Proceedings Volume 4806

Complex Mediums III: Beyond Linear Isotropic Dielectrics

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Proceedings Volume 4806

Complex Mediums III: Beyond Linear Isotropic Dielectrics

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Volume Details

Date Published: 24 June 2002
Contents: 11 Sessions, 36 Papers, 0 Presentations
Conference: International Symposium on Optical Science and Technology 2002
Volume Number: 4806

Table of Contents

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Table of Contents

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  • Inaugural Session
  • Sonoluminescence and Plasmons
  • Patterns and Statistics
  • Constituitive Relations
  • Chiral Electromagnetics I
  • Microwaves and Left-handed Materials
  • Energy Harvesting and Nanostructures I
  • Nanostructures II
  • Chiral Electromagnetics II
  • Optical Constants
  • Posters
  • Microwaves and Left-handed Materials
Inaugural Session
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Randomness in complex media
H. John Caulfield, Don Otto Henderson, Mikhail A. Noginov
Randomness is not always the enemy. It can serve many purposes where materials sciences and optical sciences meet. Among those purposes are these. It can provide the raw material for self-organization. It can 'uniformize' optical properties. It can make manufacturing easier. It can assure a great deal of noise immunity. Although most cases exhibit all of those features, we can illustrate them with examples in which one tends to dominate the other.
Sonoluminescence and Plasmons
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Giant magneto-impedance in structured materials
Larissa V. Panina, D. P. Makhnovskiy
Recent discovery of giant magneto-impedance (GMI) has opened new horizons in the development of micro magnetic sensor technology. GMI involves a very large and sensitive change in complex impedance of certain soft magnetic materials. However, with decreasing the sensor element Size, the maintenance of such high sensitivity becomes a major concern. Special thin-film structures are employed to improve GMI performance in miniature elements. The present paper concerns the principal advantages of GMI in magnetic/metallic multilayered materials. The physical concepts, theoretical analysis based on field-dependent surface impedance matrix and experimental results are discussed. This includes multi-fold enhancement of the GMI ratio and a considerable extension of the operational frequency range. Along with this, special types of magnetic anisotropy can be induced in layered systems to realize asymmetrical GMI. This property is of particular interest for magnetic sensor applications.
Plasmonic nanophotonics: manipulating light and sensing molecules
Vladimir M. Shalaev, Viktor A. Podolskiy, Andrey K. Sarychev
We show that plamonic nanomaterials allow the localization and guiding light, with high efficiency, and molecule sensing, with unsurpassed sensitivity. Two types of palsmonic naomaterials are considered: metal nanowires and fractal colloid aggregates. The electromagnetic field distribution for thin metal nanowires is found, by using the discrete dipole approximation. The plasmon polariton modes in wires are numerically simulated. These modes are found to be dependent on the incident light wavelength and direction of propagation. The existence of localized plasmon modes and strong local field enhancement in percolation nanowire composites is demonstrated. Novel left-handed materials in the near-infrared and visible are proposed based on nanowire composites. Dramatic enhancement in fractal colloid aggregates and, especially, in fractal-microcavity composites are discussed along with new potential applications of these plasmonic materials.
Light management at nanoscale
Andrey K. Sarychev, Viktor A. Podolskiy, A. M. Dykhne, et al.
An analytical theory for extraordinary light transmittance through an optically thick metal film with sub-wavelength holes is developed. It is shown that the film transmittance has sharp peaks that are due to the Maxwell-Garnet resonances in the holes. At resonances electric and magnetic fields are dramatically enhanced in the holes. These resonances are proposed to guide light over a metal film at a nanoscale.
Patterns and Statistics
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Optical patterns and nonlinear spatial structures
Spontaneous spatial patterns occur in nonlinear systems with spatial coupling, e.g. through diffraction or diffusion. Strong enough nonlinearity can induce spatial symmetry breaking, such that a pattern becomes more stable than the unpatterned state. Instances discussed are in nonlinear optics, but the phenomena have a universal character, and are the basis of spatial differentiation in nature, from crystals to clouds, from giraffe-coats to galaxies. The basic theory and phenomena of pattern formation are reviewed, with examples from experiments and simulations (mainly from optics). Patterns usually consist of repeated units, and such units may exist in isolation as a localized structure. Such structures are akin to spatial solitons, and are potentially useful in image and/or information processing. The nature and properties of such structures are discussed and illustrated.
