the powder bath shall be based on appropriate assumptions and shall consider occurring uncertainties. Basing on discussed problems, a method is introduced to avoid the problematic merging of variability uncertainty and data uncertainty to generate probability distributions. The introduced uncertainty importance analysis allows a consistent differentiation of these types of uncertainty. Furthermore an assessment of the used data of LCA studies is possible. The method is applied at a PCF study of the bath powder Blaue Traube of Li-iL GmbH. Thereby the analysis is carried out over the whole life cycle (cradle-to-grave) as well as cradle-to-gate. The study gives a practical example to the company determining the carbon footprint of products. In addition, it meets the requirements of ISO guidelines of publishing the study and comparing it with other products. Within the PCF study the introduced method allows a differentiation of variability uncertainty and knowledge uncertainty. The included uncertainty importance analysis supports the assessment of each aggregated unit process within the analysed product system. Finally this analysis can provide a basis to collect additional, more reliable or uncertain data for critical processes.