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Man Y, Boechler N, Theocharis G, Kevrekidis PG, Daraio C. Defect modes in one-dimensional granular crystals. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 85:037601. [PMID: 22587217 DOI: 10.1103/physreve.85.037601] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Indexed: 05/31/2023]
Abstract
We study the vibrational spectra of one-dimensional statically compressed granular crystals (arrays of elastic particles in contact) containing light-mass defects. We focus on the prototypical settings of one or two spherical defects (particles of smaller radii) interspersed in a chain of larger uniform spherical particles. We present a systematic measurement, using continuous noise, of the near-linear frequency spectrum within the spatial vicinity of the defect(s). Using this technique, we identify the frequencies of the localized defect modes as a function of the defect size and the position of the defects relative to each other. We also compare the experimentally determined frequencies with those obtained by numerical eigenanalysis and by analytical expressions based on few-site considerations. These approximate analytical expressions, based on normal-mode analysis, are found to be in excellent agreement with numerics for a wide range of mass ratios. We also observe that the experimentally measured frequencies of the localized defect modes are uniformly upshifted, compared to the numerically and theoretically predicted values.
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Affiliation(s)
- Y Man
- Graduate Aerospace Laboratories (GALCIT) California Institute of Technology, Pasadena, California 91125, USA
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52
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Use of attractive forces to create a self-assembled film of charged nano-particles with a controlled packing. Colloids Surf A Physicochem Eng Asp 2012. [DOI: 10.1016/j.colsurfa.2012.02.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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53
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Karenowska AD, Gregg JF, Tiberkevich VS, Slavin AN, Chumak AV, Serga AA, Hillebrands B. Oscillatory energy exchange between waves coupled by a dynamic artificial crystal. PHYSICAL REVIEW LETTERS 2012; 108:015505. [PMID: 22304269 DOI: 10.1103/physrevlett.108.015505] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2010] [Indexed: 05/31/2023]
Abstract
We describe a general mechanism of controllable energy exchange between waves propagating in a dynamic artificial crystal. We show that if a spatial periodicity is temporarily imposed on the transmission properties of a wave-carrying medium while a wave is inside, this wave is coupled to a secondary counterpropagating wave and energy oscillates between the two. The oscillation frequency is determined by the width of the spectral band gap created by the periodicity and the frequency difference between the coupled waves. The effect is demonstrated with spin waves in a dynamic magnonic crystal.
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Affiliation(s)
- A D Karenowska
- Department of Physics, Clarendon Laboratory, University of Oxford, OX1 3PU Oxford, United Kingdom.
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54
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Cai Z, Liu YJ, Leong ESP, Teng J, Lu X. Highly ordered and gap controllable two-dimensional non-close-packed colloidal crystals and plasmonic–photonic crystals with enhanced optical transmission. ACTA ACUST UNITED AC 2012. [DOI: 10.1039/c2jm34896a] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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55
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Yan D, Zhu J, Wu H, Yang Z, Qiu J, Song Z, Yu X, Yang Y, Zhou D, Yin Z, Wang R. Energy transfer and photoluminescence modification in Yb–Er–Tm triply doped Y2Ti2O7 upconversion inverse opal. ACTA ACUST UNITED AC 2012. [DOI: 10.1039/c2jm33418f] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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56
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Effect of pH on monolayer properties of colloidal silica particles at the air/water interface. Colloid Polym Sci 2011. [DOI: 10.1007/s00396-011-2553-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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57
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Mocanu A, Marculescu B, Somoghi R, Miculescu F, Boscornea C, Stancu IC. Fluorescence enhancement for the complex PAMAM–BSA in the presence of photonic crystal heterostructures. Colloids Surf A Physicochem Eng Asp 2011. [DOI: 10.1016/j.colsurfa.2011.10.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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58
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Tsuruoka T, Kumazaki S, Nawafune H, Akamatsu K. In Situ Generation of Silver Nanoparticles in Ion-exchangeable Polymer Photonic Crystals. CHEM LETT 2011. [DOI: 10.1246/cl.2011.1233] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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59
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Vasile E, Rusen E, Mocanu A, Patrascu M, Calinescu I. Polymer colloids and silver nanoparticles hybrid materials. Colloid Polym Sci 2011. [DOI: 10.1007/s00396-011-2530-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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60
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Diacon A, Rusen E, Mocanu A, Hudhomme P, Cincu C. Fluorescence properties of photonic crystals doped with perylenediimide. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:7464-7470. [PMID: 21604771 DOI: 10.1021/la200878b] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
This study aims to present the fabrication of colloidal photonic crystals (PC) with increased fluorescence properties. The use of a highly fluorescent perylenediimide derivate (PDI) during the soap-free emulsion polymerization of styrene-acrylic acid resulted in monodisperse core-shell particles which allowed the fabrication of PC films. The properties of the hybrid material were studied in comparison with hybrid materials obtained by impregnation of films with chromophore solutions. In both cases an increase of the fluorescence response was observed in addition to a blue shift for the PDI core particles, proving the incorporation of the dye inside the copolymer particles.
