Enhanced surface sensitivity in microring resonator biosensor based on subwavelength grating waveguides

Microring resonators on silicon-on-insulator substrate have been demonstrated to be promising in sensing applications. We study a microring resonator biosensor based on a novel subwavelength grating (SWG) waveguide structure, which consists of periodic silicon pillars in the propagation direction with a subwavelength period. In this structure, effective sensing region includes not only the top and side of the waveguide, but also the space in between the silicon pillars which is on the path of the propagation mode. This leads to greatly increased bulk refractive index sensitivity as well as extended surface sensing region with constantly high surface sensitivity.