Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session A6: Focus Session: Nanostructures and Metamaterials I |
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Sponsoring Units: DMP DCMP Chair: Federico Capasso, Harvard University Room: 006A |
Monday, March 2, 2015 8:00AM - 8:36AM |
A6.00001: In-situ, nanometer-scale visualization of nanoparticle phase transitions and light-matter interactions in 2- and 3-D Invited Speaker: Jennifer Dionne We present new spectroscopic techniques that enable visualization of nanoparticle phase transitions in reactive environments and light-matter interactions with nanometer-scale resolution. First, we directly monitor hydrogen absorption and desorption in individual palladium nanocrystals. Our approach is based on \textit{in-situ} electron energy-loss spectroscopy (EELS) in an environmental transmission electron microscope. By probing hydrogen-induced shifts of the palladium plasmon resonance, we find that hydrogen loading and unloading isotherms are characterized by abrupt phase transitions and macroscopic hysteresis gaps. These results suggest that alpha and beta phases do not coexist in single-crystalline nanoparticles, in striking contrast with conventional phase transitions and ensemble measurements of Pd nanoparticles. Then, we then extend these techniques to monitor nanoparticle reactions in a liquid environment. By constructing a flow chamber, we directly monitor growth and assembly of colloidal plasmonic metamaterial constituents induced by chemical catalysts. Lastly, we introduce a novel tomographic technique, cathodoluminescence spectroscopic tomography, to probe optical properties in three dimensions with nanometer-scale spatial and spectral resolution. Particular attention is given to reconstructing a 3D metamaterial resonator supporting broadband electric and magnetic resonances at optical frequencies. Our tomograms allow us to locate regions of efficient cathodoluminescence across visible and near-infrared wavelengths, with contributions from material luminescence and radiative decay of electromagnetic eigenmodes. The experimental signal can further be correlated with the radiative local density of optical states in particular regions of the reconstruction. Our results provide a general framework for visualizing chemical reactions and light-matter interactions in plasmonic materials and metamaterials, with sub-nanometer-scale resolution, and in three-dimensions. [Preview Abstract] |
Monday, March 2, 2015 8:36AM - 8:48AM |
A6.00002: Photoluminescence of Giant Quantum Dots Coupled With Waveguide Modes of Plasmonic Gap Bar Nanoantennas Feng Wang, Hue-Minh Nguyen, Niladri Karan, Yagnaseni Ghosh, Chris Sheehan, Jennifer Hollingsworth, Han Htoon We designed a plasmonic gap bar nanoantenna, which is in resonances with the emission band of silica-coated giant-CdSe/CdS quantum dots. This antenna is composed of two parallel gold nano-bars with 40 nm gap fabricated on top of a 20 nm thick gold film and glass substrate. Utilizing two-step e-beam lithography process, we have fabricated this antenna and integrated the single silica-coated giant quantum dots into the gap. The enhanced emission rate and emission polarization have been studied for quantum dots placed at different positions along the gap bar antennas. The use of silica shell suppressed the energy transfer quenching from giant quantum dots to metal. Therefore, the detected lifetime shortening by a factor of 8 is purely resulted from the enhancement of decay rate. Experimental measurements also show that the photoluminescence intensity with polarization perpendicular to the bar can be 9 times stronger than along the bar, leading to a linear polarization degree of 0.8. Strong modulation of emission spectra has also been observed. Numerical simulations indicate that the strong linear polarization and the spectral modulation could be due to the emission coupling with the plasmonic waveguide modes. [Preview Abstract] |
Monday, March 2, 2015 8:48AM - 9:00AM |
A6.00003: Synchrotron X-ray and optical studies of the DNA-mediated growth of plasmonic nanostructures Gang Chen, Geng Wang, Xiaonan Zhang, Heping Geng, Lifeng Xu, Wenqin Li, Xin Liu Reproducible and controllable growth of nanostructures with well-defined physical and chemical properties is a longstanding problem in nanoscience. A key step to address this issue is to understand their underlying growth mechanism, which is often entangled in the complexity of growth environments and obscured by rapid reaction speeds. Synchrotron x-rays, because of their specific wavelengths (nanometers) and advantages of large flux, high penetration and adjustable photon energy, have a particularly important position in structural and electronic characterizations of nanomaterials. Herein, we demonstrate that the evolution of size, surface morphology, and the optical properties of plasmonic nanostructures could be quantitatively intercepted by dynamic and stoichiometric control of the DNA-mediated growth. By combining synchrotron-based small-angle X-ray scattering with transmission electron microscopy, we reliably obtained quantitative structural parameters for these fine nanostructures that correlate well with their optical properties as identified by UV/Vis absorption and dark-field scattering spectroscopy. We report growth mechanisms for SERS active plasmonic nanostructures, and the remarkable interplay between their morphology and plasmonic properties. [Preview Abstract] |
