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  • 201.
    Schmidt, Daniel
    et al.
    Department of Electrical Engineering and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE, USA.
    Müller, Christian
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Hofmann, Tino
    Department of Electrical Engineering and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE, USA.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Schubert, Eva
    Department of Electrical Engineering and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE, USA.
    Schubert, Mathias
    Department of Electrical Engineering and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE, USA.
    Optical properties of hybrid titanium chevron sculptured thin films coated with a semiconducting polymer2011Inngår i: THIN SOLID FILMS, ISSN 0040-6090, Vol. 519, nr 9, s. 2645-2649Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Optical and structural properties of a hybrid metallic chevron sculptured thin film from titanium coated with the semiconducting polymer poly(3-dodecylthiophene) (P3DDT) are reported. The nanostructured thin film with two subsequent layers of oppositely slanted nanocolumns was fabricated by glancing angle deposition and coated with P3DDT by a spin-cast process. Spectroscopic generalized ellipsometry is employed to determine geometrical structure properties and the anisotropic optical constants of the coated and uncoated film in the spectral range from 400 to 1700 nm. The nanostructured thin films before and after hybridization show highly anisotropic optical properties. The complex refractive indices along major polarizability directions of the hybridized chevrons are increased in the entire investigated spectral range with respect to the as-deposited chevrons. Changes in birefringence and dichroism upon polymer infiltration are observed.

  • 202.
    Schmidt, Susann
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Hänninen, Tuomas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Goyenola, Cecilia
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Wissting, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska fakulteten.
    Jensen, Jens
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Goebbels, Nico
    IHI Ionbond AG, Switzerland.
    Tobler, Markus
    IHI Ionbond AG, Switzerland.
    Högberg, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    SiNx Coatings Deposited by Reactive High Power Impulse Magnetron Sputtering: Process Parameters Influencing the Nitrogen Content2016Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 8, nr 31, s. 20386-20396Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Reactive high power impulse magnetron sputtering (rHi-PIMS) was used to deposit silicon nitride (SiNx) coatings for biomedical applications. The SiNx growth and plasma characterization were conducted in an industrial coater, using Si targets and N-2 as reactive gas. The effects of different N-2-to-Ar flow ratios between 0 and 0.3, pulse frequencies, target power settings, and substrate temperatures on the discharge and the N content of SiNx coatings were investigated. Plasma ion mass spectrometry shows high amounts of ionized isotopes during the initial part of the pulse for discharges with low N-2-to-Ar flow ratios of amp;lt;0.16, while signals from ionized molecules rise with the N-2-to-Ar flow ratio at the pulse end and during pulse off times. Langmuir probe measurements show electron temperatures of 2-3 eV for nonreactive discharges and 5.0-6.6 eV for discharges in transition mode. The SiNx coatings were characterized with respect to their composition, chemical bond structure, density, and mechanical properties by X-ray photoelectron spectroscopy, X-ray reflectivity, X-ray diffraction, and nanoindentation, respectively. The SiNx deposition processes and coating properties are mainly influenced by the Nz-to-Ar flow ratio and thus by the N content in the SiNx films and to a lower extent by the HiPIMS frequencies and power settings as well as substrate temperatures. Increasing N2-to-Ar flow ratios lead to decreasing growth rates, while the N content, coating densities, residual stresses, and the hardness increase. These experimental findings were corroborated by density functional theory calculations of precursor species present during rHiPIMS.

  • 203.
    Schmidt, Susann
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Hänninen, Tuomas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Wissting, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska fakulteten.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Goebbels, N.
    IHI Ionbond AG, Switzerland.
    Santana, A.
    IHI Ionbond AG, Switzerland.
    Tobler, M.
    IHI Ionbond AG, Switzerland.
    Högberg, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    SiNx coatings deposited by reactive high power impulse magnetron sputtering: Process parameters influencing the residual coating stress2017Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 121, nr 17, artikkel-id 171904Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The residual coating stress and its control is of key importance for the performance and reliability of silicon nitride (SiNx) coatings for biomedical applications. This study explores the most important deposition process parameters to tailor the residual coating stress and hence improve the adhesion of SiNx coatings deposited by reactive high power impulse magnetron sputtering (rHiPIMS). Reactive sputter deposition and plasma characterization were conducted in an industrial deposition chamber equipped with pure Si targets in N-2/Ar ambient. Reactive HiPIMS processes using N-2-to-Ar flow ratios of 0 and 0.28-0.3 were studied with time averaged positive ion mass spectrometry. The coatings were deposited to thicknesses of 2 mu m on Si(001) and to 5 mu m on polished CoCrMo disks. The residual stress of the X-ray amorphous coatings was determined from the curvature of the Si substrates as obtained by X-ray diffraction. The coatings were further characterized by X-ray photoelectron spectroscopy, scanning electron microscopy, and nano-indentation in order to study their elemental composition, morphology, and hardness, respectively. The adhesion of the 5 mu m thick coatings deposited on CoCrMo disks was assessed using the Rockwell C test. The deposition of SiNx coatings by rHiPIMS using N-2-to-Ar flow ratios of 0.28 yield dense and hard SiNx coatings with Si/N ratios amp;lt; 1. The compressive residual stress of up to 2.1 GPa can be reduced to 0.2 GPa using a comparatively high deposition pressure of 600 mPa, substrate temperatures below 200 degrees C, low pulse energies of amp;lt; 2.5 Ws, and moderate negative bias voltages of up to 100 V. These process parameters resulted in excellent coating adhesion (ISO 0, HF1) and a low surface roughness of 14 nm for coatings deposited on CoCrMo. (C) 2017 Author(s).

