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  • 1.
    Mendoza, Arturo
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Cinvestav Queretaro, Mexico.
    Tejeda-Galan, Tania
    Cinvestav Queretaro, Mexico.
    Dominguez-Gomez, Amos B.
    Cinvestav Queretaro, Mexico.
    Araceli Mauricio-Sanchez, Reina
    Cinvestav Queretaro, Mexico.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Linear Birefringent Films of Cellulose Nanocrystals Produced by Dip-Coating2019In: NANOMATERIALS, ISSN 2079-4991, Vol. 9, no 1, article id 45Article in journal (Refereed)
    Abstract [en]

    Transparent films of cellulose nanocrystals (CNC) are prepared by dip-coating on glass substrates from aqueous suspensions of hydrolyzed filter paper. Dragging forces acting during films deposition promote a preferential alignment of the rod-shaped CNC. Films that are 2.8 and 6.0 mu m in thickness show retardance effects, as evidenced by placing them between a linearly polarized light source and a linear polarizer sheet in the extinction configuration. Transmission Mueller matrix spectroscopic ellipsometry measurements at normal incidence as a function of sample rotation were used to characterize polarization properties. A differential decomposition of the Mueller matrix reveals linear birefringence as the unique polarization parameter. These results show a promising way for obtaining CNC birefringent films by a simple and controllable method.

  • 2.
    Odin, Giliane P.
    et al.
    Univ Coll Cork, Ireland; Sorbonne Univ, France; Milieux Environm Transferts and Interact Hydrosyst, France.
    McNamara, Maria E.
    Univ Coll Cork, Ireland.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Experimental degradation of helicoidal photonic nanostructures in scarab beetles (Coleoptera: Scarabaeidae): implications for the identification of circularly polarizing cuticle in the fossil record2018In: Journal of the Royal Society Interface, ISSN 1742-5689, E-ISSN 1742-5662, Vol. 15, no 148, article id 20180560Article in journal (Refereed)
    Abstract [en]

    Scarab beetles (Coleoptera: Scarabaeidae) can exhibit striking colours produced by pigments and/or nanostructures. The latter include helicoidal (Bouligand) structures that can generate circularly polarized light. These have a cryptic evolutionary history in part because fossil examples are unknown. This suggests either a real biological signal, i.e. that Bouligand structures did not evolve until recently, or a taphonomic signal, i.e. that conditions during the fossilization process were not conducive to their preservation. We address this issue by experimentally degrading circularly polarizing cuticle of modern scarab beetles to test the relative roles of decay, maturation and taxonomy in controlling preservation. The results reveal that Bouligand structures have the potential to survive fossilization, but preservation is controlled by taxonomy and the diagenetic history of specimens. Further, cuticle of specific genus (Chrysina) is particularly decay-prone in alkaline conditions; this may relate to the presence of certain compounds, e. g. uric acid, in the cuticle of these taxa.

  • 3.
    Mendoza-Galvan, A.
    et al.
    Cinvestav, Mexico.
    Fernandez Del Rio, Lia
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Graded pitch profile for the helicoidal broadband reflector and left-handed circularly polarizing cuticle of the scarab beetle Chrysina chrysargyrea2018In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 6456Article in journal (Refereed)
    Abstract [en]

    The cuticle of the beetle Chrysina chrysargyrea reflects left-handed polarized light in the broad spectral range from 340 to 1000 nm. Interference oscillations in the experimental Mueller-matrix spectroscopic ellipsometry data reveal that transparent materials comprise the cuticle. A spectral analysis of the interference oscillations makes evident that the pitch profile across the cuticle is graded. The graded pitch and effective refractive indices are determined through non-linear regression analysis of the experimental Mueller matrix by using a cuticle model based on twisted biaxial dielectric slices. Non-uniformity in cuticle thickness as well as in pitch profile near the cuticle surface account for depolarizance of the Mueller matrix. Transmission electron microscopy supports the reliability of the results.

  • 4.
    Mendoza-Galvan, Arturo
    et al.
    Cinvestav IPN, Mexico.
    Munoz-Pineda, Eloy
    Cinvestav IPN, Mexico.
    Ribeiro, Sidney J. L.
    Sao Paulo State University of UNESP, Brazil.
    Santos, Moliria V.
    Sao Paulo State University of UNESP, Brazil; University of Sao Paulo, Brazil.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Mueller matrix spectroscopic ellipsometry study of chiral nanocrystalline cellulose films2018In: Journal of Optics, ISSN 2040-8978, E-ISSN 2040-8986, Vol. 20, no 2, article id 024001Article in journal (Refereed)
    Abstract [en]

    Chiral nanocrystalline cellulose (NCC) free-standing films were prepared through slow evaporation of aqueous suspensions of cellulose nanocrystals in a nematic chiral liquid crystal phase. Mueller matrix (MM) spectroscopic ellipsometry is used to study the polarization and depolarization properties of the chiral films. In the reflection mode, the MM is similar to the matrices reported for the cuticle of some beetles reflecting near circular left-handed polarized light in the visible range. The polarization properties of light transmitted at normal incidence for different polarization states of incident light are discussed. By using a differential decomposition of the MM, the structural circular birefringence and dichroism of a NCC chiral film are evaluated.

  • 5.
    Mendoza, Arturo
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. CINVESTAV, Mexico.
    Munoz-Pineda, Eloy
    CINVESTAV, Mexico.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Pitch profile across the cuticle of the scarab beetle Cotinis mutabilis determined by analysis of Mueller matrix measurements2018In: Royal Society Open Science, E-ISSN 2054-5703, Vol. 5, no 12, article id 181096Article in journal (Refereed)
    Abstract [en]

    Helicoidal structures of lamellae of nanofibrils constitute the cuticle of some scarab beetle; with iridescent metallic-like shine reflecting left-handed polarized light. The spectral and polarization properties of the reflected light depend on the pitch of the helicoidal structures, dispersion of effective refractive indices and thicknesses of layers in the cuticle. By modelling the outer exocuticle of the scarab beetle Cotinis mutabilis as a stack of continuously twisted biaxial slices of transparent materials, we extract optical and structural parameters by nonlinear regression analysis of variable-angle Mueller-matrix spectroscopic data. Inhomogeneities in the beetle cuticle produce depolarization with non-uniformity in cuticle thickness as the dominant effect. The pitch across the cuticle of C. mutabilis decreased with depth in a two-level profile from 380 to 335 nm and from 390 to 361 nm in greenish and reddish specimens, respectively, whereas in a yellowish specimen, the pitch decreased with depth in a three-level profile from 388 to 326 nm.

  • 6.
    Bergqvist, Jonas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Uniaxial Anisotropy in PEDOT:PSS Electrodes Enhances the Photocurrent at Oblique Incidence in Organic Solar Cells2018In: ACS Photonics, E-ISSN 2330-4022, Vol. 5, no 8, p. 3023-3030Article in journal (Refereed)
    Abstract [en]

    PEDOT:PSS is a well studied organic conductor, commonly used as a transparent electrode material in printed organic devices such as organic solar cells. PEDOT:PSS thin films are known to be uniaxially anisotropic and exhibit a lower extinction coefficient and lower refractive index in the out of plane direction. To determine the maximum attainable photocurrent in thin film solar cells, the optical power dissipation can be calculated by the transfer matrix method. However, until now the anisotropic properties of PEDOT:PSS films have not been included in the model. In this work we have included an uniaxial anisotropic treatment of PEDOT:PSS films. We investigate reversed and semitransparent solar cells, with aluminum and PEDOT:PSS respectively as the second electrode and PEDOT:PSS as the top electrode, as compared to devices with isotropic PEDOT:PSS electrodes. For p-polarized light at large oblique incidence the inclusion of anisotropy shows a gain of over 7% for the maximum photocurrent in reversed solar cells. In semitransparent solar cells the photocurrent enhancement reaches 4-5% for p-polarized light. However, an enhancement of optical power dissipation and thus photocurrent generation of close to 40% is calculated for wavelengths close to the absorber bandgap. This work shows that for correct calculations of optical power dissipation in devices with PEDOT:PSS electrodes anisotropy should be included in the optical model. This will be especially important to determine the daily energy output of organic solar cells as their expected first markets are on building facades and indoor applications with larger fractions of diffuse light at large oblique incidence.

  • 7.
    Valyukh, Sergiy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Bragg reflection from periodic helicoidal media with laterally graded refractive index2017In: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 72, p. 334-340Article in journal (Refereed)
    Abstract [en]

    Light interaction with a columnar structure of InxAl1-xN where each column is a layered periodic helical medium with laterally graded refractive index is considered. It is demonstrated that such a columnar structure can be presented as a stack of layers with a gradient of the refractive index. To calculate reflectance in the proposed model, the 2 x 2 characteristic matrix method adopted for a gradient index medium was applied. The influence of the refractive indices (including absorption), parameters of the twisting, and thickness of the periodic structure on reflectance is studied. Cases of normal and oblique incident light are considered. The presented medium is a one-dimensional photonic crystal that can be utilized in many devices for light manipulation. (C) 2017 Published by Elsevier B.V.

