Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session P36: Focus Session: Plasmon Resonances in Nanostructures |
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Sponsoring Units: DMP Chair: Zachary Levine, National Institute of Standards and Technology Room: Baltimore Convention Center 339 |
Wednesday, March 15, 2006 11:15AM - 11:27AM |
P36.00001: Photoluminescence from a gold nanotip as an example of tabletop Unruh-Hawking radiation. Igor Smolyaninov Conversion of zero-point quantum fluctuations into real thermal photons which may occur in a curved space-time is the main mechanism behind the Hawking radiation and the Unruh effect [1]. Up to date no experimental verification of these effects and the related dynamical Casimir effect has been reported. Here we argue that the recently observed infrared photoluminescence from a gold nanotip, which is mediated by surface plasmons (SP) propagating over a curved metal tip surface [2], constitutes an example of such zero-point to real photon conversion. Since SP wavelength may be very short, a surface plasmon wave packet propagating along a curved metal surface with radius of curvature $R\sim1$ micrometer may be considered as a classical particle (this would correspond to the ray optics approximation). The centripetal acceleration of such particle may be as large as $a\sim c^2/R\sim 10^{22}g$. According to ref. [1], such particle perceives vacuum as a bath of thermal radiation with temperature $T=\hbar a/2\pi kc\sim 1000K$. Nonlinear optical mixing of SPs with the thermal quanta from this bath looks like infrared photoluminescence in the laboratory reference frame. This work was supported in part by NSF grants ECS-0304046, CCF- 0508213 and ECS-0508275. References [1] W.G. Unruh, Phys.Rev.D 14, 870 (1976). [2] M.R. Beversluis, A. Bouhelier, and L. Novotny, Phys.Rev.B 68, 115433 (2003). [Preview Abstract] |
Wednesday, March 15, 2006 11:27AM - 11:39AM |
P36.00002: Surface plasmon dielectric waveguides Christopher Davis, Igor Smolyaninov, Yu-Ju Hung We demonstrate that surface plasmon polaritons can be guided by nanometer scale dielectric waveguides on top of a gold film. In a test experiment plasmons were coupled to a curved 3 micrometer radius dielectric stripe, which was 200 nm wide and 138 nm thick using a parabolic surface coupler. This experiment demonstrates that using surface plasmon polaritons the scale of optoelectronic devices based on dielectric waveguides can be shrunk by at least an order of magnitude. [Preview Abstract] |
Wednesday, March 15, 2006 11:39AM - 11:51AM |
P36.00003: Synthesis and Optical Properties of Star-shaped Gold Nanoparticles Colleen Nehl, Hongwei Liao, Jason Hafner Here we describe the synthesis, structure, and optical properties of ca. 100 nm star-shaped gold nanoparticles. Seed mediated, surfactant directed synthesis yields nanoparticle solutions sufficiently monodisperse that extinction spectra reveal plasmon bands representative of their structure. Single particle spectroscopy measurements demonstrate that these nanoparticles exhibit multispectral, multidirectional polarized scattering. Through correlated structural characterization by electron microscopy, each scattering component can be assigned to the different points on the star-shaped structure. The plasmon resonances were also found to be extremely sensitive to the local dielectric encironment, yielding sensitivities as high as 1.41 eV photon energy shift per refractive index unit. These properties suggest that the star-shaped gold nanoparticles may be highly valuable for certain biosensing and microscopic imaging paradigms. [Preview Abstract] |
Wednesday, March 15, 2006 11:51AM - 12:03PM |
P36.00004: Nanorice: a new hybrid nanostructure P. Nordlander, D. Brandl, F. Le, H. Wang, N.J. Halas The plasmon hybridization method [1] is applied to nanorice, a new metallic nanostructure which combines the properties of two popular tunable plasmonic nanoparticle geometries: nanorods and nanoshells. The particle consists of a prolate spheroidal dielectric core and a thin metallic shell, bearing a remarkable resemblance to a rice grain. The nanorice particle shows far greater geometric tunability of the optical resonance, larger local field intensity enhancements and far greater sensitivity as a surface plasmon resonance (SPR) nanosensor than any previously reported dielectric-metal nanostructure. The tunability of the nanorice particle arises from the interaction of primitive plasmons associated with the inner and outer surfaces of the shell. The results from plasmon hybridization are compared to FDTD simulations. \newline \newline [1] E. Prodan and P. Nordlander, J. Chem. Phys. 120(2004)5444-5454 [Preview Abstract] |
Wednesday, March 15, 2006 12:03PM - 12:15PM |
P36.00005: Photonic Crystal Effects in Surface Enhanced Raman Scattering from Nanocluster/Nanoshell Arrays Ke Zhao, Hongxing Xu, Baohua Gu, Zhenyu Zhang We study the local optical properties of one-dimensional solid nanosphere dimer arrays with large array spacings, using the generalized Mie theory. We have obtained a large Raman cross section enhancement with magnitude of $10^{11}$ purely by electromagnetic effects, which is higher if compared with that of an isolated nanosphere dimer and in the literature. A coupled dipole approximation is used to understand this enhancement and the plasmon resonance shift relative to the isolated dimer. We have also studied the nanoshell dimer array and found even higher enhancement with magnitude of $10^{13}$. Our studies show that the nanoshell arrays with proper spacings have clear advantages in single molecule surface enhanced Raman spectroscopy (SMSERS). [Preview Abstract] |
