Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session T8: Plasmonic Phenomena in Metallic Nanostuctures |
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Sponsoring Units: DCMP Chair: Yanwen Wu, University of South Carolina Room: 006C |
Thursday, March 5, 2015 11:15AM - 11:27AM |
T8.00001: Surface Plasmon Instability Leading to Emission of Radiation in Hybrid Semiconductors Godfrey Gumbs, Andrii Iurov, Danhong Huang, Wei Pan An energy conversion approach from a dc electric field to a terahertz wave based on a new generation of hybrid semiconductors by combining two-dimensional (2D) crystalline layers and a thick conducting material is proposed with possible applications as a source of coherent radiation. The hybrid nano-structure may consist of a single or pair of sheets of graphene, silicene or a 2D electron gas as would occur at a semiconductor hetero-interface. When an electric current is passed through a layer, we discover that the low-frequency plasmons may become unstable beyond a critical wave vector $q_c$. However, there is no instability for a single driven layer far from the conductor and the instability of an isolated pair of 2D layers occurs only at ultra long wavelengths. To bring in frequency agility for this spontaneous radiation, we manipulate the surface-plasmon induced instability, which leads to the emission of radiation (spiler), to occur at shorter wavelengths by choosing the conductor electron density, layer separation, distances of layers from the conductor surface and the driving-current strength. Applications of terahertz radiation from spiler for chemical analysis, security scanning, medical imaging and telecommunications are expected. [Preview Abstract] |
Thursday, March 5, 2015 11:27AM - 11:39AM |
T8.00002: Exciton Emission from Uncoated and Plasmonic Gold/Alq3 Coated GaAs-AlGaAs Core-Shell Nanowires Masoud Kaveh, Qiang Gao, Chennupati Jagadish, Gerd Duscher, Hans-Peter Wagner We investigate the exciton emission from uncoated and gold/aluminum quinoline (Alq3) coated GaAs-AlGaAs core-shell nanowires (NW) by temperature- and intensity-dependent photoluminescence (PL). The vertically aligned 100 nm diameter zincblende NWs were grown on GaAs substrate using the Au catalyzed vapor-liquid-solid method. Au/Alq3 coated NW heterostructures were fabricated by organic molecular beam deposition. Intensity-dependent PL spectra show strong and weak emission bands at 1.515 and 1.47 eV at 15 K, which are attributed to the exciton transition and tentatively to an impurity related luminescence, respectively. Plasmonic NWs with an Au coating of nominal 10 nm thickness but without Alq3 spacer layer reveal a significant reduction of the PL intensity for both emission bands compared with the uncoated NW sample. The PL quenching is mainly attributed to an energy-transfer from free excitons in the NWs to plasmon oscillations in the deposited Au film. The plasmonic Au/Alq3 NW samples with same nominal Au layer thickness and Alq3 spacer layer thicknesses of 5 and 10 nm, respectively, reveal PL intensities which are noticeably stronger as in the Au coated NWs without Alq3 layer. The PL yield rises with increasing Alq3 spacer thickness. [Preview Abstract] |
Thursday, March 5, 2015 11:39AM - 11:51AM |
T8.00003: Tailoring the surface plasmon propagation in subwavelength cylindrical structures Hui Kin Kwok, Kin Wah Yu Tailoring the propagation of surface plasmon polariton (SPPs) in waveguides is useful for subwavelength focusing in photonic circuits. We have studied the wave propagation in an array of subwavelength dielectric cylinders and hollow cylinders immersed in a metallic host. Motivated by Prodan et al.(2003) who proposed the hybridization model for the plasmonic response of cylindrical nanostructures, we extend the study to non-zero off-plane wave number to assess the effect of the hybridizaton of SPP modes on the wave propagation in cylindrical structures. The hybridization of SPP modes of cylindrical multi-layer or multi-array geometry allows us to tailor the SPP propagation through the proper separation of the dielectric components as well as their sizes. By means of the electro-optic effect, the tunable refractive index of the material increases the flexibility on the operating frequency range of the dispersion relation. [Preview Abstract] |
Thursday, March 5, 2015 11:51AM - 12:03PM |
