Bulletin of the American Physical Society
2008 APS March Meeting
Volume 53, Number 2
Monday–Friday, March 10–14, 2008; New Orleans, Louisiana
Session H35: Focus Session: Negative Index Materials III |
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Sponsoring Units: FIAP Chair: Igor Smolyaninov, BAE Systems Room: Morial Convention Center 227 |
Tuesday, March 11, 2008 8:00AM - 8:36AM |
H35.00001: Plasmonic metamaterials with tuneable optical properties Invited Speaker: Negative refraction in metamaterials has recently attracted significant attention due to its possible numerous applications in high-resolution imaging and photolithography with the so-called ``perfect lenses,'' for electromagnetic shielding (invisibility cloak), optical signal manipulation, etc. Among various realizations of negative index materials, plasmonic nanostructures play a prominent role as they allow negative refraction properties to be engineered in the visible and near infrared spectral ranges. The coupling of light to plasmonic modes, that are collective electronic excitations in metallic nanostructures, provides the possibility to confine the electromagnetic field on the sub-wavelength scale and manipulate it with high precision to achieve the desired mode dispersion and, thus, reflection, absorption and transmission properties of the nanostructures. In this talk we will discuss various pathways to control dispersion of the electromagnetic waves in plasmonic metamaterials, including plasmon polaritonic crystals and plasmonic nanorod arrays, and the approaches to active tuneability of their optical properties using optical and electric control signals. Both approaches take advantage of the very high sensitivity of surface plasmon mode dispersion on the refractive index of the dielectric adjacent to metallic nanostructure. Hybridization of plasmonic nanostructures with molecular species exhibiting nonlinear optical response allows the development of metamaterials with high effective nonlinear susceptibility due to the electromagnetic field enhancement related to plasmonic excitations. Signal and control light are then coupled to plasmonic modes that strongly interact via nonlinearity introduced by the hybridization. Concurrently, the use of electro-optically active dielectrics incorporated into plasmonic nanostructures provides the route to control optical signals electronically. Plasmonic metamaterials with tuneable optical properties can be used to control negative refraction and electromagnetic field propagation in various applications in nanophotonics, optoelectronics and optical communications. [Preview Abstract] |
Tuesday, March 11, 2008 8:36AM - 8:48AM |
H35.00002: Tunable plasmonic negative index nanostructures and nanolenses in optical domain E.V. Ponizovskaya, A.M. Bratkovsky We have designed by means with the use of FDTD method a metamaterial, which is a stack of metallic films with periodic hole arrays separated by dielectric layers (usually called fishnet, FN) to have negative index at IR frequencies. Optical modulation of the effective refractive properties of a FN Ag/Si/Ag metamaterial structure in the near-IR range has been confirmed experimentally [1]. Pump excitation of the amorphous Si layer was found to be responsible for the observed modulation of the effective refractive index [1]. We discuss the use of gain material to compensate the losses. Arrays of metallic nanoparticles or holes support individual and collective plasmonic excitations that contribute to surface enhanced Raman scattering (SERS), anomalous transparency, negative index, and subwavelength resolution in various metamaterials [2]. Using the FDTD and a boundary integral method we design 2D plasmonic nanolenses with thousand-fold field enhancement factor that can be used for single-molecule SERS detection. [1] E. Kim, et al., Appl. Phys. Lett. 91, 173105 (2007) [2] E.V. Ponizovskaya, A.M.Bratkovsky, Appl.Phys. A 87, 161 (2007) [Preview Abstract] |
Tuesday, March 11, 2008 8:48AM - 9:00AM |
H35.00003: Novel acoustic surface plasmons on Cu(111) Karsten Pohl, Bogdan Diaconescu, Luca Vattuone, Mario Rocca The recent discovery of a fundamentally new sound-like plasmon on a bare metal surface of beryllium introduced a new research direction in the area of plasmonics [1]. While conventional surface plasmons are optical modes and have a finite excitation energy of a few eV, the novel acoustic mode can be excited with very low energies of a few meV. This allows, in principle, for a coupling with visible light for signal processing and advanced microscopies as well as new catalysts on metallic surfaces. In order to show that this novel excitation is a general phenomenon on closed-packed noble metal surfaces, as predicted by our theoretical collaborators [2], we have measured the dispersion of the acoustic surface plasmon on Cu(111) by electron energy-loss spectroscopy for a parallel momentum-transfer range from 0 to 0.15 1/{\AA}. We can report that the dispersion is indeed linear (acoustic) with a slope (sound velocity) in good agreement with theory [2], and energy values that extend up to 500 meV. We will discuss the lifetime (decay length) of acoustic surface plasmons.\newline [1] B. Diaconescu, K.Pohl, L. Vattuone, et al., Nature 448, 57 (2007).\newline [2] V.M. Silkin, J.M. Pitarke, et al. Phys. Rev. B 72, 115435 (2005). [Preview Abstract] |
Tuesday, March 11, 2008 9:00AM - 9:12AM |
