Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session B2: Focus Session: Quantum Control of Molecular, Nano, and Plasmonic Materials I |
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Sponsoring Units: DCP Chair: Yossi Paltiel, Hebrew University Room: 102 |
Monday, March 3, 2014 11:15AM - 11:51AM |
B2.00001: Real-time observation of ultrafast Rabi oscillations between excitons and plasmons in J-aggregate/metal hybrid nanostructures Invited Speaker: Christoph Lienau Surface plasmon polaritons (SPPs), optical excitations at the interface between a metal and a dielectric, carry significant potential for guiding and manipulating light on the nanoscale. Their weak optical nonlinearities, however, hinder active device fabrication, $e.g.$, for all-optical switching or information processing. Recently, strong optical dipole coupling between SPPs and nonlinear quantum emitters with normal mode splittings of up to 700 meV has been demonstrated [1,2]. The predicted ultrafast energy transfer between quantum emitters and SPP fields could be a crucial microscopic mechanism for switching light by light on the nanoscale. Here, we present the first real-time observation of ultrafast Rabi oscillations in a J-aggregate/metal nanostructure, evidencing coherent energy transfer between excitonic quantum emitters and SPP fields. We demonstrate coherent manipulation of the coupling energy by controlling the exciton density on a 10-fs timescale, a step forward towards coherent, all-optical ultrafast plasmonic circuits and devices. [Preview Abstract] |
Monday, March 3, 2014 11:51AM - 12:03PM |
B2.00002: Nonlinear optics of hybrid nano-materials under strong coupling conditions Maxim Sukharev Modern optics fueled with both tremendous advances in nano-fabrication and laser physics is currently experiencing significant growth. We are presently witnessing a unique situation - the research centered at interaction of matter with electromagnetic radiation is fully diving into nanoscale, where one considers purely quantum systems optically driven by nano-materials. The possibilities are vast ranging from fundamental ideas on single atom/molecule optical manipulation, through control of light far below the diffraction limit, to optical engineering and photonic circuitry. Despite progress, the research in optics of quantum media coupled to nano- materials is not complete. Many recent works consider just several quantum emitters driven by near-fields altered by plasmonic materials with a few very promising attempts to include collective effects, which as I will show in this talk play a pivotal role in quantum optics of nano-materials. I will discuss general concepts of nano- plasmonics (one of the most promising sub-fields of nano-optics) with several examples ranging from linear spectroscopy to nonlinear transient absorption. [Preview Abstract] |
Monday, March 3, 2014 12:03PM - 12:15PM |
B2.00003: Ultrafast Coherent Nanoscopy and Control of Plasmonic Nanostructures Dmitri Voronine, Charles Ballmann, Alexei Sokolov Space-time-resolved nonlinear optical spectroscopy with nanoscale spatial and femtosecond temporal resolution may provide structural and dynamical information of various ultrafast processes such as energy and electron transfer, protein folding, etc. Theoretical analysis of tip-enhanced coherent anti-Stokes Raman scattering (TECARS) using a new plasmonic nanostructure is presented. Two tips are used to provide near-field enhancement and control of the nanoantenna response. TECARS signals from different hot spots are obtained by laser pulse shaping and tip manipulation. Various applications of time-resolved surface-enhanced coherent Raman spectroscopy and strategies for manipulating the spectra are discussed. [Preview Abstract] |
Monday, March 3, 2014 12:15PM - 12:27PM |
B2.00004: Coherent Field Emission by Superfocused Plasmons Julia Majors, Alejandro Rodriguez Perez, Joonhee Lee, V. Ara Apkarian Field emission takes place upon focusing propagating surface plasmon polaritons (SPP) at the apex of a sharp metal tip. The effect is demonstrated with remotely launched SPPs on a silver probe tip. We couple femtosecond laser pulses through a grating inscribed on the taper of a smooth, silver wire 30um from the apex. Field-emitted current is directly correlated with the radiation of the super-focused SPP at the apex. Both current and radiation at the apex are measured as a function of incident polarization on the grating. In the absence of incident light at the apex, the local field of the ``naked'' surface plasmon modulates the tunneling barrier that drives the field emission. We give a detailed analysis of the governing dynamics in the presence and absence of an applied extractor field, and clearly distinguish contributions to tunneling current from Fermi electrons, athermal electron-hole pair distribution created by Landau damping of the plasmon, and the thermalized electrons. Independent of the distribution of the electrons in the metal half-space the emission acquires coherence by the time-dependent field of the plasmon in the vacuum half-space. [Preview Abstract] |
