Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session G50: Focus Session: Plasmon Enhanced Light: Matter Interactions |
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Sponsoring Units: DMP Chair: Xiaoqin (Elaine) Li, University of Texas at Austin Room: Mile High Ballroom 1D |
Tuesday, March 4, 2014 11:15AM - 11:51AM |
G50.00001: Metal Nanostructure-Multiexciton Interactions: From Emission Enhancement to Modification of Photon Statistics Invited Speaker: Han Htoon In the past decade, a tremendous amount of research efforts has been invested in the study of metal nanostructure (NM)-nanoemitter interactions. However, most of these studies have been conducted in the context of MNs interacting with single excitons. In contrast to these studies, we ventured into the realm of multi-exciton-MN interactions by performing low temperature photoluminescence (low-T PL) and photon-correlation spectroscopy studies on individual core/ultra-thick-shell NQDs (``giant''-NQDs or g-NQDs) deposited on nano-roughened silver films. Our low-T PL study show that (1) the multiexciton (MX) emissions in g-NQD coupled to silver films were enhanced mainly through the direct modification on the competition between the radiative and nonradiative recombination processes of MXs; and (2) strong enhancement in absorption is not necessary for a strong multiexciton emission.\footnote{\textit{J. Phys. Chem. Letts.} \textbf{4}, 1465-1470, (2013).} Our room temperature photon-correlation spectroscopy studies reveal that the MN-g-NQD interaction can transform sub-Poissonian photon emission statistics of individual g-NQDs to strong super-Poissonian statistics (photon-bunching).\footnote{\textit{Phys. Rev. Lett.} \textbf{110}, 117401, (2013).} We further derived the conditions required for the manifestation of this phenomenon and show that it can also manifest in other nanoemitters such as epitaxially grown QDs and single walled carbon nanotubes. The understandings attained in this work could open a new plasmonic route for manipulation of important multiexciton processes such as optical amplification, lasing and entangled-photon-pair generation. [Preview Abstract] |
Tuesday, March 4, 2014 11:51AM - 12:03PM |
G50.00002: Plasmon enhanced photoluminescence in dye doped films coupled to random metal aggregates Shikhadeep Gill, Miriam Deutsch We present a study of plasmon enhanced light emission from metal/dielectric composites comprising aggregated nanocrystalline silver islands deposited onto thin polymer films which have been doped with the amplifying dye Rhodamine 6G. We address the dependence of dye photoluminescence on the morphology of the metal aggregates as additional silver is added to the films. A frequency doubled Nd:YAG laser is used as the pump for exciting both the gain medium as well as localized surface plasmons in the metal aggregates. We exploit the intense plasmon fields localized to the metal islands to obtain greatly enhanced luminescence signals. In addition, the large scattering cross sections sustained by the metal nanoparticles serve to further increase light-molecule interaction in this system. We discuss the dependence of luminescence enhancement factors on the material's structural properties, and show that maximal signals are obtained when metal islands begin to coalesce. Using films in the coalescence regime, we then proceed to discuss the dependence of dye emission on pump power, and address the prospects for achieving plasmon-enhanced random lasing in these materials. [Preview Abstract] |
Tuesday, March 4, 2014 12:03PM - 12:15PM |
G50.00003: Giant fluorescence enhancement of fluorophores coupled to nanopatch antennas Maiken H. Mikkelsen, Alec Rose, Thang B. Hoang, Felicia McGuire, Jack J. Mock, Cristian Cirac\`i, David R. Smith Plasmonic cavities and nanoantennas have proven to be particularly attractive candidates for modifying the excitation and decay rates of nearby emitters. Here, we demonstrate giant enhancement of fluorescence in planar nanoparticles electromagnetically coupled to a metallic film, resembling nanopatch antennas. The antennas consist of colloidally synthesized silver nanocubes deposited over a 50 nm silver film. The cubes and film are separated by a $\sim 5$ nm selfassembled polyelectrolyte spacer layer, coated with a dilute layer of fluorophores (sulfo-cy5 carboxylic acid). By varying the size of the nanocubes, we tune the plasmonic resonance throughout the excitation and emission spectra of the embedded fluorophores, demonstrating a seamless transition between fluorescence enhancement and quenching. The experimentally observed behavior agrees well with performed finite-element simulations. Using this tunable platform, design rules for optimal enhancement are revealed, allowing us to demonstrate giant fluorescence enhancements and a significantly increased spontaneous emission rate. [Preview Abstract] |
