This thesis encompasses a theoretical analysis, the fabrication, and optical characterization of a novel compact Bragg Slot Waveguide with a Cavity (BSWC). Strong light confinement in the low refractive index slot region formed by two silicon slabs on a silicon dioxide substrate [1] makes this structure useful for optofluidic, sensing, and optical trapping applications. The transmission spectrum of the BSWC can be engineered through the dimensional variations of the waveguide and through the refractive index change of the surrounding medium. BSWC is compact and can be integrated with various components on a chip for increased functionality. The results in this thesis show a good agreement between analytical and experimental results, while emphasizing the increasing importance of atomic-scale imperfections as a result of fabrication on the nano-scale. The impact of the slot width, slab width, and the cavity length on the waveguide transmission spectrum is investigated.

This thesis encompasses a theoretical analysis, the fabrication, and optical characterization of a novel compact Bragg Slot Waveguide with a Cavity (BSWC). Strong light confinement in the low refractive index slot region formed by two silicon slabs on a silicon dioxide substrate [1] makes this structure useful for optofluidic, sensing, and optical trapping applications. The transmission spectrum of the BSWC can be engineered through the dimensional variations of the waveguide and through the refractive index change of the surrounding medium. BSWC is compact and can be integrated with various components on a chip for increased functionality. The results in this thesis show a good agreement between analytical and experimental results, while emphasizing the increasing importance of atomic-scale imperfections as a result of fabrication on the nano-scale. The impact of the slot width, slab width, and the cavity length on the waveguide transmission spectrum is investigated.

En los últimos años y debido a la Sociedad de la Información en la que vivimos, la cantidad de información que se transmite por las redes de comunicaciones aumenta de forma exponencial. Esto se debe a un aumento en el número de usuarios y a la aparición de nuevas aplicaciones que demandan un gran ancho de banda. Esta necesidad de mayores anchos de banda provoca que el procesado electrónico en los nodos de comunicaciones esté llegando a su límite y se necesitan nuevas tecnologías que realicen dichas funciones en el dominio óptico por su mayor ancho de banda y evitar la conversión opto-electrónica. Un primer paso para poder realizar procesado fotónico es el desarrollo de puertas lógicas todo ópticas. El objetivo de esta tesis doctoral es el estudio y caracterización de una puerta lógica XOR como primer paso para el procesado fotónico. La fabricación se realiza mediante tecnología CMOS de fabricación en masa. Para ello se ha estudiado un nuevo tipo de guía llamado guía ranurada (slot-waveguide) en la que el campo óptico se confina en una región nanométrica aumentando su intensidad. Se han optimizado sus dimensiones para maximizar los efectos no lineales y se han investigado técnicas de acoplo para disminuir las pérdidas de inserción. Para los efectos no lineales se ha empleado un novedoso material basado en nanocristales de silicio en SiO2. Se han estudiado estructuras de anillos resonantes e interferómetros Mach-Zehnder para la realización de un conmutador todo óptico y una puerta lógica XOR respectivamente. También se ha analizado un desfasador de 90º basado en un anillo resonante para integrarlo en un modulador vectorial fotónico. Todas estas estructuras se han podido fabricar y caracterizar experimentalmente. Se han obtenido las pérdidas de propagación de las guías ranuradas. Se ha caracterizado la respuesta de estructuras de anillos resonantes e interferómetros Mach-Zehnder obteniendo sus parámetros óptimos. / Blasco Solbes, J. (2009). Desarrollo de aplicaciones basadas en la guía nanofotónica de silicio tipo ranura [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/6290 / Palancia

Silicon is the dominant material in Microelectronics. Building photonic devices out of silicon can leverage the mature processing technologies developed in silicon CMOS. Silicon is also a very good waveguide material. It is highly transparent at 1550nm, and it has very high refractive index of 3.46. High refractive index enables building high index contrast waveguides with dimensions close to the diffraction limit. This provides the opportunity to build highly integrated photonic integrated circuit that can perform multiple functions on the same silicon chip, an optical parallel of the electronic integrated circuit. However, silicon does not have some of the necessary properties to build active optical devices such as lasers and modulators. For Example, silicon is an indirect band gap material that can’t be used to make lasers. The centro-symmetric crystal structure in silicon presents no electro-optic effect. By contrast, electro-optic polymer can be engineered to show very strong electro-optic effect up to 300pm/V. In this research we have demonstrated highly compact and efficient devices that utilize the strong optical confinement ability in silicon and strong electro-optic effect in polymer. We have performed detailed investigations on the optical coupling to a slow light waveguide and developed solutions to improve the coupling efficiency to a slow light photonic crystal waveguides (PCW). These studies have lead to the demonstration of the most hybrid silicon modulator demonstrate to date and a compact chip scale true time delay module that can be implemented in future phased array antenna systems. In the future, people may be able to realize a photonic integrated circuit for optical communication or sensor systems using the devices we developed in our research. / text

Nowadays, silicon photonics is a widely studied research topic. Its high-index-contrast and compatibility with the complementary metal-oxide-semiconductor technology make it a promising platform for low cost high density integration. Several general problems have been brought up, including the lack of silicon active devices, the difficulty of light coupling, the polarization dependence, etc. This thesis aims to give new attempts to novel solutions for some of these problems. Both theoretical modeling and experimental work have been done. Several numerical methods are reviewed first. The semi-vectorial finite-difference mode solver in cylindrical coordinate system is developed and it is mainly used for calculating the eigenmodes of the waveguide structures employed in this thesis. The finite-difference time-domain method and beam propagation method are also used to analyze the light propagation in complex structures. The fabrication and characterization technologies are studied. The fabrication is mainly based on clean room facilities, including plasma assisted film deposition, electron beam lithography and dry etching. The vertical coupling system is mainly used for characterization in this thesis. Compared with conventional butt-coupling system, it can provide much higher coupling efficiency and larger alignment tolerance. Two novel couplers related to silicon photonic wires are studied. In order to improve the coupling efficiency of a grating coupler, a nonuniform grating is theoretically designed to maximize the overlap between the radiated light profile and the optical fiber mode. Over 60% coupling efficiency is obtained experimentally. Another coupler facilitating the light coupling between silicon photonic wires and slot waveguides is demonstrated, both theoretically and experimentally. Almost lossless coupling is achieved in experiments. Two approaches are studied to realize polarization insensitive devices based on silicon photonic wires. The first one is the use of a sandwich waveguide structure to eliminate the polarization dependent wavelength of a microring resonator. By optimizing the multilayer structure, we successfully eliminate the large birefringence in an ultrasmall ring resonator. Another approach is to use polarization diversity scheme. Two key components of the scheme are studied. An efficient polarization beam splitter based on a one-dimensional grating coupler is theoretically designed and experimentally demonstrated. This polarization beam splitter can also serve as an efficient light coupler between silicon-on-insulator waveguides and optical fibers. Over 50% coupling efficiency for both polarizations and -20dB extinction ratio between them are experimentally obtained. A compact polarization rotator based on silicon photonic wire is theoretically analyzed. 100% polarization conversion is achievable and the fabrication tolerance is relatively large by using a compensation method. A novel integration platform based on nano-epitaxial lateral overgrowth technology is investigated to realize monolithic integration of III-V materials on silicon. A silica mask is used to block the threading dislocations from the InP seed layer on silicon. Technologies such as hydride vapor phase epitaxy and chemical-mechanical polishing are developed. A thin dislocation free InP layer on silicon is obtained experimentally. / QC20100705