Paul V. Braun University of Illinois, Urbana-Champaign
Shanhui Fan Stanford University
Andrew J. Turberfield University of Oxford
Shawn-Yu Lin Rensselaer Polytechnic Institute
AA1/D1: Joint Session: Fabricating and Filling Complex 3-d Structures
Tuesday PM, April 10, 2007
Room 3003 (Moscone West)
9:30 AM - **AA1.1/D1.1
Electrodeposition Through Colloidal Templates: Fabrication of Nanostructures, Properties and Applications.
Philip Bartlett 1 Show Abstract
1 Chemistry, Southampton University, Southampton, Hampshire, United Kingdom
Templated electrochemical deposition through close packed monolayers of unform polystyrene colloidal particles assembled on electrode surfaces produces structured thin films. Removal of the template by dissolution leaves a supported thin metallic film containing an array of interconnected spherical segement voids. Because electrodeposition is a volume filling technique which does not require a heat treatment step the diameters and organisation of these voids replicates the diameter and packing of the colloidal particles used to form the template. In addition the thickness of the film is controlled by the charge passed to deposit the film. It is thus possible to simply and predictably control the geometry of the structured films produced. These structured metal films have interesting magnetic , superconducting  and optical properties  that are determined by their precise geometry.Using templates with diameters between 450 and 1200 nm we are able to produce metallic surfaces that show significant surface enhancement in surface enhanced Raman spectroscopy (SERS) if the correct sphere diameter and film thickness are used. We have investigated the origins of this surface enhancement by varying the film thickness, template sphere diameter and by looking at the angular dependence. We find that the intensity of the SER spectra varies with all of these factors indicating that the precise geometry of the structured surface and the excitation of surface plasmons is important in producing the surface enhancement. Studies of the SERS intensity at the structured surfaces show that the signal is linear with laser light intensity. We also find that the enhancement varies with the laser wavelength. These results are consistent with electromagnetic enhancement of the SERS signal caused by the excitation of confined plasmons  at the structured metal surface. This tentative explanation is consistent with our detailed studies of the reflection spectra of the structured metal films as a function of pore diameter, film thickness and angle of incidence . In contrast to the electrochemically roughened surfaces the intensity of the SERS spectra on the structured surface is reproducible from place to place across the surface and from sample to sample. This is a significant potential advantage. The structured surfaces are also robust and stable under laboratory conditions and ideally suited as electrodes for electrochemical SERS experiments since they do not have a high surface area. References:  P. N. Bartlett, M. A. Ghanem, I. S. El Hallag, P. de Groot, A. Zhukov, J. Mater. Chem., 13, 2003, 2596. A. A. Zhukov, E. T. Filby, M. A. Ghanem, P. N. Bartlett and P. A. J. de Groot, Physica C, 404, 2004, 455. P. N. Bartlett, J. J. Baumberg, S. Coyle and M. Abdelsalem, Faraday Discuss., 125, 2004, 117. S. Coyle, M. C. Netti, J. J. Baumberg, M. A. Ghanem, P. R. Birkin, P. N. Bartlett and D. M. Whitaker, Phys. Rev. Lett., 87, 2001, 176801-1.
10:00 AM - AA1.2/D1.2
Variable Filling Fraction Inverse Opal Metallic Photonic Crystals
Xindi Yu 1 , Yun-Ju Lee 1 , Robert Furstenberg 2 , Jeffrey White 2 , Paul Braun 1 Show Abstract
1 Material Science and Engineering, University of Illinois, Urbana, Illinois, United States, 2 Physics, University of Illinois at Urbana Champaign, Urbana, Illinois, United States
Metallic photonic crystals, metal based structures with periodicities on the scale of the wavelength of light, have attracted considerable attention due to the potential for new properties, including the possibility of a complete photonic band gap with reduced structural constraints compared to purely dielectric photonic crystals, unique optical absorption and thermally stimulated emission behavior, and interesting plasmonic physics. Photonic applications may include high efficiency light sources, chemical detection, and photovoltaic energy conversion. Other applications for three-dimensionally porous metals, so called “metal foams”, include acoustic damping, high strength to weight structures, catalytic materials, and battery electrodes. The photonic properties of metallic inverse opal structures have been of significant interest because of the simplicity of fabrication and potential for large area structures. However, in practice, experiments on metal inverse opals have been inconclusive, presumably because of structural inhomogeneities due to synthetic limitations. In this work, we demonstrate an electrochemical approach for fabricating high quality metal inverse opals with complete control over sample thickness, surface topography and for the first time, the structural openness (metal filling fraction). Optical measurements conclusively demonstrate that metal inverse opals modulate the absorption and thermal emission of the metal and that these effects only become three-dimensional (3D) in nature at high degrees of structural openness.
10:15 AM - **AA1.3/D1.3
Surface Engineering of Aerogels via Atomic Layer Deposition
Juergen Biener 1 Show Abstract
1 Nanoscale Synthesis and Characterization Laboratory, Lawrence Livermore National Laboratory, Livermore, California, United States
Nanoporous materials with tailored surface functionality hold technological promise for applications such as sensors, energy storage, and catalysis. Such materials can be developed using aerogels as a flexible and robust material platform. While macro-cellular open-cell foams can be easily coated via chemical or physical vapor deposition, shadowing effects and diffusion limitations become dominant at the submicron length scale. I will discuss a general approach to prepare such metal/aerogel nanocomposites via template directed atomic layer deposition (ALD). The approach was tested for a wide range of aerogel templates and ALD processes including the deposition of W, Ru, Pt, Cu, CuN and ZnO. In general, the process offers excellent control over composition and morphology. Furthermore, the ability to control the growth morphology of the deposited material opens the door to further fine-tune material properties by exploiting the size-effect frequently observed for nanoparticles. I will also discuss the limitations of the ALD approach, and suggest ways to overcome these.
11:15 AM - **AA1.4/D1.4
New Routes to Three-Dimensional Photonic Band-Gap Materials
Martin Hermatschweiler 1 , Sean Wong 2 , Alexandra Ledermann 2 , Geoffrey Ozin 4 , Martin Wegener 1 2 3 , Georg von Freymann 1 2 3 Show Abstract
1 Institut für Angewandte Physik, Universität Karlsruhe (TH), Karlsruhe Germany, 2 Institut für Nanotechnologie, Forschungszentrum Karlsruhe, Karlsruhe Germany, 4 Chemistry Department, University of Toronto, Toronto, Ontario, Canada, 3 DFG-CFN, Universität Karlsruhe (TH), Karlsruhe Germany
The past decade has witnessed intensive research efforts related to the design and fabrication of Photonic Crystals (PCs) [1,2]. These periodically structured dielectric materials can represent the optical analogue of semiconductor crystals and provide a novel platform for the realization of integrated photonics. While the layer-by-layer or “woodpile” structure  is amenable to microfabrication techniques and has already been realized at infrared frequencies through combinations of advanced planar semiconductor microstructuring techniques for individual layers with sophisticated alignment and stacking procedures to combine different layers into 3D PCs , more demanding structures like, e.g., photonic quasicrystals or chiral photonic crystals, cannot directly be realized with conventional techniques. Here we present two alternative approaches, which allow the realization of almost arbitrary three-dimensional structures: (i) In a first step, a three-dimensional polymer template is created via direct-laser-writing  (DLW). As the optical properties, especially the index of refraction, of the polymer (SU-8) are not sufficient for the opening of a complete photonic bandgap, we use a combination of atomic-layer-deposition (ALD) of silica and chemical vapor deposition (CVD) of silicon to replicate  or invert these intricate 3D templates with silicon. (ii) To overcome the need for additional ALD and CVD techniques, we directly write 3D structures into a high-index of refraction all-inorganic photoresist , namely into As2S3 chalcogenide glass. With a specially designed highly selective wet chemical etch, the unexposed areas are removed. Besides its high index of refraction, As2S3 is advantageous for 3D nanofabrication as it does not swell or shrink during etching, as polymer materials do. E. Yablonovitch, Phys. Rev. Lett. 58, 2059-2062 (1987).  S. John, Phys. Rev. Lett. 58, 2486-2489 (1987). K.-M. Ho et al., Solid State Comm. 89, 413-416 (1994). S. Y. Lin et al., Nature 394, 251-253 (1998).  M. Deubel et al., Nature Mater. 3, 444 (2004). N. Tétreault et al., Adv. Mater. 18, 457 (2006). S. Wong et al., Adv. Mater. 18, 265 (2006).
11:45 AM - **AA1.5/D1.5
Nano-Fabrication of 3D Optoelectronic Devices by Atomic Layer Deposition
Christopher Summers 1 , Elton Graugnard 1 , Davy Gaillot 1 , John Blair 1 , Olivia Roche 2 , David Sharp 2 , Robert Denning 3 , Andrew Turberfield 2 Show Abstract
1 Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Department of Physics, University of Oxford, Oxford United Kingdom, 3 Inorganic Chemistry Laboratory, University of Oxford, Oxford United Kingdom
The formation of 3D periodic dielectric contrast allows great control over the propagation of light. The two main challenges in fabricating patterned dielectric materials are pattern formation and dielectric control. Atomic layer deposition (ALD) has proven to be a powerful tool for fabricating new dielectric structures from patterned templates (produced by a variety of techniques) by enabling their facile inversion and replication into a wide range of dielectric materials. [1,2] Here, we present ALD of high transparency, high index, luminescent, electro-optic and nonlinear materials into self-assembled opal and lithographically derived templates, where each presents unique challenges and benefits as template structures. Investigations are presented on the fabrication of inverse opal based structures by multi-layer ALD of TiO2, Al2O3, and ZnS. Most recently new protocols have been developed for the ALD growth of GaP on metal oxide templates. It is demonstrated that novel derivatives of the opal structure can be obtained by the use of a sacrificial buffer layer, which is subsequently removed with the original template by etching and followed by regrowth of the target dielectric material. Consequently, structures can be inverted, precisely replicated, and formed from composite or multi-layered materials that allow a high degree of functionality: for example, luminescence modification and photonic band tuning. Additionally, this process enables polymer structures formed at low temperature to be inverted by low temperature ALD into a high temperature compatible material that then serves as a second high temperature template (double templating). Specific examples are given of the high degree of static and dynamic tunability (by liquid crystal infiltration) that can be obtained in non-close-packed opals, and recent work presented on the inversion and replication of holographically defined SU-8 templates and biological scaffolds. This work demonstrates a pathway to the fabrication of new lattices with complex geometries and material combinations that are needed to enable full control over light propagation in dielectric material devices. J. S. King, E. Graugnard, O. M. Roche, D. N. Sharp, J. Scrimgeour, R. G. Denning, A. J. Turberfield and C. J. Summers, Adv. Mater., 18, 1561 (2006). E. Graugnard, J. S. King, D. P. Gaillot and C. J. Summers, Adv. Func. Mater., 16, 1187 (2006).
12:15 PM - AA1.6/D1.6
Periodic Nanostructures Templated from Two-Dimensional and Three-Dimensional Colloidal Crystals
Peng Jiang 1 Show Abstract
1 Chemical Engineering, University of Florida, Gainesville, Florida, United States
Self-assembled colloidal crystals are ideal templates for creating three-dimensional (3D) highly ordered macroporous materials and photonic crystals. In this approach, the voids between colloidal spheres are infiltrated with another material and subsequent removal of the template by either wet etching or thermal decomposition leads to the formation of 3D ordered air cavities inside the structure-filling materials. Here we report two nonlithographic approaches to the fabrication of large-area, periodic nanostructured materials using both 2D and 3D colloidal crystals as templates. In the first approach, 3D ordered colloidal crystals, made by convective self-assembly or spin-coating, are used as templates to create 2D surface gratings, provided the subconformal deposition of materials by physical vapor deposition only occurs on the periodic surfaces of the templates. The technique allows the production of surface gratings from a large variety of functional materials, such as metals, semiconductors, and dielectrics. In the second approach, two-dimensional non-close-packed colloidal crystals fabricated by a simple spin-coating process are used as structural templates to make metallic nanohole arrays. Wafer-scale samples (up to 8-inch) can be easily made using standard physical vapor deposition. Complex micropatterns can be created by standard microfabrication for potential device applications. The templated periodic nanostructured materials have important technological applications in subwavelength optics, plasmonic sensors, and efficient organic light-emitting diodes (OLEDs).
12:30 PM - AA1.7/D1.7
Effect of SiC Whisker Growth on Cordierite Honeycomb by CVI Process.
