Thesis (M. Eng.)--Carleton University, 1988. / Also available in electronic format on the Internet.

Thesis (Ph. D.)--Carleton University, 1999. / Also available in electronic format on the Internet.

Thesis (M.S.)--Rochester Institute of Technology, 2006. / Typescript. Includes bibliographical references (leaves 94-97).

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 132-135).

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaf 107). Also available on the World Wide Web.

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 87-95).

Thesis (Ph. D.)--Oregon State University, 2006. / Printout. Includes bibliographical references (leaves 114-119). Also available on the World Wide Web.

[pt] O desenvolvimento de moduladores externos é fundamental já que em decorrência do efeito de chirp em altas freqüências, a modulação direta de lasers fica prejudicada. Nesta tese projetamos uma estrutura de modulador de amplitude utilizando o efeito Stark em semicondutores para ser aplicado em sistemas de telecomunicação de altas taxas. Na estrutura semicondutora proposta utilizou-se a eletro-absorção em poços quânticos múltiplos de OnGaAs/InAlAs. Diferentes figuras de mérito do dispositivo passivo e ativo foram analisadas. Na simulação do comportamento do dispositivo como guia de onda foram utilizados os seguintes métodos: Método do Índice Efetivo e Método de Propagação de Feixe. A aplicabilidade desses métodos foi testada numa estrutura Rib de GaAs/AlGaAs e os resultados confrontados com medidas feitas em laboratório. Estando os resultados experimentais de acordo com os resultados obtidos através da simulação, os mesmos métodos foram utilizados na avaliação da estrutura do modulador de amplitude proposta. O comportamento resultante do guia correspondente às características almejadas. / [en] The development of external modulators is fundamental since the presence of chirping deteriotates the direct modulation of laseres ati high frequencies. In this work a project of an amplitude modulator for high bit-rate telecommunication systems using the Stark effect in semiconductors was undertaken. In the proposed semiconductor structure the electro-absorption in InGaAs/AnAlAs multiple quantum wells was used. Different figures of merit of the passive and active device were analysed. In the simulation of the device performance as a waveguide the following methods were applied: effective Index Method and Beam Propagation Method. The applicability of these methods were tested on a GaAs/AlGaAs rib structure and the results were compared with measurements done in the laboratory. The experimental results were in completed accord with the simulation. Therefore, the same methods were used to evaluate the proposed amplitude modulator structure. The resulting performance of the waveguide corresponds to the desired characteristics.