Wednesday, March 15, 2006 12:15PM - 12:27PM |
P36.00006: Strongly anisotropic optical composites Justin Elser, Evgenii Narimanov, Viktor Podolskiy We study the macroscopic electromagnetic properties of nano-structured meta-materials formed by plasmonic nanowires embedded in a dielectric host. We show that nanowires have a significant effect on the effective dielectric constant of the system even in the case when their concentration is below 15{\%}. The effect of dielectric properties of nanowires as well as the effect of inclusion concentration, shape and local configuration disorder on effective dielectric constant is explored via numerical simulations. Further, we develop an analytical description of the effective dielectric properties of nanowire composites and study the limit of its validity. We demonstrate that it is possible to use plasmonic nanowire composites to construct strongly anisotropic low-loss optical materials. Proposed applications include polarizers, reflectors, high-energy-density nano-waveguides, and the recently discovered non-magnetic low-loss left-handed media. [Preview Abstract] |
Wednesday, March 15, 2006 12:27PM - 12:39PM |
P36.00007: Metal Nanoparticle Enhanced Fluorescence -- Role of Particle Plasmon Resonance Shy-Hauh Guo, Tim Corrigan, Henryk Szmacinski, Ray Phaneuf We report on a systematic investigation of the enhancement of fluorescence by proximity to Ag nanoparticles whose size, shape and spacing are varied systematically using electron beam lithography. Our measurements indicate that enhancement of both absorption and radiative decay takes place. We compare our observations with expectactions based upon coupling to particle plasmons. [Preview Abstract] |
Wednesday, March 15, 2006 12:39PM - 12:51PM |
P36.00008: Role of Cylindrical Surface Plasmons in Enhanced Optical Transmission Michael Haftel, Carl Schlockermann, Girsh Blumberg We investigate the role of cylindrical surface plasmons in enhancing the optical transmission from nanoarrays of dielectric coaxial cylinders embedded in a metal film. Finite difference time domain (FDTD) simulations identify transmission peaks at long wavelengths as being associated with the fields produced by the individual coaxial cylinders, and these peaks move out to increasingly long wavelengths as the dielectric ring becomes narrower. An analysis of cylindrical surface plasmon dispersion relations show that these peaks are due to resonances from surface plasmons propagating on the cylindrical metal-dielectric interfaces whose wave functions increasingly overlap as the ring narrows. The counterintuitive behavior of the wavelength of the peak is a direct consequence of the negative dielectric constant of the metal film and would not occur for a perfectly conducting or dielectric film. This resonant surface plasmon mechanism closely accounts for the dependence of the position of the simulated transmission peaks on ring geometry and the length of the coaxial cylinders. [Preview Abstract] |
Wednesday, March 15, 2006 12:51PM - 1:03PM |
P36.00009: Plasmonic properties of non-concentric nanoshells Y. Wu, H. Wang, N.J. Halas, P. Nordlander The plasmon hybridization method [1]is applied to nanoeggs, i.e., nanoshells with a non-concentric (offset) core. In contrast to concentric nanoshells, the particle exhibits a multitude of dipole active plasmon resonances. These resonances are formed by hybridization of the multipolar plasmon resonances associated with the inner and outer surfaces of the metallic shell. The reduced symmetry introduced by the offset of the core causes a significant admixture of dipolar components in all plasmon modes. The hybridization is shown to depend strongly on the asymmetry of the particle. The results compare very well with results from FDTD simulations. The non-concentric nanoshell particles are shown to provide large electric field enhancements on open-ended surfaces. \newline \newline [1] E. Prodan and P. Nordlander, J. Chem. Phys. 120(2004)5444-5454 [Preview Abstract] |
Wednesday, March 15, 2006 1:03PM - 1:15PM |
P36.00010: Plasmonic properties of the metallic nanosphere/thin wire system. Feng Hao, P. Nordlander The plasmon hybridization method [1] is applied to a metallic nanosphere positioned near an infinitely long metallic wire. The plasmon resonances of the sphere are found to be shifted and to depend on the polarization of the incident light. In the limit of a thin wire, a virtual state consisting of propagating low energy wire plasmons is induced. The state is similar in nature to the virtual thin film state recently predicted and observed for a nanosphere near a thin metallic film [2]. \newline \newline [1] E. Prodan and P. Nordlander, J. Chem. Phys. 120(2004)5444-5454. \newline [2] F. Le, N. Z. Lwin, J.M. Steele, M. Kall, N.J. Halas, and P. Nordlander, Nano Lett. 5(2005)2009-2013. [Preview Abstract] |
Wednesday, March 15, 2006 1:15PM - 1:27PM |
