Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session G16: Focus Session: Negative Refractive Index II |
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Sponsoring Units: FIAP Chair: Gennady Shvets, University of Texas Room: Baltimore Convention Center 312 |
Tuesday, March 14, 2006 8:00AM - 8:36AM |
G16.00001: Light in Strongly Anisotropic Media: Towards Negative Index Materials at Optical Frequencies Invited Speaker: |
Tuesday, March 14, 2006 8:36AM - 8:48AM |
G16.00002: Mid-infrared transmission and reflection measurements of degenerately doped quantum wells A. J. Hoffman, L. Alekseyev, E. E. Narimanov, C. Gmachl, D. L. Sivco Degenerately doped quantum wells are proposed as a non-magnetic left-handed material in the mid-infrared wavelength range. Such anomalous wave propagation is predicted for waveguides with highly anisotropic dielectric constants. [V. A. Podolskiy, et al. Phys.Rev. B \textbf{71}, 201101 (2005)] Three samples consisting of 85 {\AA} AlGaAs/InGaAs quantum wells and barriers were prepared. Doping densities of 1.7x10$^{19}$ cm$^{-3}$ and 1.1x10$^{19}$ cm$^{-3}$ were used for the degenerately doped samples and compared to a control sample doped 2x10$^{17}$ cm$^{-3}$. Reflectance and transmittance as a function of incident angle, wavelength, and polarization were measured. Strong resonances were observed at 10.9 $\mu $m and 13.2 $\mu $m, respectively, for the two highly doped samples over a wide range of experimental incident angles (35\r{ } -- 75\r{ }) for the relative reflectance of transverse magnetic to transverse electric polarization. No such resonances were observed for the low-doped sample or a highly doped bulk InGaAs sample. [Preview Abstract] |
Tuesday, March 14, 2006 8:48AM - 9:00AM |
G16.00003: Imaging with negative-refraction planar waveguides Robyn Wangberg, Evgenii Narimanov, Viktor Podolskiy We study the electromagnetic properties of planar waveguides with non-magnetic strongly anisotropic dielectric cores. We develop an analytical description of the mode propagation in these systems and show that their index of refraction can be either positive or negative depending on the configuration. We further demonstrate that it is possible to combine planar waveguide structures to build a planar lens. We study the far-field resolution limit of such a lens and show that it is feasible to achieve resolution better than the free-space diffraction limit. The coupling to and from planar waveguide systems is also explored. [Preview Abstract] |
Tuesday, March 14, 2006 9:00AM - 9:12AM |
G16.00004: Super-Lensing and Sub-Wavelength Antennas in Mid-IR Using Silicon Carbide Gennady Shvets, Dmitriy Korobkin, Yaroslav A. Urzhumov, Christian Zorman Extraordinary properties of SiC in mid-infrared (negative dielectric permittivity and small losses) make it an ideal building block for making negative index meta-materials in that important part of the electromagnetic spectrum. We report on a series of experiments demonstrating that thin films of SiC can be used as a ``perfect'' near-field lens. We have theoretically designed and experimentally implemented a super-lens ion mid-IR using SiC. We also report excitation of electrostatic resonances of two structures based on a sub-micron film of crystalline silicon carbide: (a) nano-holes drilled in the free-standing SiC membrane, and (b) metallic nano-posts evaporated on the SiC membrane. Applications of nano-hole resonances to excitation of magnetic moments in nano-structured SiC and development of negative index materials will be discussed, as will be the prospects of using nano-structured SiC films for laser processing of materials on a nanoscale. [Preview Abstract] |
Tuesday, March 14, 2006 9:12AM - 9:24AM |
G16.00005: Surface Enhanced Raman Scattering from Vertical Arrays of Silver Nanowires G. Chen, J. Habib, T. Russin, H.G. Guitierrez, Peter Eklund We present results of optical studies of surface plasmons and surface enhanced Raman scattering (SERS) from vertical arrays of Ag nanowires. Arrays based on Ag wires with mean diameters d=100 nm have been studied. The wires were grown electrochemically in the pores of anodic aluminum oxide (AAO). To test the SERS activity of these vertical Ag nanowires arrays, we have carried out experiments to detect pyridine on the surface of the nanowires. The SERS enhancement factor is found to be in the order of 10$^{6}$ compared to the Raman signal from bulk liquid. We also studied the surface plasmons of these nanowire arrays in transmission with the incident photon wavevector approximately parallel to the wire axis. Calculations of the plasmon resonances have been made and are found in reasonable agreement with the data. [Preview Abstract] |