T8.00004: Effect of dielectric spacer layers and substrate on SERS with Au nanoparticle arrays Xin Zhang, Robert M. Briber, Oded Rabin The optical response of a plasmonic nanostructure is often highly dependent on the nature of the underlying substrate. To study the effect of the substrate on surface enhanced Raman scattering (SERS), a series of SERS substrates were fabricated consisting of a hexagonal array of Au nanoparticles self assembled on block copolymer films, a silicon oxide (dielectric) layer and a silicon substrate or an Au substrate. The inter-particle distance and the dielectric layer thickness were controlled. The SERS Enhancement Factors (EF) were calculated by comparing the Raman spectra of 4-aminothiophenol adsorbed on the surface of the Au nanoparticles and in a standard solution. The SERS EF were found to be strongly affected by the inter-particle distance and silicon oxide thickness. Changing the inter-particle spacing induced a 10$^{\mathrm{2}}$ variation in the EF, changing the oxide thickness increased EF values by an factor of 10, and changing substrate from Si to Au increased EF by a factor of 10. Maximal enhancement factors were found with oxide layer thicknesses between 30 nm and 50 nm beneath the 30 nm polymer film with Au substrates. This geometry both improved the resonance condition with the probe laser and reduced the absorption by the substrate. This work illustrates that optimization of plasmonic-based sensors should consider both the metallic and the surrounding structures. [Preview Abstract] |
Thursday, March 5, 2015 12:03PM - 12:15PM |
T8.00005: Surface plasmon propagation along smeared metal-dielectric interfaces Andrii Bozhko, Vladimir Drachev, Arkadii Krokhin Propagation of surface plasmons (SPs) along metal-dielectric interfaces is studied for nano-width metallic films with accounting for interface smearing. Smearing is modelled by electron cloud with density decaying exponentially from the metal surface. The level of smearing is controlled by external electric field. The dispersion and electromagnetic field profile of SPs is calculated numerically for different asymmetric smearings. At some point near the smeared interfaces, where dielectric constant is close to zero, strong enhancement of electric field is predicted. Asymmetry of interface smearings breaks the P-symmetry of the system that leads to frequency splitting of SPs degenerated eigenstates and as a result a doublet of resonant states appears. Also, the perturbation theory which explains the features of dispersion spectrum and field profile is developed. [Preview Abstract] |
Thursday, March 5, 2015 12:15PM - 12:27PM |
T8.00006: Generation of hot plasmonic carriers, thermal effects and plasmonic photochemistry in metal nanocrystals Alexander Govorov, Hui Zhang, Lucas V\'azquez, Yurii Gun'ko, Min Ouyang We investigate the effects of generation of hot plasmonic carriers and heat in metal and hybrid nanostructures. In our theory, the problem of hot-electron generation is calculated using the quantum-mechanical approach based on the DFT theory and the equation of motion of the density matrix [1], whereas the problem of heat release is treated classically. The energy distribution of optically-excited plasmonic carriers is very different in metal nanocrystals with large and small sizes. We found that the hot-electron generation is efficient only for nanocrystals with very small sizes or in nanocrystals with plasmonic hot spots. The physical reason for the above behaviors is non-conservation of momentum in a nanocrystal. Using the newly-developed kinetic DFT theory, we also describe the effect of breaking of the plasmon resonance into multiple peaks in small nanocrystals. Finally, the generation of plasmonic holes via the interband transitions leads to efficient photochemistry [2]. The results obtained in this study can be used to design a variety of plasmonic nanodevices for photocatalysis and photodetectors.\\[4pt] [1] A.O. Govorov, et al., \textit{NanoToday}, 9, 85 (2014).\\[0pt] [2] L. Weng, et al., \textit{Nature Commun.} 5, 4792 (2014). [Preview Abstract] |
Thursday, March 5, 2015 12:27PM - 12:39PM |
T8.00007: Tunable plasmons in atomically thin gold nanodisks Alejandro Manjavacas, Javier Garcia de Abajo The ability to modulate light at high speeds is of paramount importance for telecommunications, information processing, and medical imaging technologies. This has stimulated intense efforts to master optoelectronic switching at visible and near-infrared (vis-NIR) frequencies, although coping with current computer speeds in integrated architectures still remains a major challenge. Here [1] we show that atomically thin noble metal nanoislands can extend optical modulation to the vis-NIR spectral range. We find plasmons in thin metal nanodisks to produce similar absorption cross-sections as spherical particles of the same diameter. Using realistic levels of electrical doping, plasmons are shifted by about half their width, thus leading to a factor-of-two change in light absorption. These results are supported by a microscopic quantum-mechanical calculations based on the random-phase approximation (RPA), which we compare with classical simulations obtained solving Maxwell's equations using tabulated dielectric functions. Both approaches result in an excellent agreement for nanodisks with diameters above 13 nm, although quantum confinement and nonlocal effects play an important role for smaller sizes. [1] A. Manjavacas and F.J Garcia de Abajo, Nat. Commun. (2014). [Preview Abstract] |
