Bulletin of the American Physical Society
APS March Meeting 2010
Volume 55, Number 2
Monday–Friday, March 15–19, 2010; Portland, Oregon
Session J14: Focus Session: Optics of Nanostructures – Plasmons, Nanoantennas, and Quantum Dots |
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Sponsoring Units: DMP Chair: Richard Averitt, Boston University Room: B113 |
Tuesday, March 16, 2010 11:15AM - 11:27AM |
J14.00001: Nanocrystal optoelectronic devices by plasmon-based optical trapping Kenneth Evans, Daniel Ward, Douglas Natelson Optical trapping is an important tool for studying and manipulating nanoscale objects. In conventional laser trapping, the trapping volume is diffraction limited. Recent experiments have shown that subwavelength control of nanoparticles can be achieved by using plasmonic nanostructures, rather than using the laser directly, to generate the electric fields necessary for trapping. We present a numerical model describing the trapping forces on an individual semiconducting nanocrystal in a nanoscale metallic junction, and discuss initial experimental results. Calculations of the fields are performed in COMSOL, a commercial finite element solver package, and the trapping forces are computed using the full Maxwell stress tensor formalism. We propose the use of plasmonic optical trapping in this geometry as a method to fabricate electrically driven, single nanocrystal light-emitting devices. [Preview Abstract] |
Tuesday, March 16, 2010 11:27AM - 11:39AM |
J14.00002: Measurement of electrical field enhancement in plasmonic nanogaps via optical rectification Daniel Ward, Douglas Natelson Planar nanogap structures have been demonstrated to exhibit plasmonically enhanced electrical fields. Electric field enhancements in these structures are sufficiently large to observe single molecule surface enhanced Raman scattering (SERS) (Nano Lett. 8, 919 (2008)). Nanogaps can be integrated into electrical circuits allowing simultaneous optical and electrical characterization of the gap. Nanogaps exhibit an electrical nonlinearity in their tunneling conduction. This nonlinearity results in a rectified current proportional to the square of an applied oscillating voltage. We have found that when illuminated such gaps exhibit a photocurrent proportional to this electrical nonlinearity, suggesting that this rectification process is at work at optical frequencies in these structures. By detecting the optically rectified current in nanogaps and comparing with simultaneously acquired electrical measurements, we infer the plasmonically enhanced local electrical field in the nanogap. Inferred electric field strengths are on the order of 100 times the incident field. This enhancement of the electric field is consistent with the enhancement necessary to observe single molecule SERS. [Preview Abstract] |
Tuesday, March 16, 2010 11:39AM - 11:51AM |
J14.00003: Nanowire Plasmon Resonators Nathalie Snapp, Chun Yu, Dirk Englund, Frank Koppens, Mikhail Lukin, Hongkun Park Strong interactions between light and matter can be engineered by confining light to small volumes. Nanoscale plasmonic structures are capable of confining light well below the diffraction limit; however, building resonant cavities in these devices has proven difficult due to large material losses. We report the design and fabrication of one-dimensional plasmonic crystals utilizing patterned dielectric surrounding low-loss, highly crystalline silver nanowires to make distributed bragg reflectors (DBR) with stopbands of 40-50 nm in the visible range. Introduction of a defect in the DBR causes a resonant feature to appear in the stopband. These plasmonic cavities have a Q of up to 45 in a sub-diffraction limit mode volume. Quantum dots coupled to these devices show modified fluorescence spectra, as well as emission enhancement at the cavity resonance. [Preview Abstract] |
Tuesday, March 16, 2010 11:51AM - 12:27PM |
J14.00004: Ultrafast quantum optics with solid-state nanosystems Invited Speaker: Semiconductor quantum dots and color centers in diamond are promising solid-state systems for fundamental quantum optical experiments and robust quantum information processing. In quantum dots, ultrafast sequences of coherent quantum operations may be envisioned with femtosecond light pulses. We present the first femtosecond pump-probe experiment on a single CdSe quantum dot. In this few-fermion system, Coulomb renormalization and single-photon gain are observed on an ultrafast timescale. The ability to add or remove single photons to and from photon bunches is explored [1]. To not only reach single-electron but also single-photon sensitivity, we present two ideas to efficiently couple light from the far field into nanometer sized objects: metal nanoantennas [2] and dielectric microresonators [3]. Color centers in diamond allow for single spin initialization, manipulation and readout at ambient conditions. We present imaging magnetometry on the nanoscale with a single diamond color center [4]. Furthermore, new concepts to fabricate diamond nanophotonic elements are demonstrated. \\[4pt] [1] F. Sotier et al., Nature Physics 5, 352 (2009). \newline [2] J. Merlein et al., Nature Photonics 2, 230 (2008). \newline [3] M. Kahl et al., Nano Lett. 7, 2897 (2007). \newline [4] G. Balasubramanian et al., Nature 455, 648 (2008). [Preview Abstract] |
