Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session D16: Focus Session: Negative Refractive Index I |
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Sponsoring Units: FIAP Chair: Vladimir M Shalaev, Purdue University Room: Baltimore Convention Center 312 |
Monday, March 13, 2006 2:30PM - 2:42PM |
D16.00001: Single Superconducting Split-Ring Resonator Electrodynamics Michael C. Ricci, Steven M. Anlage In order to create compact metamaterial devices in the microwave frequency range, current designs must be scaled down to smaller dimensions. However, at such scales, normal metal losses dominate, and desirable device properties ({\it e.g.} negative index of refraction) are lost. We investigate the properties of superconducting Nb metamaterials that do not suffer from these limitations. The experiments are performed in an all-Nb waveguide, with Nb wires and Nb thin film split-ring resonators (SRRs). Transmission experiments performed in vacuum show a narrow, deep notch for a single Nb SRR (quality factor $\sim 50,000$), and no notch for a Cu resonator of similar dimensions. Adding SRRs increases the notch bandwidth, but decreases the insertion loss of individual resonators. In addition, placing a single superconducting SRR into an array of superconducting wires produces a single negative-index passband 40 dB above the noise floor, with a quality factor of $\sim 22,000$. Models based on the permeability of individual SRRs and the effective dielectric response of a wire array are used to fit the data. This work is supported by the NSF through Grant No. NSF/ECS-0322844, and the DI Outreach Program. [Preview Abstract] |
Monday, March 13, 2006 2:42PM - 2:54PM |
D16.00002: Experiments on the Goos-H\"{a}nchen shift with negative and positive index of refraction materials Nathan Orloff, Michael Ricci, Collin Anderson, Christian Long, Sudeep Dutta, Steven Anlage ~ The negative Goos-H\"{a}nchen shift occurs when a beam of radiation having a finite transverse extent undergoes total internal reflection at a positive to negative index of refraction interface, hence the reflected beam experiences a negative lateral shift. This phenomenon has been predicted for materials with a negative index of refraction. We investigate a composite wire and split-ring resonator medium between 8-12 GHz, based on that first implemented by [1]. In addition, we present an experiment to investigate the Goos-H\"{a}nchen shift and show preliminary results on transmission, refraction, and total internal reflection. Work supported by NSF/ECS-0322844. [1] R. Shelby, D. R. Smith and S. Schultz, Science, 292, 77 (2001) [Preview Abstract] |
Monday, March 13, 2006 2:54PM - 3:06PM |
D16.00003: Optical properties of Ag nanoparticle arrays: Tuning the plasmon resonance J.R. Simpson, H.D. Drew, S.H. Guo, R. Phaneuf Potential applications in the optical spectral range of meta-materials displaying negative permittivity and negative permeability has driven recent interest in nanostructured materials. Electromagnetic radiation incident on metallic nanoparticles induces a collective electronic excitation, or plasmon, which results in a detectable optical resonance. We report polarization-dependent transmission measurements of Ag nanoparticle arrays in the near-infrared to visible frequency range. E-beam lithography patterns arrays of nanoparticles from Ag deposited on transparent ITO-glass substrates. The array grid spacing is several hundred nanometers and the nanoparticle thickness and width are approximately 75\,nm. We vary the length to provide an in-plane aspect ratio (length to width) from 1\,:\,1 to 4\,:\,1. The resonance shifts to lower (higher) energy with increasing aspect ratio for polarizations parallel to the long (short) axis. This work demonstrates the ability to tune optical resonance energies and widths in nanostructured materials with quality factors $Q$ exceeding $10$. Additionally, we discuss the effects of radiation damping, carrier scattering, and inhomogeneous broadening on the resonance widths. [Preview Abstract] |
Monday, March 13, 2006 3:06PM - 3:42PM |
D16.00004: Large-Area Infrared Metamaterials using Interferometric Lithography Invited Speaker: Large area (several cm$^{2})$ mid- and near-infrared metamaterial samples including analogs to split ring resonators and negative index materials have been fabricated using interferometric lithography and standard integrated circuit fabrication techniques. The split ring resonators are vertical structures with the smallest dimensions defined by deposition rather than by lithography. The negative index material is a Au-Al$_{2}$O$_{3}$-Au stack structure perforated with a 2D hole pattern. Both the amplitude and phase of the transmission and reflectivity are measured with phase-mask, zero-path-length difference, interferometric techniques and the refractive index is deduced by inverting these measurements. A rigorous coupled wave analysis (RCWA) is in excellent agreement with the measurement. Improvements in the original structure to provide a lower loss and an improved transmission for the structure are presented. Prospects for continued reduction in the loss and an improved figure of merit, [$\vert $Re($n)\vert $/Im($n)$], are discussed. Interferometric lithography provides an inexpensive, facile, large-area technology for the fabrication of visible/infrared metamaterials with a 2D array patterning capability extending to as small as 30-nm features. [Preview Abstract] |