Thursday, March 5, 2015 12:39PM - 12:51PM |
T8.00008: Plasmon-induced Hot Carriers in Metallic Nanoparticles Jun Liu, Alejandro Manjavacas, Vikram Kulkarni, Peter Nordlander Plasmon-induced hot carrier formation is attracting an increasing research interest due to its potential for applications in photocatalysis, photodetection and solar energy harvesting. Here [1] we develop a theoretical model for the plasmon-induced hot carrier process and apply it to spherical silver nanoparticles and nanoshells. We show that the inclusion of many-body interactions has only a minor influence on the results. Using the model we calculate the rate of hot carrier generation, finding that it closely follows the spectral profile of the plasmon. Our analysis reveals that particle size and hot carrier lifetime play a central role in determining both the production rate and the energy distribution of the hot carriers. We characterize the efficiency of the hot carrier generation process by introducing a figure of merit that measures the number of high energy carriers generated per plasmon. Furthermore, we analyze the spatial distribution and directionality of these excitations. [1] A. Manjavacas, J. G. Liu, V. Kulkarni, P. Nordlander ACS Nano (2014) [Preview Abstract] |
Thursday, March 5, 2015 12:51PM - 1:03PM |
T8.00009: Bi-anisotropy in a metallic nanoparticle ring Liuyang Sun, Tzuhsuan Ma, Seung-Cheol Yang, Jinwei Shi, Irving Martinez, Gaehang Lee, Gi-Ra Yi, Gennady Shvets, Xiaoqin Li Optical bi-anisotropy refers to magnetoelectric coupling effect, where electric (magnetic) polarization is excited by magnetic (electric) field of the incident light, and the induced polarization and incident field are at different directions. In the field of metamaterials, bi-anisotropy effects have been previously examined in various systems with broken symmetry, such as split rings and Pi-shaped or S-shaped resonators. We investigate bi-anisotropy in the visible frequency range in an asymmetric nano-ring system consisting of four nearly identical gold nanoparticles, in which electric and magnetic dipoles interact with each other. We arrange the nanoparticles into a designed ring geometry using atomic force microscopy manipulation method. Using dark field scattering spectroscopy, we observe that the magnetic dipole is either enhanced or suppressed under different excitation conditions. These results are relevant in designing negative index metamaterials, nano-sensors and other plasmonic devices. [Preview Abstract] |
(Author Not Attending)
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T8.00010: Non-reciprocal Bands by Symmetry Breaking in One-way Magnetized Plasmonic Double Chain System Chi Wai Ling, Kin Hung Fung Non-reciprocity is a key component to provide one-way propagation in one dimensional (1D) optical waveguides, which enables applications like isolators and switches. Plasmonic chains, formed by spatial periodic metal nanoparticles, are subwavelength 1D optical waveguides. Coupled plasmon modes on the chains are characterized by dispersion relation $\omega(k)$, in which $k$ is the wave vector. It has been shown that the spectral reciprocity $\omega(-k)=\omega(k)$ can be protected by either time reversal ($T$) or inversion ($P$) symmetry. However, breaking of ($P$) and ($T$) symmetries are not sufficient to achieve $\omega(-k)\neq\omega(k)$. We use a magnetized plasmonic double chain system to show that breaking pi-rotation time-reversal ($RT$) symmetry is also a necessary condition. [Preview Abstract] |
Thursday, March 5, 2015 1:15PM - 1:27PM |