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Affiliation(s)
- Aurel Diacon
- Department of Polymer Science, University Politehnica of Bucharest, 149 Calea Victoriei, RO-010072 Bucharest, Romania
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61
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Deleuze C, Sarrat B, Ehrenfeld F, Perquis S, Derail C, Billon L. Photonic properties of hybrid colloidal crystals fabricated by a rapid dip-coating process. Phys Chem Chem Phys 2011; 13:10681-9. [PMID: 21552585 DOI: 10.1039/c0cp02517h] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The enhancement of the capillarity fabrication of well-ordered two-dimensional (2D) and three-dimensional (3D) opal photonic crystal is described herein. The quality enhancement and the reduction of the fabrication time are improved by using core@soft adhesive shell (Silica@PolyButylAcrylate) particles dispersed in an organic solvent with a high boiling point. The hybridization by an elastomeric corona polymer, grafted from the SiO(2) surface, has offered adhesive properties naturally tunable by changing the polymer state from a solvated to a dry one. Such properties involve drastic changes of the self-assembly behavior and qualities. Their use, as elementary building blocks, for colloidal crystal fabrication have required a high withdrawal rate (up to 4000 μm s(-1)), i.e. involving a three order of magnitude reduction in time compared to a classic vertical deposition method (1 to 10 μm s(-1)) and a good control/prediction of the coating thickness can be tuned by varying the withdrawal rate and the particle concentration. In addition, an analysis of the 2D synthetic iridescence of the hybrid photonic crystal was performed under white light, revealing the adhesive shell bridge influence on the dissipation energy of cracks linked to the crystal quality and the photonic properties.
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Affiliation(s)
- C Deleuze
- Université de Pau et Pays de l'Adour, IPREM/UMR 5254/Equipe de Physique et Chimie des Polymères, Hélioparc, 2 avenue Angot, 64053 Pau Cedex 9, France
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62
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Yoon SM, Lee J, Je JH, Choi HC, Yoon M. Optical waveguiding and lasing action in porphyrin rectangular microtube with subwavelength wall thicknesses. ACS NANO 2011; 5:2923-2929. [PMID: 21391706 DOI: 10.1021/nn200027x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Lasing action by planar-, fiber-, or ring-type waveguide has been extensively investigated with different types of microcavities such as thin films, wires, cylindrical tubes, or ribbons. However, the lasing action by sharp bending waveguide, which promises efficient interconnection of amplified light in the photonic circuits, remains unexplored. Here, we report the first observation of microcavity effects in the organic rectangular microtubes (RMTs) with sharp bends (ca. 90°) and subwavelength nanoscale wall thicknesses, based on single crystalline and themostable tetra(4-pyridyl)porphyrin (H(2)TPyP)-RMTs synthesized by the VCR process. A bright tip emission is observed from the sharp bending edges of a single RMT upon laser excitation, demonstrating a clear waveguiding behavior in RMT. The appearance of a peak from the (0-1) band at a threshold tube length and the gradual decrease of its full width at half-maximum (fwhm) suggest that amplification of spontaneous emission (ASE) is developed by stimulated emission along the walls of the RMTs. The ehancement of the ASE peak together with the narrowing of its fhwm over a threshold pump power and the tube size (width and length) dependence of the mode spacing strongly support vibronic lasing action in the RMTs. The stimulated emission by the subwavelength bending waveguide demonstrates that the organic RMTs can be applied as new building blocks for micromanipulation of optical path and amplification in the integrated circuits for efficient photonic devices.
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Affiliation(s)
- Seok Min Yoon
- Molecular/Nano Photochemistry & Photonics Lab, Department of Chemistry, Chungnam National University, 79 Daehak-Ro, Yuseong-gu, Daejeon 305-764, South Korea
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63
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Antos R, Veis M. Fourier factorization with complex polarization bases in the plane-wave expansion method applied to two-dimensional photonic crystals. OPTICS EXPRESS 2010; 18:27511-27524. [PMID: 21197026 DOI: 10.1364/oe.18.027511] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We demonstrate an enhancement of the plane wave expansion method treating two-dimensional photonic crystals by applying Fourier factorization with generally elliptic polarization bases. By studying three examples of periodically arranged cylindrical elements, we compare our approach to the classical Ho method in which the permittivity function is simply expanded without changing coordinates, and to the normal vector method using a normal-tangential polarization transform. The compared calculations clearly show that our approach yields the best convergence properties owing to the complete continuity of our distribution of polarization bases. The presented methodology enables us to study more general systems such as periodic elements with an arbitrary cross-section or devices such as photonic crystal waveguides.
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Affiliation(s)
- Roman Antos
- Institute of Physics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic.
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64
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Kang C, Phare CT, Vlasov YA, Assefa S, Weiss SM. Photonic crystal slab sensor with enhanced surface area. OPTICS EXPRESS 2010; 18:27930-27937. [PMID: 21197066 DOI: 10.1364/oe.18.027930] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
In this work, we demonstrate improved molecular detection sensitivity for silicon slab photonic crystal cavities by introducing multiple-hole defects (MHDs), which increase the surface area available for label-free detection without degrading the quality factor. Compared to photonic crystals with L3 defects, adding MHDs into photonic crystal cavities enabled a 44% increase in detection sensitivity towards small refractive index perturbations due to surface monolayer attachment of a small aminosilane molecule. Also, photonic crystals with MHDs exhibited 18% higher detection sensitivity for bulk refractive index changes.
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Affiliation(s)
- Christopher Kang
- Interdisciplinary Graduate Program in Materials Science, Vanderbilt University, Nashville, Tennessee 37235, USA.