Monday, March 13, 2006 3:42PM - 3:54PM |
D16.00005: Zero-n band-gap in 1D periodically layered photonic superlattices Nicolae Panoiu, Richard Osgood, Shuang Zhang, Steven Brueck We demonstrate that photonic superlattices consisting of a periodic distribution of alternating layers of materials with positive and negative index of refraction present a photonic band-gap at a frequency at which the spatial average of the index of refraction is zero (these stop bands are called zero-n band-gaps). We prove that these results can be generalized to two cases, namely i) a superlattice of alternating layers, one layer made of a homogeneous material with positive index of refraction and the other layer consisting of a photonic crystal, with negative index of refraction and ii) a superlattice consisting of alternating photonic crystal slabs, which, have positive and negative index of refraction. We demonstrate that, in both cases, the central frequency of the zero-n band-gap corresponds to the frequency at which the spatial average of the refractive index, taken over the unit supercell, is zero. We also show that, unlike the Bragg gaps, these zero-n band-gaps are invariant to the geometrical scaling of the superlattice or the direction of wave propagation in the superlattice. [Preview Abstract] |
Monday, March 13, 2006 3:54PM - 4:06PM |
D16.00006: Negative Refraction in One-Dimensional Photonic Crystal Plarenta Vodo, Wentao Lu, Patanjali Parimi, Srinivas Sridhar We demonstrate experimentally negative refraction of plane waves by a one-dimensional Photonic crystal (PhC) prism at microwave frequencies. The prism was fabricated from a microwave alumina PhC acting as a left-handed metamaterial. Focusing of plane waves from a one-dimensional PhC plano-concave lens is predicted theoretically and realized experimentally. The focal point is observed to move with the radius of curvature of the lens. The measured values of refractive index are in complete agreement with those determined from band structure calculations. [Preview Abstract] |
Monday, March 13, 2006 4:06PM - 4:18PM |
D16.00007: Determination of Refractive Indices of Photonic Crystals: Theory and Experiments Wentao Lu, Srinivas Sridhar We develop a method to calculate the refractive indices of photonic crystal based on plane wave expansion. The appearance of surface waves and subwavelength imaging is explained within this frame. Numerical simulations of 1D and 2D crystals are performed to support our theory. Comparisons are presented with experimental results on microwave photonic crystals. [Preview Abstract] |
Monday, March 13, 2006 4:18PM - 4:30PM |
D16.00008: Free space microwave focusing by a negative-index gradient lens Tom Driscoll, Patrick Rye, Dimitri Basov, Sia Nemat-Nasser, Tony Starr, David Schurig, David Smith The complexity of left-handed metamaterials has advanced rapidly to the point where direct applications are now viable. We present a radial gradient-index lens with an index-of-refraction ranging from -2.67(edge) to -0.97(center). Experimentally, we find the lens can produce field intensities at the focus that are greater than that of the incident plane wave. These results are obtained at 10.3 GHz and are in excellent agreement with full-wave simulations. We also discuss the design and construction of this lens - which involved an advanced fabrication technique using conventional printed circuit board technology. This technique offers significant design, mechanical, and cost advantages over other microwave lens constructions. [Preview Abstract] |
Monday, March 13, 2006 4:30PM - 4:42PM |
D16.00009: Dynamical Electric and Magnetic Metamaterial Response at Terahertz Frequencies Willie Padilla, Antoinette Taylor, Clark Highstrete, Mark Lee, Richard Averitt Utilizing terahertz time domain spectroscopy, we have characterized the electromagnetic response of a planar array of split ring resonators (SRRs) fabricated upon a high resistivity GaAs substrate. The measured frequency dependent magnetic and electric resonances are in excellent agreement with theory and simulation. For two polarizations the SRRs yield negative electric response ($\epsilon<0$). We demonstrate, for the first time, dynamical control of the electrical response of the SRRs through photoexcitation of free carriers in the substrate. An excited carrier density of $\sim4 \times 10$$^{16}$cm$^{-3}$ is sufficient to short the gap of the SRRs thereby turning off the electric resonance demonstrating the potential of such structures as terahertz switches. Due to the universality of metamaterial response over many decades of frequency, these results have implications for other regions of the electromagnetic spectrum. [Preview Abstract] |
