High Quality-Factor All-Dielectric Metacavity for Label-Free Biosensing.

High sensitivity and high quality-factor are crucial for achieving outstanding sensing performance in photonic biosensors. However, strong optical field confinement and high light-biomolecule interactions on photonic surfaces are usually contradictory and challenging to satisfy simultaneously. Here, a distinctive configuration for addressing this issue is reported: embedding a nanophotonic metasurface inside a micro vertical cavity as a meta-channel (metacavity) biosensor. The analyte solution serves as the cavity medium, thereby maximizing the light-analyte interaction. Simulation validation is conducted to optimize the metacavity with high structural robustness and remarkable optical and sensing properties. Large-scale low-cost metacavity biosensors are realized by combining anodic aluminum oxide template technique and wafer bonding. Experimentally, the metacavity biosensor demonstrates a notable quality-factor (maximum 4140) and high bulk refractometric sensitivity (450 nm RIU-1), resulting in an unprecedented figure-of-merit (1670 RIU-1). Moreover, the metacavity biosensor achieves high surface sensitivity, together with a detection-limit of 119 viral copies mL-1 for label-free severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pseudovirus sensing, revealing remarkable performance in both bulk and surface sensing.