Design and applications of multi-channel directional couplers

The research in this thesis presents the analysis and design of multi-channel directional coupler structures for applications in optical sensing and electro-optic devices. The structures are analysed using supermodes and a potential limitation is identified with the discovery of the phenomenon of partial image revivals. A detailed analysis is presented along with one possible exploitation of this phenomenon with the design of a compact wavelength division multiplexer. The outcomes of the research include: i) an evanescent field optical sensor is designed using the multi-channel directional coupler structure; the design is based on the idea that the analyte to be measured infiltrates the spacing between the coupled waveguides so that the sensor can exploit the exponential dependence of the coupling on the analyte refractive index; ii) an optical chemical sensor is designed that uses silicon slot waveguides; the sensor exploits the high confinement of light in the slots, whilst retaining the exponential dependence of the coupling on the analyte refractive index; iii) discovery of the differential multi-channel directional coupler structure; and the design of a more efficient optical chemical sensor using this structure; iv) a multichannel directional coupler refractive index sensor is design in fiber, i.e. as a dual-core microstructured optical fiber; v) a compact wavelength division multiplexer for fluorescence sensing is designed; vi) electro-optic devices including an optical electric field sensor, switch and modulators are design using the multi-channel directional coupler structure and recent electro-optic materials.