Monday, March 2, 2015 9:00AM - 9:12AM |
A6.00004: Standing wave plasmon modes interact in an antenna-coupled nanowire Jared Day, Nicolas Large, Peter Nordlander, Naomi Halas In a standing wave optical cavity, the coupling of cavity modes, e.g. through a nonlinear medium, results in a rich variety of nonlinear dynamical phenomena, such as frequency pushing and pulling, mode-locking and pulsing, and modal instabilities. Metallic nanowires of finite length support a hierarchy of longitudinal surface plasmon modes with standing wave properties: the plasmonic analog of a Fabry-P\'{e}rot cavity. Here we show that positioning the nanowire within the gap of a plasmonic nanoantenna introduces a passive, hybridization-based coupling of the standing-wave nanowire plasmon modes with the antenna structure, mediating an interaction between the nanowire plasmon modes themselves. Frequency pushing and pulling, and the enhancement and suppression of specific plasmon modes, can be controlled and manipulated by nanoantenna position and shape. Dark-field spectroscopy, CL spectroscopy and imaging, and finite-difference time-domain calculations are performed to investigate these surface plasmon ``drift.'' Near-field coupling of nanoantennas to nanowire optical cavities shows that plasmon hybridization is a powerful strategy for controlling the radiative LDOS of nanowires, and could ultimately enable strategies for active control of emission properties in nanowire-based devices. [Preview Abstract] |
Monday, March 2, 2015 9:12AM - 9:24AM |
A6.00005: Accurate modeling of photodynamic processes enhanced by plasmonic nanoantennas Christos Argyropoulos, Gleb Akselrod, Cristian Ciraci, Thang Hoang, Maiken Mikkelsen, David Smith Plasmonic nanoantennas are powerful platforms to enhance fluorescence and spontaneous emission rates leading to exciting nanophotonic applications. Strong fields confined in highly subwavelength regions in the nanoantenna geometry are ideal conditions to increase the Purcell factor. However, the accurate modeling of the interaction between fluorescence molecules or quantum-dots and plasmonic nanoantennas is a complicated task. In our talk, we will demonstrate efficient numerical techniques to accurately compute the total spontaneous emission rate and radiation efficiency by multiple fluorescence molecules and quantum-dots randomly positioned nearby the plasmonic nanoantennas [G. Akselrod, C. Argyropoulos et al., Nat. Phot. 8, 835-840 (2014)]. This is a complex problem because in plasmonic systems the Purcell factor has contributions from an increased radiative rate and from an increased nonradiative rate due to the inherent metallic losses. We will demonstrate ways to accurately compute the useful fraction of energy emitted as radiation, known as the radiative quantum yield. When we combine the knowledge of the Purcell factor and the quantum yield, the enhancement in the emitters' radiative rate can be computed, which consists the key property to obtain efficient ultrafast nanophotonic communication systems. The presented numerical results are in excellent agreement with experimental results obtained by similar nanoantenna systems. [Preview Abstract] |
Monday, March 2, 2015 9:24AM - 9:36AM |
A6.00006: Surface Plasmon Propagation in Nanostructured Metallic Waveguides Y.M. Calm, J.M. Merlo, A.H. Rose, N.T. Nesbitt, A.M. Boyce, G. McMahon, M.J. Burns, K. Kempa, M.J. Naughton Visible frequencies of light can be routed on subwavelength scales with nanostructured, metallic waveguides by coupling optical energy to surface plasmon (SP) modes at a metal-insulator interface. Epitaxially-grown Ag nanowires and nanocoaxes provide a low-loss, ``model'' system to characterize the propagation of SP waves. We have studied these structures by electron, focused ion, scanning probe, and optical microscopies, and have observed propagation lengths exceeding 15$\lambda_{vac}$ with confinement on the order of $0.07(\lambda_{vac})^{2}$. Experimental efforts towards lithographically-fabricated metal-insulator-metal waveguides are discussed. Finally, an architecture for a nanocoax-based optical microscope,\footnote{K. Kempa, X. Wang, Z. F. Ren, and M. J. Naughton, \textit{Appl}. \textit{Phys}. \textit{Lett}. \textbf{92}, 043114 (2008)} which extracts near-field (evanescent) information and propagates it into the far-field, is presented. [Preview Abstract] |