Constituitive Relations
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Constitutive relations
Werner S. Weiglhofer
To provide a complete and self--consistent description of an electromagnetic process in any type of material, the macroscopic Maxwell equations must be supplemented by constitutive relations. This paper reviews some of the fundamental aspects related to the characterization of different types of materials in terms of constitutive relations. In particular, the dual viewpoints of time--domain and frequency--domain formulations are explored, and certain issues concerning classifications of materials depending on their electromagnetic response are addressed.
Volterra differential constitutive operators and locality considerations in electromagnetic theory
Dan Censor, Timor Melamed
Macroscopic Maxwell's theory for electrodynamics is an indeterminate set of coupled, vector, partial differential equations. This infrastructure requires the supplement of constitutive equations. Recently, a general framework has been suggested, taking into account dispersion, inhomogeneity and nonlinearity, in which the constitutive equations are posited as differential equations involving the differential operators based on the Volterra functional series. The validity of such representations needs to be examined. Here it is shown that for such representations to be effective, the spatiotemporal functions associated with the Volterra differential operators must be highly localized, or equivalently, widely extended in the transform space. This is achieved by exploiting Delta-function expansions, leading in a natural way to polynomial differential operators. The Four-vectors Minkowski space is used throughout, facilitating general results and compact notation.
Combined numerical and analytic approach for generalized models of complex bi-anisotropic materials
Seung-Woo Lee, Akira Ishimaru, Yasuo Kuga, et al.
A combined numerical and analytic approach is presented to obtain a general matrix form of constitutive relations for a bi-anisotropic material which consists of arbitrary inclusions in a host medium. This approach is based on the quasi-static Lorentz-Lorenz theory which relates the constitutive parameters of the material with the electric and magnetic dipole moments of the inclusions which can be calculated in a numerical or analytic way. Analysis of 'meta-materials' is conducted to validate the proposed method.
Trilocally approximated strong-permittivity-fluctuation theory for nonlinear composite mediums
Tom G. MacKay, Akhlesh Lakhtakia, Werner S. Weiglhofer
The strong-permittivity-fluctuation theory (SPFT) is well-established in the context of the homogenisation of linear composite materials. Unlike conventional homogenisation formalisms, the SPFT takes account of coherent interactions between scattering centres at sub-wavelength length scales. A weakly nonlinear second-order SPFT, applicable to electrostrictive composite materials, has recently been developed. We present here the corresponding third-order theory, namely the trilocally approximated SPFT. The issues of nonlinear SPFT convergence and the manifestation of nonlinearity enhancement are explored by means of a numerical example. The sensitivity of the nonlinear SPFT to the choice of covariance function is discussed.
Chiral Electromagnetics I
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Layered chiral metallic meta-materials
Nikolay I. Zheludev, Aris Papakostas, Adrian W. Potts, et al.
Using electron beam lithographic techniques we have manufactured left and right-handed forms of an artificial medium consisting of high densities of microscopic planar chiral metallic objects distributed regularly in a plane. In this artificial medium we have for the first time observed optical manifestations of planar chirality in the form of handedness-sensitive rotation of the polarization state and elliptization of visible light diffracted from the structure. Applications of such media in functional materials are discussed.
Layered and continuous handed materials for chiral optics
Ian J. Hodgkinson, Qihong Wu, Lakshman de Silva
Thin film optical materials deposited with a helical nanostructure can be used to fabricate devices that respond differently to right-handed and left-handed circularly polarized light. Together these inorganic materials and devices promise the framework of chiral optics, in which the basic polarization states of propagating light are circular. In the presentation we show that one period of a continuous chiral material can be replaced with three or more sub- layers of oriented biaxial material, and compare the performance that is expected of elements and devices such mirrors, spacerless spectral-hole filters and circularly polarized lasers that use continuous and layered chiral materials respectively. The investigation shows that, for the same number of turns and local linear birefringence, the performance of the layered material is slightly poorer than that of the continuos material. However, in practice the small loss in performance of the layered chiral material may be offset by inherently larger local linear birefringence and improved structural fidelity due to superiority of optical monitoring over quartz-crystal monitoring.