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65
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Wang HP, Lai KY, Lin YR, Lin CA, He JH. Periodic si nanopillar arrays fabricated by colloidal lithography and catalytic etching for broadband and omnidirectional elimination of Fresnel reflection. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:12855-12858. [PMID: 20666420 DOI: 10.1021/la1012507] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Periodic Si nanopillar arrays (NPAs) were fabricated by the colloidal lithography combined with catalytic etching. By varying the size of colloidal crystals using oxygen plasma etching, Si NPAs with desirable diameter and fill factor could be obtained. The Fresnel reflection can be eliminated effectively over broadband regions by NPAs; i.e., the wavelength-averaged specular reflectance is decreased to 0.70% at wavelengths of 200-1900 nm. The reflectance is reduced greatly for the incident angles up to 70 degrees for both s- and p-polarized light. These excellent antireflection performances are attributed to light trapping effect and very low effective refractive indices, which can be modified by the fill factor of Si in the NPA layers.
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Affiliation(s)
- Hsin-Ping Wang
- Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, 106 Taiwan, ROC
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66
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Kim SG, Seo YG, Cho YJ, Shin JS, Gil SC, Lee WM. Optimization of Emulsion Polymerization for Submicron-Sized Polymer Colloids towards Tunable Synthetic Opals. B KOREAN CHEM SOC 2010. [DOI: 10.5012/bkcs.2010.31.7.1891] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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67
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Sirotkin E, Apweiler JD, Ogrin FY. Macroscopic ordering of polystyrene carboxylate-modified nanospheres self-assembled at the water-air interface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:10677-83. [PMID: 20423068 DOI: 10.1021/la1009658] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
We present results from an experimental study of ordering characteristics in monolayers of polystyrene nanospheres self-assembled at a water-air interface. We demonstrate that the interaction of spheres, governed by the dissemination of surface charge, leads to the formation of macroscopic close-packed ordered areas or "domains" with a well-defined orientation of the lattice axes over areas of 25 mm(2). It was found that by changing the surface chemistry of the spheres it is possible to modify the balance between the attractive and repulsive forces and thus to control the ordering characteristics. We implemented a model that simulates the process of self-assembly and examines the ordering characteristics for layers with different ratio between attractive and repulsive forces. A good qualitative agreement was found between the simulations and experiment. These studies are technologically relevant as a method of producing nanosphere templates for large area patterned materials.
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Affiliation(s)
- Evgeny Sirotkin
- School of Physics, University of Exeter, Exeter, EX4 4QL UK.
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68
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Liao G, Chen S, Quan X, Chen H, Zhang Y. Photonic crystal coupled TiO(2)/polymer hybrid for efficient photocatalysis under visible light irradiation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2010; 44:3481-3485. [PMID: 20387884 DOI: 10.1021/es903833f] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Inverse TiO(2) opal photonic crystal coupled TiO(2)/poly(3-hexylthiophene) (bilayer TiO(2)/P3HT) was structured on FTO substrate for efficient photocatalysis under visible light irradiation (lambda > 400 nm). We expected that the photocatalytic capability of this hybrid photocatalyst could be enhanced by the efficient visible light absorption owing to the photonic crystal structure and effective charge separation owing to the unique heterojunction built between TiO(2) and P3HT. The bilayer TiO(2)/P3HT photocatalyst was prepared first by depositing inverse TiO(2) opal on FTO substrate via replicating polystyrene opal, followed by spin coating a layer of TiO(2) nanoparticles on the inverse TiO(2) opal. The as prepared bilayer TiO(2) was modified by P3HT via dipping method. Environmental scanning electron microscopy (ESEM) images demonstrated that the as prepared photocatalyst was composed of inverse TiO(2) opal layer and TiO(2) nanoparticles layer. The UV-vis diffuse reflectance spectra showed that the optical absorption for bilayer TiO(2)/P3HT was more intensive than for pristine TiO(2) nanoparticle/P3HT (NP-TiO(2)/P3HT) in the range of 400-650 nm. The enhanced generation of photocurrent under visible light irradiation (lambda > 400 nm) was observed using the bilayer TiO(2)/P3HT. The results of photocatalytic experiments under visible light irradiation revealed that the pseudofirst-order kinetic constant of photocatalytic degradation of methylene blue using the bilayer TiO(2)/P3HT was 2.08 times as great as that using NP-TiO(2)/P3HT, showing the advantage of the unique structure in the bilayer TiO(2)/P3HT for efficient photocatalysis.
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Affiliation(s)
- Gaozu Liao
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education, China), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China
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69
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Teo EJ, Bettiol AA, Xiong B, Breese MBH, Shuvan PT. An all-silicon, single-mode Bragg cladding rib waveguide. OPTICS EXPRESS 2010; 18:8816-8823. [PMID: 20588726 DOI: 10.1364/oe.18.008816] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
In this paper, we demonstrate a direct method of fabricating an all-silicon, single-mode Bragg cladding rib waveguide using proton beam irradiation and subsequent electrochemical etching. The Bragg waveguide consists of porous silicon layers with a low index core of 1.4 that is bounded by eight bilayers of alternating high and low refractive index of 1.4 and 2.4. Here, the ion irradiation acts to reduce the thickness of porous silicon formed, creating an optical barrier needed for lateral confinement. Single-mode guiding with losses as low as approximately 1 dB/cm were obtained for both TE and TM polarization over a broad range of wavelengths from 1525 nm to 1625 nm. Such an approach offers a method for monolithic integration of Bragg waveguides in silicon, without the need for multiple processes of depositing alternating materials.
