Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session Q11: Focus Session: Optical Properties of Nanostructures IV: Optical Antennas and Plasmonics |
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Sponsoring Units: DMP Chair: P. James Schuck, Molecular Foundry, Lawrence Berkeley National Laboratory Room: 305 |
Wednesday, March 18, 2009 11:15AM - 11:51AM |
Q11.00001: Dielectric Optical Antenna Emitters and Metamaterials Invited Speaker: Optical antennas are critical components in nanophotonics research due to their unparalleled ability to concentrate electromagnetic energy into nanoscale volumes. Researchers typically construct such antennas from wavelength-size metallic structures. However, recent research has begun to exploit the scattering resonances of high-permittivity particles to realize all-dielectric optical antennas, emitters, and metamaterials. In this talk, we experimentally and theoretically characterize the resonant modes of subwavelength rod-shaped dielectric particles and demonstrate their use in negative index metamaterials and novel infrared light emitters. At mid-infrared frequencies, Silicon Carbide (SiC) is an ideal system for studying the behavior of dielectric optical antennas. At frequencies below the TO phonon resonance, SiC behaves like a dielectric with very large refractive index. Using infrared spectroscopy and analytical Mie calculations we show that individual rod-shaped SiC particles exhibit a multitude of resonant modes. Detailed investigations of these SiC optical antennas reveal a wealth of new physics and applications. We discuss the distinct electromagnetic field profile for each mode, and demonstrate that two of the dielectric-type Mie resonances can be combined in a particle array to form a negative index metamaterial [1]. We further show that these particles can serve as ``broadcasting'' antennas. Using a custom-built thermal emission microscope we collect emissivity spectra from single SiC particles at elevated temperatures, highlighting their use as subwavelength resonant light emitters. Finally, we derive and verify a variety of general analytical results applicable to all cylindrical dielectric antennas and discuss extensions of the demonstrated concepts to different materials systems and frequency regimes. [1] J.A. Schuller, et al., Phys. Rev. Lett. 99, 107401 (2007) [Preview Abstract] |
Wednesday, March 18, 2009 11:51AM - 12:03PM |
Q11.00002: Quantum Confined Stark Effect for Exciton-Plasmons in Carbon Nanotubes Igor Bondarev, Justice McConnell We study theoretically the perpendicular electrostatic field effect (the quantum confined Stark effect) for excitons and interband plasmons in small-diameter ($<\sim $1nm) semiconducting carbon nanotubes (CNs). The exciton excitation energy and the plasmon energy both shift to the red due to the decrease in the CN band gap as the field increases. However, the exciton red shift is much less than the plasmon one due to the decrease in the absolute value of the (negative) exciton binding energy [1]. This brings the exciton in resonance with the interband surface plasmon. The exciton total energy may be tuned to the nearest interband plasmon resonance this way, to form the strongly coupled exciton-surface-plasmon excitation[2,3]. We propose this effect for the development of CN based tunable optoelectronic device applications in areas such as nanophotonics, nanoplasmonics, and cavity quantum electrodynamics.\\[0pt] REFERENCES: [1] I.V. Bondarev, K .Tatur and L.M. Woods, Phys. Rev. B, submitted. [2] I.V. Bondarev and H. Qasmi, Physica E 40, 2365 (2008). [3] I.V. Bondarev, K. Tatur and L.M. Woods, Optics Communications, to appear in Dec. 2008. [Preview Abstract] |
Wednesday, March 18, 2009 12:03PM - 12:15PM |