H35.00004: Thickness dependent plasmon excitation and damping in metallic thin films Zhe Yuan, Shiwu Gao We present a theoretical study of collective plasmon excitation and lifetime in metallic thin films using a jellium model [1, 2]. The excitation spectra are calculated with linear response theory and time-dependent local density approximation. The plasmon energy dispersion follows qualitatively the classical electrodynamical model. For ultrathin films with a few atomic layers, the collective plasmon resonances evolve into single particle transitions at small momenta. The plasmon linewidth due to Landau damping is found to depend exponentially on the film thickness. Quantum oscillations are found in ultrathin films with a period that is about three times longer than the universal period $\lambda_F/2$ observed in many other quantities. This long period results from the dynamical Friedel oscillations in the collective excitation normal to the films. [1] Z. Yuan and S. Gao, Phys. Rev. B 73, 155411 (2006). [2] Z. Yuan and S. Gao, Surf. Sci. in press. [Preview Abstract] |
Tuesday, March 11, 2008 9:12AM - 9:24AM |
H35.00005: Surface Plasmon Polariton Amplification at Telecommunication Frequencies. Muralidhar Ambati, Sunghyun Nam, Dentcho Genov, Erick Ulin-Avila, Xiang Zhang Active plasmonics describes the interaction between an active medium and surface plasmons, and it offers a foundation for fundamental studies and an opportunity to expand surface plasmon based applications. In order to overcome the challenges posed by surface plasmons - primarily the metal losses - recent studies have focused extensively on surface plasmon amplification; however, there has been very limited headway from the experimental front. We present an experimental evidence of the amplification of long range surface plasmon polaritons (SPPs) by stimulated emission at telecom frequencies. We design SPP waveguides - thin gold metal strips - embedded in a gain medium, erbium doped phosphate glass. We confirm SPP amplification by showing an increase in the propagation length of surface plasmons in both pulsed and continuous modes. We present the design, fabrication and measurements of the gold SPP waveguides in erbium doped glass. Such structures will be suitable as integrated coupling devices as well as for the study of plasmon-exciton interface in cavity quantum electrodynamics. [Preview Abstract] |
Tuesday, March 11, 2008 9:24AM - 9:36AM |
H35.00006: Novel electromagnetic effective medium based on nanocoaxes Krzysztof Kempa, Xiwen Wang, Zhifeng Ren, Michael J. Naughton A thin film of an opaque material, pierced with an array of subwavelength coaxial nanowaveguides, decomposes an incident electromagnetic wave into spatially discrete wave components, propagates these components without frequency cut-off through the film, and reassembles them on the far side. The propagation of these wave components is fully controlled by the physical properties of the waveguides and their geometrical distribution in the array. This allows for an exceptional degree of control over the electromagnetic response of this effective medium, with numerous potential applications, including metamaterial functionality enabled in the visible frequency range. [Preview Abstract] |
Tuesday, March 11, 2008 9:36AM - 9:48AM |
H35.00007: Controlling surface plasmons and local field by two-dimensional arrays of metallic nano-bottles Hei Iu, Daniel H.C. Ong, Jones T.K. Wan, Jia Li In recent years, studies of surface plasmon polaritons (SPPs) have been intensive. It is of great interest to control SPPs with great precision and flexibility. In this talk, we present our recent work on SPPs manipulation by using two-dimensional arrays of bottle-shaped, metallic cavities. We propose that by tuning the geometry of such ``nano-bottle'' contained in a two-dimensional nano-scale array it is possible to control the resonance frequencies and near field patterns of different SPP modes. The dispersion relations are not sensitive to the sizes and depths of the nano-bottles, but depends strongly on the polarization In particular, by using different polarizations, it is observed that different types of SPPs, either propagating or localized, can be excited independently. Moreover, we attempt to control the local field by closing up the aperture of the nano-bottle. We have found that the local field slowly moves up from the bottom to the neck of bottle by increasing its depth. In addition, the field intensity can be fine-tuned by controlling the topology of the bottleneck, for example, a smaller and thinner neck leads to stronger field intensity. As a result, we believe these nano-bottle arrays are good candidates for making high sensitivity chemical and biological sensors. [Preview Abstract] |
Tuesday, March 11, 2008 9:48AM - 10:00AM |
H35.00008: Inverse Mapping Structures onto Transparency Kim F. Ferris, Xin Sun, Paul A. Whitney Composite materials have continued to make a number of improvements in physical properties (mechanical moduli), but lag behind in optical responses such as transparency. The hybrid nature of the composite material, particle and host matrix, divides light scattering issues into particle size regimes, where the particle size d $>>$ lambda and approximations such as anomalous dispersion have proven useful, and d$<<$ lambda where more exacting methods are necessary. The real-life difference between the `design' particle size and the practical particle size distribution often finds contributions to light scattering losses from both regimes. Using a ceramic-polymer composite as a case example, we have used black box optimization methods to examine the practical bounds for each regime and to assess design rules. These guidelines suggest limitations for particle morphologies and the optical properties of the component materials. [Preview Abstract] |
