Vivian Ferry, University of Minnesota
Jill Millstone, University of Pittsburgh
Ming Tang, Univ of California-Riverside
Joel Yang, Singapore University of Technology and Design
Z3: Hybrid Nanophotonics
Tuesday PM, April 07, 2015
Moscone West, Level 2, Room 2004
2:30 AM - *Z3.01
Hybrid Nanophotonics: Coupling Light with Other Degrees of Freedom at the Nanoscale
Albert Polman 1
1FOM Institute AMOLF Amsterdam NetherlandsShow Abstract
The research field of nanophotonics has made tremendous progress in the past 10 years. Many of these achievements result from the increasing degree of control over nanofabrication and nanocharacterization that has evolved in the past years. Taking advantage of the extreme control over nanophotonic light fields that we have today, we are now in an ideal position to bring the photonics field a next step further, and to investigate the coupling of light with other degrees of freedom such as nanoscale mechanical motion, acoustic phonons, electron spins and excitons.
We will illustrate this emerging new trend of hybrid nanophotonics with several characteristic examples:
- plasmonic optomechanical oscillators: we demonstrate the integration of optically resonant plasmonic nanocavities with silicon-nitride-membrane mechanical oscillators. In these hybrid structures mechanical motion is transduced to scattered optical fields, enabling measurements of displacement sensitivity down to the picometer level.
- plasmonic transparent conductors: we shows how resonant plasmonic nanowire networks serve both as efficient light coupling/trapping geometries and low-resistivity electrical current collectors. We show the integration of nano-imprinted silver nanowire networks with high-efficiency silicon heterojunction solar cells, polymer solar cells, and present their possible use in touch-screen displays.
- cathodoluminescence microscopy: the high-energy electron beam in an electron microscope is coupled to resonant modes in photonic nanostructures, enabling spatial mapping of optical modes with deep-subwavelength resolution, as we will show. This technique provides the “purest” form of optical excitation spectroscopy, as a single electron drives individual polarizable nanophotonic building blocks.
Hybrid nanophotonic concepts will lead to new devices and functionality such as mechanical sensors, RF signal processing, bio-sensors, quantum information processing, ultra-high efficiency solar cells, light-emitting diodes, opto-electronic integrated circuits, imaging systems, and much more.
3:00 AM - Z3.02
Photon-Spin-Induced Electric Hall Effect Enabled by a Metasurface
Xingjie Ni 1 Jun Xiao 1 Sui Yang 1 Yuan Wang 1 Xiang Zhang 1
1University of California, Berkeley Berkeley United StatesShow Abstract
Classical polarized light carries spin and reveals spin-orbit coupling when propagating along a curved trajectory, however this interaction typically is weak. Utilizing a large phase-gradient, a metasurface can greatly enhance this interaction because it can bend light abruptly within an extremely small thickness due to the large induced momentum. Conceivably, this strong photonic spin-orbit coupling on a metasurface could drive the electrons collectively and lead to direct electric Hall currents flowing transversely to the light-bending direction, even at normal incidence and without external magnetic fields. Yet such a photon-spin-induced electric Hall effect has never until now been demonstrated. Here we report the first observation of this direct coupling between photon spin and electron orbital momenta on a metallic metasurface consisting of complementary nanoantennas. By inputting opposite photonic spins, we directly detect the changes inversion of the transverse current direction, with the longitudinal current (induced by the photon-drag effect) being constant. This effect enables an electrical way of detecting photonic spin-orbit interactions and provides a viable route to directly integrate conventional electronic chips with the additional degrees of freedom from the spin and orbital angular momenta of light for future information processing and communication applications
3:15 AM - Z3.03
Optical Matter: Self-Organization of Plasmonic Nanoparticles in Optical Fields
Zijie Yan 1 Norbert F Scherer 1
1University of Chicago Chicago United StatesShow Abstract
Optical matter is a unique class of materials. Typical optical matter is consisting of dielectric microparticles that are self-organized and stabilized by optical binding forces in an optical field. Noble metal nanoparticles usually exhibit strong scattering in the visible light spectrum, resulting in strong optical binding forces that offer the opportunity to construct optical matter from nanoparticles. Here we report our recent work on controlling and tailoring the self-organization of plasmonic nanoparticles in structured optical fields. Structurally stable 2D and 3D clusters with various geometries have been photonically synthesized from Ag nanoparticles with nanometer scale precision in their inter-particle separations. In particular, we show how Ag nanoparticles organize themselves in response to the optical trap shape, intensity gradient, phase gradient, polarization of light, and even the spatial assembly pathways. Our work paves the way for rational design of photonic clusters in optical fields, and we envision that these photonic clusters will find applications in various areas, such as sensing and quantum optics.
