Near-field optical mode engineering-enabled freeform nonlocal metasurfaces

TL;DR

This paper presents an inverse design framework for near-field optical mode engineering, enabling the creation of complex, multifunctional nonlocal metasurfaces with applications in sensing, nonlinear optics, and quantum information.

Contribution

It introduces a novel inverse design method for tailoring near-field distributions in dielectric nanostructures, facilitating the discovery of new nonlocal metasurfaces with multi-wavelength and chiral functionalities.

Findings

Optimized freeform nonlocal metasurfaces support bound states in the continuum.

Demonstrated multi-wavelength and chiral metasurfaces experimentally.

Framework applicable to high-Q-factor metasurface platforms.

Abstract

Nanophotonic technologies inherently rely on tailoring light-matter interactions through the excitation and interference of deeply confined optical resonances. However, existing concepts in optical mode engineering remain heuristic and are challenging to extend towards complex and multi-functional resonant phenomena. Here, we introduce an inverse design framework that optimizes near-field distributions, ideally suited to tailor Mie-type modes within dielectric nanophotonic structures, and we demonstrate its powerful opportunities to facilitate the discovery of new classes of nonlocal metasurfaces. We show that freeform nonlocal metasurfaces supporting accidental bound states in the continuum can be readily optimized to tackle tailored illumination conditions, modal properties and quality factors. We further extend our approach to multifunctional and multipolar mode engineering, and experimentally demonstrate freeform planar nonlocal multi-wavelength and chiral metasurfaces. Our versatile and robust framework for freeform mode engineering has applications in a broad range of high quality-factor metasurface platforms relevant to sensing, nonlinear optics, optomechanics and quantum information processing.