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Affiliation(s)
- Ee Jin Teo
- Centre for Ion Beam Applications (CIBA), Department of Physics, 2 Science Drive 3, National University of Singapore, 117542, Singapore.
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70
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Imura Y, Kawakami M, Morita C, Kawai T. Network of polystyrene particle strings fabricated using glass slide with hydrophobic and hydrophilic periodical patterns. Colloids Surf A Physicochem Eng Asp 2010. [DOI: 10.1016/j.colsurfa.2010.01.046] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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71
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Li X, Wang T, Zhang J, Yan X, Zhang X, Zhu D, Li W, Zhang X, Yang B. Modulating two-dimensional non-close-packed colloidal crystal arrays by deformable soft lithography. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:2930-2936. [PMID: 19715332 DOI: 10.1021/la9027018] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We report a simple method to fabricate two-dimensional (2D) periodic non-close-packed (ncp) arrays of colloidal microspheres with controllable lattice spacing, lattice structure, and pattern arrangement. This method combines soft lithography technique with controlled deformation of polydimethylsiloxane (PDMS) elastomer to convert 2D hexagonal close-packed (hcp) silica microsphere arrays into ncp ones. Self-assembled 2D hcp microsphere arrays were transferred onto the surface of PDMS stamps using the lift-up technique, and then their lattice spacing and lattice structure could be adjusted by solvent swelling or mechanical stretching of the PDMS stamps. Followed by a modified microcontact printing (microcp) technique, the as-prepared 2D ncp microsphere arrays were transferred onto a flat substrate coated with a thin film of poly(vinyl alcohol) (PVA). After removing the PVA film by calcination, the ncp arrays that fell on the substrate without being disturbed could be lifted up, deformed, and transferred again by another PDMS stamp; therefore, the lattice feature could be changed step by step. Combining isotropic solvent swelling and anisotropic mechanical stretching, it is possible to change hcp colloidal arrays into full dimensional ncp ones in all five 2D Bravais lattices. This deformable soft lithography-based lift-up process can also generate patterned ncp arrays of colloidal crystals, including one-dimensional (1D) microsphere arrays with designed structures. This method affords opportunities and spaces for fabrication of novel and complex structures of 1D and 2D ncp colloidal crystal arrays, and these as-prepared structures can be used as molds for colloidal lithography or prototype models for optical materials.
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Affiliation(s)
- Xiao Li
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, PR China
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72
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Chumak AV, Tiberkevich VS, Karenowska AD, Serga AA, Gregg JF, Slavin AN, Hillebrands B. All-linear time reversal by a dynamic artificial crystal. Nat Commun 2010; 1:141. [PMID: 21266991 PMCID: PMC3105294 DOI: 10.1038/ncomms1142] [Citation(s) in RCA: 145] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2010] [Accepted: 11/17/2010] [Indexed: 11/09/2022] Open
Abstract
The time reversal of pulsed signals or propagating wave packets has long been recognized to have profound scientific and technological significance. Until now, all experimentally verified time-reversal mechanisms have been reliant upon nonlinear phenomena such as four-wave mixing. In this paper, we report the experimental realization of all-linear time reversal. The time-reversal mechanism we propose is based on the dynamic control of an artificial crystal structure, and is demonstrated in a spin-wave system using a dynamic magnonic crystal. The crystal is switched from an homogeneous state to one in which its properties vary with spatial period a, while a propagating wave packet is inside. As a result, a linear coupling between wave components with wave vectors k≈π/a and k'=k-2π/a≈-π/a is produced, which leads to spectral inversion, and thus to the formation of a time-reversed wave packet. The reversal mechanism is entirely general and so applicable to artificial crystal systems of any physical nature.
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Affiliation(s)
- Andrii V Chumak
- Fachbereich Physik and Forschungszentrum OPTIMAS, Technische Universität Kaiserslautern, Kaiserslautern 67663, Germany.
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73
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Dechézelles JF, Aubert T, Grasset F, Cordier S, Barthou C, Schwob C, Maître A, Vallée RAL, Cramail H, Ravaine S. Fine tuning of emission through the engineering of colloidal crystals. Phys Chem Chem Phys 2010; 12:11993-9. [DOI: 10.1039/c0cp00129e] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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74
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Theocharis G, Kavousanakis M, Kevrekidis PG, Daraio C, Porter MA, Kevrekidis IG. Localized breathing modes in granular crystals with defects. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 80:066601. [PMID: 20365288 DOI: 10.1103/physreve.80.066601] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2009] [Indexed: 05/29/2023]
Abstract
We study localized modes in uniform one-dimensional chains of tightly packed and uniaxially compressed elastic beads in the presence of one or two light-mass impurities. For chains composed of beads of the same type, the intrinsic nonlinearity, which is caused by the Hertzian interaction of the beads, appears not to support localized, breathing modes. Consequently, the inclusion of light-mass impurities is crucial for their appearance. By analyzing the problem's linear limit, we identify the system's eigenfrequencies and the linear defect modes. Using continuation techniques, we find the solutions that bifurcate from their linear counterparts and study their linear stability in detail. We observe that the nonlinearity leads to a frequency dependence in the amplitude of the oscillations, a static mutual displacement of the parts of the chain separated by a defect, and for chains with two defects that are not in contact, it induces symmetry-breaking bifurcations.
