Rampi Ramprasad University of Connecticut
John Page University of Manitoba
Philippe Renaud Freescale Semiconductor
Pawitter Mangat Motorola, Inc.
R1: Negative Index Meta-Materials I
Tuesday AM, November 28, 2006
Room 313 (Hynes)
9:30 AM - **R1.1
A Practical Route to Achieving a 2D True NIM at Mid-IR Frequencies.
Sheldon Schultz 1 , David Vier 1 , Aleksandar Simic 1 Show Abstract
1 Physics, University California San Diego, La Jolla, California, United States
We will give a brief review of the required characteristics for a true Negative Index of refraction Metamaterial (NIM). We present the design, fabrication, and confirmation process for a 2D multilayer NIM comprised without any conducting materials that can have index n=-1, and the relative surface impedance Z/Zo=+1 at a Mid IR frequency. The design is applicable for operation at lower frequencies by the appropriate choice of materials.
10:00 AM - **R1.2
Negative Refractive Index of Meta-materials at Optical Frequencies.
S. Anantha Ramakrishna 1 , S. Chakrabarti 1 Show Abstract
1 Physics, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh, India
Scaling the performance of metamaterials to obtain negative refractive index at optical frequencies has been of great interest. One of the great barriers to the scaling is that real currents cannot be driven at very high frequencies and one is more dependent on displacement currents to generate negative magnetic permeability. Moreover to keep the dimensions of the metamaterials physically accessible, the structural lengthscales of the metamaterials begin approach the wavelength of the radiation in free space and homogenisation is often questionable. Here we will show that metamaterials such as Split ring resonators in these high frequency limits exhibit complex behaviour. Magnetic activity and Negative refractive index behaviour can, indeed, be obtained at optical frequencies but will need to be intepreted very carefully. The plasmonic nature of the metallic system and excitation needs to be considered in detail.
10:30 AM - R1.3
Meta-structure at Sub-10 micron IR Range Using Nanoimprint Lithography
Evgenia Kim 1 , Yongmin Liu 1 , Wei Wu 2 , Zhaoning Yu 2 , Shih-Yuan Wang 2 , Xiang Zhang 1 , Yuen Ron Shen 1 Show Abstract
1 Physics, UCB, Berkeley, California, United States, 2 , Hewlett-Packard Company, Palo-Alto, California, United States
Artificial magnetic resonance based on split-ring resonators (SRRs) recently has attracted intensive research interest, because it could implement negative permeability unobtainable in natural materials. However, traditional SRRs possess strong bianisotrsopy, which is not desired for constructing isotropic negative-index materials (NIMs). We have designed a novel resonator consisting of four isolated L-shaped arms to form an open loop. The L-shaped resonator (LSR) has four-fold rotational symmetry, which can suppress electric-field induced resonance, therefore it is more isotropic compared with SRR. The designed LSR with 45nm feature size can achieve effective permeability of -0.5 at 5um wavelength.There are two major steps in the meta-structure fabrication, the nanoimprint lithography (NIL) mold fabrication and the device fabrication. The NIL mold fabrication process is consist of two steps, first, the Si master mold fabrication using electron-beam lithography (EBL) and reactive ion etching (RIE); second, the transparent daughter mold fabrication using NIL, lift-off and RIE. The transparent NIL mold is needed in the device fabrication using UV-curable NIL, however, it is much harder to do high resolution EBL on a transparent substrate directly, such as glass, due to charging effect. Hence we chose the two-steps mold making processes to do EBL on a Si substrate first and transfer the patterns onto the transparent mold substrate later. We have studied the same LSRs on three different substrates: (i) silicon, (ii) silicon + 300nm of Si3N4, (iii) 300nm suspended film of Si3N4. The results from different substrates can provide information on how the refractive index of the substrate influences the magnetic and plasmon resonances. The reflection spectrum with p-in p-out polarization combination from the nanoimprinted LSRs on the Si3N4 substrate is revealed a sharp reflection peak resulting from negative permeability due to plasmon resonance of LSRs, which is clearly observed at 3.7±0.05 um wavelength. It agrees well with the simulation. The reflection spectra of LSRs on Si3N4 substrate, LSRs on Si+ Si3N4 substrate and LSRs on Si substrate are revealed red-shift of the peak and increase of peak amplitude with an overall decrease of refractive index of the substrate. (n~3.73 for Si and n~2 for Si3N4.) This behavior is expected from the dependence of local plasmon resonance of metal nanostructure on the permeability of the substrate. In our measurements, the input beam was incident on the sample at 70o from the surface normal. To access the magnetic response of LSRs, we used s-in s-out polarization combination. In addition to the peak at 3.7 um due to plasmon resonance, another peak is observed at 5.25±0.05 um wavelength, due to the magnetic resonance. As expected, both peaks are sharper, stronger, and red-shifted with a substrate of smaller refractive index. In this respect, Si3N4 is clearly the best among the three we have investigated.
10:45 AM - R1.4
Development of Low-loss Metamaterials Utilizing Dielectric Resonators
Elena Semouchkina 1 , George Semouchkin 1 , Michael Lanagan 1 Show Abstract
1 , Penn State University, University Park, Pennsylvania, United States
Artificial materials created by embedding inhomogenities periodically in a host matrix can generate qualitatively new electromagnetic responses that do not occur in nature. Unusual properties of metamaterials offer enormous potential for advanced applications in the mm-wave, THz and optical frequency ranges. “Conventional” metamaterials consisting of arrays of microstrip split-ring resonators (SRRs) and wires have been extensively investigated in the past. It was demonstrated that these metamaterials could exhibit a negative refractive index in a certain frequency range. However, “conventional” metamaterials have proven to be lossy at high frequencies due to the skin effect in metal inclusions. These inclusions also create discontinuities for wave propagation that reduce transmission to impractical levels. Another problem with these structures is anisotropy, since SRRs support only dipole-like resonance modes with fixed axial orientation in space. Efforts undertaken to decrease anisotropy and create 3D materials by using metal inclusions of more complicated designs have led to accentuated discontinuities and losses. Our theoretical and experimental studies have shown that negative index materials could be created from structural units different from ones of “conventional” metamaterials. These results have opened up a way for utilizing various types of resonators for creation negative index materials. We present a new metamaterial, which employs a periodic array of high-permittivity dielectric resonators (DRs) embedded into lower-permittivity matrix instead of SRRs and wire arrays. The new metamaterial potentially is 3D, isotropic and has low loss. High permittivity DRs are linked together in the periodic structure and become electromagnetically coupled under resonant conditions. The interplay between local resonator mode symmetry and global lattice symmetry provides for intriguing properties, such as negative refraction and formation of electric and magnetic laminar superstructures. The latter property could be potentially used for realization magnetic and electric properties of all-dielectric metamaterials at high frequencies, at which natural ferromagnetics and ferroelectrics have high loss. We demonstrate that the transmission mechanism in the novel resonant dielectric structures is different from one in the photonic bandgap crystals, and is defined by resonance wave propagation.Metamaterial prototypes for microwave frequency range have been fabricated by using low temperature co-fired ceramics technology. Our current studies are focused on investigation of 3D combinations of DRs of different shapes, dimensions, and materials and on extension of their operation range up to far infrared region.
11:30 AM - **R1.5
A Volumetric Negative-Refractive-Index Transmission-Line (NRI-TL) Metamaterial For Incident Waves From Free-Space.
George Eleftheriades 1 , Ashwin Iyer 1 Show Abstract
1 Electrical and Computer Engineering, University of Toronto, Toronto, Ontario, Canada
12:00 PM - R1.6
A Systematic Approach to the Design and Analysis of 1-D, Two-Port Metamaterial Lattices.
Michael Petras 1 , Rashaunda Henderson 1 , Sushil Bharatan 1 , Walter Parmon 1 Show Abstract
1 , Freescale Semiconductor Inc., Tempe, Arizona, United States
Two-port transmission lines (TMLs) provide an excellent framework for studying the electromagnetic properties of 1-D metamaterial systems. They are easy to construct using standard semiconductor or printed circuit board processes, are relatively easy to measure and characterize, and can be accurately described theoretically using well-established distributed circuit models. A typical metamaterial TML consists of a basic microstrip or coplanar transmission line that is periodically loaded with simple lumped passive elements (e.g. inductors, capacitors, and resistors), and operated at frequencies where the electromagnetic (EM) wavelength is much smaller than the spacing between repeat units. However, although simple in concept, the design flexibility available using TML constructions can quickly lead to very complex lattices, making it difficult to realize an efficient design for a given set of requirements. This problem is made even more difficult for inhomogeneous lattices, where changes are made to one or more repeat units, or “super” lattices where several levels of nested sub-lattices are used in combination. To address this complexity issue, a systematic method for classifying and characterizing two-port TML lattices was developed. Using this approach, a “periodic table” of TML lattices easily realizable in any multilevel metal/dielectric process was constructed. Each cell in the table links a particular lattice’s electrical construction to its fundamental performance characteristics, i.e. the transmission spectrum, characteristic impedance spectrum, and w-k diagram. The table facilitates rapid identification of the lattice constructions best suited for a given application, and can be used like a periodic table to combine lattices to generate more complex structures. It can also be used in conjunction with computer-based search algorithms to optimize the performance of large metamaterial networks.
