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Gopal A.,Friedrich - Schiller University of Jena | Gopal A.,Helmholtz Center for Heavy Ion Research | Herzer S.,Friedrich - Schiller University of Jena | Herzer S.,Helmholtz Center for Heavy Ion Research | And 12 more authors.
Physical Review Letters | Year: 2013

We report the observation of subpicosecond terahertz (T-ray) pulses with energies ≥460 μJ from a laser-driven ion accelerator, thus rendering the peak power of the source higher even than that of state-of-the-art synchrotrons. Experiments were performed with intense laser pulses (up to 5×1019 W/cm2) to irradiate thin metal foil targets. Ion spectra measured simultaneously showed a square law dependence of the T-ray yield on particle number. Two-dimensional particle-in-cell simulations show the presence of transient currents at the target rear surface which could be responsible for the strong T-ray emission. © 2013 American Physical Society.


Stockel S.,Friedrich - Schiller University of Jena | Meisel S.,Friedrich - Schiller University of Jena | Elschner M.,Friedrich Loeffler Institute | Rosch P.,Friedrich - Schiller University of Jena | And 2 more authors.
Angewandte Chemie - International Edition | Year: 2012

Better safe than sorry: A combined analytical procedure consisting of Raman spectroscopy and chemometrics can be used to test for anthrax endospores in environmental samples. Time-consuming enrichment steps are not required and low levels of anthrax endospores in household substances like baking powder can be detected within 3h and discriminated against other nonpathogenic Bacillus species with typing accuracies of up to 99 %. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Vargas Jentzsch P.,Friedrich - Schiller University of Jena | Ciobota V.,Friedrich - Schiller University of Jena | Rosch P.,Friedrich - Schiller University of Jena | Popp J.,Friedrich - Schiller University of Jena | Popp J.,Institute For Photonische Technologien
Angewandte Chemie - International Edition | Year: 2013

Climate science: When different salts occurring in atmospheric particles combine during a coagulation process and interact with humid air, some reactions can take place and modify the salt composition (see picture). The hygroscopicity of certain salts favors the formation of a liquid H2O film on the solid material. The salts partially dissolve and the ions can react with each other. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Frosch T.,Friedrich - Schiller University of Jena | Frosch T.,Institute For Photonische Technologien | Popp J.,Friedrich - Schiller University of Jena | Popp J.,Institute For Photonische Technologien
Journal of Biomedical Optics | Year: 2010

The structure of the antimalarial drug halofantrine is analyzed by means of density functional theory (DFT) calculations, IR, and Raman spectroscopy. Strong, selective enhancements of the Raman bands of halofantrine at 1621 and 1590 cm -1 are discovered by means of UV resonance Raman spectroscopy with excitation wavelength γ exc=244 nm. These signal enhancements can be exploited for a localization of small concentrations of halofantrine in a biological environment. The Raman spectrum of halofantrine is calculated by means of DFT calculations [B3LYP/6-311 + G(d,p)]. The calculation is very useful for a thorough mode assignment of the Raman bands of halofantrine. The strong bands at 1621 and 1590 cm -1 in the UV Raman spectrum are assigned to combined C=C stretching vibrations in the phenanthrene ring of halofantrine. These bands are considered as putative marker bands for tttt interactions with the biological target molecules. The calculation of the electron density demonstrates a strong distribution across the phenanthrene ring of halofantrine, besides the electron withdrawing effect of the Cl and CF 3 substituents. This strong and even electron density distribution supports the hypothesis of ππ stacking as a possible mode of action of halofantrine. Complementary IR spectroscopy is performed for an investigation of vibrations of polar functional groups of the halofantrine molecule. © 2010 Society of Photo-Optical Instrumentation Engineers.


Popp A.,University of Stuttgart | Voss A.,University of Stuttgart | Graf T.H.,University of Stuttgart | Unger S.,Institute For Photonische Technologien | And 2 more authors.
Laser Physics Letters | Year: 2011

We report on an ytterbium-doped fiber laser (FL) remotely pumped by a commercial Yb:YAG thin-disk laser with a beam parameter product of 4 mm mrad and an emission wavelength of 1030 nm. The pump light absorption is 1.4 dB/m, which is 77 times lower than the peak value at 976 nm. The high-brilliance pumped fiber laser with a double pass of the pump light yielded a maximum output power of 1008 W out of 1264 W pump power. Despite the low pump absorption at 1030 nm, this kW-fiber laser reaches an excellent opticalto-optical efficiency of 80%. This concept of high-brilliance pumping enables to overcome the nonlinear effects limiting high-power high-brightness beam delivery over long distances and offers a power scalability fiber lasers paired with flexibility in the application. © 2011 by Astro Ltd., published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA.


