Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session M20: Focus Session: Metamaterials - Plasmonics |
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Sponsoring Units: DCMP Chair: David Smith, Duke University Room: 322 |
Wednesday, March 20, 2013 8:00AM - 8:12AM |
M20.00001: Quantum Plasmonics: Electron transfer processes Peter Nordlander Plasmon energies can be tuned across the spectrum by simply changing the geometrical shape of a nanostructure. Plasmons can efficiently capture incident light and focus it to nanometer sized hotspots which can enhance electronic and vibrational excitations in nearby structures.[1] Another important but still relatively unexplored property of plasmons, is that they can be efficient sources of hot energetic electrons which can transfer into nearby structures and induce a variety of processes. This process is a quantum mechanical effect: the decay of plasmon quanta into electron-hole pairs. I will discuss how plasmon induced hot electrons can be used in various applications: such as to induce chemical reactions in molecules physisorbed on a nanoparticle surface;[2] to inject electrons directly into the conduction band of a nearby substrate;[3] and to induce local doping of a nearby graphene sheet.[4] References [1] N.J. Halas \textit{et al.}, Adv. Mat. 24(2012)4842 [2] R. Huschka \textit{et al.}, JACS 133(2011)12247; S. Mukherjee \textit{et al.} TBP 2012 [3] M. W. Knight \textit{et al.}, Science 332(2011)702, Z.Y. Fang \textit{et al.}, NL 12(2012)3808 [4] Z.Y. Fang \textit{et al.}, ACS Nano 6(2012)10.1021/nn304028b [Preview Abstract] |
Wednesday, March 20, 2013 8:12AM - 8:24AM |
M20.00002: Plasmonic electron injection drives ultrafast phase transition by catastrophic phonon collapse I: experiment Kannatassen Appavoo, Nathaniel F. Brady, Bin Wang, Minah Seo, Joyeeta Nag, Rohit P. Prasankumar, Sokrates T. Pantelides, David J. Hilton, Richard F. Haglund Phase transitions in quantum materials such as vanadium dioxide (VO$_{\mathrm{2}})$ can provide functionality in nanophotonic devices. Here we report on a novel all-optical mechanism to trigger phase transformation (PT) of VO$_{\mathrm{2}}$ faster than its intrinsic single phonon period. By optically exciting a spectrally resonant sparse mesh of plasmonic gold nanoparticles, hot electrons created are ballistically injected across the Au/VO$_{\mathrm{2}}$ interface to assist the sub-picosecond PT, lowering the switching threshold by a factor of five. As confirmed by density functional calculations, the injected electrons cause a catastrophic collapse of the 6 THz phonon mode in VO$_{\mathrm{2}}$, essential for triggering its PT (next abstract). This demonstration of plasmon-induced hot-electron-driven PT controlled by this ultrafast technique represents a critical step towards developing hybrid nanomaterials with optimal switching thresholds. [Preview Abstract] |
Wednesday, March 20, 2013 8:24AM - 8:36AM |
M20.00003: Plasmonic electron injection drives ultrafast phase transition by catastrophic phonon collapse II: theory Bin Wang, Kannatassen Appavoo, Nathaniel Brady, Minah Seo, Joyeeta Nag, Rohit Prasankumar, David Hilton, Richard Haglund, Sokrates Pantelides The ultrafast photo-induced phase transition in VO$_{2}$ is promising for data storage and sensing applications. Our experimental work (the previous talk) shows that in a Au/VO$_{2}$ hybrid nanostructure, electrons excited in the Au photocathode by an ultrafast laser trigger the insulator-to-metal transition in VO$_{2}$. Here we report first-principles density-functional calculations showing that the collapse of a 6 THz optical phonon, corresponding to a twisting motion of V atoms, is responsible for the ultrafast phase transition. Above a concentration threshold, we find that injected electrons from Au induce collapse of the VO$_{2\, }$phonon, which stimulates the monoclinic-to-rutile structural phase transition. We also show that hole-doping can induce the same effect. The abrupt change of the critical phonon results from the weakening of the V-V bonds induced by the combined flux of injected electrons and holes. Thus, our results explain the experimental finding of plasmonic-electron-driven ultrafast phase transition and represent a step towards manipulating the photo-induced phase transition by surface modification. [Preview Abstract] |
Wednesday, March 20, 2013 8:36AM - 8:48AM |