Tuesday, March 11, 2008 10:00AM - 10:12AM |
H35.00009: A method for determining refractive indices of epilayers of multi-structure active layer Gagik Shmavonyan The refractive indices of bulk and epitaxially grown materials differ. Besides, it is very difficult to experimentally determine and theoretically calculate the refractive indices of compound semiconductor epitaxial layers of quantum hetero-structures, especially the refractive indices of active layer of multilayer compound semiconductor devices. For that reason the precise determination of the refractive indices of epilayers is actual. A new method for the determination of the refractive indices of epitaxially grown compound semiconductor materials of multilayer heterostructure is suggested. This method is a combination of experimental measurements and theoretical calculations. The equipment for the fulfillment of the suggested method is also elaborated. [Preview Abstract] |
Tuesday, March 11, 2008 10:12AM - 10:24AM |
H35.00010: Electromagnetic field distributions of perfect and imperfect cloaks Tai Hang Fung, Lai Lai Leung, Kin Wah Yu In this work, based on the ideal cloaking model proposed by Pendry et al. [1], we calculate, by first-principles approach, the electric field distributions of ideal cloaks (both spherical and cylindrical) subject to different external electric field sources. The results show that the external electric field of an ideal cloak remains unperturbed and the field inside the cloaking region vanishes, thus verifying that Pendry et al.'s model is indeed perfect. We then extend the investigation to imperfect cloaks, whose permittivity tensors can be perturbed due to dispersion or loss, by solving the appropriate boundary-value problems [2]. The resultant electric field distributions can become nonzero inside the cloaking regions as expected. We further evaluate the visibility of the imperfect cloak against the perturbation. We find small visibility under appropriate conditions. \newline [1] J. B. Pendry, D. Schurig, and D. R. Smith, Science 312, 1780 (2006). \newline [2] L. Dong, J. P. Huang, K. W. Yu and G. Q. Gu, Eur. Phys. J. B 48, 439 (2005). [Preview Abstract] |
Tuesday, March 11, 2008 10:24AM - 10:36AM |
H35.00011: Design of cloaking metamaterials using spectral representation theory Lai Lai Leung, Tai Hang Fung, Kin Wah Yu Controlling the propagation of electromagnetic (EM) waves, for instance in cloaking problem, has become an important topic in nanophotonics. So far, following the cloaking model proposed by Pendry et al. [1], the experimental realization was only limited to the microwave region [2]. Since practical application lies in the visible range, we have extended the investigation to that region by utilizing nanocomposites with reference to the material parameters proposed by Pendry et al. and Shalaev et al. [3]. The calculations can be made much simpler by invoking the spectral representation theory [4]. The loss and dispersion effects, as well as the propagation of EM waves are assessed for the designed cloaking models in order to investigate the cloaking performance. Further analyses show that our models can accomplish the desired cloaking effect in the visible range. Moreover, the loss and dispersion effects are found to be small and acceptable.\newline [1] J. B. Pendry, D. Schurig, and D. R. Smith, Science 312, 1780 (2006). \newline [2] D. Schurig, J. J. Mock, B. J. Justice, S. A. Cummer, J. B. Pendry, A. F. Starr, D. R. Smith Science 314, 5801 (2006). \newline [3] Wenshan Cai, Uday K. Chettiar, Alexander V. Kildishev and Vladimir M. Shalaev, Nature photonics 1 (2007). \newline [4] L. Dong, Mikko Karttunen, K. W. Yu, Phys. Rev. E 72, 016613 (2005). [Preview Abstract] |
Tuesday, March 11, 2008 10:36AM - 10:48AM |
H35.00012: Nonlinear Cerenkov radiation in a two-dimensional nonlinear photonic crystal waveguide. S.N. Zhu, Y. Zhang, Z. Yan, Z. Qi, G. Zhao We present a new type of quasi-phase-matched Cerenkov radiation generation from a two- dimensional nonlinear photonic crystal waveguide: a hexagonally poled LiTaO3 waveguide. The waveguide was fabricated by field poling followed by proton exchange technique. The fundamental source was a LD-pumped, 90-ns pulsed Q-switch double wavelength Nd:YAG laser at 1064-$\mu $m and 1319-$\mu $m. The pulse repetition rates was 8-kHz. When the fundamental beams at 1064-$\mu $m and 1319-$\mu $m were collinearly focused into the waveguide and propagated along its x-axis, multiple radiation spots at red, yellow, green with different propagation directions and radiation angles are simultaneously exhibited from such a hexagonally poled waveguide. Scattering involved erenkov arc is also observed. These frequency conversion processes were realized by guided-to-radiated mode interaction. Phase-matching for these processes in the waveguide was automatically achieved by a quasi-phase-matched Cerenkov configuration. [Preview Abstract] |
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