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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.
    Kuo, Yu-Hung
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Serban, Alexandra
    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.
    Hultman, Lars
    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.
    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.
    Influence of InAiN Nanospiral Structures on the Behavior of Reflected Light Polarization2018In: NANOMATERIALS, ISSN 2079-4991, Vol. 8, no 3, article id 157Article in journal (Refereed)
    Abstract [en]

    The influence of structural configurations of indium aluminum nitride (InA1N) nanospirals, grown by reactive magnetron sputter epitaxy, on the transformation of light polarization are investigated in terms of varying structural chirality, growth temperatures, titanium nitride (TiN) seed (buffer) layer thickness, nanospiral thickness, and pitch. The handedness of reflected circularly polarized light in the ultraviolet-visible region corresponding to the chirality of nanospirals is demonstrated. A high degree of circular polarization (P-c) value of 0.75 is obtained from a sample consisting of 1.2 mu m InA1N nanospirals grown at 650 degrees C. A film-like structure is formed at temperatures lower than 450 degrees C. At growth temperatures higher than 750 degrees C, less than 0.1 In-content is incorporated into the InA1N nanospirals. Both cases reveal very low P-c-A red shift of wavelength at P-c peak is found with increasing nanospiral pitch in the range of 200-300 nm. The P-c decreases to 0.37 for two-turn nanospirals with total length of 0.7 mu m, attributed to insufficient constructive interference. A branch-like structure appears on the surface when the nanospirals are grown longer than 1.2 mu m, which yields a low P-c around 0.5, caused by the excessive scattering of incident light.

  • 5.
    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.

  • 6.
    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.

  • 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.
    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.

  • 9.
    Valyukh, Sergiy
    et al.
    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.
    Modeling of light interaction with exoskeletons of scarab beetles2017In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 56, no 9, p. 2510-2516Article in journal (Refereed)
    Abstract [en]

    Some beetles of the family Scarabaeidae produce brilliant metallic-looking colors by their pure dielectric exoskeletons and reflect light with a high degree of circular polarization. In the present work, we discuss three models for simultaneously describing scattering, spectral, and polarization characteristics of scarab beetles. Each model consists of three slabs: an outer thin epicuticle, an exocuticle having a helicoidal structure, and a thick uniform slightly absorbing endocuticle. Scattering features are defined by rough interfaces of the epicuticle and/or nonuniformities of the exocuticle. As an example, a slightly modified model of an earlier study of Chrysina aurata is considered. The modification is aimed at including surface and volume nonuniformities that affect not only spectral and polarization properties but also scattering. Another example of using the proposed models is based on the analysis of image formations of a specimen of the species Mimela chinensis, which was studied in a polarizing microscope at different magnifications. The results show that the proposed models can be applied for explanation of light interaction with the exoskeletons of scarab beetles. (C) 2017 Optical Society of America

  • 10.
    Kroon, Lars
    et al.
    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.
    Neutral inclusions for diffusive acoustic fields2017In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 295, p. 80-89Article in journal (Refereed)
    Abstract [en]

    We predict scattering cancellation in diffusive transport of acoustics waves propagating through multiple scattering media in the stationary limit. This would enable sensing of diffusive sound without disrupting the exterior acoustic field. We present design schemes for making spherical or cylindrical core-shell structures with multiple layers, characterized by homogenous and isotropic diffusion coefficients, neutral to an arbitrary applied multipole field. The double-layered sphere is found to support transparency to two concurrent multipole fields and unique cloaking solutions of arbitrary multipole order. One extra degree of freedom is provided by every layer added to the core-shell structure which may be exploited with our iterative formula for effective diffusivity for cloaking of additional field terms. From this we pass over to the long wavelength limit of ballistic sound and provide formulas for effective mass densities of multi-layered structures in spherical and cylindrical geometries with respect to multipole pressure fields. (C) 2017 Elsevier Ltd. All rights reserved.

