Dekel Veksler

Spin-optical metamaterial route to spin-controlled photonics.

Making Metamaterials Controlling the propagation of electromagnetic waves is a key requirement in communication technologies. The components tend to be bulky, however, which can make it difficult to integrate with microelectronics circuits. Using arrays of metallic nanoantennae patterned on a substrate surface, Shitrit et al. (p. 724) fabricated a novel class of metamaterials: anisotropic materials without inversion symmetry. The materials may pave the way to polarization-dependent nanophotonics. Designed arrays of metallic nanoantennas provide a route for the polarization-dependent propagation of light. Spin optics provides a route to control light, whereby the photon helicity (spin angular momentum) degeneracy is removed due to a geometric gradient onto a metasurface. The alliance of spin optics and metamaterials offers the dispersion engineering of a structured matter in a polarization helicity–dependent manner. We show that polarization-controlled optical modes of metamaterials arise where the spatial inversion symmetry is violated. The emerged spin-split dispersion of spontaneous emission originates from the spin-orbit interaction of light, generating a selection rule based on symmetry restrictions in a spin-optical metamaterial. The inversion asymmetric metasurface is obtained via anisotropic optical antenna patterns. This type of metamaterial provides a route for spin-controlled nanophotonic applications based on the design of the metasurface symmetry properties.

Photonic spin-controlled multifunctional shared-aperture antenna array

Multifunction planar optics Specially designed two-dimensional (2D) arrays of nanometer-scale metallic antennas, or metasurfaces, may allow bulky optical components to be shrunk down to a planar device structure. Khorasaninejad et al. show that arrays of nanoscale fins of TiO can function as high-end optical lenses. At just a fraction of the size of optical objectives, such planar devices could turn your phone camera or your contact lens into a compound microscope. Maguid et al. interleaved sparse 2D arrays of metal antennas to get multifunctional behavior from the one planar device structure (see the Perspective by Litchinitser). The enhanced functionality of such designed metasurfaces could be used in sensing applications or to increase the communication capacity of nanophotonic networks. Science, this issue pp. 1190 and 1202; see also p. 1177 A 2D nanophotonic system can be designed with multifunctional optical capability. The shared-aperture phased antenna array developed in the field of radar applications is a promising approach for increased functionality in photonics. The alliance between the shared-aperture concepts and the geometric phase phenomenon arising from spin-orbit interaction provides a route to implement photonic spin-control multifunctional metasurfaces. We adopted a thinning technique within the shared-aperture synthesis and investigated interleaved sparse nanoantenna matrices and the spin-enabled asymmetric harmonic response to achieve helicity-controlled multiple structured wavefronts such as vortex beams carrying orbital angular momentum. We used multiplexed geometric phase profiles to simultaneously measure spectrum characteristics and the polarization state of light, enabling integrated on-chip spectropolarimetric analysis. The shared-aperture metasurface platform opens a pathway to novel types of nanophotonic functionality.

Characterization of Different Wire Configurations in Underwater Electrical Explosion

The results of a study of shock wave (SW) generation by means of underwater electrical wire explosion with different exploding wire configurations and two high-current microsecond and submicrosecond timescale generators are presented. By using aperiodical generator discharge, a ~85% and ~15% of the stored electrical energy was transferred to the exploding wire and energy of the generated water flow, respectively. The energy of the water flow is distributed between its internal (~25%) and kinetic (~75%) energies. It was shown that the exploding wire zigzag configuration, confinement of the SW propagation region, and an increase in the rate of the energy deposition into the exploding wire allow one to increase the SW pressure ges10 times that attained with microsecond timescale straight wire explosion. The averaged thermophysical properties of nonideal and weakly degenerated plasma formed as a result of the wire explosion were obtained and summarized.

Rashba-type plasmonic metasurface

Observation of the plasmonic Rashba effect manifested by a polarization helicity degeneracy removal in a surface wave excitation via an inversion asymmetric metamaterial is reported. By designing the metasurface symmetry using anisotropic nanoantennas with space-variant orientations, we govern the light-matter interaction via the local field distribution arising in a wavelength and a photon spin control. The broken spatial inversion symmetry is experimentally manifested by a directional excitation of surface wave jets observed via a decoupling slit as well as by the quantum dot fluorescence. Rashba-type plasmonic metasurfaces provide a route for spin-based nanoscale devices controlled by the metamaterial symmetry and usher in a new era of light manipulation.

