Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session Z50: Plasmonics and Metamaterials |
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Sponsoring Units: DCMP Chair: Christos Argyropoulos, Duke University Room: Mile High Ballroom 1D |
Friday, March 7, 2014 11:15AM - 11:27AM |
Z50.00001: Germanium-Based Plasmonic Nanojunctions Kenneth Evans, Pavlo Zolotavin, Douglas Natelson The fabrication of robust optoelectronic devices which function on length scales well below the wavelength of light is an important step in the development of light-based electronics. We present a method for the production of reliable near-IR light detection in germanium films on plasmonically-active gold nanojunctions. We show polarization measurements consistent with the existence of plasmon-enhanced absorption in these structures, making possible the careful study of the effect of highly local plasmons in the gold leads on the photogenerated carriers in the germanium. We discuss the photoconductive mechanism in these structures and the potential for high-efficiency, scalable photodevices through changes to the device geometry. [Preview Abstract] |
Friday, March 7, 2014 11:27AM - 11:39AM |
Z50.00002: Dirac-Like Plasmons in Honeycomb Lattice of Metallic Nanoparticles Claire Woollacott, Guillaume Weick, William L. Barnes, Ortwin Hess, Eros Mariani We consider a two-dimensional (2D) honeycomb array of metallic nanoparticles, each supporting a localized surface plasmon, and study the quantum properties of the collective plasmonic modes resulting from the near-field dipole interaction between nanoparticles. We analytically investigate the dispersion, effective Hamiltonian and eigenstates of the collective plasmons for an arbitrary orientation of the individual dipole moments. For polarization pointing normal to the plane, the spectrum presents Dirac cones similar to those present in the electronic band structure of graphene. The effective Dirac Hamiltonian and corresponding spinor eigenstates represent Dirac-like massless bosonic excitation, presenting similar effects to electrons in graphene, for example, non-trivial Berry phase and the absence of backscattering off smooth inhomogeneities. However, by tilting the polarisation, the Dirac points can be manipulated and a gap can be controllably opened in the spectrum. Therefore the properties of this metamaterial can be manipulated by the incident light polarization, paving the way for a fully tunable plasmonic analogue of graphene. - G. Weick, C. Woollacott, W. Barnes, O. Hess and E. Mariani, Phys. Rev. Lett. 110, 106801 (2013) [Preview Abstract] |
Friday, March 7, 2014 11:39AM - 11:51AM |
Z50.00003: Tailoring the plasmonic modes of metal nanoparticle arrays with lattice anisotropy King Chun Lai, Sze Fung Lee, Kin Wah Yu We have studied the plasmonic band structure of three-dimensional lattices of nanoparticles under external electromagnetic waves. The long-range dipolar forces among polarized nanoparticles lead to the collective motion of the dipole moments to form plasmon. The resulting plasmonic dispersion thus depends on the polarizability of individual particle and the lattice structure of the whole system. We tailor sets of desirable plasmonic modes through varying the polarizability of nanoparticles or lattice anisotropy which can be tuned by incident GHz ultrasonic waves. Similar work of one-dimensional particle chain was contributed by Maier (2003), but we further extend the system into three-dimensional cases. In order to deal with the long-range interactions, we adopt the Ewald method to develop a viable means for calculating the plasmonic dispersion relation. Furthermore, we consider the formalism for diatomic basis of nanoshell. The plasmonic modes of each particle may couple and form hybridized plasmonic band attributed to level repulsion effect. This method provides a flexible way to manipulate plasmonic wave in a lattice by tuning the characteristic parameters of particle shape or lattice structure. [Preview Abstract] |
Friday, March 7, 2014 11:51AM - 12:03PM |
Z50.00004: Selective reflection by deteriorated phase accumulation in Fabry-Perot cavity with aperiodic metallic nanomesh entry windows Tianyi Sun, Chuanfei Guo, Krzysztof Kempa, Zhifeng Ren A Fabry-Perot reflection filter, consisting of semi-transparent metal and dielectric layers on opaque metals, is featured by selective absorption determined by the phase difference of waves from the two interfaces. In such systems, semi-transparency is usually realized by layers of reflective metals thinner than the penetration depth of the light. Here we present a filter cavity with entry windows not made of traditional thin layers, but of aperiodic metallic random nanomeshes thicker than the penetration depth, fabricated by grain boundary lithography. It is shown that due to the deteriorated phase caused by the interface between the random nanomesh and the dielectric layer, the width and location of the resonances can be tuned by metallic coverage. Further experiments show that this phenomenon can be used in designing aperiodic plasmonic metamaterial structures for visible and infrared applications. [Preview Abstract] |
Friday, March 7, 2014 12:03PM - 12:15PM |