  • 11.
    Kroon, Lars
    et al.
    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.
    Neutral shielding and cloaking of magnetic fields using isotropic media2017In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 29, no 3Article in journal (Refereed)
    Abstract [en]

    A method for designing magnetic shields that do not perturb applied multipole fields in the static regime is developed. Cylindrical core-shell structures with two layers characterized by homogeneous isotropic permeabilities are found to support neutral shielding of multipole fields and unique cloaking solutions of arbitrary multipole order. An extra degree of freedom is provided by every layer added to the structure which may be exploited with an effective design formula for cloaking of additional field terms. The theory is illustrated with numerical simulations.

  • 12.
    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.

  • 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.
    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.

  • 15.
    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

  • 16.
    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

  • 17.
    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.

  • 18.
    Hsiao, Ching-Lien
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Sandström, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Persson, Per O. Å.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Valyukh, Sergiy
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Curved-Lattice Epitaxial Growth of InxAl1-xN Nanospirals with Tailored Chirality2015In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 15, no 1, p. 294-300Article in journal (Refereed)
    Abstract [en]

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

  • 19.
    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

  • 20.
    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.

  • 21.
    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.

  • 22.
    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

  • 23.
    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.

  • 24.
    Arwin, Hans
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Garcia-Caurel, Enric
    CNRS 91128 Palaiseau, France.
    de Martino, Antonello
    CNRS 91128 Palaiseau, FranceCNRS 91128 Palaiseau, France.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Ossikovski, Razvigor
    CNRS 91128 Palaiseau, France.
    Sum decomposition of Mueller matrices from beetle cuticles2015Conference paper (Other academic)
    Abstract [en]

    Spectral Mueller matrices are very rich in information about physical properties of a sample. We have recently shown that polarizing properties like ellipticity and degree of polarization can be extracted from a Mueller matrix measured on a beetle cuticle (exoskeleton). Mueller matrices can also be used in regression analysis to model nanostructures in cuticles. Here we present the use of sum decomposition of Mueller matrices from these depolarizing biological reflectors to explore the fundamental character of these reflectors. The objective is to decompose a Mueller matrix into well- defined ideal non-depolarizing matrices corresponding to mirrors, circular polarizers, halfwave retarders etc.Generally it is possible to decompose a measured depolarizing Mueller matrix M into four (or fewer) non-depolarizing matrices according to M=λ1M1+λ2M2+λ3M3+λ4M4, where λ1, λ2, λ3 and λ4 are eigenvalues of the covariance matrix of M. Two strategies for decomposition will be discussed. A Cloude decomposition will provide the eigenvalues and also the Mi’s although the latter will contain severe noise in some spectral regions. However, a major advantage with the Cloude decomposition is that the number of nonzero eigenvalues is directly obtained, i.e. the number of contributing Mi matrices. In an alternative decomposition, the Mi’s are assumed and the eigenvalues are found by regression analysis based on M. In the case with two non-zero eigenvalues we define a model Mueller matrix MD=αRM1+βRM2 with αR+βR=1. With αR as adjustable parameter, the Frobenius norm ||M-MD|| is minimized for each wavelength in the spectral range of M. For more complex structures, the regression can be extended by adding more matrices up to a total of four. Advantages with a regression approach are its simplicity and stability compared to a Cloude decomposition.Mueller-matrix spectra of beetle cuticles are recorded with a dual rotating compensator ellipsometer in the spectral range 400 – 900 nm at angles of incidence in the range 20 - 75°. The application of decomposition on biological reflectors is demonstrated on M measured on the beetle Cetonia aurata, which represents a narrow-band chiral Bragg reflector with two non-zero eigenvalues. A decomposition in an ideal mirror and a circular polarizer is feasible. In another example, the broad-band and gold-colored beetle Chrysina argenteola, we show that more than two eigenvalues can be nonzero, especially at oblique incidence, and additional matrices are involved.

  • 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.
    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.

  • 27.
    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°.

  • 28.
    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.

  • 29.
    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.

  • 30.
    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.

  • 31.
    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.

  • 32.
    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.

  • 33.
    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.

  • 34.
    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.

  • 35.
    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.

  • 36.
    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.

  • 37.
    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.

  • 38.
    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.