Tuesday, March 4, 2014 12:15PM - 12:27PM |
G50.00004: Single particle optical investigation of gold shell enhanced upconverted fluorescence emission Kory Green, Shuang Fang Lim, Hans Hallen Upconverting nanoparticles (UCNPs) excited in the near IR offer novel advantages as fluorescent contrast agents, allowing for background free bio-imaging. However, their fluorescence brightness is hampered by low quantum efficiency due to the low absorption cross section of Ytterbium and Erbium ions in the near IR. We enhance the efficiency of these particles by investigating the plasmonic coupling of 30nm diameter core NaYF4: Yb, Er upconverting particles (UCNPs) with a gold shell coating. An enhancement of green emission by a factor of five and a three times overall increase in emission intensity has been achieved for single particle spectra. UV-Vis absorption has confirmed the surface plasmon resonance (SPR) of the gold shell to the near IR and transmission electron microscope (TEM) images demonstrates successful growth of a gold shell around the upconversion particle. Time-resolved spectroscopy shows that gold shell coupling changes the lifetime of the energy levels of the Erbium ion that are relevant to the emission process. [Preview Abstract] |
Tuesday, March 4, 2014 12:27PM - 12:39PM |
G50.00005: Extraordinary SPP propagation distance in epitaxially grown silver film Yanwen Wu, Chengdong Zhang, Jisun Kim, Matt Zhang, Liuyang Sun, Chih-Kang Shih, Xiaoqin Li, Yang Zhao, N. Mohammadi Estakhri, Xing Xiang Liu, Andrea Al\`u, Greg Pribil We measured greatly enhanced propagation distances of surface plasmon polaritons (SPPs) on an atomically-smooth epitaxial silver \textit{(Ag}) film beyond what was previously considered possible. These extraordinary propagation lengths approach the fundamental limit determined by the new optical constants measured in these films. We excited and detected the SPPs in reflection geometry. Light incident on a single groove launched the SPPs, which were subsequently detected at a series of output coupling slits with increasing distance from the launching site. We used incident wavelengths of 632nm and 880nm and extracted propagation distances of 22$\mu$m and 42$\mu$m, respectively. Calculations using the optical constants measured on the same film predict distances of 42$\mu$m at 63nm and 155$\mu$m at 880nm. The discrepancy is mainly due to scattering from the 1-2 monolayer fluctuations at the \textit{Ag} surface. The propagation distance extrapolated from our measurements far exceeds the speculated theoretical limit ($\sim$ 5X) in template stripping \textit{Ag} films. [Preview Abstract] |
Tuesday, March 4, 2014 12:39PM - 12:51PM |
G50.00006: Plasmonic Magnetic Nanostructure Farbod Shafiei, Francesco Monitcone, Khai Q. Le, Xing-Xiang Liu, Thomas Hartsfield, Andrea Alu, Xiaoqin Li AFM manipulation technique has been used to position individual 100 nm gold nanospheres into a subwavelength plasmonic metamolecule nanoring consisting of four closely spaced nanoparticles. This structure supported a strong magnetic response coupled to a broad electric responce in the visible range. Asymmetries in the assembled nanoring enable the interaction between electric and magnetic modes, leading to the first observation of a magnetic-based Fano scattering resonance at optical frequencies. Such a metamolecule is suitable building block for negative-index metamaterials. AFM manipulation technique gave us ability to modify the nanostructure in real time while we were monitoring the elctric and magnetic responses of the nanostructure. [Preview Abstract] |
Tuesday, March 4, 2014 12:51PM - 1:03PM |
