Bifunctional gap-plasmon metasurfaces for visible light: polarization-controlled unidirectional surface plasmon excitation and beam steering at normal incidence

Abstract

Integration of multiple diversified functionalities into a single, planar and ultra-compact device has become an emerging research area with fascinating possibilities for realization of very dense integration and miniaturization in photonics that requires addressing formidable challenges, particularly for operation in the visible range. Here we design, fabricate and experimentally demonstrate bifunctional gap-plasmon metasurfaces for visible light, allowing for simultaneous polarization-controlled unidirectional surface plasmon polariton (SPP) excitation and beam steering at normal incidence. The designed bifunctional metasurfaces, consisting of anisotropic gap-plasmon resonator arrays, produce two different linear phase gradients along the same direction for respective linear polarizations of incident light, resulting in distinctly different functionalities realized by the same metasurface. The proof-of-concept fabricated metasurfaces exhibit efficient (>25% on average) unidirectional (extinction ratio >20 dB) SPP excitation within the wavelength range of 600–650 nm when illuminated with normally incident light polarized in the direction of the phase gradient. At the same time, broadband (580–700 nm) beam steering (30.6°–37.9°) is realized when normally incident light is polarized perpendicularly to the phase gradient direction. The bifunctional metasurfaces developed in this study can enable advanced research and applications related to other distinct functionalities for photonics integration.

Dynamic Metasurfaces Using Phase‐Change Chalcogenides

“…Indeed, to meet the ever‐increasing demand for storage capacity and information processing speed, combining multiple diversified functionalities into a single device has become a relentless pursuit for the researchers in the nanophotonics community. For metasurfaces, so far a variety of approaches such as polarization‐multiplexing, wavelength‐multiplexing, and space‐multiplexing have been developed to achieve passive multifunctionalities. Therefore, it is highly desired to combine these multifunctional metasurfaces with phase‐changing chalcogenides, which could add a further degree of freedom to extend the functionalities.…”

Multifunctional Metasurfaces Based on the “Merging” Concept and Anisotropic Single-Structure Meta-Atoms

“…Reproduced from [93] with permission. (e) The working principle of similar type of bi-functional metasurface operating for visible light realized in [94]. The top panel shows the schematic of the unit cell consisting of an Ag nanobrick (grey) on top of a spacer (green) and Ag substrate.…”

“…The top panel shows the schematic of the unit cell consisting of an Ag nanobrick (grey) on top of a spacer (green) and Ag substrate. Reproduced from [94] with permission. SPPs, surface plasmon polaritons.…”

High-efficiency terahertz spin-decoupled meta-coupler for spoof surface plasmon excitation and beam steering

“…In addition, at visible wavelength, Ding et.al. use gap-plasmon metasurfaces to implement polarizationcontrolled unidirectional SP excitation and beam steering at normal incidence [33]. Similarly, polarization-switchable multi-functional metasurface for focusing and SP excitation are also designed by Ling et.al.…”