Cavity-Waveguide Coupling Engineered High Sensitivity Silicon Photonic Crystal Microcavity Biosensors With High Yield

We present a high yield and high sensitivity on-chip biosensing system by combining subwavelength grating coupling and high sensitivity photonic crystal microcavity side coupled to a photonic crystal waveguide. 80% yield of working devices was experimentally demonstrated for sensitivity engineered L13 photonic crystal microcavities and 70% for L21 photonic crystal microcavities. Subwavelength grating couplers significantly improved the quality of the output transmission spectrum. By engineering the optical loss rate from the cavity to the waveguide, we experimentally detected 1 pM (67 pg/ml) and 50 femto-molar (3.35 pg/ml) concentration of avidin binding to biotin in phosphate buffered saline for L21 and L55 PC microcavities respectively, which represents the highest sensitivity versus other chip-based optical biosensors.