M20.00004: Optical circulation and power flow rotation with nonreciprocal plasmonic structure Artur Davoyan, Nader Engheta In this work we propose a concept for tailoring the near-zone optical field with the plasmonic nanostructures mixed with MO materials, and demonstrate a novel effect of a subwavelength power flow circulation. We study both analytically and numerically plasmonic nanostructures embedded into magneto-active media, and analyze their resonances and corresponding eigenmode spectra. We show that when the structure is degenerate the magneto-optical activity, when introduced, causes strong interaction between these modes. Such intermodal interaction leads to a formation of a novel set of rotating states and to a frequency splitting between them. We study the plane wave excitation of such nanostructures and reveal a strong power flux circulation around such structures in the presence of magneto-optical activity. We will discuss a possible application of the observed effect and propose a subwavelength optical circulator. In particular, we study numerically a plasmonic nanostructure embedded into the core of the Y-junction formed by single mode optical waveguides. We show that mixing the plamonic nanostructures with magneto-optical materials it is possible to break significantly the symmetry between the output arms of the junction and almost completely isolate one of them. [Preview Abstract] |
Wednesday, March 20, 2013 8:48AM - 9:00AM |
M20.00005: Mode matching for optimal plasmonic nonlinear generation Kevin O'Brien, Haim Suchowski, Jun Suk Rho, Boubacar Kante, Xiaobo Yin, Xiang Zhang Nanostructures and metamaterials have attracted interest in the nonlinear optics community due to the possibility of engineering their nonlinear responses; however, the underlying physics to describe nonlinear light generation in nanostructures and the design rules to maximize the emission are still under debate. We study the geometry dependence of the second harmonic and third harmonic emission from gold nanostructures, by designing arrays of nanostructures whose geometry varies from bars to split ring resonators. We fix the length (and volume) of the nanostructure on one axis, and change the morphology from a split ring resonator on the other axis. We observed that the optimal second harmonic generation does not occur at the morphology indicated by a nonlinear oscillator model with parameters derived from the far field transmission and is not maximized by a spectral overlap of the plasmonic modes; however, we find a near field overlap integral and mode matching considerations accurately predict the optimal geometry. [Preview Abstract] |
Wednesday, March 20, 2013 9:00AM - 9:12AM |
M20.00006: Theory of plasmon-enhanced metal photoluminescence Tigran V. Shahbazyan Metal photoluminescence (MPL) originates from radiative recombination of photoexcited core holes and conduction band electrons. In metal nanostructures, MPL is enhanced due to surface plasmon local field effect. We identify another essential process in plasmon-assisted MPL - excitation of Auger plasmons by core holes - that hinders MPL from small nanostructures. We develop a microscopic theory of plasmon-enhanced MPL that incorporates both plasmonic enhancement and suppression mechanisms and derive enhancement factor for MPL quantum efficiency. Our numerical calculations of MPL from Au nanoparticles are in excellent agreement with experiment. [Preview Abstract] |
Wednesday, March 20, 2013 9:12AM - 9:24AM |
M20.00007: Probing light-matter interactions in plasmonic nanostructures with a single quantum dot Chad Ropp, Zachary Cummins, Sanghee Nah, John T. Fourkas, Benjamin Shapiro, Edo Waks Understanding and controlling the interactions between single quantum emitters and plasmonic nanostructures is important for a wide variety of applications in quantum optics and nanophotonics. Metal nanostructures provide subwavelength confinement of electromagnetic fields in the form of surface plasmon polaritons, which can enhance optical nonlinearities for improved light-matter interactions. In this talk we will present recent results on nano-manipulation of single colloidal quantum dots (QDs) for deterministic probing of light-matter interactions in plasmonic nanostructures. Single QDs are manipulated using a combination of microfluidics and engineered fluid chemistry. We achieve deterministic positioning with 50 nm accuracy and demonstrate probing of the surface plasmon mode of a silver nanowire. Spatially variant interactions are quantified by measuring the coupling rate of the QD into the wire mode as well as changes to the QD emission lifetime. The resulting interactions are resolved with nanoscale resolution and reveal features such as the evanescent field decay away from the wire surface and interference along the wire length. [Preview Abstract] |
Wednesday, March 20, 2013 9:24AM - 9:36AM |
M20.00008: Giant circular dichroism of a molecule in a plasmonic nanoparticle dimer Hui Zhang, A.O. Govorov We report on giant circular dichroism (CD) of a molecule inserted into a plasmonic hot spot. Naturally occurring molecules and biomolecules have typically CD signals in the UV range, whereas plasmonic nanocrystals exhibit strong plasmon resonances in the visible spectral interval. Therefore, excitations of chiral molecules and plasmon resonances are typically off-resonant. Nevertheless, we demonstrate theoretically that it is possible to create strongly-enhanced molecular CD utilizing the plasmons. Specifically, by employing a nanoparticle dimer, we gain simultaneously a strong plasmonic enhancement and a shift of optical CD from the UV range to the visible. The associated mechanism of giant CD comes from the Coulomb interaction which is greatly amplified in a plasmonic hot spot. Two key factors play a role in the described effect: One is the Coulomb interaction within the molecule-dimer complex giving rise to the plasmon peak in the CD spectrum, whereas the other one is the plasmonic enhancement of the absorption process in a chiral molecule. We propose that, by using the hot spot effect and plasmon-induced CD signals, one can design optical sensors to study chirality of biomolecules. [Preview Abstract] |