Tuesday, March 14, 2006 9:24AM - 9:36AM |
G16.00006: Modeling Surface Plasmon Enhanced Contact Lithography Matthew Arnold, Richard Blaikie Surface Plasmon Enhanced Contact Lithography (SPECL) is a technique for improving sub-wavelength image quality by placing a noble metal beneath the imaging layer in the near-field of a mask. Previous computational[1,2] and experimental[3] studies suggest that that SPECL can improve process latitude compared to pure contact techniques, but future investigations will benefit from a better understanding of the underlying mechanism. We present some numerical simulations, and interpret the results in terms of balanced interference of the ``sources'' consisting of the mask at the top and coupled plasmons at the bottom. Reflected evanescent fields are amplified by a factor that increases with the lateral propagation constant, and hence the usual ``phase'' decay is partially compensated. The observation of an optimal coupling distance is consistent with the inverse relationship between coupling distance and plasmon amplitude compared to the mask fields. Finally we present some data relevant to future experimental exploration. [1] R.J. Blaikie, and S. J. McNab, Assoc. of Asia Pacific Physical Societies Bull. \textbf{11}(3), 15 (2002). [2] D.B. Shao, and S.C. Chen, Opt. Express \textbf{13}, 6964 (2005). [3] D.B. Shao, and S.C. Chen, Appl. Phys. Lett. \textbf{86}, 253107 (2005). [Preview Abstract] |
Tuesday, March 14, 2006 9:36AM - 9:48AM |
G16.00007: A model for the influence of granularity in a negative refractive index metamaterial lens Kevin Webb, Jia-Han Li An important goal in building a negative refractive index metamaterial lens at optical frequencies is the achievement of sub-wavelength image resolution. In assigning an effective medium negative refractive index, the electric and magnetic dipoles (which give rise to negative permittivity and permeability) need to be dense relative to the wavelength, i.e., operation near the center of the first Brillouin zone is a prerequisite. Sub-wavelength imaging requires good performance for a significant portion of the evanescent plane wave spectrum. We use a model comprised of discrete regions with negative permittivity and permeability, calculate the effective medium parameters, and show the impact of granularity level (scatterer density) on the performance of a discrete lens, using the slab lens as a reference. We thus arrive at a measure of metamaterial density required to achieve significant improvement over traditional lensing approaches. [Preview Abstract] |
Tuesday, March 14, 2006 9:48AM - 10:00AM |
G16.00008: Circuit elements at optical frequencies: A synthesis of first principles electronic structure and circuit theories C. Tang, R. Ramprasad We present a new first principles based method to determine the equivalent circuit representations of nanostructured physical systems at optical frequencies. This method involves the determination of the frequency dependent effective permittivity of two constructs: an ordered composite system consisting of physical nano-elements using density functional theory, and an ordered arrangement of impedances using transmission line theory. Matching the calculated effective permittivity functions of these two constructs has enabled a mapping of the physical nano-system to its equivalent circuit. Specifically, we will show that silicon nanowires and carbon nanotubes can be represented as a series combination of inductance, capacitance and resistance. Once this mapping has been reasonably accomplished for a variety of physical systems, the nano-elements can be combined suitably to result in equivalent circuit topologies appropriate for optical and nanoelectronic devices, including left-handed (or negative refractive index) materials. [Preview Abstract] |
Tuesday, March 14, 2006 10:00AM - 10:12AM |
G16.00009: 1-D, 2-D and 3-D Negative-Refraction Metamaterials at Optical Frequencies: Optical Nano-Transmission-Line and Circuit Theory Nader Engheta, Andrea Alu In recent years metamaterials have offered new possibilities for overcoming some of the intrinsic limitations in wave propagation. Their realization at microwave frequencies has followed two different paths; one consisting of embedding resonant inclusions in a host dielectric, and the other following a transmission-line approach, i.e., building 1-D, 2-D, or 3-D cascades of circuit elements, respectively, as linear, planar or bulk right- or left-handed metamaterials. The latter is known to provide larger bandwidth and better robustness to ohmic losses. Extending these concepts to optical frequencies is a challenging task, due to changes in material response to electromagnetic waves at these frequencies. However, recently we have studied theoretically how it may be possible to have circuit nano-elements at these frequencies by properly exploiting plasmonic resonances. Here we present our theoretical work on translating the circuit concepts of right- and left-handed metamaterials into optical frequencies by applying the analogy between nanoparticles and nanocircuit elements in transmission lines. We discuss how it is possible to synthesize optical negative-refraction metamaterials by properly cascading plasmonic and non-plasmonic elements in 1-D, 2-D and 3-D geometries. [Preview Abstract] |