Optical Mode Control by Geometric Phase in Quasicrystal Metasurface.

We report on the observation of optical spin-controlled modes from a quasicrystalline metasurface as a result of an aperiodic geometric phase induced by anisotropic subwavelength structure. When geometric phase defects are introduced in the aperiodic structured surface, the modes exhibit polarization helicity dependence resulting in the optical spin-Hall effect. The radiative thermal dispersion bands from a quasicrystal structure are studied where the observed bands arise from the optical spin-orbit interaction induced by the aperiodic space-variant orientations of anisotropic antennas. The optical spin-flip behavior of the revealed modes that arise from the geometric phase pickup is experimentally observed within the visible spectrum by measuring the spin-projected diffraction patterns. The introduced ability to manipulate the light-matter interaction of quasicrystals in a spin-dependent manner provides the route for molding light via spin-optical aperiodic artificial planar surfaces.

Spinoptical Metamaterials: A Novel Class of Metasurfaces

Photonic metasurfaces are metamaterials with reduced dimensionality composed of engineered subwavelength-scale meta-atoms enabling a custom-tailored electromagnetic response of the medium. These 2-D metastructures are also at the forefront of the physical enigma: What is the effect of surface symmetry properties on light-matter interactions?

Shared-aperture geometric phase metasurfaces

Shared-aperture multifunctional planar systems (in which a number of tasks are performed concurrently) have recently been introduced in the field of phased array antennas, for radar applications.1 Indeed, these shared-aperture phased antenna arrays—see Figure 1(a)—are a promising way to increase functionality in photonics. Recent achievements in the fast-growing field of metasurfaces (i.e., metamaterials of reduced dimensionality) are particularly relevant because they provide a route to developing virtually flat optics. Such metasurfaces consist of a dense arrangement of small-scale resonant optical antennas. For example, in a phased antenna array, phase accumulators are arranged so that they form a wavefront (because of phase differences across the array). Light–matter interactions of individual nanoantennas therefore allow local light scattering properties to be controlled with these arrays. The local phase pickup in a phased antenna array can be manipulated by changing the antenna material, size, shape, and environment (known as antenna resonance shaping), or via the geometric phase concept. The latter concept is fundamental to geometric phase metasurfaces (GPMs), in which the phase pickup originates from space-variant orientations of the anisotropic nanoantennas that compose the metasurface. In addition, the geometric phase concept is an efficient way to achieve spin-controlled phase modulation, whereas the photon spin is associated with the intrinsic angular momentum of light.2–8 GPMs can also be used to transform incident circularly polarized light into a beam of opposite helicity (imprinted with a geometric phase). In our work,9 we have used a new technique to synthesize shared-aperture phased antenna arrays. We combine these arrays with the geometric phase concept to realize multifunctional GPM photonic arrays. In addition, we have incorporated Figure 1. Schematic illustrations of (a) the shared-aperture concept and (b) structured wavefronts emerging from an interleaved geometric phase metasurface. In (a) each wavefront is represented by a different color. The wavefronts are illustrated with solid lines and the dashed lines indicate the propagation directions.

Molding Surface Plasmons by Spinoptical Rashba Metasurfaces

We report on a spin-based surface plasmon directional excitation by spinoptical Rashba metasurfaces. The light-matter interaction control via the geometric design of the metasurface symmetry ushers in a new era of light manipulation.

Spinoptical metamaterials: Symmetry violation route to spin-based photonics

We report on spinoptical metamaterials manifested by spin-controlled optical modes, where the inversion symmetry is violated. The metasurface symmetry properties design via nanoantennas is a starting point for spin-based nanophotonic applications.

Spinoptical metamaterials: spin-controlled photonics based on symmetry violation

Spinoptics provides a route to control light, whereby the photon helicity (spin angular momentum) degeneracy is removed due to a geometric gradient onto a metasurface. The alliance of spinoptics and metamaterials offers the dispersion engineering of a structured matter in a polarization helicity dependent manner. We show that polarization-controlled optical modes of metamaterials arise where the spatial inversion symmetry is violated. The emerged spin-split dispersion of spontaneous emission originates from the spin-orbit interaction of light, generating a selection rule based on symmetry restrictions in a spinoptical metamaterial. The inversion asymmetric metasurface is obtained via anisotropic optical antenna patterns. This type of metamaterial provides a route for spin-controlled nanophotonic applications based on the design of the metasurface symmetry properties.