Optically-Triggered Nanoscale Memory Effect in a Hybrid Plasmonic-Phase Changing Nanostructure

Nanoscale devices, such as all-optical modulators and electro-optical transducers, can be implemented in heterostructures that integrate plasmonic nanostructures with functional active materials. Here we demonstrate all-optical control of a nanoscale memory effect in such a heterostructure by coupling the localized surface plasmon resonance (LSPR) of gold nanodisk arrays to a phase-changing material (PCM), vanadium dioxide (VO<inf>2</inf>). By latching the VO<inf>2</inf> in a distinct correlated metallic state during the insulator-to-metal transition (IMT), while concurrently exciting the hybrid nanostructure with one or more ultraviolet optical pulses, the entire phase space of this correlated state can be accessed optically to modulate the plasmon response. We find that the LSPR modulation depends strongly but linearly on the initial latched state, suggesting that the memory effect encoded in the plasmon resonance wavelength is linked to the strongly correlated electron states of the VO<inf>2</inf>. The continuous, linear variation of the electronic and optical properties of these model heterostructures opens the way to multiple design strategies for hybrid devices with novel optoelectronic functionalities, which can be controlled by an applied electric or optical field, strain, injected charge, or temperature.Department of Applied Physic

Electrodeposition of silver amalgam particles on ITO – Towards novel electrode material

© 2017 Elsevier B.V. Silver solid amalgam represents up to now the most suitable alternative electrode material to metallic mercury in electroanalytical chemistry. Controlled electrodeposition of variable (sub)micrometer-sized silver amalgam particles (AgAP) on the surface of transparent indium-tin oxide (ITO) electrode from an electrolyte containing Ag+ and Hg2+ ions is reported here, as a novel perspective method suitable for preparation of nano-structured silver amalgam electrode material. Elemental analysis of the composition and morphology of the AgAP decorating the ITO was studied by scanning electron microscopy including energy-disperse X-ray spectroscopy and by image processing software. Particle composition, size, and surface coverage are controllable by selection of the Ag+/Hg2+ ratio in the electrodeposition solution and by setting of individual parameters of applied double pulsed/potential chronoamperometry. Applicable potential window of thus prepared ITO-AgAP electrode was found to be within +0.2 to −1.0 V in 0.2 acetate buffer pH 5.0. Utilized voltammetric and chronoamperometric methods revealed significant enhancement in electrochemical reducibility of selected model organic nitro-compound (shift of the peak potential about 300 mV to more positive potentials). Its further employment in UV/Vis spectroelectrochemical cell provided information about number of consumed electrons and kinetic characteristics. Furthermore preferential adsorption of calf thymus DNA at AgAP than ITO was observed by fluorescence microscopy indicating its potential applicability in (bio-)spectroelectrochemical methods. Further advantages and potential applications are also proposed and discussed

Optically tunable mie resonance VO2 nanoantennas for metasurfaces in the visible

Metasurfaces are ultrathin nanostructured surfaces that can allow arbitrary manipulation of light. Implementing dynamic tunability into their design could allow the optical functions of metasurfaces to be rapidly modified at will. The most pronounced and robust tunability of optical properties is provided by phase-change materials such as vanadium dioxide (VO2) and germanium antimony telluride (GST), but their implementations have been limited only to near-infrared wavelengths. Here, we demonstrate that VO2 nanoantennas with widely tunable Mie resonances can be utilized for designing tunable metasurfaces in the visible range. In contrast to the dielectric-metallic VO2 phase transition-induced tunability in previous demonstrations, we show that persisting dielectric Mie resonances in VO2 nanoantennas offer remarkable scattering and extinction modulation depths (5–8 dB and 1–3 dB, respectively) for tunability in the visible. Moreover, these strong resonances are optically switchable using a continuous-wave laser. Our results establish VO2 nanostructures as low-loss building blocks of optically tunable metasurfaces

Babinet’s principle for disc-shaped plasmonic antennas

Resumen del trabajo presentado a la International Conference on Nanoscience + Technology (ICN+T), celebrada en Brno (Czech Republic) del 22 al 27 de julio de 2018.Babinet’s principle relates the optical response of apertures in thin films and their complementary analogues – solid barriers or particles. Originating in the wave theory of light and analysis of diffraction, it has recently entered the field of plasmonics. According to Babinet’s principle, localized surface plasmons in complementary particles and apertures have identical resonance energies and their near field are closely linked: The electric field distribution of a specific in-plane polarization for an aperture corresponds to the magnetic field distribution of perpendicular polarization for a particle. On the other hand, substantial differences can be related to different fabrication processes and experimental techniques involved in the characterization of real structures.Peer reviewe

Near-field digital holography: A tool for plasmon phase imaging

© 2018 The Royal Society of Chemistry. The knowledge of the phase distribution of the near electromagnetic field has become very important for many applications. However, its experimental observation is still technologically a very demanding task. In this work, we propose a novel method for the measurement of the phase distribution of the near electric field based on the principles of phase-shifting digital holography. In contrast to previous methods the holographic interference occurs already in the near field and the phase distribution can be determined purely from the scanning near-field optical microscopy measurements without the need for additional far-field interferometric methods. This opens a way towards on-chip phase imaging. We demonstrate the capabilities of the proposed method by reconstruction of the phase difference between interfering surface plasmon waves and by imaging the phase of a single surface plasmon wave. We also demonstrate a selectivity of the method towards individual components of the field

Effect of deposition angle on fabrication of plasmonic gold nanocones and nanodiscs

Sem informaçãoMetal nanocones can exhibit several strong plasmonic resonances, which are associated with intense and accessible electromagnetic hot spots. They can thus be used to enhance light-matter interactions or to facilitate location-specific sensing while enabli22816Sem informaçãoSem informaçãoSem informaçãoThis research was carried out under project GA17-33767L of Grant Agency of the Czech Republic, H2020 Twinning programme (project SINNCE, 810626) and Brno University of Technology (project FSI-S-17-4482). The work was also supported by the project CEITEC

Epitaxial VO<inf>2</inf> Nanostructures: A Route to Large-Scale, Switchable Dielectric Metasurfaces

Copyright © 2018 American Chemical Society. Metasurfaces offer unparalleled functionalities for controlling the propagation and properties of electromagnetic waves. But to transfer these functions to technological applications, it is critical to render them tunable and to enable fast control by external stimuli. In most cases, this has been realized by utilizing tunable materials combined with a top-down nanostructuring process, which is often complicated and time intensive. Here we present a novel strategy for fabricating a tunable metasurface comprising epitaxially grown nanobeams of a phase transition material, vanadium dioxide. Without the need for extensive nanolithographic fabrication, we prepared a large-area (>1 cm2), deep-subwavelength (thickness of ∼Λ/40) nanostructured thin film that can control light transmission with large modulation depth, exceeding 9 dB across all telecommunication wavelength bands. Furthermore, the transmission in the "on" state remains higher than 80% from near- to mid-infrared region. This renders our metasurface useful also as a phase-shifting element, which we demonstrate by carrying out cross-polarized transmission measurements. To provide insights about the relationship between metasurface morphology and its resulting optical properties, we perform full-field three-dimensional numerical simulations as a function of width, height, and edge-to-edge separation of the epitaxial VO2 nanobeams