Monday, March 3, 2014 12:27PM - 1:03PM |
B2.00005: Manipulating Energy Flow at the Nanoscale by Coupling Plasmons of Metal Nanostructures to Resonant Molecules Invited Speaker: Gary Wiederrecht Collective hybrid excitations resulting from the coupling of metal nanostructures with organic molecules present unique opportunities for manipulating light-matter interactions at the nanoscale. In this talk, I discuss recent studies that are examples of the breadth of phenomena that are possible. First, the interactions of coupled plasmonic nanostructures with azobenzene-based polymers are described, in which the spatial features of the plasmonic near-field can be used to manipulate molecular motion. The directional molecular transport that results is shown to be useful for imaging the spatial and polarization features of the optical near-field. The modeling of this effect is described. Second, the coupling of excitonic molecular aggregates to metal nanostructures produces coherent coupling that provides added structure to the optical extinction spectra of metal nanoparticles, thereby by providing a photonic handle with which to manipulate energy flow on an ultrafast timescale. Monitoring the rate of energy flow as a function of photon energy reveals important information about the energy dissipation channels and the structural interactions between molecule and metal. Third, the strongly enhanced optical nonlinearity resulting from coupled plasmonic nanorods is described. The closely spaced nanorod material exhibits nonlocality of the optical response that has an unusually strong nonlinear dependence on incident light intensity. Electromagnetic modeling confirms the nonlocal response of the plasmonic metamaterial. The broader impact of collective hybrid excitations on nanophotonics applications is described. Use of the Center for Nanoscale Materials was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-06CH11357. [Preview Abstract] |
Monday, March 3, 2014 1:03PM - 1:15PM |
B2.00006: ABSTRACT WITHDRAWN |
Monday, March 3, 2014 1:15PM - 1:27PM |
B2.00007: Coherent polarization dynamics in three-photon photoemission from Cu(111) surface Cong Wang, Xuefeng Cui, Sean Garrett-Roe, Hrvoje Petek We investigate the surface states on Cu(111) by multi-photon photoemission using tunable ultra-short (\textless 15 fs) laser pulses. The angle-resolved photoemission spectra in the pre-resonant region for the two-photon excitation from the Shockley surface (SS) state to the n$=$1 image potential state are consistent with the well-known band structures. An anomaly is observed, however, for excitation at 610 nm (2.04 eV), where the tripling of the SS band occurs, the SS appearing as three parallel bands with the same effective mass. Excitation with the doubled frequency does not support this phenomenon. Instead we attribute this to parallel excitation pathways where the multi-photon photoemission occurs in response to the external and internal fields. The external field at 2.04 eV can drive the multiphoton absorption from SS, but also the coherent local field associated with the transition from top of the d-band to the sp-band at its crossing with the Fermi level can drive the photoemission. We examine the coherent nonlinear polarization dynamics by performing interferometric two-pulse correlation measurements. Fourier transform with respect to delay axis provides 2D linear and nonlinear spectra of the coherent polarization leading to the observed phenomena. [Preview Abstract] |
Monday, March 3, 2014 1:27PM - 1:39PM |
