Silicon-on-insulator microring resonators have proven to be an excellent platform for label-free nanophotonic biosensors. The high index contrast of the silicon-on-insulator waveguides allows for fabrication of micrometer size sensors. Their small size combined with high sensitivity make them ideal candidates for integration in sensing arrays as a multiplexed DNA detection platform. By chemically modifying the sensor surface, the microrings can provide sequence selective DNA detection. However, the high index contrast also limits the quality of the resonances by introducing an intrinsic mode-splitting by coupling the degenerate resonator modes. This severely deteriorates the quality of the output signal. The quality of the resonances is of utmost importance to determine the performance of the microrings as a biosensor. We will suggest an integrated interferometric approach to give access to the unsplit, high-quality normal modes of the microring resonator.
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