Wavefront-selective Fano resonant metasurfaces

Abstract

Fano resonances are conventionally understood as sharp spectral features with selectivity in the momentum-frequency domain, implying that they can be excited only by plane waves with specific frequencies and incident angles. We demonstrate that Fano resonances can be made generally selective in the spacefrequency domain. They can be tailored to resonate only when excited by a frequency, polarization, and wavefront of choice. This generalization reveals that Fano systems are characterized by eigenwaves that scatter to their time-reversed image upon reflection. Although in conventional Fano systems this trivially occurs for normally incident plane waves, we show that, in general, the selected wavefront is locally retroreflected everywhere across the device. These results show that conventional Fano resonances are a subset of a broader dichroic phenomenon with spin, spatial, and spectral selectivity. We demonstrate these concepts with nonlocal metasurfaces whose governing principles are deeply rooted in the symmetry features of quasi-bound states in the continuum. Enhanced light-matter interactions and symmetry-protection make these phenomena uniquely suited for enriching applications in quantum optics, non-linear optics, augmented reality, and secure optical communications, laying the groundwork for a range of novel compact optical sources and devices.

An Intelligent Programmable Omni‐Metasurface

“…Thus, metasurfaces have facilitated many intriguing functional devices such as flat metalenses, [ 9,10 ] cloaks, [ 11 ] antennas, [ 12,13 ] holographic imagers, [ 14–16 ] and many other potential applications across the whole spectrum ranging from microwave to terahertz and optical regions. [ 17–22 ]…”

“…Thus, metasurfaces have facilitated many intriguing functional DOI: 10.1002/lpor.202100718 devices such as flat metalenses, [9,10] cloaks, [11] antennas, [12,13] holographic imagers, [14][15][16] and many other potential applications across the whole spectrum ranging from microwave to terahertz and optical regions. [17][18][19][20][21][22] More recently, metasurfaces in the microwave region have been adopted as a promising alternative to adjust EM wave propagations, enhance wireless service performance, and improve received power in wireless communication systems due to their programmable characteristics. [23][24][25] Considering an indoor wireless communication system, users generally suffer from poor quality and limited coverage of communication services due to severe channel fading and potential obstacles.…”

Nearly Perfect Transmissive Subtractive Coloration through the Spectral Amplification of Mie Scattering and Lattice Resonance

“…We trust that the color gamut and the color distinction can be improved using interleaved meta-atoms, 65,68,69 recently studied high-Q resonances with nonlocal metasurfaces, 70,71 Fano resonance, 72,73 Quasi-BIC, 74,75 and so on. We believe that our theoretical and experimental research on spectral engineering of all-dielectric metasurfaces may present a promising way to realize practical metadevices such as imaging devices, dynamic color displays, and photorealistic color printing.…”

Free-Space Nonreciprocal Transmission Based on Nonlinear Coupled Fano Metasurfaces

“…Fano resonant metasurfaces have been widely studied in nanophotonics. More recently, there has been significant work devoted to realize high-quality factor Fano resonances for optical and visible frequencies based on bound states in the continuum (BICs) [35][36][37][38][39][40][41]. Due to their enhanced light-matter interactions, these BIC metasurfaces can be efficiently employed in nonlinear optics applications [35].…”