  • 8.
    Hilfiker, James N.
    et al.
    JA Woollam Co Inc, NE 68508 USA.
    Hale, Jeffrey S.
    JA Woollam Co Inc, NE 68508 USA.
    Herzinger, Craig M.
    JA Woollam Co Inc, NE 68508 USA.
    Tiwald, Tom
    JA Woollam Co Inc, NE 68508 USA.
    Hong, Nina
    JA Woollam Co Inc, NE 68508 USA.
    Schoche, Stefan
    JA Woollam Co Inc, NE 68508 USA.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Estimating depolarization with the Jones matrix quality factor2017In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 421, p. 494-499Article in journal (Refereed)
    Abstract [en]

    Mueller matrix (MM) measurements offer the ability to quantify the depolarization capability of a sample. Depolarization can be estimated using terms such as the depolarization index or the average degree of polarization. However, these calculations require measurement of the complete MM. We propose an alternate depolarization metric, termed the Jones matrix quality factor, QJM, which does not require the complete MM. This metric provides a measure of how close, in a least-squares sense, a Jones matrix can be found to the measured Mueller matrix. We demonstrate and compare the use of QJM to other traditional calculations of depolarization for both isotropic and anisotropic depolarizing samples; including nonuniform coatings, anisotropic crystal substrates, and beetle cuticles that exhibit both depolarization and circular diattenuation. (C) 2016 Elsevier B.V. All rights reserved.

  • 9.
    Mendoza-Galvan, A.
    et al.
    CINVESTAV, Mexico.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Exposing different in-depth pitches in the cuticle of the scarab beetle Cotinis mutabilis2017In: MATERIALS TODAY-PROCEEDINGS, ELSEVIER SCIENCE BV , 2017, Vol. 4, no 4, p. 4969-4978, article id 4Conference paper (Refereed)
    Abstract [en]

    The cuticle of the scarab beetle Cotinis mutabilis reflects left-handed polarized light indicating the presence of a helicoidal structure. Different in-depth pitches in the cuticle are corroborated by optical microscopy images of the cuticle which originally is yellowish or reddish but becomes greenish after gently scratching its top side. Using the Mueller-matrix formalism the degree of polarization (total and circular) of reflected light is determined for unpolarized incident light. The effects of the finite thickness of the cuticle on the broadening and strength of the selective Bragg reflection are discussed on the basis of dispersion relations for optical modes in helicoidal structures and simulated spectra. (C) 2017 The Author(s). Published by Elsevier Ltd.

  • 10.
    Arwin, Hans
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Fernandez Del Rio, Lia
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Åkerlind, Christina
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Swedish Def Research Agency FOI, Div Command and Control Syst, SE-58111 Linkoping, Sweden.
    Valyukh, Sergiy
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Mendoza-Galvan, A.
    CINVESTAV IPN, Mexico.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Landin, Jan
    Linköping University, Department of Physics, Chemistry and Biology, Ecology. Linköping University, Faculty of Science & Engineering.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    On the polarization of light reflected from beetle cuticle2017In: MATERIALS TODAY-PROCEEDINGS, ELSEVIER SCIENCE BV , 2017, Vol. 4, no 4, p. 4933-4941Conference paper (Refereed)
    Abstract [en]

    The use of Mueller matrices for studies of polarizing properties and cuticle structure of scarab beetles are partly reviewed. Specifically we show how the polarization of the reflected light can be quantified in terms of degree of polarization and ellipticity. It is also shown that sum decomposition of Mueller matrices reveals cuticle reflection characteristics in different spectral regions, e.g. in terms of mirrors and circular polarizers. With a differential decomposition of cuticle transmission Mueller matrices, we determine the spectral variation in the fundamental optical properties circular birefringence and dichroism. (C) 2017 Elsevier Ltd. All rights reserved.

  • 11.
    Nygren, K.
    et al.
    Uppsala University, Sweden; Impact Coatings AB, Westmansgatan 29, SE-58216 Linkoping, Sweden.
    Samuelsson, Mattias
    Linköping University, Department of Physics, Chemistry and Biology, Nanoscale engineering. Linköping University, Faculty of Science & Engineering. Impact Coatings AB, Westmansgatan 29, SE-58216 Linkoping, Sweden.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Impact Coatings AB, Westmansgatan 29, SE-58216 Linkoping, Sweden.
    Jansson, U.
    Uppsala University, Sweden.
    Optical methods to quantify amorphous carbon in carbide-based nanocomposite coatings2017In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 638, p. 291-297Article in journal (Refereed)
    Abstract [en]

    We report how the total carbon content and the amorphous carbon (a-C) phase fraction in transition metal carbide/a-C nanocomposite coatings can be obtained using optical methods, which are much more practical for industrial use than conventional X-ray photoelectron spectroscopy. A large set of carbon-containing nanocomposite coatings deposited using different magnetron sputtering techniques were analyzed by X-ray photoelectron spectroscopy, reflectance spectrophotometry, and spectroscopic ellipsometry. The chemical composition and the a-C phase fraction were determined by X-ray photoelectron spectroscopy for each coating and results are presented for the Ti-C, Cr-C, and Nb-C systems. The composition and the a-C phase fraction are correlated to optical reflectance in the visible range, by parametrization in L*a*b* color space, and by ellipsometry primary data. Results show that it is possible to rapidly estimate the composition and the a-C fraction using these optical methods. We propose that optical methods have promising use in the industry as a cost-efficient technique for characterization of carbide-based coatings. (C) 2017 Elsevier B.V. All rights reserved.

  • 12.
    Lunca Popa, Petru
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. LIST, Luxembourg.
    Sønderby, Steffen
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering. Tribol Centre, Denmark; National Oilwell Varco Denmark IS, Denmark.
    Kerdsongpanya, Sit
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Rensselaer Polytech Institute, NY 12180 USA.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Structural, morphological, and optical properties of Bi2O3 thin films grown by reactive sputtering2017In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 624, p. 41-48Article in journal (Refereed)
    Abstract [en]

    Bi2O3 thin films were grown using reactive RF sputtering from a metallic Bi target. The influence of various deposition parameters (substrate temperature, applied power on target and oxygen content in the working gas) on the morphology, structure and optical properties of films was investigated. Depending on the O-2/(Ar + O-2) ratio of the working gas, bismuth, delta-Bi2O3, alpha-Bi2O3 or a mixture of these phases can be deposited, with a narrow window for growth of [111]-oriented delta-Bi2O3 thin films. The delta-Bi2O3 phase is stable from room temperature up to 350 degrees C (in air), where an irreversible transition to alpha-Bi2O3 occurs. This phase transformation is also shown to occur during TEM sample preparation, because of the inherent heating from the ion-milling process, unless liquid -nitrogen cooling is used. (C) 2017 Published by Elsevier B.V.

  • 13.
    Mendoza-Galvan, A.
    et al.
    CINVESTAV, Mexico.
    Munoz-Pineda, E.
    CINVESTAV, Mexico.
    Järrendahl, Kenneth
    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.
    Birefringence of nanocrystalline chitin films studied by Mueller-matrix spectroscopic ellipsometry2016In: Optical Materials Express, ISSN 2159-3930, E-ISSN 2159-3930, Vol. 6, no 2, p. 671-681Article in journal (Refereed)
    Abstract [en]

    Birefringent chitin films were prepared by a dipping technique from aqueous suspensions of chitin nanocrystals in a nematic liquid crystal phase. In the films, chitin nanocrystals are preferentially oriented along the withdrawal direction. Normal incidence transmission Mueller-matrix (M) spectroscopic ellipsometry measurements as a function of sample rotation were used to investigate the optical birefringence in the spectral range 0.73 to 5 eV. Analysis of eigenvalues and depolarization data reveal that the Mueller matrix corresponds to a pure retarder for photon energies below 4 eV and is depolarizing in the range 4 to 5 eV. By modeling the chitin film as a slab with in-plane anisotropy the birefringence was determined. The determination of birefringence was extended to include the range of 4 to 5 eV by a differential decomposition of M. (C) 2016 Optical Society of America

  • 14.
    Karpus, V.
    et al.
    Centre Phys Science and Technology, Lithuania.
    Tumenas, S.
    Centre Phys Science and Technology, Lithuania.
    Eikevicius, A.
    Centre Phys Science and Technology, Lithuania.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Interband optical transitions of Zn2016In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 253, no 3, p. 419-428Article in journal (Refereed)
    Abstract [en]

    Experimental results of an optical study of single-crystal zinc are presented. Components of the Zn dielectric function tensor were measured by spectroscopic ellipsometry in the 0.1-5 eV spectral range. In the NIR-VIS range, the dielectric function spectra show two clearly resolved, polarization-dependent optical features located at about 1 and 1.7 eV. The optical features were analyzed in a framework of parallel-band optical transitions. The performed theoretical calculations of the optical conductivity spectra well reproduce the experimental data with respect to positions, intensities, and polarization dependencies of the observed interband absorption peaks. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • 15.
    Fernandez Del Rio, Lia
    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.
    Polarizing properties and structure of the cuticle of scarab beetles from the Chrysina genus2016In: PHYSICAL REVIEW E, ISSN 2470-0045, Vol. 94, no 1, p. 012409-Article in journal (Refereed)
    Abstract [en]

    The optical properties of several scarab beetles have been previously studied but few attempts have been made to compare beetles in the same genus. To determine whether there is any relation between specimens of the same genus, we have studied and classified seven species from the Chrysina genus. The polarization properties were analyzed with Mueller-matrix spectroscopic ellipsometry and the structural characteristics with optical microscopy and scanning electron microscopy. Most of the Chrysina beetles are green colored or have a metallic look (gold or silver). The results show that the green-colored beetles polarize reflected light mainly at off-specular angles. The gold-colored beetles polarize light left-handed near circular at specular reflection. The structure of the exoskeleton is a stack of layers that form a cusplike structure in the green beetles whereas the layers are parallel to the surface in the case of the gold-colored beetles. The beetle C. gloriosa is green with gold-colored stripes along the elytras and exhibits both types of effects. The results indicate that Chrysina beetles can be classified according to these two major polarization properties.