12:15 PM - R1.7
Realization of Planar Infrared Negative Index Metamaterials through Genetic Algorithm Optimization of Frequency Selective Surfaces
Yan Tang 1 2 , Jeremy Bossard 1 2 , Mark Gingrich 1 , Jacob Smith 1 , Theresa Mayer 1 2 , Douglas Werner 1 2 Show Abstract
1 Department of Electrical Engineering, The Pennsylvania State University, University Park, Pennsylvania, United States, 2 Center for Nanoscale Science, The Pennsylvania University, University Park, Pennsylvania, United States
In this talk, we will present a new design strategy for synthesis of negative index metamaterials (NIMs) that employs a robust genetic algorithm (GA) technique to optimize the geometrical configuration and material properties of metallodielectric frequency selective surfaces (FSSs). This approach allows the metamaterial structure of the FSS to achieve a target value of negative refractive index (e.g., nr = -1) with minimum dielectric and reflection loss, as well as to satisfy fabrication constraints. Our infrared NIM design is comprised of a 2D periodic metallic pattern (75nm-thick silver) with a unit cell size of 2.5×2.5 μm2 sandwiched between two flexible dielectric films (3.25μm-thick polyimide), and was fabricated by electron beam lithography. The effective refractive index of the fabricated NIM was inverted from the transmission and reflection coefficients, measured with Fourier Transform Infrared Spectroscopy (FTIR). Both the real (nr = -1.3) and imaginary (ni ≈ 0) parts of the refractive index show excellent agreement with the theoretical prediction. The optimized structure has a loss of only 0.1dB at a wavelength of 20μm, which represents an improvement of more than two orders of magnitude compared to other reported NIM designs operating in the infrared. Another important objective of the GA was to minimize the reflection loss of the NIM due to any impedance mismatch that might occur at the surface. The goal-oriented feed forward design strategy in combination with the straightforward fabrication process presented in this work represents a significant step towards the engineering of high-quality NIMs for use in applications such as perfect lenses.
12:30 PM - R1.8
Enhancement of Plasmon Propagation Length Using Metamaterials.
David McNeil 1 , Arkady Krokhin 1 , Arup Neogi 1 Show Abstract
1 , University of North Texas, Denton, Texas, United States
The efficiency of the plasmonic and resolution of the near-field optical devices is determined by the propagation range of the surface plasmon (SP) – surface mode, which exist at the metal-dielectric interface. The decay of the SP is mainly due to Joule losses in the metal film, reducible by cooling. We propose an alternative method which is more practical.Electromagnetic dissipation in metal is determined by the scalar product j.E, both vectors having longitudinal and transverse components. The relation between these components is affected by the properties of the dielectric substrate. Joule losses may be essentially reduced if the substrate possesses strong optical anisotropy. The dissipation can be minimized by correct orientation of the substrate’s optical axis with respect to the metal surface. The substrate is considered to be a uniaxial crystal with its axis perpendicular to the metal surface. The dielectric constants of the substrate are ε1 (in the propagation plane) and ε2 (in the perpendicular direction). The metal film is characterized by a complex dielectric tensor with isotropic negative real part ε’(ω) and anisotropic positive imaginary part εik”(ω). The later has parallel and perpendicular components. Anisotropy of the dissipative part of the dielectric tensor is due to the surface channel of electron scattering, leading to the lower AC conductivity of the thin film in the direction perpendicular to the metal surfaces. The substrate with ε2>ε1 gives rise to larger propagation length of the SP. Thus anisotropic negative uniaxial crystals are preferential.Analysis of anisotropic optical crystals shows that enhancement of the propagation length occurs if the axis of the highest value of the dielectric tensor is parallel to the metal-dielectric interface. If the substrate is a positive (negative) uniaxial crystal, the longest propagation occurs if the optical axis is parallel (perpendicular) to the interface. Optical anisotropy in natural crystals is quite weak and insufficient to provide a noticeable increase in propagation range. However, artificial semiconductor structures, photonic crystals (PCs), do have the necessary degree of anisotropy. In the long-wavelength limit, PCs behave like homogeneous anisotropic mediums. 1D crystals (superlattices) exhibit negative birefringence, therefore the axis of the crystal has to be oriented perpendicular to the interface. However, 2D PCs behaves like a positive uniaxial crystal. Therefore the substrate of 2D PCs provides the longest propagation length in the case when the optical axis (the cylinders) is parallel to the interface.Application of anisotropic substrates has one more important advantage. For the same orientation of the optical axis that provides the longest propagation length, the penetration depth of the electromagnetic field into the substrate turns out to be the largest. The penetration depth determines the number of parallel layers integrated in optoelectronic devices.
12:45 PM - R1.9
Screen Printed Frequency-Selective Surfaces on Rigid, Flexible and Elastic Substrates
Thomas Kistenmacher 1 , Arthur Francomacaro 1 , Benjamin Brawley 1 , Raid Awadallah 1 , Paul Vichot 1 , Michael Fitch 1 , Jane Spicer 1 , Dennis Wickenden 1 Show Abstract
1 Applied Physics, Johns Hopkins University, Laurel, Maryland, United States
Two-dimensional arrays of nested square and triangular split-ring resonators (SRRs) have been fabricated by screen printing silver-filled polymer-thick-film (PTF) paste on flexible polymeric (PI and PET) and elastic (silicone) substrates. In order to maximize the resolution and edge acuity of the resonators, a high performance screen from IRI International was utilized. The silk screen was 400 mesh, derived from 28 µm stainless steel wire strung at 45 degrees and coated with a pre-sensitized 8 µm thick HP emulsion. Typically, the final line thickness of the cured resonators was on the order of 5 - 6 µm. The microwave transmission of these resonator arrays was measured using an Agilent PNA-N5230A network analyzer with two Condor Systems AS-48461, 2-18 GHz horn antennas connected on the transmit and receive ports. A 0.9 by 0.9 m wall of pyramidal absorber, with a 12.7 by 12.7 cm cutout for the sample, was placed between the two horn antennas. Two 17.8 by 17.8 cm Plexiglas frames, each with the same 12.7 by 12.7 cutout for the sample, and 4 plastic screws were used to hold the arrays on flexible and elastic substrates. The transmit horn antenna was placed 1.5 m from the absorber wall, while the receive antenna was placed 0.6 m from the wall. This spacing was optimized to establish a far-field transmit pattern with nominal phase variation, while minimizing diffractive spillover from the edges of the absorbing wall. Time-gating was used to isolate the signal-of-interest from any interfering signals. All signals were referenced to the signal obtained with vertically polarized transmit and receive horns with the sample removed from the beam. Screen-printed arrays were compared to SRR arrays fabricated on 34 µm-thick-Cu-coated FR4 boards. For these Cu-based arrays, the observed frequencies, 9.3 and 9.6 GHz, and quality factors (Qs), 68 and 62, are typical of highly conductive split-square and split-triangle resonator arrays. Arrays produced by screen-printing silver-filled PTF paste on FR4 boards exhibit small downward shifts in the resonance frequency (~ 0.5 GHz), and the expected loss in Q (on the order of 50%) is attributed to insertion losses following from the increased resistivity of the silver-filled PTF paste.The screen-printed arrays on the lower dielectric flexible and elastic substrates exhibit transmission minima in the 10 - 12 GHz range and Qs of 26 - 34 for the flexible polymers and 14 - 17 for resonator arrays on elastic silicone substrates. In spite of the limited Qs, screen-printed resonator arrays offer considerable potential as components in flexible and conformal microwave devices.
R2: Negative Index Meta-Materials II
Tuesday PM, November 28, 2006
Room 313 (Hynes)
2:30 PM - **R2.1
Empowering Metamaterials: From Low to No-loss and From Linear to Nonlinear Optics.
Vladimir Shalaev 1 , A. Kildishev 1 , V. Drachev 1 , A. Popov 2 , T. Klar 3 Show Abstract
1 School of Electrical & Computer Engineering, Purdue University, West Lafayette, Indiana, United States, 2 Physics Department, University of Wisconsin at Stevens Point, Stevens Point, Wisconsin, United States, 3 Fakultät für Physik, Ludwig-Maximilians-Universität, München Germany
In this presentation we review recent progress in optical negative-index materials (NIMs). Practical optical negative index materials based on coupled plasmon resonances must overcome reflection and absorption. We show that matched impedance and compensated losses due to optimized design and gain material can lead to 100% transmission. The extraordinary nonlinear optical properties of NIMs will be also discussed.
3:00 PM - **R2.2
Nano-Scale Resonant Metamaterial-Based Radiating And Scattering Systems.
Richard Ziolowski 1 Show Abstract
1 Electrical and Computer Engineering, University of Arizona, Tucson, Arizona, United States
3:30 PM - R2.3
Magnetic, Electric and Magneto-Optical Metamaterials at THz Frequencies
Willie Padilla 1 , Marie Aronsson 2 , Houtong Chen 3 , A. Taylor 3 , Richard Averitt 3 Show Abstract
1 Physics, Boston College, Chestnuthill, Massachusetts, United States, 2 ISR-HPE, Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 3 MPA-CIN, Los Alamos National Laboratory, Los Alamos, New Mexico, United States
3:45 PM - R2.4
Negative Index Metamaterials with Deeply Subwavelength Structural Dimensions from Near Infrared to Visible Based on Thin Films.
Vitaliy Lomakin 1 , Yeshaiahu Fainman 1 , Gennady Shvets 2 Show Abstract
1 Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, United States, 2 Department of Physics, University of Texas, Austin, Austin, Texas, United States
4:30 PM - **R2.5
Imaging and Negative Refraction by Left-handed Metamaterials.
Srinivas Sridhar 1 , Wentao Lu 1 , Plarenta Vodo 1 , Patanjali Parimi 1 , Yongjian Huang 1 , Ravi Banyal 1 Show Abstract
1 Electronic Materials Research Institute and Department of Physics, Northeastern University, Boston, Massachusetts, United States
5:00 PM - **R2.6
Photonic Crystal Lens.
Stefan Enoch 1 , Boris Gralak 1 , Raphael Pierre 1 , Gerard Tayeb 1 , Daniel Maystre 1 , Thibault Decoopman 1 Show Abstract
1 , Institut Fresnel CNRS, Marseille France
5:30 PM - R2.7
Negative Refraction in the Visible: Direct Evidence of Left-Handed Behavior in Metal-Dielectric-Metal Waveguides.
