Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session X32: Plasmonics and Beyond IV: Single particle dynamicsFocus
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Sponsoring Units: DCP Chair: Hrvje Petek, University of Pittsburgh Room: 332 |
Friday, March 18, 2016 8:00AM - 8:12AM |
X32.00001: Plasmonic nano-focused four-wave mixing for femtosecond nano-imaging Vasily Kravtsov, Ronald Ulbricht, Joanna Atkin, Markus Raschke We experimentally demonstrate efficient and broadband nonlinear optical four-wave mixing (FWM) in a deep sub-wavelength volume using adiabatic nanofocusing of surface plasmon polaritons (SPPs). We couple few-femtosecond laser pulses into SPPs that propagate and experience nanofocusing on a sharp Au tip, and detect blue-shifted intra-pulse FWM response of the nanofocused plasmons. Due to the asymptotic mode volume compression and resulting steep increase in SPP field enhancement when approaching the tip apex, the nonlinear signal is highly localized in a nanoscopic volume at the apex. The simultaneous enhanced generation and further FWM field compression into the tip apex provides for a highly sensitive nano-probe for ultrafast near-field microscopy and spectroscopy. We demonstrate the use of the nano-localized nonlinear frequency conversion to spatially resolve few-femtosecond dynamics in ultrafast coherent spatio-temporal nano-imaging of the localized plasmonic modes of an inhomogeneous Au layer edge. Our results are supported by simulations and provide a perspective for an all-optical implementation of the novel multidimensional nano-spectroscopies. [Preview Abstract] |
Friday, March 18, 2016 8:12AM - 8:48AM |
X32.00002: Femtosecond Snapshots of quantum mechanics at work in plasmonic nano-structures. Invited Speaker: Fabrizio Carbone Ultrafast Transmission Electron Microscopy enabled a new technique (Photon-Induced Near Field Electron Microscopy, PINEM), capable of controlling electromagnetic fields confined on the surface of nanostructures and image their properties with nm-resolution in direct space and fs resolution in time. In this presentation, we will show some recent results where the standing wave formed by the plasmonic field confined on the surface of one silver nano-wire was imaged together with its energy exchange with the imaging electrons. In these results, both the interference and the quantization of the plasmonic near field could be imaged simultaneously, revealing both a quantum and a classical aspect of the electromagnetic field in one snapshot. The implications of these results will be discussed, and we will also present new ideas and methodologies to go beyond such an experiment and image the interaction between single electrons and single plasmons. We will also show that shaping the electron density in a thin film via light pulses is possible by taking advantage of the plasmon-plasmon interference and the ability of light polarization to control the excitation of different plasmonic field geometries in ad hoc designed nanostructures. Movies of the propagation of plasmons will also be presented, providing insights into their speed, propagation losses and the effect of confinment. [Preview Abstract] |
Friday, March 18, 2016 8:48AM - 9:24AM |
X32.00003: Ultrafast Nonlinear Plasmonics of Single Nano-Objects Invited Speaker: Natalia Del Fatti Investigating, understanding and modeling the physical properties of nano-objects are intense fields of research. Of particular interest are metal-based nano-objects, where their morphology and environment dependent surface plasmon resonances (SPR) have been extensively exploited to design new optical systems. As a SPR is associated to electromagnetic local field enhancement in the nano-object, it also leads to enhancement of its optical nonlinearity, opening many possibilities for investigating fundamental processes at nanoscale [1]. Most of these studies were performed on large ensembles of nano-objects, providing mean information which impedes detailed comparison between experimental data and theoretical models. With the advance of single nanoparticle spectroscopy methods, the linear and nonlinear responses of a single nano-object can now be addressed, which, associated to determination of its morphology by electron microscopy, opens the way to their quantitative modeling [2]. In this context we discuss experimental and theoretical investigations of the ultrafast response of individual model nano-objects, either formed by a single particle (gold nanorod) or by two particles at a nanometric distance (gold-silver nano-dimer). Results obtained in gold nanorods are in excellent quantitative agreement with a model computing the change of the metal dielectric function