  • 16.
    Valyukh, Sergiy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. 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, ISSN 1094-4087, 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

  • 17.
    Arwin, Hans
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Mendoza-Galvan, A.
    Cinvestav IPN, Mexico.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Andersson, Anette
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Landin, Jan
    Linköping University, Department of Physics, Chemistry and Biology, Ecology. Linköping University, Faculty of Science & Engineering.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Garcia-Caurel, E.
    University of Paris Saclay, France.
    Ossikovski, R.
    University of Paris Saclay, France.
    Structural circular birefringence and dichroism quantified by differential decomposition of spectroscopic transmission Mueller matrices from Cetonia aurata2016In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 41, no 14, p. 3293-3296Article in journal (Refereed)
    Abstract [en]

    Transmission Mueller-matrix spectroscopic ellipsometry is applied to the cuticle of the beetle Cetonia aurata in the spectral range 300-1000 nm. The cuticle is optically reciprocal and exhibits circular Bragg filter features for green light. By using differential decomposition of the Mueller matrix, the circular and linear birefringence as well as dichroism of the beetle cuticle are quantified. A maximum value of structural optical activity of 560 degrees/mm is found. (C) 2016 Optical Society of America

  • 18.
    Magnusson, Roger
    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, The Institute of Technology.
    Garcia-Caure, Enric
    LPICM, CNRS, Ecole Polytechnique, Université Paris–Saclay, Palaiseau, France.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Ossikovski, Razvigor
    LPICM, CNRS, Ecole Polytechnique, Université Paris–Saclay, Palaiseau, France.
    Sum regression decomposition of spectral and angle-resolved Mueller-matrices from biological reflectors2016In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 55, no 15, p. 4060-4065Article in journal (Refereed)
    Abstract [en]

    In this report we present studies on beetles of the Scarabaeidae family. The selected beetles show brilliant colors and in addition interesting polarization features. Mueller matrices of such beetles are of large interest to explore for biomimetics and for the understanding of the biological relevance of the observed polarization phenomena. Several species of the Scarabaeidae family have been studied by Hodgkinson, Goldstein  and our group to mention some. Ellipticity, degree of polarization and other derived parameters have been reported and Arwin et al. also did optical modeling to determine structural parameters of the scutellum part of the exoskeleton of Cetonia aurata. Mueller matrices are very rich in information about the sample properties and can also be analyzed by addressing depolarization. Cloude showed that a depolarizing Mueller matrix can be represented by a sum of up to four non-depolarizing Mueller matrices weighted by the eigenvalues of the covariance matrix of the Mueller matrix. These eigenvalues are all positive for a physically realizable Mueller matrix and this, so called sum decomposition can be used to filter matrices and obtain a measure of experimental fidelity. The result of the decomposition can also be used to describe a Mueller matrix as a set of basic optical elements having direct physical meaning, such as polarizers and retarders. Pioneering work on decomposition of Mueller-matrix images, including studies of beetles, was performed by Ossikovski et al. We have also previously demonstrated this with Cloude as well as regression decomposition of Mueller matrix spectra and images measured at near-normal incidence on C. aurata. Using Cloude decomposition we found that the experimentally determined Mueller matrix of C. aurata decomposes into a set of a mirror and a circular polarizer. Those results were then the basis for a more stable regression decomposition where the result was confirmed.

  • 19. Chen, Jiaxin
    et al.
    Obitz, C
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Forssgren, B
    CORROSION KINETICS OF NICKEL-BASE ALLOYS WITH HIGH CHROMIUM CONTENTS UNDER SIMULATED BWR NORMAL WATER CHEMISTRY CONDITIONS AND HIGH FLOW VELOCITY2015Conference paper (Refereed)
    Abstract [en]

    In light water reactors corrosion-induced material degradation is a critical issue not only for material integrity but also for plant radiation field build-up. In BWRs nickel-base alloys, such as Alloy 600, Alloy 82 and Alloy 182, are applied in various parts of reactor components including welds. However, their corrosion mechanisms are not very well understood. Although the complex compositions of different nickel-base alloys generally prohibit us to single out some specific alloy constituent having a major impact on alloy corrosion rate, a higher chromium content is often thought to be beneficial to forming a more protective oxide film against corrosion attack. In this paper we report a corrosion kinetics study on high chromium nickel-base alloy welding consumables, Alloy 52M and Alloy 152, under simulated BWR normal water chemistry conditions and high flow velocity for up to nine weeks exposure. The corrosion rates are derived from measurements of weight losses of test coupons, oxide thicknesses with infrared ellipsometry, and microstructures of oxide films with electron microscopy. The obtained corrosion rates are then compared to that for Alloy 182, Alloy 82 and Alloy 600. The results show that the corrosion rate for Alloy 52M is similar to those for Alloy 182, whereas the rate for Alloy 152 is reduced to less than half. These observations indicate that the corrosion kinetics for nickel-base alloys is complex and alloy chromium content alone is not a dominant factor in influencing alloy corrosion rate.

  • 20.
    Magnusson, Roger
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Ossikovski, Razvigor
    LPICM, CNRS, Ecole Polytechnique, Université Paris - Saclay, Palaiseau, France.
    Garcia-caurel, Enric
    LPICM, CNRS, Ecole Polytechnique, Université Paris - Saclay, Palaiseau, France.
    Järrendahl, Kenneth
    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.
    Decomposition of angle resolved spectroscopic Mueller matrices from Scarabaeidae beetles2015Conference paper (Other academic)
    Abstract [en]

    We use angle-dependent Mueller-matrix spectroscopic ellipsometry (MMSE) to determine Mueller matrices of Scarabaeidae beetles which show fascinating reflection properties due to structural phenomena in the exocuticle which are often depolarizing. It has been shown by Cloude [1] that a depolarizing matrix can be decomposed into a sum of up to four non-depolarizing matrices according to M= aM­­1+bM2+cM3+dM4, where a, b, c and d are eigenvalues of the covariance matrix of M. Using the same eigenvalues the matrices Mi can be calculated. This method provides the full solution to the decomposition with both the non-depolarizing matrices and the weight of each of them in the sum.

    An alternative to Cloude decomposition is regression decomposition. Here any Mueller matrix can be decomposed into a set of matrices Mi which are specified beforehand. Whereas in Cloude decomposition the only constraint on the matrices is that they are physically realizable non-depolarizing Mueller matrices, we can now limit the constraint and only use Mueller matrices representing pure optical devices having direct physical meaning, such as polarizers, retarders, etc. This leaves a, b, c, d as fit parameters to minimize the Frobenius norm Mexp -Mreg where Mexp is the experimentally determined Mueller matrix to be decomposed and Mreg is the sum of all Mi. Depending on Mexp an appropriate choice of Mreg matrices has to be made and different values of a, b, c and d are obtained through regression analysis.

    We have previously shown that regression decomposition can be used to show that the Mueller matrix of Cetonia aurata can be decomposed into a sum of a circular polarizer and a mirror [2]. Here we expand the analysis to include angle-resolved spectral Mueller matrices, and also include more species of Scarabaeidae beetles.

    One effect of the decomposition is that when depolarization is caused by an inhomogeneous sample with regions of different optical properties the Mueller matrices of the different regions can be retrieved under certain conditions. Regression decomposition also has potential to be a classification tool for biological samples where a set of standard matrices are used in the decomposition and the parameters a, b, c, d are used to quantify the polarizing properties of the sample.