Monday, March 2, 2015 9:36AM - 9:48AM |
A6.00007: Investigation of nanogap localized field enhancement in gold plasmonic structures Desalegn Tadesse Debu, Stephen Bauman, Cameron Saylor, Eric Novak, David French, Joseph Herzog Nanogaps between plasmonic structures allow confining the localized electric field with moreenhancements. Based on previously implemented two-step lithography process, we introducea nano-masking technique to fabricate nanostructrues and nanogaps for various geometrical patterns. This new method can fabricate gold nanostructures as well as nanogaps that are less than 10nm, below the limiting scale of lithography. Simulation from finite element method (FEM) shows strong gap dependence of optical properties and peak enhancement of these devices. The fabricated plasmonic nanostructure provides wide range of potential future application including highly sensitive optical antenna, surface enhanced Raman spectroscopy and biosensing. [Preview Abstract] |
Monday, March 2, 2015 9:48AM - 10:00AM |
A6.00008: Purcell factors exceeding 1,000 in directional and efficient plasmonic nanoantennas Gleb Akselrod, Christos Argyropoulos, Thang Hoang, Cristian Ciraci, Chao Fang, Jiani Huang, David Smith, Maiken Mikkelsen To move nanophotonic devices such as nano-lasers, ultrafast LEDs, and single photon sources into the practical realm, a challenging list of requirements must be met, including directional emission, room temperature and broadband operation, and high radiative quantum yield, while having a large spontaneous emission rate. To achieve these features simultaneously, a platform is needed in which the various decay channels of embedded emitters can be fully understood and controlled. In this work\footnote{Akselrod et al., {\em Nature Photonics} \textbf{8}, 835-840 (2014).} we show that all these device requirements can be satisfied by a plasmonic nanoantenna with emitters embedded in the nanoscale gap ($\sim10$ nm) between a metal film and a silver nanocube. Fluorescence lifetime measurements on ensembles of emitters reveal Purcell factors exceeding 1000 while maintaining high quantum yield ($>0.5$) and directional emission (84\% collection efficiency). Using angle resolved fluorescence measurements, we independently determine the orientations of emission dipoles in the nanoscale gap. By incorporating this information along with the three-dimensional spatial distribution of dipoles into simulations, we predict the emission dynamics in excellent agreement with experiment. [Preview Abstract] |
Monday, March 2, 2015 10:00AM - 10:12AM |
A6.00009: Study of plasmonic and magnetic modes in non-symmetric gold nano-ring geometries Larousse Khosravi Khorashad, Hui Zhang, Eva-Maria Roller, Tim Liedl, Alexander O. Govorov Research on the science of plasmonics and the study of the optical properties of photonic devices at the nanoscale have become essential over the past few decades owing to the introduction of innovative plasmonic devices and their vast applicability. The quest for light manipulation in metallic nanostructures has grown greatly due to the creation of novel optical devices for applications ranging from meta-materials and cloaking to optical sensing and plasmonic waveguides. Here, we present theoretical and numerical studies of complex nano-ring geometries composed of gold nano-spheres. We used the finite element method (COMSOL) for computational implementations. For each of the experimentally built structures, we have obtained the plasmonic resonance modes. The nano-ring structures exhibit magnetic, dipole and multipole plasmonic modes and these modes depend on the size of nanoparticles and the geometry of nano-rings. We also indicate that the plasmonic resonances observed in scattering and absorption spectra are highly dependent on symmetry breaking of nano-rings. Finally, we compare our results with the experiment and observe that our simulation is in good agreement with the experimental measurements. [Preview Abstract] |
Monday, March 2, 2015 10:12AM - 10:24AM |
