Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session H18: Plasmons and Polaritons in Superlattices, Nanaostructures, and other Artificially Structured Materials |
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Sponsoring Units: DCMP DMP Chair: Sayantani Ghosh, Univ of California - Merced Room: LACC 306B |
Tuesday, March 6, 2018 2:30PM - 2:42PM |
H18.00001: Plasmon-Assisted Förster Resonance Energy Transfer in Hybrid Organic/Inorganic Nanomaterials. Thang Hoang Förster resonance energy transfer is a physical mechanism that describes the energy transfer between two light-sensitive objects through nonradiative dipole-dipole interactions at small length scales. Here, we investigate the Förster resonance energy transfer between organic molecules and adjacent semiconductor quantum dots with the influence of a plasmon field. The plasmon field, generated by a plasmonic nanocavity through engineering the coupling between metallic nanoparticles and a metal surface, significantly enhances the energy transfer rate between organic and inorganic materials. Organic materials provide an excellent opportunity to efficiently absorb photons in the near infrared or ultraviolet frequencies, and the semiconductor quantum dots are excellent candidates for optoelectronic and nanophotonic device applications in the visible frequency. Plasmonic nanocavities thus bridge the energy gaps between organic and inorganic nanomaterials. We discuss ways to control the light-matter interactions at the nanoscale and subsequently elucidate the interactions between organic and inorganic emitters and optimally designed plasmonic nanoplatforms, gearing towards highly efficient light harvesting devices. |
Tuesday, March 6, 2018 2:42PM - 2:54PM |
H18.00002: Plasmon-Enhanced Energy Transfer in Photosensitive Nanocrystal Device Pedro Hernández-Martínez, Shahab Akhavan, Mehmet Zafer Akgul, Hilmi Demir In this work, we fabricated and comparatively studied seven types of NC (Nanocrystal)-monolayer devices consisting of only donor, only acceptor, Au (gold) MNP (Metal Nanoparticle)-donor, Au MNP-acceptor, donor-acceptor bilayer, donor-Au MNP-acceptor trilayer, and acceptor-Au MNP-donor reverse trilayer. We experimentally and theoretically studied the effect of LSP (Localized Surface Plasmon)-enhanced FRET (Förster-type Resonance Energy Transfer) and exciton interactions from the donor NCs layer to the acceptor NCs layer. The obtained numerical results are in excellent agreement with the systematic experimental studies done in our work. Moreover, we experimentally show that LSP-enhanced FRET in these NC photosensors result in a substantially enhanced photosensitivity. For instance, compared to a single acceptor NC device, we observed a significant extension in operating wavelength range and a substantial photosensitivity enhancement (2.91-fold) around the LSP resonance peak of Au MNPs in the LSP-enhanced FRET trilayer structure. |
Tuesday, March 6, 2018 2:54PM - 3:06PM |
H18.00003: Ultra-Fast Light Energy Transfer with Suppressed Losses Through Hot-Spots in Heterogeneous Plasmonic Arrays Lucas Vazquez Besteiro, Eva Roller, Larousse Khosravi Khorashad, Tim Liedl, Alexander Govorov Plasmonic materials effectively confine light beyond the diffraction limit, being a useful tool in Nanophotonics for a diverse range of applications, from sensing to energy harvesting. They have proven difficult to use, however, as a means for energy transportation: Although a nanostructured metallic guide, be it as a surface supporting SPPs or as an array of nanoparticles in near-field interaction, has the capability of constraining the spatial evolution of an electromagnetic excitation, the high losses characteristic to metals make this a problematic approach to energy transfer. To partially circumvent this limitation, we propose the use of heterogeneous arrays of plasmonic nanoparticles, using different metals with resonances that are not spectrally aligned. We propose a system that exemplified this approach, built using gold and silver nanoparticles, precisely aligned using DNA origami technique [1]. We show computationally that a silver particle in a trimer suppresses energy transfer losses, and report observation of features of such loss-less transfer [1]. Similar complexes could be useful as connection and control elements in hybrid or all-optical computing devices. |
Tuesday, March 6, 2018 3:06PM - 3:18PM |
