Edge detection imaging by quasi-bound states in the continuum

TL;DR

This paper demonstrates how a quasi-bound state in the continuum (quasi-BIC) in an all-dielectric metasurface can be used for efficient, polarization-independent edge detection imaging, advancing optical computing technology.

Contribution

It introduces a novel quasi-BIC metasurface design capable of isotropic 2D spatial differentiation for edge detection, with experimental validation on silicon-on-insulator platforms.

Findings

Successful fabrication of quasi-BIC metasurfaces on silicon-on-insulator.

High-quality, efficient, and polarization-independent edge detection achieved.

Theoretical and experimental validation of edge detection mechanism.

Abstract

Optical metasurfaces have revolutionized analog computing and image processing at sub-wavelength scales with faster speed and lower power consumption. They typically involve spatial differentiation with engineered angular dispersion. Quasi-bound states in the continuum (quasi-BICs) have recently emerged as a powerful tool for tailoring properties of optical resonances. While quasi-BICs have been explored in various applications that require high $Q$-factors and enhanced field confinement, their full potential in image processing remains unexplored. Here, we demonstrate edge detection imaging by leveraging a 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. Importantly, we find that with suitable parameters, this quasi-BIC metasurface can perform isotropic two-dimensional spatial differentiation, which is the core element for realizing edge detection. Following the theoretical design, we fabricate the metasurfaces on the silicon-on-insulator platform and experimentally validate their capability of high-quality, efficient, and uniform edge detection imaging under different incident polarizations. Our results illuminate the mechanisms of edge detection with quasi-BIC metasurfaces and highlight new opportunities for their application in ultra-compact, low-power optical computing devices.