P36.00011: Optical Response of Metal Nanoparticle Chains Kin Hung Fung, Che Ting Chan The excitation of surface plasmon on metal nanoparticles is interesting to many researchers because of its variety of applications. By arranging nanoparticles in different ways, many interesting properties can be observed. For metal nanoparticle chains, there is a red (blue) shift on the plasmon resonant frequency for longitudinal (transverse) excitation. We present the results on this splitting of plasmon resonant frequency for Ag nanoparticle chains with diameters around 10nm, calculated by the multiple scattering theory (MST) and the ways to understand the results using simple models. MST calculations are performed on the extinction of finite silver nanosphere chains embedded in glass matrix. The transmission and reflection of an infinite 2D arrays of silver nanospheres are also calculated to understand the interaction between nanoparticle chains. The results are in agreement with recent experiments. The splitting of plasmon-resonance modes associated with different polarizations of the incident light is further understood by employing simple models. Results on the effect of order and disorder in nanoparticle chains are also presented. [Preview Abstract] |
Wednesday, March 15, 2006 1:27PM - 1:39PM |
P36.00012: Emergence of collective plasmon excitation in a confined one-dimensional electron gas Zhe Yuan, Shiwu Gao We present a theoretical study of the electronic excitation in a confined one-dimensional electron gas~[1], which is utilized to model atomic chains created in recent experiments. The length dependence of the excitation spectra is obtained from the linear response theory within the random phase approximation and time-dependent density functional theory. As the length of the chains increases, the dipole excitation spectra shows a transition from electron-hole pair excitations to collective plasmon excitation. The trend of the length-dependent plasmon resonance is predicted, and the nature of the plasmon resonance is also elaborated. \\ \\ \noindent [1] Shiwu Gao and Zhe Yuan, Phys. Rev. B 72, 121406(R) (2005). [Preview Abstract] |
Wednesday, March 15, 2006 1:39PM - 1:51PM |
P36.00013: Electron energy-loss spectroscopy study of surface plasmons in Au nano-particles. Cheng-Hsuan Chen, Ming-Wen Chu, Jin-Pei Deng, Chung-Yuan Mou We have studied the surface plasmon excitations of $\sim $10 nm Au nano-particles with various shapes (such as sphere, rod, and triangle) by electron energy-loss spectroscopy (EELS) using a 0.2 nm electron probe in a scanning transmission electron microscope (STEM). EELS spectra were investigated as a function of distance from the probe to the nanoparticle surface, i.e., the impact parameter, and four surface plasmon peaks at 10, 15, 24, and 33 eV could be identified in the loss spectra in the 10 to 40 eV range where the dielectric constant of Au is positive (and still less than one). These high energy surface excitations are anomalous and in sharp contrast to the well-known surface plasmon of Au at 2.4 eV in the visible spectral range where the dielectric constant is negative. Spectral imaging studies also conclusively show that these high energy surface excitations are indeed localized at the surface of the nano-particles. [Preview Abstract] |
Wednesday, March 15, 2006 1:51PM - 2:03PM |
P36.00014: Plasmons in the metallic nanoparticle-film system as a tunable impurity problem F. Le, N.Z. Lwin, N.J. Halas, P. Nordlander We show that the plasmon resonances of a metallic nanoparticle interacting with a metallic film is an electromagnetic analog of the spinless Anderson-Fano model [1].~ The three characteristic regimes of this model are realized here, where the energy of the nanoparticle plasmon resonance lies above, within, or below the energy band of surface plasmon states. The latter regime is experimentally observed and identified. Our approach [1] is generalized to describe a nanoshell on a metallic film and to account for the screening effects caused dielectric backgrounds. These three interaction regimes are controlled by film thickness and the aspect ratio of the nanoshell. The results are compared with Finite-Difference Time-Domain (FDTD) simulations using realistic dielectric functions. \newline \newline [1] ~F. Le, N. Z. Lwin, J.M. Steele, M. Kall, N.J. Halas, and P. Nordlander, Nano Lett. 5(2005)2009-2013. [Preview Abstract] |
Wednesday, March 15, 2006 2:03PM - 2:15PM |
P36.00015: \textbf{Surface plasmon interference spectroscopy of metal films} Vitalii Vlasko-Vlasov, Ulrich Welp, Andreas Rydh, John Pearson Circular nanoslits manufactured by focused ion beam in silver films were used to excite surface plasmon polaritons and to generate plasmon interference patterns. Changes of the plasmon interference periods at changing the excitation wavelength were imaged by a near-field scanning optical microscope and scaled by the known nanostructure dimensions allowing precise plasmon wavelength measurements. The plasmon dispersion curves for our film thickness were calculated in different approximations and a proper fitting function for the experimental data was chosen. This allowed to retrieve the frequency dependence of the dielectric function of our silver film, which is different from usually cited Johnson-Christy and Palik data but falls in the range of values reported in literature. The results of fitting indicate to the important role of losses, which can not be neglected in definition of the real part of the dielectric constant even in the Drude region. Our technique is a useful tool for the local characterization of the dielectric function sensitive to the structure of metal films potential for photonics applications. [Preview Abstract] |
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