Hwan Sup Lee 1 , Ik Whan Kim 1 , Doo Jin Choi 1 , Hia Doo Kim 2 Show Abstract
1 Department of Ceramic Engineering, Yonsei University , Seoul Korea (the Republic of), 2 Department of Materials Engineering, Korea Institute of Machinery and Materials, Seoul Korea (the Republic of)
Recently, there has been a increasing concern for the air pollutant caused by diesel engine such as particulates and nitrogen oxides. As these pollutant are mainly caused by diesel automobiles. Legal regulations are becoming rigorously strengthened. Hence, the diesel particulate filter (DPF) made of ceramic material is developed, to eliminate particulates generated by the diesel engines. For the application of DPF, the silicon carbide DPF with high strength are mainly used, and in developed countries, it is a standardized regulation to use these silicon carbide DPFs in the cutout units of diesel cars. However, the silicon carbide DPFs currently available in the market have 10μm mean pore size, which has also efficiency problem to capture nano-particulates less than 50nm size, and it is insufficient capturing filter to achieve the ultimate goal - i.e. atmosphere environment protection by capturing the particulates. This study was performed in order to improve conventional DPF efficiency by filtering nano-particle materials. SiC whiskers were grown on porous cordierite honeycomb in order to enhance the filtering efficiency, performance, and durability by controlling pore morphology. This experiment was performed by chemical vapor infiltration(CVI) process in order to grow the whiskers at inner pores without closing the pores. Metyltrichlorosillan(MTS) was used as source gas, and the input gas ratio α[H2/MTS] were 100 and 300, respectively. the deposition temperature was varied from 1000°C to 1300°C, and the deposition time was varied from 10min to 120min. After the deposition process, scanning electron microscopy(SEM) and universal testing machine were used to explain the micro-structure and compressive strength, respectively. The sizes of pores were measured with mercury porosimeter, and the gas permeability was analysed by the nitrogen gas injection method under 1 atmospheric pressure at 28°C, and the particulates trap test was conducted. The formation of "networking structure" in the inside of porous cordierite honeycomb was confirmed. The compressive strength of whiskered porous cordierite honeycomb increased from 24MPa to 60MPa(250%) after 1hour deposition at 1200°C. And the permeability of whiskered porous cordierite honeycomb was higher than that of cordierite honeycomb with similar pore size. This study showed the advantage of networking structure by whiskers in order to filter the nano-particulate materials with improved strength, reduced pore size and minimized permeability drop.
AA2: Colloidal Self-Assembly i
Tuesday PM, April 10, 2007
Room 2022 (Moscone West)
2:30 PM - **AA2.1
How Does Convective Assembly Work?
Linli Meng 1 , Hong Wei 1 , L. Scriven 1 , David Norris 1 Show Abstract
1 Chem. Eng. & Mat. Sci., Univ. of Minnesota, Minneapolis, Minnesota, United States
One simple route to three-dimensional microstructures is to utilize convective assembly, a process in which thin colloidal crystals are deposited on a substrate from suspensions of nearly monodisperse spheres. Previously, such crystals (also known as opaline films) have been shown to be highly ordered with a strong tendency toward the face-centered cubic (fcc) structure. Thus, they have become a very popular starting material for a wide range of applications from batteries to microfiltration to photonic crystals. However, the crystallization mechanism of convective assembly is not well understood. In particular, the tendency toward fcc is difficult to explain on thermodynamic grounds. Here we explore this issue by examining the microscopic details of convective assembly. Using real-time microscopic visualization, electron microscopy, and scanning confocal microscopy, we uncover interesting and unexpected features of the crystallization process. In some cases, previous puzzles from the literature can be resolved immediately by these observations. In addition, we also utilize the same techniques to quantify the density and distribution of stacking faults and vacancies in these thin colloidal crystals. Again, surprising details are revealed that help us understand the growth mechanism. The dream of this research is that a better understanding of the mechanism may provide an avenue for developing a new class of self-assembly techniques. By clever design of the process, new micro- and nanostructured films may be obtained.
3:00 PM - AA2.2
Laser Tweezer Manipulation of Nanoscale Particles in Photonic Crystals
Ryan Kershner 1 , Weon-Sik Chae 2 , Gabriel Spalding 3 , Paul Braun 2 Show Abstract
1 , IBM Almaden Research Center, San Jose, California, United States, 2 Beckman Institute, University of Illinois, Urbana, Illinois, United States, 3 Department of Physics, Illinois Wesleyan University, Bloomington, Illinois, United States
Photonic crystals have received a great deal of attention in recent years for their remarkable ability to harness and control light. One significant challenge remains the ability to controllably place individual defect states within an ordered lattice, with specific control over composition. Solving this problem is essential to realizing photonic waveguides in three dimensional periodic structures. Here we present a promising approach for control of individual features using laser tweezers. Synthetic opals were produced from 1.58 μm silica particles using a standard flow cell method. ~100 nm diameter ZnS core/SiO2 shell nanoparticles having a bulk index of refraction on the order of 2 were produced by controlled aggregation of ZnS seed nanocrystals, followed by SiO2 shell growth. Arrays of optical traps were utilized to grab individual nanoparticles and guide them through the pore structure (~ 250 nm) of the synthetic opal to pre-determined locations. By filling the opal with an index-matching solvent, scattering from the silica particles was reduced while still maintaining an index contrast between the medium and ZnS particles sufficient for trapping. Simple structures consisting of 3-6 particles were successfully fabricated as a proof of concept, and methods for producing more complicated structures will be proposed. Particle arrangements were fixed in place through polymerization of a photosensitive hydrogel, with the wavelength tuned far from that of the laser trap. Results obtained using Au nanoparticles also demonstrates the flexibility of this technique for controlling composition.
3:15 PM - AA2.3
Focussed Ion Beam Milling of Nanocavities in Single Colloidal Nanoparticles and in Self-Assembled Opals.
Leon Woldering 1 , Bert Otter 2 , Bart Husken 1 3 , Willem Vos 1 3 Show Abstract
1 Complex Photonic Systems (COPS), MESA+ Institute, University of Twente, Enschede Netherlands, 2 MESA+ Institute for Nanotechnology, University of Twente, Enschede Netherlands, 3 Center for Nanophotonics, FOM Institute for Atomic and Molecular Physics AMOLF, Amsterdam Netherlands
Artificial opals made from self-assembled colloidal nanoparticles are of considerable scientific and technological interest as photonic crystals; as components of light sources, solar cells, and chemical sensors; and in the field of plasmonics. While the majority of studies concern spherical nanoparticles, several exciting opportunities arise if the shape and morphology of individual particles can be controlled. Firstly, a monolayer of colloids can be used as a lithographic opal mask. Fabricating an aperture in one sphere in the monolayer adds a finely controlled feature to the mask. If size, shape and position of the aperture in the mask can be controlled with nanometer precision, detailed structural flexibility beyond the structure of the colloids is obtained. Secondly, if opals are made chemically selective by covering the opal with self-assembled monolayers, a cavity inside one sphere will add size-selectivity, since only molecules that fit in the cavity will go inside and bind. Additional local chemical specificity can be introduced at the modified nanostructure by local deposition methods (by e.g. ion beams). Thirdly if an opal is used as a photonic crystal, a single modified colloidal particle in the opal is expected to act as an optical cavity. To the best of our knowledge the controlled modification of the nanostructure of a single colloid in an opal has not been achieved to date.Here, we describe a versatile method to modify the structure of targeted individual silicon dioxide colloidal particles on the surface of opals with controllable features with radii smaller than 40 nm using focused ion beam milling (FIB) . With our technique, we mill a circularly shaped material cavity in the colloid, converting the particle into a donut-like or bead-like structure. We will refer to these material nanocavities as “defects” or “cavities”. We show that we can control both the size and the position of each cavity with nanometer precision. Additionally, we show that not only a single defect, but also an array of single defects can be fashioned in any desired pattern. Finally, we have also achieved nano-donuts from polystyrene colloidal particles. For more information, please visit www.photonicbandgaps.com  L.A. Woldering, A.M. Otter, B.H. Husken, and W.L. Vos, Nanotechnology 17 (2006, at press).
3:30 PM - **AA2.4
Mesocrystals from Peanut- and Mushroom Cap-shaped Colloids.
Ian Hosein 1 , Stephanie Lee 1 , Bettina John 1 , Michael Ghebrebrhan 2 , Fernando Escobedo 1 , John Joannopoulos 2 , Chekesha Liddell 1 Show Abstract
1 , Cornell University, Ithaca, New York, United States, 2 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
4:30 PM - **AA2.5
Exploring PbSe and PbTe Nanocrystal (Quantum Dot) Superlattices for 3D electronics and photonics.
Christopher Murray 1 2 , Dmitri Talapin 1 3 , Jeffrey Urban 1 4 Show Abstract
1 Chemistry & Materials Science, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 2 Nanoscale Materials & Devices, IBM T. J. Watson Research Center, Yorktown Heights, New York, United States, 3 The Molecular Foundry, Lawrence Berkeley National Labs, Berkeley, California, United States, 4 Chemistry, Michigan State University, Lansing, Michigan, United States
The electronic and optical tunability of semiconductor nanocrystals (quantum dots) motivates their use in the design new materials and assembly of new devices. This talk will focus on the interesting superlattice systems that can be built with these nanoscale building blocks. Monodisperse nanocrystals self-organize during controlled evaporation to produce 2D and 3D superlattices (colloidal crystals, opals) with relatively simple close-packed structures. The superlattices retain and enhance many of the desirable mesoscopic properties of individual nanocrystals and are now permitting the systematic investigation of new collective phenomena. Specifically recent results on the formation of PbSe and PbTe quantum dot solids will be emphasized. Initially insulating PbSe, and PbTe, and PbS nanocrystal solids (quantum dot arrays, superlattices) can be chemically “activated” to fabricate n- and p-channel field effect transistors (FETs) while retaining the size quantization photonic effects prized in the constituent building blocks. Chemical treatments engineer the interparticle spacing, electronic coupling and doping in the films while simultaneously passivating electronic traps. The electronic performance of these nanocrystal FETs’ compares favorably with more mature organic transistors and provides complimentary circuit (CMOS) options that could enable a range of low cost, large area electronic, optoelectronic, thermoelectric, and sensing applications.
5:00 PM - **AA2.6
Electric Field Driven Assembly of Anisotropic Colloidal Particles into Two-Dimensional and Three-Dimensional Crystals of Unusual Symmetry
Orlin Velev 1 , Olivier Cayre 1 , Sumit Gangwal 1 , Amit Goyal 1 , Carol Hall 1 Show Abstract
1 Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States
We have shown earlier that dielectrophoresis (DEP), particle interactions driven by external AC fields, can be used for the reversible on-chip assembly of extraordinarily large, switchable 2D crystals from colloid microspheres. We will demonstrate here how a much richer variety of crystals, 2D and 1D arrays can be assembled by electric fields acting on particles of anisotropic charge distribution and/or polarizability. Methods for fabrication of such advanced particles have been developed by our group and others and many new types of particles are likely to be synthesized in the near future. First, we will present the specifics of DEP-driven assembly of 2D crystals from metallo-dielectric particles. These particles demonstrate numerous field-driven physical effects. At higher frequencies the particles assemble into 2D crystals of various symmetries, where each particle is oriented such that the conductive parts of the nearby particles are also organized in lines. Such long ranged metallo-dielectic arrays can find applications both in photonics and electronics. At lower frequencies the motion and interactions of the particles are governed by AC electrohydrodynamics acting in the areas of high field gradient at the interface between the two particle hemispheres of different polarizability. In the last part of this talk we will discuss theoretical strategies for electrostatic assembly of microspheres with permanently embedded dipoles. We use computer simulations to explore the dynamics of assembly and the structure of systems from dipolar colloids. Discontinuous molecular dynamics (DMD) simulations demonstrate how the dipolar particles self-assemble into a variety of microstructures ranging from nematic or smectic liquid crystals, to face centered cubic, hexagonally close packed and body centered tetragonal crystals, to open networks (gels) of cross-linked particle chains. The phase diagram of this system will be discussed in view of the use of such directed self-assembly processes for the formation of photonic and "smart" materials.
5:30 PM - AA2.7
Synthesis and Optical Properties of Long Chains of Coupled Spherical Microcavities
Andrey Kapitonov 1 , Vasily Astratov 2 1 Show Abstract
1 Center for Optoelectronics and Optical Communications, University of North Carolina at Charlotte, Charlotte, North Carolina, United States, 2 Department of Physics and Optical Science, University of North Carolina at Charlotte, Charlotte, North Carolina, United States
Self-assembly of colloidal particles is widely used in the synthesis of photonic microstructures. Colloidal photonic crystals1 are formed from relatively small nanospheres. Whispering gallery modes (WGMs) develop in microspheres as large as several wavelengths of light. It was predicted recently2 that spherical cavities arranged as a linear chain can provide optical transport in two different ways: (i) tight-binding between WGMs, (ii) as a result of focusing produced by cavities operating as a series of periodically coupled microlenses. In the latter case each microsphere produces a focused spot termed the “photonic nanojet”,2 with elongated shape and subwavelength lateral size. In a chain of spheres such nanojets result in periodical modes, called nanojet-induced modes (NIMs)3. The properties of NIMs are different from WGMs since they are not resonant modes.Linear arrays of monodisperse (~3%) polystyrene spheres with mean diameters 1.9, 2.2, 2.9, 5.0, and 10.1 micron were deposited on glass substrates by using a technique of self-assembly directed by micro-flows of water suspension of spheres. In our synthesis the “pinning” points forming pipe-like flows were nucleated by the spheres of larger size. With water evaporating, these pipe-like flows gradually shrink reaching the size of an individual sphere in cross-section, causing the formation of long chains consisting of tens of touching microcavities.To couple light to the arrays of microcavities we locally excited several fluorescent microspheres in the same chain. We directly observed the formation and propagation of NIMs by means of the scattering imaging technique. In the first several spheres apart from the emission source, high mode conversion losses occur. This is accompanied by the gradual tapering of the beam profile and the formation of the photonic jets at the interfaces of the spheres. At longer distances from the source the losses decrease. We observed attenuation as small as 0.5 dB per sphere. Intrinsic radiation loss of NIMs can be even smaller, because in our samples they are masked by the structural imperfections, e.g., slight deviations from the coaxial alignment of cavities.References:1. V. N. Bogomolov, S. V. Gaponenko, I. N. Germanenko, A. M. Kapitonov, E. P. Petrov, N. V. Gaponenko, A. V. Prokofiev, A. N. Ponyavina, N. I. Silvanovich, and, S. M. Samoilovich, Phys. Rev. E. 55, 7619 (1997).2. Z. Chen, A. Taflove, and V. Backman, Opt. Lett. 31, 389 (2006). 3. A. M. Kapitonov and V. N. Astratov, Opt. Lett. – accepted.
