Abstract
Metasurfaces are ideal candidates for conformal wave manipulation on curved objects due to their low profiles and rich functionalities. Here we design and analyze conformal metasurfaces for practical optical applications at 532 nm visible band for the first time. The inclusions are silicon disk nanoantennas embedded in a flexible supporting layer of polydimethylsiloxane (PDMS). They behave as local phase controllers in subwavelength dimensions for successful modification of electromagnetic responses point by point, with merits of high efficiency, at visible regime, ultrathin films, good tolerance to the incidence angle and the grid stretching due to the curvy substrate. An efficient modeling technique based on field equivalence principle is systematically proposed for characterizing metasurfaces with huge arrays of nanoantennas oriented in a conformal manner. Utilizing the robust nanoantenna inclusions and benefiting from the powerful analyzing tool, we successfully demonstrate the superior performances of the conformal metasurfaces in two specific areas, with one for lensing and compensation of spherical aberration, and the other carpet cloak, both at 532 nm visible spectrum.
Highlights
Been discussed in the characterization of metasurfaces at the high frequency regime and with conformal shapes where the effective surface currents are not readily available
The platform is extremely large with a curved surface covered by a huge subwavelength nanoantenna array for electromagnetic transformation, making the design and modelling challenging
The conformal metasurface array under such circumstances can be approximated by locally flat inclusions with slow space-variation
Summary
To design the metasurface and evaluate its performance in providing a specific phase discontinuity function on a curvy substrate, we comply with the following procedures: 1) calculate the inhomogeneous phase shift profile for a specific application, and find the discretized phase shift for each meta-element, 2) analyze the incidence angle for each meta-element based on the excitation and the comformal surface shape, and decompose the excitation into s and p modes through global to local coordinate transformation, 3) find the disk diameter and the efficiency of the specific element that fulfills the phase requirement based on the numerical data in Figs 2 and 3, 4) calculate the total electric and magnetic fields on the metasurface, find equivalent surface currents and field distribution based on the field equivalence principle. With the proposed metasurfaces and the developed powerful modelling scheme, manipulating electromagnetic waves in novel ways and for other sophisticated systems can be anticipated
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