Bulletin of the American Physical Society
2007 APS March Meeting
Volume 52, Number 1
Monday–Friday, March 5–9, 2007; Denver, Colorado
Session X38: Focus Session: Negative Index Materials: Concepts to Applications III |
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Sponsoring Units: FIAP Chair: Nader Engheta, University of Pennsylvania Room: Colorado Convention Center 501 |
Friday, March 9, 2007 8:00AM - 8:36AM |
X38.00001: Negative Refraction in Metamaterials and Surface Plasmonics Invited Speaker: In this talk, we explore general requirements on negative-refraction metamaterials imposed by the fundamental principle of causality [1]. We show that the causality imposes lower limit on optical losses at and near the observation frequency. We also discuss specific, exactly solvable models of nanoplasmonic materials that possess the negative refraction [2] and compare them with the predictions of the exact theory based on the dispersion relations. From the requirements of causality, we derive the dispersion relation for squared refraction index $n^2(\omega )$ of a metamaterial (optically-linear refraction is considered). Using this relation, we derive a rigorous criterion of the negative refraction with a low optical loss at observation frequency $\omega $ as \[ \frac{2}{\pi }\int\limits_0^\infty {\frac{{\varepsilon }''(\omega ){\mu }'(\omega )+{\mu }''(\omega ){\varepsilon }'(\omega )}{\left( {\omega _1^2 -\omega ^2} \right)^2}} \omega _1^3 d\omega _1 \le -1, \] where ${\varepsilon }'(\omega )$ and ${\mu }'(\omega )$ are the real parts of the permittivity and permeability, and ${\varepsilon }''(\omega )$ and ${\mu }''(\omega )$ are their imaginary parts describing the electric and magnetic losses. This criterion imposes the lower limits on the electric and magnetic losses in the region of the negative refraction. If these losses are eliminated or significantly reduced by any means, including the compensation by active (gain) media, then this criterion is violated and the negative refraction will disappear. This criterion can be particularly useful in designing new left-handed materials: testing the expected polarizabilities of a medium against this criterion would check the compliance with the causality and verify the design feasibility. As examples of this general criterion, we consider negative refraction of surface plasmon polaritons in three exactly-solvable nanoplasmonic systems: metal nanolayer in dielectric, dielectric nanolayer in metal, and a dielectric nanolayer on metal surface. In all these three cases, the regions of negative refraction are also those of very strong absorption where extinction of the optical wave occurs on a distance on order of the wavelength. This is in accord with the obtained criterion. \textbf{References} 1. M. I. Stockman, \textit{Does Nature Allow Negative Refraction with Low Losses in Optical Region?}, cond-mat/0611350 (2006). 2. M. I. Stockman, \textit{Slow Propagation, Anomalous Absorption, and Total External Reflection of Surface Plasmon Polaritons in Nanolayer Systems}, Nano Lett. \textbf{6}, 2604-2608 (2006). [Preview Abstract] |
Friday, March 9, 2007 8:36AM - 8:48AM |
X38.00002: A new mechanism for negative refraction and focusing using selective diffraction from surface corrugation W. T. Lu, Y. J. Huang, P. Vodo, R. K. Banyal, C. H. Perry, S. Sridhar Refraction at a smooth interface is accompanied by momentum transfer normal to the interface. We show that corrugating an initially smooth, totally reflecting, non-metallic interface provides a momentum kick parallel to the surface, which can be used to refract light negatively or positively. This new mechanism of negative refraction is demonstrated by visible light and microwave experiments on grisms (grating-prisms), and is used to create a new optical device, a grating lens. A plano-concave grating lens is demonstrated that focuses plane microwaves to a point image. Single-beam all-angle-negative-refraction is achieved by incorporating a surface grating on a flat multilayered material. These results show that customized surface engineering can be used to achieve negative refraction even though the bulk material has positive refractive index. The surface periodicity provides a tunable parameter to control beam propagation leading to novel optical and microwave devices. [Preview Abstract] |
Friday, March 9, 2007 8:48AM - 9:00AM |