Q11.00003: Resonant Plasmonic and Vibrational Coupling in a Tailored Nanoantenna for Infrared Detection Javier Aizpurua, Aitzol Garcia-Etxarri, Thomas W. Cornelius, Shafkat Karim, Frank Neubrech, Annemarie Pucci Gold nanowires are introduced as plasmonic infrared antennas for effective molecular spectroscopy. A novel resonant mechanism involving the interference of the broadband plasmon with the narrowband vibration from molecules is presented in the context of Surface-Enhanced Infrared Absorption (SEIRA). With the use of this concept, we demonstrate experimentally the enormous enhancement of the vibrational signals from less than one attomol of molecules on individual gold nanowires, tailored to act as plasmonic nanoantennas in the infrared. By detuning the resonance via a change in the antenna length, a Fano-type behavior of the spectral signal is observed, which is clearly supported by full electrodynamical calculations. This resonant mechanism can be a new paradigm for sensitive infrared identification of molecular groups. \\[0pt] F. Neubrech {\it et al}. Phys. Rev. Lett. {\bf 101}, 157403 (2008). [Preview Abstract] |
Wednesday, March 18, 2009 12:15PM - 12:27PM |
Q11.00004: A novel near field transducer for efficient energy transfer William Challener, Amit Itagi, Chubing Peng, Nils Gokemeijer, Ganping Ju, Michael Seigler, Edward Gage Interest in the localized surface plasmon resonance (LSPR) of metallic nanoparticles has been piqued by single molecule detection in surface enhanced Raman spectroscopy, scanning optical microscopy with sub-20 nm resolution, particle capture using the optical tweezers effect, and proposed applications in nanolithography and data storage. We have designed a gold near field transducer (NFT) that combines the LSPR effect, the lightning rod effect, and the dual dipole effect. Optical energy that is focused onto the NFT is coupled into a metallic thin film within a spot that is an order of magnitude smaller than the free space wavelength with an efficiency of about 5{\%}. With approximately 40 mW of optical power from a laser diode at a wavelength of 830 nm, data has been recorded at a track width less than 50 nm onto a high coercivity magnetic medium by heating it to its Curie point of 650 K while the medium was rotating at 2700 RPM and the NFT was separated from the medium surface by 15 nm. [Preview Abstract] |
Wednesday, March 18, 2009 12:27PM - 12:39PM |
Q11.00005: Near-field imaging and probe-assisted nano-mechanical control of plasmonic antennas Aitzol Garcia-Etxarri, Isabel Romero, F. Javier Garcia de Abajo, Rainer Hillenbrand, Javier Aizpurua Imaging plasmon-resonant gold nanodisks acting as optical nanoantennas by scattering-type near-field optical microscopy (s-SNOM), we identify weak and strong coupling regimes between the near-field probe and the plasmonic nanoantenna sample. By means of rigorous electrodynamical calculations based on a model system, we find that in the weak coupling regime, s-SNOM can be applied for direct mapping of plasmonic nanoantenna modes, while in the strong coupling regime, the near-field probe allows for high-precision opto-mechanical control of the antenna response. [Preview Abstract] |
Wednesday, March 18, 2009 12:39PM - 12:51PM |
Q11.00006: Direct Near-field Imaging of UV Surface Plasmon of a Bowtie Optical Nano-antenna Liangcheng Zhou, Qiaoqiang Gan, Volkmar Dierolf, Filbert Bartoli Study of Ultraviolet Surface Plasmon Polariton (SPP) is of special interest because of UV light's wide applications. Near-field Scanning Microscopy (NSOM) has been proven to be one of the most effective ways of characterizing SPP modes thanks to its highly localized signal collection from surface with a sub-wavelength resolution. A resolution of 60nm is achieved on our NSOM which is capable of working with deep-UV (down to 244nm) light. By utilizing this NSOM working under collection mode, we directly imaged the UV SPP modes on various nanostructures on an Al/Al2O3 thin film, among which a bowtie antenna structure showed extraordinary quality of both confining UV light field to a sub-wavelength size and enhancing the optical intensity as well. Numerical simulation of said structure is also reported and discussed, revealing that a bowtie antenna is a promising candidate for many uses such as a novel NSOM tip, optical sensors and optical nano-trap etc. [Preview Abstract] |
Wednesday, March 18, 2009 12:51PM - 1:03PM |