Paul V. Braun University of Illinois, Urbana-Champaign
Shanhui Fan Stanford University
Andrew J. Turberfield University of Oxford
Shawn-Yu Lin Rensselaer Polytechnic Institute
AA3: Colloidal Self-Assembly II
Wednesday AM, April 11, 2007
Room 2022 (Moscone West)
9:30 AM - **AA3.1
Opal-templated Structures for Nanophotonics: Photonic Crystals and Glasses.
Cefe Lopez 1 Show Abstract
1 , Instituto deciencia de Materiales de Madrid, Madrid Spain
10:00 AM - AA3.2
A Spin-Coating Technological Platform for Large-Scale Fabrication of Colloidal Photonic Crystals and Nanostructured Materials.
Peng Jiang 1 Show Abstract
1 Chemical Engineering, University of Florida, Gainesville, Florida, United States
A versatile spin-coating technique for assembling wafer-size colloidal photonic crystals, along with a large variety of functional nanostructured materials has been developed. The methodology is based on shear-aligning concentrated colloidal suspensions using standard spin-coating equipment. It enables large-scale production of both 3D and 2D non-close-packed colloidal crystals as well as a wide range of nanostructured materials including 3D ordered polymer nanocomposites, macroporous polymers, periodic nanohole arrays, metallic surface gratings, attoliter microvial arrays, 2D magnetic nanodots, and more. Most importantly, the new technological platform is compatible with standard semiconductor microfabrication, enabling parallel production of micropatterns for potential device applications. The spin-coating process also provides a new route to study the fundamental aspects of shear-induced crystallization, melting and relaxation. The shear flow in the spin-coating process is inherently non-uniform. The effect of non-uniform shear on the order-disorder transition and the microstructure of colloids, a topic that has received little or no attention, will be described.
10:15 AM - AA3.3
Characterization of 3D Photonic Colloidal Crystals by Microradian X-ray Diffraction and Quantitative 3D Microscopy.
Job Thijssen 1 , Andrei Petukhov 2 , Dannis Hart 1 , Arnout Imhof 1 , Alfons Blaaderen 1 Show Abstract
1 Soft condensed matter, Utrecht University, Utrecht Netherlands, 2 Van’t Hoff laboratory, Utrecht University, Utrecht Netherlands
10:30 AM - AA3.4
Full processing of Colloidal Photonic Crystals by Spin-Coating.
Hernan Miguez 1 , Agustin Mihi 1 , Gabriel Lozano Barbero 1 , Manuel Ocana 1 , Raul Pozas 1 Show Abstract
1 Institute of Materials Science of Seville, Spanish Research Council, Sevilla Spain
AA4: Direct Writing of 3D Photonic Crystals
Wednesday PM, April 11, 2007
Room 2022 (Moscone West)
11:15 AM - **AA4.1
Three-dimensional Photonic Crystals via Direct Laser Writing and Silicon Double Inversion.
Martin Hermatschweiler 1 2 3 , Michael Thiel 1 2 3 , Geoffrey Ozin 4 , Georg von Freymann 1 2 3 , Martin Wegener 1 2 3 Show Abstract
1 Institut fuer Angewandte Physik, Universitaet Karlsruhe (TH), Karlsruhe Germany, 2 DFG-Center for Functional Nanostructures, Universitaet Karlsruhe (TH), Karlsruhe Germany, 3 Institut fuer Nanotechnologie, Forschungszentrum Karlsruhe, Karlsruhe Germany, 4 Department of Chemistry, University of Toronto, Toronto, Ontario, Canada
11:45 AM - AA4.2
Inverse Woodpile Structure with a Large Photonic Band Gap.
Florencio Garcia-Santamaria 1 2 4 , Mingjie Xu 1 3 , Jennifer Lewis 1 2 3 , Paul Braun 1 2 4 Show Abstract
1 Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 2 Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 4 Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 3 Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
The fabrication of structures with a large complete photonic band gap (cPBG) has become the goal of numerous researchers since the concept was introduced two decades ago. Although cPBGs with theoretical relative widths below 5% can be adequate for some purposes, structures with narrow gaps might be unpractical for realistic applications. For example, structural defects may reduce the size, or even close, photonic gaps by introducing unwanted modes into the band structure. Here, we report the fabrication and optical and structural characterization of a germanium inverse woodpile structure with a robust 25% wide cPBG, centered around 6 µm, obtained from woodpile structures prepared by direct writing with a polymeric-ink. The photonic response has been maximized by tuning the filling fraction in accordance to the theoretical predictions. The reflectance spectrum from the sample shows a large reflectance peak in the middle infrared as predicted by the band structure.Due to its low filling ratio, this inverse configuration allows opening larger cPBGs at shorter wavelengths than the direct woodpile. In principle, the procedures that will be shown here can be applied to woodpile templates fabricated with other methods such as laser-writing and e-beam lithography.These interconnected, hollow structures may find applications not only as photonic devices but also as low-cost MEMs, microfluidic networks for heat dissipation and biological devices.
12:00 PM - AA4.3
Sol-Gel Inks for Direct-Write Assembly of 3D Micro-Periodic Photonic Crystals
Eric Duoss 1 , Mariusz Twardowski 1 , Jennifer Lewis 1 Show Abstract
1 Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
We have pioneered an innovative approach for the fabrication of 3D micro-periodic photonic crystals (PCs), known as direct ink writing (DIW). In this method, a micro-capillary nozzle is mounted to a 3-axis nano-positioning robotic stage that is controlled via a computer-aided design (CAD) program. Paramount to our approach is the creation of inks that flow through these fine deposition nozzles as continuous filaments, and then rapidly solidify to maintain their shape even as they span gaps in the underlying layer(s). An inherent advantage of the DIW process over other PC assembly techniques is the ease to which functional defects can be engineered into the crystalline structure. DIW enables precise control of point and waveguide defects simply by initiating and terminating ink flow at designated locations in the lattice. Using titania-based sol-gel inks, functional face-centered tetragonal woodpile structures with feature sizes of ~500 nm have been patterned and directly converted to the anatase phase of titania by thermal annealing. The resultant structures have been explored as potential photonic crystals due to the high refractive index of anatase titania (nanatase ~ 2.5) and its transparency in the near infrared (IR) spectral region. The anatase woodpile structures exhibit a partial photonic bandgap with a reflectivity of up to 92% in the near IR. We are now creating tin-doped titania-based inks in order fabricate rutile PCs. Rutile has a higher refractive index (nrutile ~ 2.7) than anatase and therefore leads to a wider photonic bandgap. Tin-doping is known to suppress the large grain growth normally encountered during thermal conversion of undoped inks. Reflectivity measurements will be carried out on 3D PCs patterned with embedded defects from tin-doped titania inks.
12:15 PM - **AA4.4
Two-Photon 3D Micro- and Nano-Fabrication with Polymer, Metal Nanocomposite and Hybrid Materials.
Joseph Perry 1 , Wenting Dong 1 , Vincent Chen 1 , Wojciech Haske 1 , Jian Zhou 1 , Yiqing Wang 1 , Uwe Bunz 1 , Stephen Barlow 1 , Seth Marder 1 Show Abstract
1 School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, United States
Two-photon microfabrication is becoming an increasingly important method for the creation of three-dimensional microstructures. The method allows for the fabrication of 3D microstructures in a single coat, expose, and develop process cycle and without the use of masks, offering a low cost, environmentally friendly way to form complex 3D devices and structures. Efficient two-photon absorbing materials that allow for the fabrication of three-dimensional microstructures composed of polymeric, metallic, or hybrid titania-organic materials will be described. We have recently demonstrated the reliable fabrication of lines with a width of 85 ± 5 nm using 520 nm femtosecond pulse excitation and a two-photon absorber with a significant cross section at this wavelength. We will discuss a range of 3D microstructures that can be fabricated in various materials systems by two-photon lithography using a continuous wave mode-locked femtosecond laser for excitation, including microchain structures, photonic crystal structures, switchable photonic devices, and luminescent conjugated polymer microstructures.
12:45 PM - AA4.5
Direct Laser Writing of three-dimensional Nanostructures in As2S3 Photoresist.
Sean Wong 1 , Michael Thiel 2 , Alexandra Ledermann 2 , Geoffery Ozin 4 , Martin Wegener 1 2 3 , Georg von Freymann 1 2 3 Show Abstract
1 Institut fuer Nanotechnologie, Forschungszentrum Karlsruhe GmbH, Karlsruhe, Baden-Wuerttemberg, Germany, 2 Institut fuer Angewandte Physik, Universitaet Karlsruhe (TH), Karlsruhe, Baden-Weurttemberg, Germany, 4 Materials research group - Chemistry department, University of Toronto, Toronto, Ontario, Canada, 3 DFG-CFN, Universitaet Karlsruhe (TH), Karlsruhe, Baden-Weurttemberg, Germany
Arsenic trisulfide (As2S3) is a photosensitive inorganic glass that can function as a photoresist for the fabrication of three-dimensional (3-D) nanostructures via direct laser writing (DLW) . Its value as a photoresist derives from the absence of shrinkage, a high index of refraction (n = 2.45) and transparency down into the visible spectral range. In combination with a highly selective etch, As2S3 is perfectly suited for the fabrication of 3-D photonic crystals with a complete bandgap .Previously documented chemical formulations for negatively etching As2S3 have targeted the fabrication of thin two-dimensional structures [3,4]. These formulations are unsuitable for etching tall 3-D nanostructures with intricate features typical for photonic crystals.
Here, we present the development of a highly-selective amine formulation, which, in a single step, enables high aspect-ratio, free-standing 3-D nanostructures to be directly etched in As2S3 after DLW. To achieve this objective, we systematically adjust the steric and electronic properties of a prototype amine and measure the effect of these modifications on the etch rate and selectivity of the amine. This knowledge allows for the intentional design of an optimized amine etch, which facilitates the formation of a range of arbitrary free-standing 3-D nanostructures with feature sizes down to 170 nm. The samples fabricated along these lines are free of shrinkage with smooth and defect-free surfaces. Therefore, DLW in As2S3 followed by a single etching step provides an appealing strategy for manufacturing high structural and optical property photonic crystals with a full photonic bandgap.
 M. Deubel et al., Nature Mater. 3, 444 (2004)
 S. Wong et al., Adv. Mater. 18, 265 (2006).
 M. Vleck et al., J. Non-Cryst. Solids (1991), 197-138 (Pt.2), 1035-8
 A. Kovalskiy et al., J. Non-Cryst. Solids (2006) 352(6-7), 589-594
AA5: Photonic Crystal Devices
Wednesday PM, April 11, 2007
Room 2022 (Moscone West)
2:30 PM - **AA5.1
3D Photonic Crystals as Diffractive and Energy Selective Filter for Tandem Thin Film Solar Cells.
Ralf Wehrspohn 1 , Andreas von Rhein 1 , Andreas Bielawny 1 , Carsten Rockstuhl 2 , Falk Lederer 2 , Reinhard Carius 3 Show Abstract
1 Institute of Physics, University of Halle, Halle Germany, 2 Department of Physics,, University of Jena, Jena Germany, 3 Institute for Photovoltaics, Research Center Juelich, Juelich Germany
3:00 PM - AA5.2
Enhanced and Tailored Emission from Luminescent Three-Dimensional Ru(bpy)3(PF6)2 Inverse-Opal Photonic Crystals
Jyh-Tsung Lee 1 2 , Andrew Brzezinski 1 2 , Jason Slinker 3 , Pierre Wiltzius 1 2 , George Malliaras 3 , Paul. Braun 1 2 Show Abstract
1 Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 2 Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 3 Department of Materials Science and Engineering, Cornell University, Ithaca, New York, United States
Three-dimensional inverse opal structures, with various lattice constants, were made by infilling polystyrene colloid templates with luminescent Ru(bpy)3(PF6)2. Passive structures exhibiting photoluminescence and active organic light-emitting-diode structures, which additionally exhibit electroluminescence, have been prepared. Characterization includes scanning electron microscopy, visible and near infrared reflectance, and solid-angle-resolved spectroscopy. Results show angular emission profiles can be tailored via choice of lattice constant, which determines directions inside the crystal for which propagation of frequencies emitted from Ru(bpy)3(PF6)2 are either enhanced or suppressed. Suppressing propagation parallel to the device interface corresponds with enhancement of luminescent flux exiting the crystal.
3:15 PM - **AA5.3
Photonic Crystal Enhanced MEMS Infrared Emitters and Sensors.