X38.00003: Resonant enhancement of absorption in the superlens Leonid Alekseyev, Zubin Jacob, Evgenii Narimanov The Veselago lens (also known as the super lens) [1], which is a slab made of left handed material with $\varepsilon $=-1 and $\mu $=-1 has interesting properties like perfect lensing [2] and cloaking [3]. When a source is placed in front of it there are regions of high field intensity in such a lens , known as anomalously localized resonant regions [3]. For practical applications of the superlens taking advantage of these properties, the effect of finite loss on the device performance is critical [4] . We calculate the absorption loss of dipole radiation by an $\varepsilon <$0 and $\mu <$0 slab and find resonant enhancement of absorption in the superlensing regime. \newline [1] V. G. Veselago, ``The electrodynamics of substances with simultaneously negative values of permittivity and permeability,'' Sov. Phys. Usp. \textbf{10}, 509 (1968). \newline [2] J. B. Pendry, ``Negative refraction makes a perfect lens,'' Phys. Rev. Lett. \textbf{85}, 3966-3969 (2000). \newline [3] Graeme W. Milton and Nicolae-Alexandry P. Nicorovici ``On the cloaking effects associated with anomalous localized resonance,'' Proc. R. Soc. A (2006) 462, 3027-3059. \newline [4] V. A. Podolskiy and E. E. Narimanov, ``Near-sighted superlens,'' Opt. Lett. \textbf{30}, 75-77 (2005) [Preview Abstract] |
Friday, March 9, 2007 9:00AM - 9:12AM |
X38.00004: Negative Index Metamaterials at Optical Frequencies: Theory and Experiment E. Ponizovskaya, A.M. Bratkovsky Pafomov and Veselago showed in 1950-60s that negative refraction should occur in homogeneous media with simultaneously negative dielectric permittivity and magnetic permeability, $\epsilon<0$, $\mu<0$. Pendry (2000) speculated that the ideal Veselago lens can produce sub- wavelength resolution. We find a strong effect of surfaces on resolution limit and nontrivial relation of subwavelength imaging to EM ``softness'' of the lens [1]. We have designed the metamaterial by means of FDTD modeling, which is a stack of metallic films with periodic hole arrays separated by dielectric layers (called ``fishnet'', FN) to work at IR wavelengths $\lambda=1.5- 1.6 \mu$m. The FN samples have been fabricated by nanoimprint lithography[2]. The transmission and reflectance characteristics of the samples have been measured by laser spectroscopic ellipsometry and showed unambiguously that the FN supports the ``backward'' waves and have overall negative index of refraction at IR frequencies. We also show that single layers of FN structure have positive index. We also address the questions of countering losses by using gain medium, limits sub-wavelength resolution, and focusing. 1. A.M. Bratkovsky, A.Cano, and A.P. Levanyuk, Appl. Phys. Lett. 87, 103507 (2005). 2. W. Wu et al., cond-mat/0610352. [Preview Abstract] |
Friday, March 9, 2007 9:12AM - 9:24AM |
X38.00005: Surface resonant states in acoustic and elastic metamaterials Muralidhar Ambati, Dongmin Wu, Xiang Zhang We discuss a new type of surface acoustic wave at an interface between two media, one of which is a metamaterial. In contrast to the familiar case where the surface acoustic waves exist at solid-fluid and solid-solid interfaces, these unique waves exist because of the negative material responses in metamaterials. We explore the existence of a surface wave a) at the interface of a fluid and an acoustic metamaterial modeled as a fluid and b) at the interface of a solid and an elastic metamaterial modeled as a solid. The latter case is for shear waves with horizontal polarization (SH). In each of these two cases, first, we discuss the necessary and sufficient conditions on the material properties of metamaterials for the existence of surface modes. Second, we offer the microscopic picture of these surface modes in terms of particle trajectories at the interfaces. Next, we examine the unique characteristics of these surface states; as a result, we propose and numerically demonstrate an acoustic superlens for sub-diffraction limited imaging. Finally, we provide a design for metamaterials that can lead to the surface states and make a significant impact in ultrasonic imaging. [Preview Abstract] |
Friday, March 9, 2007 9:24AM - 9:36AM |