G50.00007: Assembling Three-Dimensional Optical Stereo-Nanocircuits Jinwei Shi, Sarah Elias, Francesco Monticone, Yanwen Wu, Daniel Ratchford, Xiaoqin Li, Andrea Alu The development level of integration of photonic devices is lagging behind compared with microelectronics, due to diffraction limit and the difficulty of realizing basic functionalities with lumped photonic circuit elements at the nanoscale and achieving versatile operations by combining these elements in large circuits. Here we demonstrate the design, assembly and characterization of various 3D photonic nanocircuits with increasing complexity by accurately positioning a number of metallic and dielectric nanoparticles (NPs) in a reconfigurable way with atomic force microscope (AFM) manipulation, in analogy to what an electrical engineer does when putting together an electronic circuit. The NP clusters are shown to produce the designed spectral response, qualitatively predicted by simple circuit rules, with fixed optical lumped impedance value of each NP for different nanocircuit configurations. Additionally, such nanophotonic circuits exhibit stereo-functionality, i.e., a response that can be controlled by the polarization of impinging light. Our work represents an important step toward transplanting and extending the powerful design tools of electronic circuits to nanophotonic systems. [Preview Abstract] |
Tuesday, March 4, 2014 1:03PM - 1:15PM |
G50.00008: An ``optical diode'' based on surface plasmon cavity modes Michael J. Burns, Fan Ye, Michael J. Naughton We present the discovery and systematic study of a novel optical phenomenon that works like an ``optical diode,'' where the center of an optically thick circular Ag disk surrounded by step gap looks dark when observing in the far field from the top side, and appears bright when seeing from the bottom side. In both cases, the circular step gap circumference appears bright. We call the effect when observing from the top side the ``plasmonic halo,'' and the effect from the bottom side the ``reverse halo.'' In our previous work, we have demonstrated the physical nature of the ``plasmonic halo'' effect: modulation of transmission by the surface plasmon polariton (SPP) drumhead modes.\footnote{F. Ye, M. J. Burns, M. J. Naughton, \textit{Nano Lett}. \textbf{13}, 519-523 (2013).} Here we will explain the ``reverse halo'' effect by a three-step process: coupling from photons to SPPs, interference of SPPs forming cavity modes, and out coupling from SPPs to photons. Full-wave electromagnetic simulations based on finite element method support our theory. We have thus arrived at a thorough understanding of this ``optical diode'' effect, which could have potential applications in biomedical plasmonics, dielectric constant sensing, discrete optical filtering, and photonic logic, among others. [Preview Abstract] |
Tuesday, March 4, 2014 1:15PM - 1:27PM |
G50.00009: Modification of electric and magnetic dipole emission near plasmonic metal David Keene, Rabia Hussain, Natalia Noginova, Maxim Durach Strongly different behavior of magnetic and electric dipole spontaneous emission is observed near plasmonic metal at wavelengths close to the plasmon resonance range. Results are related to different coupling of the dipoles with plasmonic modes, and can be used to study and map modifications of local optical fields in plasmonic systems. We visualize the effects using a simple microscope setup and provide a theoretical description of the effects observed in a planar geometry, based on the dyadic Green's function approach for a layered medium. [Preview Abstract] |
Tuesday, March 4, 2014 1:27PM - 1:39PM |
G50.00010: Control of plasmonic coupling and radiative emission in tip-enhanced photoluminescence Vasily Kravtsov, Samuel Berweger, Joanna M. Atkin, Markus B. Raschke We study plasmon enhanced photoluminescence (PL) as a probe of local fields and plasmonic coupling in metallic nanostructures and nanogaps, and to gain microscopic insight into the mechanisms of tip--sample coupling in tip-enhanced spectroscopy in particular, and the behavior of radiative emitters in the proximity of interfaces in general. For that purpose we measure the laser induced PL response of a nanogap formed by a sharp Au tip and a flat Au sample surface, with distance precisely controlled using shear force feedback. We find three different distance regimes for the PL spectral behavior, characterized by non-monotonic changes in the PL intensity and linewidth, as well as the shift of the emission peak position, on a scale of several nanometers. Through relating the PL signal to the underlying mechanism of plasmonic enhancement, we describe the behavior of the plasmonic resonance of a nanogap of a varying size, where the weak dipole coupling gradually transforms into the higher order multipole and charge transfer coupling modes. The role of the plasmon nonlocality and the influence of the dielectric surface layer are discussed. [Preview Abstract] |