Martin Pralle 1 , Irina Puscasu 1 , Anton Greenwald 1 , Andrew Oliver 1 , James Daly 1 , Edward Johnson 1 Show Abstract
1 , Ion Optics, Inc., Waltham, Massachusetts, United States
It has long been a goal of technologist to control the emissivity of surfaces thereby providing a pathway to high efficiency sources, better thermal management, and truly “black” surfaces. We have realized a structure that affords this level of control through the use of a unique 2D photonic crystal of air holes in a metal coated silicon medium. This structure transforms an otherwise infrared transparent material into a structure that vigorously absorbs infrared radiation at a discrete narrow band. As expected, when heated this material generates tuned narrowband IR radiation at wavelengths commensurate with the periodicity of the lattice. We have integrated this photonic crystal enhanced (PCE) technology into a MEMS thermal hot filament device to generate high efficiency wavelength specific narrow band infrared emitters. Early applications of the technology include nondispersive infrared (NDIR) sensors built directly on a silicon chip and high efficiency thermophotovoltaic energy conversion.
4:15 PM - **AA5.4
Tunable two-dimensional Photonic Crystal Microcavities in SOI.
Philippe Fauchet 1 Show Abstract
1 ECE, University of Rochester, Rochester, New York, United States
4:45 PM - AA5.5
All-optical Ultrafast Switching of Si Woodpile Photonic Band Gap Crystals.
Tijmen Euser 1 2 , Adriaan Molenaar 1 2 , Jim Fleming 3 , Boris Gralak 4 , Albert Polman 1 , Willem Vos 1 2 Show Abstract
1 , FOM-Institute for Atomic and Molecular Physics AMOLF, Amsterdam Netherlands, 2 , Complex Photonic Systems (COPS), MESA+, University of Twente, Enschede Netherlands, 3 , Sandia National Laboratories, Albuquerque, New Mexico, United States, 4 , Institut Fresnel, Marseille France
We present the first ultrafast all-optical switching measurements of 3D photonic band gap crystals. The high-quality Si woodpile crystals are homogeneously excited, and the large induced reflectivity changes are probed over an octave in frequency (including the telecom range) as a function of time. We observe unexpected non-monotonic physics: at short fs times, the photonic gap narrows due to a Kerr nonlinearity, followed at longer ps times by a blue-shift of the whole gap due to optically excited free carriers. Our results agree well to exact modal method calculations. Our experiments open up exciting opportunities in fundamental physics by ultrafast control of density of states. We also discuss possible applications with necessary experimental parameters. For further information, please visit www.photonicbandgaps.com
5:00 PM - AA5.6
Strong Light-Matter Interaction and Lasing in Semiconductor Nanowires
Lambert van Vugt 1 , Sven Ruhle 1 , Jonathan Palero 2 , Prasanth Ravindran 2 , Hans Gerritsen 2 , Laurens Kuipers 3 , Daniel Vanmaekelbergh 1 Show Abstract
1 Condensed Matter and Interfaces, Debye Institute, Utrecht University, P.O.Box 80000, 3508 TA Utrecht Netherlands, 2 Molecular Biophysics, Debye Institute, Utrecht University, Utrecht Netherlands, 3 Center for Nanophotonics, FOM-Institute AMOLF, Kruislaan 407, 1098 SJ Amsterdam Netherlands
Strong light-matter interaction in semiconductors is a highly researched topic due to its enticing prospects of room temperature Bose-Einstein condensation and low threshold polariton lasing.1 The strong coupling of photons with excitons causes the formation of composite quasiparticles in which the energy oscillates back and forth between the photon state and the exciton state with the Rabi frequency.2 These exciton-polaritons have a strongly modified dispersion which combines the properties of the photon (weak confinement, long coherence length) with that of the exciton (strong confinement, short coherence length). Studies of strong light-matter interaction are usually performed on so called microcavity structures where a layer containing the excitons is sandwiched between distributed Bragg mirrors which confine the optical field.3 In these structures confined exciton-polaritons, or cavity polaritons are formed which have, unlike photons, a finite ground state energy where spontaneous coherence can be obtained. The light emitted from such a macroscopically coherent state would also be coherent, hence the name polariton laser. We provide experimental results showing that ZnO nanowires act as cavities in which photon modes are confined in three dimensions. If the wires are highly excited with UV laser light, laser emission is obtained with a mode spacing dependent on the wire length.4 Under lower excitation conditions with NIR laser light (two photon excitation) or an electron beam these photon modes strongly couple to the excitons to form confined room temperature stable exciton-polaritons which display a record Rabi-splitting of up to 160 meV.5 Recently, Bose-Einstein condensation at 5K in a CdTe microcavity displaying a vacuum field Rabi splitting of 25 meV has been observed.6 Our finding of a room temperature stable Rabi splitting of up to 160 meV in ZnO nanowires makes them prime candidates for the observation of room-temperature spontaneous macroscopic coherence and polariton lasing.References:1 H. Deng, G. Weihs, D. Snoke, J. Bloch, and Y. Yamamoto, Proc. Natl. Acad. Sci. U. S. A. 100 (2003), p. 15318-15323.2 J. J. Hopfield, Phys. Rev. 112 (1958), p. 1555-1567.3 C. Weisbuch, M. Nishioka, A. Ishikawa, and Y. Arakawa, Phys. Rev. Lett. 69 (1992), p. 3314-3317.4 L. K. v. Vugt, S. Rühle, and D. Vanmaekelbergh, Nanoletters accepted (2006).5 L. K. v. Vugt, S. Rühle, P. Ravindran, H. C. Gerritsen, L. Kuipers, and D. Vanmaekelbergh, Phys. Rev. Lett. 97 (2006), p. 147401.6 J. Kasprzak, M. Richard, S. Kundermann, et al., Nature 443 (2006), p. 409-414. Corresponding Email adress: L.K.vanVugt@Phys.uu.nl
AA6: Holographically Defined Photonic Crystals I
Wednesday PM, April 11, 2007
Room 2022 (Moscone West)
5:15 PM - **AA6.1
Creating Functional Photonic Crystals by Multi-beam Interference Lithography.
Shu Yang 1 , Jun Moon 1 , Jin Seo 1 , Yongan Xu 1 , Wengtin Dong 2 , Joe Perry 2 , Ali Adibi 3 Show Abstract
1 Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 2 School of Chemistry and Biochemistry , Georgia Institute of Technology, Atlanta, Georgia, United States, 3 School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
5:45 PM - AA6.2
A Generic Holographic Methodology for Engineered Mesoscale Assembly of Nanoparticles over Macroscopic Size Scales.
John Busbee 1 2 , Lalgudi Natarajan 1 , Abby Griffith 2 , Paul Braun 2 , Rachel Jakubiak 1 , Vincent Tondiglia 1 , Richard Vaia 1 , Timothy Bunning 1 Show Abstract
1 Materials Directorate, Air Force Research Laboratory, Wright-Patterson AFB, Ohio, United States, 2 Materials Science and Engineering, University of Illinois, Urbana, Illinois, United States
Holographic polymer dispersed liquid crystals (HPDLC’s) have shown to be a promising avenue for the production of low-cost electrically switchable optical elements. Here, we modify this technique to include the addition of controlled amounts of functionalized nanoparticles. By carefully selecting the functionalization chemistry, the particles are reactively constrained into the polymeric domain, allowing modification of grating properties and enhancing the functionality of the device. Beyond 1-D gratings, other, higher dimensional structures have been fabricated, opening the possibility of engineered assembly and alignment of particle structures with feature sizes as small as 100 nm over macroscopic distance scales. The structures were fabricated using a simple system comprised of acrylate monomer and silica nanoparticles, with results extended to other polymeric systems and other nanoparticles, validating the technique as a generalized methodology for large scale assembly of particles sized from 6 to 200 nm.
AA7: Poster Session
Thursday AM, April 12, 2007
Salon Level (Marriott)
9:00 PM - AA7.1
Bragg Reflector Waveguide and Electro-Optic Modulator Based on Barium Titanate Thin Films.
Zhifu Liu 1 , Pao-Tai Lin 1 , Bruce Wessels 1 Show Abstract
1 Department of Materials Science and Engineering and Materials Research Center, Northwestern University, Evanston, Illinois, United States
Barium titanate (BaTiO3) is an excellent non-linear optical material with an extremely high electro-optic (EO) coefficient. A thin film BaTiO3 EO modulator with a >15GHz modulation bandwidth has recently been demonstrated. To enhance the modulation bandwidth, photonic crystal waveguides have been proposed. In this investigation, a Bragg reflector waveguide and EO modulator based on barium titanate platform were designed, fabricated and tested. The Bragg grating functions as a reflector for a specific wavelength, which satisfies the Bragg condition. By implementing a Bragg grating structure, the EO modulator’s driving voltage can be potentially lowered by an order of magnitude compared to that of a polarization intensity waveguide modulator since for the grating structure there is a strong dependence of transmission on wavelength. For 1.55μm wavelength, the Bragg feature is ~180nm for the Si3N4/ BaTiO3/MgO multi-layer thin film structure. To form Bragg waveguide structures, a 200-500nm thick, epitaxial thin film barium titanate layer was deposited on an MgO substrate by low pressure metalorganic chemical vapor deposition. A Si3N4 layer was subsequently grown on barium titanate by plasma enhanced chemical vapor deposition and patterned using photolithography to form the waveguide. Electron-beam lithography was used to define the grating. Since thin film barium titanate and MgO substrate are both insulating, during electron-beam writing there exists a strong electron charging effect in the high vacuum mode, resulting in distorted patterns. To eliminate the distortion, we have developed a process that uses low vacuum (~ 1 torr) for the electron-beam writing. Grating patterns were then formed by reactive ion etching the Si3N4 layer. To form an EO modulator, co-planar electrodes were deposited and patterned by using electron-beam evaporation and lift-off process.Grating patterns were successfully fabricated as shown in images by scanning electron microscopy. The transmission spectrum of the Bragg reflector waveguide was measured using a tunable infrared laser source. Bragg reflector waveguide spectrum exhibited a ~40% transmission decrease within a 6nm laser tuning range. For comparison, the transmission spectrum of a reference sample without Bragg reflectors was nearly wavelength independent within the tuning range of the laser. By applying an external voltage the effective refractive index can be changed as well as the resonance wavelength of the waveguide structure. Initial results for millimeter long Bragg reflector devices indicated that by operating at the mid-point of its transmission curve, a one-volt level driving voltage could be potentially achieved.
9:00 PM - AA7.10
A Novel Approach for Fabrication of Highly Ordered Colloidal Crystals using Fluorinated Solvent.
Satoshi Takeda 1 2 , Pierre Wiltzius 2 Show Abstract
1 , Asahi Glass Company, Yokohama Japan, 2 , Univ. Illinois at Urbana-Champaign, Urbana-Champaign, Illinois, United States
9:00 PM - AA7.11
Deterministically Generated Aperiodic Metal/Dielectric Structures for Large, Chip-scale Electric Field Enhancement Effects
Luca Dal Negro 1 , Ashwin Gopinath 1 , Ning-Ning Feng 1 , Mark Brongersma 2 Show Abstract
1 Electrical and Computer Engineering, Boston University, Boston, Massachusetts, United States, 2 Geballe Laboratory of Advanced Materials, Stanford University, Stanford, California, United States
The control of light-matter interaction in complex metal/dielectric structures without translational invariance offers the ultimate potential for the creation and manipulation of deep sub-wavelength light states. Unlike periodically arranged structures (photonic crystals), deterministically generated aperiodic (fractal) metal/dielectric photonic structures show unique light localization and transport properties. Based on a Finite-Difference-Time-Domain (FDTD) analysis, we report on surface plasmon-polariton (SPP) multiple scattering and electromagnetic coupling in two dimensional (2D) aperiodic arrays of metal nanoparticles. The arrays are generated by a 2D generalization of simple mathematical rules, such as Fibonacci, Thue-Morse or Rudin-Shapiro sequences, encoding a fascinating complexity. We show that, by combining easy SPP coupling and multiple scattering effects, aperiodic patterns of metal nanoparticles can give rise to strong SPP localization and field enhancement effects within deep sub-wavelength volumes (hot electromagnetic spots). The use of non-periodic, deterministic 1D and 2D metal nano-particle arrays represent a convenient approach to manipulate enhanced local fields on chip-scale devices which can have a large impact for active nanophotonics applications.
9:00 PM - AA7.12
Large Scale Fabrication of a 3-D Copper Woodpile Photonic Crystal in the Infrared Wavelengths.
Timothy Walsh 1 3 , Pei-I Wang 2 3 , Shawn-Yu Lin 2 3 Show Abstract
1 Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States, 3 Future Chips Constellation, Rensselaer Polytechnic Institute, Troy, New York, United States, 2 Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York, United States
In this project, a 6 layer copper woodpile photonic crystal structure was fabricated on 8 inch silicon wafers in the RPI Microfabrication Clean Room facility. Initial optical measurements show a reflection band edge at about 4.5μm which is independent of incidence angle. There is a transmission peak at about 3μm, which decreases as the incident angle increases but does not shift in wavelength. The thermal emission from the structure has also been studied. The emission spectrum is very sharp with a maximum at 3.3μm which is constant with sample temperature. The device shows good optical characteristics despite some misalignment and scale errors in the individual layers. The sharp thermal emission peak and possibility of large scale fabrication makes metallic photonic crystals an intriguing candidate to serve as a selective emitter in thermophotovoltaic (TPV) systems. The modified photonic density of states decreases the long wavelength tail of the emission while enhancing the emission at the photonic band edge. Calculations using the emission from a photonic crystal demonstrate improved TPV efficiency and high power density when a photovoltaic cell with a bandgap matched to the emission peak of the photonic crystal is used.
