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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Birefringent Liquid-Filled Photonic Crystal Fiber

Chiang, Chih-Lun 18 July 2011 (has links)
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.
2

Lumière lente par amplification paramétrique dans les fibres optiques biréfringentes / Slow light by parametric amplification in birefringent optical fibers

Nasser, Nour 06 June 2013 (has links)
Cette thèse a pour thème le processus physique de ralentissement de la lumière induit par amplification paramétrique vectorielle dans les fibres optiques biréfringentes. Notre première étude porte sur la lumière lente induite par amplification paramétrique vectorielle dans les fibres fortement biréfringentes. Contrairement au processus scalaire, nous montrons théoriquement que le processus vectoriel offre la possibilité de créer des bandes de gain paramétrique étroites et éloignées de la pompe, permettant de générer des retards optiques très importants, un ordre de grandeur supérieurs à ceux obtenus en amplification paramétrique scalaire. Des résultats analytiques et issus de simulations numériques dans le cas de dispersion normale ainsi que dans le cas de dispersion anormale sont présentés. Ensuite, nous discutons des principales limitations au retard optique (élargissement de l’impulsion pompe notamment) et nous étudions l’influence positive de l’effet Raman sur le retard optique. Notre seconde étude est consacrée à la lumière lente induite par amplification paramétrique dans les fibres faiblement biréfringentes. Nous traitons l’ensemble des configurations possibles d’instabilité de polarisation selon l’état initial de polarisation de l’impulsion pompe et du régime de dispersion. Nous démontrons clairement que la configuration correspondant à une impulsion pompe polarisée suivant l’axe lent de la fibre et une impulsion signal polarisée suivant l’axe rapide en régime de dispersion normale donne des retards optiques les plus important / This thesis aims to the physical process of slow light induced by vector parametric amplification in highly and weakly birefringent optical fibers. Our first study concerns slow light induced by parametric amplification in highly birefringent fibers. Unlike the scalar process, we theoretically demonstrate that large optical delays can be in principle generated in birefringent fibers, one order of magnitude higher than for the scalar case. Both analytical and numerical results in the case of anomalous dispersion are presented. We further discuss the main limitations for slow light optical delays (signal pulse broadening, pump pulse depletion). The influence of the Raman gain is also studied both analytically and numerically. The second study focuses on slow light induced by parametric amplification in weakly birefringent fibers. We consider all possible configurations of polarization modulation instability, depending on the polarization axis of the pump pulse and on the dispersion regime, and we derive the slow-light optical delays. We clearly demonstrate that the configuration corresponding to a pump pulse polarized in the slow axis of the fiber and a signal pulse polarized on the fast axis, in the normal dispersion regime, gives the largest optical delays.

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