T8.00011: Controlling spontaneous emission rates of quantum dots with plasmonic nanopatch antennas Thang Hoang, Gleb Akselrod, Christos Argyropoulos, Jiani Huang, David Smith, Maiken Mikkelsen The radiative processes associated with quantum emitters can be strongly enhanced due to intense electromagnetic fields created by plasmonic nanostructures. Here, we experimentally demonstrate large enhancements of the spontaneous emission rate of colloidal quantum dots coupled to single plasmonic nanopatch antennas. The antennas consist of silver nanocubes (75 nm) coupled to a gold film separated by a thin polyelectrolyte spacer layer ($\sim$1 nm) and core-shell CdSe/ZnS quantum dots ($\sim$6 nm). By optimizing the size of the nanopatch antenna, the plasmonic mode is tuned to be on resonance with the quantum dot emission. We show an increase in the spontaneous emission rate by a factor of 880 (Purcell factor) and a 2300-fold enhancement in the total fluorescence while maintaining a high radiative quantum efficiency of $\sim$50 $\%$. The nanopatch antenna, as demonstrated here, offers highly directional and broadband radiation that can be tailored for emitters from the visible to the near infrared, providing a promising approach for the spontaneous emission control of single quantum emitters. [Preview Abstract] |
Thursday, March 5, 2015 1:27PM - 1:39PM |
T8.00012: Probing plasmons in three dimensions in a scanning transmission electron microscope Jordan Hachtel, Anas Mouti, Daniel Mayo, Claire Marvinney, Richard Mu, Richard Haglund, Stephen Pennycook, Matthew Chisholm, Sokrates Pantelides The optical behavior of nanostructured materials is of significant interest across many fields. Surface plasmons and their interactions with emitters in nanoscale devices allow us to control light below the coherence limit. By understanding the nature of plasmonics at the local level we can move towards unlocking the full potential of photonic devices. To this end, we examine plasmonic Ag nanoparticles suspended on insulating nanowires by combining cathodoluminescence spectroscopy, electron energy loss spectroscopy, and high resolution annular dark field imaging in a scanning transmission electron microscope. The complementary nature of CL and EELS allow us to extract optical data from a randomly shaped and oriented nanoparticle, and understand its plasmonic behavior in all three spatial dimensions. [Preview Abstract] |
Thursday, March 5, 2015 1:39PM - 1:51PM |
T8.00013: Band modulation and in-plane propagation of surface plasmons in composite nanostructures Ren-Hao Fan, Di-Hu Xu, Kun Zhang, Ru-Wen Peng, Mu Wang In this work, we have experimentally and theoretically studied band modulation and in-plane propagation of surface plasmons (SPs) in composite nanostructures with aperture arrays and metallic gratings. It is shown that the plasmonic band structure of the composite system can be significantly modulated because of coupling between the aperture and the grating. By changing the relative positions between these optical components, the resonant modes would shift or split. And the resonant SP modes launched on the structure surface can be effectively modified by the geometric parameters. Further, we provide an experimental observation to directly show the SP in-plane propagation by using far-field measurements. Our study offers a convenient way for observing the SP propagation in far field, and provides unique composite nanostructures for possible applications in subwavelength optodevices, such as optical sensors and detectors.\\[4pt] References: D. H. Xu, K. Zhang, M. R. Shao, H. W. Wu, R. H. Fan, R.W. Peng, and Mu Wang, Optics Express, 22, 25700 (2014); R. H. Fan, L. H. Zhu, R. W. Peng, X. R. Huang, D. X. Qi, X. P. Ren, Q. Hu, and Mu Wang, Physical Review B, 87, 195444 (2013). [Preview Abstract] |
Thursday, March 5, 2015 1:51PM - 2:03PM |
T8.00014: ABSTRACT WITHDRAWN |
Thursday, March 5, 2015 2:03PM - 2:15PM |
T8.00015: Study on electrostatic resonance of nanoprisms with sharp corners Wai Soen Chan, Ka Ki Ng, Kin Wah Yu We have studied the electrostatic resonance of metal nanoprisms with sharp corners numerically. We consider an infinite metal cylinder with polygonal base, e.g. square. The incident electric field lies in the plane of cross-section of the cylinder. Yu and co-workers proposed Green's function formalism (GFF) to numerically calculate the electric potential and field distribution in plasmonic systems. We will adopt the scheme to demonstrate the effect of sharp corners, particularly on the effect of electrostatic resonance spectrum, as in the spectral analysis proposed by Bergman and Milton. Hetherington and Thorpe investigated the conductivity of a sheet containing dilute inclusion with sharp corners, they made use of a conformal mapping approach to calculate the conductivity from circular inclusions. Helsing, McPhedran and Milton also investigated the optical properties of a metamaterial lattice with inclusions having sharp corners. We study the possibility of improving numerical accuracy by combining the conformal mapping approach and GFF. We may extend similar approach to investigate the properties of plasmonic systems, for examples nanoboties and nanostars. [Preview Abstract] |
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