9:00 PM - AA7.13
Tunable Ferroelectric Photonic Crystals.
Oleg Aktsipetrov 1 , Tatyana Murzina 1 , Fedor Sychev 1 , Irina Kolmychek 1 Show Abstract
1 Department of Physics, Moscow State University, Moscow Russian Federation
9:00 PM - AA7.14
Development of 1-D Photonic Wire Composed of Hundreds of Polymeric Micro-spheres Fabricated by Self-organization Process.
Tadashi Mitsui 1 , Yutaka Wakayama 2 , Tsunenobu Onodera 3 , Hidetoshi Oikawa 3 , Hachiro Nakanishi 3 , Kazuaki Sakoda 1 , Nobuyuki Koguchi 1 Show Abstract
1 Quantum Dot Research Center, National Institute for Materials Science, Tsukuba, Ibaraki, Japan, 2 Advanced Electric Materials Center, National Institute for Materials Science, Tsukuba, Ibaraki, Japan, 3 Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi, Japan
We fabricated 1-Dimentional photonic wires by using self-organization technique in colloidal suspension, and successfully made a few millimeter-length 1-D wires composed of hundreds of polystyrene micro-spheres. The fabrication process was performed on an original substrate which is formed a metal thin-film on it. The metal thin-film has some groove pattern for drain. In addition, we developed an original cell for the process we called “horizontal capillary cell”. Since this horizontal capillary cell keeps the colloidal solution relatively long time, the self-organization process is slowly but accurately progress. We injected the colloidal suspension which includes the 2-micron diameter micro-spheres (NIST Traceable) with ultra micro-pipette. The scanning electron microscopy (SEM) images of the 1-D photonic wires indicate that those have a nearly straight structure with aligned micro-spheres of 2 or 3 lines. On the micro-spheres lines, second or third layers were formed with close-packed structure. Here, the wires have a pyramid-like cross-section. The two important point of our process is that we use a hydrophobic or an insufficient hydrophilic substrate, and the drain structure. Since this type substrate has weaker attraction of micro-spheres than the attraction among the hydrophilic micro-spheres, the most probable cause of this wire structure is self-organization during the very slowly drain process. Moreover, we will show the propagation light and its optical properties within the 1-D photonic wires by using guide-collection-mode near-field scanning optical microscopy [2-4]. T. Mukaiyama, K. Takeda, H. Miyazaki, Y. Jimba and M. Kuwata-Gonokami, Phys. Rev. Lett., Vol.82, (1999) pp. 4623-4626 T. Mitsui, Rev. Sci. Instrum., Vol.76, (2005) art.043703. T. Mitsui, Appl. Phys. Lett., Vol.87, (2005) art.141104. T. Mitsui, J. Appl. Phys., Vol.98, (2005) art.086113.
9:00 PM - AA7.15
Selective GaAs Quantum Dot Array Growth Using Dielectric and AlGaAs Masks Pattern-Transferred from Diblock Copolymer.
Joo Hyung Park 1 , Anish Khandekar 2 , Sang-Min Park 2 , Luke Mawst 1 , Thomas Kuech 2 , Paul Nealey 2 Show Abstract
1 Electrical and Computer Engineering, University of Wisconsin - Madison, Madison, Wisconsin, United States, 2 Chemical and Biological Engineering, University of Wisconsin - Madison, Madison, Wisconsin, United States
To reach the full theoretical potential advantages of ideal Quantum Dots (QDs) for diode lasers and photodetectors, elimination of the wetting layer, which is inherent to self-assembled QDs of Stranski-Krastnow (SK) growth mode, and achieving a uniform mono-modal QD size distribution is needed. The SK QD approach is complicated by the randomness of the QD size distribution and inherent presence of the wetting layer. These factors have been experimentally identified as the underlying cause for low optical gain and high temperature sensitivity in diode lasers. An alternate approach to QD formation is the use of nanopatterning with diblock copolymers combined with selective MOCVD growth. We utilize cylinder-forming PS-b-PMMA which have the ability of preserving the hole size through the pattern transfer procedures. The combination of diblock copolymer lithography with selective MOCVD growth of the QDs could lead to a higher degree of control over QD shape, size uniformity, and composition over the self-assembly process. Since the SK self-assembly process is not employed, the problematic wetting layer states are eliminated and improved optical gain can be expected. Control over the QD height, shape, and strain, also allows for the design of increased energy spacing between ground and excited QD states and hence a wider control or selection of the emission wavelengths. Since the QD strain is decoupled from the size, the process also has potential for achieving longer wavelength emission compared with SK QDs. On a GaAs substrate, hexagonally arranged uniform size QD arrays have been fabricated. The QD patterning is prepared by dense nanoscale diblock copolymer lithography, which consists of perpendicularly ordered cylindrical domains of polystyrene-block-poly (PS-b-PMMA) matrix. To transfer polymer patterns to QD arrays, two mask materials have been taken under consideration. Firstly, to characterize the profile and distribution of the QDs, a dielectric template mask was utilized and the polymer patterning is transferred on it. After the pattern transfer to the dielectric and subsequent removal of the polymer, single crystal GaAs QDs are selectively grown by MOCVD. SEM images indicate that the QD density is larger than 5×1010/cm2, comparable to SK growth mode and the size distribution peaks at a 12nm diameter. Finally, to grow QDs and subsequently cover the QDs in situ, an AlxGa1-xAs template mask is being investigated. After the pattern transfer to a 15nm thick AlGaAs template layer using RIE, the native oxide on the patterned AlGaAs surface acts as a selective growth mask for InAs QDs. After deposition of the QDs, capping layers can be grown on QDs without removing the sample from the reactor. We are currently investigating optimal growth conditions for covering the QDs and characterizing the photoluminescence. We gratefully acknowledges support from the ARO MURI W911NF-05-1-0262 (Dr. John Prater) and NSF NSEC DMR-0425880.
9:00 PM - AA7.16
Tungsten Inverse Opals for Modified Thermal Emission.
Sang Eon Han 1 , David Norris 1 Show Abstract
1 Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota, United States
Photonic crystals are solids that are three-dimensionally patterned on an optical length scale. Recent research has indicated that specific periodic structures can alter the thermal emission spectrum from metals. This may allow the elimination of unwanted heat from thermal emission sources, such as the tungsten filament in a conventional light bulb. Here, we study the possibility that tungsten photonic crystals obtained via self-assembly can exhibit modified thermal emission. These structures, known as inverse opals, are easy to fabricate. However, if their optical absorption is too high, the radiation does not “feel” the periodicity of the crystal and no modification will occur. To avoid this, we employed a systematic approach and simulated the optical properties of tungsten inverse opals. First, we derived an analytical expression for the absorption, which is determined both by the group velocity and the field distribution inside the structure. Second, we investigated the photonic bands of the inverse opal and found that the group velocity could be controlled by adjusting specific structural parameters. Third, we investigated the effect of the surface structure. For an experimentally realizable surface geometry, we determined the group of photonic bands that couples strongly to the incident beam. By exploiting these bands, we obtained the desired optical spectrum. In particular, our calculations show that tungsten inverse opals can have a very similar absorption spectrum in the near-infrared range to the tungsten woodpile structure, which has previously shown modified thermal emission.
9:00 PM - AA7.17
Laser Colloidal Gel Writing of Porous 3D Microstructures.
Matthew George 1 , Ali Mohraz 1 , Martin Piech 2 , Nelson Bell 2 , Jennifer Lewis 1 , Paul Braun 1 Show Abstract
1 Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 2 , Sandia National Laboratories*, Albuquerque, New Mexico, United States
9:00 PM - AA7.2
Controlled Defects Formation and Photoemission from Three Dimensional Optically Active Si & SiO2 Nanocavities and Microdisks.
Laxmikant Saraf 1 , Fung Ou 2 , Mark Engelhard 1 , Donald Baer 1 , Scott Lea 1 , Zheming Wang 1 Show Abstract
1 Environmental Molecular Sciences Lab, Pacific Northwest National Laboratory, Richland , Washington, United States, 2 , Rensselaer Polytechnic Institute , Troy, 12180, New York, United States
Controlled defects formation in silicon based nanostructures such as tuning of isolated nano-cavities with the knowledge of their optical and surface properties at desirable locations is extremely important in future photonics applications. In the same sense, precise micro-fabrication of silicon oxide microdisks frequently used in photonic structures like ring/disk resonators and waveguide couplers require ultra-low surface roughness to avoid unnecessary light scattering. In this study we discuss these issues through two sets of experiments. In the first part, an attempt to control the defects in silicon at desirable locations by using a combination of evolving hydrogen and optical lithography is discussed. In the second part, we study depth-dependent photoemission and high-resolution microscopy studies on smooth silicon oxide micro-disks and lateral nanotips, potentially used for light coupling. The primary origin of the defect craters is observed at silicon-hydrogen-electrolyte triple interface boundary. We also observe that the surface oxide strongly influences the photoemission properties. Photoemission studies indicate a complete depth dependent stoichometry in ordered oxide micro-disks and lateral nanotips with ~15 nm tip sharpness. These microdisks and nanotips are ideally suited for high-Q light trapping and waveguide coupling experiments. We conclude our discussion by describing future challenges and roles of rapid isotropic, anisotropic etching and dependence of etch rates on the quality of micro-fabricated photonic devices. References:Ou, Saraf, and Baer, “Applied Physics Letters”, 88(14):143113 (2006).Saraf, Baer, Wang, Young, Engelhard, and Thevuthasan. “Surface and Interface Analysis”, 37(6):555-561 (2005).Ou, Saraf, and Baer, ‘Proc. Mat. Res. Soc.’ Vol.829, B.9.27 (2004).Saraf, Young, Lea, Thevuthasan, Dunham, Grate, and Baer. “Electrochemical and Solid-State Letters” 7(1):C7-C9 (2004).Saraf, Engelhard and Lea, “Microelectronic Engineering”-submitted (2006).
9:00 PM - AA7.20
Tailoring the Morphology of White-Light Emitting ZnO Nanostructures
Rizia Bardhan 1 4 , Hui Wang 1 4 , Felicia Tam 2 4 , Naomi Halas 1 3 4 Show Abstract
1 Chemistry, Rice University, Houston, Texas, United States, 4 Laboratory for Nanophotonics, Rice University, Houston, Texas, United States, 2 Physics, Rice University, Houston, Texas, United States, 3 Electrical and Computer Engineering, Rice University, Houston, Texas, United States
ZnO is of great interest for photonic applications due to its wide band gap (3.37 eV) and large exciton binding energy (60 meV), and is a promising material for light emitting devices. The hexagonal wurtzite structure and polar crystal surface of ZnO makes it a promising candidate for fabricating novel nanostructures with unique morphologies. We have developed a facile, efficient, and controllable wet-chemistry approach to the fabrication of ZnO nanostructures with well-defined sizes and shapes. ZnO nanodonuts, nanobagels, nanobowls and nanoboats are fabricated by a one-pot synthesis at low temperature, by varying the concentration of zinc acetate dihydrate, while maintaining an acidic pH of ~ 5. These nanostructures not only have distinctive morphologies but also emit white light, via surface defect states, when excited above the bandgap energy. These structures may be useful in the development of economical, environmentally friendly nanophotonics devices and solid-state lighting sources.
9:00 PM - AA7.21
Controlled Modulation of Spontaneous Emission from Quantum Dots in Holographic Polymer Dispersed Liquid Crystals.
Abigail Griffith 1 , John Busbee 1 2 , Rachel Jakubiak 2 , Lalgudi Natarajan 2 , Vincent Tondiglia 2 , Congjun Wang 1 , Moonsub Shim 1 , Paul V. Braun 1 Show Abstract
1 1.Department of Materials Science and Engineering, University of Illinois, Urbana, Illinois, United States, 2 Materials Directorate, Air Force Research Laboratory, Wright-Patterson AFB, Ohio, United States
There has been significant interest in the use of holographic polymer dispersed liquid crystals (H-PDLC) as integrated optical elements, given that such elements are lighter and more compact then classical optical elements, and are also capable of multiplexing, which is not possible with classical optics. Here we demonstrate the controlled addition of functionalized quantum dots into H-PDLCs, resulting in a device with angular and electric field dependent spontaneous emission. The inherent switchable reflection Bragg grating present in the H-PDLC was created by holographic polymerization using an acrylate monomer and liquid crystal. ZnS capped CdSe nanocrystals were sequestered into the polymer regions of the 1-D grating via surface functionalization, thereby avoiding disruption of the switching characteristics of the liquid crystal. The device was fabricated so that the band edge of the photonic crystal was located at the emission wavelength of the nanocrystals. The observed spontaneous emission could be selectively enhanced or inhibited via the angle of measurement with respect to the periodicity and applied electric field.
9:00 PM - AA7.23
Large-Scale Photonic Crystal Circuit Design using Guided-Mode Scattering Matrices based on Photonic Wannier Functions.