3:30 AM - Z3.04
Enantioselective Optical Trapping with Coaxial Plasmonic Aperture
Yang Zhao 1 Amr Saleh 1 Chi-Sing Ho 1 Jennifer A. Dionne 1
1Stanford University Stanford United StatesShow Abstract
Enantiomers are pairs of chiral molecules that are non-superimposable mirror images of each other. The handedness of enantiomers is highly related to their biological function, and effective separation of enantiomers is crucial for the development of functional drugs. Since enantiomers are identical in their chemical composition and mass, existing methods of enantiomer separation largely rely on the unique ways in which each molecule in an enantiomeric pair interacts with other chiral reagents. Here we introduce a novel method of separating enantiomers using optical forces. To generate forces of sufficient strength to trap single molecules, we use a plasmonic coaxial optical trap composed of a 120-nm-diameter silver core and a 25-nm silicon dioxide channel. The coaxial resonator thickness is 150 nm, which provides two strong transmission peaks at 487 nm and 702 nm, corresponding to the Fabry-Perot resonances of the resonator. When light is scattered from the aperture, a large field gradient is generated close to it; linearly-polarized light can provide up to 1.8 pN of lateral force per 100 mW of transmitted power, sufficient to capture dielectric nanoparticles as small as 10 nm in diameter at 20 nm above the coaxial aperture. Interestingly, the near-fields of our coaxial aperture also generate forces that can differentiate between different chiral structures. The two distinct lateral forces arising from chiral molecules interacting with the coaxial aperture are related to the optical rotation dispersion and the circular dichroism of the molecule, and can be derived from electromagnetic chiral density and the energy flow vortex. To calculate the optical forces exerted selectively on R and S enantiomers, we use a combination of finite difference time domain simulations and analytic methods. We consider a 10-nm-diameter dielectric chiral particle (similar in size to a typical large protein) placed 20 nm away from the aperture. Our calculations indicate that, for left-handed circularly polarized illumination, the total maximum transverse force can reach 0.9pN/100mW for the S enantiomer and 0.3pN/100mW for the R entantiomer. Importantly, these forces are in opposite directions: the S enantiomer is attracted toward the trap, while the R enantiomer is repelled. Such significant differences in both magnitude and sign of the transverse forces for the enantiomer pairs result in large differences in trapping potentials: we observe a maximum trapping potential depth of -7.6kT per 100mW transmitted power for the S-enantiomer and a positive trapping potential for the R enantiomer. On-going experiments are employing atomic force microscopy to directly measure these forces and to maneuver single chiral molecules with a specific handedness by switching polarization states. Our presentation will describe this theoretical and experimental work and discuss optimized coaxial arrays for all-optical enantiomer-pure chemical synthesis and chiral drug purification.
3:45 AM - Z3.05
Circularly Polarized Light-Induced Magnetization in Plasmonic Noble Metal Nanostructures
Matthew Sheldon 1
1Texas Aamp;M University College Station United StatesShow Abstract
Fundamentally plasmon oscillations are an opto-mechanical phenomenon. Incident optical fields induce the coherent motion of electrons that produce large fluctuations of charge density at ‘hot spots&’ in resonant structures. Despite these large fluctuations, during linearly polarized illumination a resonant structure, e.g. a metallic nanorod, will necessarily assume a uniform charge distribution twice during each optical cycle. This behavior mimics the electrical field vector of the linearly polarized excitation, which must also have zero magnitude in the plane perpendicular to the direction of propagation twice during an optical cycle. In contrast, the electrical field vector of circularly polarized light has constant magnitude. During an optical cycle, the electric field vector rotates in the plane normal to the wave propagation. Consequently, if plasmonic structures are resonant with circularly polarized excitation, they can exhibit regions of strongly modified carrier density for the duration of the optical cycle.
Here, we study a class of achiral toroid and ‘sun burst&’ patterned resonant plasmonic nanostructures that show persistent, circulating charge density waves during circularly polarized illumination. The direction of the continuously circulating wave (clockwise or counterclockwise) depends on the handedness of the incident beam. Our interest stems from whether these charge density waves can support circular electric currents (DC) manifest experimentally as static magnetic fields during illumination. Using full-wave optical modeling (FDTD method), and mechanistic calculations of the circulating potential acting on the electronic density of states in the toroid resonators, we outline the conditions that maximize optical excitation of circulating electric currents for the case of Au and Ag resonators. We show that in the limit of very weak coupling to the solenoid-like electron transport, or when < 1 x 10-6 % of the electron population that contributes to the charge density wave enters the circular transport modes, relatively strong magnetic fields, > 1 G, can be expected. We discuss scanning probe measurements for monitoring the induced magnetic field, as well as the relationship between this phenomenon and the inverse faraday effect observed in continuous media.
