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Photonic Structures (photonic + structure)
Selected AbstractsMagnetically Tunable Colloidal Photonic Structures in Alkanol Solutions,ADVANCED MATERIALS, Issue 18 2008Jianping Ge Magnetically tunable photonic structures are prepared in alkanol solutions by using silica-modified superparamagnetic Fe3O4 colloids as building blocks. Repulsive electrostatic and solvation forces and magnetically induced attractive forces contribute to the ordering of the Fe3O4@SiO2 colloids. The ability to form tunable photonic structures in nonaqueous solutions allows the fabrication of field-responsive polymer composite films for potential applications as displays and sensors. [source] Modifying the Output Characteristics of an Organic Light-Emitting Device by Refractive-Index Modulation,ADVANCED FUNCTIONAL MATERIALS, Issue 18 2006T. Höfler Abstract In order to modify the output characteristics of organic light-emitting devices (OLEDs), the optical properties of an active layer within the device are patterned without introducing any thickness modulation. For this purpose a new conjugated copolymer, which serves as a hole-transporting material and at the same time can be index patterned using UV techniques, is synthesized. Poly(VC- co -VBT) (VC: N -vinylcarbazole; VBT: 4-vinylbenzyl thiocyanate) is prepared by free-radical copolymerization of VC and VBT. The material contains photoreactive thiocyanate groups that enable altering of the material's refractive index under UV illumination. This copolymer is employed as a patternable hole-transporting layer in multilayer OLEDs. Refractive-index gratings in poly(VC- co -VBT) are inscribed using a holographic setup based upon a Lloyd mirror configuration. The fourth harmonic of a Nd:YAG (YAG: yttrium aluminum garnet) laser (266,nm) serves as the UV source. In this way 1D photonic structures are integrated in an OLED containing AlQ3 (tris(8-hydroxyquinoline) aluminum) as the emitting species. It is assured that only a periodical change of the refractive index (,n,=,0.006 at ,,=,540,nm) is generated in the active material but no surface-relief gratings are generated. The patterned devices show more forward-directed out-coupling behavior than unstructured devices (increase in luminosity by a factor of five for a perpendicular viewing direction). This effect is most likely due to Bragg scattering. For these multilayer structures, optimum outcoupling was observed for grating periods ,,,,390,nm. [source] Rewritable Photonic Paper with Hygroscopic Salt Solution as InkADVANCED MATERIALS, Issue 42 2009Jianping Ge Flexible photonic paper is fabricated through the instant magnetic assembly of Fe3O4@SiO2 colloids, followed by a rapid photopolymerization to fix the photonic structures inside the PEGDA matrix. Solutions of LiCl, MgCl2, or CaCl2 are used as inks to print durable letters and patterns with color contrast based on the local swelling of the polymer matrix. The photonic paper is rewritable and benign to the environment as the ink marks can simply be removed by washing with water. [source] Rare-Earth Spontaneous Emission Control in Three-Dimensional Lithium Niobate Photonic CrystalsADVANCED MATERIALS, Issue 34 2009Airán Ródenas Spontaneous emission inhibition of erbium ions at 1.5,µm wavelength is obtained by tailoring direct femtosecond-laser-written 3D photonic structures inside lithium niobate laser crystals. This technique allows for engineering of the structure symmetry and filling fraction by spatially inscribing laser-induced amorphous voxels inside the crystalline sample. [source] Stacking the Nanochemistry Deck: Structural and Compositional Diversity in One-Dimensional Photonic CrystalsADVANCED MATERIALS, Issue 16 2009Leonardo D. Bonifacio Abstract One-dimensional photonic structures, known as Bragg stacks or Bragg reflectors or Bragg mirrors, represent a well-developed subject in the field of optical science. However, because of a lack of dynamic tunability and their dependence on complex top-down techniques for their fabrication, they have received little attention from the materials science community. Herein, we present recent and ongoing developments on the way to functional one-dimensional photonic structures obtained from simple bottom-up techniques. We focus on the versatility of this new approach, which allows the incorporation of a wide range of materials into photonic structures. [source] Magnetically Tunable Colloidal Photonic Structures in Alkanol Solutions,ADVANCED MATERIALS, Issue 18 2008Jianping Ge Magnetically tunable photonic structures are prepared in alkanol solutions by using silica-modified superparamagnetic Fe3O4 colloids as building blocks. Repulsive electrostatic and solvation forces and magnetically induced attractive forces contribute to the ordering of the