Henri Lezec 1 2 , Jennifer Dionne 1 , Harry Atwater 1 Show Abstract
1 Thomas J. Watson Laboratories of Applied Physics, California Institute of Technology, Pasadena, California, United States, 2 , CNRS, Paris France
Left-handed (LH) materials are defined by a dielectric permittivity ε and magnetic permeability μ that are both negative, resulting in a negative index of refraction n. Here we report on the first direct experimental observation at visible wavelengths of negative refraction at the interface between a left-handed and right-handed material. The structures we have used to implement negative refraction are inspired by recent theoretical predictions of LH behavior in planar plasmonic waveguides [1,2,3]. More specifically, these structures consist of ultra-thin Au-Si3N4-Ag waveguides (dielectric core thickness ~50nm) which are able to sustain a coupled surface-plasmon mode with negative group velocity over a wide wavelength range in the visible (470nm < λ < 530nm). Planar triangular sections of such waveguides (region 1, index n1) are fabricated in series with thicker Ag-Si3N4-Ag waveguides (region 2, index n2) predicted to sustain propagation of a photonic mode with positive group velocity and standard right-handed behavior. By measuring the in-plane angle of refraction of a guided plane wave as it crosses the interface separating regions 1 and 2, unequivocal evidence of negative refraction is observed at certain wavelengths. For example, for an incident angle of θ1=+7° with respect to the interface normal, transmitted angles with respect to the normal of θ2 =-51° and -54° are obtained at λ=514nm and 488nm, respectively. Applying Snell’s law (and solving Maxwell’s equations in region 2 to determine n2), yields an effective negative index of refraction for region 1 of n1=-4.3 and -6.6, at λ=514nm and 488nm, respectively. For wavelengths outside the interval of negative group velocity for region 1, standard positive refraction is observed (θ2=+38° at λ=685nm for example). This path to achieving negative refraction in the visible, along with predicted phenomena such as subwavelength image formation, appears particularly promising since it circumvents the difficulty of fabricating resonant elements with lateral dimensions far smaller than optical wavelengths, such as would be required in a more traditional approach . A. Alu and N. Engheta, J.Opt. Soc. Am. B 23 571 (2006). G. Shvets, Phys. Rev. B 67 35109 (2003). H. Shin and S. Fan, Phys. Rev. Lett. 96 73907 (2006). R.A. Shelby, D.R. Smith and S. Schultz, Science 292 77 (2001).
5:45 PM - R2.8
Imaging of Quantum Dots Fluorescence in Opal/Inverted Opal Photonic Crystals: Search for Negative Refraction Focusing
Anvar Zakhidov 1 , Stacey McLeroy 1 , Ali Aliev 1 , Rocio Lara 1 Show Abstract
1 Physics, University of Texas at Dallas, Richardson, Texas, United States
Fluorescence of CdS and CdSe quantum dots (QD) impregnated into porous silica and polysterene opal photonic crystals have been compared for QDs of different sizes. Spatial distribution of light is visualized by confocal fluorescent microscopy for QDs emitting in blue, green and red spectral bands and compared for photonic crystals having photonic band gaps in different spectral bands. It is found that spatial distribution of fluorescence emission from single QDs and small aggregates of QD is significantly different for QD with fluorescent lines below, within and above PBG frequency in  direction.We discuss these different spatial fluorescent patterns in terms of negative refraction in upper photonic bands, which have negative group velocity. The light from QDs in the upper band creates patterns, which we interpret as focusing by the interface between media with positive and negative refraction. We analyze the fluorescence patterns of same size QD in inverted opals, and opals with strong disordering. Comparing those patterns with earlier obtained images of QDs in direct opal PC allows to understand the microscopic paths of light propagation from QD point sources inside photonic crystals.
R3: Poster Session: Meta-Material
Tuesday PM, November 28, 2006
Exhibition Hall D (Hynes)
9:00 PM - R3.1
Integration of Metallic Nanorod Arrays onto Optical Fibers
Elizabeth Smythe 1 , Ertugrul Cubukcu 1 , Kenneth Crozier 1 , Federico Capasso 1 Show Abstract
1 DEAS, Harvard University, Cambridge, Massachusetts, United States
We have successfully integrated periodic arrays of strongly coupled metallic nanorod antennas on the facet of an optical fiber. Our structures can be used for chemical and biological sensing and detection by utilizing surface enhanced Raman spectroscopy. Nanorod arrays provide high average electromagnetic field enhancement over a large area, as opposed to a few localized ‘hot spots’ as found in disordered metal-dielectric films. The integration of antenna arrays on a fiber can potentially eliminate the need for bulkier conventional detection systems by providing a robust, portable system that allows for easy ‘probing’ of various chemical and biological samples. Our optical antenna arrays are modeled using finite difference time domain method. The fiber mode that is incident on the structure is represented by a plane wave interacting with our antenna array. Since our structures are periodic in nature they can be represented by a single computational unit cell. This allows us to use periodic boundary conditions for computing the resonances of the arrays. Our calculations indicate an average field enhancement factor = |Eloc(λ)/Eo(λ)|4 on the order of 105. Antenna arrays are initially fabricated on indium tin oxide coated glass slides using electron beam lithography and standard lift-off processes. This facilitates in characterization of our fabricated structures, as the optical properties of thin gold films depends on their evaporation conditions. Our gold is deposited using electron beam evaporation. The characterization of our arrays on glass slides is done by taking reflection measurements. Once the desired antenna array parameters are determined, the arrays are fabricated on the facet of an optical fiber (directly over its core) using a focused ion beam. The non-altered end of the fiber is then connectorized to allow for easy integration to standard lasers and other commercial light sources. Measured reflection data from our arrays on slides show that the antenna resonances can have a full width half max of on the order of 150nm. We are able to tune the resonances of our on-slide arrays by changing the antenna geometry and their periodicity. Arrays of a ‘short’ nanorod length and set spacing exhibit peak resonances that are blue-shifted from those of ‘long’ lengths with the same spacing. With the same rod-to-rod spacing, antennas that are 100nm in length exhibit a peak in resonance that is blue-shifted by 75nm from those that are 140nm in length. When rods become more separated along their lengths they also exhibit blue-shifted spectra. Our measurements were done for light polarized along the length of the rod. Light polarized perpendicular to the rods should also exhibit resonances, but we are unable to measure these as they are out of the range of our light source and detectors (λ=600-1000nm). Our reflection measurements of this polarization confirm that no enhancement is occurring in our range of detection and measurement.
9:00 PM - R3.10
Non-coupling Bands in Photonic Crystals as Origin for Negative Refraction Effect.
Andreas von Rhein 1 , Daniel Pergande 1 , Siegmund Greulich-Weber 1 , Ralf Wehrspohn 1 Show Abstract
1 Department of Physics, University of Paderborn, Paderborn Germany
9:00 PM - R3.12
3D Silicon Opal
Marva Royer 1 , Ali Aliev 1 , Anvar Zakhidov 1 , Ray Baughman 1 Show Abstract
1 NanoTech Institute, University of Texas at Dallas, Richardson, Texas, United States
9:00 PM - R3.13
P Surface Crystal with a Complete Photonic Band Gap via Interference Lithography and Infiltration
Ji-Hyun Jang 1 , Chaitanya Ullal 1 , Martin Maldovan 1 , CheongYang Koh 1 , Steven Kooi 1 , Edwin Thomas 1 Show Abstract
1 , MIT, Cambridge, Massachusetts, United States
Interference lithography (IL) has been recently proposed as efficient and flexible technique for fabrication of photonic crystals. Diamond based structures, which have been predicted to possess the largest photonic band gaps to date, have unfavorable process conditions via interference lithography for integrated optics platforms since the beams do not all come from the same half space. On the other hand, the P structure has been suggested as an accessible alternative photonic lattice with a 13 % complete band gap at a volume fraction of 0.26 and dielectric contrast of 3.6:1. Importantly, the P lattice is size scalable without need to change the wavelength of the exposing light. Here we report on the fabrication and optical properties of simple cubic lattices fabricated by interference lithography. Polymeric templates with simple cubic symmetry are patterned by exposing negative photoresist to the periodic intensity distribution formed by the interference of six beams of light. Refraction is compensated for by the use of a prism. The polymeric template is then infiltrated with high refractive index materials such as TiO2 and removed by sintering. These structures show large photonic band gaps in the infrared region.
9:00 PM - R3.14
Dielectrophoretic Assembly of Grain-Boundary-Free 2D Colloidal Single Crystals
Sejong Kim 1 , Ramazan Asmatulu 2 , Harris Marcus 2 , Fotios Papadimitrakopoulos 1 Show Abstract
1 Nanomaterials Optoelectronics Laboratory, Polymer Program, Institute of Materials Science, University of Connecticut, Storrs, Connecticut, United States, 2 Department of Chemical, Materials and Biomolecular Engineering, Institute of Materials Science, University of Connecticut, Storrs, Connecticut, United States
In this contribution, dielectrophoretic (DEP) force-assisted assembly of colloidal single crystal monolayer in microfluidic chamber was demonstrated. A negative DEP force with high frequency electric field induced compression of colloidal microspheres to form colloidal crystal domain at the center of hexapolar shape electrode. While typical assembly by monotonic DEP compressive force forms multicrystalline domain containing crystal defects, DEP-compression/relaxation-cycle-induced aging process significantly facilitated crystal growth of 10 μm monodispersed polystyrene microsphere, allowing grain boundary-free single crystalline monolayer domain of c.a. 200 μm size. Microsphere size as well as size distribution affected the formation of such a single crystalline domain. Utilizing a non-ionic polymeric binder, such a single crystalline domain was successfully immobilized onto the glass substrate without loosing its long-range order.
9:00 PM - R3.15
Magnetic Opals: 3D Magnetophotonic Crystals as new Materials for Nonlinear Magneto-Optics
Oleg Aktsipetrov 1 , Tatyana Murzina 1 , Ruslan Kapra 1 , Evgeniya Kim 1 , Dmitrii Kurdyukov 2 , Savelii Kaplan 2 , Valerii Golubev 2 , Mitsuteru Inoue 3 Show Abstract
1 Department of Physics, Moscow State University, Moscow Russian Federation, 2 , Ioffe Physico-Technical Institute, St. Petersburg Russian Federation, 3 , Toyohashi University of Technology, Toyohashi Japan
9:00 PM - R3.16
Nonlinear Optical Properties of Surface Immobilized Gold Nanospheres above a gold Surface with Nanogap.