Tuesday, March 16, 2010 12:27PM - 12:39PM |
J14.00005: Determining the mechanism of metal-enhanced multiphoton absorption polymerization John Fourkas, Sanghee Nah, Linjie Li, Junjie Hao Multiphoton absorption polymerization has been demonstrated by a number of groups to occur considerably more efficiently near noble metal nanostructures. It is generally assumed that the mechanism underlying this increased efficiency is an increase in the effective two-photon absorption cross-section due to field enhancement from the nanostructure. However, we have recently demonstrated that for small aggregates of gold nanoparticles, multiphoton absorption drives broadband luminescence that can expose a photoresist directly through single-photon absorption. In this talk we will show that the same mechanism is responsible for metal-enhanced multiphoton absorption polymerization (MEMAP) for a range of different metal nanostructures. In fact, we have yet to find a system in which field enhancement leading to enhanced two-photon absorption of a photoinitiator is responsible for MEMAP. These observations suggest that we need to rethink the mechanisms of other nonlinear optical phenomena in metal nanostructures, including surface-enhanced Raman scattering. [Preview Abstract] |
Tuesday, March 16, 2010 12:39PM - 12:51PM |
J14.00006: Plasmons and The Electromagnetic Response of Nanowires Rodrigo Arias, Alejandro Jara, Douglas Mills We present a theory of the nature of plasmons in nanowires, along with the response of such systems to a spatially uniform applied electric field in the plane perpendicular to the symmetry axis of the wire. We confine our analysis to the electrostatic limit, and to modes with infinite wavelength parallel to the wire's symmetry axis. Thus we focus on the limit where the linear dimensions of the cross section are small compared to the wavelength of incoming radiation. We derive integral equations that involve only the electrostatic potential on the boundary of a wire of arbitrary cross section. The formalism leads to a complete description of the potential as well as the lines of electric field in the system. The homogeneous versions of these equations allows one to find the plasmon eigenfrequencies and eigenfunctions, whereas the inhomogeneous equations allow one to generate the response of the nanowire to a spatially uniform applied field. We present numerical studies of the plasmon normal modes and electromagnetic response of nanowires of rectangular cross section, and comparisons to experiments and other calculations. [Preview Abstract] |
Tuesday, March 16, 2010 12:51PM - 1:03PM |
J14.00007: Angular dependence of the transmittance and reflectance of periodic hole arrays Dimitrios Koukis, David Tanner, Arthur Hebard We have measured the transmittance and reflectance of several samples consisting of a periodic array of holes in a metal film as a function of the angle of incidence of the light. The spectra cover the visible and infrared range. For our measurements we used two different polarizations, p-polarization (TM wave) and s-polarization (TE wave), defined by the direction of the electric field vector relative to the plane of incidence. The well-known resonant behavior of the hole arrays is seriously affected by the angle of incidence and differs significantly for the two polarizations. The behavior of the observed experimental data will be reviewed using theoretical considerations. [Preview Abstract] |
Tuesday, March 16, 2010 1:03PM - 1:15PM |
J14.00008: Dependence of transmission resonances on the lateral shift in bilayer subwavelenth metallic hole arrays Z. Marcet, H.B. Chan, Z.H. Hang, C.T. Chan, J.E. Bower, R. Cirelli, F.P. Klemens, W.M. Mansfield, J.F. Miner, C.S. Pai, J.A. Taylor Periodic subwavelength hole arrays in a metal film exhibit enhanced optical transmission at wavelengths where surface excitations are at resonance with the incident light. We fabricated double layer metal films, with identical periodic arrays of subwavelength holes in the two layers. When the two metal films are placed in sufficiently close proximity, two types of transmission resonances emerge. For the surface plasmon mode, the electromagnetic field is concentrated on the outer surface of the entire metallic layer stack. In contrast, for the gap resonance, also known as the guided mode, the field is confined to the gap between the two metal layers. Our measurements indicate that as the two layers are laterally shifted from perfect alignment, the peak transmission frequency of the guided mode decreases significantly, while that of the surface plasmon mode remains largely unchanged, in agreement with numerical calculations. [Preview Abstract] |
Tuesday, March 16, 2010 1:15PM - 1:27PM |
J14.00009: Calculations of optical properties of nanohole systems in metallic films Peter Johansson, Vladimir Miljkovic, Mikael Kall We present a computational study of the optical properties of systems of nanohole system in thin (the typical thickness is less than 100 nm) noble metal films. The Green's tensor technique adopted to layered systems forms the analytical framework to the calculations. We have studied individual holes as well as several interacting holes, and calculated quantities related both to far-field properties such as scattering cross sections and near fields and near-field properties such as resonance energy transfer between molecules. The resonance properties of nanoholes are determined by their size and shape[1]. The interaction between two holes can, at a basic level, be understood as a dipole-dipole interaction between the holes, however, the interaction strength is strongly modulated by the properties of the surface plasmons of the metal film[2]. \\ {[1]}. B. Sepulveda {\it et al}., Opt.\ Express {\bf 16}, 5609 (2008). \\ {[2]}. J. Alegret, P. Johansson, and M. K\"all, New J. Phys.{\bf 10}, 105004 (2008). [Preview Abstract] |