Z50.00005: Symmetry-broken metamaterial absorbers as reflectionless directional couplers for surface plasmon polaritons in the visible range Fan Ye, Michael J. Burns, Michael J. Naughton Recently, gradient-index meta-surfaces have been shown to have the ability to manipulate wavefronts at will in a reflectionless manner in the GHz range, including the extreme example of converting freely propagating waves into surface waves with high-efficiency. Upon approaching the visible regime, the gradient-index concept encounters difficulties due to fabrication limitations. Here, we demonstrate theoretically and experimentally that asymmetric, periodic, two-element metal-insulator-metal structures can serve as reflectionless directional convertors between freely propagating visible photons and surface plasmon polaritons (SPP). Coupling between propagating modes caused by the broken symmetry and localized modes generated by individual elements is shown to be the main mechanism of this high-efficiency process. Direct experimental evidence is obtained for reflectionless ($<$ 8\% measured reflectance) directional SPP coupling in the visible range, with a directionality of 99.7\%. A novel measurement scheme is developed for the characterization of absolute reflectance of samples with micron-sized area under normal incidence in the visible range. Our results are meaningful for integrated nanoplasmonics, plasmonic logic, and plasmonic light harvesting, among others. [Preview Abstract] |
Friday, March 7, 2014 12:15PM - 12:27PM |
Z50.00006: Edge state and photon emission rate in plasmon chains Chi Wai Ling, Kin Hung Fung, Siu Fung Yu Topology band theory has explained many important electronic phenomena in condensed matter physics, like quantum hall effect and topological insulators. We consider realistic plasmonic nanoparticles as strongly coupled ``atoms'' and study the topological properties in the plasmon bands. Zak phase and edge state frequency in chains of plasmonic nanoparticles are studied analytically. Photon emission rate enhanced by such an edge state is also analyzed by solving the Maxwell's equations using FDTD method. [Preview Abstract] |
Friday, March 7, 2014 12:27PM - 12:39PM |
Z50.00007: Electromagnetic properties of gain-doped epsilon-near-zero metamaterials Ka Ki Ng, Naijing Deng, Kin Wah Yu Sun and Yu designed broadband gain-doped epsilon-near-zero (GENZ) metamaterials in 2012. The large loss of epsilon-near-zero metamaterials is compensated by gain to get a great advantage in practical applications. Previous works have demonstrated that the electromagnetic properties of gain media differ from that of lossy media. For example, the original Kramers-Kronig relations are no longer suitable for certain gain media. Therefore, we have studied the electromagnetic properties of GENZ and determined whether it is possible to develop such relations for GENZ over a broad frequency range. In order to investigate the validity of Kramers-Kronig relations for GENZ, we have studied the electromagnetic properties of a GENZ slab which is considered as a homogeneous layer with frequency dependent permittivity. The associated Fresnel equations for GENZ is studied using Laplace transform analysis. The changes caused by the two pumped sources at lower and higher frequencies is demonstrated. Finally, the associated Kramers-Kronig relation is validated after a contact with the causality and electromagnetic properties of active media. [Preview Abstract] |
Friday, March 7, 2014 12:39PM - 12:51PM |
Z50.00008: Focusing electromagnetic waves in subwavelength structures by lossy anisotropic media Hui Kin Kwok, Sze Fung Lee, King Chun Lai, Kin Wah Yu Different from subwavelength focusing by negative refractive index slab and microsphere array, we have proposed a new mechanism of subwavelength focusing by lossy radial anisotropy which helps to beat the diffraction limit in near field microscopy. We consider the propagation of a plane polarized electromagnetic wave incident on a nanosphere with anisotropic complex permittivity. For a sphere with complex radial permittivity implying a loss effect on radial component of the electric field, only the tangential component of the field survives, and thus the Poynting vectors can be made to concentrate at the centre of the sphere by increasing the complex permittivity to enhance the radial loss. Extending the study of electromagnetic scattering by coated spheres with lossless radial anisotropy by Gao et al.(2008), we consider a lossy medium and calculate the distribution of electromagnetic field by solving Maxwell's equations with expressing the fields in terms of Debye potentials. Considering the sphere of subwavelength scale and thus the incident fields are nearly quasistatic, the calculation of Poynting vectors inside reveals a focusing effect as expected. This nanosphere also offers a possible way to convert light into a nanospot which leads to applications in computing. [Preview Abstract] |
Friday, March 7, 2014 12:51PM - 1:03PM |
Z50.00009: Broadband Dipole Bonding with Epsilon-near-zero Material Naijing Deng, Kin Wah Yu Epsilon-near-zero dielectrics (ENZ) is known to be responsible for static dipole levitation. Force equilibrium, or dipole bonding appears when the wavelength is comparable to the separation distance. For oscillating dipoles, the bonding position would be dependent on the dispersive dielectric responses of the ENZ plane. We propose a ENZ designing scheme, allowing dipoles with broad frequency range to be bonded simultaneously at one specific position. In the meantime, the Kramer-Kronig relation of ENZ dielectrics is not violated. The dipole mass would linearly shift the bonding position and may bring viable applications in particle filtration. [Preview Abstract] |