Kazuma Tsuboi 2 , Kotaro Kajikawa 1 2 Show Abstract
2 PRESTO, JST, Saitama Japan, 1 Department of Electronics and Applied Physics, Tokyo Institute of Technology, Yokohama Japan
Linear and nonlinear optical properties are investigated for surface immobilized gold nanospheres (SIGNs) above a gold surface with a gap distance of a few nanometers. The nanogap was supported by self-assembled monolayers (SAMs) of alkanethiolates. A large second harmonic generation (SHG) was observed from the SIGN systems at localized surface plasmon resonance condition. The maximum enhancement factor of SHG intensity was found to be 300000 for the SIGN system of nanospheres 100 nm in diameter with a gap distance of 0.8 nm. The corresponding susceptibility was estimated to be 750 pm/V (1.8x10(-6) esu). It was found that the SHG response of the SIGN systems is strongly frequency dependent, suggesting that the large second order susceptibility is caused by enhanced electric fields at the LSP resonance condition, and is not due to an increase of the surface susceptibility following from the presence of the gold nanospheres. The observed SHG was consistent with the theoretical calculations involving Fresnel correction factors, based on the quasi-static approximation.
9:00 PM - R3.17
Synthesis and Optical Properties of Gold Nanoparticles with Complex Shapes
Colleen Nehl 1 4 , Britt Lassiter 1 4 , Hui Wang 2 4 , Hongwei Liao 2 4 , Yanpeng Wu 1 4 , Peter Nordlander 1 3 4 , Naomi Halas 2 3 4 , Jason Hafner 1 2 4 Show Abstract
1 Physics, Rice University, Houston, Texas, United States, 4 Laboratory for Nanophotonics, Rice University, Houston, Texas, United States, 2 Chemistry, Rice University, Houston, Texas, United States, 3 Electrical and Computer Engineering, Rice University, Houston, Texas, United States
Manipulation of electromagnetic wave propagation with meta-materials often requires the fabrication and characterization of optical materials with complex shapes. At visible wavelengths, nanometer scale control is required. Here we will describe our efforts in the synthesis and fabrication of gold nanoparticles with complex shapes and their characterization by single particle spectroscopy. Star-shaped gold nanoparticles which are ca. 100 nm in diameter have been synthesized by seed-mediated, surfactant directed synthesis. The yield, monodispersity, and initial investigations into the growth mechanism of the synthesis will be described. Nanoshells with an offset core have also been fabricated and investigated. The reduced symmetry of nanoshells with offset cores creates a multipeaked spectrum dependent on the core offset. We have also studied controlled aggregate nanostructures, such as nanoshell homo- and heterodimers. Because these nanoparticles have highly complex shapes and are not completely monodisperse, single particle spectroscopy has been used to investigate the scattering spectra of individual nanoparticles. Correlation of the polarized scattering spectra with high resolution electron microscopy of the same nanoparticle reveals that many of these nanoparticles have multiple visible and near-infrared plasmon resonances which correspond to the particle structure and geometry.
9:00 PM - R3.18
Thermo-optical Properties of Nanoparticles and Nanoparticle Complexes Embedded in Ice: Characterization of Heat Generation and Actuation of Larger-scale Effects.
Hugh Richardson 1 , Zachary Hickman 1 , Alyssa Thomas 1 , Martin Kordesch 2 , Alexander Govorov 2 Show Abstract
1 Chemistry and Biochemistry, Ohio University, Athens, Ohio, United States, 2 Physics and Astronomy, Ohio University, Athens, Ohio, United States
We have investigated the thermo-optical properties of gold NPs embedded in an ice matrix . Resonant laser light of relatively weak intensity is able to melt ice with embedded Au NPs, whereas even a very intense laser beam does not melt ice alone. This comes from strong absorption in Au NPs in the regime of plasmon resonance. By recording time-resolved Raman signals, we observe the melting process and determine the threshold melting power, Pmelting (T), where T is the background temperature. We also observe relatively large scattering in the threshold laser intensity that leads to melting of the ice because of the mesoscopic nature of the sample. We can understand this observation using the TEM images of NPs, showing that geometry of NP complexes varies greatly. In our recent theoretical paper we showed that the local temperature inside and around a NP complex depends strongly on its geometry, and this leads to large scattering for the measured as a function of the reduced temperature, for different complexes . We recently discovered that NPs immobilized on glass surfaces can be characterized by single particle spectroscopy. Single and small NP clusters can be discriminated using the integrated intensity of the plasmon emission band. A cluster of four gold NPs has ~ 4 times the intensity of a single gold NP. When the NPs are aggregated into a single cluster then broadening of the intensity profile plot is not observed In contrast, gold NPs that are not clustered together but are located within the excitation volume will lead to a broadening of a cross sectional slice spectrum from the intensity profile plot. We will use these principles to determine the amount of heat generation from single(clustered)gold NP(s) and NP complexes.  H. H. Richardson, Z. N. Hickman, A. O. Govorov, A. C. Thomas, W. Zhang, M. E. Kordesch, Nano Lett. (2006); DOI: 10.1021/ nl060105l.  A. O. Govorov, H. H. Richardson, W. Zhang, and T. Skeini, Nanoscale Res. Lett. 1, 100101 (2005).
9:00 PM - R3.19
Single-Step Synthesis of Metal/Porous Support Nanocomposites.
Jayashri Sarkar 1 , Arijit Bose 1 , Ramanath Ganapathiraman 2 , Vijay John 3 Show Abstract
1 Department of Chemical Engineering, University of Rhode Island, Kingston, Rhode Island, United States, 2 Department of Materials Science & Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States, 3 Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana, United States
A bicontinuous phase formed by adding water to an isooctane solution containing the two surfactants AOT and lecithin was used as a template for the synthesis of gold/porous silica and platinum/porous titania nanocomposites. The mechanism of synthesis was by simultaneous hydrolysis/condensation of the support precursor (TMOS - Tetramethyl orthosilicate and TIP- Titanium isopropoxide), present in the oil phase along with reduction of the metal precursor (HAuCl4 or PtCl4) in the aqueous phase. The high viscosity of this multi-component system immobilized metallic nanoparticles once they were formed throughout the aqueous domains, thus preventing agglomeration. The TiO2 formed hexagonally arranged highly organized structures at the nanoscale, mimicking the underlying structure of the surfactant system. The pore size can be varied by varying the amount of aqueous phase in the system, while the inter-pore distance can be varied by changing the concentration of the support precursor. Pore size, specific surface area, as well as nanoparticle loading could be controlled using this technique. Highly facetted and size tunable gold nanoparticles were also synthesized in situ in the same system. This was achieved without adding additional reducing agents. The surfactants donate electrons, reduce the metal ions and also adsorb onto preferred planes of the growing nanocrystal, adjusting the growth rates and leading to hexagonal and triangular plates with dimensions of the order of microns, but thickness of a few nanometers. These experiments provide a new pathway for the formation of catalyst-support composite materials with well-dispersed metal nanoparticles inside the support material, as well as a robust technique for producing nanoparticles of highly controlled morphology.
9:00 PM - R3.2
Experimental Demonstration of Sub-wavelength Focusing and Negative Refraction of Electromagnetic Waves by Labyrinth Based Two-Dimensional Left-handed Metamaterials
Irfan Bulu 1 , Humeyra Caglayan 1 , Ekmel Ozbay 1 Show Abstract
1 department of physics and nanotechnology research center, bilkent university, Ankara Turkey
9:00 PM - R3.20
Guiding And Confining Light In Nanoporous Cu4O3-C Composite Thin Films.
Mahua Das 1 , Shivashankar Sa 1 Show Abstract
1 Materials Research Centre, Indian Institute of Science, Bangalore, Karnataka, India
Nanoporous Cu4O3 – C composite thin films with spherical and bicontinuous elongated pore structure have been grown on stainless steel substrates by metalorganic chemical vapour deposition technique using a single source tetranuclear metalorganic complex as precursor. The guiding and confinement of light in these quasi-periodic structures have been investigated by glancing incidence (75 degree) infrared spectroscopy at room temperature. The transmittance spectra of these films between wave number 10000 – 400 cm-1 reveal light confinement modes in photonic band gap between 6127- 8839 cm-1 and propagation modes between 5094- 400 cm-1
9:00 PM - R3.21
A Parylene Shadow Mask Technology for Rapid Fabrication and Prototyping of Large Scale Micro and Nano Device Applications
Selvapraba Selvarasah 1 2 , Mehmet Dokmeci 1 2 Show Abstract
1 Electrical and Computer Engineering Department, Northeastern University, Boston, Massachusetts, United States, 2 NSF Center for High-rate Nanomanufacturing (CHN), Northeastern University, Boston, Massachusetts, United States
Selective area deposition using a shadow mask technique has gained great interest in the fields of Micro and Nano Devices. However, the conventional shadow mask techniques have issues with precise deposition due to gaps between the substrate, high pattern flexibility, lack of large area application, complicated processing steps, brittleness of the mask, or reproducibility. We have developed a simple, low cost, robust and High Aspect Ratio (HAR) Parylene Shadow Mask technology for rapid fabrication and prototyping of large scale Micro and Nano Devices and Structures. Parylene (Poly-Para-Xylylene) is a light-weight, stress-free, transparent, inert and a conformal film which does not produce any out-gassing, has a very low permeability to moisture and gases and is very hydrophobic. These extraordinary properties of the Parylene film make it seal very well with the substrate in contact, and prevent contamination or damage to sensitive or fragile components on the substrate. Mechanical alignment is obtained using Supporting Pillar or V-Groove Pyramid structures. The Parylene shadow mask is fabricated using a very simple conventional optical (micro) or e-beam (nano) lithography process and a HAR, low temperature and low pressure Inductively Coupled Plasma (ICP) Reactive Ion Etching procedure. The HAR structure makes the Parylene film reusable, robust and easy to handle. HMDS (HexaMethylDiSilizane) is used as the adhesion promoter and allows one to peel off the films at ease from any surface (silicon or glass). This novel technology can be used to deposit any material of choice, to any shape in the Milli-, Micro- or Nanoscales, by evaporation or by sputter deposition. The detailed technical information and device application will be presented in the paper.