Q11.00007: Cavity resonances of metal-dielectric-metal nanoantennas Bhuwan Joshi, Qi-Huo Wei We numerically study the optical properties of metal-dielectric-metal nanoantennas. The nanoantennas consist of two metal nanocylinders stacked vertically with a dielectric disk spacer. The numerical analysis using finite difference time domain method (FDTD) shows that nanoantennas exhibit two types of resonances when the gap between the metal cylinders is below 5nm. One of the resonance corresponds to the antenna resonance, generates a peak in scattering spectra and the other corresponds to cavity resonance, produces multiple dips in the scattering spectra. The multiple dips are corresponding to the different cavity resonant modes; the resonant frequencies of these modes depend upon the gap size between the cylinders. It is found that as the gap size decreases, enormous electric field enhancement can be generated inside the cavity. For a particular gap size, electric field enhancement can be maximized by varying diameter of the dielectric disk and optimum condition is obtained when dielectric disk diameter is roughly half that of the metal cylinders. The cavity resonance can be explained as interference of gap surface plasmons between two metal cylinders. [Preview Abstract] |
Wednesday, March 18, 2009 1:03PM - 1:15PM |
Q11.00008: Plasmonic hysteresis: temperature dependent resonance of vanadium-dioxide coated gold nanoparticle arrays Davon Ferrara, Joyeeta Nag, Eugene Donev, Jae Suh, Richard Haglund The optical properties of metal nanostructures are dominated by the free-electron, or plasmonic, response of the material. In the case of metal nanoparticles, this leads to a resonant extinction with wavelength determined by the particles' size, shape, material, and surrounding dielectric. Vanadium-dioxide has a hysteretic transition from a semiconductor to a metal about 68C accompanied by a change in its structural, electrical and optical properties. Using vanadium dioxide as a thermochromic dielectric switch, we map out the hysteresis of the plasmonic resonance of gold nanoparticle arrays coated with the metal-oxide as a function of temperature. To study this plasmonic dependence on temperature, a sample of 20nm thick Au nanoparticle arrays with various particle sizes and grating constants were coated with a 60nm thick vanadium dioxide film. We find that near the transition, the particle plasmon resonance can shift position over 250nm. Measurements of the line shape show the effects of strong correlation in the vicinity of the switching temperatures. [Preview Abstract] |
Wednesday, March 18, 2009 1:15PM - 1:27PM |
Q11.00009: Surface plasmon lifetime in metal nanoshells A.S. Kirakosyan, T.V. Shahbazyan Lifetime of localized surface Plasmon in metal nanostructures plays important role in many aspects of plasmonics and its applications. In small nanometer-sized spherical particles, the dominant mechanism is size-dependent Landau damping that limits plasmon lifetime to t$<$R/v, where R is nanoparticle radius and v is the electron Fermi velocity. It has long been expected that for other nanostructures, the plasmon lifetime should be similarly determined by their characteristic size. We performed quantum-mechanical calculations of Landau damping in metal nanoshells with dielectric core, and found a significant difference of plasmon lifetime from the expected behavior. In particular, due to electron scattering on two metal surfaces, the damping rate exhibits pronounced quantum oscillations with changing shell thickness. Our calculations explain the results of recent measurements of plasmon lifetime in gold nanoshells. [Preview Abstract] |
Wednesday, March 18, 2009 1:27PM - 1:39PM |