  • 204.
    Schubert, Mattias
    et al.
    Faculty of Physics and Geosciences, Inst. of Experimental Physics II University of Leipzig.
    Bundesmann, C.
    Faculty of Physics and Geosciences, Inst. of Experimental Physics II University of Leipzig.
    Jacopic, G.
    Institut für Nanostrukturierte Materialien und Photonik JOANNEUM Research Forschungsgesellschaft mbH.
    Maresch, H.
    Institut für Nanostrukturierte Materialien und Photonik JOANNEUM Research Forschungsgesellschaft mbH.
    Arwin, Hans
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik.
    Infrared dielectric function and vibrational modes of pentacene thin films2004Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 84, nr 2, s. 200-202Artikkel i tidsskrift (Fagfellevurdert)
  • 205.
    Schubert, Mattias
    et al.
    Inst for Experimental Physics II University of Leipzig.
    Bundesmann, C.
    Inst for Experimental Physics University of Leipzig.
    Jacopic, G.
    JOANNEUM Research Forschungsgesellschaft mbH, Austria.
    Maresch, H.
    JOANNEUM Research Forschungsgesellschaft Mbh, Austria.
    Arwin, Hans
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik.
    Persson, Nils-Krister
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik.
    Zhang, Fengling
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik.
    Inganäs, Olle
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik.
    Infrared ellipsometry characterization of conducting thin organic films2004Inngår i: Elsevier Science, ISSN 1626-3200, Vol. 455-456, s. 295-300Artikkel i tidsskrift (Fagfellevurdert)
  • 206.
    Schubert, Mattias
    et al.
    Fakultät für Physik und Geowissenschaften Institut für Experimentelle Physik II, Leipzig.
    Bundesmann, C.
    Fakultät für Physik und Geowissenschaften Institut für Experimentelle Physik II, Leipzig.
    v. Wenckstern, H.
    Fakultät für Physik und Geowissenschaften Istitut für Experimentelle Physik II, Leipzig.
    Jakopic, G.
    Institut für Nanostrukturierte Materialien und Photonik JOHANNEUM Research Forschungsgesellschaft mbH.
    Haase, A.
    Institut für Nanostrukturierte Materialien und Photonik JOANNEUM Research Forschungsgesellschaft mbH.
    Persson, Nils-Krister
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik.
    Zhang, Fengling
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik.
    Arwin, Hans
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik.
    Inganäs, Olle
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik.
    Carrier redistribution in organic/inorganic (poly(3,4-ethylenedioxy thiophene/poly(styrenesulfonate)polymer)-Si) heterojunction determined from infrared ellipsometry2004Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 84, s. 1311-1313Artikkel i tidsskrift (Fagfellevurdert)
  • 207.
    Souxa Dantas, Nilton
    et al.
    Dept of Materials Science and Engineering, Royal Institute of Technology, Sweden.
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Nzulu, Gabriel
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    de Olivera Rappl, Paulo Henrique
    Instituto Nacional de Pesquisas Espaciais, Brazil.
    Ferreira da Silva, Antonio
    Instituto de Fisica Universidade Federal da Bahia, Brazil.
    Persson, Clas
    Dept of Materials Science and Engineering, Royal Institute of Technology, Sweden.
    Optical characterization of rocksalt Pb1-xSnxTe alloys2008Inngår i: physica status solidi (a): Applications and Materials Science, ISSN 1862-6300, Vol. 205, nr 4, s. 837-840Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The optical properties in terms of dielectric function ε(hSω)= ε1(hSω)+iε2(hSω)of rocksalt pb 1-xsnx Te alloyes (0≤x≤1)are investigated experimentally by spectroscopic ellipsometry and theoretically by first-principles electronic band structure calculation. We find a strong optical response in the 0.5-2.0 eV region arising from optical absorption around the LW-line of the Brillouin zone. The response peak of the imaginary part of the dielectric functions at E = 1.6-1.8 eV shifts towards lower energies for high Sn compositions as a consequence of narrower W-point band-gap Eg(W) for the Sn-rich alloys, ©2008 WILEY-VCH Verlag GmbH & Co. KGaA.

  • 208.
    Tazawa, M.
    et al.
    National Institute of Advanced Industrial Science and Technology Japan.
    Xu, G.
    National Institute of Advanced Industrial Science and Technology Japan.
    Jin, P.
    National Institute of Advanced Industrial Science and Technology Japan.
    Arwin, Hans
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik.
    A memory application of light reflection from anisotropic microstructured thin films2004Inngår i: Elsevier Science, ISSN 1626-3200, Vol. 455-456, s. 824-827Artikkel i tidsskrift (Fagfellevurdert)
  • 209.
    Tazawa, Masato
    et al.
    National Institute of Advanced Industrial Science and Technology, Shidami, Moriyama-ku, Nagoya .
    Kakiuchida, Hiroshi
    National Institute of Advanced Industrial Science and Technology, Shidami, Moriyama-ku, Nagoya .
    Xu, Gang
    National Institute of Advanced Industrial Science and Technology, Shidami, Moriyama-ku, Nagoya .
    Jin, Ping
    National Institute of Advanced Industrial Science and Technology, Shidami, Moriyama-ku, Nagoya .
    Arwin, Hans
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik.
    Optical constants of vacuum evaporated SiO film and an application2006Inngår i: Journal of Electroceramics, ISSN 1385-3449, E-ISSN 1573-8663, Vol. 16, nr 4, s. 511-515Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Silicon monoxide films were deposited on silver films on glass substrates and studied by infrared ellipsometry to determine the optical properties in the infrared wavelength range from 1.3 to 40 micrometers. The thicknesses of silicon monoxide and aluminum films were designed to 1 micrometer and 200 nanometers, respectively. The ellipsometric measurements were carried out by using a spectro-ellipsometer attached with an FT-IR. The imaginary part of the refractive index shows a high absorption region which is centered at 10 micrometers, whereas in other wavelength regions it shows rather low absorption. The resultant optical properties of silicon monoxide film are compared with published data. As an application, the spectral reflectance of spectral selective panel heating surface is calculated.

