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  • 1.
    Hsiao, Ching-Lien
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Sandström, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Persson, Per O. Å.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Valyukh, Sergiy
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Curved-Lattice Epitaxial Growth of InxAl1-xN Nanospirals with Tailored Chirality2015In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 15, no 1, p. 294-300Article in journal (Refereed)
    Abstract [en]

    Chirality, tailored by external morphology and internal composition, has been realized by controlled curved-lattice epitaxial growth (CLEG) of uniform coatings of single-crystalline InxAl1-xN nanospirals. The nanospirals are formed by sequentially stacking segments of curved nanorods on top of each other, where each segment is incrementally rotated around the spiral axis. By controlling the growth rate, segment length, rotation direction, and incremental rotation angle, spirals are tailored to predetermined handedness, pitch, and height.  The curved morphology of the segments is a result of a lateral compositional gradient across the segments while maintaining a preferred crystallographic growth direction, implying a lateral gradient in optical properties as well. Left- and right-handed nanospirals, tailored with 5 periods of 200 nm pitch, as confirmed by scanning electron microscopy, exhibit uniform spiral diameters of ~80 nm (local segment diameters of ~60 nm) with tapered hexagonal tips.  High resolution electron microscopy, in combination with nanoprobe energy dispersive X-ray spectroscopy and valence electron energy loss spectroscopy, show that individual nanospirals consist of an In-rich core with ~15 nm-diameter hexagonal cross-section, comprised of curved basal planes. The core is surrounded by an Al-rich shell with a thickness asymmetry spiraling along the core. The ensemble nanospirals, across the 1 cm2 wafers, show high in-plane ordering with respect to shape, crystalline orientation, and direction of compositional gradient. Mueller matrix spectroscopic ellipsometry shows that the tailored chirality is manifested in the polarization state of light reflected off the CLEG nanospiral-coated wafers. In that, the polarization state is shown to be dependent on the handedness of the nanospirals and the wavelength of the incident light in the ultraviolet-visible region.

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  • 2.
    Hsiao, Ching-Lien
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Sandström, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Valyukh, Sergiy
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Persson, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Curved-lattice epitaxial growth of chiral AlInN twisted nanorods for optical applications2012Manuscript (preprint) (Other academic)
    Abstract [en]

    Despite of using chiral metamaterials to manipulate light polarization states has been demonstrated their great potential for applications such as invisible cloaks, broadband or wavelength-tunable circular polarizers, microreflectors, etc. in the past decade [1-6], operating wavelength in ultraviolet-visible range is still a challenge issue. Since these chiral structures often consist of metallic materials, their operation is designed for the infrared and microwave regions [2-4]. Here, we show how a controlled curved-lattice epitaxial growth (CLEG) of wide-bandgap AlInN semiconductor curved nanocrystals [7] can be exploited as a novel route for tailoring chiral nanostructures in the form of twisted nanorods (TNRs). The fabricated TNRs are shown to reflect light with a high degree of polarization as well as a high degree of circular polarization (that is, nearly circularly polarized light) in the ultravioletvisible region. The obtained polarization is shown to be dependent on the handedness of the TNRs.

  • 3.
    Kalustova, Darla
    et al.
    NAS Ukraine, Ukraine.
    Kornaga, Vasyl
    NAS Ukraine, Ukraine.
    Rybalochka, Andrii
    NAS Ukraine, Ukraine.
    Yu, Ying-Jie
    Shanghai Univ, Peoples R China.
    Valyukh, Sergiy
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Color temperature tunable RGBW clusters with 3 control channels2020In: Photonics Letters of Poland, ISSN 2080-2242, E-ISSN 2080-2242, Vol. 12, no 1, p. 10-12Article in journal (Refereed)
    Abstract [en]

    The work is devoted to the development of a smart lighting system that is able to change correlated colour temperature and consists of tunable 4-components RGBW clusters controlled via three channels. It is shown that fixing a ratio between the intensities of white and red LEDs at a level of 100:9 enables obtaining high values of colour rendering in a wide range of correlated colour temperatures. The control of 3 from 4 channels simplifies the system. The influence of the red LED on CRI and luminous efficiency is analysed.