H18.00004: Femtosecond All-Optical Control of Plasmons: Hot-Electron versus Phonon Relaxation Mohammad Taghinejad, Hossein Taghinejad, Sean Rodrigoues, Wenshan Cai The optical Kerr nonlinearity of plasmonic metals provides enticing prospects for developing reconfigurable and ultracompact all-optical modulators. In nanostructured metals, the coherent coupling of electromagnetic radiations to plasmons creates a nonequilibrium distribution of electrons at an elevated temperature that gives rise to significant Kerr optical nonlinearities. Although enhanced nonlinear responses of metals enable the optical control of light, the intrinsically slow relaxation dynamics of photoexcited carriers, primarily governed by electron-phonon interactions, impedes sub-picosecond modulation speeds. Here, we demonstrate femtosecond (~ 190 fs) all-optical modulation in plasmonic systems via the activation of relaxation pathways for hot-electrons at the interface of metals and electron acceptor materials. We show that the relaxation kinetics and the optical nonlinearity can be tuned by leveraging the spectral response of the plasmonic system in the linear regime. Our findings introduce a generic scheme for achieving sub-picosecond modulation speeds in plasmonic systems, suitable for the ultrafast control of the intensity, polarization, and phase of light upon exchange of energetic hot carriers. |
Tuesday, March 6, 2018 3:18PM - 3:30PM |
H18.00005: Hot-electron generation in plasmonic nanostructures with hot spots: Quantum mechanisms Alexander Govorov, Lucas Vazquez Besteiro, Xiang-Tian Kong, Zhiming Wang, Gary Wiederrecht Generation of energetic (hot) electrons is an intrinsic property of any plasmonic nanostructure under illumination. Simultaneously, a striking advantage of metal nanocrystals over semiconductors lies in their very large absorption cross sections. Therefore, metal nanostructures with strong and tailored plasmonic resonances are very attractive for photocatalytic applications in which excited electrons play an important role. However, the central question in this problem is to quantify the number of hot electrons in a nanocrystal. Here we develop a theory describing the energy distributions of hot electrons in nanocrystals with various geometries [1-4]. In particular, we show that nanostructures with strong plasmonic hot spots generate unusually large numbers of hot electrons, which can be observed using ultra-fast spectroscopy, [2,4] and photochemistry. |
Tuesday, March 6, 2018 3:30PM - 3:42PM |
H18.00006: Encapsulated low-energy graphene plasmons under strain and the effect of
plasmon-phonon coupling Dipendra Dahal, Godfrey Gumbs The combined effect due to strain, encapsulation and phonon scattering on the plasmon excitation |
Tuesday, March 6, 2018 3:42PM - 3:54PM |
H18.00007: Plasmonic Based Microcapsules as Strain Sensors Celine Burel, Remi Dreyfus, Bertrand Donnio, Ahmed Alsayed, ludivine Malassis Plasmonic nanoparticles (NPs) assembled into two- or three-dimensional architectures offer new collective optical properties. Indeed, closely packed gold nanoparticles (Au NPs) absorb light at higher wavelength than when they are far apart. Au NPs were assembled onto droplets to fabricate new dispersed materials. By tuning the charges and wettability of Au NPs, they adsorb and pack at the surface of emulsion droplets. A subsequent silanization at the interface of the emulsion allows to lock the NPs inside a silica shell. Au NP-silica microcapsules are obtained by that process. The Au NP-silica microcapsules were inserted in a polymeric film. When the films are stretched, the microcapsules are deformed into elongated ellipsoidal shapes and the distance between the Au NPs embedded in their shells concomitantly increases. As the extinction of Au NPs depends on the separation between the Au NPs, the microcapsules exhibit different colors when they are deformed. These novel microcapsules can be used to detect and measure mechanical deformations by outputting a color change. Each one of the microcapsules being one sensor by itself, these results pave the way as for the design of new microscale sensors. |
Tuesday, March 6, 2018 3:54PM - 4:06PM |