  • 210.
    Tiwari, Ashutosh
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biosensorer och bioelektronik. Linköpings universitet, Tekniska högskolan.
    Valyukh, SergiyLinköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Advanced Energy Materials2014Collection/Antologi (Annet vitenskapelig)
    Abstract [en]

    An essential resource for scientists designing new energy materials for the vast landscape of solar energy conversion as well as materials processing and characterizatio.

    Based on the new and fundamental research on novel energy materials with tailor-made photonic properties, the role of materials engineering has been to provide much needed support in the development of photovoltaic devices. Advanced Energy Materials offers a unique, state-of-the-art look at the new world of novel energy materials science, shedding light on the subject's vast multi-disciplinary approach.

    The book focuses particularly on photovoltaics, efficient light sources, fuel cells, energy-saving technologies, energy storage technologies, nanostructured materials as well as innovating materials and techniques for future nanoscale electronics. Pathways to future development are also discussed.Critical, cutting-edge subjects are addressed, including:

    • Non-imaging focusing heliostat; state-of-the-art of nanostructures
    • Metal oxide semiconductors and their nanocomposites
    • Superionic solids; polymer nanocomposites; solid electrolytes; advanced electronics
    • Electronic and optical properties of lead sulfide
    • High-electron mobility transistors and light-emitting diodes
    • Anti-ferroelectric liquid crystals; PEEK membrane for fuel cells
    • Advanced phosphors for energy-efficient lighting
    • Molecular computation photovoltaics and photocatalysts
    • Photovoltaic device technology and non-conventional energy applicationsReadership

    The book is written for a large and broad readership including researchers and university graduate students from diverse backgrounds such as chemistry, materials science, physics, and engineering working in the fields of nanotechnology, photovoltaic device technology, and non-conventional energy.

  • 211.
    Tulldahl, Michael
    et al.
    IFM Tillämpad optik Linköpings universitet.
    Steinvall, K. Ove
    Swedish defence Research Agency Linköping.
    Arwin, Hans
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik.
    Simulation of sea surface wave influence on small target detection with airborne laser depth sounding2004Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A theoretical model for simulation of airborne depth-sounding lidar is presented with the purpose of analyzing the influence from water surface waves on the ability to detect 1-m3 targets placed on the sea bottom. Although water clarity is the main limitation, sea surface waves can significantly affect the detectability. The detection probability for a target at a 9-m depth can be above 90% at 1-m/s wind and below 80% at 6-m/s wind for the same water clarity. The simulation model contains both numerical and analytical components. Simulated data are compared with measured data and give realistic results for bottom depths between 3 and 10 m. © 2004 Optical Society of America.

  • 212.
    Tumenas, S
    et al.
    Institute for Semiconductor Physics, Vilnius .
    Karpus, V
    Institute for Semiconductor Physics, Vilnius .
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Assmus, W
    Goethe University Frankfurt.
    Optical conductivity of fci-ZnMgRE quasicrystals2011Inngår i: THIN SOLID FILMS, ISSN 0040-6090, Vol. 519, nr 9, s. 2951-2954Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The results of room-temperature spectroscopic ellipsometry study of single-grain face-centred icosahedral (fci) ZnMgY, ZnMgHo, and ZnMgEr quasicrystals in the spectral range of 0.1-6.5 eV are presented. Analysis of the optical conductivity spectra, carried out within a framework of the band structure hypothesis, reveals that an optical response of the fci-ZnMgRE quasicrystals is determined by a superposition of the intraband Drude-type contribution and that of the interband optical transitions across a pseudogap. The deduced parameters of the fci-ZnMgRE electron energy spectrum are close to their values determined previously from an analysis of the fci-ZnMgRE photoemission data.

  • 213.
    Tumenas, S
    et al.
    Institute for Semiconductor Physics, Vilnius, Lithuania .
    Kasalynas, I
    Institute for Semiconductor Physics, Vilnius, Lithuania .
    Karpus, V
    Institute for Semiconductor Physics, Vilnius, Lithuania .
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Infrared Reflectance Kramers--Kronig Analysis by Anchor-Window Technique2011Inngår i: ACTA PHYSICA POLONICA A, ISSN 0587-4246, Vol. 119, nr 2, s. 140-142Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An algorithm for the Kramers-Kronig analysis of the reflectivity spectra, based on an anchor-window technique is presented. The high-frequency asymptote, required for the Kramers-Kronig analysis, is determined by minimizing differences between the Kramers Kronig-deduced optical constants of a system under investigation and known optical constants measured in a small anchor-window. The algorithm is illustrated by applying it for a reconstruction of the optical conductivity sigma(omega) of the fci-ZnMgRE quasicrystals in the spectral range of 0.01-6.5 eV from the experimental IR Fourier-transform reflectivity data and the experimental spectral ellipsometry VIS-UV data. The reliability of the suggested Kramers-Kronig analysis technique is confirmed by independent infrared spectral ellipsometry sigma(omega) measurements for fci-ZnMgRE.

  • 214.
    Tumėnas, Saulius
    et al.
    Center for Physical Sciences and Technology, Vilnius.
    Karpus, Vytas
    Center for Physical Sciences and Technology, Vilnius.
    Kondrotas, R
    Center for Physical Sciences and Technology, Vilnius.
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik.
    Spectroscopic Ellipsometry Study of Monocrystalline Zn2013Konferansepaper (Annet vitenskapelig)
  • 215.
    Tumėnas, Saulius
    et al.
    Center for Physical Sciences and Technology, Vilnius, Lithuania.
    Karpus, Vytautas
    Center for Physical Sciences and Technology, Vilnius, Lithuania.
    Bertulis, Klemensas
    Center for Physical Sciences and Technology, Vilnius, Lithuania.
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Dielectric function and refractiveindex of GaBixAs1-x(x = 0.035, 0.052, 0.075)2012Inngår i: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 9, nr 7, s. 1633-1635Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    MBE grown GaBiAs epitaxial layers with Bi content of3.5 %, 5.2 %, and 7.5 %, sandwiched between GaAs,have been investigated by spectroscopic ellipsometry inthe infrared and absorption threshold spectral regions.The real and imaginary parts of the dielectric function ofGaBiAs indicate bandgap Eg and spin-orbit splitting Δ0+values close to literature data. The refractive index ofGaBiAs in the IR region 0.2–0.8 eV exceeds that ofGaAs by ca. 0.8 %, 2.3 %, and 3.6 %, for Bi content3.5 %, 5.2 %, and 7.5 %, respectively.