Z4: Nanoscale Light-Matter Interactions
Tuesday PM, April 07, 2015
Moscone West, Level 2, Room 2004
4:30 AM - *Z4.01
Scalable Plasmonic Structures for Control of Emission by Quantum Dots
Ann Roberts 1 Jasper Cadusch 1 Timothy James 1 3 Evgeniy Panchenko 1 Stuart K Earl 1 3 Nicholas Kirkwood 4 Kevin Webb 2 Paul Mulvaney 4
1The University of Melbourne Melbourne Australia2Purdue University West Lafayette United States3Melbourne Centre for Nanofabrication Clayton Australia4The University of Melbourne Melbourne AustraliaShow Abstract
The recent demonstration of resistless nano-imprint lithography (RNIL) as a scalable technique for the fabrication of nanoscale structures in metallic films provides great promise for the mass production of plasmonic devices. Computational and experimental studies indicate that nanocavities in a metallic film exhibit distinct localized resonances. These cavity resonances are accompanied by strongly enhanced and localized electric and magnetic fields and can modify the lifetime and other emission properties of quantum sources such as quantum dots, NV centers in nanodiamond and fluorescent molecules. Furthermore, cavities produced by RNIL support a higher energy, lowest-order, localized surface plasmon mode than a similarly sized dielectric-backed aperture. Applications for these nanocavities include plasmonic color filters, enhanced solar energy harvesting and the production of novel polarization states. Here we demonstrate enhanced fluorescence of CdSe/CdS/ZnS core-shell quantum dots (QDs) via coupling to plasmonic nanocavities imprinted using RNIL into a silver film.
A silicon master template was patterned using electron beam lithography and reactive ion etching. The pattern consisted of rectangular nanorods in a periodic array, with a period of 300 nm. The pattern was transferred to a 360 nm thick silver film on a silicon substrate using RNIL with a force of 19 kN at room temperature. The resulting cavities were 200 nm long by 60 nm wide by 40 nm deep. The QDs were mixed with SU8 2005 and then drop-cast over the sample and cured.
Fluorescence microscopy was performed on the sample by pumping the QDs with a 532 nm pulsed laser and collecting the 650 nm emission. Time correlated single photon counting (TCSPC) lifetime measurements indicate that excited state lifetimes of the QDs in the vicinity of the nano-imprinted plasmonic nanocavities are reduced. Preliminary results indicate around a 4-fold brightness enhancement and a lifetime reduction of around 70%, when compared to the QD-SU8 matrix on an unpatterned Ag film.
This work was performed in part at the Melbourne Centre for Nanofabrication (MCN) in the Victorian Node of the Australian National Fabrication Facility (ANFF). This research was supported under the Australian Research Council's Discovery Projects funding scheme (project number DP110100221) and a Melbourne Centre for Nanofabrication Technical Fellowship.
5:00 AM - Z4.02
Strong Coupling in Plasmonic Systems and Their Interaction with Moleucles
Adi Salomon 1
1Bar-Ilan University Ramat Gan IsraelShow Abstract
We study the optical properties of molecules deposited metallic nanostructures with respect to the free molecules. We show theoretically and experimentally that molecular excited states can be strongly coupled to plasmonic modes. Upon coupling new hybrid states are form, the lower and the higher polariton. These modes have the characteristic of both molecular and plasmonic states. As the coupling strength grows, a new mode emerges, which is attributed to long-range molecular interactions mediated by the plasmonic field. The new, molecular-like mode repels the polariton states, and leads to an opening of energy gaps. By tuning the plasmonic modes to be on/off resonance with respect to molecular system excited state, one can shift these hybrid modes and by that modify the photophysical and even the chemical properties of these molecules, and form a new kind of tunable hybrid materials.
In the same aspect, we study and demonstrate coupling between plasmonic modes of metallic nanocavities (holes). The metallic nanocavities display long range coupling at distances of hundreds of nanometers for selected hole distance/wavelength combinations. Such strong coupling drastically changes the symmetry of the charge distribution around the nanocavities as is evidenced by the nonlinear optical response of the medium. Upon coupling, the emission intensity is strongly dependent on the fundamental beam polarization, and is either suppressed or enhanced.
middot; From Individual to coupled metallic nanocavities. Salomon, A.; Prior, Y. ; Kolkowski, R.; Zyss,J.; Journal of optics, accepted 2014
middot; Role of mode degeneracy in molecule-surface plasmon strong coupling. Salomon A. Wang, S. Hutchison, J.A., Genet, C. Ebbesen, T.W. accepted ChemPhysChem 2013
J. Phys. Chem. C, 2013, 117 (43), pp 22377-22382
middot; Collective Plasmonic-Molecular Modes in the Strong Coupling Regime Salomon, A.; Gordon R.J.; Prior, Y.; Seideman, T.; Sukharev, M.;
Phys. Rev. Lett 109, 073002, 2012
middot; Molecule - light complex: dynamics of hybrid molecule - surface plasmon states. Salomon, A. Genet, C. and Ebbesen, TW. Angewandte Chemie, 48, Pages: 8749-8751, 2009.