  • 39.
    Hsiao, Ching-Lien
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Sandström, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Valyukh, Sergiy
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Persson, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Curved-lattice epitaxial growth of chiral AlInN twisted nanorods for optical applications2012Manuscript (preprint) (Other academic)
    Abstract [en]

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

  • 40.
    Mendoza-Galván, Arturo
    et al.
    Cinvestav-IPN, Unidad Querétaro, Querétaro, Mexico .
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Dmitriev, Alexander
    Department of Applied Physics, Chalmers University of Technology, Göteborg, Sweden.
    Pakizeh, T.
    Faculty of Electrical and Computer Engineering, K. N. Toosi University of Technology, Tehran, Iran.
    Käll, Mikael
    Department of Applied Physics, Chalmers University of Technology, Göteborg, Sweden.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Fano interference in supported gold nanosandwiches with weakly coupled nanodisks2012In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 20, no 28, p. 29646-29658Article in journal (Refereed)
    Abstract [en]

    We studied the far-field optical response of supported gold-silica-gold nanosandwiches using spectroscopic ellipsometry, reflectance and transmittance measurements. Although transmittance data clearly shows that the gold nanodisks in the sandwich structure interact very weakly, oblique reflectance spectra of s- and p-polarized light show clearly asymmetric line-shapes of the Fano type. However, all experimental results are very well described by modeling the gold nanodisks as oblate spheroids and by employing a 2 × 2 scattering matrix formulation of the Fresnel coefficients provided by an island film theory. In particular, the Fano asymmetry can be explained in terms of interference between the scattered waves from the decoupled nanodisks in the spectral range limited by their respective plasmon resonances. We also show that the reflectance and ellipsometry spectra can be described by a three-layer system with uniaxial effective dielectric functions.

  • 41.
    Valyukh, Sergiy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Light Scattering and Colour Generation in exoskeletons of Jewelled Beetle2012In: Photonics Global Conference, 2012Conference paper (Other academic)
  • 42.
    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.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. 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.
    Gustafson, Johan
    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, 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.
    Åkerlind, Christina
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Polarization effects in reflection from the cuticle of scarab beetles studied by spectroscopic Mueller-matrix ellipsometry2012In: AES 2012, Advanced Electromagnetics Symposium, 2012Conference paper (Other academic)
    Abstract [en]

    Polarization effects in reflection from the cuticle of scarab beetles studied by spectroscopic Mueller-matrix ellipsometry

     

    H. Arwin*, T. Berlind, J. Birch, L. Fernandez Del Rio, J. Gustafson, J. Landin,

    R. Magnusson, C. Åkerlind, and K. Järrendahl

    Department of Physics, Chemistry and Biology, Linköping University, Sweden

    *corresponding author: han@ifm.liu.se

     

    Abstract- Many scarab beetles exhibit structural colors and complex polarization phenomena in reflection. These effects are characterized with spectroscopic Mueller-matrix ellipsometry in our work. The polarization ellipse of reflected light as well as the degree of polarization is presented including variations with angle of incidence and wavelength. Emphasis is on beetles showing chiral effects and structural modeling of cuticle nanostructure is discussed.

     

    Background Since one hundred years it is known that some scarab beetles reflect elliptically polarized light as demonstrated by Michelson for the beetle Chrysina resplendens [1]. The handedness of the polarization is in a majority of the cases left-handed but also right-handed polarization has been found [2,3]. The ellipticity varies with wavelength and viewing angle but can be close to +1 or -1 (right or left circular polarization, respectively) and in addition these beetles may exhibit beautiful structural colors. The polarization and color effects are generated in the outer part of the exoskeleton, the cuticle. These natural photonic structures are often multifunctional and play important roles for survival of beetles, e.g. for hiding from or scaring predators, for intraspecies communication, etc. [4]. However, such structures may find use in many commercial applications and a major motivation for detailed studies of natural photonic structures is that they inspire to biomimetic applications [5,6].

