Two-dimensional optical spatial differentiation and high-contrast imaging

Abstract

Optical analog signal processing technology has been widely studied and applied in a variety of science and engineering fields. It overcomes low-speed and high-power consumption disadvantages compared with its digital counterparts. Meanwhile, the emerging metasurface technology has been introduced to optical imaging and processing system and attracted much attentions. Here, we demonstrate the first broadband two-dimensional spatial differentiation and high-contrast edge imaging based on a dielectric metasurface across the whole visible spectrum. This edge detection method works for both intensity and phase objects simply by inserting the metasurface into a commercial optical microscope. The exploration of the highly efficient metasurface performing a basic optical differentiation operation opens new opportunities in applications of fast, compactible and power-efficient ultrathin devices for data processing and biological imaging.

Switchable and Simultaneous Spatiotemporal Analog Computing

“…To start the design and perform an accurate evaluation of the proposed structure, graphene is modeled as an infinitesimally thin sheet with surface impedance Z = 1/σ g , where σ g is the frequency-dependent complex conductivity of graphene. The surface conductivity of graphene including both intraband (σ intra ) and interband (σ inter ) transitions are governed by the well-known Kubo formula 48,49 σ g (ω, τ, µ c , T) = σ intra (ω, τ, µ c , T) + σ inter (ω, τ, µ c , T) , (17) 11/28 σ intra (ω, τ, µ c , T) = -j e 2 k B T πh 2 (ω-jτ -1 )…”

“…on photonic crystal slabs 4 , plasmonic surfaces 5 , metasurfaces [6][7][8][9][10][11] , photonic spin Hall insulators 12 , inverse-designed metastructures 13 or topological wave insulators 14 . In optics, one-and two-dimensional image edge detection has been demonstrated using various platforms, such as optical metasurfaces [15][16][17][18] and surface plasmons 5 . On the other hand, temporal analog signal processing systems manipulate signals in the time domain with a dispersive structure, called a phaser 19 .…”

Computing metasurfaces enabled chiral edge image sensing

“…Computing metasurfaces are two-dimensional artificial nanostructures capable of performing mathematical operations on the input electromagnetic field ( Silva et al., 2014 ; Pors et al., 2015 ; Hwang and Davis, 2016 ; Zhu et al., 2017 ; Lee et al., 2017 ; Zangeneh-Nejad et al., 2020 ; Li et al., 2021 ; Jin et al., 2021 ; Yung et al., 2022 ; He et al., 2022 ; Fu et al., 2022 ). The spatial differentiation operations based on computing metasurfaces have been applied for all-optical image processing, especially for edge detection ( Dong et al., 2018 ; Kwon et al., 2018 ; Zhou et al., 2019 , 2020 , 2021 ; Momeni et al., 2019 ; Huo et al., 2020 ; Liu et al., 2020 ; Wesemann et al., 2021 ; Solntsev et al., 2021 ; Yang et al., 2021 ). In recent years, because of the sensitivity to changes in physical parameters of the system, weak-value amplification techniques have been proposed for the chiral sensing ( Rhee et al., 2013 ; Wang et al., 2020 ).…”

Monolithic metasurface spatial differentiator enabled by asymmetric photonic spin-orbit interactions

“…Notably, optical spatial computing based on metamaterials including differentiators, integrators, and equation solvers is proposed by Silva et al in 2014 [34], opening new avenues for optical analog computing. Since then, various differentiator metasurfaces are developed based on photonic crystals [5,35], spin Hall effect [36], surfaces plasmons [37], high-contrast gratings [8], and Pancharatnam-Berry (PB) phase [38,39]. However, additional prisms or lenses are still required for plasmon coupling or Fourier transform in those applications [37,40], which is incompatible with the flat and compact optical systems.…”