Fe3O4@SiO2 colloids. The ability to form tunable photonic structures in nonaqueous solutions allows the fabrication of field-responsive polymer composite films for potential applications as displays and sensors. [source] Nonlinear Tamm states and surface effects in periodic photonic structuresLASER PHYSICS LETTERS, Issue 10 2008Yu. S. KivsharArticle first published online: 10 JUL 200 Abstract We present a brief overview of the basic concepts and important experimental observations of the effect of light localization near the surfaces of truncated periodic photonic structures. In particular, we discuss the formation of nonlinear localized modes and discrete surface solitons near the edges of nonlinear optical waveguide arrays and two-dimensional photonic lattices. We draw an analogy between the nonlinear surface optical modes and the surface Tamm states known in the electronic theory. We discuss the crossover between discrete solitons in the array and surface solitons at the edge of the array by analyzing the families of even and odd nonlinear localized modes located at finite distances from the edge of a waveguide array. We discuss various generalization of this concept including surface solitons in chirped lattices, multi-gap vector surface solitons, polychromatic surface states generated by a supercontinuum source, surface modes in two-dimensional photonic lattices, and spatiotemporal surface solitons. Finally, we discuss briefly several other related concepts including the enhanced beaming of light from subwavelength waveguides in photonic crystals. (© 2008 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Lateral structuring of porous silicon: application to waveguidesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2003A. M. Rossi Abstract The problem of lateral definition of waveguides and photonic structures has been tackled by means of direct laser scribing on porous silicon (PS). The low thermal conductivity of PS allows for local oxidation and even the complete ablation of the material with laser power of a few mW. The buried Laser Local Oxidized (LaLOx) method exhibits great versatility and efficiency in achieving lateral light confinement in waveguides. [source] Fabricating three-dimensional polymeric photonic structures by multi-beam interference lithography,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 2 2006Jun Hyuk Moon Abstract The fabrication of true three-dimensional (3D) microstructures both rapidly and economically over a large area with negligible defects is attractive for a wide range of applications. In particular, multi-beam interference lithography is one of the promising techniques that can mass-produce polymeric 3D photonic crystals defect-free over a large area. This review discusses the relationship between beam geometry and the symmetry of the interference patterns, the lithographic process, and various types of photoresist systems, including thick films of negative-tone and positive-tone photoresists, organic-inorganic hybrids, hydrogels, and holographic polymer-dispersed liquid crystals. Copyright © 2006 John Wiley & Sons, Ltd. [source] Fine structural dependence of ultraviolet reflections in the King Penguin beak hornTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 3 2006Birgitta Dresp Abstract The visual perception of many birds extends into the near-ultraviolet (UV) spectrum and ultraviolet is used by some to communicate. The beak horn of the King Penguin (Aptenodytes patagonicus) intensely reflects in the ultraviolet and this appears to be implicated in partner choice. In a preliminary study, we recently demonstrated that this ultraviolet reflectance has a structural basis, resulting from crystal-like photonic structures, capable of reflecting in the near-UV. The present study attempted to define the origin of the photonic elements that produce the UV reflectance and to better understand how the UV signal is optimized by their fine structure. Using light and electron microscopic analysis combined with new spectrophotometric data, we describe here in detail the fine structure of the entire King Penguin beak horn in addition to that of its photonic crystals. The data obtained reveal a one-dimensional structural periodicity within this tissue and demonstrate a direct relationship between its fine structure and its function. In addition, they suggest how the photonic structures are produced and how they are stabilized. The measured lattice dimensions of the photonic crystals, together with morphological data on its composition, permit predictions of the wavelength of reflected light. These correlate well with experimentally observed values. The way the UV signal is optimized by the fine structure of the beak tissue is discussed with regard to its putative biological role. © 2006 Wiley-Liss, Inc. [source] | |||||||||||||