Improved performance of highly multiplexed silicion-on-insulator microring sensor chips by surface structure implementation

Silicon-on-insulator microring resonators have proven to be an excellent platform for label-free nanophotonic biosensors. The high index contrast of the silicon-an-insulator platform allows for fabrication of micrometer size sensors and a high degree of multiplexing. To enable robust, low-noise performance of a microring resonator sensor chip in a lab-on-a-chip setting, flood illuminating an array of vertical grating couplers is a promising approach to couple input light into the chip. This technique provides a very high alignment tolerance while at the same time exciting multiple sensors simultaneously for rapid parallel read-out. We demonstrate this technique to obtain a highly multiplexed chip output combined with real time sensor information. However, parasitic reflections on the chip surface can deteriorate the sensor signal and limit the performance. We investigate the use of surface structures to limit these parasitic signals and show a significant improvement of the sensor operation.