Tuesday, March 14, 2006 10:12AM - 10:24AM |
G16.00010: Three and four wave mixing in negative refractive index materials.. Ildar Gabitov, Andrei Maimistov Nonlinear mixing of waves with different frequencies in materials with negative refractive index represents a new mechanism in nonlinear optics. We will consider spatio-directional effects for parametric amplification in negative refractive index materials (NRI) with quadratic nonlinearity. We will also investigate photon echo in NRI materials with lambda configuration active dopants. [Preview Abstract] |
Tuesday, March 14, 2006 10:24AM - 10:36AM |
G16.00011: Numerical Calculations of the Magnetic Susceptibility of Split Gold Nanorings Jeremy Neal, Bahman Taheri, Peter Palffy-Muhoray Metamaterials consisting of split ring resonators have shown negative permeabilities at microwave frequencies. A key challenge is the realization of such a negative index material in the visible spectrum. We consider here the magnetic susceptibility of cut gold nanorings as function of frequency. We have carried out numerical calculations of the polarizability of such particles using the Discrete Dipole Approximation of Draine and Flatau. We present our results for the magnetic susceptibility of different nanoparticle geometries, and compare our results with theoretical estimates. Since the susceptibilities are strongly anisotropic, liquid crystal-like orientationally ordered assemblies of such nanostructures may be useful in realizing bulk optical NIM materials. [Preview Abstract] |
Tuesday, March 14, 2006 10:36AM - 10:48AM |
G16.00012: Consequences of Spatial Antisymmetry on Light. Angelo Mascarenhas, Brian Fluegel When light traverses an interface across which the permittivity, $\varepsilon $, and permeability, $\mu $, change sign, it undergoes negative refraction and the medium with negative values of $\varepsilon $ and $\mu $ must be interpreted as having a negative refractive index $n=-\sqrt{\varepsilon \mu}$. In the past few years this has been experimentally demonstrated by several groups. We have analyzed light propagating in lattices comprised of 2-D tilings in which alternating tiles are made up of media with refractive index whose values alternate in sign acoss tile boundaries. Using both numerical ray tracing and wave equation expansion, we show that when the tiling belongs to certain antisymmetric plane groups, every light ray is exactly bound into a closed, lossless path. The extension to antisymmetric 3-D space groups is also discussed. The study provides unique insights into the consequences of spatial antisymmetry on light. [Preview Abstract] |
Tuesday, March 14, 2006 10:48AM - 11:00AM |
G16.00013: Measured polarization rotation loss in negative index metamaterials John Derov, Beverly Turchinetz, Everett Crisman, Drayton Hanna, Alvin Drehman The loss mechanisms in left-handed or negative refractive index metamaterial are still not well understood, even for the most common volumetric form using split ring resonators and posts at microwave frequencies. Loss due to polarization rotation, which can only be determined in free space experiments, is both a significant and neglected mechanism. We have measured rotation angles as large as 25 degrees after transmission through negative index media. Polarization rotation is observed as a radiative loss since it reduces the co-polarized power transmitted through the medium. The apparent loss can be reduced by optimizing the receiver polarization. We have measured metamaterial shaped as wedge prisms and rectangular blocks, thereby including and excluding refraction effects. Wedge prisms necessarily include refraction effects. The rectangular blocks can exclude or include refraction by changing the incident angle from normal to oblique. We have investigated whether the polarization type of the transmitted wave is linear or elliptical by using circularly polarized receiver antennas. The results of these measurements will be presented and discussed. [Preview Abstract] |
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