Volume and suface gratings combined
We report on the propagation of plane electromagnetic waves through a complex dielectric medium consisting of two complementary grating structures: a sinusoidal interface between two isotropic dielectric mediums overlaying a structurally chiral anisotropic dielectric medium. Phenomenons characteristic of both types of structures - namely the Rayleigh-Wood anomalies and the circular Bragg phenomenon - are shown to co-exist, even at wavelengths where both occur together. Our results open the possibility of novel device geometries which exploit these effects.
Towards graded-index planar waveguides using 2D sculptured thin films
The waveguiding properties of sculptured nematic thin films (SNTFs) are investigated. A theoretical framework to determine the modal wavenumbers and modeshapes for guided wave propagation through these anisotropic microcolumnar mediums is presented. Numerical results are provided to illustrate the characteristics of guided wave propagation through C-SNTFs. The differences between guided wave propagation in such mediums and the corresponding isotropic thin films are highlighted.
Admittance determination for cylindrical soft and hard surface chirowaveguides for mode transformation
Umit Erturk, Savas Uckun
The generalized dyadic admittance resulting from the transverse fields in slightly chiral soft and hard surface waveguides is presented. The derived admittance is useful in describing the mode transforming effect of the waveguide. In the analysis of the admittance equations, it is observed that the length of the waveguide is of critical importance.
Microwaves and Left-handed Materials
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Applicability of ferrimagnetic hosts to nanostructured negative index of refraction (left-handed) materials
There has been considerable interest generated by the demonstration of (epsilon) < 0, (mu) < 0 composite materials. These negative index of refraction materials, a subset of the class of materials labeled 'left-handed', possess two different arrays of resonant structures which separately give rise to negative (epsilon) and (mu) over the appropriate microwave frequency interval. Any attempt to significantly increase the operating frequency will require shrinking the resonant elements to a nanostructure. Replacing the array of elements responsible for (mu) < 0 with a nonconducting ferrimagnet significantly reduces the complexity of the resulting nanostructured material. This presentation includes a brief overview of the behavior of negative index of refraction materials and an enumeration of the advantages and disadvantages of using a ferrimagnet to produce (mu) < 0. In addition, calculations of the transmission of electromagnetic waves through a ferrimagnet based negative index of refraction material are presented. In particular, the prospects for operating in the far IR and microwave regimes, pro9blems with the interaction between the (epsilon) < 0 structures and the ferrimagnet, and tunability with externally applied magnetic fields are discussed.
Transmission properties of material with relative permittivity and permeability close to -1
John Rhodes Thomas, Akira Ishimaru
J.B. Pendry has shown that a layer of material with relative permittivity and relative permeability both equal to -1 behaves as a perfect two-dimensional lens for an object closer than the thickness of the layer. We examine results for transmission through a material with relative constants close to -1. For a passive material, the imaginary parts of relative permittivity and permeability are negative (the engineer's convention). We treat the transmission of a delta-function line source through a layer. This source includes all spatial wave numbers. The longitudinal component kz of the propagation vector normal to the surface assumes values that are negative real and imaginary for the evanescent modes. Transmission in a medium that has both relative permittivity and permeability equal to -1 amplifies the imaginary kz terms and, thus, restores the evanescent waves and bypasses the usual diffraction limit of an ordinary lens. We show that small deviations from the perfect lens material cause a change from amplification to attenuation of these evanescent waves and thus limit the degree of improvement of an image.
