The selective detection of biomolecules, such as proteins or DNA strands, is of vitally importance for medical diagnosis. Optical biosensors are believed to be a promising way to overcome the limitations of expensive and time-consuming state-of-the-art diagnostic tests. In this thesis, the development of a fully integrated Mach-Zehnder interferometer biosensor based on high index contrast polymer waveguides is reported. The optical sensor design, based on grating waveguide couplers for light

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... and out-coupling as well as single mode polymer waveguides, is fully compatible with cost-efficient mass production technologies for polymers such as injection molding and spin coating, which makes the sensor an attractive alternative to inorganic optical sensors. The sensor elements are rigorously simulated and optimized. For an improved efficiency of small grating couplers in material systems with comparatively low index contrasts, the novel approach of a high index coating on top of grating couplers was applied. Simulations revealed a nearly 8 dB increase in the maximum coupling efficiency into narrow single mode waveguides by means of grating couplers due to the high index coating. The positive effect of the high index coating was then experimentally verified. Finally, the polymer waveguide based biosensor was applied for label-free online measurements of biotin-streptavidin binding processes on the sensor surface at a wavelength of 1310 nm. For the binding experiments, the surface of the polyimide waveguide core layer was functionalized with 3-mercaptopropyl trimethoxy silane and malemide tagged biotin. Despite the large wavelength and the comparatively low surface sensitivity of the sensor system due to the low index contrast in polymer material systems compared to inorganic material systems, streptavidin concentrations down to 0.1 µg/ml were resolved.