5:15 AM - Z4.03
Quantum Plasmonic Waveguides and Resonators
Stephan Kress 1 Felipe Antolinez 1 Patrizia Richner 2 Sriharsha Jayanti 1 David Kim 1 Kevin McPeak 1 Dimos Poulikakos 2 David J. Norris 1
1OMEL, ETH Zurich Zurich Switzerland2LTNT, ETH Zurich Zurich SwitzerlandShow Abstract
Quantum optics involves the coupling of quantum emitters to their electromagnetic environment. Because this coupling is related to the concentration of the optical field, it is typically constrained by the diffraction limit of light. One way to circumvent this limitation is by moving to quantum plasmonics, which uses surface plasmon polaritons (SPPs) instead of photons. However, despite the advantages of this approach, quantum plasmonics has not yet been fully explored, largely due to the difficulty of creating the necessary structures. We address this problem by combining state-of-the-art quantum emitters with plasmonic structures (waveguides and reflectors) that approach theoretical performance limits. We synthesize highly luminescent colloidal quantum dots (photoluminescence quantum yields >90%) and precisely place them on template-stripped silver wedge waveguides. We demonstrate efficient coupling of the quantum-dot emission into guided plasmonic modes in the waveguide. In addition, by adding efficient reflectors, high-Q plasmonic resonators are obtained. More generally, the flexibility and fidelity of the resulting quantum plasmonic systems indicates that they will enable a broad set of nanoscale quantum optical measurements and devices.
5:30 AM - Z4.04
Plasmo-Photonic Crystals: Weak and Strong Coupling of Their Resonances with Excitons and Preservation of Entanglement
Renaud Valleacute;e 1 Simona Ungureanu 1 Pierre Fauche 1 Branko Kolaric 2 Laurent Olislager 3 Philippe Emplit 3 Serge Massar 3
1Centre de Recherche Paul Pascal (CRPP, CNRS, UPR8641) Pessac France2Universiteacute; de Mons Mons Belgium3Universiteacute; Libre de Bruxelles Bruxelles BelgiumShow Abstract
Light-matter interaction probed at the nanoscale attracts much attention nowadays, both for its fundamental interest and potential applications, ranging from all-integrated optics to single photon sources .
Hybrid plasmo-photonic 2D crystals exhibit a complex resonance pattern, which has been characterised using both numerical simulations and measurements of the electric near-field patterns obtained with a scattering scanning near-field optical microscope (s-SNOM) . We show that the resonance modes exhibited by such a hybrid nanostructure can be recovered in the far-field by using narrow-band fluorescence nano-reporters. To this end, different types of semiconductor quantum dots (QDs), acting as nanoreporters of the local interactions, were dispersed on top of these hybrid structures. We show that the emission rates are affected, in a unique way, by the complex interaction occurring between the plasmo-photonic modes and the excitons.
We also report on the experimental observation of an asymmetric wavelength-dependence of the emission rate enhancement in such 2D crystals . This feature strongly contrasts with the traditional Lorentzian line shape exhibited at a resonance by the Purcell factor. This unusual dispersive behavior is shown to be reproducible for different combinations of emitters and structures. It is further retrieved from FDTD simulations. It is mainly due to the fact that a hybridized mode, resulting from the coupling of a Bragg and a SPP modes, is coupled to the emitters. Further studies of the emission detuning by hybrid plasmo-photonic structures are expected to benefit many related fields and notably sensing and bio-sensing technologies.
Furthermore, we show experimentally that frequency-bin entangled photons can propagate through these plasmo-photonic nanostructures . Our measurements clearly show the robustness of frequency-bin entanglement, which survives after interactions with the plasmo-photonic structures, offering possibilities for a variety of applications in which quantum states can be encoded into the collective motion of a many-body electronic system without demolishing their quantum nature.
Finally, we show some recent investigations of the strong coupling regime between excitons and the resonances modes of such plasmo-photonics structures, the so-called "excimons".
