Thesis (Ph. D.)--Lehigh University, 2004. / Includes bibliographical references and vita.

Orientador: Aldario Chrestani Bordonalli / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-12T12:54:47Z (GMT). No. of bitstreams: 1 Silva_Reginaldoda_M.pdf: 5147387 bytes, checksum: 92c87077ec69edec6939f972e198910e (MD5) Previous issue date: 2008 / Resumo: Com o atual e constante crescimento das taxas de transmissões em comunicações ópticas, a busca por novos materiais com aplicações em amplificadores ópticos tem servido de fonte de constantes pesquisas. Motivado por essa necessidade, este trabalho apresenta os resultados alcançados para uma análise experimental das características de amplificação de fibras ópticas feitas com vidro telurito dopado com érbio e sem a utilização do túlio (Tm) como co-dopante, produzidas no IFGW/ UNICAMP. Os procedimentos adotados para as medições de dois tipos de fibra (perfil de índice degrau e microestruturada) são descritos para diferentes configurações de aplicação de bombeio. Quando comparadas às fibras de sílica dopadas com érbio, estas fibras apresentaram banda disponível para amplificação, aproximadamente, duas vezes mais ampla (~90 nm). Medindo-se as variações no nível de potência óptica de um sinal antes e depois da aplicação de bombeio, pode-se alcançar um aumento de potência de saída de até 15 dB, sugerindo propriedades de amplificação óptica, no entanto não se obteve ganho real no sistema. Este valor máximo foi obtido para amostras de 10 cm e 5 cm de fibra de perfil de índice degrau e microestruturada, respectivamente. A fragilidade da fibra dificultou o seu manuseio e impossibilitou sua conectorização, de maneira que os resultados alcançados podem, potencialmente, ser melhorados se as grandes perdas no processo de acoplamento da luz entre os diferentes materiais vítreos forem minimizadas. / Abstract: The continuous growth of the optical communication transmission rate has stimulated the search for new materials that can be applied to the manufacturing of optical amplifiers. Motivated by this, the results for an experimental analysis of the amplification characteristics of erbium doped tellurite fibers (EDTFs) without thulium co-doping are presented. The measurement procedures for two distinct fiber structures (step index and microstructured) fabricated at the IFGW/UNICAMP labs were described for different pump coupling configurations. In comparison with erbium-doped silica fibers, the EDTF shows an available optical amplification bandwidth twice as broader (~90 nm). By measuring the optical power variations of a signal before and after pumping application, an optical output power increase as high as 15dB was possible, suggesting optical amplification properties. This maximum value was achieved for 10-cm long step index fiber and 5-cm long microstructured fiber samples. The fiber sample mechanical fragility has made difficult its manipulation and prevented its connectorization in such a way that improvement in the measured results could be attained if the high losses during light coupling among different glass materials were minimized. / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

No description available.

Thèse de doctorat : Physique et Chimie de la Matière et des matériaux : Nancy 1 : 2007. / Titre provenant de l'écran-titre. Bibliogr.

No description available.

Konstanz, Univ., Diss., 2007. / Ersch. auch im Verlag Hartung-Gorre, Konstanz.

Hannover, Universiẗat, Diss., 2004.

Spontaneous atomic emission is not a process of the isolated atom but rather a cooperative effect of the atom and the vacuum field. It is now well established that spontaneous radiative decay rates can be enhanced or suppressed through the effect of cavities comprising various types of discrete, reflective-mirror type, boundaries. The cavity effect is generally understood in terms of a cavity-induced modification of the vacuum spectral energy density. Recently, interest has grown in the possibility that systems characterized by distributed periodic boundary conditions, such as a spatially varying index of refraction, might be effective in controlling radiative atomic processes. A semi-classical theory is given that enables an estimate of the size of the lifetime modification of a two-level radiator contained within a three-dimensionally incomplete photonic bandgap structure called a fiber-Bragg grating. Following this is an exploration of a specific system and its effect upon radiative spontaneous emission. It is found through fluorescence line narrowing and frequency hole burning measurements that the observation of lifetime modification of the specific system is complicated due to intra and inter Stark energy migration. A lifetime modification measurement then shows that no change in lifetime is observed beyond the error bars on the measurement results. The tuning and coherence properties of a short-external-cavity diode laser that may be useful for future time-dependent spectroscopic measurements are examined using a fiber-based, self-heterodyne technique. Coherence properties during active frequency scans are characterized through analysis of time-dependent heterodyne beat signals at the output of a fiber interferometer.

No description available.

The erbium-based optical amplifier (EDFA) plays a vital role in the global fibre-optic telecommunication network. However, there are two main issues with current EDFAs, their bulky size means that they cannot be integrated into silicon-based photonic devices, and they need high pump power to produce optical gain. Here, a potential organo-erbium gain system has been invented, which could be operated under a low pump power and integrated onto a silicon-based device. The fully-fluorinated organic erbium complex [Er(ftpip)3] was mixed with a fully-fluorinated organic zinc complex [Zn(F-BTZ)2], acting as a chromophore over the visible range. The composite provides extraordinary sensitisation from the Zn(F-BTZ)2 to Er(ftpip)3 over a broad-visible band, which is compatible with high power LEDs, whilst the erbium ions have a new record of IR emission lifetime of ~ 0.8 ms (quantum yield = ~ 7%). The integrated sensitisation is ~ 104 times that of the intrinsic excitation into erbium. This system has been integrated into an organic light emitting diodes (OLEDs) demonstrating that the energy transfer is dominated by triplet states of the Zn(F-BTZ)2. This is used for explaining the photoluminescence saturation and large pump-rate, with the composite being excited by a low power diode laser on the chromophore units. This composite-system was used to fabricate a slab waveguide, in which an relative gain of 3.4 dB/cm was achieved when excited by a diode laser with 3 mW. A microscopic-optic setup was designed to measure IR line strengths of erbium ions in crystals of complexes, which were included in theoretical calculation to obtain accurate quantum yield for IR emission of erbium ions. The inclusion of IR line strengths measured from crystals is found to be crucial for Judd-Ofelt parameterisation on organic erbium complexes. It was demonstrated that fluorination could increase the line strengths of hypersensitive transitions and IR transition for 1.5 μm band.