Flat Plasmonic Biosensor with an On-Chip Metagrating-Integrated Laser

Metasurfaces are emerging as a transformative platform in optics, offering compact and versatile alternatives to bulky traditional components. Here, we present a metasurface-enabled, on-chip surface plasmon resonance (SPR) biosensor that enables label-free biomolecular analysis in a miniaturized, chip-scale format. By integrating flat metaoptics together with semiconductor lasers, a collimated fan of light for angle-resolved SPR measurements can be emitted directly into a glass substrate, eliminating the need for conventional optics. As a proof of concept, we demonstrate a bulk refractive index sensitivity of 4.9 × 10^-6 RIU, along with multiplexed detection of low-molecular-weight microRNA with limits of detection of 0.1 nM via direct sensing and 0.02 nM with antibody amplification. The scalability of metasurface fabrication, coupled with the low cost of semiconductor lasers, suggests this platform can be readily adapted for diverse sensing modalities and mass manufacture, potentially transforming SPR beyond its conventional, benchtop implementations.