  • 216.
    Valyukh, I.
    et al.
    Dalarna University.
    Arwin, Hans
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik.
    Chiginov, V.
    Hong Kong University of Science and Technology.
    UV-induced in-plane anistropy in layers of mixtures of the azo-dyes SD1/SD2 characterized by spectroscopic ellipsometry2007Inngår i: 4th International Conference on Spectroscopic Ellipsometry,2007, Linköping: Linköpings universitet , 2007, s. 217-Konferansepaper (Fagfellevurdert)
  • 217.
    Valyukh, I
    et al.
    Dalarna University.
    Green, S
    Uppsala University.
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Niklasson, G A
    Uppsala University.
    Wackelgard, E
    Dalarna University.
    Granqvist, C G
    Uppsala University.
    Spectroscopic ellipsometry characterization of electrochromic tungsten oxide and nickel oxide thin films made by sputter deposition2010Inngår i: SOLAR ENERGY MATERIALS AND SOLAR CELLS, ISSN 0927-0248, Vol. 94, nr 5, s. 724-732Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Electrochromic films of tungsten oxide and nickel oxide were made by reactive dc magnetron sputtering and were characterized by X-ray diffraction, Rutherford backscattering spectrometry, scanning electron microscopy, and atomic force microscopy. The optical properties were investigated in detail by spectroscopic ellipsometry and spectrophotometry, using a multiple-sample approach. The W-oxide film was modeled as a homogeneous isotropic layer, whereas the Ni-oxide film was modeled as an anisotropic layer with the optical axis perpendicular to the surface. Parametric models of the two layers were then used to derive complex refractive index in the 300-1700 nm range, film thickness, and surface roughness. A band gap of 3.15 eV was found for the W-oxide film, using a Tauc-Lorentz parameterization. For the Ni-oxide film, taken to have direct optical transitions, band gaps along the optical axis, perpendicular to it, and in an isotropic intermediate layer at the bottom of the film were found to be 3.95, 3.97, and 3.63 eV, respectively. Parameterization for the Ni oxide was made by use of the Lorentz model.

  • 218.
    Valyukh, Iryna
    et al.
    Dalarna University, Borlänge, Sweden.
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Chigrinov, Vladimir
    Hong Kong University of Science and Technology, Kowloon, Hong Kong .
    Valyukh, Sergiy
    Hong Kong University of Science and Technology, Kowloon, Hong Kong .
    Characterization of the Photo-Alignment Material SD-1/SDA-2 with Spectroscopic Ellipsometry2007Inngår i: 14th  International Display Workshops, 2007, 2007, s. 391-394Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Variable angle spectroscopic ellipsometry (VASE) is applied for investigation of the azo-dye SD-1/SDA-2 which are used for photoalignment of liquid crystals. The azo-dye was spin coated on silicon substrates. Samples as prepared as well as samples illuminated with polarized UV light were studied. The measured optical constants were modelled with an ensemble of the Lorentz oscillators. The results confirm the reorientation mechanism of the photo-induced order formation in the azo-dye films under the action of polarized light, and also show that there exist some photochemical processes.

  • 219.
    Valyukh, Iryna
    et al.
    Dalarna University, Borlänge, Sweden.
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Chigrinov, Vladimir
    Hong Kong University of Science and Technology, Hong Kong.
    Valyukh, Sergiy
    Hong Kong University of Science and Technology, Hong Kong.
    UV-induced in-plane anisotropy in layers of mixture of the azo-dyes SD-1/SDA-2 characterized by spectroscopic ellipsometry2008Inngår i: Physica Status Solidi. C, Current topics in solid state physics: Special Issue: 4th International Conference on Spectroscopic Ellipsometry (ICSE4), Weinheim, Germany: Wiley-VCH Verlagsgesellschaft, 2008, Vol. 5, nr 5, s. 1274-1277Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The optical properties of the azo-dyes SD-1/SDA-2, which are used for photoaligning of liquid crystals (LCs), are investigated with Variable Angle Spectroscopic Ellipsometry (VASE). Films of mixture of SD-1/SDA-2 are deposited by spin coating on silicon wafers. The estimated thickness is approximately 10 nm. To achieve photo-induced anisotropy, one of the samples is illuminated during 15 minutes with linearly polarized UV light followed by thermal stabilization during 1 hour at 150 °C. VASE measurements are performed in the wavelength range 200–1350 nm at several angles of incidence and at different sample orientations. Dielectric functions of azo-dye films without/with polarized UV light illumination were modelled using an ensemble of Lorentz oscillators. The results confirm the diffusion model proposed recently for explanation of the formation of the photo-induced order in azo-dye films under the action of polarized light. Refractive indices, their wavelength dispersion and thicknesses of films of SD-1/SDA-2 are reported here.