  • 4.
    Pranovich, Alina
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Trujillo Vazquez, Abigail
    University of the West of England, United Kingdom.
    Nyström, Daniel
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Valyukh, Sergiy
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Frisvad, Jeppe Revall
    Technical University of Denmark, Denmark.
    Klein, Susanne
    University of the West of England, United Kingdom.
    Parraman, Carinna
    University of the West of England, United Kingdom.
    Angular dependent reflectance spectroscopy of RGBW pigments2022Conference paper (Other academic)
    Abstract [en]

    Traditional printing relies primarily on subtractive color mixing techniques. In this case, optical color mixing is achieved by one of the established halftoning methods that use Cyan, Magenta, Yellow and Black (CMYK) primaries on a reflective white substrate. The reason behind the subtractive color mixing in printing is the high absorbance of available pigments used in inks. A new type of mica-based pigments that exhibit high reflectivity at Red, Green, Blue and White (RGBW) spectral bands was recently introduced by Merck (SpectravalTM). Printing with RGBW primaries on black background allows additive color mixing in prints. While offering excellent color depth, the reflected spectra of such pigments vary with the angles of incidence and observation. As a result, new approaches in modelling the appearance of prints as well as strategies for color separation and halftoning are needed. The prior optical characterization of the reflective inks is an essential first step. For this purpose, we have used SpectravalTM pigments to prepare acrylic based inks, which we applied on glass slides by screen printing. In this work, we measured the relative spectral bidirectional reflection distribution of Red, Green, Blue and White reflective inks. The measurements were conducted on an experimental set up consisting of a goniometer, spectrometer, and a xenon light source. Based on the measurements, we simulate the reflectance spectra under diffuse illumination and demonstrate ratios of red, green, and blue spectral components for different observation angles of individual inks and their combinations.

  • 5.
    Pranovich, Alina
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Valyukh, Sergiy
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Gooran, Sasan
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Frisvad, Jeppe Revall
    Technical University of Denmark, Denmark.
    Nyström, Daniel
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Dot Off Dot Screen Printing with RGBW Reflective Inks2023In: Journal of Imaging Science and Technology, ISSN 1062-3701, E-ISSN 1943-3522, Vol. 67, no 3, article id 030404Article in journal (Refereed)
    Abstract [en]

    Recent advances in pigment production resulted in the possibility to print with RGBW primaries instead of CMYK and performing additive color mixing in printing. The RGBW pigments studied in this work have the properties of structural colors, as the primary colors are a result of interference in a thin film coating of mica pigments. In this work, we investigate the angle-dependent gamut of RGBW primaries. We have elucidated optimal angles of illumination and observation for each primary ink and found the optimal angle of observation under diffuse illumination. We investigated dot off dot halftoned screen printing with RGBW inks on black paper and in terms of angle-dependent dot gain. Based on our observations, optimal viewing condition for the given RGBW inks is in a direction of around 30◦ to the surface normal. Here, the appearance of the resulting halftoned prints can be estimated well by Neugebauer formula (weighted averaging of the individual reflected spectra). Despite the negative physical dot gain during the dot off dot printing, we observe angularly dependent positive optical dot gain for halftoned prints. Application of interference RGBW pigments in 2.5D and 3D printing is not fully explored due to the technological limitations. In this work, we provide colorimetric data for efficient application of the angle-dependent properties of such pigments in practical applications.

  • 6.
    Tiwari, Ashutosh
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Valyukh, SergiyLinköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Advanced Energy Materials2014Collection (editor) (Other academic)
    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.

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  • 7.
    Valyukh, Iryna
    et al.
    Dalarna University, Borlänge, Sweden.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    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 Ellipsometry2007In: 14th  International Display Workshops, 2007, 2007, p. 391-394Conference paper (Other academic)
    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.

  • 8.
    Valyukh, Iryna
    et al.
    Dalarna University, Borlänge, Sweden.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    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 ellipsometry2008In: 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, no 5, p. 1274-1277Conference paper (Refereed)
    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.

  • 9.
    Valyukh, Iryna
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Green, S V
    Uppsala University.
    Granqvist, C G
    Uppsala University.
    Niklasson, G A
    Uppsala University.
    Valyukh, Sergiy
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Optical properties of thin films of mixed Ni-W oxide made by reactive DC magnetron sputtering2011In: THIN SOLID FILMS, ISSN 0040-6090, Vol. 519, no 9, p. 2914-2918Article in journal (Refereed)
    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.

  • 10.
    Valyukh, Iryna
    et al.
    Dalarna University, Borlänge, Sweden .
    Valyukh, Sergiy
    Swedish LCD Center AB, Borlänge, Sweden .
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Chigrinov, Vladimir
    Hong Kong University of Science and Technology, Kowloon, Hong Kong .
    Characteristic functions for uniformly twisted birefringent media2007In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 102, no 6Article in journal (Refereed)
    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.

  • 11.
    Valyukh, Sergiy
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Adaptive liquid crystal lenses for display applications2012In: SID-ME Spring Meeting 2012, 2012Conference paper (Other academic)
    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.

  • 12.
    Valyukh, Sergiy
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Diffractive optical elements based on liquid crystals2012In: 4th Workshop on Liquid Crystals for Photonics, 2012Conference paper (Other academic)
    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).