Daniel Hermann 1 2 , Sergei Mingaleev 1 2 3 , Matthias Schillinger 1 2 , Patrick Mack 1 2 4 , Kurt Busch 1 2 Show Abstract
1 Institut für Theoretische Festkörperphysik, Universität Karlsruhe (TH), 76128 Karlsruhe Germany, 2 DFG-Forschungszentrum Center for Functional Nanostructures (CFN), Universität Karlsruhe (TH), 76128 Karlsruhe Germany, 3 Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine, 03143 Kiev Ukraine, 4 Institut für Nanotechnologie, Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft, 76021 Karlsruhe Germany
We present a guided-mode scattering-matrix approach  based on the expansion of electromagnetic fields in photonic Wannier functions  and demonstrate its applicability to large-scale photonic circuits composed of compact functional elements imprinted in Photonic Crystal (PC) structures [3,4]. Such PC circuits allow to miniaturize existing designs from conventional (fiber) optics and possibly open the way towards integrated all-optical devices. We discuss basic building blocks such as Mach-Zehnder interferometers and directional couplers as well as the influence of non-zero reflections at bends and waveguide transitions on the overall performance of the circuits. Furthermore, we investigate wavelength-flattening techniques and tunability options.References: S.F. Mingaleev et al., Opt. Lett. 28, 619 (2003) K. Busch et al., J. Phys. Cond. Mat. 15, R1233 (2003) S.F. Mingaleev et al., Opt. Lett. 29, 2858 (2004) Y. Jiao et al., Phot. Tech. Lett. 17, 1875 (2005)
9:00 PM - AA7.25
Spectroscopic Ellipsometric Study of Optical Transitions in Si Nanoclusters embedded in SiOx matrix
Rastogi Alok 1 , Seshu Desu 1 , Chandra Sharat 2 , L. Malhotra 2 Show Abstract
1 Department of Electrical and Computer Engineering, University of Massachusetts, Amherst , Massachusetts, United States, 2 Department of Physics, Indian Institute of Technology, New Delhi India
9:00 PM - AA7.26
Ion Beam Assisted Square Spiral Photonic Crystal Fabrication
Jason Sorge 1 , Michael Fleischauer 1 , Michael Brett 1 Show Abstract
1 Electrical & Computer Engineering, University of Alberta, Edmonton, Alberta, Canada
Square spiral photonic crystals, proposed by Toader and John1, are comprised of periodic arrays of cylindrical columns with periodic abrupt 90° changes in the column growth direction. These abrupt changes produce elbows which correspond to specified points in the three-dimensional diamond lattice, and are commonly referred to diamond:n photonic crystal structures based on the nth nearest neighbour lattice point between column arms. The diamond:n structures are characterized by four parameters: column separation, spiral pitch, column diameter, and column growth angle. These structures have been shown theoretically to have a moderately large three-dimensional relative bandgap of approximately 15% for a direct silicon diamond:1 structure and as much as a 24% for an inverse silicon diamond:5 structure. Silicon square spiral photonic crystals can be grown by a single step thin film deposition process known as glancing angle deposition (GLAD), which utilizes rotation of lithographically patterned substrates and advanced control algorithms to limit column broadening and bifurcation. Experimental realizations of the square spiral architecture have been reported with optical results showing a relative bandgap width of 10.9%2, although they only marginally resemble the optimal structure. This is largely due to films deposited at extreme incidence forming columns with angle β ≤ 60° relative to the substrate normal, which is a fundamental limitation for physical vapour deposited films. However the optimal diamond:1 and diamond:5 structures require angles of approximately 64° and 74° respectively. Ion bombardment has recently been reported as a technique which can be used to increase the column tilt angle in films grown at oblique angles3. We report the use of ion bombardment in combination with the traditional GLAD process as a means to increase the film growth angle and achieve film structures that more closely resemble the optimal diamond:1 structure and also present studies of the effect ion bombardment has on the microstructure of the isolated columns.1 O. Toader, and S. John, Phys. Rev. E 66, 016610(18) (2002)2 M.O. Jensen, and M.J. Brett, Optics Express 13, 3348-3354 (2005)3 I. Hodgkinson, and Q.H. Wu, Modern Phys. Lett. B 15, 1328-1331 (2001)
9:00 PM - AA7.27
Non-spherical Based Colloidal Crystals from Asymmetric-dimer Shaped Polymer Mesoparticles.
Ian Hosein 1 , Chekesha Liddell 1 Show Abstract
1 Materials Science & Engineering, Cornell University, Ithaca, New York, United States
9:00 PM - AA7.29
Optimization Study of a 3D Structured Normal Incidence Plasmon Coupler.
Amitabh Ghoshal 1 , Grady Webb-Wood 1 , Pieter Kik 1 Show Abstract
1 College of Optics and Photonics: CREOL & FPCE, University of Central Florida, Orlando, Florida, United States
Recent work in the field of plasmon nanophotonics has resulted in the successful fabrication of surface plasmon (SP) based optical elements such as waveguides, splitters, resonators and multimode interference devices. These elements enable the development of true plasmonic integrated circuits. An important challenge lies in the coupling of conventional far-field optics to such nanoscale optical circuits. Existing approaches generally use one and two dimensional grating patterns on metal surfaces, or individual nanostructures such as shaped apertures. This presentation discusses a plasmonic coupling device that makes use of structure optimization in three dimensions in order to maximize the far-field to near-field coupling efficiency. The coupler structure consists of an array of ellipsoidal silver nanoparticles embedded in SiO2 and placed near a silver surface. By tuning the shape and size of the particles in the array, the nanoparticle plasmon resonance can be matched with the incident light frequency. The resulting resonantly enhanced fields near the nanoparticles in turn excite surface plasmons on the metal film.We have performed Finite Integration Technique simulations of a plasmon coupler, optimized for operation at a wavelength of λ = 676 nm (corresponding to λSP = 440 nm). Clear trends in the coupling efficiency are observed as a function of particle aspect ratio, inter-particle spacing in the longitudinal direction (along the SP propagation direction), as well as array-film separation. At a fixed lateral spacing of 100 nm, optimum coupling is observed at a particle aspect ratio of 2.5, a particle-to-film distance of 70 nm, and a longitudinal spacing of 425 nm. Analysis of the frequency dependant electric field at different points in the simulation volume reveals the separate contributions of the particle and surface resonances to the excitation mechanism. A coupled oscillator model describing the nanoparticle and the metal film as individual resonators reproduces all the observed trends. Initial experiments on coupler structures fabricated via electron beam lithography will be presented.
9:00 PM - AA7.30
3D Metallodielectric Photonic Crystal Based on Gold Nanoshells.
Jin Hyoung Lee 1 , Wounjhang Park 1 Show Abstract
1 Electrical and Computer Engineering, University of Colorado, Boulder, Colorado, United States
We report the fabrication and optical characterization of metallodielectric photonic crystal in which gold nanoshells were self-assembled into a face-centered-cubic (fcc) close-packed structure. The gold nanoshell opal structure exhibited two main reflection peaks at 710 nm and 1240 nm. These two peaks were attributed to the complete 3D photonic band gap and (111) directional band gap, respectively, based on the theoretical photonic band calculation by finite-difference time-domain method. To further substantiate the assignment, we measured reflectivity at various incident angles and found the 710 nm peak did not shift while other peaks shifted according to the Bragg law. However, the gold nanoshell opal structures fabricated with gold nanoshells tend to exhibit only short-range order with a high density of defects. Highly ordered crystal structure using metal particles is known to be extremely difficult to make because of strong attractive force between particles and rough surfaces. To overcome these difficulties and improve our opal sample crystallinity, we introduced silica coating on gold nanoshell so that we can increase the stability of gold nanoshell and make the surface smooth. Silica coating was accomplished by using poly(vinylpyrrolidone) as a stabilizing and coupling agent. We successfully synthesized a smooth and uniform thin silica coating (~10 nm thick) on gold nanoshell of which core diameter was 418 nm and gold shell thickness 20 nm. These silica coated gold nanoshells were then self-assembled into a 3D photonic crystal structure using the forced sedimentation method. We obtained highly ordered gold nanoshell opal structures, which were directly confirmed by scanning electron microscopy. We investigated the optical properties of the opal samples by measuring the reflectivity spectrum. Reflectivity peaks occurred at 720 nm and 1000 nm which were attributed to the complete 3D photonic band gap and (111) directional band gap, respectively, based on the finite-difference time-domain simulations. We also synthesized gold nanoshells with different silica coating thicknesses while the size of gold nanoshell was kept the same. As the coating thickness was increased from 10 nm to 300 nm, the reflectivity peaks at 720 nm and 1000 nm were red-shifted to 1300 nm and 2330 nm, respectively. The observed shifts are due to the increase in lattice constant and agreed well with the theoretical predictions. The silica coating thickness also controls the volume fraction of gold inside opal sample and the distance between the nanoshells. Therefore, controlling the silica coating thickness provides a means to engineer the photonic band structure, absorption by gold and any plasmonic coupling between nanoshells that may exists. A detailed analysis on the optical properties of silica coated gold nanoshell opals will be presented at the conference.
9:00 PM - AA7.31
Multiphoton Fabrication of Structures with 85 nm Linewidths.
Vincent Chen 1 , Wojciech Haske 1 , Joel Hales 1 , Mariacristina Rumi 1 , Wenting Dong 1 , Stephen Barlow 1 , Seth Marder 1 , Joseph Perry 1 Show Abstract
1 Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, United States
Multi-photon absorption offers the unique capability of initiating a photochemical/photophysical reaction in a confined volume at the focus of an intense laser beam. The high spatial selectivity stems from the nonlinear intensity dependence of the absorption process, which is I2 in the case of two-photon absorption. Because the intensity depends on 1/z2, where z is the distance from focus, the excitation probability decreases rapidly (as 1/z4 for two photon absorption) with increasing z, and this provides the depth selectivity of the excitation. Two- and multi-photon excitation have been utilized in various fields such as three-dimensional microfabrication, optical data storage and biological imaging. In the field of 3D microfabrication, there has been a strong interest in reducing the feature size of the fabricated structures to afford smaller devices for microelectromechanical systems, visible to near-infrared wavelength photonic structures, and other applications.Here we report on the fabrication of microstructures with sub-100 nm linewidths by using a two-photon absorbing dyes with a maximum at short wavelengths. Previous work from our labs used two-photon dyes absorbing at 730 nm to write lines with widths as small as 200 nm, which is below the diffraction-limited resolution. We reasoned that by using shorter excitation wavelengths and suitable two-photon absorbing dyes, it should be possible to obtain smaller linewidths as a result of the wavelength scaling of the point-spread function. Cross-linked polymer lines were written in a fluid photosensitive resin by excitation with 520 nm femtosecond laser pulses at a repetition rate of 1 kHz. The pulses were focused into the sample using an objective with a numerical aperture of 1.4. The photosensitive resin consisted of a blend of triacrylate monomers along with 0.1 wt% of 4,4’-bis(di-n-butylamino)biphenyl (DABP), that exhibits sizable two-photon absorption in the region of 520 nm. Fabrication was performed using a computer-controlled 3D positioning stage to translate the sample. The sample was then washed to remove the underexposed resin.A power-dependent photo-induced polymerization study was carried out with DABP and E,E-1,4-bis[4-(di-n-butylamino)styryl]-2,5-dimethoxybenzene, that exhibits two-photon absorption at 730 nm. At exposure powers just above threshold, polymer features with linewidths of 85 ± 5 nm were obtained with 520 nm excitation and the DABP initiator, whereas the longer wavelength initiator gave a minimum linewidth of 200 ± 20 nm with 730 nm excitation. The two initiator systems exhibited comparable power thresholds of 0.85 and 0.90 μW, respectively. These results show that the 520 nm excitation system yielded a linewidth of wavelength/6, while the 730 nm system provided a width of wavelength/3.7. The factors controlling the linewidths in multiphoton fabrication, the dose dependence of the linewidths, and the comparative sensitivity of the absorbers will be discussed.
9:00 PM - AA7.32
Effect of Sulfide Ion in Electrolyte on the Ultrafast Carrier Dynamics of CdSe QDs Adsorbed on Nanostructured Inverse Opal TiO2 Films.