  • 220.
    Valyukh, Iryna
    et al.
    Dalarna University, Borlänge.
    Green, S.
    Uppsala University, The Ångström Laboratory.
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Niklasson, G.A.
    Uppsala University, The Ångström Laboratory.
    Wäckelgård, Ewa
    Uppsala University, The Ångström Laboratory.
    Granqvist, C.G.
    Uppsala University, The Ångström Laboratory.
    Optical Properties of Amorphous Tungsten Osice Films Deposited by Reactive DC magnetron sputtering2009Konferansepaper (Annet vitenskapelig)
  • 221.
    Valyukh, Iryna
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Green, S V
    Uppsala University, Sweden .
    Granqvist, C G
    Uppsala University, Sweden .
    Gunnarsson, K
    Uppsala University, Sweden .
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Niklasson, G A
    Uppsala University, Sweden .
    Ellipsometrically determined optical properties of nickel-containing tungsten oxide thin films: Nanostructure inferred from effective medium theory2012Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 112, nr 4, s. 044308-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Films of NixW1-x oxide with 0.05 andlt;= x andlt;= 0.53 were produced by reactive dc magnetron co-sputtering onto Si. Such films have documented electrochromism. Spectroscopic ellipsometry was used to extract accurate data on the dielectric function in the photon range 0.062 to 5.62 eV. The results for 0.62 to 5.62 eV were compared with computations from the Bruggeman effective medium theory applied to two nanostructural models: one representing a random mixture of structural entities characterized by the dielectric functions of WO3 and NiWO4 and the other describing a random mixture of WO3 and NiO. Unambiguous evidence was found in favor of the former model, and hence the films are composed of nanosized tungsten oxide and nickel tungstate. This agrees excellently with an earlier investigation of ours on NixW1-x oxide films, where nanostructure was inferred from Raman spectroscopy, x-ray photoelectron spectroscopy, and x-ray diffraction.

  • 222.
    Valyukh, Iryna
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik.
    Green, S V
    Uppsala University.
    Granqvist, C G
    Uppsala University.
    Niklasson, G A
    Uppsala University.
    Valyukh, Sergiy
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik.
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Optical properties of thin films of mixed Ni-W oxide made by reactive DC magnetron sputtering2011Inngår i: THIN SOLID FILMS, ISSN 0040-6090, Vol. 519, nr 9, s. 2914-2918Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thin films of NixW1-x oxides with x = 0.05, 0.19, 0.43 and 0.90 were studied. Films with thicknesses in the range 125-250 nm were deposited on silicon wafers at room temperature by reactive DC magnetron co-sputtering from targets of Ni and W. The films were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), and spectroscopic ellipsometry (SE). XRD spectra and SEM micrographs showed that all films were amorphous and possessed a columnar structure. The ellipsometric angles psi and Delta of as-deposited films were measured by a rotating analyzer ellipsometer in the UV-visible-near infrared range (0.63-6.18 eV) and by an infrared Fourier transform rotating compensator ellipsometer in the 500-5200 cm(-1) wavenumber range. SE measurements were performed at angles of incidence of from 50 degrees to 70 degrees. Parametric models were used to extract thicknesses of the thin films and overlayers of NixW1-x oxide at different compositions, band gaps and optical constants. Features in the optical spectra of the NixW1-x oxides were compared with previous data on tungsten oxide, nickel oxide and nickel tungstate.

  • 223.
    Valyukh, Iryna
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Jiao, Z.
    Nanyang Technological University, Singapore.
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Sun, X. W.
    Nanyang Technological University, Singapore.
    Optical Properties of Hydrated Tungsten Trioxide 3WO3ˑH2O 2014Inngår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 571, s. 644-647Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Spectroscopic ellipsometry was used to determine the optical properties of plate-like hydrated tungsten trioxide (3WO3·H2O) films in the energy range 300–4000 cm− 1. Films with different thicknesses were deposited on glass substrates pre-coated with fluorine-doped tin oxide via an efficient and simple hydrothermal method. Parametric models were used to extract thicknesses and optical constants of the thin films. The WO3 was found to be more hydrated for thicker films. Moreover, the nano-plates are larger in thicker films, which leads to a decrease of the transmission due to an increase of the scattering. Features in the obtained dielectric functions of the 3WO3·H2O thin films were compared with the earlier published optical spectra of WO3 and its hydrates ½WO3·H2O and WO3·H2O.

  • 224.
    Valyukh, Iryna
    et al.
    Dalarna University, Borlänge, Sweden .
    Valyukh, Sergiy
    Swedish LCD Center AB, Borlänge, Sweden .
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Chigrinov, Vladimir
    Hong Kong University of Science and Technology, Kowloon, Hong Kong .
    Characteristic functions for uniformly twisted birefringent media2007Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 102, nr 6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present two functions for characterization of birefringent media with application to twisted nematic liquid crystal (LC) cells in the field off state. The first function is for reflective LC cells and the second is for transmissive LC cells. Based on the Stockes formalism, it is shown that these functions describe the ability of a layer of the twisted birefringent medium to change polarization of the output light and are invariant to the layer orientation. The characteristic functions are found in simple procedures and can be used for simultaneous determination of retardation, its wavelength dispersion, and twist angle, as well as for solving optimization problems. © 2007 American Institute of Physics.

  • 225.
    Valyukh, Sergiy
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Adaptive liquid crystal lenses for display applications2012Inngår i: SID-ME Spring Meeting 2012, 2012Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    This work is devoted to study of adaptive liquid (LC) lens arrays utilized as a switcher between 2D and 3D autostereoscopic displays. In addition, the adaptive lens array can set and control viewing zones of an autostereoscopic display. The needed spatial distribution of LC director caused the lens effect can be achieved due to a non-uniform electric field or inhomogeneous alignment. In order to obtain a non-uniform electric field, it is necessary a pattered structure of electrodes or a specific design, e.g. non-uniform thickness of a dielectric layer sandwiched between the electrodes and LC. The inhomogeneous alignment is achieved due to a non-uniform distribution of the pre-tilt angle or anchoring energy. Analysis of adaptive LC lenses based on a non-uniform electric field and inhomogeneous alignment is done.

  • 226.
    Valyukh, Sergiy
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Diffractive optical elements based on liquid crystals2012Inngår i: 4th Workshop on Liquid Crystals for Photonics, 2012Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Liquid crystal-based planar optical elements destined for control of direction of light propagation are investigated. There are diffractive active lenses, dynamic diffraction gratings, tuneable prisms, etc. Among the attractive features of such optical elements are non-mechanical tunability, low driving voltage, relatively low cost, and small sizes. In fact, they can be much smaller and have less weight that conventional glass and plastic analogues [1-3]. The key role in achieving the needed optical properties plays a liquid crystal due to its unique features - electric and optical anisotropies coupled with high fluidity. A certain distribution of an external electric field or inhomogeneous boundary conditions leads to a spatial distribution of the liquid crystal molecules (director) that, in turn, forms an optically inhomogeneous medium. This medium affects the light propagation in the required way.