Tuesday, March 16, 2010 1:27PM - 1:39PM |
J14.00010: Plasmonic antenna array at optical frequency based on nanoapertures Ruwen Peng, Zhijian Zhang, Liuyang Sun, Zhan Wang, Feng Gao, Xianrong Huang, Mu Wang We demonstarte here that the plasmonic array based on nanoapertures in ultrathin silver film radiates at optical frequency and behaves as an optical antenna array (OAA). When the incident light illuminates the nanohole array, the localized surface plasmons are excited and serve as electric dipoles. The far-field radiation originates from the coherent superposition of plasmonic emissions on each bank of the aperture. The radiation of OAA presents a strong directivity, which depends on the in-plane rotation of aperture array, and on the polarization and incidence angle of the excitation light as well. We suggest that these features have potential applications in photovoltaics, light-emitting devices, and optical sensors. Reference: Z. J. Zhang, R. W. Peng, Z. Wang, F. Gao, X. R. Huang, W. H. Sun, Q. J. Wang, and Mu Wang, Appl. Phys. Lett. (2008) 93, 171110. [Preview Abstract] |
Tuesday, March 16, 2010 1:39PM - 1:51PM |
J14.00011: Mode life time study of transmission resonances in bilayer subwavelength metallic hole arrays Z.H. Hang, C.T. Chan, H.M. Su, K.S. Wong, H.B. Chan Enhanced optical transmission occurs on bilayer periodic subwavelength hole arrays in metal films at wavelength where surface excitation can be induced by incident light. Two different types of transmission resonances (surface plasmon mode and gap guided mode) with different mode confinement are found in this structure. Simulation at microwave frequencies found that the mode life time of these two resonance modes have different dependence on the gap thickness between the two perforated metallic films. Gap guided modes with long life time was found. The delay time of a short laser pulse at infrared wavelength passing through similar bilayer subwavelength metallic hole arrays was also experimentally measured and large delay time was found to correlate with the two transmission resonances in this system. The experimental results agree with numerical calculations and mode life time simulations. The difference at different wavelengths (microwave and infrared) of these two resonance modes was studied. [Preview Abstract] |
Tuesday, March 16, 2010 1:51PM - 2:03PM |
J14.00012: Plasmon Induced Nanoparticle Movement Driven by Fast Electrons P.E. Batson, A. Reyes-Coronado, A. Rivacoba, J. Aizpurua, P.M. Echenique, R.G. Barrera Nanometer-sized Au clusters, deposited on amorphous carbon, readily move under a sub-Angstrom electron beam, often coalescing with neighboring clusters (\urllink{P.E. Batson, Microsc. Microanal., \textbf{14} 89-97, 2008} {http://dx.doi.org/10.1017/S1431927608080197}). Movement begins before cluster contact and finishes with a few Au atoms remaining bound to the substrate, suggesting that an external applied force, sufficiently large to break cluster-substrate bonds, drives clusters together. Theoretical modelling shows that forces created by swift electron excitation of surface plasmons having bispherical symmetry are directed properly, and are large enough to produce this behavior. For single clusters, beam-cluster forces are weakly attractive, but in the two- cluster case, forces become stronger and are directed along the line connecting the two clusters, producing coalescence. [Preview Abstract] |
Tuesday, March 16, 2010 2:03PM - 2:15PM |
J14.00013: Cross Resonant Quadruple-ridge Apertures for Nanoscale Optical Emitters Akihiro Kirihara, Junichi Fujikata, Toshihiro Nakaoka, Naoto Kumagai, Katsuyuki Watanabe, Shunsuke Ohkouchi, Masayuki Shirane, Shinichi Yorozu, Yasuhiko Arakawa Plasmonic antenna effect in metal nanostructures has gained much interest because of its useful properties for nanophotonic devices such as quantum-dot photon emitters. In this presentation, we report on polarization-independent quadruple-ridge (QR) apertures to improve photon extraction efficiency from single quantum dots (SQD). The QR aperture has four metallic tips protruding perpendicular to each other, which work as a polarization-independent antenna for a SQD just below the tips. We designed the gold QR apertures for SQD devices emitting around 1 um using FDTD simulation, and fabricated them by EB lithography and lift-off technique. By means of transmission spectroscopy, we demonstrated antenna-induced transmission enhancement through QR apertures for any optical polarization. The enhancement factor was more than 10 compared to that through conventional circular apertures. Because our QR aperture works not only as an optical antenna but also as an electrode for SQDs, it will be applicable to electrically-driven single photon generators or detectors. [Preview Abstract] |
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