Lina Diguna 1 2 , Qing Shen 1 2 , Kenji Katayama 3 , Tsuguo Sawada 4 , Taro Toyoda 1 2 Show Abstract
1 Applied Physics and Chemistry, The University of Electro-Communications, Chofu, Tokyo, Japan, 2 Course of Coherent Optical Science, The University of Electro-Communications, Chofu, Tokyo, Japan, 3 Applied Chemistry, Chuo University, Bunkyo, Tokyo, Japan, 4 Chemical System Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo, Japan
The improvement of the performance of dye-sensitized solar cell (DSSC) must be achieved by considering the morphology of TiO2 film and the choice of sensitizers. Recently, inverse opal TiO2 has been proposed to enhance the light harvesting efficiency due to its large interconnected pores for better penetration of dye and photon confinement at wavelength near the photonic band gap for significant enhancement of dye absorption. On the other hand, narrow band gap semiconductor quantum dots (QDs) have attracted significant attention as light harvesters due to quantum confinement effect [1-3]. Regarding the initial process in photocurrent generation, the better understanding of photoexcited carrier dynamics is required to improve the performance of quantum dots sensitized solar cells. On the last report, the role of CdSe QDs interfaces in the carrier dynamics has been investigated for CdSe QDs adsorbed on inverse opal TiO2 films, while their measurement was done in air . However, practically this TiO2 films in DSSC are in contact with the electrolyte. Thus the carrier dynamics with the presence of electrolyte, especially in the solid-liquid junction, is necessary. In this study, ultrafast carrier dynamics of CdSe QDs adsorbed on nanostructured inverse opal TiO2 films with the presence of electrolyte were characterized using a lens-free heterodyne detection transient grating (LF-HD-TG) method, based on the change in the refractive index of the sample surface due to photoexcited carrier . The inverse opal TiO2 films were prepared by bottom-up method . CdSe QDs were adsorbed onto TiO2 films by a chemical deposition method . The photoexcited carriers decay was found to be affected by the presence of sulfide ion in electrolyte, especially for initial CdSe QDs adsorption time. Two exponential decays were observed for the measurement in air where the fast and slow decay are considered as the photoexcited hole and electron decay, respectively. However, single exponential decay, slow process relating to electron decay, was observed for the measurement in electrolyte. The disappearance of fast decay process may be due to another faster hole decay process than those observed without sulfide ion. This may be attributed by the role of sulfide ion as the hole scavenger. R. Vogel, K. Pohl, and H. Weller, Chem. Phys. Lett. 174 (1990) 241. L.M. Peter, D.J. Riley, E.J. Tull, and K.G.U. Wijayanta, Chem. Commun. 2002 (2002) 1030. Q. Shen and T. Toyoda, J. Photochem. Photobiol. A: Chem. 164 (2004) 75. L.J. Diguna, Q. Shen, A. Sato, K. Katayama, T. Sawada, and T. Toyoda, Mater. Sci. Eng. C (2006, in press). K. Katayama, M. Yamaguchi, and T. Sawada, Appl. Phys. Lett. 82 (2003) 2775. L.J. Diguna, M. Murakami, A. Sato, Y. Kumagai, T. Ishihara, N. Kobayashi, Q. Shen, and T. Toyoda, Jpn. J. Appl. Phys. 45 (2006) 5563. S. Gorer and G. Hodes, J. Phys. Chem. 98 (1994) 5338.
9:00 PM - AA7.33
Controlled Size and Shape of Three Dimensional Nano-ZnO Plates for UV- Absorption Application.
Taekon Kim 1 , Jae Seok Lee 1 , Arul Arjunan 1 , Rajiv Singh 1 Show Abstract
1 Materials science and engineering, University of Florida, Gainesville, Florida, United States
9:00 PM - AA7.34
Enhanced Optical Transmission through Periodic and Aperiodic Subwavelength Hole Arrays.
Domenico Pacifici 1 , Henri Lezec 1 2 , Harry Atwater 1 Show Abstract
1 Appl. Phys., California Institute of Technology, Pasadena, California, United States, 2 , Centre National de la Recherche Scientifique, Paris Cedex 16 France
9:00 PM - AA7.35
Surface Plasmon Dispersion Control in Metallodielectric Multilayers
Grady Webb-Wood 1 , Amitabh Ghoshal 1 , Pieter Kik 1 Show Abstract
1 CREOL/The College of Optics and Photonics, University of Central Florida, Orlando, Florida, United States
Surface plasmon are being studied intensively for use in a wide range of applications, including short-to-medium range optical data transport in high density integrated circuits, biosensing, and nanoscale focusing of light. In all these applications, control over the surface plasmon dispersion behavior is crucial. Recently is was shown theoretically that lossless metallodielectric multilayers can be used to generate unusual dispersive properties, including zero group velocity and negative group velocities. In this presentation we discuss the dispersive properties of surface plasmons on silver surfaces in the presence of a thin (0-20nm thick) silicon cover layer. At low frequencies, the surface plasmon modes are found to extend to beyond the silicon layer thickness, resulting in a high phase velocity. As the frequency is increased the plasmon wavevector increases and the spatial extent of the surface plasmon is reduced, resulting in more silicon-like dispersive behavior. The transition from air-like to silicon-like plasmon modes results in the appearance of zero group velocity modes as well as negative group velocity modes. Analytical calculations for this system including realistic losses show that by tuning the silicon layer thickness, zero group velocity can be obtained at wavelengths ranging from 380nm to 630nm. Under these conditions, typical damping times of a few optical cycles are obtained, showing potential for the use of the modes in the generation of localized resonances. Numerical simulations based on the Finite Integration Technique on such layered systems are presented. It is shown that local excitation by an oscillating dipole at frequencies around the zero group velocity point indeed results in the excitation of a plasmon wave packet that propagates with an apparent group velocity substantially lower than the speed of light. The effect of the cover layer thickness on the plasmon damping time will be discussed, and the potential for two-dimensional negative refraction using such layered structures is addressed.
9:00 PM - AA7.4
Thermally Stable Photoresists for Fabrication of 3D Photonic Crystals via Direct Laser Writing and Holography
Prashant Nagpal 1 , Yoonho Jun 1 , David Norris 1 Show Abstract
1 Chemical Engineering and Material Science, University of Minnesota, Minneapolis, Minnesota, United States
Three dimensional (3D) photonic crystals are structures that are periodic in all three directions on an optical length scale. Two powerful techniques for obtaining these materials are direct laser writing (DLW) and holography. Both utilize photopolymerization in a thin film of photoresist. In DLW, the focus of an infrared laser is moved to define the 3D photonic crystal structure. In holography, a 3D optical intensity pattern is created from the interference of four laser beams. However, both techniques are commonly used with conventional organic photoresists, which have low refractive index and low thermal stability. These properties can limit the usefulness of the photonic crystals that are obtained. To address this problem, here we demonstrate the use of methylsilsesquioxane (MSQ) as a thermally stable photoresist for DLW and holography. We synthesize oligomeric MSQ and use it in combination with diaryliodonium hexafluroantimonate salts as a photoinitiator and ITX as a sensitizer. DLW was then performed with a scanning confocal optical microscope and 750nm pulses from a Ti:Sapphire laser. 3D holograms were obtained using 355nm pulses from a Nd:YAG laser. The resulting structures were thermally stable at 550oC and could be infiltrated with silicon using chemical vapor deposition.
9:00 PM - AA7.5
Optical Phenomena in Synthetic Opal Photonic Crystals.
Kostyantyn Chayka 1 , Oleg Guziy 1 , Vasiliy Moiseyenko 1 Show Abstract
1 Optoelectronic department, Dnipropetrovsk National University, Dnipropetrovsk Ukraine
9:00 PM - AA7.6
Angular Dispersion of Photonic Pseudogap in Opal vs Inverse Opal.
Lay Kuan Teh 1 , Chee Cheong Wong 1 Show Abstract
1 School of Materials Science and Engineering, Nanyang Technological University, Singapore Singapore
We have recently achieved a non-dispersive photonic stop-band in the blue region near the L-point in the Brillouin Zone of electrodeposited ZnO inverse opal. As compared to its parent opal, the low energy photonic stop-band (pseudogap between the 2nd and 3rd band) of the inverse structure is ‘blue’-shifted, widened and remained fixed at its central frequency along different directions. The extensive spectral overlap of the stop-bands indicates a smooth angular dispersion approaching omni-directionality within a specific range of directions. Here, we present the calculated photonic bands along the LW direction in the fcc Brillouin Zone with the aim to investigate the difference in the angular dispersion of the photonic pseudogap between opal and inverse opal periodic structures. The results show that for the same refractive index contrast (RIC), the pseudogap in the inverse structure is widened and its central frequency remained relatively unchanged along different directions, in deviation to Bragg’s law. The width increases with the RIC while the angular dispersion is reduced, in agreement with our experiments. Further increase of the RIC above the threshold necessary to open up a complete photonic bandgap between the 8th and 9th band (RIC > 2.8 for fcc inverse opal) does not have significant effects on improving the omni-directionality. The results could be extended to make other inverse photonic structures of different symmetry with nondispersive bands for moderate RIC.
9:00 PM - AA7.7
Tunable Two Dimensional Nonlinear Photonic Crystal Waveguides
Pao Lin 1 , Zhifu Liu 1 , Bruce Wessels 1 Show Abstract
1 Material science & Engineering and Materials Research Center, Northwestern University, Evanston, Illinois, United States
Photonic crystal (PC) waveguides can potentially result in enhanced optical properties around critical points in the photonic band gap. Of interest here are enhanced nonlinear optical effects. In this study, two dimensional nonlinear PC waveguides were designed and fabricated using barium titanium oxide thin films as the active medium. Nonlinear PC waveguides made with barium titanate thin films potentially provide integrated devices with the advantages of wide tunability and high stability. Films 500 nm thick deposited on MgO substrates were utilized. Two dimensional PC structures were defined by the electron beam lithography or focused ion beams. Before patterning, a thin metal layer was deposited on the barium titanate layers in order to improve the conductivity of the samples. After writing the patterns, cylindrical air holes were generated in the thin film layers by wet etching. The PC lattice constant and the hole radius were selected in sub-micron region in order to satisfy the requirement of wave resonance. The PCs with sub-micron features were characterized by the atomic force microscopy, scanning electron microscopy, and near field optical microscopy. The transmission spectras of the PC waveguides were measured with a continuous wide band source that covered 1 to 2 micron wavelength. Simulations of the transmission characteristics were performed using the two dimensional finite difference time domain method (FDTD) and compared to experiments. Four types of monitors were used in the simulation that include: frequency domain, the time domain, the effective index domain, and the movie (continuous) monitor. The frequency domain monitors served as a spectrometer and provided the calculated transmission spectrum. The time monitors showed the spatial field profiles, and were used to trace the time dependent electro-magnetic field variation. The effective refractive index monitors were used to calculate the optical modes. The movie monitors provided the continuous wave propagation images which described the power flow.
9:00 PM - AA7.8
Photonic Crystal Structures of Biologic Origin: Butterfly Wing Scales.
Laszlo Biro 1 , Zsolt Balint 2 , Krisztian Kertesz 1 , Zofia Vertesy 1 , Geza Mark 1 , Levente Tapaszto 1 , Virginie Lousse 3 , Jean-Pol Vigneron 3 Show Abstract
1 Nanotechnology, Research Institute for Technical Physics and Materials Science, Budapest Hungary, 2 Lepidoptera Collection, Hungarian Natural History Museum, Budapest Hungary, 3 Solid State Physics Laboratory, Facultes Universitaires Notre Dame de la Paix, Namur Belgium
Many butterflies have beautifully colored wings. Some colors originate from pigmentation while others have structural origin. Blue and green are two typical colors in butterfly scales which usually are associated with structural color. Coloration is an important communication (sexual signaling: the chances to reproduce) and protective (cryptic color: the chances to survive) tool. Therefore, many millennia of evolution have generated well optimized structures: multilayers, diffraction gratings and photonic crystal type structures of high efficiency based on a relatively moderate refractive index contrast between chitin (n = 1.58) and air. In the present paper the photonic crystal type structures occurring in the scales of various butterflies are in the focus of attention. Their nanostructure, optical and thermal properties will be discussed with a particular emphasis on the degree of order in their photonic structures. Two butterflies with dorsal blue and ventral green colors are discussed in detail: the Cyanophrys remus, with metallic, blue colored single crystalline scales on its dorsal wing surface and polycrystalline ventral matt green surface  and the Albulina metallica, which has both its matt dorsal blue and ventral shiny green produced by quasi-ordered photonic crystal type structures .The natural photonic crystals optimized by evolution may provide useful “blueprints” for designing artificial structures and may hint to unexpected properties of photonic crystal type structures, like thermoregulation .This work was carried out with financial support from the EU through the EU6 NEST/PATHFINDER/BioPhot-01915 grant. K. Kertész, Zs. Bálint, Z. Vértesy, G. I. Márk, V. Lousse, J. P. Vigneron, M. Rassart, and L. P. Biró, Phys. Rev E. 74 (2006) 021922-1. L. P. Biró, K. Kertész, Z. Vértesy, G. I. Márk, Zs. Bálint, V. Lousse, J-P. Vigneron, Mat. Sci. Eng. C, in press. L. P. Biró, Zs. Bálint, K. Kertész, Z. Vértesy, G. I. Márk, Z. E. Horváth, J. Balázs, D. Méhn, I. Kiricsi, V. Lousse, and J.-P. Vigneron, Phys. Rev. E 67, (2003) 021907-1.
9:00 PM - AA7.9
Resonant Enhancement of Fluorescence from Quantum Dots on a Photonic Crystal Surface.
Nikhil Ganesh 1 2 , Wei Zhang 1 2 , Patrick Mathias 1 , Brian Cunningham 1 Show Abstract
1 Nano Sensors Group - Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 2 Department of Material Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Quantum Dots have rapidly emerged as an important class of nanomaterials that promise to revolutionize a wide range of nanotechnology-enabled fields. The unique optical properties of quantum dots combined with the ability to functionalize them has made them important candidates for light sources, solar cells, optical switches and fluorescent probes in sensitive biological assays.In this study, we report the initial efforts at enhancement of fluorescence emission from quantum dots on the surface of two-dimensional photonic crystal slabs. The enhancement of fluorescence is achieved by the combined development of high intensity near-fields (that serve to more efficiently excite the quantum dots) and strong coherent scattering effects (that result in enhanced extraction of the emitted fluorescence), attributed to leaky photonic crystal eigenmodes. By fabricating photonic crystal slabs that operate at visible wavelengths and engineering their leaky modes to provide an overlap with the absorption and emission wavelengths of the quantum dots, we realize an enhancement of over 107 times in fluorescence intensity from quantum dots on the photonic crystal surface. We believe our results to be important towards the realization of high brightness light sources, enhanced non-linear effects and lowering the detection limits in biological applications.