Energy Harvesting and Nanostructures I
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Energy harvesting materials
It is shown how key features of natural photosynthesis can be emulated in novel materials based on photoactive multichromophore arrays and crystals. A major consideration in the design of such systems is the means of channeling electronic excitation from sites of light absorption to centers where it is stored or released. Storage is often achieved by driving charge separation or, for the longer term, a more complex chemical reaction whilst rapid release is commonly associated with frequency up-converted emission. In each case channeling to the conversion site generally entails a multi-step energy transfer mechanism whose efficiency is determined by the arrangement and electronic properties of the array chromophores or ions, guided in the more complex systems by a spectroscopic gradient that promotes overall directionality. The functional cascade molecules known as photoactive dendrimers are exemplars of this approach. The latest developments involve new mechanisms for concerted excitation transfer in multichromophore systems, leading towards the tailoring and exploitation of optical nonlinearities for high intensity energy pooling applications.
Nanostructured gain materials
John M. Arnold
Applications of semiconductor quantum wells and quantum dots to the amplification of optical fields are discussed. The principle types of nanostructured semiconductor optical gain medium, namely edge-emitting quantum wells, surface emitting quantum wells, quantum cascade and quantum dot media, are described.
Hydrogen storage in carbon nanostructures
Boris P. Tarasov, Yuriy M. Shul'ga, Oleksander O. Lobodyuk, et al.
Magnetization curves in the fields up to 10 koe measured for powders produced at the electric arc the sputtering of graphite-cobalt-nickel electrodes. It was ascertained that magnetic properties of powders essentially depend on the place of their deposition within a spray chamber. The deposition growing on the cathode is basically a diamagnetic material while the rest of the products after sputtering is ferromagnetic. Their ferromagnetism is conditioned by Co-Ni nanoparticles. Some of them are encapsulated into the carbon shell that preserves those particles from oxidation by air and dissolution in a hydrochloric acid.
Nanostructures II
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Nanostructured thin films: a critical review
Nanostructured thin films containing metal or conducting oxides underpin some existing technologies. Based on recent advances they will also enable many emerging opportunities. The optical properties from different nanostructures are linked to examples including, spectrally selective solar absorbers, solar control glazing, angular selective filters, optical bio-sensors, and decorative paints. This review will cover studies of various film and coating morphologies including cermets, and polymers containing metal or oxide conductor nanoparticles, oblique nano-metal columns in oxide, clusters and arrays of conducting nanoparticles, nanoholes in metal, granular metal networks and thin metal layers on nanostructures. Situations where quasi-static effective medium theories of optical response can be used and those where they are inadequate due to surface plasmon polariton effects will be compared. The latter includes very fine scale nano-features. Coupling between surface plasmons to form new modes is an important consideration. A brief look will also be given into an important new field - very thin metal films on nanoparticles which allow broad band tuning as thickness changes. The nanostructure within such films is quite influential.
Semiconductor nanowire array
A novel vapor-liquid-solid epitaxy (VLSE) process has been developed to synthesize high-density semiconductor nanowire arrays. The nanowires generally are single crystalline and have diameters of 10-200 nm and aspect ratios of 10-100. The areal density of the array can be readily approach 1010 cm-2. Results based on Si and ZnO nanowire systems are reported here.
Nanoscale surface texturing by impact of accelerated condensed-gas nanoparticles
Lisa P. Allen, David B. Fenner, C. Santeufemio, et al.
Commercial apparatus has recently become available to utilize a gas-cluster ion beam (GCIB) for smoothing microelectronic and photonic surfaces to sub-nanometer residual roughness. Smoothing occurs after a high fluence to the surface. However, at very low fluence, surface features are observed that are helpful in modeling the stochastic nature of the smoothing. These low fluence features have potential for nano-scale surface texturing that may result in unique electronic and optical properties. This paper addresses the impact of individual gas clusters to yield nano-scale craters in SiO2 and nano-scale hillocks on Si. The nature of these features results from parameters of cluster species, beam acceleration, target material and residual vacuum chamber gases, as well as chemical reactions. 20 kV argon clusters impacting a smooth SiO2 film results in pits approximately 4 nm deep, approximately 10 nm diameter with a small rim of ejecta. Higher energy 24 kV Ar gas clusters incident on silicon with approximately 20 SiO2 cause hillocks approximately 4 nm high (projecting above the native oxide) and a approximately 40 nm diameter. The hillocks formed from Ar-GCIB on Si are composed of SiOx and have been found to reflect the symmetry of the underlying (100) or (111) crystallographic Si orientations.