9:00 PM - R3.3
Highly Directive Antennas Based on the SRR Metamaterial Medium
Irfan Bulu 1 , Humeyra Caglayan 1 , Koray Aydin 1 , Ekmel Ozbay 1 Show Abstract
1 department of physics and nanotechnology research center, bilkent university, Ankara Turkey
9:00 PM - R3.4
Design and Fabrication of Periodically Loaded Transmission Line Metamaterial Structures.
Sushil Bharatan 1 , Michael Petras 1 , Rashaunda Henderson 1 , Walter Parmon 1 , Rampi Ramprasad 2 Show Abstract
1 , Freescale Semiconductor Inc., Tempe, Arizona, United States, 2 Department of Materials Science & Engineering, University of Connecticut, Storrs, Connecticut, United States
Periodically loaded transmission lines represent a simple yet practical realization of 1-D metamaterials at frequencies where the electromagnetic (EM) wavelength is much smaller than the spacing between repeat units. We report here on the design and construction of two types of simple lattices that were fabricated using high-density interconnect printed circuit board (HDI) and gallium arsenide (GaAs) integrated passives device (IPD) technologies: (1) transmission lines loaded periodically with shunt elements to ground and (2) transmission lines loaded periodically with elements in cascade. Data is presented for both homogeneous lattices, and lattices with defects, which are modifications made to one or more of the lattice repeat units. These defects are shown to introduce resonances in the transmission spectrum of the parent lattice. EM simulation and a transmission line-based effective medium theory using circuit elements as building blocks both provide accurate descriptions of these systems, and can be used as predictive design tools for lattices and defects. This approach can easily be extended to other types of periodic systems and fabrication technologies.
9:00 PM - R3.5
Circuit Elements at Optical Frequencies: A Synthesis of First Principles Electronic Structure and Circuit Theories.
Chunguang Tang 1 , Rampi Ramprasad 1 Show Abstract
1 Department of Chemical, Materials and Biomolecular Engineering, University of Connecticut, Storrs, Connecticut, United States
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: (1) an ordered composite system consisting of physical nano-elements such as nanowires or nanotubes using density functional theory, and (2) an ordered arrangement of impedances using circuit theory (e.g., 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 have established this mapping for silicon nanowires and carbon nanotubes, both of which can be represented as a series combination of inductance, capacitance and resistance. Once this mapping has been accomplished for a variety of physical systems, and the reasons for the existence of such a mapping well understood, the nano-elements can be combined suitably to result in equivalent circuit topologies appropriate for optical and nanoelectronic devices, including left-handed materials (also referred to as negative refractive index materials).
9:00 PM - R3.6
Low-Refractive-Index Materials: A New Class of Material for Optoelectronic and Photonic Applications
Jingqun Xi 1 , Jong Kyu Kim 2 , E. Fred Schubert 1 2 Show Abstract
1 Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York, United States, 2 Department of Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States
The refractive index contrast in dielectric multilayer structures, optical resonators and photonic crystals is an important figure of merit, which creates a strong demand for a new class of optical thin-film materials with a very low refractive index. Oblique-angle electron-beam deposition of SiO2 with an off-normal vapor incident angle of 85 degree is shown to result in thin films consisting of an array of nano-rods with an extremely low refractive index of only n = 1.08. Scanning electron microscopy reveals a columnar, highly porous structure of the low-refractive-index (low-n) film. The SiO2 nanorods have an approximate diameter of 30 nm and the gap between the SiO2 nanorods is < 50 nm. That is, the feature sizes are smaller than the wavelength of visible light, and thus sufficiently small to limit optical scattering. Optical micrographs of the low-n film SiO2 deposited on a Si substrate reveal a perfectly specular, uniform film with no apparent optical scattering. The unprecedented low refractive index of the low-n SiO2 nano-rod layer is confirmed by both ellipsometry and optical thin-film interference. A single-pair distributed Bragg reflector (DBR) employing a quarter-wave Si layer and a quarter-wave low-n SiO2 nano-rod layer is demonstrated to have higher reflectivity than a DBR employing a quarter-wave Si layer and a quarter-wave dense SiO2 layer. The enhanced optical properties show the great potential of low-n SiO2 films for applications in photonic device structures. An even lower refractive-index of n = 1.05 is obtained by oblique-angle deposition of SiO2 using an off-normal vapor incident angle greater than 85 degree. This is the lowest refractive index ever reported for an optical thin-film material. The gradual change of the refractive index combined with the attainability of refractive indices very close to that of air (n = 1.0) enables omni-directional anti-reflection coatings that have negligible reflectivity over a broad range of angles and wavelengths. This cannot be achieved with conventional anti-reflection coatings which work only at one wavelength and at normal incidence. We will report on graded-index anti-reflection coatings, enabled by the low-n material, with negligible reflection over wide wavelength range, at any incident angle, and for both polarizations (TE and TM). Such anti-reflection coatings with low-n materials are very attractive for solid-state lighting and solar cell applications.
9:00 PM - R3.7
Electromagnetic Responses of Metamaterials at THz Frequencies.
Hou-Tong Chen 1 , Willie Padilla 1 , Johsua Zide 2 , Arthur Gossard 2 , Antoinette Taylor 1 , Richard Averitt 1 Show Abstract
1 MPA-CINT, Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 2 Materials Department, University of California at Santa Barbara, Santa Barbara, California, United States
9:00 PM - R3.8
pH-Controlled Photosynthesis and Surface Assembly of Silver Nanoprisms
Can Xue 1 2 , Chad Mirkin 1 2 Show Abstract
1 Department of Chemistry, Northwestern University, Evanston, Illinois, United States, 2 International Institute for Nanotechnology, Northwestern University, Evanston, Illinois, United States
Silver nanoprisms of uniform size distribution and with tunable plasmon bands that span the visible and NIR range have been synthesized using a novel pH-controlled route. The fusion process of nanoprisms along their edge planes is efficiently inhibited at pH 11.2 due to strong interprism repulsion in basic solution. This allows for the synthesis of silver nanoprisms without a secondary beam, normally required to suppress prism fusion. In contrast, neutral environment (pH 7.4) promotes the nanoprism fusion, leading to high yields of large nanoprisms. These two techniques allow one to tailor the size of the prisms and their corresponding plasmon bands. When the silver nanoprisms are assembled onto amine-functionalized glass substrates, they undergo reversible optical changes while cycled between wet and dry states. This optical phenomenon derives from the dependence of the surface plasmon band on the surrounding dielectric medium changes. A systematic study exhibits an approximately linear relationship between the environmental refractive index and the plasmon extinction wavelength of the silver nanoprism monolayers.
9:00 PM - R3.9
Nondiffractive Propagation through Metal-Dielectric Nanofilm Metamaterial
M. Joseph Roberts 1 , Andrew Guenthner 1 , Geoffrey Lindsay 1 , Simin Feng 1 Show Abstract
1 , NAVAIR NAWCWD, China Lake, California, United States
We report the production and characterization of laterally continuous gold or silver layers alternated with glassy functional polymer films in which the thickness is on the order of 15 nm and 60 nm respectively. When the thickness of each layer is much less than the wavelength, such multilayer structures become metamaterials. Such films exhibit physical phenomena associated with the coupled plasmon resonances and the resonant transmission in the forbidden bands [Laroche, et al. Phys. Rev. B 71, 155113 (2005)]. We have characterized normal light propagation through the resulting metal-dielectric periodic structures using collection mode NSOM. In agreement with published theoretical models [Feng, et al, Optics Express, 13, 4113 (2005)], our experiments confirm that diffraction is suppressed for light propagating through such metamaterials.
Rampi Ramprasad University of Connecticut
John Page University of Manitoba
Philippe Renaud Freescale Semiconductor
Pawitter Mangat Motorola, Inc.
R4: Plasmonics and Nanoscale Meta-Materials
Wednesday AM, November 29, 2006
Room 313 (Hynes)
9:30 AM - **R4.1
Hybrid Localized-Delocalized Plasmonic Systems
Naomi Halas 3 4 1 , Peter Nordlander 2 3 1 Show Abstract
3 Department of Electrical and Computer Engineering, Rice University, Houston, Texas, United States, 4 Department of Chemistry, Rice University, Houston, Texas, United States, 1 Laboratory for Nanophotonics, Rice University, Houston, Texas, United States, 2 Department of Physics and Astronomy, Rice University, Houston, Texas, United States
It has recently been shown that the localized plasmon resonances of complex nanostructures can be understood as arising from the hybridization of simpler, fixed frequency primitive plasmons supported by the structure. This Plasmon Hybridization picture extends naturally to the interaction between the localized plasmon resonances of metallic nanostructures and the propagating plasmons on extended structures such as films, wires, or gratings. This interaction is described by the spinless Anderson model, where the regimes of this model can be accessed by varying the geometry of the system. We will discuss this interaction in plasmonic geometries which have recently been experimentally realized.
10:00 AM - **R4.2
Plasmonic Metamaterials and Optical-Field Nanoelectronics.