Q11.00010: Finite Size Effects on the Electromagnetic Field Enhancement from Low-dimensional Silver Nanoshell Dimer Arrays Youlin Song, Ke Zhao, Yu Jia, Xing Hu, Zhenyu Zhang Finite size effects on the optical properties of one-dimensional (1D) and 2D nanoshell dimer arrays are investigated using generalized Mie theory and coupled dipole approximation within the context of surface-enhanced Raman spectroscopy (SERS). It is shown that the huge enhancement in the electromagnetic (EM) field at the center of a given dimer oscillates with the length of the 1D array. For an array of fixed length, the EM enhancement also oscillates along the array, but with a different period. Both types of oscillations can be attributed to the interference of the dynamic dipole fields from different dimers in the array. When generalized to 2D arrays, EM enhancement higher than that of the 1D arrays can be gained with a constant magnitude, a salient feature advantageous to experimental realization of single-molecule SERS. [K. Zhao et al, J. Chem. Phys. \textbf{125}, 081102 (2005); Y. L. Song et al, accepted by J. Chem. Phys.] [Preview Abstract] |
Wednesday, March 18, 2009 1:39PM - 1:51PM |
Q11.00011: System-bath approach to electronic effect in Surface Enhanced Raman Scattering Semion Saikin, Roberto Olivares-Amaya, Cesar Rodriguez-Rosario, Michael Stopa, Alan Aspuru-Guzik Raman scattering from molecules is greatly enhanced in proximity of a metal nanoparticle or a rough metal surface. The strong interest in this effect is driven by applications to selective detection of toxic chemicals, warfare agents, etc. The scattering enhancement has two distinct contributions. The electromagnetic effect originates in the field concentration by surface plasmons excited in the metal. The second, electronic or chemical contribution, which is important for molecules in direct contact with the surface, is more controversial. It is controlled by the charge transfer between a molecule and a metal with nanoscale roughness. We develop an open quantum system approach to the formation of charge-transferred states and apply it to describe electronic effect in SERS using specific examples of organic molecules adsorbed on a surface of a silver nanoparticle. [Preview Abstract] |
Wednesday, March 18, 2009 1:51PM - 2:03PM |
Q11.00012: Single molecule surface-enhanced Raman spectroscopy in nanogap structures Daniel Ward, Naomi Halas, Douglas Natelson Single molecule sensitivity in surface enhanced Raman scattering (SERS) is of significant interest to multiple fields of study but has been difficult to demonstrate conclusively. We have developed a planar nanogap structure with single molecule Raman sensitivity ( Nano Lett. 7, 2007; Nano Lett. 8, 2008). Nanogap devices offer a reliable way to probe SERS phenomena often thought to be the hallmarks of single molecule sensitivity: intensity fluctuations and spectral diffusion. We present a series of experiments on intensity fluctuation and spectral diffusion rates as a function of temperature to better understand the mechanism driving these phenomena. We also explore how the gap width affects overall Raman intensity. Additionally, time permitting, we present results on plasmonic light emission from nanogap devices when excited by hot electrons. The spectrum shows intensity peaks at energies well above the excitation energy revealing a wealth of interesting physics. [Preview Abstract] |
Wednesday, March 18, 2009 2:03PM - 2:15PM |
Q11.00013: Plasmonic Nanolens Arrays for Enhanced Raman Spectroscopy E.V. Ponizovskaya, I. Naumov, Z. Li, Jing Tang, A.M. Bratkovsky Surface-enhanced Raman scattering (SERS) is the 4th-order process with regards to a local electric field, $\sim $E$^{4}$, and therefore, may be extraordinarily enhanced well in excess of 10-11 orders of magnitude. The ``chemical' enhancement factor of less clear origin may also reach few orders of magnitude. We are looking at engineering various nanoparticle arrays that may focus local field and may be fabricated in top-down manner or self-assembled. Nanocrystals of Au and Ag with different shapes, such as octahedra, cubes, stars etc and their 2-dimensional and 3-dimensional assembly have been studied for plasmonic applications. One promising way of reaching the enhancement $\ge 10^{12}$is to use arrays of plasmonic nanolenses with with binary or even ternary nanoparticles arrangements with certain patterns. The nanoparticles arrangements were modeled numerically using Finite Difference Time Domain method. and results are compared with the data collected by our team on some fabricated high-performance SERS substrates. [Preview Abstract] |
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