 W.L. Barnes, A. Dereux and T.W. Ebbesen, Nature 424, 824 (2003)
 S. Ungureanu, B. Kolaric, J. Chen, R. Hillenbrand and R.A.L. Vallée, Nanophotonics, 2, 173, (2013)
 P. Fauché, S. Ungureanu, B. Kolaric, R.A.L. Vallée, Journal of Materials Chemistry C, 2014, DOI: 10.1039/C4TC01787K
 L. Olislager, B. Kolaric, W. Kubo, T. Tanaka, S. Ungureanu, R.A.L. Vallée, P. Emplit, S. Massar, in preparation.
5:45 AM - Z4.05
Engineer Light Interaction: A New System at the Nanoscale
Alberto Casadei 1 Esther Alarcon-Llado 1 Emanuele Francesco Pecora 2 Jacob Trevino 3 Carlo Forestiere 4 Daniel Rueffer 1 Eleonora Russo-Averchi 1 Martin Heiss 1 Federico Matteini 1 Goezde Tuetuencueoglu 1 Luca Dal Negro 4 Anna Fontcuberta i Morral 1
1Ecole Polytechnique Feacute;deacute;rale de Lausanne (EPFL) Lausanne Switzerland2Stanford Univ Stanford United States3City Univ of New York New York United States4Boston University Boston United StatesShow Abstract
Semiconductor nanowires (NWs) are filamentary crystals with a diameter of few tens of nanometers. Thanks to their dimensions and high refractive index, have the ability to collect and trap the light into a sub-wavelength volume . Metal nanostructures have shown in the past the ability of modifying and enhancing light response of nanoscale objects. The realization of this hybrid system opens a way to novel applications and the use optical fields to manipulate and enhance the light interaction with semiconducting materials[3,4].
We demonstrate for the first time how, by hybridizing a single nanowire photo#8208;detector with a bow#8208;tie antenna structure, it is possible to control the polarization response of a nanowire. Bow#8208; tie antenna concentrate radiation inside the body of the nanowire, thereby increasing the absorption of light polarized across the nanowire axis. The amount of light absorbed is strictly dependent on the antenna design and density. We demonstrate enhancement in light absorption, as well as for second order phenomena such as the generation of second harmonics and Raman scattering . We perform photoconductivity measurements demonstrating that a hybrid structure formed by GaAs NWs and an array of bow-tie antennas is able to modify the polarization response of a NW. The large increase in light absorption for transverse polarized light changes the NW polarization response, including the inversion.
This study constitutes an important step for the understanding of light coupling in engineered nanodevices. It opens a path to applications aiming to combine the semiconducting properties of nanostructures with the plasmonic properties of metal. Hybrid nanoantenna-NW systems can certainly bring progress to the use of nanowires for next generation photo#8208;detectors and solar cells.
P. Krogstrup, et al., Nature Photonics, vol 7, 306-310 (2013)
C. Forestiere, et al., Nano Letters, vol 12, 2037-2044 (2012)
A. Casadei, et al., Nano Letters, vol 14, 2271-2278 (2014)
S. Heeg, et al., Nano Letters, vol 14, 1762-1768 (2014)
A. Casadei, et al, Scientific Report, (under review)
Z1: Hot Topics in Nanophotonics
Tuesday AM, April 07, 2015
Moscone West, Level 2, Room 2004
9:00 AM - *Z1.01
Plasmonics: From Quantum Effects to Light Harvesting
Peter Nordlander 1
1Rice University Houston United StatesShow Abstract
The “plasmon hybridization”concept, shows that the plasmon resonances in complex metallic nanostructures interact and hybridize in an analogous manner as atomic wavefunctions in molecules. The insight gained from this concept provides an important conceptual foundation for the development of new plasmonic structures that can serve as substrates for surface enhanced spectroscopies, chemical and biosensing, and subwavelength plasmonic waveguiding and other applications. The talk is comprised of basic overview material interspersed with a few more specialized “hot topics” such quantum plasmonics, molecular plasmonics, active plasmonic nanoantennas for enhanced light harvesting, plasmon induced hot carrier generation, and chemical reactions.
