Advancing an Optical Metasurface (OMS) platform with dynamic adjustability and rapid response times strongly aligns with the current trends in photonics. Firstly, we demonstrate an electrically driven MEMS-OMS-based dynamic linear polarizer (DLP), benefiting from a tunable hybrid plasmonic Fabry-Pérot (FP) cavity formed by an anisotropic plasmonic OMS and thin-film piezoelectric MEMS mirror and featuring a continuous and tunable, in a fast and reversible fashion, Extinction Ratio (ER) between two linearly polarized incident beams. DLP-based dynamic grayscale imaging and Vector Vortex Beam (VVB) generation have also been realized. Secondly, we embark on an in-depth exploration of optical Exceptional Points (EPs) within a fully electrically tunable non-Hermitian metasurface platform that leverages the synergistic interplay between chiral gold meta-atoms with a piezoelectric MEMS mirror, thereby allowing for fine-detuning the system to construct a voltage-controlled spectral space. We demonstrate a voltage-controlled topological phase transition, transforming a chiral EP to a Diabolic Point (DP) characterized by degenerate eigenvalues and orthogonal eigenstates.
KEYWORDS: Antennas, Diffraction, Reflection, Gold, Design and modelling, Beam steering, Electric fields, Near field optics, Beam splitters, Simulations
Electrically connected optical metasurfaces with high efficiencies are crucial for developing spatiotemporal metadevices with ultrahigh spatial and ultrafast temporal resolutions. While efficient metal–insulator–metal (MIM) metasurfaces containing discretized meta-atoms require additional electrodes, Babinet-inspired slot-antenna-based plasmonic metasurfaces suffer from low efficiencies and limited phase coverage for copolarized optical fields. Capitalizing on the concepts of conventional MIM and slot-antenna metasurfaces, we design and experimentally demonstrate a new type of optical reflective metasurfaces consisting of mirror-coupled slot antennas (MCSAs). By tuning the dimensions of rectangular-shaped nanoapertures atop a dielectric-coated gold mirror, we achieve efficient phase modulation within a sufficiently large range of 320 deg and realize functional phase-gradient metadevices for beam steering and beam splitting in the near-infrared range. The fabricated samples show (22 % ± 2 % ) diffraction efficiency for beam steering and (17 % ± 1 % ) for beam splitting at the wavelength of 790 nm. The considered MCSA configuration, dispensing with auxiliary electrodes, offers an alternative and promising platform for electrically controlled reflective spatiotemporal metasurfaces.
The capability to manipulate the polarization state of light at the nanoscale is of paramount importance in many emerging research areas ranging from optical communication to quantum information processing. Gap-surface plasmon (GSP) metasurfaces, which provide unprecedented advantages and abilities of molding reflected fields, have been demonstrated excellently suited for integration of multifunctional polarization optics into a single device. Here, we establish a versatile GSP metasurface platform based on nanoscale quarter-wave plates (nano-QWPs) that enable efficient circular-to-linear polarization conversion along with the complete phase control over reflected fields. Capitalizing on the nano-QWP design, we demonstrate, both theoretically and experimentally, how resonance and geometric phases can be used in concert to achieve independent and simultaneous phase modulation of both co- and cross-polarized circularly polarized (CP) waves by realizing arbitrary beam steering of co- and cross-polarized CP channels in a broadband near-infrared range. The GSP metasurface platform established in our work provides versatile and flexible solutions to enrich multiple functionalities for diversified metasurface-based polarization optics exploited in modern integrated photonic devices and systems.
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