due to ultrafast electron heating and relaxation. This shows that the nonlinear response of a metal nano-object can be fully described as that of the bulk metal enhanced by plasmonic effects. Extension of these studies to more complex nano-objects, as nano-dimers formed by two different materials, permits analysis of the impact of their interaction. We demonstrate here the existence of Fano effect in the absorption of a single Ag-Au dimer, experimentally proving previous theoretical predictions [3]. Furthermore, we show that ultrafast pump-probe nonlinear spectroscopy permits to selectively address at nanoscale only one of the components of a dimer, paving the way toward quantitative investigations of energy and charge exchanges in multi-material nano-objects. [1] F. Vall\'{e}e and N. Del Fatti, in ``Plasmonics: theory and applications'', eds. T.Shahbazyan {\&} M.Stockman, Springer, p. 167 (2013) [2] A. Crut, P. Maioli, N. Del Fatti and F. Vall\'{e}e, Chem. Soc. Rev. \underline {43}, 3921 (2014) [3] G. Bachelier, I. Russier-Antoine, E. Benichou, C. Jonin, N. Del Fatti, F. Vall\'{e}e, P.F. Brevet, Phys. Rev. Lett. \underline {101}, 197401 (2008). [Preview Abstract] |
Friday, March 18, 2016 9:24AM - 10:00AM |
X32.00004: Dirac single particle and plasmon excitations in topological insulators Invited Speaker: Stefano Lupi Topological Insulators (TIs), like Bi2Se3 and Bi2Te3, are one of the most intriguing issues at focus in Condensed Matter Physics. TIs exhibit a band gap in the bulk like ordinary insulators, but have intrinsic 2D conducting states on their edge and surface. This means that the topology, associated with the electronic wavefunctions of the system, changes discontinuously when passing from the bulk to the surface. The edge states arise from a strong spin-orbit coupling, and they are backscattering protected, i.e. not sensitive to disorder (except that coming from magnetic impurities). Such as graphene, TIs surface charge transport is carried out by Dirac fermions, with a very high surface carrier density (n $\ge $ 10$^{\mathrm{13}}$ cm$^{\mathrm{-2}})$, compared to typical values on metal surfaces. Apart single particle excitations, Dirac fermions in TIs sustain exotic plasmonic (collective) modes whose properties of tunability and temperature dependence can be used for photonics applications at the nanoscale. Moreover, unlike plasmons in metals, Dirac plasmons in TIs are expected to be strongly affected by an external magnetic field B due to fact that the cyclotron frequency is comparable to the the plasmon frequency, in particular when plasmons are engineered in the terahertz region of the electromagnetic spectrum. In this talk, after a general review on the properties of Topological Insulators, I will discuss the terahertz linear response of Dirac plasmons in TIs and their behavior under a strong magnetic field up to 30 T. The appearance of strong non-linear optical effects, when the THz electric field reaches values on the order of 1 MV/cm, will be also discussed. In the second part of the talk, I will discuss the sub-ps dynamics of Dirac single-particle and collective excitations as measured by optical-pump THz-probe experiments. Both the steady state and time-resolved experiments provide a unifying picture of single particle and collective electronic excitations in Topological Insulators. [Preview Abstract] |
Friday, March 18, 2016 10:00AM - 10:36AM |
X32.00005: Quantum Plasmonics with Free Electrons Invited Speaker: Javier Garcia de Abajo Fast electrons offer the means to excite and probe plasmons with an unparalleled combination of space and energy resolutions. In particular, electron energy-loss and cathodoluminescence spectral microscopies are widely used to obtain snapshots of these excitations. Additionally, access to ultrafast plasmon dynamics is possible by recording photoelectrons excited with femtosecond light pulses, while recent experiments demonstrate optical pumping followed by electron-beam probing with similar temporal resolution. In this talk, we will review recent highlights of these techniques and present a unified theoretical description. We will further discuss some exciting phenomena enabled by the quantum nature of the electron-plasmon interaction, including quantum nonlinearities, electron-plasmon entanglement, and vacuum fluctuations. Emphasis will be placed on the potential application of these phenomena for improving and extending spectrally resolved electron microscopy, as well as for on-demand creating and probing of plasmons in integrated devices. [Preview Abstract] |
Friday, March 18, 2016 10:36AM - 10:48AM |
X32.00006: ABSTRACT MOVED TO M1.000376 |
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