 N.J. Halas et al., Adv. Mat. 24(2012)4842
 T.V. Teperik et al., PRL 110(2013)263901; Opt. Express 21(2013)27306
 A. Manjavacas et al., ACS Nano 7(2013)3635
 M. W. Knight et al., NL 13(2013)1687; A. Sobhani et al., Nature Comm. 4(2013)1643
 A. Manjavacas et al., ACS Nano 8(2014)7630
 S. Mukherjee et al., JACS 136(2014)64; Y. Kang et al., Adv. Mat. 26(2014)6467
Z5: Poster Session I
Tuesday PM, April 07, 2015
Marriott Marquis, Yerba Buena Level, Salon 7/8/9
9:00 AM - Z5.01
Capillary Force-Driven, Large-Area Assembly of Anisotropic Nanoparticles
Yu Zhou 1 Xiaozhu Zhou 2 Chad A. Mirkin 1
1Northwestern University Evanston United States2Henkel Corporation Madison Heights United StatesShow Abstract
We report the large-area assembly of gold anisotropic nanoparticles into lithographically defined templates with control over their angular position using a capillary-based approach. We elucidate the role of the geometry of the templates in the assembly of anisotropic nanoparticles consisting of different shapes and sizes. These insights allow us to design templates that immobilize individual triangular nanoprisms and concave nanocubes in a shape-selective manner, and filter undesired impurity particles from a mixture of triangular prisms and other polyhedra. Furthermore, by studying the assembly of two particles in the same trench, we elucidate the importance of interparticle forces with this novel method. These advances allow for the construction of face-to-face and edge-to-edge nanocube dimers as well as triangular nanoprism bowties. As an example of the fundamental studies enabled by this assembly method, we investigate the surface enhanced Raman scattering (SERS) of face-to-face concave cube dimers both experimentally and theoretically, and reveal a strong polarization dependence of the local field enhancement.
9:00 AM - Z5.03
Silver Nanocube Aggregation Gradient Materials in Search for Total Internal Reflection with High Phase Sensitivity
Tobias AF Koenig 1 3 Petr A Ledin 3 Michael Russell 3 Jeffrey Geldmeier 3 Mahmoud A Mahmoud 2 Mostafa A. El-Sayed 2 Vladimir Tsukruk 3
1University of Bayreuth Bayreuth Germany2Georgia Institute of Technology Atlanta United States3Georgia Institute of Technology Atlanta United StatesShow Abstract
We fabricated coatings with a silver nanocube aggregation gradient by applying different surface pressures during slow Langmuir-Blodgett deposition. The randomly distributed nanocube aggregates with gradually changing surface coverage open up new ways to continuously control the absorption and phase of the incoming light over a broad optical spectrum, while being polarization sensitive. Optical characterization under total internal reflection conditions (TIR) reveals that the broadband light absorption depends on the relative orientation of the particle aggregations to the polarization of the incoming light, which has not been investigated yet. By using electromagnetic simulations, we found that the electric field vector of the s-polarized light matches with the different types of silver nanocube aggregations to excite variable plasmonic resonances. Based on this matching conditions, the s-polarization shows an outstanding tunablility of the plasmonic resonance by the angle of incidence (64nm per 10° angle of incidence). Further observation of these modes with spectral ellipsometry reveals a steep phase change at the plasmonic resonances. With a very low surface coverage below 25%, we observed a polarization-selective absorption of 80% (theoretical 98% at peak value) of the incoming light over a broad optical range in the visible region from 400 to 700 nm. This low cost, large area, gradiental variable and easily scalable assembled plasmonic material designs is of particular interest for broadband light absorption, phase-sensitive sensors, and imaging.
9:00 AM - Z5.04
Colloidal Metasurfaces Displaying Near-Ideal and Tunable Light Absorption in the Visible and Infrared
Matthew Rozin 1 Andrea R Tao 1
1University of California San Diego La Jolla United StatesShow Abstract
Optical metasurfaces are ultrathin, two-dimensional arrays of subwavelength resonators that have been demonstrated to control the flow of light in ways that are otherwise unattainable with natural materials. However, metasurfaces pose major challenges in their nanofabrication, prominently in terms of minimum reliable feature size, high throughput and large area fabrication, which can be prohibitively expensive and time-consuming using conventional lithography techniques. Optical metasurfaces that operate in the visible are inherently challenging to fabricate due to their multi-scale architecture, and requirement for deeply sub-wavelength features, often requiring dielectric spacing of a few nanometers.
Self-assembly provides an alternative fabrication approach that overcomes these limitations in scalability and design. Here we show that colloidal, single-crystalline anisotropic nanocrystals can be organized into metasurface architectures with nanometer-precision using robust, scalable assembly methods. These metasurfaces exhibit extreme in- and out-of-plane electromagnetic coupling that is strongly dependent on nanocrystal size, shape, and spacing. We show that this fabrication approach enables plasmonic metamaterials to be tuned for diverse applications ranging from metasurfaces that display near-ideal electromagnetic absorption--up to 99.8%--tunable from the visible into mid- IR wavelengths, to quasi-2D metasurfaces that demonstrate photoluminescent enhancement of over 120x, for an active region less than 150 nm thick.