Nader Engheta 1 Show Abstract
1 Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States
Metamaterials with negative or near-zero parameters have attracted a great deal of attention in recent years in the microwave, infrared (IR) and optics communities. Owing to their unconventional electromagnetic characteristics, these materials may offer exciting possibilities in various applications. For many years, the familiar notion of lumped circuit elements has been extensively and successfully used in the radio frequency (RF) and microwaves. This concept has allowed “modularization” of various functions at the circuit level, and thus has been proven to be a powerful tool in design, innovation, and discovery of new functionalities in those frequency domains. We have been exploring the possibilities of bringing the concept of lumped circuit elements into the optical domain. In particular, we have been interested on how one can envision optical nanostructures that can act as “modules” representing lumped circuit elements at the optical frequencies. In our recent works [N. Engheta, A. Salandrino, and A. Alù, Phys. Rev. Lett., 95, 095504 (2005); A. Alù and N. Engheta, J. Opt. Soc. Am. B. Vol. 23, No. 3, pp. 571-583, March 2006] we have investigated analytically and numerically how plasmonic, non-plasmonic, and near-zero-epsilon (ENZ) nanoparticles, when designed properly, can indeed act as such lumped nanoelements. In our computational efforts, we consider several classes of nanoparticles of sub-wavelength size, made of combinations of non-plasmonic materials, plasmonic materials, and nonlinear optical materials.. According to our analysis, these nanoparticles can act as nanocapacitors, nanoinductors, nanoresistors, nanoinsulators, nanoconnectors, and nanodiodes. These elements can be arranged in “parallel” and “series” configurations, resulting in more complex circuit structures. This concept will provide the possibility of utilizing and extending the concepts and mathematical tools of circuit theory into the THz, IR and Optical frequencies, and will open doors to many innovations in future optical nanoelectronics and nanosystems. In our theoretical and computational works, we have shown how this concept of “optical-field nanoelectronics”, as a new paradigm for information processing, can be extended to more general circuits with various resonances, thus providing new ways of designing nano-scale optical components and devices at optical wavelengths. This can lead to direct processing of optical signals, nano-switches, nano-antennas and arrays, nano-beam patterning and nanospectroscopy and nano-circuit-filters with possible applications in nano-computing, nano-storage, molecular signaling, and molecular-optical interfacing. Such nanoelectronics may one day be also interfaced with biological circuits, leading to the possibility of hybrid nano-bio circuits.In this talk, I will present an overview of some of our theoretical results and computational simulations on this concept of optical field nanoelectronics.
10:30 AM - R4.3
Plasmonic Laser Antenna.
Ertugrul Cubukcu 1 , Elizabeth Smythe 1 , Kenneth Crozier 1 , Federico Capasso 1 Show Abstract
1 DEAS, Harvard University, Cambridge, Massachusetts, United States
We have demonstrated a new surface plasmon device that consists of a resonant optical antenna integrated on to the facet of a commercial diode laser, termed a plasmonic laser antenna. This device allows intense and spatially confined optical fields to be generated in the near-field zone. Spot sizes of a few tens of nanometers have been measured at a wavelength ~0.83 μm. This device can be implemented in a wide variety of semiconductor lasers emitting in spectral regions ranging from the visible and the near infrared to the mid- and far-infared, including quantum cascade lasers. As such it is potentially useful in a broad range of applications including near-field optical microscopes, optical data storage, spatially resolved chemical imaging and spectroscopy and heat-assisted magnetic recording.Finite difference time domain method is used to model the antenna structures. The field enhancement is maximized when the wavelength is suitably matched to the size of the nanoparticle (resonant optical antenna). Our first design consists of two coupled gold nanorod antennas separated by a gap of 20 nm. Each gold nanorod is 120 nm long and has a 50 nm x 50 nm square cross section. In our simulations the incident field is polarized along the antenna axis. The time averaged total electric field intensity is calculated in the gap and is enhanced by a factor of 700 relative to the incident intensity. Physically this enhancement is due to the charges accumulating on both sides of the gap, analogous to a capacitor, thus generating an enhanced electric field in the near field zone. For the perpendicular polarization, no enhancement was observed. Our second design utilized gold bowties-coupled triangular nanoparticles separated by a nanometric gap. It is advantageous to use the bowties as they act like nano-lightning-rods and confine the electric field enhancement to the gap rather than have it equally distributed over both ends. Optical antennas are fabricated on an edge-emitting laser diode operating at a wavelength of 830 nm. To prevent electrical shorting of the laser and the monitor photodiode in the laser package, alumina was deposited first onto the laser facet as an insulating layer. A gold layer was then evaporated onto the alumina layer. Next the optical antenna was defined by focused ion beam milling.An apertureless near field optical microscope is used to measure these enhanced, primarily non-propagating fields. The laser diode is operated at low duty cycles with a pulse length of 20 ns and a repetition frequency of 2 MHz. The gold-coated silicon atomic force microscope tip is scanned over the optical antenna in non-contact mode, with the very end of the tip scattering light from the field distribution on the surface of the optical antenna. The full-width-at-half-maximum of the central peak of the near-field intensity distribution is 40 nm along the axis of the nanorods and 100 nm in the other direction.
11:15 AM - R4.4
THz Plasmonics: Guiding and Super-focusing of Terahertz Waves Using Structured Conductive Surfaces and Wires.
Stefan Maier 1 , Steve Andrews 1 , Luis Martin-Moreno 3 , Francisco Garcia-Vidal 2 Show Abstract
1 Dep. of Physics, University of Bath, Bath United Kingdom, 3 Departamento de Fisica Teorica de la Materia Condensada, Universidad de Zaragoza, Zaragoza Spain, 2 Departamento de Fisica de la Materia Condensada, Universidad Autonoma de Madrid, Madrid Spain
The field of plasmonics has experienced an explosive growth in research efforts in recent years, fuelled by the fascinating possibility of confining and guiding electromagnetic energy over length scales significantly smaller than the free-space wavelength. This energy localization is due to the coupling of the electromagnetic field to the electron plasma of a conductor at its interface with an insulator. However, these hybrid excitations, known as surface plasmon polaritons (SPPs), are only closely confined to the surface when excited at a frequency that is close to the intrinsic plasma frequency of the conductor, which for most metals is in the ultraviolet part of the spectrum. Therefore, sub-wavelength energy localization using SPPs sustained by metals has been limited to visible and near-infrared frequencies.At lower frequencies, such as in the technologically important far-infrared (THz) regime, SPPs resemble a grazing incidence light field only weakly confined to the metal surface and extending several cm into the dielectric. Sub-wavelength confinement resembling that achievable at visible frequencies is in principle possible using doped semiconductors with a plasma frequencies about 6 orders of magnitude lower than that of metals, however the intrinsic losses of such materials are not promising for practical applications in SPP guiding.We will present a detailed assessment of a different and highly promising approach using structured metal surfaces, based on the design of an effective meta-material layer that sustains SPP-like excitations termed ‘spoof plasmons’. Here, the surface topography instead of the intrinsic properties of the metal determines the properties of the surface waves. Two geometries will be discussed. Firstly, planar metal surfaces structured with regular one- or two-dimensional arrays of grooves or holes. Three-dimensional electromagnetic modelling suggests the possibility of designing the surface in order to allow the guiding of SPPs at a frequency around 1 THz using physically realistic geometric parameters. Details of the dispersion relation, mode profile, and broad-band pulse propagation will be presented. Additionally, the possibility of creating defect waveguides with sub-wavelength out-of-plane and wavelength-scale in-plane confinement will be assessed.Our second geometry is based on a metal wire corrugated with a regular array of annular grooves. We will show that such a meta-wire can be used for the guiding of THz-SPPs with sub-wavelength radial confinement, and that energy concentration as well as super-focusing is possible in adiabatically graded structures. The latter could enable a new form of THz near-field microscopy.We will also address challenges regarding the fabrication these planar and wire meta-materials for THz SPP guiding, and preliminary experimental results on their guiding properties.
11:45 AM - R4.6
Distance Dependence of Fluorescence from Fluorophores Near Silver Nanoparticles.
Keiko Munechika 1 , Yeechi Chen 2 , David Ginger 1 Show Abstract
1 Chemistry, University of Washington, Seattle, Washington, United States, 2 Physics, University of Washington, Seattle, Washington, United States
12:00 PM - R4.7
Ellipsometric Identification of Collective Optical Properties of Silver Nanocrystal Arrays.
Stefan Kooij 1 , Anne-Isabelle Henry 2 , Herbert Wormeester 1 , Bene Poelsema 1 , Marie-Paule Pileni 2 Show Abstract
1 Solid State Physics, MESA+ Institute for Nanotechnology, University of Twente, Enschede Netherlands, 2 LM2N, Université Pierre et Marie Curie, Paris France
The optical properties of 5nm diameter silver nanocrystal arrays, self-assembled on graphite (HOPG) substrates, have been investigated using spectroscopic ellipsometry in combination with polarized reflection measurements. Analysis of the ellipsometry and reflectometry spectra in terms of the “Thin Island Film” theory enables identification of the contribution of collective effects to the optical response. Negligible image charge effects imply that only dipole contributions have to be considered. The interactions between the hexagonally ordered silver nanocrystals give rise to an effective modification of the optical response of the individual spherical nano-particles. The optical characteristic of the nanocrystal arrays can still be described in terms of individual entities, but their response is modified to that of oblate entities with different polarizabilities parallel and perpendicular to the substrate, expressed in terms of corresponding depolarization factors. The effect of nanocrystal ordering, nearest-neighbour distance, size distribution, surrounding ambient and the optical properties of the single nanocrystals on the optical response have been analysed. The extent of plasmon resonance peak splitting as a function of surface coverage will be discussed, in relation to the constituting materials.
12:15 PM - R4.8
Semiconductor-Metal Hybrid Nanocrystal Superstructures and Metamaterials: Photonic Properties and Exciton-Plasmon Interactions.