    [1] Cloude S.R. 1989. Conditions for the physical realisability of matrix operators in polarimetry. Proc. SPIE 1166, Polarization Considerations for Optical Systems II, pp. 177-185

    [2] Arwin H, Magnusson R, Garcia-Caurel E, Fallet C, Järrendahl K, De Martino A, Ossikovski R, 2015. Sum decomposition of Mueller-matrix images and spectra of beetle cuticles. Opt. Express, vol. 23, no. 3, pp. 1951–1966

  • 21.
    Arwin, Hans
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Fernández del Río, Lia
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Landin, Jan
    Linköping University, Department of Physics, Chemistry and Biology, Ecology. Linköping University, The Institute of Technology.
    Mendoza-Galván, Arturo
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology. Unidad Queretaro, Queretaro, Mexico.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Exploring polarization features in light reflection from beetles with structural colors2015In: Proc. SPIE  9429, Bioinspiration, Biomimetics, and Bioreplication 2015, SPIE - International Society for Optical Engineering, 2015, Vol. 9429, p. 942909-1-942909-13Conference paper (Refereed)
    Abstract [en]

    A Mueller matrix of a sample can be used to determine the polarization of  reflected light  for  incident light with arbitrary polarization. The polarization can be quantified  in terms of ellipticity, polarization azimuth and degree of polarization. We apply spectroscopic Mueller-matrix ellipsometry at multiple angles of incidence  to study the cuticle of beetles and derive  polarization features for incident unpolarized light.  In particular we address chiral phenomena in scarab beetles,  the origin of their structural colors and the observed high degree of circular polarization is discussed. Results from beetles in the Scarabaeidae subfamilies Cetoniinae and Rutelinae are presented including specimens with broad-band silver- or gold-like colors with metallic shine as well as specimens with narrow-band green or red reflectors. The variation of polarization with angle of incidence and occurrence of both left-handed and right-handed polarization from a single species are presented. We also use Mueller-matrix spectra in electromagnetic modeling and show how to determine structural parameters including cuticle layer thicknesses and optical properties. Interference oscillations in the observed spectra are due to allowed optical modes and we show how to develop a structural model of a cuticle based on this effect. Sum decomposition of  Mueller matrices measured on a depolarizing cuticle of a beetle is briefly discussed.

  • 22.
    Magnusson, Roger
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hsiao, Ching-Lien
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Sandström, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. 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.
    InxAl1-xN chiral nanorods mimicking the polarization features of scarab beetles2015In: SPIE Proceedings Vol. 942: Bioinspiration, Biomimetics, and Bioreplication 2015 / [ed] Akhlesh Lakhtakia, Mato Knez, Raúl Martín-Palma, SPIE - International Society for Optical Engineering, 2015, Vol. 9429, p. 94290A-1-94290A-8Conference paper (Refereed)
    Abstract [en]

    The scarab beetle Cetonia aurata is known to reflect light with brilliant colors and a high degree of circular polarization. Both color and polarization effects originate from the beetles exoskeleton and have been attributed to a Bragg reflection of the incident light due to a twisted laminar structure. Our strategy for mimicking the optical properties of the Cetonia aurata was therefore to design and fabricate transparent, chiral films. A series of films with tailored transparent structures of helicoidal InxAl1-xN nanorods were grown on sapphire substrates using UHV magnetron sputtering. The value of x is tailored to gradually decrease from one side to the other in each nanorod normal to its growth direction. This introduces an in-plane anisotropy with different refractive indices in the direction of the gradient and perpendicular to it. By rotating the sample during film growth the in-plane optical axis will be rotated from bottom to top and thereby creating a chiral film. Based on Muellermatrix ellipsometry, optical modeling has been done suggesting that both the exoskeleton of Cetonia aurata and our artificial material can be modeled by an anisotropic film made up of a stack of thin layers, each one with its in-plane optical axis slightly rotated with respect to the previous layer. Simulations based on the optical modeling were used to investigate how pitch and thickness of the film together with the optical properties of the constitutive materials affects the width and spectral position of the Bragg reflection band.

  • 23.
    Mendoza-Galván, Arturo
    et al.
    Linköping University, Department of Physics, Chemistry and Biology.
    Muñoz-Pineda, Eloy
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Ribeiro, S.J.L.
    LaMF—UNESP Instituto de Química, Araraquara, Brazil.
    Vieira Dos Santos, M.
    LaMF—UNESP Instituto de Química, Araraquara, Brazil.
    Järrendahl, Kenneth
    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.
    Mueller matrix spectroscopic ellipsometry study of nanocrystalline cellulose free-standing chiral films2015Conference paper (Other academic)
    Abstract [en]

    The astonishing colors exhibited by many birds, insects and other creatures have inspired the development of materials and structures for optical biomimetics. Particularly, aqueous suspensions of cellulose nanocrystals self-assembly in a chiral nematic liquid crystalline phase producing nanocrystalline cellulose (NCC) chiral films after slow evaporation [1] that mimic the left-handed helicoidal arrangement of chitin-protein fibrils found in some beetle cuticles. Owing to the helical structure, left-handed polarized light is selectively reflected from beetle cuticles and NCC chiral films at normal incidence in a spectral band centered at wavelength l0=nL where n is the in-plane average refractive index and L the helix pitch.

    In this work we report the normalized Mueller matrix (M) of NCC free-standing chiral films measured with a dual rotating compensator ellipsometer (J. A. Woollam Co., Inc.) in the wavelength (l) range  250-1000 nm. Measurements performed on NCC films in reflection at angles of incidence (q) between 20 and 75° are shown in the contour map in Fig. 1 and display the same structure as those found in M of beetle cuticles [2]. At q=20° the band of selective reflection of left-handed polarized light (m41=m14<0) is centered at 520 nm. However, NCC chiral films are characterized by a mosaic-like texture as can be observed in the optical microscopy image inserted on the right panel of Fig. 1. The multidomain texture indicates both random helix direction and pitch distribution. Therefore, measurements in different places show selective reflection bands with different spectral characteristics. On the other hand, the transmission of right-handed polarized light (m41=m14>0) is confirmed from measurements at normal incidence, as observed in the right panel of Fig. 1. Other properties of the transmitted light like degree of polarization, ellipticity, and azimuth are determined for incident unpolarized as well as for different polarizations of incident light. Also, circular dichroism and optical rotation of NCC chiral films are evaluated.

    References

    [1] J. A. Kelly et al, Acc. Chem. Res. 47 (2014) 1088−1096.

    [2] E. Muñoz-Pineda et al, Thin Solid Films (2014) http://dx.doi.org/10.1016/j.tsf.2013.11.144

  • 24.
    Åkerlind, Christina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology. Division of Sensor and Electronic Warfare, Swedish Defence Research Agency (FOI), Linköping, Sweden .
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Hallberg, Tomas
    Division of Sensor and Electronic Warfare, Swedish Defence Research Agency (FOI), Linköping, Sweden .
    Landin, Jan
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Gustafsson, Johan
    Division of Defence and Security, Systems and Technology, Swedish Defence Research Agency (FOI), Sweden.
    Kariis, Hans
    Division of Sensor and Electronic Warfare, Swedish Defence Research Agency (FOI), Linköping, Sweden .
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Scattering and Polarization Properties of the Scarab Beetle Cyphochilus insulanus cuticle2015In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 54, no 19Article in journal (Refereed)
    Abstract [en]

    Optical properties of natural photonic structures can inspire material developments in diversified areas, such as the spectral design of surfaces for camouflage. Here, reflectance, scattering, and polarization properties of the cuticle of the scarab beetle Cyphochilus insulanus are studied with spectral directional hemispherical reflectance, bidirectional reflection distribution function (BRDF) measurements, and Mueller-matrix spectroscopic ellipsometry (MMSE). At normal incidence, a reflectance (0.6–0.75) is found in the spectral range of 400–1600 nm and a weaker reflectance <0.2  in the UV range as well as for wavelengths >1600  nm  . A whiteness of 𝑊=42  is observed for mainly the elytra of the beetle. Chitin is a major constituent of the insect cuticle which is verified by the close similarity of the measured IR spectrum to that of 𝛼  -chitin. The BRDF signal shows close-to-Lambertian properties of the beetle for visible light at small angles of incidence. From the MMSE measurement it is found that the beetles appear as dielectric reflectors reflecting linearly polarized light at oblique incidence with low gloss and a low degree of polarization. The measured beetle properties are properties that can be beneficial in a camouflage material.