Wednesday, March 20, 2013 9:36AM - 9:48AM |
M20.00009: Exciton-plasmon coupling in monolayer molybdenum disulfide Jed Ziegler, A.K.M. Newaz, Kirill Bolotin, Richard Haglund Two-dimensional materials such as monolayer molybdenum disulfide (MoS$_{2})$ represent a unique platform for investigating the dynamics of exciton-plasmon coupling. We report on the generation and modulation of coherent and incoherent coupled states between excitons in monolayer MoS$_{2}$ and plasmons in an array of gold nanoparticle deposited onto the surface of MoS$_{2}$. We study the behavior of these coherent states, termed plexcitons using a combination of photoluminescence, extinction and ultrafast spectroscopies. The close proximity of the two characteristic exciton bands of MoS$_{2}$ presents multiple coherent coupling configurations, including A-or-B exciton-plasmon, and A-and-B exciton-plasmon interactions. These configurations of plexciton formation that are shown to modulate both the extinction and photoluminescence spectra of the hybrid system. This includes broadband photoluminescence and Fano-type resonances. This behavior is distinct from the spectral response of the MoS$_{2}$ and plasmonic components of the system. Incoherent exciton-plasmon coupling, achieved by detuning from the plasmon extinction peaks, enhances the interaction of MoS$_{2}$ with light by focusing the plasmon energy. Depending on which coupling configuration is chosen, our results show that the MoS$_{2}$/plasmon hybrid systems can act as high efficiency light harvesters, broadband emitters and as tunable visible and NIR photodetectors. [Preview Abstract] |
Wednesday, March 20, 2013 9:48AM - 10:00AM |
M20.00010: Optical Properties of Graphene Plasmons in Periodic Gate Structures Stefan C. Badescu, Robert C. Fitch Plasmons in graphene have been shown to be tunable in a wide frequency range including the THz regime. Room temperature, narrow plasmon modes have been demonstrated in graphene ribbons arranged periodically on surfaces. Here we present computational results of localized modes in continuous graphene layers with periodic arrangements of gates that modulate spatially the charge density. These induce boundary conditions different from those in graphene ribbons and open the possibility of electrical injection. We discuss the optical absorption and reflection spectra for different gate voltages and for a range of gate widths and spacing. We also discuss different regimes of electrical injection and the role of substrates in coupling to plasmons and in heat dissipation. [Preview Abstract] |
Wednesday, March 20, 2013 10:00AM - 10:12AM |
M20.00011: Optical Properties of Epitaxially Grown Silver Films Yanwen Wu, Chendong Zhang, Matt Zhang, Chih-Kang Shih, Xiaoqin Li One major obstacle in the advancing field of plasmonics is the loss in metals. A sizable contribution of this loss comes from grain boundaries and surface roughness introduced during thin film growth using conventional deposition methods. A novel epitaxial growth technique is used to produce silver (Ag) thin films free of such flaws. We investigate the optical properties--namely the dielectric optical constants--of these new epitaxial films in the bulk region and in the ultrathin film limit where quantum mechanical behaviors emerge due to energy quantization in the growth direction. The values for the dielectric optical constants are extracted from the spectral ellipsometry (SE) measurements over a wide range of optical frequencies. By using an adequate model of the sample structure and initial values of the fitting parameters (i.e. the real and imaginary parts of the optical constants), we can extract these measured values for the new Ag films. We have confirmed that in the bulk region, the optical constants converge with the well-known Johnson and Christy measurements [1]. In the ultrathin film limit, however, we observed significant changes near the D-band transition likely due to a quantum well-like density of states.\\[4pt] [1] P.B. Johnson and R.W. Christy, PRB 6 4370 (1972) [Preview Abstract] |
Wednesday, March 20, 2013 10:12AM - 10:24AM |