A6.00010: VO$_{2}$ Semishells/Au Nanohemispheres Hybrid Nanostructure with Tunable Optical Property Ki Wan Nam, Abbas Maroof, Dong-guk Cho, Bong-Jun Kim, Hyun-Tak Kim, Seunghun Hong Vanadium dioxide (VO$_{2})$ has been drawing much attention due to its unique property of a reversible phase transition accompanying significant changes in electrical and optical properties. In addition, the optical property of VO$_{2}$ can be tuned by depositing metal on the VO$_{2}$, and thus VO$_{2}$-metal hybrid structures have been intensively studied to develop smart materials with tunable optical properties. Herein, we developed hybrid nanostructures based on VO$_{2}$ semishells (SSs) and Au nanohemispheres (NHs) as tunable plasmonic nanostructures. The hybrid structure exhibited an enhanced optical absorbance compared to that of the VO$_{2}$ SSs alone, which could be attributed to a strong plasmonic coupling between VO$_{2}$ SSs and Au NHs. Furthermore, the positions of peaks in their absorbance spectra can be adjusted by controlling temperatures, presumably due to the phase transition of the VO$_{2}$ SS structures. Our hybrid nanostructures with tunable optical properties can be useful for various optoelectronic applications such as photothermal nanoregulators and ultrafast optical switches [Preview Abstract] |
Monday, March 2, 2015 10:24AM - 10:36AM |
A6.00011: Cluster Ion Beam Induced Nano Metallic Rippled Structures for Localized Surface Plasmon Resonance (LSPR) Based Sensors Iram Saleem, Buddhi Tilakaratne, Yanzhi He, Epie Nzumbe, Dharshana Wijesundera, Quark Chen, Wei-Kan Chu Localized surface plasmon resonance (LSPR) based bio sensors have a high sensitivity and exploit a label free real time analytical detection mechanism. We have produced plasmonic nano-structured substrates by cluster ion beam irradiation of thin gold films and have studied their effectiveness as potential plasmonic sensors. By adsorbing a mono-layer of thiolated organic compounds on the surface of these substrates we identified the shift in the LSPR peaks triggered by the change of dielectric function in the neighborhood of the structures. These plasmonic nano-metallic structures can be utilized to observe the change of LSPR resonance frequency due to adsorption, re-adsorption and reactions taking place on the surface that can potentially be mapped to reaction mechanics [Preview Abstract] |
Monday, March 2, 2015 10:36AM - 10:48AM |
A6.00012: Virus templated plasmonic nanoclusters with icosahedral symmetry via directed assembly Banahalli Ratna, Jake Fontana, Walter Dressick, Jamie Phelps, John Johnson, Travian Sampson, Ronald Rendell, Carissa Soto Controlling the spatial and orientational order of plasmonic nanoparticles may lead to structures with novel electromagnetic properties and applications such as sub-wavelength imaging and ultra-sensitive chemical sensors. Here we report the directed assembly of three-dimensional, icosahedral plasmonic nanoclusters with resonances at visible wavelengths [1]. We show using transmission electron microcopy and \textit{in situ} dynamic light scattering the nanoclusters consist of twelve gold nanospheres attached to thiol groups at predefined locations on the surface of a genetically engineered cowpea mosaic virus with icosahedral symmetry. We measured the bulk absorbance from aqueous suspensions of nanoclusters and reproduced the major features of the spectrum using finite-element simulations. Furthermore, because the viruses are easily produced in gram quantities the directed assembly approach is capable of high-throughput, providing a strategy to realize large quantities for applications. \\[4pt] [1] J. Fontana, W. J. Dressick, J. Phelps, J. E. Johnson, R. W. Rendell, T. Sampson, B. R. Ratna and C. M. Soto, Small \textbf{10}, 3058 (2014) [Preview Abstract] |
Monday, March 2, 2015 10:48AM - 11:00AM |
A6.00013: Spectroscopic Imaging of NIR to Visible Upconversion from NaYF$_{4}$: Yb$^{3+}$, Er$^{3+}$ Nanoparticles on Au Nano-cavity Arrays Jon Fisher, Bo Zhao, Cuikun Lin, Mary Berry, P. Stanley May, Steve Smith We use spectroscopic imaging to assess the spatial variations in upconversion luminescence from NaYF$_{4}$:Er$^{3+}$,Yb$^{3+}$ nanoparticles embedded in PMMA on Au nano-cavity arrays. The nano-cavity arrays support a surface plasmon (SP) resonance at 980nm, coincident with the peak absorption of the Yb$^{3+}$ sensitizer. Spatially-resolved upconversion spectra show a 30X to 3X luminescence intensity enhancement on the nano-cavity array compared to the nearby smooth Au surface, corresponding to excitation intensities from 1 W/cm$^{2}$ to 300kW/cm$^{2}$. Our analysis shows the power dependent enhancement in upconversion luminescence can be almost entirely accounted for by a constant shift in the effective excitation intensity, which is maintained over five orders of magnitude variation in excitation intensity. The variations in upconversion luminescence enhancement with power are modeled by a 3-level-system near the saturation limit, and by simultaneous solution of a system of coupled nonlinear differential equations, both analyses agree well with the experiments. Analysis of the statistical distribution of emission intensities in the spectroscopic images on and off the nano-cavity arrays provides an estimate of the average enhancement factor independent of fluctuations in nano-particle density. [Preview Abstract] |
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