Edge Detection Imaging by Quasi-Bound States in the Continuum

Optical metasurfaces have revolutionized analog computing and image processing at subwavelength scales with faster speed and lower power consumption. They typically involve spatial differentiation with an engineered angular dispersion. Quasi-bound states in the continuum (quasi-BICs) have emerged as powerful tools for customizing optical resonances. While quasi-BICs have been widely used with high Q-factors and enhanced field confinement, their potential in image processing remains unexplored. Here, we demonstrate edge detection imaging by leveraging quasi-BIC in an all-dielectric metasurface. This metasurface, composed of four nanodisks per unit cell, supports a polarization-independent quasi-BIC through structural perturbations, allowing simultaneously engineering Q-factor and angular dispersion. It can perform isotropic two-dimensional spatial differentiation, which is crucial for edge detection. We fabricate the metasurfaces and validate their efficient, high-quality edge detection under different polarizations. Our findings illuminate the mechanisms of edge detection with quasi-BIC metasurfaces, opening new avenues for ultracompact, low-power optical computing devices.