9:00 AM - Z5.05
Superplastic Flow of Multi-Crystalline Plasmonic Gold Nanoantenna under Laser Induced Shock Wave
Yaowu Hu 1 Shengyu Jin 1 Biwei Deng 1 Gary Cheng 1
1Purdue University West Lafayette United StatesShow Abstract
Laser induced mechanical shockwave was developed as an effective tool to tailor multi-crystalline Au nanostructures and tune nanogaps in plasmonic nanoantennas. The shock wave generation during laser shock irradiation of graphite was explained using Fabbro's model. Atomic movement of plasmonic gold structure under shockwave compression was investigated using molecular dynamic simulations. Force - displacement relationship was monitored to analyze mechanical property change of nanostructures during laser shock compression. Atoms were found to move in radial direction and nanodisks were found to keep their symmetry after severe plastic deformation. Geometrical changes at different laser energies were quantitatively measured using SEM and AFM images. Surface roughness was found to be decreased after laser shock compression. Different nanogaps down to sub-10 nm could be effectively controlled by varying laser fluences. Optical response of the processed nanostructures were compared with initial structures by numerical simulations and experiments. It was found that after laser shock, nanodisks were enlarged, brought closer, and field enhancement at the center of two adjunct nanodisks was hugely increased. The processed nanostructures had higher sensitivity in low- concentration molecular sensing experiment. Optical dark field spectroscopy experiment showed that the resonance of these processed structures had a red shift compared to the initial structures. Laser induced mechanical shockwave is an effective tool to improve optical properties of multi-crystalline plasmonic nanoantennas.
9:00 AM - Z5.06
Direct Observation of Anisotropic Electrostatic Potential in Gold Nanorod Using Electron Holography
Ji-Young Kim 2 Nicholas A. Kotov 1 2 3 Myung-Geun Han 4
1Univ of Michigan Ann Arbor United States2University of Michigan Ann Arbor United States3University of Michigan Ann Arbor United States4Brookhaven National Lab Upton United StatesShow Abstract
The origin of unique optical properties of gold nanorods such as distinctive extinction bands in the upper visible or near-infrared region is surface plasmon (SP) oscillation of free electrons. Surface electrostatics of gold nanorod is tremendously important to understand how electrons interact with optical waves. Electrostatic property of gold nanorods has been known to be centrosymetric, however, we have shown that gold nanorods have anisotropic charge accumulation on their surface, which can be defined as a polarized surface charge density. By using off-axis electron holography, we have observed anisotropic electrostatic potential of gold nanorods experimentally. We believe that their anisotropic potential is from different distribution of cetyltrimethylammonium bromide (CTAB), capping ligand having positive charge, on the gold nanorod surface. This anisotropic distribution of CTAB is identified by high resolution scanning electron microscopy (SEM), implementing secondary electron detector in high resolution transmission electron microscopy (TEM) system. We believe that this anisotropic potential formed by CTAB layer results in anisotropic charge accumulation on the gold surface as compensate the potential gradient. As the result, the inner potential of gold nanorod itself has no gradient as well known the fact that the electric field anywhere beneath the surface of a charged conductor is zero. Computation of electrostatic potential of gold nanorod considering this charge distribution from CTAB is well matched with experimental hologram that we observed.
9:00 AM - Z5.07
Core-Shell Hybrid Nanostructure of Metal (Core) and Polymer (Shell) toward High Performance Optical Sensor
Seokho Kim 1 Sujin Kim 1 Dong Hyuk Park 1 Gilsun Lee 2
1Dept. Applied Organic Materials Engineering, INHA University Incheon Korea (the Republic of)2Department of General Educations, Kookmin University Seoul Korea (the Republic of)Show Abstract
As our society become progress, the possibility of people to be exposing to various hazardous environments. The needs to develop high sensitive and selective bio/chemical sensor have been increased. The π-conjugate polymers are a good candidate for the developing sensor applications because of their specific detection capability through a large change in the electrical and optical signals. In this study, we present a high performance optical sensing using core-shell hybrid nanostructure consist of silver (Ag) nanoparticles (NPs) and polydiacetylene (PDA). Our ultimate aims are improvement and control in the detection ability of selectivity and sensitivity by means of surface plasmon resonance (SPR) coupling effect. We fabricate a core-shell NP in deionized (DI) water solution through sequentially processes of reprecipitation and hydrothermal thermal method. The formation of the Ag/PDA core-shell hybrid NPs was visualized through scanning electron microscope (SEM) and high resolution-transmission electron microscope (HR-TEM) images. The nanometer-scale photoluminescence (PL) and Raman characteristics of core-shell NP were studied by using a laser confocal microscope (LCM) with a help of color charged-coupled device (CCD) images. The variation of light emission color and intensities of the core-shell hybrid nanostructure were observed depending on the amounts and kinds of target materials. Our results show that the PL intensity of Ag/PDA core-shell hybrid NP considerably increased compare to pristine PDA materials when the attachment of target bio/chemical materials because of the strong SPR coupling effect.
