Multifunctional resonant wavefront-shaping meta-optics based on multilayer and multi-perturbation nonlocal metasurfaces

Abstract

Photonic devices rarely provide both elaborate spatial control and sharp spectral control over an incoming wavefront. In optical metasurfaces, for example, the localized modes of individual meta-units govern the wavefront shape over a broad bandwidth, while nonlocal lattice modes extended over many unit cells support high quality-factor resonances. Here, we experimentally demonstrate nonlocal dielectric metasurfaces in the near-infrared that offer both spatial and spectral control of light, realizing metalenses focusing light exclusively over a narrowband resonance while leaving off-resonant frequencies unaffected. Our devices attain this functionality by supporting a quasi-bound state in the continuum encoded with a spatially varying geometric phase. We leverage this capability to experimentally realize a versatile platform for multispectral wavefront shaping where a stack of metasurfaces, each supporting multiple independently controlled quasi-bound states in the continuum, molds the optical wavefront distinctively at multiple wavelengths and yet stay transparent over the rest of the spectrum. Such a platform is scalable to the visible for applications in augmented reality and transparent displays.

Emerging Planar Nanostructures Involving Both Local and Nonlocal Modes

“…Copyright 2022 the Authors. (c) Reprinted under the terms of Creative Commons license () from ref . Copyright 2022 the Authors, published by Springer Nature.…”

“…22 (c) SEM image of multifunctional few-layer metasurfaces exploiting multiperturbations on nonlocal modes. 23 (d) Dynamic focusing by perturbative metagratings composed of photorefractive silicon nanolines. 72 (e) SEM image of superthin high-Q matagratings with independent diffraction efficiency across different wavelength bands.…”

“…22 Figure 2c shows the SEM images of the multilayer perturbative nonlocal metasurfaces, by which multifunctional resonant focusing and abnormal refraction were experimentally observed, and applications of augmented reality were further conceptually demonstrated. 23 In addition to perturbative nonlocal metasurfaces, diffractive metagratings are an alternative to achieve efficient narrow-band optical field manipulations. Figure 2d−e illustrates representative works of diffractive metagratings that apply nanoscale defects in homogeneous waveguides to construct supercells and introduce minimal couplings to the diffraction channels.…”

Universal narrowband wavefront shaping with high quality factor meta-reflect-arrays

“…But the corresponding radiation patterns have complicated high order features, making them poor candidates for metasurface building blocks 33,34 . Nonlocal metasurfaces exhibiting high-Q extended modes that have shaped instead of at phase distributions have also emerged [35][36][37] . Rather than applying a tailored transfer function to incoming waves, these structures can resonantly enhance speci c wavefronts, which is useful for focusing incoherent emission 38 , for example.…”

Versatile platform of nonlocal metasurfaces for both spectral and spatial control of light waves

“…In recent work published in Light: Science & Applications , Malek et al experimentally demonstrated a multifunctional platform of nonlocal metasurfaces in the near-infrared region for independent multispectral wavefront shaping with high Q-factors 12 . The systems are based on photonic crystal slabs fabricated on an amorphous silicon film etched with pairs of rectangular holes on silica substrate supporting q-BICs encoded with a spatially varying geometric phase.…”