Monday, March 13, 2006 4:42PM - 4:54PM |
D16.00010: Nanofabricated materials with negative refractive indices at optical wavelengths Wenshan Cai, Uday Chettiar, Hsiao-Kuan Yuan, Vladimir Drachev, Alexander Kildishev, Andrey Sarychev, Vladimir Shalaev The efforts to construct media exhibiting negative refraction have been extended to the optical range. In this work we present examples of structures with negative refraction at optical frequencies, including paired nanorods arrays and coupled metal strips. The negative refractive indices in such nanofabricated metamaterials result from plasmon resonances for both the electric and magnetic components of light at overlapping wavelength ranges. Simulations and experimental verification of the negative indices are demonstrated. The agreement between simulations and experimental data is excellent, confirming the validity of the proposed structures as negative index materials. Optimization of the parameters of the nanostructure is also discussed. [Preview Abstract] |
Monday, March 13, 2006 4:54PM - 5:06PM |
D16.00011: Negative static dielectric constant in a nano-colloid Jason Shulman, Stephen Tsui, Feng Chen, Yuyi Xue, C. W. Chu We have investigated the dielectric properties of assemblies of urea-coated Ba$_{0.8}$Rb$_{0.4}$TiO(C$_{2}$O$_{4})_{2}$ nanoparticles. The effective dielectric constant, $\varepsilon $', is negative below a certain bias dependent frequency. $\varepsilon $' follows a plasma-like dispersion with an extremely low plasma frequency and damping rate. This dielectric response is linear with bias fields larger than 2.5 kV/mm. Additionally, after a step increase of the electric field, the transient current changes sign and is opposite to the applied field. These two properties rule out electrochemical effects as well as carrier trapping/de-trapping as the source of the negative dielectric constant. More importantly, this latter feature verifies that the static dielectric function, $\varepsilon $'(k,$\omega $=0), is negative. Furthermore, measurements on cold pressed (solid) pellets of the nanoparticles demonstrate that the effect is not due to rearrangement or large scale motion of the particles. In fact, the data suggests that the negative static $\varepsilon $' is correlated to the interfacial conductivity of the nanoparticles. [Preview Abstract] |
Monday, March 13, 2006 5:06PM - 5:18PM |
D16.00012: Scaling Behavior of Dielectric Switching in Nano-assemblies Feng Chen, Jason Shulman, Stephen Tsui, Yuyi Xue, C. W. Chu Recently, we have reported a field-induced sign-switch of dielectric constant ($\varepsilon $') for urea-coated Ba$_{0.8}$Rb$_{0.4}$Ti$_{O}$(C$_{2}$O$_{4})_{2}$ nano-particles (U-BRTOCO) in silicone oil and demonstrated that the observed negative $\varepsilon $' is an intrinsic property of the nano-particle assemblies A systematic study has been subsequently carried out on the switching of $\varepsilon $' under a bias field for U-BRTOCO and other nano-particle assemblies under different conditions. The switching frequency ($\omega _{c})$ is found to be closely related to the zero-frequency electrical conductivity ($\sigma $(0)) of the assemblies. Such a scaling behavior for different nano-assemblies under various conditions gives us strong insight of the origin of the negative $\varepsilon $'. The possible models such as plasma and 2D electron-gas (2DEG) are compared. [Preview Abstract] |
Monday, March 13, 2006 5:18PM - 5:30PM |
D16.00013: Magnetic resonances in nano-scale metamaterials Zhao Hao, Alex Liddle, Michael Martin We have designed, fabricated, and optically measured several different kinds of nano-scale metamaterials. We make use e-beam nano-lithography technology at LBNL's Center for X-Ray Optics for fabricating these structures on extremely thin SiN substrates so that they are close to free-standing. Optical properties were measured as a function of incidence angle and polarization. We directly observe a strong magnetic resonance consistent with a negative magnetic permeability in our samples at mid- and near-IR optical frequencies. We will discuss the results in comparison with detailed simulations, and will discuss the electric dipole or quadrupole resonances observed in the samples. Finally, we will report on our progress towards constructing a fully negative index of refraction meta-material. [Preview Abstract] |
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