Paul V. Braun University of Illinois, Urbana-Champaign
Shanhui Fan Stanford University
Andrew J. Turberfield University of Oxford
Shawn-Yu Lin Rensselaer Polytechnic Institute
AA8: Holographically Defined Photonic Crystals II
Thursday AM, April 12, 2007
Room 2022 (Moscone West)
9:45 AM - **AA8.1
Conformable Phase Mask Techniques for Fabricating Three Dimensional Nanostructured Materials
John Rogers 1 Show Abstract
1 , University of Illinois, Urbana, Illinois, United States
Exposing a photopolymer to the distribution of intensity that develops when light passes through a conformable, subwavelength phase mask provides a flexible and experimentally simple route to wide ranging classes of periodic, aperiodic and graded three dimensional (3D) nanostructures. This talk will describe this fabrication technique, with rigorous coupled wave analysis and finite element modeling of the optics. Key features will be illustrated through the formation of 3D structures with a range of geometries and feature sizes (from 50 nm to microns) in thin (several microns) and thick (several hundred microns) formats, using both one photon and two photon effects. In addition, approaches will be introduced for the fabrication of continuous graded profiles in the structures, both in and out of the plane of the mask, through manipulation of the spatial and temporal coherence of the exposure light. Applications in areas ranging from nanostructured mixers and filters for microfluidics, to photonic bandgap materials to matrices for controlled chemical release will be presented.
10:15 AM - AA8.2
Direct Fabrication of 3D Ceramic Photonic Crystals Using Interference Lithography.
Matthew George 1 , Seokwoo Jeon 1 , Matthew Highland 1 , David Cahill 1 , John Rogers 1 , Paul Braun 1 Show Abstract
1 Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
11:00 AM - **AA8.3
Device Fabrication in High-Index 3D Photonic Crystals.
David Sharp 1 , Olivia Roche 1 , Jan Scrimgeour 1 , Christopher Blanford 2 , Robert Denning 2 , Andrew Turberfield 1 , Elton Graugnard 3 , Jeffrey King 3 , Christopher Summers 3 Show Abstract
1 Department of Physics, University of Oxford, Oxford United Kingdom, 2 Inorganic Chemistry Laboratory, University of Oxford, Oxford United Kingdom, 3 School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Holographic lithography (HL) is a flexible technique for the fabrication of three-dimensional (3D) photonic crystals with the submicron periodicity required for optical and near-IR applications. We demonstrate two key steps towards the creation of integrated optical devices based on waveguides and microcavities operating within a complete photonic band gap:1) infiltration of a holographically-defined polymeric 3D photonic crystal template with high-index dielectric by Atomic Layer Deposition (ALD);2) creation of localised structural defects embedded in, and in registration with, a 3D photonic crystal by direct two-photon laser writing .Structural and optical characterisation of TiO2 photonic crystals produced by infiltration and removal of the polymer template demonstrates the high quality of the negative replica. Structural characterisation of photonic crystals with embedded waveguide structures shows a faithful rendering of the designed structure in the developed polymer photonic crystal. The combination of these three techniques (HL, two-photon writing and ALD) maps out a clear route to device fabrication in high-index 3D photonic crystals.  J. S. King, E. Graugnard, O. M. Roche, D. N. Sharp, J. Scrimgeour, R. G. Denning, A. J. Turberfield and C. J. Summers “Infiltration and Inversion of holographically-defined polymer photonic crystal templates by atomic layer deposition”, Adv. Mater. 18, 1561 (2006). J. Scrimgeour, D. N. Sharp, C. F. Blanford, O. M. Roche, R. G. Denning and A. J. Turberfield “Three-dimensional optical lithography for photonic microstructures”, Adv. Mater. 18, 1557 (2006).
11:30 AM - AA8.4
Photo-initiation and Resist Optimization for 3-Dimensional Holographic Fabrication of Photonic Crystal Templates
Robert Denning 1 , Jared Lewis 1 , David Sharp 2 , Andrew Turberfield 2 , Harpal Bharaj 2 Show Abstract
1 Inorganic Chemistry Laboratory, Oxford University, Oxford United Kingdom, 2 The Clarendon Laboratory, Department of Physics, Oxford University, Oxford United Kingdom
In holographic exposures designed to fabricate 3-dimensional photonic crystals, the optical intensity varies smoothly across the unit cell: different parts of the developed structure therefore have different densities of photochemical cross-linkage. This is an important cause of resist shrinkage and pattern distortion. Moreover, structures with large intrinsic bandgaps at telecommunications wavelengths are not readily fabricated using familiar resist systems because these require photo-initiation by short wavelength sources. These two problems with current photoresists have seriously constrained the scope of the holographic method.We now report a study of solubility contrast as a nonlinear function of optical exposure for SU-8, an epoxy resist which is widely used for holographic lithography, and for two alternative photoresists that are candidates to replace it: a dendrimer based epoxy resist that we have synthesized, and a dendrimeric phenolic negative-tone resist that can be developed in aqeuous media. We also report developments designed to allow the use of longer exposure wavelengths that can generate structures with lattice parameters suitable for telecommunications applications. We have synthesized several conjugated carbazole-benzothiazole dyes designed to sensitize long-wavelength photo-acid generation: we report their luminescence and two-photon excitation spectra, as well as their acid-generation efficiencies and lithographic performance.
11:45 AM - **AA8.5
2D and 3D Interference Lithography for Photonics
Edwin Thomas 1 Show Abstract
1 MSE, MIT, Cambridge, Massachusetts, United States
This talk will address the design and fabrication of 2D and 3D photonic and phononic crystals. Designs are based on low order Fourier terms for connected solid - connected fluid (bicontinuous) structures. Fabrication is by multiple beam interference lithography as well as phase mask interference lithography. Both positive and negative resist platforms are utilized together with infiltration around the polymeric template to enlarge the available suite of material systems. Complete band gaps for light and sound are explored and the role of defects in localizing waves is illustrated.
12:15 PM - **AA8.6
Fabrication and Characterization of 3D Photonic Crystals
Pierre Wiltzius 1 2 Show Abstract
1 Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 2 Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Photonic crystals are materials that allow the manipulation of light in new and unexpected ways. Colloidal self-assembly and multi-beam interference lithography are great tools to build crystals with interesting optical properties. Recent progress on making large area single crystals will be discussed. The fabrication of high index of refraction contrast photonic crystals is of particular interest. In addition, optical characterization of these microstructured materials and some device applications using photonic crystals will be presented.
12:45 PM - AA8.7
Fabrication of Three-dimensional Silicon-air Photonic Crystals with Embedded Defects using Multi–beam Holography.
Vinayak Ramanan 1 , Erik Nelson 1 , Andrew Brzezinski 1 , Paul Braun 1 2 , Pierre Wiltzius 1 2 Show Abstract
1 Materials Science and Engineering, University of Illinois, Urbana-Champaign, Urbana, Illinois, United States, 2 Beckman Institute, University of Illinois, Urbana-Champaign, Urbana, Illinois, United States
AA9: Lithographically Fabricated Photonic Crystals
Thursday PM, April 12, 2007
Room 2022 (Moscone West)
2:30 PM - **AA9.1
Present Status of Semiconductor 3D Photonic Crystals.
Susumu Noda 1 Show Abstract
1 Department of Electronic Science and Engineering, Kyoto University, Kyoto Japan
In this presentation, I will talk about the present status of semiconductor-based 3D photonic crystals. The 3D photonic crystals have a stacked-stripe (or wood-pile) structure , which is a diamond-like structure. First of all, I will discuss light emission control  by the 3D photonic crystals, where light emitters and artificial defects are introduced into the crystals and their characteristics are investigated. Then, I will discuss light propagation control, where horizontal [3, 4] and vertical  waveguides are introduced into the 3D crystals and their characteristics are investigated. Finally, I will describe a new fabrication method of the stacked-stripe 3D crystal, which is based on a double-angled etching method combined with a wafer fusion technique . References:  S. Noda, et al, Science, 289 (2000) 604.  S. Ogawa, et al, Science, 305 (2004) 227.  M. Imada, et al, Appl.Phys.Lett., 88 (2006) 171107.  S. Kawashima, et al, Optics Express, 13 (2005) 9774.  Kawashima, et al, unpublished.  S. Takahashi, et al, Appl.Phys.Lett., 89 (2006) 123106.
3:00 PM - AA9.2
Characterization and Tuning of Visible Frequency 3-D Photonic Crystals Fabricated by Nanolithography
Yun-Ju Lee 1 , Ganapathi Subramania 1 , Igal Brener 1 , Ting Luk 1 , Paul Clem 1 Show Abstract
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States
3-D photonic crystals with complete photonic band gaps in the visible frequency range are promising candidates for compact light manipulation devices, with potential applications in areas such as lasing, sensing, and solid state lighting. By scaling down existing e-beam nanolithography technique, we have successfully fabricated titania woodpile lattices with band gap in the visible range. Here, we describe the characterization of these 3-D photonic crystals, as well as the tuning of their optical response by varying the fabrication parameters. Reflectance spectra of the woodpile lattices were measured by microspot spectroscopy, and the spectra exhibited very good agreement with features in the photonic band structure calculated by plane wave expansion. The directionality of the photonic band gap was determined by varying the numerical aperture of the focused microspot, which showed a weak dependence of peak shape to numerical aperture, suggesting that the band gap complete. The c/a ratio of the woodpile unit cell was varied by modifying the line width during the e-beam nanolithography step, and the differences in their optical response were matched to theoretical calculations. Finally, the amorphous titania woodpile lattices were successfully converted to anatase and rutile phases following thermal annealing, as determined by x-ray diffraction and ellipsometry. The relatively small shifts in the reflectance spectra were explained by the shrinkage of the lattice parameter during titania crystallization. Other relevant results and possible future directions will also be discussed.
3:15 PM - **AA9.3
Tailored Thermal Emission From Metallic Photonic Crystals Fabricated by Soft Lithography.
Jae-Hwang Lee 1 2 , Yong-Sung Kim 1 2 , Kristen Constant 3 1 , Kai-Ming Ho 1 2 Show Abstract
1 , Ames Laboratory-U.S. DOE, Ames, Iowa, United States, 2 Department of Physics and Astronomy, Iowa State University, Ames, Iowa, United States, 3 Department of Materials Science and Engineering,, Iowa State University, Ames, Iowa, United States
We will report on observation of highly enhanced thermal radiation in a tailorable range of frequencies from metallic photonic crystals fabricated by an economical non-photolithographic method. Our fabrication can achieve highly-layered full 3D metal photonic crystals with excellent structural fidelity using a combination of soft lithography  and electrodeposition techniques. By adding a homogeneous monolithic backplane to the conventional woodpile structure, the difficulty of alignment in layer-by-layer fabrication is alleviated, while preserving characteristic thermal emission behavior of full 3D metallic photonic crystals. With proper design, such structures can yield highly polarized thermal emission at characteristic designable frequencies.  Xia, Y. & Whitesides, G. M. Soft lithography. Annu. Rev. Mater. Sci. 28, 153-184 (1998).
3:45 PM - AA9.4
Multilayer 3-D Integration of Photonic Devices in Silicon.
Prakash Koonath 1 , Bahram Jalali 1 Show Abstract
1 Electrical Engineering, University of California, Los Angeles, Los Angeles, California, United States
AA10: Plasmonics and Metamaterials
Thursday PM, April 12, 2007
Room 2022 (Moscone West)
4:30 PM - AA10.1
Three-Dimensional Electromagnetic Metamaterials with Non-Maxwellian Effective Fields.
Jonghwa Shin 1 , Jung-Tsung Shen 1 , Shanhui Fan 1 Show Abstract
1 E. L. Ginzton Laboratory, Stanford University, Stanford, California, United States
Electromagnetic metamaterial systems have drawn much attention lately since they can possess electromagnetic properties not easily found in nature. However, it has been implicitly assumed that their long-wavelength behavior can always be described by effective macroscopic fields that follow Maxwell equations. Thus, the efforts so far have been on designing metamaterial systems possessing unusual effective electric permittivity and magnetic permeability. Here we report that this assumption is false—there exist entirely new classes of metamaterial consisting of several interlocking disconnected metal networks, for which the effective long-wavelength theory is local, but the effective field is non-Maxwellian, and possesses much more internal degrees of freedom than effective Maxwellian fields in a homogeneous medium. We present several examples of the new metamaterial and analyze their unusual properties with a new effective model as well as with numerical simulations.
4:45 PM - AA10.2
Plasmon-Controlled Luminescence of Silicon Quantum Dots.
Hans Mertens 1 , Julie Biteen 2 , Harry Atwater 2 , Albert Polman 1
1 Center for Nanophotonics, FOM Institute AMOLF, Amsterdam Netherlands, 2 , California Institute of Technology, Pasad