[pt] Nesta tese estudamos estruturas de poucos quânticos múltiplos (MQW) com dopagens delta de Si dentro dos poços quânticos de GaAs e de C nas barreiras de AlGaAs (nipi). Esta estrutura foi proposta anteriormente por W. Batty e D. W. E. Allsopp como uma alternativa para maximizar o deslocamento Stark e melhorar o desempenho de moduladores de amplitude por eletroabsorção.As amostras foram crescidas pela técnica de MOCVD, utilizando respectivamente como fontes de Si e C, a silana (SiH4)e o tetrabrometo decarbono(CBr4). Em particular,a dopagem de C em AlGaAs foi cuidadosamente estudada uma vez que seu controle é mais difícil de ser obtido. Apesar de pouca flexibilidade nas condições de crescimento, em particular na razão entre os fluxos dos elementos V e III, foi possível controlar o nível de dopagem de C nas camadas de AlGaAs. As estruturas nipi foram estudadas em detalhe para avaliar seu potencial na aplicação em moduladores ópticos. Observamos que o balanço necessário entre os níveis de dopagem n e p não é trivial de ser alcançado devido µ a presença de armadilhas de buracos nas interfaces AlGaAs=GaAs cuja população depende da concentração da dopagem no pouco de GaAs.Medidas de fotoluminescência (PL), reforçadas por cálculos teóricos, mostraram que uma transição espacialmente indireta envolvendo elétrons no pouco quântico de GaAs e buracos na barreira de AlGaAs ocorre, para baixas temperaturas, em energias abaixo do gap do pouco quântico. A temperatura ambiente esta transição não foi observada e a emissão óptica medida ocorre essencialmente na mesma energia observada em uma estrutura equivalente porém, sem dopagem delta. Estes resultados levaram a conclusão de que problemas de perdas por inserção no modulador, decorrentes de absorção por níveis no gap,não ocorrerão uma vez que, a temperatura ambiente, não existem níveis de energia abaixo da transição ao fundamental do pouco quântico. / [en] In this thesis we have studied multiple quantum well structures with Si delta doping inside the GaAs quantum wells and C delta doping in the AlGaAs barriers (nipi). This structure was proposed by W. Batty and D. W. E. Allsopp as an alternativeto maximize the Stark shift and improve the performance of electroabsorption amplitude modulators.The samples were grown by the MOCVD technique, using respectively as Si and C sources, silane (SiH4) and carbon tetrabromide (CBr4). Particularly, the C doping of AlGaAs was carefully studied because of the difficulties in controlling the C incorporation.Despite the little flexibility in the growth conditions, in particular in the V to III fluxes ratio, it was possible to control the C doping level in the AlGaAs layers.The nipi structures were studied in detail to evaluate their potential for use in the fabrication of optical modulators. It has been observed that the required balance between n and p type doping levels is not trivial to be achieved due to the presence of interface hole traps whose population depends on the GaAs quantum well doping concentration.Photoluminescence measurements, supported by calculations, point out that an spatially indirect transition which involves electrons in the GaAs quantum well and holes in the AlGaAs barrier occurs, at low temperatures, at energies below the gap of the quantum well. At room temperature this transition has not been observed and the measured optical emission occurs at essentially the same energy as that of an equivalent undoped structure. These results led to the conclusion that insertion losses problems will not occur due to absorption below the gap since, at room temperature, there are no energy levels below the quantum well fundamental transition energy.

Over the past several years, rapid advances in the field of integrated photonics coupled with nanofabrication capabilities have enabled studies of the interaction of light with the mechanics of a variety of physical structures. Concurrently, mechanical resonators have been extensively studied in the MEMS community due to their high quality factors, and have been implemented in a variety of RF filters and oscillators. The combination of MEMS with integrated optomechanical structures can generate a variety of novel devices that can be used for applications in RF-Photonics, timing and optical switching. While there are several demonstrations of electrostatic devices integrated with optomechanical structures, fewer examples exist in the piezoelectric domain. In particular, photonic integration in a piezoelectric material can benefit from some of the traditional strengths associated with this type of actuation, such as the ability to easily scale to higher frequencies of operation by patterning lateral features, the ability to interface with 50Ω electronics and strong electromechanical coupling. In addition, it enables a platform to produce new architectures for photonic-based electronic frequency reference oscillators that incorporate multiple degrees of freedom. This thesis presents the development of a piezoelectrically-actuated acousto-optic modulator in the aluminum nitride (AlN) material system. The process of implementing this device is carried out in five principal stages. First, light coupling from optical fibers to the AlN thin film is demonstrated with the use of on-chip grating couplers, exhibiting a peak insertion loss of -6.6 dB and a high 1 dB bandwidth of 60 nm for operation in the telecommunications C- and L-bands. This is followed by characterization of photonic whispering gallery mode microdisk and microring resonators with optical quality factors on the order of 104. Next, a robust fabrication method combining optical and electron-beam lithography is developed to produce a fully-integrated device preserving the critical features for acoustic and photonic resonators to be colocalized in the same platform. Acousto-optic modulation is demonstrated with the use of a contour mode resonator which drives displacements in the photonic resonator at 653 MHz, corresponding to the mechanical resonance of the composite structure. The modulator is then implemented in an opto-acoustic oscillator loop, for which an initial phase noise of -72 dBc/Hz at 10 kHz offset from the carrier is recorded with a large contribution from thermal noise at the photodetector. Finally, some possibilities to improve the modulator efficiency and oscillator phase noise are provided along with prospects for future work in this area.