H18.00008: Detecting Photothermoelectric Voltages from Surface Plasmon Polariton Excitation in Gold Nanoscale Devices Charlotte Evans, Xifan Wang, Pavlo Zolotavin, Douglas Natelson Thermoelectric properties of nanostructured materials heated under laser illumination can be detected via measurable open-circuit voltages, which can be useful for applications such as photodetection. Large open-circuit photovoltages have been detected in single metal, plasmonically-active structures with nanogaps when the gap is directly illuminated with resonant light, consistent with “hot” carrier generation from plasmon excitation. This effect is particularly evident in thin gold “bowtie” devices because of the strong local plasmon resonance in the nanowire constriction. Direct optical excitation of the nanogap can cause high local heating which can cause nanogap morphology instability. To reduce this temperature rise, metallic gratings are added to the electrode design which can be illuminated to excite propagating plasmons that couple into the junction region without direct excitation by far-field radiation. We will present how the open-circuit voltage of these devices with and without nanogaps varies as a function of incident laser position and discuss how the results of remote excitation of the nanogap via propagating plasmons compare to direct excitation, in the context of "hot" carriers. |
Tuesday, March 6, 2018 4:06PM - 4:18PM |
H18.00009: Quantum description of the optical response of charged monolayer–thick metallic patch nanoantennas Mario Zapata Herrera, andrey Kazansky, Javier Aizpurua, Andrei Borisov The optical response of small charged metallic nanodisks of one atomic monolayer thickness is analyzed under the excitation by an incident plane wave and by a localized point-like dipole. Using the time-dependent density functional theory (TDDFT) and classical electrodynamical calculations we identify the bright and dark plasmon modes and study their evolution under external charging of the nanostructure. For neutral nanodisks, despite their monolayer thickness, the in-plane optical response, as obtained from TDDFT, is in agreement with classical electromagnetic results. The optical response for an incident wave polarized perpendicular to the nanostructure cannot be retrieved classically as it reflects a discrete energy structure of electronic levels. This latter situation appears most sensitive to external charging while the energy of the in-plane plasmon with dipolar character is nearly charge independent. |
Tuesday, March 6, 2018 4:18PM - 4:30PM |
H18.00010: Bounds on quantum confinement effects in metal nanoparticles Gordon Blackman, Dentcho Genov Quantum size effects on the permittivity of metal nanoparticles are investigated using the quantum box model. Explicit upper and lower bounds are derived for the permittivity and relaxation rates due to quantum confinement effects. These bounds are verified numerically, and the size-dependence and frequency-dependence of the empirical Drude size parameter is extracted from the model. Results suggest that the common practice of empirically modifying the dielectric function can lead to inaccurate predictions for highly uniform distributions of finite-sized particles. |
Tuesday, March 6, 2018 4:30PM - 4:42PM |
H18.00011: Direct observation of plasmon-induced interfacial charge separation in metal/semiconductor hybrid nanostructures by measuring surface potentials Jae-Won Jang Plasmon-induced interfacial charge separation (PICS) is one of the key processes responsible for the improved conversion efficiencies of energy-harvesting devices that incorporate metal nanostructures. In this letter, we reveal a mechanism of PICS by visualizing (with nanometer-scale resolution) and characterizing plasmon-exciton coupling between p-type poly(pyrrole) (PPy) nanowires (NWs) and Ag nanoparticles (NPs) using light-irradiated Kelvin probe force microscopy (KPFM). Under blue-light irradiation, the Ag NPs are expected to donate electrons to the PPy NWs via a hot electron injection process. However in this letter, we observe that under blue-light irradiation the plasmonically and excitonically excited electrons in the semiconductor back-transfer to the metal. These experimental findings and our proposed mechanism consistently explain the PICS occurring in the PPy NW-Ag NP system with important implications on explaining their cooperative optoelectronic activities. |
Tuesday, March 6, 2018 4:42PM - 4:54PM |