Friday, March 7, 2014 1:03PM - 1:15PM |
Z50.00010: A Multi-Mode Hybrid Plasmonic Waveguide with Enhanced Confinement and Propagation John Colanduoni, Daniel Nikolov, Huizhong Xu Waveguides capable of achieving high confinement with low loss are a key goal in the developing field of plasmonics. A hybrid waveguide, which consists of a dielectric wire above a dielectric-metal interface, has been previously proposed with such desirable properties. By exciting this geometry with an aperture in the metal that takes advantage of the extraordinary transmission through sub-wavelength apertures, it is possible to strongly couple to multiple modes. The real part of the fundamental mode is in fact capable of exceeding the index of refraction of all the materials used while maintaining a small imaginary part, as a result of appropriate choice of materials for the dielectric wire and the metal. As the amplitude of the most confined mode is significantly larger than the amplitude of the other modes with poor confinement, this geometry can enable enhanced confinement and propagation in light guiding applications. [Preview Abstract] |
Friday, March 7, 2014 1:15PM - 1:27PM |
Z50.00011: Making structured metals transparency for broadband and wide-incidence-angle electromagnetic waves Renhao Fan, Ruwen Peng, Xianrong Huang, Mu Wang Very recently, we have demonstrated that one-dimensional metallic gratings can become transparent and completely antireflective for extremely broadband electromagnetic (EM) waves under oblique incidence. However, the oblique-incidence geometry, is inconvenient for the technological applications. To overcome this drawback, here we instead use oblique metal gratings with optimal tilt angles to achieve normal-incidence broadband transparence for EM waves. Further we use two-dimensional periodic metallic cuboids to achieve broadband and broad-angle high transmission and antireflection. By introducing such metallic cuboids arrays into silicon solar cells, we find that high performance of light trapping in the cells can be obtained with a significant enhancement of the ultimate quantum efficiency. The structured metals, which achieve broadband and broad-angle high transmission for EM waves, may have many other potential applications, such as transparent conducting panels, white-beam polarizers, and stealth objects. References: R. H. Fan, R. W. Peng, X. R. Huang et al., Adv. Mater. 24, 1980 (2012); R. H. Fan, J. Li, R. W. Peng et al., Appl. Phys. Lett. 102, 171904 (2013); and R. H. Fan, L. H. Zhu, R. W. Peng et al., Physical Review B, 87, 195444 (2013). [Preview Abstract] |
Friday, March 7, 2014 1:27PM - 1:39PM |
Z50.00012: Dark Acoustic Metamaterials Jun Mei, Guancong Ma, Min Yang, Zhiyu Yang, Weijia Wen, Ping Sheng The attenuation of low-frequency sound has been a challenging task because the dissipation of materials in this regime is inherently weak. Here we show that by using thin elastic membranes decorated with asymmetric rigid platelets, the resulting acoustic metamaterials can reach almost unity absorption at frequencies where the relevant sound wavelength in air can be three orders of magnitude larger than the membrane thickness. At resonances, the measured displacement profiles show slope discontinuities around the platelet perimeters, implying significantly enhanced elastic curvature energy is concentrated in these small volumes. This thereby gives rise to strong absorption similar to a cavity system, even though the system is geometrically open. [Preview Abstract] |
Friday, March 7, 2014 1:39PM - 1:51PM |
Z50.00013: Asymmetric Invisibility Cloaking Theory Based on the Concept of Effective Electromagnetic Fields for Photons Tomo Amemiya, Masato Taki, Toru Kanazawa, Shigehisa Arai The asymmetric invisibility cloak is a special cloak with unidirectional transparency; that is, a person in the cloak should not be seen from the outside but should be able to see the outside. Existing theories of designing invisibility cloaks cannot be used for asymmetric cloaking because they are based on the transformation optics that uses Riemannian metric tensor independent of direction. To overcome this problem, we propose introducing directionality into invisibility cloaking. Our theory is based on ``the theory of effective magnetic field for photons'' proposed by Stanford University.\footnote{K. Fang \textit{et al.}, Nature Photon. \textbf{6}, 782 (2012).} To realize asymmetric cloaking, we have extended the Stanford's theory to add the concept of ``effective electric field for photons.'' The effective electric and the magnetic field can be generated using a photonc resonator lattice, which is a kind of metamaterial. The Hamiltonian for photons in these fields has a similar form to that of the Hamiltonian for a charged particle in an electromagnetic field. An incident photon therefore experiences a ``Lorentz-like'' and a ``Coulomb-like'' force and shows asymmetric movement depending of its travelling direction.We show the procedure of designing actual invisibility cloaks using the photonc resonator lattice and confirm their operation with the aid of computer simulation. [Preview Abstract] |
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