X38.00006: Embeddable Metal Coil Microparticles for 3-D Metamaterial Applications C. K. Harnett, E. V. Moiseeva, Y. M. Senousy We will discuss our recent efforts in strain-based self-assembly of metal/insulator bilayers for production of freestanding metal coil microparticles in the sub-200 micron diameter range. This process has generated microparticles having metal coils in three orthogonal planes, demonstrating a possible route to polarization-insensitive metamaterials. Other designs such as ``Swiss roll'' shapes, coils in only one or two planes, or coils in non-orthogonal planes are also achievable by this method. Because the coils are assembled out-of-plane using strain mismatch between two thin films, particle diameter is governed mainly by film thickness, rather than by lithographic patterning as in planar split-ring resonators. These microparticles may be detached from the substrate by etching. Assortments of particles may function as taggants with an engineered spectral signature in the microwave to terahertz range. Surprisingly, such particles are robust enough to be embedded and detached into a flexible polymer cast over the substrate. Detaching entire arrays preserves particle orientation and any spatial gradients designed into the array. Stacking arrays of embedded resonant particles, or distributing freestanding particles uniformly throughout a dielectric matrix, will enable production of machinable, three-dimensional electromagnetic metamaterials. [Preview Abstract] |
Friday, March 9, 2007 9:36AM - 9:48AM |
X38.00007: Nanophotonic structures for Negative Refraction at NIR and VIS Ravinder Banyal, B.D.F. Casse, Plarenta Vodo, W.T. Lu, Srinivas Sridhar Nanophotonic structures were fabricated for negative index refraction at NIR and VIS frequencies. Structures include prisms and flat lenses fabricated in Si using nanolithography. Refraction and imaging experiments were carried out at NIR and VIS. Natural divergence of laser beam, collimation and guiding of the light within the device structures are also discussed. [Preview Abstract] |
Friday, March 9, 2007 9:48AM - 10:00AM |
X38.00008: Towards 3D and Multilayer Electromagnetic Metamaterials Structures in the THz Range B. D. F. Casse, H. O. Moser, J. W. Lee, S. Inglis, M. Bahou, L. K. Jian V. G. Veselago predicted that left-handed materials would exhibit a plethora of unusual effects such as a negative index of refraction as used in Snell's law, a reverse Doppler and \v {C}erenkov effect. This novel class of materials, following Pendry's recipes, can potentially restore evanescent waves to focus subwavelength details in an image. Micron-size electromagnetic metamaterials (EM$^3$) structures which exist so far were produced and characterized as single layer structures. Furthermore the structures were produced with a low yield. In the first part of the talk, we will present techniques for producing copious amount of EM$^3$ chips via the LIGA process using Synchrotron radiation and demonstrate assembly of the first multilayer THz EM$^3$ structures. The planar micro- or nanoEM$^3$ produced so far are also highly anisotropic. Recently, we proposed schemes to produce more isotropic structures, within the same matrix, via tilted X-ray exposures that were introduced in the LIGA process years ago. In the second part of the talk, we will show the results of microfabrication of nearly 3D EM$^3$ structures for the THz range. [Preview Abstract] |
Friday, March 9, 2007 10:00AM - 10:12AM |
X38.00009: Nonlinear Absorption in Nanoparticle Suspensions and Aerogels Yi Huang, Ashish Agarwal, Piotr Lesiak, Nick Kotov, David Carroll, Peter Palffy-Muhoray Nonlinear optics can be used to study materials structure by inferring material properties from characteristics of the mechanisms responsible for the nonlinear response. We have carried out ns and ps Z{\_}scan experiments to determine the nonlinear absorption and refraction in pure and dye containing aqueous solutions of Au nanorods and self-assembled polymer coated Ag nanowire glass gels. The enhancement of nonlinear absorption by the presence of nanoparticles can be related to the nanoparticle shape, linear response as well as concentration. We present our results for nonlinear refraction as well as nonlinear absorption, and discuss our results in terms of simple models. [Preview Abstract] |
Friday, March 9, 2007 10:12AM - 10:24AM |
X38.00010: Plasma-like negative capacitance in a nano-colloid Jason Shulman, Feng Chen, Stephen Tsui, Yuyi Xue, C. W. Chu A negative capacitance has been observed in an electrorheological fluid consisting of urea-coated Ba$_{0.8}$Rb$_{0.4}$TiO(C$_{2}$O$_{4})_{2}$ nanoparticles in silicone oil. The response is linear over a broad range of conditions. Previously, it was shown that this phenomenon originates at the surfaces of the nanoparticles. In this work, we demonstrate that the low frequency dispersions of both the resistance and capacitance are consistent with the free-carrier plasma model, while the transient behavior demonstrates an unusual energy storage mechanism. [Preview Abstract] |
Friday, March 9, 2007 10:24AM - 10:36AM |
X38.00011: ABSTRACT HAS BEEN MOVED TO S33.00014 |
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