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Affiliation(s)
- G Theocharis
- Department of Mathematics and Statistics, University of Massachusetts, Amherst, Massachusetts 01003-4515, USA
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75
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Abstract
Abstract
Experimental measurements, using an impulse response technique, are reported on a one-dimensional acoustic band gap system composed of a waveguide with a series of regularly spaced resonant structures. The amplitude data of the experimental results demonstrate the frequency and extent of the forbidden transmission bands and the phase information is analysed to determine the acoustic dispersion — the band structure — in the one-dimensional array. The results exhibit generally good agreement with previous theoretical analysis both in terms of the location of the forbidden transmission frequencies and in the form of the band structure. This simple system is a good candidate for the exploration of a number of postulated acoustic band gap effects.
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76
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Abstract
Abstract
Tunneling and dispersion of ultrasonic pulses is investigated in 3D phononic crystals consisting of 0.8 mm-diameter tungsten carbide beads that are close packed in a fcc crystal array embedded in either water or epoxy. Pulsed ultrasonic techniques allow us to measure the phase velocity and group velocity, i.e. the dynamics of wave propagation, as well as the transmission coefficient. Our experimental data are well interpreted using multiple scattering theory (MST). In the tungsten carbide/water crystals, dispersion phenomena were studied at frequencies in and around the gap in the ΓL direction. A strong suppression of the group velocity, and large variations of the group velocity dispersion (GVD) were found at frequencies around the band edges. By contrast, fast group velocities and nearly constant GVD with values around zero were observed at gap frequencies, indicating that tunneling in phononic crystals is essentially dispersionless. In the tungsten carbide/epoxy crystals a wide gap (to our knowledge, largest measured 3D band gap) was measured covering a frequency range from 1.2 MHz to 4.3 MHz along the ΓL crystal direction. The agreement between the theory and experiments gives strong evidence of the existence of a large complete gap (1.5 MHz to 3.9 MHz), which is theoretically predicted from the band structure calculations.
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77
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Wang X, Chen Z. Beam control and multi-color routing with spatial photonic defect modes. OPTICS EXPRESS 2009; 17:16927-16932. [PMID: 19770910 DOI: 10.1364/oe.17.016927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We demonstrate tunable re-directing, blocking, and splitting of a light beam along defect channels based on spatial bandgap guidance in two-dimensional photonic lattices. We show the possibility for linear control of beam propagation and multicolor routing with specially designed junctions and surface structures embedded in otherwise uniform square lattices.
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Affiliation(s)
- Xiaosheng Wang
- Department of Physics and Astronomy, San Francisco State University, San Francisco, California 94132, USA
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78
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Imura Y, Nakazawa H, Matsushita E, Morita C, Kondo T, Kawai T. Characterization of colloidal crystal film of polystyrene particles at the air-suspension interface. J Colloid Interface Sci 2009; 336:607-11. [DOI: 10.1016/j.jcis.2009.04.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2009] [Revised: 04/06/2009] [Accepted: 04/07/2009] [Indexed: 10/20/2022]
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79
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Hwang H, Park YH, Park JK. Optoelectrofluidic control of colloidal assembly in an optically induced electric field. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:6010-4. [PMID: 19466768 DOI: 10.1021/la9005604] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
This letter reports a method for controlling the organization of colloidal particles using optoelectrofluidic mechanisms. This optoelectrofluidic colloidal assembly (OCA) can be an efficient and simple way of preparing 2D colloidal crystals. Here, we present the first investigation of 2D colloidal assembly due to the electrohydrodynamic flows in an optoelectrofluidic device. The normalized distance among the assembled particles and the assembly rate according to the applied ac signal were analyzed. This OCA allows the control of both the colloidal crystal pattern over a large area and the distance between the assembled particles by adjusting the projected light pattern and the applied ac signal.
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Affiliation(s)
- Hyundoo Hwang
- Department of Bio and Brain Engineering, College of Life Science and Bioengineering, KAIST, 335 Gwahangno, Yuseong-gu, Daejeon 305-701, Republic of Korea
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80
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Chen B, Tang T, Chen H. Study on a compact flexible photonic crystal waveguide and its bends. OPTICS EXPRESS 2009; 17:5033-5038. [PMID: 19333264 DOI: 10.1364/oe.17.005033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The dispersion and transmission characteristics of transverse electric modes of a flexible photonic crystal waveguide are investigated by numerical simulation. Calculated results indicate that for arbitrary-angle bends of this waveguide with very small curved radii no more than two wavelengths, a very high transmission (>98.5%) is observed for a broad enough bandwidth. Owing to its unique advantage of compactness and flexibility, this waveguide is expected to be applied to highly dense photonic integrated circuits after further research.
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Affiliation(s)
- Bing Chen
- Key Laboratory of Physical Electronics and Devices of the Ministry of Education, Xi'an Jiaotong University, Xi'an, People's Republic of China
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81
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Fan WQ, Feng J, Song SY, Lei YQ, Xing Y, Deng RP, Dang S, Zhang HJ. Erbium-Complex-Doped Near-Infrared Luminescent and Magnetic Macroporous Materials. Eur J Inorg Chem 2008. [DOI: 10.1002/ejic.200800480] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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82
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Ristenpart WD, Jiang P, Slowik MA, Punckt C, Saville DA, Aksay IA. Electrohydrodynamic flow and colloidal patterning near inhomogeneities on electrodes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:12172-12180. [PMID: 18828610 DOI: 10.1021/la801419k] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Current density inhomogeneities on electrodes (of physical, chemical, or optical origin) induce long-range electrohydrodynamic fluid motion directed toward the regions of higher current density. Here, we analyze the flow and its implications for the orderly arrangement of colloidal particles as effected by this flow on patterned electrodes. A scaling analysis indicates that the flow velocity is proportional to the product of the applied voltage and the difference in current density between adjacent regions on the electrode. Exact analytical solutions for the streamlines are derived for the case of a spatially periodic perturbation in current density along the electrode. Particularly simple asymptotic expressions are obtained in the limits of thin double layers and either large or small perturbation wavelengths. Calculations of the streamlines are in good agreement with particle velocimetry experiments near a mechanically generated inhomogeneity (a "scratch") that generates a current density larger than that of the unmodified electrode. We demonstrate that proper placement of scratches on an electrode yields desired patterns of colloidal particles.