B2.00008: Resonant secondary light emission from plasmonic Au nanostructures at high electron temperatures created by pulsed laser excitation David Cahill, Jingyu Huang, Wei Wang, Catherine Murphy We study continuous-wave (cw) and pulsed laser excitation of aqueous suspensions of Au nanorods (AuNRs) as a model system for secondary light emission from plasmonic nanostructures. Resonant secondary emission contributes significantly to the background commonly observed in surface-enhanced Raman scattering (SERS) and to the light emission generated by pulsed laser excitation of metallic nanostructures that is often attributed to two-photon luminescence (TPL). The intensity of anti-Stokes emission collected using cw laser excitation at 785 nm is described by a 300 K thermal distribution of excitations. Excitation by sub-picosecond laser pulses at 785 nm broadens and increases the intensity of the anti-Stokes emission in a manner that is consistent with electronic Raman scattering by a high temperature distribution of electronic excitations predicted by a two-temperature model. Broadening of the pulse duration using an etalon reduces the intensity of anti-Stokes emission in quantitative agreement with the model. Experiments using a pair of sub-picosecond optical pulses separated by a variable delay show that the time-scale of resonant secondary emission is comparable to the time-scale for equilibration of electrons and phonons. [Preview Abstract] |
Monday, March 3, 2014 1:39PM - 1:51PM |
B2.00009: Cooperative amplification of energy transfer in plasmonic systems T.V. Shahbazyan, V.N. Pustovit, A.M. Urbas We study cooperative effects in energy transfer (ET) from an ensemble of donors to an acceptor near a plasmonic nanostructure. We demonstrate that in cooperative regime ET takes place from plasmonic superradiant and subradiant states rather than from individual donors leading to a significant increase of ET efficiency. The cooperative amplification of ET relies on the large coupling of superradiant states to external fields and on the slow decay rate of subradiant states. We show that superradiant and subradiant ET mechanisms are efficient in different energy domains and therefore can be utilized independently. We present numerical results demonstrating the amplification effect for a layer of donors and an acceptor on a spherical plasmonic nanoparticle. [Preview Abstract] |
Monday, March 3, 2014 1:51PM - 2:03PM |
B2.00010: Proximity Resonance and Localized Surface Plasmons Bo Liu, Eric Heller The collective excitation of conduction electrons in subwavelength nanostructures is known as Localized Surface Plasmon(LSP)[1]. Such plasmon modes has been intensively studied using noble nanoparticles . More recently, the possibility of building terahertz metamaterials supporting such LSP modes has been explored in graphene microribbons and microdisks. Unlike Surface Plasmon Polaritons(SPPs) at metal-insulator interface, LSP can be directly excited by light illumination and holds promise for applications in ultrasensitive biosensing, nano-optical tweezers and improved photovoltaic devices. In this paper, we consider the interaction of two LSPs in the weak coupling regime and show how an effect similar to the proximity resonance in the quantum scattering theory\cite{a2} gives rise to an asymmetric(quadrupole) mode with increased damping rate. The existence of this asymmetric mode relies on a small phase retardation between the two LSPs. This phase retardation, though small, is key to both increased damping rate for the asymmetric mode and reduced damping rate for the symmetric mode. When this small phase retardation is removed by changing the polarization of the exciting light,we show that the asymmetric mode can not be excited and the symmetric mode shows increased damping. [Preview Abstract] |
Monday, March 3, 2014 2:03PM - 2:15PM |
B2.00011: Two-photon activation of photoactive ligands bound to gold surfaces Brenden A. Magill, Xi Guo, Erich M. See, Roberto L. Reyes, Richey M. Davis, Webster L. Santos, Hans D. Robinson Photoactive crosslinkers are useful tools for optically driven assembly of nano-particles. We report on the use of ultra-short laser pulses to affect localized photoreactions in o-nitrobenzyl-based photoactive ligands bound to a gold surface with thiol groups. The reaction is activated through a combination of thermal activation and two-photon absorption, while at higher power densities, ligands can be ablated from the surface through breaking of the gold-thiol bond. We will present data on the interplay of these three effects as a function of laser power and exposure time, and demonstrate assembly of nanoparticles onto optically patterned surfaces. Finally, we will discuss how this effect could be used to create well-defined nanoparticle assemblies where great binding-site selectivity can be obtained through the combination of high electromagnetic intensity enhancements at plasmon hotspots and the nonlinear scaling of photoactivation efficiency in two-photon absorption processes. We acknowledge financial support from the National Science Foundation and the Institute for Critical Technology and Applied Science. [Preview Abstract] |
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