Photonic crystal waveguides for silicon integrated optics

This thesis reports experimental and theoretical studies on photonic crystal waveguides in the silicon-on-insulator platform. The work presents a new variant of Fabry-Pérot method for waveguide characterization. In this method, the reflectivity at the ends of the waveguide under study is enhanced by lithographically patterned mirrors. The thesis also studies a new type of photonic crystal, where the planar photonic crystal lattice is defined with ring-shaped holes (RPhC). By choosing a suitable ring parameter, the RPhC waveguide exhibits low and quasi constant group velocity over a wavelength range of several nanometers. The effect of the modefield width on the dispersion properties of the waveguide is discussed. A short and efficient coupler between the slow mode in an RPhC waveguide and the mode in a conventional silicon waveguide is designed. A relationship between coupling efficiency and the phase match between the coupler mode and the slow mode is observed. These results and observations are important in designing slow-light devices for all-optical signal processing and communication systems. Use of RPhC waveguides in other applications, particularly in biosensing, is also studied. An electron beam writing method that minimizes the writing time of the RPhC lattice is presented. The experimental results on an RPhC waveguide are the first reported for such structure and they show slowdown factors of up to 22 for the group velocity, compared to the group velocity in vacuum