9:00 AM - Z5.08
Multiple Coupling in Plasmonic Metal/Dielectric Hollow Nanocavity Arrays for High Sensitive Detection
Jun Yin 1 Yashu Zang 1 Chuang Yue 1 Xu He 1 Jing Li 1 2
1Xiamen University Xiamen China2University of Califonia, Berkeley Berkely United StatesShow Abstract
Recently, plasmonic coupled optical cavity has gained much attention due to its attractive properties in light manipulation, e.g. high Q optical resonance, local field enhancements[2,3] and extraordinary transmission. The strongly enhanced local filed originated from the plasmonic resonance hybridizing with the optical cavity mode has great potential applications. Therefore, it has been widely proposed to be used in enhancing semiconductor emission, plasmonic laser, WGM resonator based bio-sensor, SERS detecting and other related fields requiring superior optical performances.
In this work, the coupling effect between plasmonic mode and optical cavity mode has been demonstrated in self-assembled metal/dielectric hollow-nanosphere (HNS) arrays. The further employment of the strongly enhanced local filed originated from the inter-coupling of the plasmonic cavities for high sensitive SERS sensing was proposed. Large scale, two-dimensional (2D) metal/dielectric HNS arrays were successfully fabricated using the self-assembled polystyrene (PS) nanospheres as the template. Series orders of whispering gallery mode (WGM) resonances in the HNSs and plasmonic coupled WGM resonances in the double-shell HNSs have been experimentally and theoretically demonstrated by the transmission spectroscopy and simulated resonance spectra and near field patterns in FDTD method. Highly localized near field around the HNS cavities originated from the plasmonic WGM resonance and its strong multiple coupling effect between the HNS arrays ensure this plasmonic cavity arrays to be a suitable SERS substrate. Extraordinary SERS performances were then achieved on the HNS arrays with optimized size and gaps. Additionally, more significant photocatalytic self-cleaning process can be effectively accomplished on this recyclable SERS chips under visible light irradiation rather than conventional UV illumination.
9:00 AM - Z5.09
Spectroelectrochemistry of Silver Deposition on Single Gold Nanocrystals
Mariana Chirea 1 Sean Stevenson Edward Collins 2 Xingzhan Wei 2 Paul Mulvaney 2
1Universidade do Porto Porto Portugal2University of Melbourne Melbourne AustraliaShow Abstract
The study of catalytic processes and redox reactions on metal nanocrystal surfaces is extremely challenging. Rates of reaction are highly sensitive to a variety of parameters including the particle size and shape, the degree of crystal faceting, the occurrence of underpotential deposition (UPD) and the role of substrate interactions. These factors are all convoluted in ensemble electrochemical measurements and consequently, one approach for obviating these problems is to study redox processes on single metal nanoparticles. We report the electrodeposition of metallic silver onto single gold nanostars adsorbed to indium tin oxide (ITO) electrodes. The electrochemical process was studied in-situ by correlated dark field spectroscopy and scanning electron microscopy (SEM). We demonstrate that bulk nucleation and growth on the ITO can be circumvented by careful application of chronoamperometry enabling controlled, selective growth of small amounts of silver onto single gold nanocrystals. This is possible because the binding energy for silver to gold is large enough to enable selective deposition at very low overpotentials. In order to increase the probability of UPD and hence control the deposition process, we have used gold nanostars which present a wide range of crystal facets and possess a high double-layer capacitance, due to their high surface-to-volume ratios. We carry out chronoamperometry at very low silver ion concentrations (0.5 micromolar) in 0.1 M NaNO3 as the supporting electrolyte. SEM proves that deposition occurs preferentially on less atomically coordinated gold sites at the tips. The surface plasmon resonance blue-shifts by several tens of nanometers following the formation of spherical deposits of silver on the star tips, moving the scattered colour from the near infrared to red. The spectral shifts can be accurately modelled using finite element simulations. These results demonstrate that the morphological properties of individual bimetallic particles can be engineered electrochemically by monitoring optical changes.
9:00 AM - Z5.10
Chiroptical Properties of Silver Nano-Spirals
Fan Bai 1
1Hong Kong Baptist University Hong Kong Hong KongShow Abstract
Chiral structures are ubiquitous in nature, such as DNA, peptides and amino acids, which exhibit very small chiroptical effects. However, chiral nanoplasmonic structures exhibit strong chiroptical effects, which are not only due to the chiral geometry of nanoparticles, but also to nanoplasma used to manipulate the local electric and magnetic fields. In our study, silver nano-spirals (AgNSs) with adjustable geometric parameters have been fabricated in wafer scale by glancing angle deposition (GLAD) under controlled low temperature. When AgNSs are dispersed in ethanol, it has been demonstrated that circular dichroism of individual AgNSs can be tuned by adjusting a set of spiral dimensional parameters. In addition, a gigantic