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1.
光学特异材料的设计 总被引:2,自引:0,他引:2
Christian Helgert Thomas Pertsch Carsten Rockstuhl Ekaterina PshenaySeverin Christoph Menzel ErnstBernhard Kleyet.al 《中国光学》2010,3(1):1-10
In this contribution we review our latest achievements of combined experimental and theoretical studies to tailor the properties of optical metamaterials(MMs) at will. We give three examples of metamaterial designs that have been realized by means of electron-beam lithography and whose spectroscopic characteristics have been comprehensively investigated. In every case, our experiments are complemented by rigorous numer ical simulations. Particular emphasis is put on the significance of such tailored effective properties of optical MMs 相似文献
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We present transmission increased fused silica lenses produced by using self-organized antireflective structures for which we developed an efficient manufacturing process. The spectral transmission measured over the whole lens aperture shows a significant transmission enhancement of up to 3.5% in the UV range. Local measurements on the lens's surface reveal a strongly reduced reflection of below 0.1% for 300 nm wavelength, which is homogeneous over the whole lens. Further, the lenses show a broadband spectral antireflection behavior. For 600 nm wavelength the reflection was measured at about 1%. 相似文献
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C. Helgert C. Rockstuhl C. Etrich E.-B. Kley A. T��nnermann F. Lederer T. Pertsch 《Applied Physics A: Materials Science & Processing》2011,103(3):591-595
We consider the effect of disorder in one transverse dimension, termed anisotropic disorder, on the optical properties of a metamaterial consisting of cut-wire-pair meta-atoms. The work comprises experimental and numerical studies. The appropriate samples were fabricated and their optical properties quantified in the far-field. For comparison large-scale rigorous numerical simulations were performed. We observe excellent agreement between experiment and theory. Based on our results we reveal how the electric dipole interactions between adjacent meta-atoms affect the overall spectral response of the metamaterial. Our main observation is a polarization-sensitive degradation of the symmetric resonance for anisotropic disorder. 相似文献
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Menzel C Alaee R Pshenay-Severin E Helgert C Chipouline A Rockstuhl C Pertsch T Lederer F 《Optics letters》2012,37(4):596-598
Most left-handed metamaterials cannot be described by local effective permittivity or permeability tensors in the visible or near-infrared due to the mesoscopic size of the respective unit cells and the related strong spatial dispersion. We lift this problem and propose a metamaterial exhibiting artificial magnetism that does not suffer from this restriction. The artificial magnetism arises from the extreme coupling between both metallic films forming the unit cell. We show that its electromagnetic response can be properly described by biaxial local constitutive relations. A genuine biaxial left-handed fishnet metamaterial is suggested, which can be realized by atomic layer deposition to fabricate the nanoscaled spacing layers required for extreme coupling. 相似文献
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M. Helgert L. Wenke S. Hvilsted P.S. Ramanujam 《Applied physics. B, Lasers and optics》2001,72(4):429-433
Light-induced surface modification of a series of liquid-crystalline side-chain azobenzene polyesters which have the same
main- and side-chain structure but eleven different substituents on the azobenzene is investigated. Using a transmission mask
as well as single focused beams we show that the formation of the surface relief is dependent on the substituents. In both
experiments irradiation with p-polarized light generates peaks for the CN, CF3, CH3 and F substituents, while for a Cl substituent valleys are observed. Also s-polarized light is found to produce surface deformations.
An amorphous azobenzene polyester was included in the study for comparison. The results point to a mechanism of the surface
relief phenomenon, in which the architecture of the polyesters plays a crucial role.
Received: 11 September 2000 / Revised version: 4 December 2000 / Published online: 21 February 2001 相似文献
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The microwave heating of two-dimensional slabs in a long rectangularwaveguide propagating the TE10 mode is examined. The temperaturedependency of the electrical conductivity and the thermal absorptivityis assumed to be governed by the Arrhenius law, while both theelectrical permittivity and the magnetic permeability are assumedconstant. The governing equations are the forced heat equationand the steady-state version of Maxwell's equation while theboundary conditions take into account both convective and radiativeheat loss. Approximate analytical solutions, valid for smallthermal absorptivity, are found for the temperature and theelectric-field amplitude using the Galerkin method. As the Arrheniuslaw is not amenable analytically, it is approximated by a rational-cubicfunction. At the steady state the temperature versus power relationshipis found to be multivalued; at the critical power level thermalrunaway occurs when the temperature jumps from the lower (cool)temperature branch to the upper (hot) temperature branch ofthe solution. In the steady-state limit the approximate analyticalsolutions are compared with the numerical solutions of the governingequations for various special cases. These are the limits ofsmall and large heat loss and an intermediate case involvingradiative heat loss. Results are also presented for a case wheredifferential cooling occurs on the different sides on the slab.An alternative heating scenario, where one end of the waveguideis blocked by a short, is also considered. The approximate solutionsare found for this geometry and compared in the small Biot-numberlimit to Kriegsmann (1997). Also, a control process is presented,which allows thermal runaway to be avoided and the desired finalsteady state to be reached. Various special cases of the feedbackparameters associated with the control process are examined. 相似文献
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Andreas?Lüthi Martin?A?Wikstr?m Mary?J?Palmer Paul?Matthews Tim?A?Benke John?TR?Isaac Graham?L?CollingridgeEmail author 《BMC neuroscience》2004,5(1):44
Background
Knowledge of how synapses alter their efficiency of communication is central to the understanding of learning and memory. The most extensively studied forms of synaptic plasticity are long-term potentiation (LTP) and its counterpart long-term depression (LTD) of AMPA receptor-mediated synaptic transmission. In the CA1 region of the hippocampus, it has been shown that LTP often involves a rapid increase in the unitary conductance of AMPA receptor channels. However, LTP can also occur in the absence of any alteration in AMPA receptor unitary conductance. In the present study we have used whole-cell dendritic recording, failures analysis and non-stationary fluctuation analysis to investigate the mechanism of depotentiation of LTP. 相似文献9.
Bauer EB Andavan GT Hollis TK Rubio RJ Cho J Kuchenbeiser GR Helgert TR Letko CS Tham FS 《Organic letters》2008,10(6):1175-1178
The scope of CCC-NHC pincer complex synthetic methodology by metalation/transmetalation has been extended to Ir. Structural characterization revealed that it is isomorphous with the Rh complex. Both Rh and Ir complexes are efficient catalysts for the hydroamination/cyclization of secondary amines in the presence of air and/or water. 相似文献
10.
Photoinduced deformation of azobenzene polyester films 总被引:1,自引:0,他引:1