Alexander Govorov 1 , Garnett Bryant 2 , Jaebeom Lee 3 , Nicholas Kotov 3 Show Abstract
1 Physics and Astronomy, Ohio University, Athens, Ohio, United States, 2 Atomic Physics Division, NIST, Gaithersburg, Maryland, United States, 3 Department of Chemical Engineering , University of Michigan, Ann Arbor, Michigan, United States
We describe optical and thermal properties of a novel class ofhybrid nanoscale structures and meta-materials composed of metal and semiconductornanoparticles (NPs), and bio-linkers/polymers. Our study is inspired by recentexperiments on bio-conjugated semiconductor-metal NP complexes [1-4] and theirpotential applications as sensors. These experiments demonstrate that a differentorganization (architecture) of a hybrid nano-complex results in qualitatively differentoptical properties. In many studies, metal (Au or Ag) NPs result in quenching thephotoluminescence. However, certain architectures can be found to achieve a strong PLenhancement. For example, the plasmon enhancement effect can be achieved utilizing acollective resonance of many Au-NPs organized in spherical or cylindrical shells [1-4].Our theory describes and explains the above observations. With a computer code basedon the multipole expansion, we can compute optical properties of complexes made oftens and hundreds of NPs of different material. In these complexes, Au NPs act as aphotonic amplifier/damper and a CdTe NP as an emitter. In contrast to the epitaxialnanostructures, colloidal superstructures and meta-materials studied here can becomposed of different materials; one structure includes gold, silver, andsemiconductor nanoparticles [1,4]. In this way, a superstructure provides novel, uniqueproperties coming from a combination of physical responses of different materials. Forexample, different plasmon resonances of Au and Ag NPs provide enhancement of lightemission and absorption [1,4], while a semiconductor NP provides strongexciton emission. Using specific polymer linkers, we can make our photonic structuressensitive to temperature since a dimension of polymer can be temperature-dependent;this suggests sensor applications. J. Lee, A. O. Govorov, J. Dulka, and N. A. Kotov, Nano Letters, 4, 2323 (2004). J. Lee, A. O. Govorov, and N. A. Kotov, Angewandte Chemie, 117, 7605 (2005). A. O. Govorov, G. W. Bryant, W. Zhang, T. Skeini, J. Lee, N. A. Kotov, J. M. Slocik,and R. R. Naik, Nano Letters, 6, 984 (2006). J. Lee, A. O. Govorov, G. W. Bryant, and N. A. Kotov, Angewandte Chemie (2006), in press.
12:30 PM - R4.9
Tunable Terahertz Granular Pyroelectric-Semiconductor Media.
Alexander Dmitriev 1 , Valentin Kachorovskii 1 , Michael Shur 1 Show Abstract
1 , RPI, Troy, New York, United States
12:45 PM - R4.10
Nonlinear Optical Properties of Metal and Core/shell Colloidal Nanostructures.
Mingzhao Liu 1 , Philippe Guyot-Sionnest 1 Show Abstract
1 James Franck Institute, University of Chicago, Chicago, Illinois, United States
R5: Phononic and Photonic Crystals and Meta-Materials
Wednesday PM, November 29, 2006
Room 313 (Hynes)
2:30 PM - **R5.1
C. Chan , Jensen Li 1 Show Abstract
, 1 Physics, Hong Kong University of Science and Technology, Hong Kong Hong Kong
Meta-materials are artificial materials exhibiting simultaneously negative permeability and permittivity, and the “double negativity” gives rise to many interesting phenomena such as negative refraction for electromagnetic waves. We will attempt to extend the concept to acoustic waves. We will show the existence of acoustic metamaterial, in which both the effective density and bulk modulus are simultaneously negative at some particular frequency range, in the sense of an effective medium. Our double negative acoustic system is an acoustic analogue of Veselago’s medium in electromagnetism, and shares many novel consequences such as negative refractive index. The double negativity in acoustic is derived from low frequency resonances, as in the case of electromagnetism, but the negative density and modulus are derived from a single resonance structure, as distinct from electromagnetism in which the negative permeability and negative permittivity originates from different resonance mechanisms.
3:00 PM - **R5.2
Phononic Crystals in Plates and Films.
Pierre Deymier 1 , Jerome Vasseur 2 , Bahram Djafari-Rouhani 2 , Yan Pennec 2 Show Abstract
1 Materials Science and Engineering, University of Arizona, Tucson, Arizona, United States, 2 , EPHONI, Institut d’Electronique, de Microelectronique et de Nanotechnologie, UMR CNRS 8520, Cité Scientifique , 59652 Villeneuve d’Ascq Cedex France
Two-dimensional and three- dimensional bulk phononic crystals have received a lot of attention in the past decade. In particular, these materials have been shown to exhibit absolute band gaps in their transmission spectrum. Furthermore, bulk phononic crystals containing point or linear defects possess localized or wave guiding modes in their forbidden bands. The application of phononic crystals to signal processing and telecommunications provides a compelling reason for the study of phononic crystals in plates and thin films. We report on the calculation of the elastic band structures of two-dimensional phononic crystal plates using the super-cell plane wave expansion method. These band structures differ significantly from the infinite 2D phononic crystal dispersion curves. The phononic crystal plates show surface modes and guided modes in their elastic band structure. The existence of gaps for plate modes depends very strongly on the thickness of the plate relative to the periodicity of the crystal. Defected phononic crystals in plates are also investigated with focus on the observation of vibrational plate modes localized in the defect enabling wave guiding.
3:30 PM - R5.3
Negative Refraction and Focusing of Ultrasound in a 2D Phononic Crystal.
Alexey Sukhovich 1 , John Page 1 , Zhengyou Liu 2 Show Abstract
1 Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada, 2 , Wuhan University, Wuhan China
3:45 PM - R5.4
Interfacial Phenomena in Strongly Nonlinear Phononic Crystals: Anomalous Reflected Waves and Energy Trapping Devices.
Chiara Daraio 2 , Vitali Nesterenko 1 , Eric Herbold 1 , Sungho Jin 1 Show Abstract
2 Aeronautics and Applied Physics, Caltech, Pasadena, California, United States, 1 Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, California, United States
4:45 PM - R5.6
Scalability of Phononic Crystal Heterostructures.
Rampi Ramprasad 1 , Ning Shi 1 Show Abstract
1 Institute of Materials Science, Dept. of Chemical, Materials and Biomolecular Engineering, University of Connecticut, Storrs, Connecticut, United States
Acoustic band-gap (ABG) materials, the acoustic analogs of photonic band-gap (PBG) systems, are artificially engineered materials with a spatially periodic variation in the material properties such as the mass density, elastic moduli, etc., that determine the propagation of acoustic waves in the medium. Acoustic waves with a half-wavelength of the order of the lattice constant of the ABG crystal undergo Bragg-type wave scattering, and so are forbidden from propagating through such periodic media.The classical wave equations for both ABG and PBG crystals allow for scaling in the following manner: uniformly expanding or shrinking the physical sizes by a factor a results in the frequency spectrum being scaled by 1/a. This feature has allowed researchers to indirectly test the properties of ABG and PBG materials at high frequencies where length scales are small by studying their scaled analogs at lower frequencies, where the larger length scales allow for easy fabrication.ABG materials have so far been designed under the assumptions that the properties of each constituent of the crystal are identical to their bulk counterparts, and abruptly change at the interface between the components. It is, however, unclear whether these assumption are valid when system sizes reach nanoscale dimensions, making the applicability of the scaling laws up to nanoscale dimensions rather moot.Acoustic band structure calculations have been performed for a nanoscale HfO2-ZrO2 multilayer stack using first-principles methods at the atomistic level and by solving the acoustic wave equation at the continuum level, as a first step toward determining the length scales when conventional continuum acoustic band-gap treatments become inadequate. Transverse acoustic waves are the focus of this study. The material parameters that continuum acoustic band gap methods require, such as the mass density and transverse wave velocity of the components of the acoustic crystal (i.e., for HfO2 and ZrO2), were determined using separate phonon calculations of the corresponding bulk materials. Comparison of the phononic band structure for a nanoscale HfO2–ZrO2 multilayer stack calculated using first-principles and continuum methods indicates the need for careful treatments of wave propagation properties at these length scales.
5:00 PM - R5.7
Transmission Enhancement and Suppression by Subwavelength Hole Arrays in SiC Films.
Peter Catrysse 1 , Shanhui Fan 1 Show Abstract
1 Electrical Engineering, Stanford University, Stanford, California, United States
5:15 PM - **R5.8
Design of Materials and Structures with Optimized Dynamic Properties.
Jakob Jensen 1 Show Abstract
1 Department of Mechanical Engineering, Technical University of Denmark, Lyngby Denmark
5:45 PM - R5.9
Computational Design of Holographic Structures using Genetic Algorithms.
James Rinne 1 2 , Pierre Wiltzius 1 2 Show Abstract
1 Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 2 , Beckman Institute for Advanced Science and Technology, Urbana, Illinois, United States
Holographic lithography is an attractive technique for the fabrication of three-dimensional (3D) photonic crystals. It relies on the concurrent exposure of four or more non-coplanar beams of coherent light to transfer a 3D periodic intensity distribution into photoresist. The relationship between a given set of beam parameters and the resultant structure is straight forward to understand within the general context of interference. However, the design of a given structure requires an understanding of the intractable inverse relationship between a structure and the beam parameters that will produce it. In this work, we have developed a computational approach using genetic algorithms to reveal such inverse relationships. In contrast to current analytical approaches that rely almost exclusively on symmetry considerations, this technique allows for high-fidelity approximations to structures without limiting the search space to a prescribed set of symmetries. We have employed this new approach to design various structures of interest to the photonic crystals community. In particular, we demonstrate a diamond-like structure having an exceptionally large photonic band gap of 28%.
Rampi Ramprasad University of Connecticut
John Page University of Manitoba
Philippe Renaud Freescale Semiconductor
Pawitter Mangat Motorola, Inc.
R6: Novel Meta-Materials: Synthesis, Characterization and Applications
Thursday AM, November 30, 2006
Room 313 (Hynes)
9:00 AM - **R6.1
Plasmonic Negative Index Nanostructures at Optical Frequencies.