  • 25.
    Arwin, Hans
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Garcia-Caurel, Enric
    Laboratoire des Physique des Interfaces et Couches Minces, Ecole Polytechnique, CNRS, France.
    Fallet, C.
    Bioaxial SAS, 40 rue de Paradis, France.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Foldyna, M.
    Laboratoire des Physique des Interfaces et Couches Minces, Ecole Polytechnique, CNRS, France.
    De Martino, A.
    Laboratoire des Physique des Interfaces et Couches Minces, Ecole Polytechnique, CNRS, France.
    Ossikovski, R.
    Laboratoire des Physique des Interfaces et Couches Minces, Ecole Polytechnique, CNRS, France.
    Sum decomposition of Mueller-matrix images and spectra of beetle cuticles2015In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 23, no 3, p. 1951-1966Article in journal (Refereed)
    Abstract [en]

    Spectral Mueller matrices measured at multiple angles of incidence as well as Mueller matrix images are recorded on the exoskeletons (cuticles) of the scarab beetles Cetonia aurata and Chrysina argenteola. Cetonia aurata is green whereas Chrysina argenteola is gold-colored. When illuminated with natural (unpolarized) light, both species reflect left-handed and near-circularly polarized light originating from helicoidal structures in their cuticles. These structures are referred to as circular Bragg reflectors. For both species the Mueller matrices are found to be nondiagonal depolarizers. The matrices are Cloude decomposed to a sum of non-depolarizing matrices and it is found that the cuticle optical response, in a first approximation can be described as a sum of Mueller matrices from an ideal mirror and an ideal circular polarizer with relative weights determined by the eigenvalues of the covariance matrices of the measured Mueller matrices. The spectral and image decompositions are consistent with each other. A regression-based decomposition of the spectral and image Mueller matrices is also presented whereby the basic optical components are assumed to be a mirror and a circular polarizer as suggested by the Cloude decomposition. The advantage with a regression decomposition compared to a Cloude decomposition is its better stability as the matrices in the decomposition are determined a priori. The origin of the depolarizing features are discussed but from present data it is not possible to conclude whether the two major components, the mirror and the circular polarizer are laterally separated in domains in the cuticle or if the depolarization originates from the intrinsic properties of the helicoidal structure.

  • 26.
    Bergqvist, Jonas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Uniaxial anisotropy in PEDOT:PSS electrodes enhances the photo current at oblique incidence in organic solar cells2015Manuscript (preprint) (Other academic)
    Abstract [en]

    In this work an uniaxial anisotropic treatment of the transparent conductor PEDOT:PSS is included in the transfer matrix method (TMM), used to calculate the optical power dissipation in organic solar cells. PEDOT:PSS is known to be anisotropic and exhibit a weaker absorption and lower refractive index in the out of plane direction. For p-polarized light at large oblique incidence the inclusion of anisotropy show a gain of over 10% for the maximum photocurrent as compared to an isotropic treatment. Due to the interference in devices with reflecting bottom electrodes, the active layer absorption gain is not always occurring for the wavelengths with highest dichroism. This work show that using PEDOT:PSS as top electrode further strengthens the argument that thin film solar cells perform better than their silicon counterparts under oblique incidence. We also confirm previous studies showing that the optical interference maxima is shifted to slightly thicker films for oblique incidence for solar cells with reflective bottom electrodes.

  • 27.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Adsorption of Proteins at Solid Surfaces2014In: Ellipsometry of Functional Surfaces and Films / [ed] Hinrichs, Karsten; Eichhorn Klaus-Jochen, Springer Berlin/Heidelberg, 2014, p. 29-46Chapter in book (Refereed)
    Abstract [en]

    Ellipsometry has a very high thin film sensitivity and can resolve sub-nm changes in the thickness of a protein film on a solid substrates. Being a technique based on photons in and photons out it can also be applied at solid-liquid interfaces. Ellipsometry has therefore found many in situ applications on protein layer dynamics but studies of protein layer structure are also frequent. Numerous ex situ applications on detection and quantification of protein layers are found and several biosensing concepts have been proposed. In this chapter, the use of ellipsometry in the above mentioned areas is reviewed and experimental methodology including cell design is briefly discussed. The classical ellipsometric challenge to determine both thickness and refractive index of a thin film is addressed and an overview of strategies to determine surface mass density is given. Included is also a discussion about spectral representations of optical properties of a protein layer in terms of a model dielectric function concept and its use for analysis of protein layer structure.

  • 28.
    Magnusson, Roger
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Hsiao, Ching-Lien
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. 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.
    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.
    Chiral nanostructures producing near circular polarization2014In: Optical Materials Express, ISSN 2159-3930, E-ISSN 2159-3930, Vol. 4, no 7, p. 1389-1403Article in journal (Refereed)
    Abstract [en]

    Optical properties of chiral nanostructured films made of Al1-xInxN using a new growth mechanism - curved-lattice epitaxial growth - are reported. Using this technique, chiral films with right- and left-handed nanospirals were produced. The chiral properties of the films, originating mainly from an internal anisotropy and to a lesser extent from the external helical shape of the nanospirals, give rise to selective reflection of circular polarization which makes them useful as narrow-band near-circular polarization reflectors. The chiral nanostructured films reflect light with high degree of circular polarization in the ultraviolet part of the spectrum with left- and right-handedness depending on the handedness of the nanostructures in the films.

  • 29.
    Arwin, Hans
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Fernández del Río, Lia
    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.
    Comparison and analysis of Mueller-matrix spectra from exoskeletons of blue, green and red Cetonia aurata2014In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 571, p. 739-743Article in journal (Refereed)
    Abstract [en]

    The exoskeleton, also called the cuticle, of specimens of the scarab beetle Cetonia aurata is a narrow-band reflector which exhibits metallic shine. Most specimens of C. aurata have a reflectance maximum in the green part of the spectrum but variations from blue–green to red–green are also found. A few specimens are also more distinct blue or red. Furthermore, the reflected light is highly polarized and at near-normal incidence near-circular left-handed polarization is observed. The polarization and color phenomena are caused by a nanostructure in the cuticle. This nanostructure can be modeled as a multilayered twisted biaxial layer from which reflection properties can be calculated. Specifically we calculate the cuticle Mueller matrix which then is fitted to Mueller matrices determined by dual-rotating compensator ellipsometry in the spectral range 400–800 nm at multiple angles of incidence. This non-linear regression analysis provides structural parameters like pitch of the chiral structure as well as layer refractive index data for the different layers in the cuticle. The objective here is to compare spectra measured on C. aurata with different colors and develop a generic structural model. Generally the degree of polarization is large in the spectral region corresponding to the color of the cuticle which for the blue specimen is 400–600 nm whereas for the red specimen it is 530–730 nm. In these spectral ranges, the Mueller-matrix element m41 is non-zero and negative, in particular for small angles of incidence, implicating that the reflected light becomes near-circularly polarizedwith an ellipticity angle in the range 20°–45°.

  • 30.
    Mendoza, Arturo
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology. Cinvestav-Querétaro, Mexico.
    Muñoz-Pineda, Eloy
    Cinvestav-Querétaro, Mexico.
    Järrendahl, Kenneth
    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.
    Evidence for a dispersion relation of optical modes in the cuticle of the scarab beetle Cotinis mutabilis2014In: Optical Materials Express, ISSN 2159-3930, E-ISSN 2159-3930, Vol. 4, no 12, p. 2484-2496Article in journal (Refereed)
    Abstract [en]

    Variable angle Mueller matrix spectroscopic ellipsometry is used to study the properties of light reflected from the exoskeleton (cuticle) of the scarab beetle Cotinis mutabilis. For unpolarized incident light, the ellipticity and degree of polarization of the reflected light reveal a lefthanded helical structure in the beetle cuticle. Analysis of the spectral position of the maxima and minima in the interference oscillations of the Mueller-matrix elements provides evidence for a dispersion relation similar to that of optical modes in chiral nematic liquid crystals calculated within a two-wave approximation. Additionally, a structural model for the cuticle of C. mutabilis is derived from the properties of the optical modes for nonattenuated propagation or selective reflection.

  • 31.
    Arwin, Hans
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Fernández del Río, Lia
    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. Swedish Defence Research Agency, Linköping, Sweden.
    Muñoz-Pineda, Eloy
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology. Cinvestav-IPN, Unidad Querétaro, Libramiento Norponiente 2000, 76230 Querétaro, Mexico.
    Landin, Jan
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Mendoza-Galván, Arturo
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Cinvestav-IPN, Unidad Querétaro, Libramiento Norponiente 2000, 76230 Querétaro, Mexico.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Exploring optics of beetle cuticles with Mueller-matrix ellipsometry2014In: Materials Today, ISSN 1369-7021, E-ISSN 1873-4103, Vol. 1S, p. 155-160Article in journal (Refereed)
    Abstract [en]

    Spectroscopic Mueller-matrix ellipsometry at variable angles of incidence is applied to beetle cuticles using a small (50 -100 μm) spot size. It is demonstrated how ellipticity and degree of polarization of the reflected light can be derived from a Mueller matrix providing a detailed insight into reflection properties. Results from Cetonia aurata, Chrysina argenteola and Cotinis mutabilis are presented. The use of Mueller matrices in regression analysis to extract structural and optical parameters of cuticles is briefly described and applied to cuticle data from Cetonia aurata whereby the pitch of the twisted layered structure in the cuticle is determined as well as the refractive indices of the epicuticle and the exocuticle.

