Internal Josephson Oscillations for Distinct Momenta Bose-Einstein Condensates

The internal Josephson oscillations between an atomic Bose-Einstein condensate (BEC) and a molecular one are studied for atoms in a square optical lattice subjected to a staggered gauge field. The system is described by a Bose-Hubbard model with complex and anisotropic hopping parameters that are different for each species, i.e., atoms and molecules. When the flux per plaquette for each species is small, the system oscillates between two conventional zero-momentum condensates. However, there is a regime of parameters in which Josephson oscillations between a vortex-carrying atomic condensate (finite momentum BEC) and a conventional zero-momentum molecular condensate may be realized. The experimental observation of the oscillations between these qualitatively distinct BEC's is possible with state-of-the-art Ramsey interference techniques.Comment: 8 pages, 6 figure

Graphene Oxide alpha Bi2O3 Composites for Visible Light Photocatalysis, Chemical Catalysis and Solar Energy Conversion

The growing challenges of environmental purification by solar photocatalysis, precious metal free catalysis and photocurrent generation in photovoltaic cells are receiving the utmost global attention. Here we demonstrate the one pot green chemical synthesis of a new stable heterostructured, eco friendly, multifunctional micro composite consisting of amp; 945; Bi2O3 micro needles intercalated with anchored graphene oxide GO micro sheets 1.0 wt for the above mentioned applications in a large economical scale. The bare amp; 945; Bi2O3 micro needles display twice as better photocatalytic activities than commercial TiO2 Degussa P25 while the GO hybridized composite exhibit 4 6 times enhanced photocatalytic activities than neat TiO2 photocatalyst in the degradation of colored aromatic organic dyes crystal violet and rhodamine 6G under visible light irradiation 300 W tungsten lamp . The highly efficient activity is associated with the strong surface adsorption ability of GO for aromatic dye molecules, the high carrier acceptability and efficient electron hole pair separation in Bi2O3 by individual adjoining GO sheets. Introduction of Ag nanoparticles 2.0 wt further enhances the photocatalytic performance of the composite over 8 folds due to a plasmon induced electron transfer process from Ag nanoparticles via GO sheets into the conduction band of Bi2O3. The new composites are also catalytically active. They catalyze the reduction of 4 nitrophenol to 4 aminophenol in presence of borohydride ions. Photoanodes assembled from GO amp; 945; Bi2O3 and Ag GO amp; 945; Bi2O3 composites display an improved photocurrent response power conversion efficiency 20 higher over those prepared without GO in dye sensitized solar cells DSSCs

Towards integrated continuous wave THz systems

We present a photonic integrated circuit, which enables the full control of the THz signal in continuous wave photomixing THz systems via standard electronics. The device comprises two DFB-lasers and an optical phase modulator on a single chip. Due to a unique bidirectional operation technique, the chip provides the optical beat signal for both THz emitter and THz receiver and allows for manipulation of the THz phase via the optical phase modulator. To evaluate the performance of our solution, we realize a coherent cw THz system based on our photonic integrated circuit and compare it to discrete lasers and standard components. As the results show, both setups feature an identical signal-to-noise ratio, reaching 50 dB at a frequency of 1 THz for an integration time of 500 ms. This is the best reported performance of CW photomixing systems running at 1.5 µm optical wavelength

40 Gbit/s directly modulated passive feedback laser with complex-coupled DFB section

40 Gbit/s open eyes are demonstrated for a passive feedback laser transmitter with complex coupled DFB section. The transmitter shows superior single mode emission in combination with chirp tuning capability and high reliability. For a multisection PFL transmitter including a complex-coupled DFB section optical modulation bandwidth of 30 GHz and open eyes for large signal 40 Gbit/s direct current modulation with 6 dB extinction ratio have been demonstrated. The device shows high single mode stability under varying phase conditions of the integrated feedback which is necessary for optical bandwidth enhancement. For data rates below 40 Gbit/s, the PFL structure has the potential to be applied for feedback controlled chirp management, thus opening up a huge potential for applications in new highly dispersion tolerant modulation formats. Reasonable life times of about 100000 h could be estimated proving reliable technological fabrication. Entnommen aus TEMA</a

Bismuth Hexagons: Facile Mass Synthesis, Stability and Applications

A unique direct electrodeposition technique involving very high current densities, high voltages and high electrolyte concentrations is applied for highly selective mass synthesis of stable, isolable, surfactant-free, single-crystalline Bi hexagons on a Cu wire at room temperature. A formation mechanism of the hexagons is proposed. The morphology, phase purity, and crystallinity of the material are well characterized by FESEM, AFM, TEM, SAED, EDX, XRD, and Raman spectroscopy. The thermal stability of the material under intense electron beam and intense laser light irradiation is studied. The chemical stability of elemental Bi in nitric acid shows different dissolution rates for different morphologies. This effect enables a second way for the selective fabrication of Bi hexagons. Bi hexagons can be oxidized exclusively to α-Bi2O3 hexagons. The Bi hexagons are found to be promising for thermoelectric applications. They are also catalytically active, inducing the reduction of 4-nitrophenol to 4-aminophenol. This electrodeposition methodology has also been demonstrated to be applicable for synthesis of bismuth-based bimetallic hybrid composites for advanced applications

Vollfarb-Elektrolumineszenz auf der Basis von II&quot;a-VI&quot;a-Verbindungen Abschlussbericht

Available from TIB Hannover: F01B392+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Neue Blauphosphore fuer vollfarbige Elektrolumineszenzdisplays Abschlussbericht

Available from TIB Hannover: F01B393+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman