Optical metasurfaces for subwavelength difference operations

Abstract

Coupled metal nanostructures supporting localized surface plasmon resonances are represented as a nanoscale optical circuit that takes light fields as inputs and forms linear combinations of them with complex coefficients. The subwavelength arrays of these circuits form a metasurface that performs mathematical operations in two dimension on an incident light field. We demonstrate this concept with subwavelength scale plasmonic circuits that perform difference operations. The metasurface is fabricated from the arrays of coupled gold nanorods where each group of three rods forms the difference circuit. The operation of the metasurface is demonstrated experimentally.

Optical Chirality from Dark‐Field Illumination of Planar Plasmonic Nanostructures

“…[25][26][27][28][29] These two points suggest that we should be able to directly translate the chiral operation of a single oligomer into a homogenized metasurface platform. So we also explore arrays of oligomers, as to show relevance of these concepts toward pursuit of plasmonic metasurfaces for polarization control, and other applications for flat optics [30][31][32][33] that capitalize on 2-dimensional fabrication. The single oligomer experiments in Figures 1, 3 and 4 have shown that each oligomer scatters light significantly more efficiently for either RCP or LCP, and these differences in scattering can generally be expected to affect the radiative coupling strength between an oligomer and its neighbors in the surrounding lattice.…”

Selective near-perfect absorbing mirror as a spatial frequency filter for optical image processing

“…Nanophotonic, all-optical image processing methods on the other hand offer ultra-compact, real time and low power consumption alternatives for use in emerging integrated analogue optical computing and image processing devices [8,9]. There has been considerable recent interest in the use of metasurfaces or subwavelength gratings for optical information processing [9][10][11][12][13]. Attention has focussed on optical computing of spatial differentiation although experimental demonstrations have been limited and restricted to operations in one dimension [14,15].…”

First-order optical spatial differentiator based on a guided-mode resonant grating

“…In particular, in a recent work [2] it was theoretically shown that a metamaterial layer with a specially designed structure enables performing the operations of differentiation and integration of an optical beam with respect to a spatial coordinate. In the second group (resonant structure approach), various resonant diffractive structures including systems of multiple homogeneous layers [4][5][6][7][8][9][10], plasmonic circuits [11,12], and resonant diffraction gratings [13][14][15] are used. The possibility to utilize such resonant structures for optical differentiation or integration is based on the fact that the Fano profile describing the reflection or the transmission coefficient of the structure in the vicinity of the resonance can approximate the transfer function of a differentiating or integrating filter [4,5,13].…”