  • 32.
    Magnusson, Roger
    et al.
    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.
    Sandström, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hsiao, Ching-Lien
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. 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.
    Optical Mueller Matrix Modeling of Chiral AlxIn1-xN Nanospirals2014In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 571, p. 447-452Article in journal (Refereed)
    Abstract [en]

    Metamaterials in the form of chiral nanostructures have shown great potential for applications such as chemical and biochemical sensors and broadband or wavelength tunable circular polarizers. Here we demonstrate a method to produce tailored transparent chiral nanostructures with the wide-bandgap semiconductor AlxIn1 − xN. A series of anisotropic and transparent films of AlxIn1 − xN were produced using curved-lattice epitaxial growth on metallic buffer layers. By controlling the sample orientation during dual magnetron sputter deposition, nanospirals with right-handed or left-handed chirality were produced. Using a dual rotating compensator ellipsometer in reflection mode, the full Mueller matrix was measured in the spectral range 245–1700 nm at multiple angles of incidence. The samples were rotated one full turn around their normal during measurements to provide a complete description of the polarization properties in all directions. For certain wavelengths, unpolarized light reflected off these films becomes highly polarized with a polarization state close to circular. Nanostructured films with right- and left-handed chirality produce reflections with right- and left-handed near-circularly polarized light, respectively. A model with a biaxial layer in which the optical axes are rotated from bottom to top was fitted to the Mueller-matrix data. Hence we can perform non-destructive structural analysis of the complex thin layers and confirm the tailored structure. In addition, the refractive index, modeled with a biaxial Cauchy dispersion model, is obtained for the AlxIn1 − xN films.

  • 33.
    Valyukh, Iryna
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Jiao, Z.
    Nanyang Technological University, Singapore.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Sun, X. W.
    Nanyang Technological University, Singapore.
    Optical Properties of Hydrated Tungsten Trioxide 3WO3ˑH2O 2014In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 571, p. 644-647Article in journal (Refereed)
    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.

  • 34.
    Fernandez Del Rio, Lia
    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.
    Polarization of light reflected from Chrysina gloriosa under various illuminations2014In: Materials Today: Proceedings, Elsevier Ltd , 2014, Vol. 1, p. 172-176Conference paper (Refereed)
    Abstract [en]

    When illuminated with unpolarized light, the scarab beetle Chrysina gloriosa, reflects left-handed near-circularly polarized light for a broad range of angles of incidence and wavelengths in the visible. It is, however, known that light scattered from the sky, reflected on water or transmitted through leaves often is linearly polarized. In this study we have analysed the polarization of light reflected on this beetle when illuminated with different polarization states of light. We have also analysed how the response would be with a polarization-sensitive detector. The reflected irradiance is shown to be highest when the incident light is s-polarized or left-handed polarized and the detector is unpolarized (or vice versa). In the case in which both, the source and the detector, are polarized, the irradiance is highest when both are s-polarized. On the contrary the visibility is low when the source is s-polarized and the detector is p-polarized.

  • 35.
    Järrendahl, Kenneth
    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.
    Polarizing Natural Nanostructures2014In: Ellipsometry of Functional Organic Surfaces and Films / [ed] Hinrichs, Karsten; Eichhorn Klaus-Jochen, Springer Berlin/Heidelberg, 2014, p. 155-169Chapter in book (Refereed)
    Abstract [en]

    A brief description of the polarizing environment we are living in and the possibilities for some animals to detect this polarization is made. This is followed by a presentation of how animals and plants generate polarized light, usually through reflection from micro- and nanostructures. Special attention is made to scarab beetles reflecting light with a high degree of circular polarization. Finally some comments on the biological aspects of polarization are made.

  • 36.
    Fernandez Del Rio, Lía
    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.
    Polarizing properties and structural characteristics of the cuticle of the scarab Beetle Chrysina gloriosa2014In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 571, no 3, p. 410-415Article in journal (Refereed)
    Abstract [en]

    The scarab beetle Chrysina gloriosa is green with gold-colored stripes along its elytras. The properties of light reflected on these areas are investigated using Mueller-matrix spectroscopic ellipsometry. Both areas reflect light with high degree of left-handed polarization but this effect occurs for specular reflection for the gold-colored areas and for off-specular angles for the green areas. The colors and polarization phenomena originate from reflection of light in the cuticle and a structural analysis is presented to facilitate understanding of the different behaviors of these two areas. Scanning electron microscopy (SEM) images of the cross section of beetle cuticles show a multilayered structure. On the gold-colored areas the layers are parallel to the surface whereas on the green-colored areas they form cusp-like structures. Optical microscopy images show a rather flat surface in the gold-colored areas compared to the green-colored areas which display a net of polygonal cells with star-shaped cavities in the center. Each of the polygons corresponds to one of the cusps observed in the SEM images. Atomic force microscopy images of the star-shaped cavities are also provided. The roughness of the surface and the cusp-like structure of the green-colored areas are considered to cause scattering on this area.

  • 37.
    Muñoz-Pineda, Eloy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology. Cinvestav-IPN, Unidad Querétaro, Libramiento Norponiente 2000, Querétaro, Mexico.
    Järrendahl, Kenneth
    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.
    Mendoza-Galván, Arturo
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology. Cinvestav-IPN, Unidad Querétaro, Libramiento Norponiente 2000, Querétaro, Mexico.
    Symmetries and relationships between elements of the Mueller matrix spectra of the cuticle of the beetle Cotinis mutabilis2014In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 571, p. 660-665Article in journal (Refereed)
    Abstract [en]

    The optical properties of light reflected from the cuticle of the scarab beetle Cotinis mutabilis are studied using variable angle Mueller matrix spectroscopic ellipsometry. Reflection of left-handed polarized light is demonstrated. Large amplitude interference oscillations in the elements of the normalized Mueller matrix (M) reveal highly transparent materials comprising the beetle cuticle. Off-diagonal elements in M obey simple symmetry relationships due to the constraint in the cross-polarized reflection coefficients between p and s polarizations of chiral systems, rps = − rsp. Based on the latter constraint and further interrelationships experimentally investigated, the number of independent elements in M resulted in only six. Reciprocity is probed from measurements performed in opposite sample orientations and the effects on M due to sample rotation by 90° are discussed. The results suggest relatively large areas in the cuticle of C. mutabilis with a helicoidal structure comprised of fibrils with a well-defined orientation.

  • 38.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    TIRE and SPR-enhanced SE for adsorption processes2014In: Ellipsometry of Functional Organic Surface and Films / [ed] Hinrichs, Karsten; Eichhorn, Klaus-Jochen, Springer Berlin/Heidelberg, 2014, p. 249-264Chapter in book (Refereed)
    Abstract [en]

    Ellipsometry configurations in internal reflection mode facilitate studies of adsorption processes without the light beam passing through the medium from which adsorption occurs. Monitoring of adsorption processes on surfaces in opaque media is thus possible. If the surface in addition has a thin semitransparent metal film in which surface plasmon polaritons can be excited, one can achieve very high sensitivity to small changes in surface mass density of an adsorbed biolayer. Thickness changes as small as one pm can be resolved. In this chapter the theory for Total Internal Reflection Ellipsometry (TIRE), also called surface plasmon resonance enhanced ellipsometry, will be described and instrumentation will be briefly discussed. TIRE applied in spectroscopic as well as in angle of incidence interrogation modes will be considered. Finally applications in the areas of bioadsorption processes, biosensing, gas adsorption and biolayer imaging will be reviewed.

  • 39. Gustafsson, C
    et al.
    Chen, Jiaxin
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Forsgren, B
    Corrosion Kinetics of Nickel-base Alloys in Simulated BWR Conditions under High Flow Velocity2013Conference paper (Refereed)
    Abstract [en]

    Corrosion-induced material degradation of nickel-base alloys is a critical issue of material integrity and plant operation safety. It is therefore important to determine alloy corrosion rates and to examine corrosion resistant properties of the oxide films formed on the alloy surfaces. This paper contributes to a corrosion kinetic study on nickel-base alloys 82, 182 and 600 in a specially constructed loop system capable of simulating BWR water environments under high flow velocity. The corrosion rate data are derived from measurements of weight changes of test coupons, oxide thicknesses with infrared ellipsometry, and microstructures of oxide films with high resolution electron microscopy. For the alloys examined, corrosion rates decreased with time, suggesting that the formed oxide films were likely protective. Although the overall thicknesses of the oxide films on Alloy 82 and 600 were vastly different from each other, they corroded equally much after nine weeks exposure. Comparing the corrosion rates for Alloys 182 and 600, on the other hand, one finds that the very thick oxide films formed on Alloy 600 did not make the alloy corrode more slowly but more rapidly. These observations indicate that the overall thickness of oxide scales, being largely porous, did not contribute to alloy corrosion protection. The possible rate-limiting step occurring in the inner-most thin but tenacious oxide films at the metal/oxide interface regions is briefly discussed.