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Affiliation(s)
- W D Ristenpart
- Department of Chemical Engineering, Princeton University, Princeton, NJ 08544, USA
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83
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Tikhonov A, Coalson RD, Asher SA. Light diffraction from colloidal crystals with low dielectric constant modulation: Simulations using single-scattering theory. PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS 2008; 77:235404. [PMID: 20657709 PMCID: PMC2908428 DOI: 10.1103/physrevb.77.235404] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We theoretically characterized the diffraction properties of both closed-packed and non-closed-packed crystalline colloidal array (CCA) photonic crystals. A general theory based on single-scattering kinematic approach was developed and used to calculate the diffraction efficiency of CCA of different sphere diameters at different incident light angles. Our theory explicitly relates the scattering properties of individual spheres (calculated by using Mie theory) comprising a CCA to the CCA diffraction efficiency. For a CCA with a lattice constant of 380 nm, we calculated the relative diffraction intensities of the fcc (111), (200), and (220) planes and determined which sphere diameter gives rise to the most efficiently diffracting CCA for each set of crystal planes. The effective penetration depth of the light was calculated for several crystal planes of several CCAs of different sphere diameters at different angles of incidence. The typical penetration depth for a CCA comprised of polystyrene spheres was calculated to be in the range of 10-40 CCA layers. A one-dimensional (1D) model of diffraction from the stack of (111) fcc crystal layers was developed and used to assess the role of multiple scattering and to test our single-scattering approach. The role of disorder was studied by using this 1D scattering model. Our methodology will be useful for the optimization of photonic crystal coating materials.
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Affiliation(s)
- Alexander Tikhonov
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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84
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Wang J, Liang J, Wu H, Yuan W, Wen Y, Song Y, Jiang L. A facile method of shielding from UV damage by polymer photonic crystals. POLYM INT 2008. [DOI: 10.1002/pi.2376] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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85
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Palmero F, Carretero-González R, Cuevas J, Kevrekidis PG, Królikowski W. Solitons in one-dimensional nonlinear Schrödinger lattices with a local inhomogeneity. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2008; 77:036614. [PMID: 18517550 DOI: 10.1103/physreve.77.036614] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2007] [Indexed: 05/26/2023]
Abstract
In this paper we analyze the existence, stability, dynamical formation, and mobility properties of localized solutions in a one-dimensional system described by the discrete nonlinear Schrödinger equation with a linear point defect. We consider both attractive and repulsive defects in a focusing lattice. Among our main findings are (a) the destabilization of the on-site mode centered at the defect in the repulsive case, (b) the disappearance of localized modes in the vicinity of the defect due to saddle-node bifurcations for sufficiently strong defects of either type, (c) the decrease of the amplitude formation threshold for attractive and its increase for repulsive defects, and (d) the detailed elucidation as a function of initial speed and defect strength of the different regimes (trapping, trapping and reflection, pure reflection, and pure transmission) of interaction of a moving localized mode with the defect.
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Affiliation(s)
- F Palmero
- Nonlinear Dynamical Systems Group, Computational Science Research Center and Department of Mathematics and Statistics, San Diego State University, San Diego, CA 92182-7720, USA.
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86
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Zhang Y, Li B. Ultracompact waveguide bends with simple topology in two-dimensional photonic crystal slabs for optical communication wavelengths. OPTICS LETTERS 2007; 32:787-9. [PMID: 17339937 DOI: 10.1364/ol.32.000787] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Ultracompact waveguide bends with simple topology in two-dimensional photonic crystal slabs are proposed by using an annular air groove at the bend corner to improve transmissions of the bends. Analysis indicates that the guided light wave experiences a very slight difference of propagation properties between straight waveguides and bends (with 60 degrees and 120 degrees bending angles). Transmissions of more than 90% can be achieved in the 60 degrees and 120 degrees bends for light waves at 1.55 microm with bandwidths of 101 and 74 nm, respectively.
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Affiliation(s)
- Yao Zhang
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou, China
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87
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Ye Z, Han P, Zhao C, Quan Y, Lu X, Wu L. Self-assembling of submicrometer three-dimensional photonic crystals in concave microzones etched on silicon substrates. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2007; 24:231-5. [PMID: 17164865 DOI: 10.1364/josaa.24.000231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
By vertical sedimentation and oblique titration, silica microspheres were grown in different shapes of concave microzones that were etched on a (100) p-silicon substrate. Through scanning electron microscope observation and optical reflective spectra measurement, sedimentation of microspheres in those microzones was compared. An index was introduced to judge the efficiency of sedimentation. The comparison demonstrates that regular hexagons and triangles facilitate the growth of photonic crystals the most.
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Affiliation(s)
- Zhicheng Ye
- Institute of Semiconductors, The Chinese Academy of Sciences, Bejing, China.