    In the present work, we study formation of a desired liquid crystal director distribution by the use of inhomogeneous alignment, i.e. non-uniform distributions of anchor energy or the pre-tilt angle. Such an approach enables one to control the optical element by a uniform electric field when only two continues electrodes are needed. This means that there are no constructive regularities, e.g. a periodic arrangement of the electrodes or thickness, which often have undesired impact on diffractive characteristics of the optical elements. Moreover, periodicity and diffraction efficiency of such kind of the optical elements can be higher than the optical elements controlled by an inhomogeneous electric field [1-3].

    As examples of practical applications, a reflective lens utilising cholesteric liquid crystal and a projection optical system for hypothetic near eye displays that can be built into a contact lens or glasses will be reported.

    References

    [1] S. Valyukh, I. Valyukh, V. Chigrinov, H. S. Kwok, and H. Arwin, “Liquid crystal light deflecting devices based on nonuniform anchoring,” Appl. Phys. Lett. 97, 231120 (2010).

    [2] S. Valyukh, V. Chigrinov,  “Optimization of Liquid-Crystal Phase Arrays,” SID Symposium Digest 42, pp. 1691-1694 (2011).

    [3] S. Valyukh, V. Chigrinov, H. S. Kwok, and H. Arwin, “On liquid crystal diffractive optical elements utilizing inhomogeneous alignment, ” Optics Express, 20, pp. 15209-15221 (2012).

  • 227.
    Valyukh, Sergiy
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik.
    Liquid-Crystal Based Light Steering Optical Elements2010Inngår i: Workshop on Liquid Crystals for Photonics 2010, Hong Kong, 2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Effective and compact active optical elements such as lenses with variable focus distance and beam steering devices are highly required for many photonic applications. Liquid crystals (LCs) are especially attractive due to their property to be controlled with an external electrical field. The main idea is based on the fact that an external non-uniform electrical field and/or particular alignment features enable one to achieve a desired spatial distribution of the LC molecules (director). Non-uniformity of the LC medium leads to internal refraction that, in turn, affects the trajectory of the light passed. In other words, the light trajectory is steered by the electrical field.

    Functional abilities of LC optical elements are restricted by refractive index changes, poor control over index profiles, and thickness of the LC layer. In order to increase the steering angle and the lens aperture, the LC light steering elements are built on principles of diffractive optics, i.e. Fresnel’s lenses and switchable diffraction gratings are used. The present work concentrates on investigation of the potential of diffraction gratings and Fresnel’s lenses based on liquid crystals. Specificity of formation of a desired spatial distribution of the LC director, as well as the correspondent restrictions, is studied. The aim is to clarify the relationship between the width of the fly-back zone, the LC thickness, the principal physical constants of the LC material, and factors that can cause a sharp profile in the LC director distribution, i.e. external field and non-uniform alignment [1,2].

    References

    1. V. G. Chigrinov, Liquid crystal devices: physics and applications (Artech House, Norwood, MA, 1999)

    2. I. W. Stewart, The static and dynamic continuum theory of liquid crystals (Taylor & Francis, 2004).

  • 228.
    Valyukh, Sergiy
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Photonic nanocomposites and their applications2013Inngår i: Advanced Materials World Congress (AMWC 2013)Turkey / [ed] A. Tiwari, M. M. Demir, 2013Konferansepaper (Fagfellevurdert)
  • 229.
    Valyukh, Sergiy
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Spectrally selective flat reflective lenses for photovoltaic applications2013Inngår i: Progress In Electromagnetics Research Symposium, 2013Konferansepaper (Fagfellevurdert)
  • 230.
    Valyukh, Sergiy
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik.
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik.
    Birch, Jens
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Magnusson, Roger
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik.
    Järrendahl, Kenneth
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik.
    Bragg reflection of light from chiral laterally graded media2011Inngår i: 6th Workshop on Ellipsometry, 2011Konferansepaper (Fagfellevurdert)
  • 231.
    Valyukh, Sergiy
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Järrendahl, Kenneth
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Light Scattering and Colour Generation in exoskeletons of Jewelled Beetle2012Inngår i: Photonics Global Conference, 2012Konferansepaper (Annet vitenskapelig)
  • 232.
    Valyukh, Sergiy
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik.
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik.
    Järrendahl, Kenneth
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik.
    On Light Interaction with Exoskeleton of Scarab Beetles2013Inngår i: ICSE-VI 2013 - 6th International Conference on Spectroscopic Ellipsometry. May 26-31, 2013. Kyoto, Kyoto, Japan, 2013Konferansepaper (Fagfellevurdert)
  • 233.
    Valyukh, Sergiy
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska fakulteten.
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska fakulteten.
    Järrendahl, Kenneth
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska fakulteten.
    Simulation of light scattering from exoskeletons of scarab beetles2016Inngår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 24, nr 6, s. 5794-5808Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An approach for simulation of light scattering from beetles exhibiting structural colors originating from periodic helicoidal structures is presented. Slight irregularities of the periodic structure in the exoskeleton of the beetles are considered as a major cause of light scattering. Two sources of scattering are taken into account: surface roughness and volume non-uniformity. The Kirchhoff approximation is applied to simulate the effect of surface roughness. To describe volume non-uniformity, the whole structure is modeled as a set of domains distributed in space in different orientations. Each domain is modeled as an ideal uniformly twisted uniaxial medium and differs from each other by the pitch. Distributions of the domain parameters are assumed to be Gaussian. The analysis is performed using the Mueller matrix formalism which, in addition to spectral and spatial characteristics, also provides polarization properties of the scattered light. (C) 2016 Optical Society of America