Effect of zeolite type upon properties of copper nanoparticles and the clusters produced within them
Vitalii P. Petranovskii, Valerij S. Gurin, Nina E. Bogdanchikova, et al.
Copper nanoparticles were produced within the protonated and alkaline forms of several zeolites by the hydrogen reduction of corresponding Cu-exchanged forms. Variation of zeolite structure, reduction temperature and acidity of zeolites were the main factors influencing metal reducibility and appearance of copper reduced forms. They were detected by means of optical absorption using diffuse reflectance spectroscopy technique. The effect of zeolite type upon the plasmon resonance band associated with the reduced copper clusters was investigated experimentally and discussed with eh Mie theory simulation results. The type of this spectral appearance is associated with size of copper nanoparticles formed as the result of reduction and secondary aggregation and dielectric properties of zeolite micro crystals being a matrix for the nanoparticle stabilization.
Chiral Electromagnetics II
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Circularly polarized luminescence from an organoterbium emitter embedded in a chiral polymer
Kristina Bjorknas, Peter Raynes, Sandra Gilmour, et al.
The periodic helical structure of an aligned cholesteric liquid crystal gives rise to circular Bragg reflection such that circularly polarised light of the same handedness as the helix is reflected while counter circularly polarised light is transmitted. The resulting circularly polarised 1D photonic band gap can be used to suppress or enhance circularly polarised photoluminescence from a fluorescent guest material embedded in a chiral host whose resonance region coincides with the emission of the fluorophor. The periodic structure of the host suppresses emission of one circular handedness of certain frequencies and enhances the suppressed emission at the edges of the reflection band. To avoid the effects of redistributing the photon density of states across the spontaneous emission spectrum and to observe inhibition of spontaneous emission of one handedness a very narrow fluorophor is needed. In this paper, an organoterbium complex is embedded in a cholesteric reactive mesogen (RM) host, which is subsequently polymerized by UV-exposure to generate a chiral polymer. The reflection band of the chiral host is tuned to completely overlap the different emission lines of the organolanthanide as well as to lie in between them. We investigate how the suppression of one emission channel causes a redistribution of probabilities for the remaining pathways resulting in a spectral and spatial redistribution of emission.
Supramolecular chiral films
Karl-Heinz Ernst, Roman Fasel, Y. Kuster
The self-assembly of racemic and enantiopure Heptahelicene, a helically shaped polyaromatic hydrocarbon (C30H18), on single-crystal surfaces was studied at temperatures between 150 K and 1000 K by means of surface sensitive methods like scanning tunneling microscopy (STM), temperature programmed desorption (TPD), low-energy electron diffraction (LEED), time-of-flight secondary mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy and diffraction (XPS, XPD), and Auger electron spectroscopy (AES). On Ni(111), Ni(100) and Cu(111), the molecule remains intact up to 450 K. Above that temperature it decomposes in several steps into carbon and hydrogen, the latter desorbing subsequently as H2. The adsorption of racemic Heptahelicene on Cu(111) leads to a two-dimensional enantiomeric separation into at least 20 nm wide homochiral domains. In the first monolayer, the adsorbate-substrate complex has a geometry in which the molecule is oriented with three terminal rings parallel to the surface. After adsorption of enantiopure Heptahelicene onto the stepped Cu(332) surface, an azimuthal alignment of the molecular spirals is observed, creating a single-phase orientational order. X-ray absorption studies (NEXAFS) using synchrotron radiation show for the molecule in the saturated monolayer on Ni(100) a tilted geometry.
Piezoelectric control of lasing in polymeric chiral-sculptured thin films
Fei Wang, Akhlesh Lakhtakia, Russell F. Messier
We propose a piezoelectric control mechanism to tune laser made of polymeric chiral sculptured thin films. The negative piezoelectric effect in a piezoelectric layer deposited on a polymeric chiral STF laser will shift the Bragg regime.