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88
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Zhang YQ, Wang JX, Ji ZY, Hu WP, Jiang L, Song YL, Zhu DB. Solid-state fluorescence enhancement of organic dyes by photonic crystals. ACTA ACUST UNITED AC 2007. [DOI: 10.1039/b612905f] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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89
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Tian K, Barbastathis G, Hong J. Localized propagation modes guided by shear discontinuities in photonic crystals. OPTICS EXPRESS 2006; 14:10887-10897. [PMID: 19529501 DOI: 10.1364/oe.14.010887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We propose and analyze shear discontinuities as a new type of defect in photonic crystals. This defect can support guided modes with minimum group velocity dispersion (GVD) and maximum bandwidth, provided that the shear shift equals half the lattice constant. A mode gap emerges when the shear shift is different than half the lattice constant. The shear shift can be used to tune the bandwidth, group velocity, and group velocity dispersion (GVD) of the guided mode. The necessary condition for the existence of guided modes along the shear plane is discussed.
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90
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Sukhanova A, Baranov AV, Klinov D, Oleinikov V, Berwick K, Cohen JHM, Pluot M, Nabiev I. Self-assembly of charged microclusters of CdSe/ZnS core/shell nanodots and nanorods into hierarchically ordered colloidal arrays. NANOTECHNOLOGY 2006; 17:4223-4228. [PMID: 21727563 DOI: 10.1088/0957-4484/17/16/037] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
A thermodynamically driven self-organization of microclusters of semiconductor nanocrystals with a narrow size distribution into periodic two-dimensional (2D) arrays is an attractive low-cost technique for the fabrication of 2D photonic crystals. We have found that CdSe/ZnS core/shell quantum dots or quantum rods, transferred in aqueous phase after capping with the bifunctional surface-active agent DL-cysteine, form on a poly-L-lysine coated surface homogeneously sized micro-particles, droplet-like spheroid clusters and hexagon-like colloidal crystals self-organized into millimetre-sized 2D hexagonal assemblies. The presence of an organic molecular layer around the micro-particles prevents immediate contact between them, forming an interstitial space which may be varied in thickness by changing the origin of the molecular layer capping nanocrystals. Due to the high refractive index of CdSe and the low refractive index of the interstitial spaces, these structures are expected to have deep gaps in their photonic band, forming hierarchically ordered 2D arrays of potentially photonic materials.
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Affiliation(s)
- Alyona Sukhanova
- EA no 3798 'Détection et Approches Thérapeutiques Nanotechnologiques dans les Mécanismes Biologiques de Défense', Université de Reims Champagne-Ardenne, 51100 Reims, France
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91
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Lai ND, Lin JH, Liang WP, Hsu CC, Lin CH. Precisely introducing defects into periodic structures by using a double-step laser scanning technique. APPLIED OPTICS 2006; 45:5777-82. [PMID: 16855679 DOI: 10.1364/ao.45.005777] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
We demonstrate a promising method to precisely introduce desired defects into large-area periodic structures by using a double-step laser scanning technique. A multiexposure two-beam interference technique is first used to create 2D periodic structures. A low power femtosecond laser combined with a high numerical aperture objective lens is then used to map the periodic structures to determine the positions and orientations of air holes or material cylinders without intermediate development. Based on the mapping results, the desired defects are written precisely into these structures by increasing the power of the femtosecond laser to induce a multiphoton polymerization effect. The experimental results show that defects are patterned with accurate positions and orientations. This proposed technique should be useful for fabrication of photonic crystals with well-defined defects.
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Affiliation(s)
- Ngoc Diep Lai
- National Chung Cheng University, Ming Hsiung, Chia Yi 621, Taiwan
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92
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Massé P, Reculusa S, Ravaine S. Elaboration of photonic crystal heterostructures by the Langmuir–Blodgett method. Colloids Surf A Physicochem Eng Asp 2006. [DOI: 10.1016/j.colsurfa.2005.12.035] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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93
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Lu Z, Shi S, Murakowski JA, Schneider GJ, Schuetz CA, Prather DW. Experimental demonstration of self-collimation inside a three-dimensional photonic crystal. PHYSICAL REVIEW LETTERS 2006; 96:173902. [PMID: 16712297 DOI: 10.1103/physrevlett.96.173902] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2005] [Indexed: 05/09/2023]
Abstract
We present our experimental demonstration of self-collimation inside a three-dimensional (3D) simple cubic photonic crystal at microwave frequencies. The photonic crystal was designed with unique dispersion property and fabricated by a high precision computer-controlled machine. The self-collimation modes were excited by a grounded waveguide feeding and detected by a scanning monopole. Self-collimation of electromagnetic waves in the 3D photonic crystal was demonstrated by measuring the 3D field distribution, which was shown as a narrow collimated beam inside the 3D photonic crystal but a diverged beam in the absence of the photonic crystal.
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Affiliation(s)
- Zhaolin Lu
- Department of Electrical and Computer Engineering, University of Delaware, Newark, 19716, USA
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94
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Kyu T, Meng S, Duran H, Nanjundiah K, Yandek GR. Holographic polymer-dispersed liquid crystals and polymeric photonic crystals formed by holographic photolithography. Macromol Res 2006. [DOI: 10.1007/bf03218503] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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95
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Liu Y, Liu S, Zhang X. Fabrication of three-dimensional photonic crystals with two-beam holographic lithography. APPLIED OPTICS 2006; 45:480-3. [PMID: 16463731 DOI: 10.1364/ao.45.000480] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
A holographic technique used to fabricate three-dimensional photonic crystals with a two-beam interference method is presented. In the optical setup of fabrication one beam is incident on the recording plate in the direction of the plate normal and the other beam with an angle to the normal. Three exposures were taken. Between each exposure, the recording plate was rotated 120 degrees on axis until three exposures were completed. Good three-dimensional lattice structures have been obtained. Theoretical analysis, computer simulations, and experimental results are presented.
