Optical and geometric control of light propagation in planar silicon photonic crystal structures

Photonic crystals offer new ways of confining light and controlling its propagation. In particular, silicon-based photonic crystal structures, because of their high refractive index contrasts at near infra-red wavelengths, can do so on a sub-micron scale. Such miniaturization is an enabling factor for high density optical integration.;A basic requirement for optical integration is the availability of other active components providing a higher functionality. In this dissertation we explore the use of optically-induced plasma dispersion and thermo-optic effects to achieve modulation of light in silicon photonic crystal waveguides and microcavities at frequencies of up to a giga-Hertz. In addition, we propose a possible solution to the basic problem of finding geometric structures with optimal bandgaps---a feature central to the utilization of photonic crystals as light guides. We also address the practical problem of finding appropriate photonic crystal taper structures for coupling light from wide waveguides into the often much narrower photonic crystal waveguides.