Imaging Through a Fano-Resonant Dielectric Metasurface Governed by Quasi--bound States in the Continuum

Fano resonance has attracted great attention in nanophotonics attributed to its unique properties. In this work, we study the imaging function of a Fano-resonant silicon metasurface governed by quasi--bound states in the continuum (quasi-BICs). First, by breaking the in-plane symmetry of nanodisks, a symmetry-protected quasi-BIC is excited with the emergence of a sharp Fano resonance. The near-field distributions, multipole contributions, and radiation patterns of the metasurface are investigated to uncover the mechanism and characteristics of this resonance. In addition, we investigate the imaging function of this Fano-resonant metasurface assisted by phase-change material Ge₂Sb₂Te₅ (GST). Through selective modification of different units from a-GST to c-GST, the produced transmitted image well reconstructs the target letter. Our findings may provide a route to achieve efficient metasurface-based imaging and fast spatial modulations.