title: Holographic free-electron light source.
abstract: Recent advances in the physics and technology of light generation via free-electron proximity and impact interactions with nanostructures (gratings, photonic crystals, nano-undulators, metamaterials and antenna arrays) have enabled the development of nanoscale-resolution techniques for such applications as mapping plasmons, studying nanoparticle structural transformations and characterizing luminescent materials (including time-resolved measurements). Here, we introduce a universal approach allowing generation of light with prescribed wavelength, direction, divergence and topological charge via point-excitation of holographic plasmonic metasurfaces. It is illustrated using medium-energy free-electron injection to generate highly-directional visible to near-infrared light beams, at selected wavelengths in prescribed azimuthal and polar directions, with brightness two orders of magnitude higher than that from an unstructured surface, and vortex beams with topological charge up to ten. Such emitters, with micron-scale dimensions and the freedom to fully control radiation parameters, offer novel applications in nano-spectroscopy, nano-chemistry and sensing.
authors.affiliation: Optoelectronics Research Centre &Centre for Photonic Metamaterials, University of Southampton, Southampton SO17 1BJ, UK.|National Key Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 200083, China.
authors.forename: Guanhai
authors.initials: G
authors.lastname: Li
authors.affiliation: Optoelectronics Research Centre &Centre for Photonic Metamaterials, University of Southampton, Southampton SO17 1BJ, UK.
authors.forename: Brendan P
authors.initials: BP
authors.lastname: Clarke
authors.affiliation: Optoelectronics Research Centre &Centre for Photonic Metamaterials, University of Southampton, Southampton SO17 1BJ, UK.|Centre for Disruptive Photonic Technologies, School of Physical and Mathematical Sciences &The Photonics Institute, Nanyanag Technological University, Singapore 637371, Singapore.
authors.forename: Jin-Kyu
authors.identifier: 0000-0003-0416-7513
authors.initials: JK
authors.lastname: So
authors.affiliation: Optoelectronics Research Centre &Centre for Photonic Metamaterials, University of Southampton, Southampton SO17 1BJ, UK.
authors.forename: Kevin F
authors.initials: KF
authors.lastname: MacDonald
authors.affiliation: Optoelectronics Research Centre &Centre for Photonic Metamaterials, University of Southampton, Southampton SO17 1BJ, UK.|Centre for Disruptive Photonic Technologies, School of Physical and Mathematical Sciences &The Photonics Institute, Nanyanag Technological University, Singapore 637371, Singapore.
authors.forename: Nikolay I
authors.initials: NI
authors.lastname: Zheludev