H18.00012: Giant THz surface plasmon polariton induced by high-index dielectric metasurface Shuai Lin, Khagendra Bhattarai, Jiangfeng Zhou, Diyar Talbayev We use computational approaches to explore the role of a high-refractive-index dielectric TiO2 grating with deep subwavelength thickness on InSb as a tunable coupler for THz surface plasmons. We find a series of resonances as the grating couples a normally-incident THz wave to standing surface plasmon waves on both thin and thick InSb layers. In a marked contrast with previously-explored metallic gratings, we observe the emergence of a much stronger additional resonance. The mechanism of this giant plasmonic resonance is well interpreted by the dispersion of surface plasmon excited in the air\TiO2\InSb trilayer system. We demonstrate that both the frequency and the intensity of the giant resonance can be tuned by varying dielectric grating parameters, providing more flexible tunability than metallic gratings. The phase and amplitude of the normally-incident THz wave are spatially modulated by the dielectric grating to optimize the surface plasmon excitation. The giant surface plasmon resonance gives rise to strong enhancement of the electric field above the grating structure, which can be useful in sensing and spectroscopy applications. |
Tuesday, March 6, 2018 4:54PM - 5:06PM |
H18.00013: Metasurfaces with Dual-Band, Spatially Overlapped Resonances in the Visible and Near-Infrared Andrew Boyce, Qixin Shen, Guoce Yang, Maiken Mikkelsen Metasurfaces are arrays of subwavelength resonators that demonstrate optical properties that are unobtainable naturally, such as near-perfect absorption of incident light on resonance. In the visible and near-infrared, near-perfect absorption has been previously demonstrated in a number of systems, including nanopatch antennas (NPAs), which are composed of colloidally-synthesized silver nanocubes separated from a metallic film by a polymer spacer layer. However, using colloidal nanocubes results in a random distribution of nanoparticles and does not allow for the creation of two absorption resonances that can be tuned independently. Highly-ordered samples with independently-tunable absorption resonances can be produced by instead using nanolithography techniques. In this work, patterned NPA arrays have been fabricated using electron beam lithography. Arrays of both nanocubes and nanodisks demonstrate strong, tailorable absorption. The resonance bandwidth decreases with increasing particle spacing, allowing for fabrication of absorbing metasurfaces with on-demand bandwidth. Furthermore, nanorectangles have shown double absorption resonances. Two spatially overlapped modes can be accessed via the incident polarization may find application in dual enhancement of optical processes. |
Tuesday, March 6, 2018 5:06PM - 5:18PM |
H18.00014: Lasing by ensemble of spasers Lyudvig Petrosyan, Tigran Shahbazyan We study laser action of two or more nanoparticle-based spasers in mutual electromagnetic field. We show that radiative coupling between spasers at subwavelength distance leads to spasers’ synchronization and lowers the system laser threshold relative to that of individual spasers. For spherical composite nanoparticles with metal core and dye-doped dielectric shell, we develop analytical model describing cooperative stimulated emission by a pair of closely-separated spasers. |
Tuesday, March 6, 2018 5:18PM - 5:30PM |
H18.00015: Hybrid polariton bands and its polarization dependence in an organic-dye-doped nanostructure Ruwen Peng, Kun Zhang, Renhao Fan, Yue Xu, Chengyao Li, Wen-BO Shi, Mu Wang In this work, we demonstrate polarization-dependent strong coupling between surface plasmon polaritons(SPPs) and excitons in the J-aggregates attached plasmonic aperture array. It is shown that the excitons strongly couple with the polarization-dependent SPPs, and Rabi splittings are consequently observed. As a result, the polarization-dependent polariton bands are generated in the system. Increasing the incident angle, the polaritons disperse to higher energies under transverse-electric (TE) illumination; while the polaritons disperse to lower energies under transverse-magnetic (TM) illumination. Therefore, at different polarization incidence, we experimentally achieve distinct polaritons with opposite dispersion directions. Furthermore, we find that the dispersion properties of the polaritons inherit from both the SPPs and the excitons. Besides, we also experimentally present the hybrid coupling among molecular excitons, SPPs, and Fabry-Perot (FP) mode in a nanostructured cavity, where a J-aggregates doped PVA (polyvinyl alcohol) layer is inserted between a silver grating and a thick silver film. Our investigation may inspire related studies on tunable photon-exciton interactions and achieve some potential applications on active polariton devices. |
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