Optical Constants
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Generalized ellipsometry of complex mediums in layered systems
Mathias Schubert, Alexander Kasic, Tino Hofmann, et al.
A new global approach, called 'Generalized Ellipsometry', is now capable to characterize the optical and structural properties of general anisotropic layered systems, including absorption, and can be applied, in general, to determine the linear response tensor elements for wavelengths from the far IR to the deep UV. This technique enables new insights into physical phenomena of layered anisotropic mediums, and can provide precise structural and optical data of novel compound materials. Experimental results are presented for stibnite single crystals as example for an arbitrary biaxial absorbing material, a wurtzite GaN thin film with uniaxial anisotropy grown on sapphire, a spontaneously atomically ordered III-V semiconductor alloy thin film, and a sculptured titanium dioxide film with symmetrically dielectric tensor properties.
Posters
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Elastic strain at Ge particles-Si matrix interface: a raman spectroscopic study
Anushree Roy, Sangeeta Sahoo
Ge clusters show luminescence at room temperature. The clusters are grown on Si substrate at room temperature (Ge-RT) and also at liquid nitrogen temperature (Ge-LNT) by cluster evaporation technique. Raman measurement demonstrates the increase in strain with annealing in diffused disordered Si at the interface between Ge-LNT clusters and Si substrate. This manifests in strain-relaxation in the clusters as observed by Photoluminescence (PL) measurements. The decrease in PL intensity for Ge-RT with annealing has been attributed to reduction in surface oxide species, which is supported by Raman spectroscopic measurements. The objective of the paper is to understand the effect of thermal annealing on both interfacial strain and interdiffusion of elemental Si at the interface, together with luminescence characteristics of the clusters.
Production and study of metal-fullerene films
Dmitry V. Schur, Eduard M. Shpilevsky, Mykola M. Baklanov, et al.
The present paper describes the metal-fullerene films production by thermal evaporation and condensation under vacuum. The necessary fullerene concentration in the film has been provided by maintaining a special relation between the rates of fullerene and metal atoms fed. The preformed research of structure of fullerene containing materials show that addition of C60 molecules to the metal coatings essentially reduces the structural elements sizes to nanometrical ones that can be used in production of nanostructural materials having unique properties. The obtained result on investigation of their physical and physico-chemical properties suggest broad potentials for application of metal-fullerene films.
New formulation of the coupled mode method for the analysis of chirowaveguides
Alvaro Gomez, Miguel Angel Solano, Angel Vegas
In this communication we present a formulation of the Coupled Mode Method (CMM) which is different from the one normally used in the literature for solving chirowaveguides. An essential step in the development of the CMM is the way in which the longitudinal components of the electromagnetic field are related to the transverse components of the electromagnetic field. An approach which involves some previous manipulation of the constitutive relations is normally used. This gives a slow convergence of the propagation constants. In previous works, involving isotropic and anisotropic dielectric guides, we have shown that a different way of using the constitutive relations produces faster convergence of the propagation constants to the correct results for the different modes. Following this approach, we show here how this formulation can be applied to a parallel plate waveguide partially filled with different slabs of chiral media. Our results show that the predictions are confirmed in the same way as for anisotropic media.
Magnetic films with periodically striped domains as tunable photonic crystals
Igor L. Lyubchanskii, N. N. Dadoenkova, M. I. Lyubchanskii, et al.
Photonic band gaps (PBGs) in periodic magnetic films with striped domains separated by Bloch-type domain walls are investigated. Calculations for yttrium iron garnet (YIG) films are performed using the transfer matrix method. The dependence of forbidden gaps in the electromagnetic wave spectrum on the thicknesses of magnetic domains is numerically studied.