Alexandre Bratkovsky 1 , E. Ponizovskaya 1 Show Abstract
1 , HP Labs, Palo Alto, California, United States
We describe various designs of metamaterials for Veselago lens that may potentially perform at optical frequencies. Plasmonic periodic metallic nanostructures present one interesting possibility for both 2D and 3Dnegative index medium (NIM) systems. NIM is a system having opposite group and phase velocities in a particular frequency range and thus supporting 'negative' refractionand 'backward' propagating waves. It is known since 1940s that crystals with strong spatial dispersion may exhibit negative refraction. It was shown by Pafomov  and Veselago  that an isotropic medium with both negative permittivity and permeability would support backward waves, and parallel slab impedance matched to vacuum may produce an exact replica of an object (Veselago lens). Systems with strong spatial dispersion (e.g. photonic dielectric bandgap crystals) are known to exhibit negative refraction.Metallic 2D and 3D metamaterials that we focus on here may support plasmon excitations, which also produce negative permeability in structures like 'fishnet' multilayers. There are indications that unusual response can be obtained in isotropic metal-dielectric composites with nanoparticles, and we shall discuss some recent results. The obvious problem with metallic NIM is that their response is strongly dispersive and lossy. Both of these effects are detrimental to subwavelength imaging . One way of mitigating losses is to use gain medium. There are potential mechanisms of modulating signals with the use of compact NIM slabs.  V.E. Pafomov, Zh. Eksp. Teor. Fiz. 36, 1853 (1959) V.G. Veselago, Usp. Fiz. Nauk 92, 517 (1967) A.M. Bratkovsky, A.Cano, and A.P. Levanyuk, Appl. Phys. Lett. 87, 103507 (2005).
9:30 AM - **R6.2
Biological Recognition Motifs in the Fabrication of Meta-Materials
Fotios Papadimitrakopoulos 1 2 Show Abstract
1 University of Connecticut, Nanomaterials Optoelectronics Laboratory, Institute of Materials Science, Storrs, Connecticut, United States, 2 Department of Chemistry, University of Connecticut, Storrs, Connecticut, United States
Realization of meta-materials and structures operating at the optical wavelengths relies on our ability to facilely organize different materials at the nano- micro- and millimeter scale. In this presentation, a variety of fabrication methodologies will be discussed with particular emphasis to biologically-derived organization motifs. Drawing analogies from biology, a number of self-assembly processes will be discussed to guide the organization of inorganic materials into three-dimensional meta-structures. Attaining organization at the micro level and beyond, while preserving both recognition and specific materials parameters to achieve negative ε
, present a major scientific and technological challenge. Attention will be given to processes that result in structures with long-range order and dimensional stability. In addition, examples from our work will be given in the area of 2- and 3-dimensional photonic crystals, using DNA-based recognition. Methodologies to reduce the number of lattice defects, while permitting controlled insertion of defects, will be also discussed, using the microsphere assembly as a model system.
Financial support from AFOSR and ONR is greatly appreciated.
10:00 AM - **R6.3
Metamaterials: Challenging Conventional Magnetic Materials.
Olivier Acher 1 , Anne-Lise Adenot Engelvin 1 , Marc Ledieu 1 , Jean-Marie Lerat 1 Show Abstract
1 , CEA, Monts France
10:30 AM - R6.4
Functional Metamaterials Based on Mesoscale Gold Sponges, Particulate Aggregates, and Their Composites with Dielectric Materials
Michael Cortie 1 , Abbas Maaroof 1 , Lech Wieczorek 2 , Geoffrey Smith 1 Show Abstract
1 Institute for Nanoscale Technology, University of Technology Sydney, Broadway, New South Wales, Australia, 2 Industrial Physics, CSIRO, Sydney, New South Wales, Australia
Mesoporous gold sponge, which is characterized by having a continuous, nanoscale gold skeleton with air or dielectric-filled voids, can be considered to be an example of a meta-material. The metallic optical properties of the gold are significantly altered by the nature of the porosity and morphology of the voids in the sponge, and can be tuned from fully metallic through to those more typical of an insulator by control of these factors. The sponges can be readily prepared by the corrosive de-alloying of an intermetallic precursor compound such as AuAl2.Here we examine the range of mesostructures that can be produced experimentally by this means, consider their associated optical properties, and show how the latter can, despite their complex geometries, be predicted by numerical simulations based on the Discrete Dipole Approximation (DDA). Back-filling of the voids in these sponges with a functional dielectric, such as VO2 which undergoes a reversible semi-conductor to metallic phase transformation at ~67C, produces meta-materials of even greater versatility. These dual-phase materials can be used as the basis of thermally-activated optical switches or coatings with more flexible characteristics than possible using the individual components. It is also interesting to examine the inverse type of structure, in which the insulating substance is the continuous phase. In fact the inverse structure is historically the better studied of the two on account of it being readily prepared by the controlled agglomeration of metallic nanoparticles. This presents a different and equally flexible range of spectral options, with the optical properties being once again highly influenced by the volume fractions of the two constituent phases, their dielectric properties and, in particular, their size distributions. Although Effective Medium theories have traditionally been used to model these types of complex structure, we show that reasonable results can be achieved by numerical simulations based on the DDA using only the system geometries and bulk optical properties of the constituents as input parameters. However, further improvements in predictive capabilities can be attained by specifically incorporating the changes to optical properties that occur in nanostructured materials of high specific surface area. As an example, we have simulated the quite different optical properties that can be achieved for two metamaterials with the same volume fraction but different size distributions of gold nanoparticles. An understanding and control of these composite microstructures provides the means to design and fabricate metamaterials with a very wide range of user-defined optical characteristics.
11:45 AM - R6.6
Tunable Optical Properties of 2-D Silver Nanocrystal Superlattices
Andrea Tao 1 2 , Peidong Yang 1 2 Show Abstract
1 Chemistry, UC Berkeley, Berkeley, California, United States, 2 Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Plasmon modes supported by nanostructured surfaces facilitate the novel or enhanced optical phenomena exhibited by noble metal films. We demonstrate that such films can be rationally engineered through a bottom-up approach by utilizing Langmuir-Blodgett assembly. Here, shape-controlled Ag nanocrystals are deposited at an air-water interface and then subjected to isothermal compression to form crystalline, close-packed monolayers. We can achieve various array architectures by using differently shaped nanocrystal building blocks. This technique is a facile, robust method for obtaining long-range order over extensive areas (~few square cm), where periodicity and average interparticle spacing are continuously variable. Thus, it offers an unprecedented approach in examining how nanocrystal size and spacing control the electromagnetic coupling responsible for plasmon-mediated effects, such as intense light scattering and enhanced optical transmission through sub-wavelength holes. This assembly strategy is likely to be extremely valuable in generating new metamaterials for application in sub-wavelength optics, integrated photonic-plasmonic devices, and nanoscale imaging.
12:00 PM - R6.7
Route to Three-dimensional Micron-scale Meta-materials via Multi-photon Patterning.
Stephen Kuebler 1 2 , Yun-Sheng Chen 1 , Amir Tal 2 Show Abstract
1 Department of Chemistry, University of Central Florida, Orlando, Florida, United States, 2 CREOL, The College of Optics and Photonics, University of Central Florida, Orlando, Florida, United States
12:15 PM - R6.8
Laser Chemical Vapor Deposition of Coils: Geometric Influences on Stead-State Growth Rates
Karlene Maskaly 2 , Marcie Black 2 , James Maxwell 2 , Craig Chavez 2 Show Abstract
2 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Meta materials often require components consisting of unusual shapes constructed from very specific materials. Laser Chemical Vapor Deposition (LCVD) possesses some unique characteristics that make it one possible technique for creating such components on the millimeter and micron-scales. In LCVD, a laser is focused onto a substrate and a spot roughly the size of the focal point is heated. The local heating of the substrate causes a thermolytic reaction of the precursors to occur, resulting in the deposition of the reaction byproduct(s) on the surface. Since only a small area of the surface is heated, wires, tubes, coils, and branching structures with diameters in the millimeter and micron range can be grown. Furthermore, the elevated temperatures involved in the reaction process allow for the fabrication of structures made from material compositions that are not accessible using lower temperature fabrication processes. In this talk, LCVD is used to create carbon graphite coils with a diameters ranging from approximately 50 to 100 microns. The diameter can be varied insitu; so many different shapes are obtainable. We investigate the radial growth rate of coils as a function of diameter and compare these rates to the growth rate of straight wires. We find that the growth rate varies only weakly with coil diameter. Coils, instead of wires, can therefore be used to measure the growth rates of new exploratory compositions and processing parameters (precursor composition, pressure, and temperature), thus making growth rate measurements possible with a more accurate, faster, space efficient method.
12:30 PM - R6.9
Isolated arrays of Glass Spheres for Coupling of Whispering Gallery Modes.
Elizabeth Tull 1 , Phil Bartlett 1 , Kate Ryan 1 Show Abstract
1 Chemistry, University of Southampton, Southampton United Kingdom
Interest in developing planar lightwave circuits exploiting the optical behaviour of glass spheres coupled to planar waveguides, has resulted in a need to create sparse arrays of glass spheres at particular locations on planar waveguide substrates. At present this sort of positioning is only achievable using optical tweezers or AFM, processes which are expensive and difficult to scale up.Assembly of large, dense particles into sparse arrays is limited by sedimentation and is currently restricted to substrates supporting a high density of patterned sites.In this work, a new method of particle assembly is presented, which yields isolated patches of glass spheres, in a small number of specific locations, across large planar substrates. The method, which combines a variable-tilt flow cell with chemical patterning and de-wetting techniques, is applicable for particle deposition onto both topographically and chemically patterned substrates, and through exploitation of a number of experimental variables, provides unique control over the deposition process and scope for the production of different devices.Results demonstrating the tuneable nature of this approach are presented together with a theoretical model examining the relative strengths of gravitational, electrostatic and capillary forces in each case.References1. D. N. Moothoo, et al., Am. J. Phys., 2001, 69, 2712. B. Siciliano et al., Tracts in Adv. Robot., 2003, 5, 3823. Y. Masuda et al., Advanced Materials, 2005, 17, 841
12:45 PM - R6.10
Simulations of the Self-assembly of Nanoparticle Supperlattices.
Alexey Titov 1 , Petr Kral 1 Show Abstract
1 Chemistry, University of Illinois at Chicago, Chicago, Illinois, United States