No description available.

L'étude concerne les lasers de puissance à semi-conducteurs émettant aux alentours de 1480nm dont l'utilisation principale est l'amplification Raman dans les fibres optiques pour les futurs systèmes de télécommunications. Cette amplification nécessite des puissances de pompe supérieures à 400mW. Les travaux ont porté sur la conception et la caractérisation des lasers de pompe en vue d'une augmentation de la puissance de sortie. Après avoir identifier les principaux effets limitant la puissance des pompes (effets thermiques, Longitudinal Spatial Hole Burning, pertes internes), trois solutions ont été mises en œuvre au cours de cette thèse pour réduire ces effets. Nous avons montré que l'introduction de guide large multimode (MMI) permettait à la fois une réduction des effets thermiques et une augmentation de la puissance de saturation de l'ordre de 10% en comparaison au laser à ruban droit. La cavité évasée a permis une réduction du Longitudinal Spatial Hole Burning entraînant un gain en puissance de saturation de l'ordre de 30% avec une puissance de 625mW pour un courant de 2.5A. Enfin, la diminution des pertes internes via l'utilisation d'un quaternaire faible indice coté InP dopé n (structure à "cladding asymétrique") a permis l'obtention d'un record de puissance (1 Watt couplé sous 5A) dans une fibre monomode avec un guide à ruban droit.

This work is concerned with the modeling and analysis of lossy planar dielectric optical waveguides. Loss mechanisms which affect propagation characteristics are reviewed, and various representations of the propagation constant in the lossy case are defined. Waveguide structures which are susceptable to absorption and/or to leakage loss, in particular silicon-based structures, are discussed. The modeling and analysis of these waveguides by various computational techniques is considered. Two computational methods, the commonly used transfer matrix method and the recently developed impedance boundary method of moments (IBMOM), are reviewed and extended to the complex domain. A third computational method, which offers improved convergence of the IBMOM for structures with large stepwise changes in refractive index, is formulated. In this approach, the regions containing refractive index discontinuities are replaced by equivalent extended impedance boundary conditions, and expansion of the transverse field in the remaining region of continuous refractive index profile is carried out. A significant increase in the rate of convergence is demonstrated for various waveguide structures, including an anti-resonant reflecting optical waveguide (ARROW) structure. Two applications of the IBMOM with extended impedance boundary conditions are presented. In the first, the method is applied to the design of a chemical sensor. The sensor, a silicon-based ARROW structure, is designed to measure the refractive index of certain chemical substances with a high degree of accuracy. In a second application, graded index SiON waveguides fabricated at Oregon State University are characterized and compared to the theoretical model. Excellent agreement between the theoretical and measured coupling angles is shown. / Graduation date: 1996

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 197-200).

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Thesis (M.S.)--Rochester Institute of Technology, 2006. / Typescript. Includes bibliographical references (leaves 171-181).

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This dissertation presents the research on a novel combination of well proven concepts for passive electromagnetic wave-guiding components. The goal of this work is to overcome and minimize losses occurring in frequency-selective structures. The work aims to contribute to an improvement in the application of conventional and Substrate Integrated Waveguide (SIW). It is proposed to mount conventional waveguide structures on the surface of printed circuit boards containing substrate integrated waveguides. The crossover technology is referred to as Surface Mounted Waveguide (SMW). Theoretical investigations are performed, proving the validity and superiority of the proposed structure focusing on the elimination of losses, while maintaining low space consumption and printed circuit board technology compatible manufacturing processes. Additionally, a mode matching technique is developed and successfully applied to prototype such components. The validation of this method reveals superior computational speed when compared to commercial available electromagnetic field solvers. The proposed structures are validated by measurements of several prototypes, including coupled SMW resonator filters, combined SMW and SIW resonator filters, a SMW triple-layer diplexer and single individual SMW resonator filters. The experimental verification shows good agreement between theory and measurements. Moreover, the comparison to other technologies proves the superiority of the proposed structures. / Graduate

Tour guides are one of the most visible players in tourism but little scholarly attention has been given to the links that tour guides may have with sustainable development. This study addresses the gap by promoting an understanding of how tour guides can assist in moving tourism in a sustainable direction. Sustainable development is expected to improve the quality of life for all people without causing undesirable ecological and socio-cultural outcomes. As a central agent in the entire tourism system, tour guides have a variety of roles to play in response to the expectations of the various tourism stakeholders. A literature review suggests that tour guides can contribute to destinations'sustainable development by exerting their functions on experience management, resources management and local economic promotion. Interpretative guiding is the means by which tour guides can realize these above potentials. A case study was conducted in Hainan, China. The guiding performance there was examined to see whether and to what extent tour guides are contributing to the achievement of local sustainability. It was discovered that the tour guides in Hainan do not exert (well) their expected functions either in enhancing enjoyable experiences for tourists, in supporting local resource conservation, or in promoting the healthy development of the local economy. Their potentials are blocked by the issues and problems of instant money-making-centered guiding conduct, below-cost group receiving industry practices and unfair remuneration system for the guides, absence of protection measures to ensure the guides??? interests, opportunism in guiding and lenient certificating requirements, lack of professionalism and effective training, ineffective monitoring measures, and limited awareness of sustainable development. In order to better the situation, unhealthy travel and trade industry practice should be banned; effective certificating, training and monitoring measures should be developed and implemented; tour guides??? personal interests should be protected and local awareness of sustainability, in particular that of the industry members, should be fostered. Serious efforts of the government administration as well as industry members and tour guides are required if tour guides are to fulfill their potential as agents of sustainable development.

by Hung Wing-yiu. / Thesis (M.Ph.)--Chinese University of Hong Kong, 1988. / Bibliography: leaves 98-103.