Sökning: "ionic crystals"

Visar resultat 16 - 20 av 30 avhandlingar innehållade orden ionic crystals.

  1. 16. Calculations of Linear and Nonlinear Optical Properties of Ionic Crystal Surfaces and Fullerenes

    Författare :Erik Westin; Chalmers tekniska högskola; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES;

    Sammanfattning : Electronic and optical properties of ionic crystal surfaces and fullerenes have been studied by means of cluster calculations based on the Local Density Approximation (LDA) method using a numerical LCAO approach. The calculations for the bulk, stoichiometric and non-stoichiometric (111) surfaces of the divalent ionic crystals, CaF2 and BaF2, were based on the construction of an appropriate cluster of Ba++/Ca++ and F- ions representing a local environment of the specific system. LÄS MER

  3. 17. Application of computer techniques to the investigation of optical properties of focusing devices and to the calculation of cohesive energy and elastic constants of ionic crystals

    Författare :Göran Pettersson; Uppsala universitet; []
    Nyckelord :NATURAL SCIENCES; NATURVETENSKAP;

    Sammanfattning : .... LÄS MER

  4. 18. Polar molecules in crystalline and surface environments : From first principles

    Författare :Maria Alfredsson; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Chemistry; Kemi; Chemistry; Kemi; Inorganic Chemistry; oorganisk kemi;

    Sammanfattning : With the knowledge of the composition and structure of a chemical system, be it a molecule, a two-dimensional surface or a three-dimensional crystal, it is now possible to predict the specific properties of the compound under consideration via computational studies. Molecular and periodic Hartree-Fock and DFT calculations have been used as a tool to study polar molecules and how their properties respond to the molecular environment in a crystal or on an ionic surface. LÄS MER

  5. 19. Fabrication and characterization of periodically poled KTB and RB-doped KTB for applications in the visible and UV

    Författare :Shunhua Wang; Fredrik Laurell; Peter Smith; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Nonlinear optics; second-harmonic generation; quasi-phasematching; type-I QPM SHG; type-II QPM SHG; KTP; RKTP; periodic electric-field poling; Physics; Fysik;

    Sammanfattning : This thesis deals with the fabrication and the characterization of periodically-poled crystals for use in lasers to generate visible and UV radiation by second-harmonic generation (SHG) through quasi-phasematching (QPM). Such lasers are of practical importance in many applications like high-density optical storage, biomedical instrumentation, colour printing, and for laser displays. LÄS MER

  7. 20. QPM Devices in KTA and RKTP

    Författare :Andrius Zukauskas; Carlota Canalias; Moti Katz; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; NATURVETENSKAP; NATURAL SCIENCES; QPM; periodic poling; KTP;

    Sammanfattning : Even though KTiOPO4 (KTP) is considered to be one of the best nonlinear materials for quasi phase matched (QPM) frequency conversion in the visible and the near-infrared spectral regions, its use is often limited by poor material homogeneity, high ionic conductivity, a considerable linear absorption and photochromatic damage. On the other hand, the improved material homogeneity and the lower ionic conductivity of bulk Rb-doped KTP (RKTP) make this material an ideal alternative for fabrication of fine-pitch QPM gratings, while the arsenate isomorph KTiOAsO4 (KTA) promises a better performance in the green spectral region and adds the advantage of a wider transparency window in the infrared. LÄS MER