Homogeneous and Significant Near-Field Enhancement in All-Dielectric Metasurfaces for Sensing Applications

Abstract

All-dielectric metasurfaces supporting high-Q resonances have emerged as a promising platform for sensing applications. However, the greatly enhanced near-fields are usually confined within the all-dielectric nanostructures rather than the outside analyte region, severely limiting the bulk sensitivity and the biosensing performance. Here, a silicon metasurface formed by the hybridization of two lattices with a relative displacement is designed to support nonlocal quasi-bound states in the continuum (q-BICs) featuring homogeneous and significant near-field enhancement over large volumes outside the silicon nanodisks. A high bulk sensitivity of 407 nm RIU–1 is experimentally demonstrated for the refractive index sensing applications, and a limit of detection down to 20 pg mL–1 for a protein biomarker for the early-stage breast cancer screening, which is improved by more than an order of magnitude over the state of the art. It is expected that the nonlocal q-BICs open new opportunities for realizing greatly enhanced light–matter interactions over large volumes in applications beyond biochemical sensing.