Freestanding metasurfaces for optical frequencies

Abstract

We present freestanding metasurfaces operating at optical frequencies with a total thickness of only 40 nm. The metasurfaces are fabricated by focused ion beam milling of nanovoids in a carbon film followed by thermal evaporation of gold and plasma ashing of the carbon film. As a first example, we demonstrate a metasurface lens based on resonant V-shaped nanovoids with a focal length of 1 mm. The second example is a metasurface phase-plate consisting of appropriately oriented rectangular nanovoids that transforms a Gaussian input beam into a Laguerre-Gaussian LG−1,0 mode.

Electron energy-loss spectroscopy on freestanding perforated gold films

“…The experimental results are in accordance with numerical computations based on the discontinuous Galerkin time-domain (DGTD) method [34,35]. The sample fabrication process [31] is based on a commercially available carbon film grid (Quantifoil Cu 200 mesh from Quantifoil Micro Tools GmbH) for application in transmission electron microscopy. The approximately 15 nm thick carbon film is patterned by focused ion beam milling with Gallium ions accelerated to 30 keV with a current of 50 pA (see Fig.…”

“…The freestanding films were fabricated by several different methods like cold-rolling of silver [19,20], or transferring the film from a solution onto a supporting grid [30]. Here, we apply a highly reproducible three step method to fabricate freestanding perforated metal films of different thicknesses down to 20 nm [31]. We characterize the samples both in the farfield with optical transmission spectroscopy and in the near-field with EELS.…”

In3SbTe2 as a programmable nanophotonics material platform for the infrared

“…Plasmonics achieves this goal by employing evanescent electromagnetic modes supported by metallic nanostructures to concentrate light fields to deeply subwavelength regions 2,3 . Arranging plasmonic nanoantennas ("meta-atoms") in subwavelength assemblies in so-called metasurfaces allows for realizing ultrathin optical devices with exciting functionalities like beam steering 4 , lensing 5,6 , and holography 7,8 . While these functionalities are originally fixed upon fabrication, they can be rendered active by multiple means including antenna geometry change by mechanical deformation [9][10][11] , charge carrier tuning by electric biasing 12,13 , and inducing an insulator-metal transition in VO 2 by heating [14][15][16][17] .…”

Polarization‐Sensitive Dielectric Membrane Metasurfaces

“…[14] To eliminate this limitation, the freestanding metasurfaces consisting of arrays of holes made in a thin membrane of highindex dielectric material is introduced. [19,22,23] While such metasurface visually resembles a photoniccrystal slab, [24][25][26] in contrast to photonic crystals, it relies on local Mietype resonant scattering rather than the periodicity of the structure. Such a membrane can realize high transmission and 2π phase coverage.…”