  • 13.
    Valyukh, Sergiy
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics. Linköping University, The Institute of Technology.
    Photonic nanocomposites and their applications2013In: Advanced Materials World Congress (AMWC 2013)Turkey / [ed] A. Tiwari, M. M. Demir, 2013Conference paper (Refereed)
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    Nanocomp
  • 14.
    Valyukh, Sergiy
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Spectrally selective flat reflective lenses for photovoltaic applications2013In: Progress In Electromagnetics Research Symposium, 2013Conference paper (Refereed)
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  • 15.
    Valyukh, Sergiy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Light Scattering and Colour Generation in exoskeletons of Jewelled Beetle2012In: Photonics Global Conference, 2012Conference paper (Other academic)
  • 16.
    Valyukh, Sergiy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    On Light Interaction with Exoskeleton of Scarab Beetles2013In: ICSE-VI 2013 - 6th International Conference on Spectroscopic Ellipsometry. May 26-31, 2013. Kyoto, Kyoto, Japan, 2013Conference paper (Refereed)
  • 17.
    Valyukh, Sergiy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics. Linköping University, Faculty of Science & Engineering.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics. Linköping University, Faculty of Science & Engineering.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics. Linköping University, Faculty of Science & Engineering.
    Simulation of light scattering from exoskeletons of scarab beetles2016In: Optics Express, E-ISSN 1094-4087, Vol. 24, no 6, p. 5794-5808Article in journal (Refereed)
    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

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  • 18.
    Valyukh, Sergiy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Åkerlind, Christina
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Simulation of light scattering from biological helicoidal structures2012In: 7th Workshop Ellipsometry, 2012, p. 90-Conference paper (Other academic)
  • 19.
    Valyukh, Sergiy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    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
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    On liquid crystal diffractive optical elements utilizing inhomogeneous alignment2012In: Optics Express, E-ISSN 1094-4087, Vol. 20, no 14, p. 15209-15221Article in journal (Refereed)
    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.

  • 20.
    Valyukh, Sergiy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Chigrinov, Vladimir
    Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
    P-136: Optimization of Liquid-Crystal Phased Arrays2011In: SID Symposium Digest of Technical Papers, ISSN 0097-966X, Vol. 42, no 1, p. 1619-1622Article in journal (Refereed)
    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.

  • 21.
    Valyukh, Sergiy
    et al.
    LCoptic, Borlänge, Sweden.
    Chigrinov, Vladimir
    Hong Kong University of Science and Technology.
    Kwok, Hoi Sing
    Hong Kong University of Science and Technology.
    A Liquid Crystal Lens with Non-uniform Anchoring Energy2008In: SID Digest, 2008, 2008, p. 659-662Conference paper (Refereed)
    Abstract [en]

    The study of a tunable liquid crystal lens having a uniform cell gap, uniform applied voltage and non-uniform anchoring energy was done. Optimal parameters of such a lens were found and discussed. We demonstrated that producing a desired director gradient profile with non-uniform spatial distribution of the anchoring energy is a good alternative for other known methods applied for liquid crystal lenses.

  • 22.
    Valyukh, Sergiy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    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 conditions2010In: 3rd International Workshop on Liquid Crystals for Photonics, 2010, 2010Conference paper (Other academic)
  • 23.
    Valyukh, Sergiy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    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 Displays2013In: Optik & Fotonik i Sverige 2013 (Optics & Photonics in Sweden), Uppsala, 2013Conference paper (Other academic)
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  • 24.
    Valyukh, Sergiy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Slobodyanyuk, Oleksandr
    Taras Shevchenko National University of Kyiv, Ukraine.
    Assessment of minimum permissible geometrical parameters of a near-to-eye display2015In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 54, no 21, p. 6526-6533Article in journal (Refereed)
    Abstract [en]

    Light weight and small dimensions are some of the most important characteristics of near-to-eye displays (NEDs). These displays consist of two basic parts: a microdisplay for generating an image and supplementary optics in order to see the image. Nowadays, the pixel size of microdisplays may be less than 4 mu m, which makes the supplementary optics the major factor in defining restrictions on a NED dimensions or at least on the distance between the microdisplay and the eye. The goal of the present work is to find answers to the following two questions: how small this distance can be in principle and what is the microdisplay maximum resolution that stays effective to see through the supplementary optics placed in immediate vicinity of the eye. To explore the first question, we consider an aberration-free magnifier, which is the initial stage in elaboration of a real optical system. In this case, the paraxial approximation and the transfer matrix method are ideal tools for simulation of light propagation from the microdisplay through the magnifier and the human eyes optical system to the retina. The human eye is considered according to the Gullstrand model. Parameters of the magnifier, its location with respect to the eye and the microdisplay, and the depth of field, which can be interpreted as the tolerance of the microdisplay position, are determined and discussed. The second question related to the microdisplay maximum resolution is investigated by using the principles of wave optics. (C) 2015 Optical Society of America

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  • 25.
    Valyukh, Sergiy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Slobodyanyuk, Oleksandr
    Objective LC lens array for a Near-to-Eye Display2013In: SID Digest, 2013Conference paper (Other academic)
    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.