Electromagnetic properties of super-lattice in the long wavelength regime
Alexei P. Vinogradov, Alexander M. Merzlikin
Is shown that the fulfillment of long-wavelength approximation does not guarantee correct introduction of the effective constitutive parameters and for one-dimensional heterogeneous system if one tries to take into account effects of spatial dispersion (retardation on an elementary layer). Is shown that though in one-dimensional periodic medium the effective wavenumber tends to the well-known Rytov's value as the sample thickness tends to infinity whereas the effective characteristic impedance does not tend to any limit at all, exhibiting periodical behavior. This results in strong dependence of the effective constitutive parameters on sample thickness. The deviation of the finite sample values from Rytov's values may achieve 100 percent even in the long-wavelength limit.
Large third-order nonlinear optical susceptiblity of Rh: BaTiO3 thin films prepared by PLD
Guang Yang, Zhenghao Chen, Huibin Lu, et al.
Highly c-axis oriented Rh-doped BaTiO3 thin films were grown on MgO substrates by pulsed laser deposition using a single-crystal Rh:BaTiO3 target. THE 150 nm-thick films were deposited at 800 degrees C under the oxygen pressure of 7 by 10-2 Pa. The structural properties of the samples were characterized by x-ray diffraction and atomic force microscopy. The full width at half-maximum of the (002) Rh:BaTiO3 rocking curve and the root-mean-square surface roughness within the 5 by 5 micrometers 2 area were 0.520 degrees and 0.85 nm, respectively. The nonlinear optical properties of the films were determined by a single beam z-scan at a wavelength of 532 nm with laser duration of 10 ns. The result shows that Rh:BaTiO3 thin films exhibit a great nonlinear optical response with the real and imaginary parts of the third-order nonlinear optical susceptibility (chi) (3) being 3.59 X 10-7 esu and 4.01 X 10-8 esu, respectively.
Complex nanostructured silicon wire
Alla Ivanova Klimovskaya, Petro M. Lytvin, Nikolay Grigor'ev, et al.
Growth of silicon nanoobjects integrated to silicon based electronic circuits is of great importance for nano-, opto-electronics as well microsensorics. In this work, self-organizing technology has been used to grow silicon wires of complex structure on silicon substrate. To characterize the wires different high-resolution instruments (Hitachi SEM S806, CM 200 UT Philips) have been used. It was found that a morphology and crystalline structure of the wires are controlled by growth conditions. In general, the wires consist of a c-Si core and a Si-based envelope. A thickness of the core ranges between 50 to 500 nm, while a thickness of the envelope changes from few to few hundreds of nanometers. Morphology of the envelope is very sensitive to the growth conditions. Depending on the conditions it consists of amorphous or nanoporous silicon or silicon quasi-crystal. Nanopores in porous envelope have semi-spherical shape, and their sizes range between 0.4 to 20 nm. Nanopores are ordered into a superlattice or in a layered heterostructure with separating amorphous layers. Phenomena of the wire growth and possible applications of the wires grown on silicon substrate (as field transistors, electron- or light-emitters and chemical sensors) are discussed.
Modeling capacitance effect in organic polymers
We have developed an extension of the Drude model for oscillators to determine capacitance in organic polymers. The extension covers the effect of time delay caused by dispersion in the carrier transport. This was done using a complex mobility parameter. Negative capacitance effect could be observed in simulation at low frequencies provided that model parameters are appropriately chosen. In matching the simulation results to a set of data reported, we have computed very reasonable values of the transport parameters in regimes where either positive capacitance or negative capacitance is dominant. Simplified equations based on the model were highlighted to accommodate for specific instances where the transport parameters could be directly extracted. We believe our model is a better approach to extract transport parameters from capacitance-frequency curves when detailed conduction processes could not be easily identified such as in an environment of disordered complex molecules.
Microwaves and Left-handed Materials
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On mediums with negative phase velocity: a brief overview
Akhlesh Lakhtakia, Martin W. McCall, Werner S. Weiglhofer, et al.
Several issues relating to oppositely directed phase velocity and power flow are reviewed. A necessary condition for the occurrence of this phenomenon in isotropic dielectric-magnetic mediums is presented. Ramifications for aberration-free lenses, homogenization approaches, and complex mediums are discussed.