  • 234.
    Valyukh, Sergiy
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Åkerlind, Christina
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Järrendahl, Kenneth
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Simulation of light scattering from biological helicoidal structures2012Inngår i: 7th Workshop Ellipsometry, 2012, s. 90-Konferansepaper (Annet vitenskapelig)
  • 235.
    Valyukh, Sergiy
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Chigrinov, V.
    Hong Kong University of Science and Technology, Peoples R China .
    Kwok, H. S.
    Hong Kong University of Science and Technology, Peoples R China .
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    On liquid crystal diffractive optical elements utilizing inhomogeneous alignment2012Inngår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 20, nr 14, s. 15209-15221Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Formation of a desired liquid crystal (LC) director distribution by the use of inhomogeneous anchoring and pre-tilt angle for electrically controlled diffractive optical elements (DOE) is studied. Such LC DOE can have high periodicity and diffraction efficiency. At the same time they are free of constructive regularities, e. g. a periodic arrangement of the electrodes or thickness deviations, which have undesired impact on diffractive characteristics of LC DOE of other types. We focus on evaluation of potential functional abilities of LC DOE with inhomogeneous alignment. The reasons causing restriction of the LC DOE diffraction efficiency and periodicity are considered. Approaches for improvement of characteristics of the LC DOE are discussed.

  • 236.
    Valyukh, Sergiy
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Chigrinov, Vladimir
    Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
    P-136: Optimization of Liquid-Crystal Phased Arrays2011Inngår i: SID Symposium Digest of Technical Papers, ISSN 0097-966X, Vol. 42, nr 1, s. 1619-1622Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, liquid-crystal phased arrays are studied. We consider two types of such devices where the needed spatial distribution of liquid crystal director is formed by 1) an inhomogeneous electric field, and 2) an inhomogeneous alignment. Physical restrictions and ways for optimizations of these devices are investigated.

  • 237.
    Valyukh, Sergiy
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Chigrinov, Vladimir
    Hong Kong University of Science and Technology, Hong Kong.
    Tytarenko, Pavlo
    Kwok, Hoi Sing
    Low voltage liquid crystal light steering devices based on non-uniform boundary conditions2010Inngår i: 3rd International Workshop on Liquid Crystals for Photonics, 2010, 2010Konferansepaper (Annet vitenskapelig)
  • 238.
    Valyukh, Sergiy
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Slobodyanyuk, O.
    Taras Shevchenko National University of Kyiv, Ukraine.
    Chigrinov, V.
    Hong Kong University of Science and Technology.
    Tuneable Objective System for Near-to-Eye Displays2013Inngår i: Optik & Fotonik i Sverige 2013 (Optics & Photonics in Sweden), Uppsala, 2013Konferansepaper (Annet vitenskapelig)
  • 239.
    Valyukh, Sergiy
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Slobodyanyuk, Oleksandr
    Objective LC lens array for a Near-to-Eye Display2013Inngår i: SID Digest, 2013Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    An objective liquid crystal microlens array enables one to see a microdisplay located at the immediate vicinity of the eye, e.g. such that built into a contact lens or glasses. However, implementation of this microlens array is associated with two problems – correct conjugation of the image provided by the microdisplay with the retina of the eye and the light leakage to a microlens from the adjacent pixels that causes the image blur. In this work, we consider these problems and their possible solutions.

  • 240.
    Valyukh, Sergiy
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Smet, Jelle De
    Ghent University-ELIS, imec-CMST, Belgium.
    Smet, Herbert De
    Ghent University-ELIS, imec-CMST, Belgium.
    Slobodyanyuk, Oleksandr
    Faculty of Physics, Taras Shevchenko National University of Kyiv.
    A Liquid Crystal Lens Array-Based Projection System for NearEye Displays2012Inngår i: The 19th International Display Workshops in conjunction with Asia Display, 2012, Kyoto, 2012, 2012, s. 1305-1308Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    A projection optical system for hypothetic near eyedisplays that can be built into a contact lens or glasses isconsidered. The system parameters are evaluated.Aspects of practical usage of the displays and possibleembodiments of the optical system are discussed.

  • 241.
    Valyukh, Sergiy
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska fakulteten. Hong Kong University of Science and Technology, Peoples R China.
    Sorokin, Sergei
    Hong Kong University of Science and Technology, Peoples R China.
    Chigrinov, Vladimir G.
    Hong Kong University of Science and Technology, Peoples R China.
    Inline Quality Control of Liquid Crystal Cells2015Inngår i: IEEE/OSA Journal of Display Technology, ISSN 1551-319X, E-ISSN 1558-9323, Vol. 11, nr 12, s. 1042-1047Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Inline quality control of liquid crystal (LC) cells is usually associated with a real-time noncontact characterization of moved LC cells. Such a characterization enables inspection of the products quality and helps to find in time defects. In the paper, we analyze an approach for fast evaluation of LC cell gap uniformity. The approach is based on detecting interference patterns formed by the quasi-monochromatic light reflected from a tested LC cell. To speed up the data treatment, a simple analytic expression describing the intensity of light interacting with the multilayered structure of an LC cell is derived. The results of the simplified model are compared with rigorous simulations. Two experimental setups are discussed. A CCD camera is used for detecting the interference patterns.

  • 242.
    Valyukh, Sergiy
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Tytarenko, Pavlo
    Liquid Crystals, Institute of Semicondactor Physics of NASU.
    Liquid-crystal-based diffractive optical elements2012Inngår i: 8th EOS Topical Meeting on Diffractive Optics 2012, Delf, 2012Konferansepaper (Annet vitenskapelig)
  • 243.
    Valyukh, Sergiy
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska fakulteten.
    Valyukh, Iryna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska fakulteten.
    Chigrinov, V
    Hong Kong University of Science and Technology.
    Kwok, H S
    Hong Kong University of Science and Technology.
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Liquid crystal light deflecting devices based on nonuniform anchoring2010Inngår i: APPLIED PHYSICS LETTERS, ISSN 0003-6951, Vol. 97, nr 23, s. 231120-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Tunable liquid crystal light deflecting devices based on nonuniform anchoring energy are proposed. These devices have uniform thicknesses of the layers they are composed of, and beam deviation is controlled with a uniform electrical field. Potential applicability of such an approach in beam deflectors and active lenses is investigated. It is shown that the approach is a competitive alternative to liquid crystal light deflecting devices, in which the needed spatial distribution of liquid crystal molecules is achieved either due to nonuniform thickness or due to generation of nonuniform electrical field.