Tuesday, March 4, 2014 1:39PM - 1:51PM |
G50.00011: Experimental demonstration of photon-dipole interactions in quantum dot emission Yikuan Wang, Tianyu Yan, Mark T. Tuominen Light emission occurs spontaneously when electrons at excited states transit to ground state. One may wonder if there is an interaction at play between the atom and the radiation field during light emission. Although theoretical attempts were made as early as 1927, so far this interaction has not been taken into account in the calculation of emission properties of matter because of the lack of recognizable photon-atom interaction in a decisive experiment. Here we show that photoluminescence decay rates of semiconductor quantum dots affected by surface plasmons are dependent on detection angle and polarization of photons, as a result of photon-dipole interactions. Our results demonstrate how a dipole emitter interact with the photon field in the spontaneous emission process, thus provide a basis for controlling light emission through dipole orientation of molecules. This work will directly influence the future design of molecular emitting devices. [Preview Abstract] |
Tuesday, March 4, 2014 1:51PM - 2:03PM |
G50.00012: Dynamics of Excitons in Bare and Organic/Metal coated InP Nanowires Masoud Kaveh, Qiang Gao, Chaennupati Jagadish, Gerd Duscher, Hans-Peter Wagner We investigate the exciton dynamics in bare and organic/metal coated wurzite/zincblende (WZ/ZB) InP nanowires (NW) by temperature-dependent time-integrated (TI) and time-resolved (TR) photoluminescence (PL). Aluminum quinoline (Alq$_{\mathrm{3}})$ as well as Alq$_{\mathrm{3}}$/Mg:Ag covered NW heterostructures are fabricated by organic molecular beam deposition. PL measurements on bare InP nanowires at 15 K reveal two emission bands at 1.45, and 1.48 eV originating from indirect WZ/ZB and point-defect (PD) trapped excitons, respectively. TR PL traces show an approximately single exponential decay for PD trapped excitons with a lifetime of 2 ns and biexponential decay for indirect WZ/ZB excitons with lifetimes of 3.3 ns and 14 ns. In Alq$_{\mathrm{3}}$ covered NWs we observe a stronger emission from both exciton transitions and longer decay times for indirect excitons indicating surface state passivation at the Alq$_{\mathrm{3}}$/NW interface. In Alq$_{\mathrm{3}}$/Mg:Ag NWs the PD trapped exciton emission is notably reduced which is attributed to a fast energy-transfer from free excitons in the WZ segments to plasmon oscillations in the metal film. The emission from indirect excitons is still comparable to the PL yield of bare NWs. [Preview Abstract] |
Tuesday, March 4, 2014 2:03PM - 2:15PM |
G50.00013: Broadband wide angle nearly perfect absorption with polarization-independence in plasmonic absorber based on multiple surface plasmon resonances Sze Fung Lee, King Chun Lai, Kin Wah Yu Nearly perfect absorption (NPA) of electromagnetic waves is useful in building photovoltaic cells, sensors and filters etc. Therefore designs of nearly perfect absorber based on different geometries have been proposed to yield NPA, with different operating frequency bandwidths, sensitivities to angle of incidence (AOI) and polarization of incident light. In this work, a design of broadband, wide AOI and polarization-independent nearly perfect absorber is proposed. The absorber is composed of a composite layer which generates multiple resonance, coated on a reflecting metal. The absorbance is computed to confirm NPA for TM and TE modes. The absorbance depends also on the thickness of the composite layer and this dependence is explained by the hybridized surface plasmon polariton (HSPP) formed inside the absorber. Particularly for TE mode, the fast HSPP wave (with phase velocity larger than the speed of light in vacuum) which coupled efficiently with incident light, can only be generated for proper thickness of layer. The proposed absorber can be one of the candidates for building light harvesting devices because of its efficient energy collection. [Preview Abstract] |
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