  • 26.
    Valyukh, Sergiy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    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 Displays2012In: The 19th International Display Workshops in conjunction with Asia Display, 2012, Kyoto, 2012, 2012, p. 1305-1308Conference paper (Other academic)
    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.

  • 27.
    Valyukh, Sergiy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering. 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 Cells2015In: IEEE/OSA Journal of Display Technology, ISSN 1551-319X, E-ISSN 1558-9323, Vol. 11, no 12, p. 1042-1047Article in journal (Refereed)
    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.

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  • 28.
    Valyukh, Sergiy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Tytarenko, Pavlo
    Liquid Crystals, Institute of Semicondactor Physics of NASU.
    Liquid-crystal-based diffractive optical elements2012In: 8th EOS Topical Meeting on Diffractive Optics 2012, Delf, 2012Conference paper (Other academic)
  • 29.
    Valyukh, Sergiy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Valyukh, Iryna
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Chigrinov, V
    Hong Kong University of Science and Technology.
    Kwok, H S
    Hong Kong University of Science and Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Liquid crystal light deflecting devices based on nonuniform anchoring2010In: APPLIED PHYSICS LETTERS, ISSN 0003-6951, Vol. 97, no 23, p. 231120-Article in journal (Refereed)
    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.

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  • 30.
    Valyukh, Sergiy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Valyukh, Iryna
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Chigrinov, Vladimir
    Hong Kong University of Science and Technology, CWB, Kowloon, Hong Kong.
    Liquid-crystal based light steering optical elements2011In: Photonics Letters of Poland, ISSN 2080-2242, E-ISSN 2080-2242, Vol. 3, no 2, p. 88-90Article in journal (Refereed)
    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.

  • 31.
    Valyukh, Sergiy
    et al.
    LCoptic, Borlänge, Sweden.
    Valyukh, Iryna
    Dalarna University, Borlänge, Sweden.
    Kozachenko, Andriy
    LCoptic, Borlänge, Sweden.
    Characterization of Liquid-Crystal Material and Cell by Means of Generalized Spectroscopic Ellipsometry2009In: SID Digest, 2009, 2009Conference paper (Other academic)
  • 32.
    Valyukh, Sergiy
    et al.
    Dalarna University, Borlänge, Sweden.
    Valyukh, Iryna
    Dalarna University, Borlänge, Sweden.
    Skarp, Kent
    Spectrophotometric determination of reflective liquid crystal cell parameters2006In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 99, no 5, p. 053102-1-053102-6Article in journal (Refereed)
    Abstract [en]

    We introduce a method for the determination of the optical retardation, its wavelength dispersion, the cell twist angle, and the orientation of the input director in a reflective liquid crystal (LC) cell. These parameters are found from the extremes of a characteristic function defined as a sum of two spectral reflectivities of the LC cell placed between a pair of linear polarizers. The reflectivities are measured for two cell orientations, one of which is arbitrary and the other one is turned through 45°. Both theoretical analysis and experimental procedures are presented. Excellent agreement between the experiment and our theory has been found. The proposed method can be applied to the measurement of reflective LC cells with small and large cell gaps, as well as cells with small and large twist angles.

  • 33.
    Valyukh, Sergiy
    et al.
    Swedish LCD Center, Borlänge, Sweden.
    Valyukh, Iryna
    Swedish LCD Center, Borlänge, Sweden.
    Xu, Peizhi
    Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong .
    Chigrinov, Vladimir
    Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong .
    Study on Birefringent Color Generation for a Reflective Ferroelectric Liquid Crystal Display2006In: Japanese Journal of Applied Physics, ISSN 0021-4922, E-ISSN 1347-4065, Vol. 45, p. 7819-7826Article in journal (Refereed)
    Abstract [en]

    We study the possibility of a layer of a surface stabilized ferroelectric liquid crystal coupled with several retardation plates for birefringent color generation. Double and single polarizer reflective bistable dichromatic ferroelectric liquid crystal displays are considered. We demonstrate that one or two retardation plates are sufficient for a display having good color characteristics and high brightness. Optimal parameters for green/red and blue/yellow ferroelectric liquid crystal displays are found.

  • 34.
    Valyukh, Vladimir
    et al.
    Katedralskolan, Linköping, Sweden.
    Kozachenko, Andriy
    LCOptic, Linköping, Sweden.
    Valyukh, Sergiy
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Mobile multifunctional system for characterization of LC cells and LC materials2011In: SID Symposium Digest of Technical Papers, ISSN 0097-966X, Vol. 42, no 1, p. 1241-1244Article in journal (Refereed)
    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.

1 - 34 of 34
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