  • 40.
    Arwin, Hans
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Berlind, Torun
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Johs, Blaine
    JA Woollam Co Inc, NE USA .
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Cuticle structure of the scarab beetle Cetonia aurata analyzed by regression analysis of Mueller-matrix ellipsometric data2013In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 21, no 19, p. 22645-22656Article in journal (Refereed)
    Abstract [en]

    Since one hundred years it is known that some scarab beetles reflect elliptically and near-circular polarized light as demonstrated by Michelson for the beetle Chrysina resplendens. The handedness of the polarization is in a majority of cases left-handed but also right-handed polarization has been found. In addition, brilliant colors with metallic shine are observed. The polarization and color effects are generated in the beetle exoskeleton, the so-called cuticle. The objective of this work is to demonstrate that structural parameters and materials optical functions of these photonic structures can be extracted by advanced modeling of spectral multi-angle Mueller-matrix data recorded from beetle cuticles. A dual-rotating compensator ellipsometer is used to record normalized Mueller-matrix data in the spectral range 400 – 800 nm at angles of incidence in the range 25–75°. Analysis of data measured on the scarab beetle Cetonia aurata are presented in detail. The model used in the analysis mimics a chiral nanostructure and is based on a twisted layered structure. Given the complexity of the nanostructure, an excellent fit between experimental and model data is achieved. The obtained model parameters are the spectral variation of the refractive indices of the cuticle layers and structural parameters of the chiral structure.

  • 41.
    Hollertz, Rebecca
    et al.
    KTH Royal Institute Technology, Sweden.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Faure, Bertrand
    Stockholm University, Sweden.
    Zhang, Yujia
    KTH Royal Institute Technology, Sweden.
    Bergstrom, Lennart
    Stockholm University, Sweden.
    Wagberg, Lars
    KTH Royal Institute Technology, Sweden.
    Dielectric properties of lignin and glucomannan as determined by spectroscopic ellipsometry and Lifshitz estimates of non-retarded Hamaker constants2013In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 20, no 4, p. 1639-1648Article in journal (Refereed)
    Abstract [en]

    We present in this study a quantitative estimate of the dispersive interactions between lignin, hemicellulose and cellulose, which are the dominating components in wood and also extensively used to produce paper and packaging materials. The dielectric properties in the UV-visible region of spin-coated films of pure lignin and glucomannan were determined by spectroscopic ellipsometry. The non-retarded Hamaker constants were estimated from the determined spectral parameters using Lifshitz theory for lignin and glucomannan interacting with cellulose, titania and calcium carbonate in vacuum, water and hexane. The Hamaker constants for the different combinations of cellulose, lignin and glucomannan fall within a relatively narrow range of 35–58 and 8–17 zJ, for the values in vacuum (air) and water, respectively. The estimated Hamaker constants for the interactions of the wood components with TiO2 and CaCO3, common additives in paper, in water range from 3 to 19 zJ, thus being similar in magnitude as the interactions between the wood components themselves. In contrast, the Hamaker constant is essentially zero for glucomannan interacting with calcium carbonate in hexane. The Hamaker constants for lignin, hemicellulose and cellulose determined in this study can provide information regarding the surface interactions important for e.g. adhesion, friction, swelling and wetting in paper processing as well as for the resulting behavior of paper products.

  • 42.
    Rehammar, Robert
    et al.
    Department of Applied Physics, Chalmers University of Technology, Göteborg, Sweden.
    Ghavanini, Farzan Alavian
    Department of Microtechnology and Nanoscience, Chalmers University of Technology, Göteborg, Sweden.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Kinaret, Jari
    Department of Applied Physics, Chalmers University of Technology, Göteborg, Sweden.
    Enoksson, Peter
    Department of Microtechnology and Nanoscience, Chalmers University of Technology, Göteborg, Sweden.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Campbell, Eleanor
    University of Edinburgh, Scotland.
    Electromechanically Tunable Carbon Nanofiber Photonic Crystal2013In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 13, no 2, p. 397-401Article in journal (Refereed)
    Abstract [en]

    We demonstrate an electrically tunable 2D photonic crystal array constructed from vertically alignedcarbon nanofibers. The nanofibers are actuated by applying a voltage between adjacent carbon nanofiberpairs grown directly on metal electrodes, thus dynamically changing the form factor of the photoniccrystal lattice. The change in optical properties is characterised using optical diffraction andellipsometry. The experimental results are shown to be in agreement with theoretical predictions andprovide a proof-of-principle for rapidly switchable photonic crystals operating in the visible that can befabricated using standard nanolithography techniques combined with plasma CVD growth of thenanofibers.

  • 43.
    Johansson, Malin B.
    et al.
    Uppsala University, Sweden .
    Baldissera, Gustavo
    Royal Institute of Technology KTH, Stockholm, Sweden .
    Valyukh, Iryna
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Persson, Clas
    Royal Institute of Technology KTH, Stockholm, Sweden .
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Niklasson, Gunnar A.
    Uppsala University, Sweden .
    Osterlund, Lars
    Uppsala University, Sweden .
    Electronic and optical properties of nanocrystalline WO3 thin films studied by optical spectroscopy and density functional calculations2013In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 25, no 20, p. 205502-Article in journal (Refereed)
    Abstract [en]

    The optical and electronic properties of nanocrystalline WO3 thin films prepared by reactive dc magnetron sputtering at different total pressures (P-tot) were studied by optical spectroscopy and density functional theory (DFT) calculations. Monoclinic films prepared at low P-tot show absorption in the near infrared due to polarons, which is attributed to a strained film structure. Analysis of the optical data yields band-gap energies E-g approximate to 3.1 eV, which increase with increasing P-tot by 0.1 eV, and correlate with the structural modifications of the films. The electronic structures of triclinic delta-WO3, and monoclinic gamma- and epsilon-WO3 were calculated using the Green function with screened Coulomb interaction (GW approach), and the local density approximation. The delta-WO3 and gamma-WO3 phases are found to have very similar electronic properties, with weak dispersion of the valence and conduction bands, consistent with a direct band-gap. Analysis of the joint density of states shows that the optical absorption around the band edge is composed of contributions from forbidden transitions (andgt;3 eV) and allowed transitions (andgt;3.8 eV). The calculations show that E-g in epsilon-WO3 is higher than in the delta-WO3 and gamma-WO3 phases, which provides an explanation for the P-tot dependence of the optical data.

  • 44.
    Bergqvist, Jonas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Mauger, Scott
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Tvingstedt, Kristofer
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    In situ reflectance imaging of organic thin film formation from solution deposition2013In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 114, p. 89-98Article in journal (Refereed)
    Abstract [en]

    In this work we present reflectance imaging as a suitable method for in situ monitoring of the drying process of film formation for organic photovoltaics (OPV) over large areas, as well as for lab-scale spin-coating. The drying wet film is illuminated with a narrow bandwidth LED with the specularly reflected light recorded by a video camera as the film dries and forms the active layer of the OPV cell. The interference fringes generated by the thinning wet film can be used to measure the rate of solvent evaporation and the drying time. Subsequent mapping elucidates variations in drying conditions over the substrate, which lead to variations in morphology formation. The technique is suitable for tracking thickness variations of the dry film, with a sensitivity of 10 nm, by comparing the intensity of the reflected light from the dry film to simulated interference conditions calculated for each thickness. The drying process is furthermore accurately simulated by an optical model considering the changes in refractive index as the amount of solvent decreases with respect to the solid content. This non-invasive in situ method represents an important monitoring tool for future large scale OPV manufacturing where high performing morphologies with uniform thickness have to be formed over very large areas.

  • 45.
    Karpus, V
    et al.
    Institute Semicond Phys, Lithuania.
    Tumenas, S
    Institute Semicond Phys, Lithuania.
    Suchodolskis, A
    Institute Semicond Phys, Lithuania.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Assmus, W
    Goethe University of Frankfurt, Germany.
    Optical spectroscopy and electronic structure of the face-centered icosahedral quasicrystals Zn-Mg-R (R=Y, Ho, Er)2013In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 88, no 9Article in journal (Refereed)
    Abstract [en]

    Results of optical spectroscopy studies of the face-centered icosahedral (fci) single-grain Zn-Mg-Y, Zn-Mg-Ho, and Zn-Mg-Er quasicrystals (QCs) are presented. The dielectric function of the QCs was measured in the 0.01–6 eV spectral range by IR-UV spectroscopic ellipsometry and far infrared reflection spectroscopy techniques. A theoretical scheme of optical conductivity calculations is extended to account for the Fermi level positions within and below a pseudogap. The model of the QC electron energy spectrum, based on a band structure hypothesis, is suggested, which treats the electronic subsystem as a nearly free electron gas affected by intersections of the Fermi surface with several families of Bragg planes. The experimental optical spectra are reproduced in detail by theoretical calculations carried out within the framework of the model. The parameters of the electron energy spectrum deduced from an analysis of optical data are close to those previously determined in an analysis of fci Zn-Mg-R valence band photoemission spectra.