Il'ichev E.V.,Institute For Photonische Technologien
Fizika Nizkikh Temperatur | Year: 2013

Based on the numerical solution of nonstationary Ginzburg-Landau equations, we investigated the evolution of the order parameter of superconducting channels of different length under applied voltage (socalled voltage-driven regime). We calculated the current- voltage characteristics for channels of different length and found out the origin of theirs characteristic disorder oscillations. For very long channels in a certain voltage interval we revealed a chaotic dynamics of the order parameter. The collected data allowed us to plot the most complete and detailed phase diagram of the resistive state of the superconducting channel in the voltage-driven regime.


Il'ichev E.,Institute For Photonische Technologien
Fizika Nizkikh Temperatur | Year: 2013

The transmission coefficient of microwave wave-guide lines with different Josephson junction circuits has been calculated. The resonance modes in lines manifest themselves as sharp dips in the transmission power. The shape and the position of these dips de-pend both on external magnetic field and applied mi-crowave power. The results of calculation can be use-ful for design and implementation of modern cryoelectronics microwave superconducting devices.


Sivakov V.A.,Institute For Photonische Technologien | Bronstrup G.,Institute For Photonische Technologien | Pecz B.,Hungarian Academy of Sciences | Berger A.,Institute For Photonische Technologien | And 5 more authors.
Journal of Physical Chemistry C | Year: 2010

Silicon nanowire (SiNW) ensembles with vertical and zigzag architectures have been realized using wet chemical etching of bulk silicon wafers (p-Si(111) and p-Si(100)) with a mask of silver nanoparticles that are deposited by wet electroless deposition. The etching of SiNWs is based on subsequent treatments in chemical solutions such as 0.02 M aqueous solutions of silver nitrate (AgNO3) followed by 5 M hydrofluoric acid and 30% hydrogen peroxide (H2O2). The etching of the Si wafers is mediated by the reduction of silver on the silicon surface and in parallel by the oxidation of Si thereby forming SiO2 which is dissolved in the HF surroundings. The morphology of the starting silver (Ag) layer/Ag nanoparticles that form during processing on the Si wafer surfaces strongly influences the morphology of the SiNW ensembles and homogeneity of the etch profile. Our observations suggest that the Ag layer/Ag nanoparticles not only catalyze the wet chemical etching of silicon but also strongly catalyze the decomposition of H 2O2so that the temperature of the etching solution substantially increases (strong exothermic reaction) and thus the etching velocity of bulk material. The morphology and microstructure of single crystalline SiNWs with respect to their crystallographic orientation was investigated by scanning (SEM) and transmission electron (TEM) microscopies and by electron backscatter diffraction (EBSD) in an SEM. Straight SiNWs as well as zigzag SiNWs can be realized depending on processing peculiarities. The optical characteristics such as absorption, transmission, and reflectance of the different silicon 1D architectures were investigated in an integrating sphere. Strong absorption and less reflection of visible and near-infrared light by the SiNW ensembles suggest that such material can be applied in the fields of opto-electronics, photonics and photovoltaics. © 2010 American Chemical Society.


Gompf B.,University of Stuttgart | Braun J.,University of Stuttgart | Weiss T.,University of Stuttgart | Giessen H.,University of Stuttgart | And 2 more authors.
Physical Review Letters | Year: 2011

Polarization rotation in isotropic materials is commonly associated with chirality, i.e., structures with a handedness which are not identical with their mirror image. We observe this effect in the visible and near-IR regions at oblique incidence in the optical response of a subwavelength square array of holes. Mapping the complete k→ space via Mueller-matrix spectroscopic ellipsometry, we find that in specific directions the rotary power is orders of magnitude larger than that observed for chiral molecules. Although experimentally indistinguishable, the physics behind the two phenomena is fundamentally different: While optical activity is a consequence of magnetic interactions, nanostructures on a square lattice rotate the polarization due to spatial dispersion. © 2011 American Physical Society.


Braun J.,University of Stuttgart | Gompf B.,University of Stuttgart | Weiss T.,University of Stuttgart | Giessen H.,University of Stuttgart | And 2 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

Contrary to thick opaque metal films, where an extraordinary high transmission of light is observed through subwavelength hole arrays, in ultrathin metal films perforation can lead to a suppressed or an enhanced transmission. Here we systematically investigate the optical transmission through semitransparent Au films structured with square arrays of subwavelength holes experimentally and theoretically. We measure the transmission at various angles of incidence through hole arrays with different thicknesses, diameters, and periodicities. We compare the data with an empty lattice approximation and with calculations based on a Fourier modal method. The results evidence that for gold the exact dielectric function has to be considered and that not only the periodicity and film thickness influences the transmission, but that also the shape and diameter of the holes play an important role. © 2011 American Physical Society.

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