Ori Avayu

Aluminum Nanoantenna Complexes for Strong Coupling between Excitons and Localized Surface Plasmons

We study the optical dynamics in complexes of aluminum nanoantennas coated with molecular J-aggregates and find that they provide an excellent platform for the formation of hybrid exciton-localized surface plasmons. Giant Rabi splitting of 0.4 eV, which corresponds to ∼10 fs energy transfer cycle, is observed in spectral transmittance. We show that the nanoantennas can be used to manipulate the polarization of hybrid states and to confine their mode volumes. In addition, we observe enhancement of the photoluminescence due to enhanced absorption and increase in the local density of states at the exciton-localized surface plasmon energies. With recent emerging technological applications based on strongly coupled light-matter states, this study opens new possibilities to explore and utilize the unique properties of hybrid states over all of the visible region down to ultraviolet frequencies in nanoscale, technologically compatible, integrated platforms based on aluminum.

Metasurfaces based dual wavelength diffractive lenses

We demonstrate experimentally and by simulations a method for using thin nanostructured plasmonic metasurfaces to design diffractive Fresnel zone plate lenses that focus pairs of wavelengths to a single focal point. The metasurfaces are made of tightly packed cross and rod shaped optical nanoantennas with strong polarization and wavelength selectivity. This selectivity allows multiplexing two different lenses with low spectral crosstalk on the same substrate and to address any superposition of the two colors at the focus of the lenses by controlling the polarization of light. This concept can open the door to use ultrathin diffractive lenses in fluorescence microscopy and in stimulated emission depletion microscopy.

Composite functional metasurfaces for multispectral achromatic optics

Nanostructured metasurfaces offer unique capabilities for subwavelength control of optical waves. Based on this potential, a large number of metasurfaces have been proposed recently as alternatives to standard optical elements. In most cases, however, these elements suffer from large chromatic aberrations, thus limiting their usefulness for multiwavelength or broadband applications. Here, in order to alleviate the chromatic aberrations of individual diffractive elements, we introduce dense vertical stacking of independent metasurfaces, where each layer is made from a different material, and is optimally designed for a different spectral band. Using this approach, we demonstrate a triply red, green and blue achromatic metalens in the visible range. We further demonstrate functional beam shaping by a self-aligned integrated element for stimulated emission depletion microscopy and a lens that provides anomalous dispersive focusing. These demonstrations lead the way to the realization of ultra-thin superachromatic optical elements showing multiple functionalities—all in a single nanostructured ultra-thin element.

Tomographic study of atomic-scale redistribution of platinum during the silicidation of Ni0.95Pt0.05/Si(100) thin films

Atom-probe tomography was utilized to study the distribution of Pt after silicidation of a solid-solution Ni0.95Pt0.05 thin film on Si(100). Direct evidence of Pt short-circuit diffusion via grain boundaries, Harrison’s type-B regime, is found after silicidation to form (Ni0.99Pt0.01)Si. This underscores the importance of interfacial phenomena for stabilizing this low-resistivity phase, providing insights into the modification of NiSi texture, grain size, and morphology caused by Pt. Platinum segregates at the (Ni0.99Pt0.01)Si/Si(100) interface, which may be responsible for the increased resistance of (Ni0.99Pt0.01)Si to agglomeration. The relative shift in work function between as-deposited and annealed states is greater for Ni(Pt)Si than for NiSi.

Optical metasurfaces for polarization-controlled beam shaping

We have developed multifunctional optical beam shapers based on plasmonic metasurfaces. The metasurfaces are composed of subwavelength-spaced polarization- and wavelength-selective optical nanoantennas that allow encoding several beam shapers on a single element. We demonstrate numerically and experimentally beam shapers that can be used to switch between arbitrary beam shapes. We specifically demonstrate switching between one-dimensional Airy and Gaussian beams, Hermite-Gaussian beams of different orders, and two-dimensional Airy and Bessel beams. These beam shapers can be used as integrated optical elements in applications that require more than one laser beam shape.

Polarization controlled coupling and shaping of surface plasmon polaritons by nanoantenna arrays

We demonstrate experimentally the use of ordered arrays of nanoantennas for polarization controlled plasmonic beam shaping and excitation. Rod- and cross-shaped nanoantennas are used as local point-like sources of surface plasmon polaritons, and the desired phase of the generated plasmonic beam is set directly through their spatial arrangement. The polarization selectivity of the optical nanoantennas allows us to further control the excitation, enabling the realization of a variety of complex and functional plasmonic beam shaping elements. We demonstrate this concept by generating plasmonic self-accelerating beams, plasmonic bottle beams, and switchable dual-focii plasmonic lenses. The freedom in the design and arrangement of these nanoantennas enables us to specifically tailor and control the shapes, wavelengths, and coupling efficiencies of complex plasmonic beams.

Three-Dimensional Atom-Probe Tomographic Studies of Nickel Monosilicide/Silicon Interfaces on a Subnanometer Scale

Three-dimensional atom-probe tomography was utilized to study the distribution of M (M = Pt or Pd) after silicidation of a solid-solution Ni0.95M0.05 thin-film on Si(100). Both Pt and Pd segregate at the (Ni1-xMx)Si/Si(100) heterophase interface and may be responsible for the increased resistance of (Ni1-xMx)Si to agglomeration at elevated temperatures. Direct evidence of Pt short-circuit diffusion via grain boundaries, Harrison regime-B, is found after silicidation to form (Ni0.99Pt0.01)Si. This underscores the importance of interfacial phenomena in stabilizing this low-resistivity phase, providing insights into the modification of NiSi texture, grain size, and morphology caused by Pt. The relative shift in work function between as-deposited and annealed states is greater for Ni(Pt)Si than for NiSi as determined by Kelvin probe force-microscopy. The nickel monosilicide/Si heterophase interface is reconstructed in three-dimensions and its chemical roughness is evaluated.

Ultrathin full color visor with large field of view based on multilayered metasurface design

An augmented reality display system based on an ultra-thin see-through stacked metasurface near eye visor is proposed. We use the unique capabilities of plasmonic metasurfaces to control light at the subwavelength scale and design a see-through diffractive element that can project a full color image from a micro-display into the eye. This element is comprised of three metasurface layers, each designed to diffract only a specific wavelength and keep the rest of the visible spectrum unaffected. By implementing this layered design we can harness the advantages of diffractive optics and reduce their chromatic aberrations. We present here the design process of the proposed metasurface near eye visor and validate it by fabricating and testing a proof of concept sample.

Exciton-plasmon hybridization in J-aggregate-aluminum nanoantenna metasurfaces

We find that aluminum nanoantennas provide an excellent platform for the formation of hybrid exciton-localized surface plasmon modes. We show that the hybrid states can be polarized, and that they enhance the photoluminesence of the system.