M20.00012: Hamiltonian Optics Approach for Hybridized Surface Plasmon Polariton in Graded Metal-Dielectric-Metal Waveguide with Periodically Varying Index Sze Fung Lee, King Chun Lai, Kin Wah Yu In a complex plasmonic nanostucture, it is possible to support several elementary modes of surface plasmon polariton due to the multi-surface configuration. Hybridized surface plasmon polariton (HSPP) is formed when those modes interact with each others. The dispersion curves of these complex plasmon modes will be shifted from the original ones. As the shifting depends strongly on the geometry of the structure, it allows one to manage the properties of light inside the structure with much higher flexibility and complexity. We have studied the properties of HSPP in a graded metal-dielectric-metal (MDM) waveguide with the refractive index of the dielectric varying periodically, using the Hamiltonian optics approach, to investigate the feasibility of light manipulation inside this structure. We have extracted the allowed phase orbits using the quantization condition. The time series of position and wavevector of HSPP were also simulated by solving the Hamiltonian equations of motion. The results revealed two possible orbits of the HSPP inside the waveguide: confinement and propagation. The range of angular frequency such that the phase orbits become singular is also determined. In this regime, the photon energy is efficiently converted into surface plasmon energy. [Preview Abstract] |
Wednesday, March 20, 2013 10:24AM - 10:36AM |
M20.00013: Self-Complementary Plasmonic Structures for High Efficiency Broadband Absorber in the Visible Range Tianyi Sun, Yang Wang, Zhifeng Ren, Krzysztof Kempa We demonstrate, by simulation, that a planar 3-layer structure on a metal substrate can highly absorb electromagnetic radiation in the entire visible range, which can become a potential platform for high-efficiency broadband absorber. Such a structure consists of an ultrathin semiconducting layer topped with a solid nanoscopically perforated metallic film and then a dielectric interference layer. It is shown that the perforated metallic film and the ultrathin absorber form an effective metamaterial film, which negatively refracts light in this broad frequency range. Our quantitative simulation confirms that the absorption bandwidth is maximized at the self-complementary pattern of the percolation threshold. If amorphous silicon (a-Si) is selected as the ultrathin semiconducting material, the absorbance of the structure with a checkerboard-patterned perforated metallic film is about 90{\%} in the visible range (from 400 nm to 700 nm), where 80{\%} goes into the a-Si layer and the other 10{\%} being absorbed by other layers. Further simulation shows that for a single p-i-n a-Si junction, the energy conversion efficiency of an optimized structure can exceed 12{\%}. [Preview Abstract] |
Wednesday, March 20, 2013 10:36AM - 10:48AM |
M20.00014: Plasmonic halos: optical surface plasmon drumhead modes Fan Ye, Michael J. Burns, Michael J. Naughton We present the discovery and systematic study of a novel optical phenomenon, wherein optically-pumped surface plasmons on circular silver microcavities form confined drumhead modes that, under off-resonant conditions, transform to colorful far field radiation at their circumferential boundaries. We call this phenomenon the ``plasmonic halo.'' We demonstrate both experimentally and theoretically that such circular microcavities integrated with perimeter step gaps can generate surface plasmon cavity modes, and modulate optical transmission/emission through/from the device, yielding the plasmonic halo effect. Via the tuning of geometric and/or material parameters, optical properties of this device can be manipulated in the visible range, leading to promising applications in biomedical plasmonics, dielectric constant sensing and discrete optical filtering, among others. [Preview Abstract] |
Wednesday, March 20, 2013 10:48AM - 11:00AM |
M20.00015: Tunable Fano resonance due to interaction between molecular vibrational modes and a double-continuum of a plasmonic metamolecule Edward Osley, Claudiu Biris, Paul Thompson, Raham Jahromi, Nicolae Panoiu, Paul Warburton We have fabricated and characterized a plasmonic system comprised of an array of asymmetric cross-shaped apertures in a metallic film coated with poly(methyl methacrylate) (PMMA). The apertures (called plasmonic metamolecules) produce localized surface plasmon (LSP) resonances that can be tuned by varying the polarization of incident light. Arrays of these nano-scale apertures, designed to have resonances at infrared wavelengths, were fabricated using electron beam lithography and argon ion milling of a gold film. Filling the apertures with PMMA allowed its C=O bond resonance to interact with tunable LSP modes. The transmission, reflection and absorption spectra of the system were measured using FTIR. Coupling between the LSPs and the C=O bond is shown to produce a Fano resonance that can be tuned in situ. The system was investigated theoretically using (a) rigorous electromagnetic calculations and (b) a quantum mechanical model that describes the interaction between a discrete state (the C=O bond) and multiple continua (the LSPs of the plasmonic metamolecule). We demonstrate that the predictions of the quantum model are in good agreement with the experimental data and show that the model allows an intuitive interpretation, at the quantum level, of the plasmon-molecule coupling. [Preview Abstract] |
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