  • 244.
    Valyukh, Sergiy
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Valyukh, Iryna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Chigrinov, Vladimir
    Hong Kong University of Science and Technology, CWB, Kowloon, Hong Kong.
    Liquid-crystal based light steering optical elements2011Inngår i: Photonics Letters of Poland, ISSN 2080-2242, E-ISSN 2080-2242, Vol. 3, nr 2, s. 88-90Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Potential abilities of active optical elements based onliquid crystals are investigated. We consider liquid crystal cells in whicha desired distribution of the liquid crystal director is achieved by a non-uniform electric field and by inhomogeneous boundary conditions. Theoptical elements built on principles of diffractive optics are discussed.

  • 245.
    Valyukh, Vladimir
    et al.
    Katedralskolan, Linköping, Sweden.
    Kozachenko, Andriy
    LCOptic, Linköping, Sweden.
    Valyukh, Sergiy
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Mobile multifunctional system for characterization of LC cells and LC materials2011Inngår i: SID Symposium Digest of Technical Papers, ISSN 0097-966X, Vol. 42, nr 1, s. 1241-1244Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A compact measuring system for determination of electoro-optical time resolved characteristics of LC cells, as well as optical retardation and twist angle, has been developed. Moreover, the system enables one to measure anchoring energy, elastic and dielectric constants of LC materials. Software of the system contains functions for simulation and optimization of LC devices.

  • 246.
    Wang, Guoliang
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Arwin, Hans
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik.
    Modification of vapor sensitivity in ellipsometric gas sensing by copper deposition in porous silicon2002Inngår i: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 85, nr 1-2, s. 95-103Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The sensitivities of porous silicon layers modified by copper deposition to low vapor concentrations of methanol, ethanol and 2-propanol are studied with spectroscopic ellipsometry. The porous silicon layers are prepared with electrochemical etching in hydrofluoric acid, and copper deposition is done in aqueous CuSO4. The ellipsometric vapor sensitivities, in terms of the ellipsometric spectral shifts due to gas exposures, of these samples and their oxides are studied and compared. It is shown that ellipsometric vapor sensitivities of porous silicon layers to alcohols are improved by copper deposition. It is also found that the oxidation of copper deposited in porous silicon layers shows improved selectivity to methanol. © 2002 Elsevier Science B.V. All rights reserved.

  • 247.
    Wang, Guoliang
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Arwin, Hans
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik.
    Return-path ellipsometry in gas sensing2003Inngår i: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 15, s. 216-220Artikkel i tidsskrift (Fagfellevurdert)
  • 248.
    Wang, Guoliang
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Arwin, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    Jansson, Roger
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik. Linköpings universitet, Tekniska högskolan.
    An optical gas sensor based on ellipsometric readout2003Inngår i: IEEE Sensors Journal, ISSN 1530-437X, E-ISSN 1558-1748, Vol. 3, nr 6, s. 739-743Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A gas sensor system based on ellipsometric readout is presented. It includes a gas chamber and a compact null ellipsometer operated in off-null mode. Small, low-cost optical components are used to demonstrate that this advanced methodology can be implemented in simplified instrumentation. The off-null ellipsometric sensing principle and transducer mechanisms of the sensing layers, as well as the instrumentation, are described. The application of the sensor system is exampled with experimental results on low-concentration alcoholic gases (methanol, ethanol, and 2-propanol) using porous silicon as a sensing layer. Optimization of the optics of the sensor system, improvement of sensitivity or alteration of selectivity by modification of sensing layers, and multisensing by using several ellipsometric units in parallel are discussed.

  • 249.
    Wang, Guoliang
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Arwin, Hans
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik.
    Jansson, Roger
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Optimization of azimuth angle settings in polarizer-compensator-sample-analyzer off-null ellipsometry2003Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 42, nr 1, s. 38-44Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The dependence of the azimuth angle settings on the change in off-null intensity of a polarizer-.compensator-sample-analyzer ellipsometer owing to changes in sample properties is studied. First, a closed-form expression for the relationship between azimuth angles that fulfill the null condition is presented. An approximation for the off-null light intensity near null that is valid for small changes of the p- and s-reflection coefficients of an isotropic sample is then derived. This approximation shows that the intensity change near the null can be described by changes in the ellipsometric parameters tan q, and Delta only. Expressions for finding the azimuth angle that gives the maximum possible intensity change for a given change in the sample parameters are also derived. The importance of optimization of azimuth angle settings for different samples is investigated and found to depend on tan psi. Numerical and experimental results chosen from the investigation of gas sensors based on porous silicon are included to verify the approximations as well as the optimization. (C) 2003 Optical Society of America.

  • 250.
    Wang, Guoliang
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Arwin, Hans
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik.
    Jansson, Roger
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Optimization of off-null ellipsometry in sensor applications2004Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The optimization of azimuth angle settings of a polarizer-compensator-sample-analyzer off-null ellipsometric sensor system to obtain maximum intensity changes with respect to changes in the properties of a sensing layer, with and without considering changes in a reflectance, is studied. Optimal conditions in the two cases are derived analytically under the assumption that linear relationships exist among the changes in the parameters of the sensing layer. The validity of these optimal conditions is verified by numerical examples. The advantage of using ellipsometry compared with reflectometry to readout sensing information for some sensing samples is also discussed. © 2004 Optical Society of America.

23456 201 - 250 of 273
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