title: Metafocusing by a Metaspiral Plasmonic Lens.
abstract: We designed and realized a metasurface (manipulating the local geometry) spiral (manipulating the global geometry) plasmonic lens, which fundamentally overcomes the multiple efficiency and functionality challenges of conventional in-plane plasmonic lenses. The combination of spirality and metasurface achieves much more efficient and uniform linear-polarization-independent plasmonic focusing. As for functionality, under matched circularly polarized illumination the lens directs all of the power coupled to surface plasmon polaritons (SPPs) into the focal spot, while the orthogonal polarization excites only diverging SPPs that do not penetrate the interior of the lens, achieving 2 orders of magnitude intensity contrast throughout the entire area of the lens. This optimal functional focusing is clearly demonstrated by near-field optical microscopy measurements that are in excellent agreement with simulations and are supported by a detailed theoretical interpretation of the underlying mechanisms. Our results advance the field of plasmonics toward functional detection and the employment of SPPs in smart pixels, near-field microscopy, lithography, and particle manipulation.
authors.affiliation: Department of Electrical Engineering, Technion, Israel Institute of Technology , 32000 Haifa, Israel.
authors.forename: Grisha
authors.initials: G
authors.lastname: Spektor
authors.affiliation: Department of Electrical Engineering, Technion, Israel Institute of Technology , 32000 Haifa, Israel.
authors.forename: Asaf
authors.initials: A
authors.lastname: David
authors.affiliation: Department of Electrical Engineering, Technion, Israel Institute of Technology , 32000 Haifa, Israel.
authors.forename: Bergin
authors.initials: B
authors.lastname: Gjonaj
authors.affiliation: Department of Electrical Engineering, Technion, Israel Institute of Technology , 32000 Haifa, Israel.
authors.forename: Guy
authors.initials: G
authors.lastname: Bartal
authors.affiliation: Department of Electrical Engineering, Technion, Israel Institute of Technology , 32000 Haifa, Israel.
authors.forename: Meir
authors.initials: M
authors.lastname: Orenstein
mesh_terms: D004867:Equipment Design; D007909:Lenses; D008027:Light; D012542:Scattering, Radiation; D020349:Surface Plasmon Resonance / Q000295:instrumentation*; D013499:Surface Properties
keywords: Plasmonics; functional focusing; metasurface; plasmonic focusing; plasmonic lens