  • 46.
    Lansåker, Pia
    et al.
    Uppsala University, Uppsala, Sweden.
    Tuncer, Enis
    3M Austin Center, Austin, USA.
    Valyukh, Iryna
    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.
    Niklasson, Gunnar
    Uppsala University, Uppsala, Sweden.
    Granqvist, Claes Göran
    Uppsala University, Uppsala, Sweden.
    Spectral  density analysis of thin gold films: Thickness and structure dependence of the optical properties2013In: Proceedings, ISSN 0351-6067, p. 443-447Article, book review (Other academic)
    Abstract [en]

    In this paper we study the feasibility of representing the optical properties of ultrathin gold films by effective medium theories. Gold films with mass thicknesses in the range of 1.4 to 9.2 nm were deposited by DC magnetron sputtering onto non-heated glass substrates. Optical measurements in the range 0.25 to 2 µm were carried out by spectroscopic ellipsometry, and the effective complex dielectric function of each film was determined. The gold films were modelled as a mixture of gold and air, and a general effective medium description using the spectral density function (SDF) was used to describe their optical properties. Numerical inversion of the experimental dielectric function gave a broad and rather featureless SDF with a few superimposed peak structures, both for island structures and percolating films. The broad background is qualitatively similar to the predictions of the Bruggeman [Ann. Phys. (Leipzig), 5th series, 24 (1935) 636-679] model.

  • 47.
    Fernández del Río, Lia
    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.
    Landin, Jan
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, The Institute of Technology.
    Magnusson, Roger
    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.
    A Mueller Matrix Spectroscopic Ellipsometry Study of Scarab Beetles of the Chrysina Genus2012Conference paper (Other academic)
    Abstract [en]

    The attractive shiny metallic colour of jewel scarabs is originating from the structure of the exoskeleton.For some directions and wavelengths of the incident light this structure will also cause the reflectedlight to have a large ellipticity (near-circular polarization). This is due to that the exoskeleton is ahelicoidal structure, formed by layers of chitin molecules. The reflected light is most commonly lefthandedpolarized but right-handed polarization is also observed. In this work six species of Scarabbeetles from the Chrysina genus are investigated. The complete Mueller-matrix is measured with adual rotating compensator ellipsometer (RC2, J.A.Woollam Co., Inc.). The results are presented ascontour plots where we represent different parameters as a function of incidence angle 2[25; 75]and wavelength 2[240; 1000]nm of the incident beam. Parameters of particular interest are the m41element of the Mueller-matrix, which is related to the circular polarization behaviour, the degree ofpolarization, the ellipticity and the absolute value of the azimuth angle. From ocular observationsthrough left- and right-circularly polarizing filters all specimens showed clear polarization effects interms of colour changes. However, the Mueller matrix ellipsometry measurements showed two generaltypes of polarization behaviour depending on the studied species. Chrysina macropus and Chrysinaperuviana had a smaller range of m41 values around zero. Much larger m41 variations were observedfor Chrysina argenteola, Chrysina chrysargyrea and Chrysina resplendens. Chrysina gloriosa hadboth types of polarization behaviour depending on if the measurements where made on the green orgolden parts of this striped beetle. Comparisons among samples of beetles from the same species wereconducted. For instance, different specimens of Chrysina resplendens show rather large differences inthe polarization response whereas specimens of Chrysina chrysargyrea showed very similar polarizationbehaviour. All studied specimens did in some sense reflect both right- and left-handed polarizedlight. In many cases very high ellipticities (near-circular polarization states) were observed. Modelsof structures generating the observed polarization effects as well as biological aspects will also bediscussed.Figure 257: Three pictures of C. chrysargyrea from left to right taken with aleft-circular polarizer, no filters and with a right-circular polarizer in front of thecamera. Two contour plots of m41 for C. chrysargyrea showing a large region withleft-handed near-circular polarization and C. resplendens showing a large regionwith right-handed near-circular polarization.

  • 48.
    Arwin, Hans
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Johs, Blaine
    J. A. Woollam Co., Inc..
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Analysis of Mueller-matrix data from chiral structures in exoskeletons of scarab beetles2012Conference paper (Other academic)
    Abstract [en]

    Several species of scarab beetles exhibit extra-ordinary metallic-like structural colors. These color-generating structures also show complex polarization properties and unpolarized light can be reflected with near-circular polarization. Specimens of Cetonia aurata (Linnaeus, 1758) are here studied with a dual-rotating compensator ellipsometer using focusing probes. Mueller-matrix data are recorded with precision better than ±0.005 in the range 350 – 1000 nm for angles 20-60º. In a narrow spectral range in the green part of the spectrum, the Mueller-matrix elements m14 and m41 show large negative values and the reflected light is near-circular left-handed polarized. This effect originates from a chiral structure in the beetle exoskeleton. A twisted biaxial lamellae structure with a top dielectric layer is used in regression analysis to determine pitch of the helix and refractive indices of the chitin-based constituting materials. The applicability of this model to data from different scarab beetles is reviewed and it is found that the model show limitations for beetles with broad-band reflection, e.g. those with gold-like colors. For narrow-band optical features, the model provides an excellent fit for all 15 normalized Mueller-matrix elements over the full spectrum and angle of incidence range. Dispersion models like Cauchy, b-splines and oscillator-based models are employed for the biaxial layer and fit qualities for the tested models are compared.

  • 49.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Analysis of photonic structures in beetles using Mueller-matrix data2012Conference paper (Other academic)
    Abstract [en]

    Since one hundred years it is known that some scarab beetles reflect elliptically polarized light as demonstrated by Michelson (Phil. Mag. 21(1911)544) for the beetle Chrysina resplendens. The handedness of the polarization is in a majority of cases left-handed but also right-handed polarization has been found. The polarization and color effects are generated in the outer part of the exoskeleton, the so called cuticle. Our objective is here to demonstrate that structural parameters and materials optical functions of these photonic structures can be extracted by advanced modeling of spectral multi-angle Mueller-matrix data recorded from beetle cuticles.

    A dual rotating compensator ellipsometer (RC2, J. A. Woollam Co., Inc.) is used to record normalized Mueller-matrix elements mij (i,j=1..4) in the spectral range 300 – 900 nm at angles of incidence in the range 20-75º. All measurements are performed on the scutellum (a small triangular part on the dorsal side of the beetles) with focusing optics resulting in a spot size of the order of 0.05-0.1 mm. The software CompleteEASE (J. A. Woollam Co., Inc.) is used for regression analysis. Analysis of data measured on Cetonia aurata will be presented in detail and data from other beetles in the Cetoniinae and Rutelinae subfamilies will be briefly discussed.

    A contour plot of Mueller-matrix data measured on Cetonia aurata (insert) is shown below. This beetle has a metallic shine and if illuminated with unpolarized white light it reflects left-handed polarized green light as revealed by the non-zero Mueller-matrix elements m14 and m41 in the green spectral region for angles of incidence below about 45º. This is detailed in the graph to the right which shows a spectrum for Mueller-matrix element m41at 20º as well as fitted model data. The model used for the chiral nanostructure is based on a twisted lamella structure, also called Bouligand structure. Given the complexity of the nanostructure, an excellent model fit is achieved. The obtained model parameters are the spectral variation of the refractive index of the birefringent lamellas and the pitch. Limitations and development of the model will be discussed as well as its applicability to more complex beetle cuticle structures.

    Figure. Left: Mueller-matrix data versus wavelength and angle of incidence on Cetonia aurata. Each panel shows mij, where i and j correspond to the row and column, respectively. Right: Experimental and model-generated m41at an angle of incidence of 20º.

     

    In addition, Mueller-matrix spectra are very rich in information about reflection properties and allow parameterization of polarization parameters of the reflected light, e.g. in terms of azimuth and ellipticity of the polarization ellipse and the degree of polarization (see abstract by Järrendahl).

  • 50.
    Arwin, Hans
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Landin, Jan
    Linköping University, Department of Physics, Chemistry and Biology, Ecology. Linköping University, The Institute of Technology.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Chirality-induced polarization effects in the cuticle of scarab beetles: 100 years after Michelson2012In: Philosophical Magazine, ISSN 1478-6435, E-ISSN 1478-6443, Vol. 92, no 12, p. 1583-1599Article in journal (Refereed)
    Abstract [en]

    One hundred years ago Michelson discovered circular polarization in reflection from beetles. Today a novel Mueller-matrix ellipsometry setup allows unprecedented detailed characterization of the beetles polarization properties. A formalism based on elliptical polarization for description of reflection from scarab beetles is here proposed and examples are given on four beetles of different character: Coptomia laevis - a simple dielectric mirror; Cetonia aurata - a left-hand narrow- band elliptical polarizer; Anoplognathus aureus - a broad-band elliptical polarizer; and Chrysina argenteola - a left-hand polarizer for visible light at small angles, whereas for larger angles, red reflected light is right-handed polarized. We confirm the conclusion of previous studies which showed that a detailed quantification of ellipticity and degree of polarization of cuticle reflection can be performed instead of only determining whether reflections are circularly polarized or not. We additionally investigate reflection as a function of incidence angle. This provides much richer information for understanding the behaviour of beetles and for structural analysis.

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