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Affiliation(s)
- Ying Liu
- Department of Physics, Xiamen University, China.
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96
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Li M, Li ZY, Ho KM, Cao JR, Miyawaki M. High-efficiency calculations for three-dimensional photonic crystal cavities. OPTICS LETTERS 2006; 31:262-4. [PMID: 16441050 DOI: 10.1364/ol.31.000262] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
A numerical method was developed by combining a plane-wave-based transfer matrix method and a robust rational function interpolation algorithm. The optical properties of three-dimensional photonic crystal cavities were extracted in a short computation time with high numerical accuracy.
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Affiliation(s)
- Ming Li
- Department of Physics and Astronomy, Iowa State University, Ames 50011, USA
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97
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Gierszal KP, Yoon SB, Yu JS, Jaroniec M. Adsorption and structural properties of mesoporous carbons obtained from mesophase pitch and phenol-formaldehyde carbon precursors using porous templates prepared from colloidal silica. ACTA ACUST UNITED AC 2006. [DOI: 10.1039/b603724k] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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98
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Lee TW, Gray S. Subwavelength light bending by metal slit structures. OPTICS EXPRESS 2005; 13:9652-9. [PMID: 19503170 DOI: 10.1364/opex.13.009652] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
We discuss how light can be efficiently bent by nanoscale-width slit waveguides in metals. The discussion is based on accurate numerical solutions of Maxwell's equations. Our results, using a realistic model for silver at optical wavelengths, show that good right-angle bending transmission can be achieved for wavelengths lambda> 600 nm. An approximate stop-band at lower wavelengths also occurs, which can be partly understood in terms of a dispersion curve analysis. The bending efficiency is shown to correlate with a focusing effect at the inner bend corner. Finally, we show that good bending transmission can even arise out of U-turn structures.
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99
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Dionigi C, Calestani G, Ferraroni T, Ruani G, Liotta LF, Migliori A, Nozar P, Palles D. Template evaporation method for controlling anatase nanocrystal size in ordered macroporous TiO2. J Colloid Interface Sci 2005; 290:201-7. [PMID: 15935368 DOI: 10.1016/j.jcis.2005.04.033] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2004] [Revised: 04/07/2005] [Accepted: 04/11/2005] [Indexed: 11/19/2022]
Abstract
The importance of pure-phase titanium oxide materials as catalysts, sensors, and photonic band-gap materials has been growing steadily. Recently, more attention has been focused on nanostructured titanium oxide showing controlled and periodic porosity on a nanometric scale. The nanocrystal size control of porous nanostructured titanium oxide in an anatase form is a crucial step for the organic template method. Simple template removal by evaporation in an inert atmosphere is reported in this article and compared with the calcination technique usually reported in the literature. The proposed method allows the formation of a double-porous (macro and meso) anatase phase. We demonstrate that it highly preserves the macropore order into a titanium oxide material and induces narrowly dispersed mesopores by controlling the nano-crystal size that is kept around 6 nm. For the proposed method, polystyrene beads are particularly suitable as templates, being evaporated in the temperature range of anatase existence. The final high surface area makes the materials appealing for applications as photocatalysts or sensors.
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Affiliation(s)
- Chiara Dionigi
- Istituto per lo Studio dei Materiali Nanostrutturati-Sezione di Bologna, Consiglio Nazionale delle Ricerche, via P. Gobetti, 101, I-40129 Bologna, Italy.
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100
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Meng S, Kyu T, Natarajan LV, Tondiglia VP, Sutherland RL, Bunning TJ. Holographic Photopolymerization-Induced Phase Separation in Reference to the Phase Diagram of a Mixture of Photocurable Monomer and Nematic Liquid Crystal. Macromolecules 2005. [DOI: 10.1021/ma0480906] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Scott Meng
- Department of Polymer Engineering, University of Akron, Akron, Ohio 44325; Science Applications International Corporation, Dayton, Ohio 45431; and Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Ohio 45433
| | - Thein Kyu
- Department of Polymer Engineering, University of Akron, Akron, Ohio 44325; Science Applications International Corporation, Dayton, Ohio 45431; and Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Ohio 45433
| | - Lalgudi V. Natarajan
- Department of Polymer Engineering, University of Akron, Akron, Ohio 44325; Science Applications International Corporation, Dayton, Ohio 45431; and Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Ohio 45433
| | - Vincent P. Tondiglia
- Department of Polymer Engineering, University of Akron, Akron, Ohio 44325; Science Applications International Corporation, Dayton, Ohio 45431; and Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Ohio 45433
| | - Richard L. Sutherland
- Department of Polymer Engineering, University of Akron, Akron, Ohio 44325; Science Applications International Corporation, Dayton, Ohio 45431; and Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Ohio 45433
| | - Timothy J. Bunning
- Department of Polymer Engineering, University of Akron, Akron, Ohio 44325; Science Applications International Corporation, Dayton, Ohio 45431; and Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Ohio 45433
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