    Approach Our objective is to use spectral Mueller-matrix data on scarab beetles to parameterize reflection properties in terms of polarization parameters and degree of polarization. The studied beetles all are phytophagous and include species from the Cetoniinae subfamily (e.g. Cetonia aurata and Coptomia laevis,), the Rutelinae subfamily (e.g. Chrysina argenteola and Chrysina resplendens) and the Melolonthinae subfamily (Cyphochilus insulanus). Furthermore, structural modeling is presented on Cetonia aurata and a few more beetles to demonstrate that structural parameters can be extracted by advanced modeling of Mueller-matrix data.

    Experimental A dual rotating compensator ellipsometer (RC2, J. A. Woollam Co., Inc.) is used to record all 16 Mueller-matrix elements mij (i,j=1..4) in the spectral range 300 – 900 nm at angles of incidence in the range 20-70º. The elements are normalized to m11 and thus have values between -1 and +1. 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 50-100 mm. The software CompleteEASE (J. A. Woollam Co., Inc.) is used for analysis.

    Results and discussion As an example, Fig. 1 shows contour plots of Mueller-matrix data measured on Cetonia aurata. 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 clearly seen in the graph to the right in Fig. 1 which shows a spectrum for Mueller-matrix element m41at 20º as well as fitted model data. A model based on a twisted lamella structure, also called Bouligand structure, is used to model the chiral nanostructure [4]. 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. The model also includes a dielectric surface layer.

     

     

     

    Fig.1. Left: Mueller-matrix data on Cetonia aurata. Each contour plot shows mij, where i and j correspond to the row and column, respectively. m11 =1 and is not shown but is replaced with a photo of the beetle. Right: Experimental and model-generated Mueller-matrix element m41at an angle of incidence of 20º.

     

    From the Mueller-matrix data one can also determine so called derived parameters including azimuth and ellipticity of the polarization ellipse and the degree of polarization. The variations of these parameters with angle of incidence are presented for a selection of scarab beetles. Examples of both left-handed and right-handed polarization effects are shown and the importance of degree of polarization will be discussed.

    Concluding remarks Mueller-matrix spectra at oblique incidence are very rich in information about reflection properties and allows parameterization of polarization parameters of the reflected light. Both left-handed and right-handed reflected light is found in scarab beetles. Mueller-matrix data can also be used for a detailed modeling of the nanostructure of the cuticle of beetles.

    AcknowledgementsFinancial support was obtained from the Knut and Alice Wallenberg foundation and the Swedish Research Council. The Museum of Natural History in Stockholm, the National Museum of Natural Science in Madrid, the Berlin Museum of Natural History and the Natural History Museum in London are acknowledged for loan of beetles.

     

    REFERENCES

    1. Michelson, A. A. “On Metallic Colouring in Birds and Insects,” Phil. Mag., 21, 554-567, 1911.
    2. Goldstein, D. H. “Polarization properties of Scarabaeidae,” Appl. Opt., 45, 7944-7950, 2006.
    3. Hodgkinson, I., Lowrey, S., Bourke, L., Parker, A. and McCall, M. W. “Mueller-matrix characterization of beetle cuticle polarized and unpolarized reflections from representative architectures,” Appl. Opt., 49, 4558-4567, 2010.
    4. Vukusic, P. and Sambles, J. R. “Photonic structures in biology,” Nature, 424, 852-855, 2003.
    5. Lenau, T. and Barfoed, M. “Colours and Metallic Sheen in Beetle Shells - A Biomimetic Search for Material Structuring Principles Causing Light Interference,” Adv. Eng. Mat., 10, 299-314. 2008.
    6. Parker, A. R. and Townley, H. E “Biomimetics of photonic nanostructures,” Nature Nanotech., 2, 347-351, 2007.
  • 43.
    Järrendahl, Kenneth
    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.
    Magnusson, Roger
    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.
    Sandström, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Berlind, Torun
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Gustafson, Johan L.I.
    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, Biology. Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Polarization of Light Reflected from Chiral Structures - Calculations Compared with Mueller Matrix Ellipsometry Measurements on Natural and Synthetic Samples2012Conference paper (Other academic)
    Abstract [en]

    The Mueller matrix elements mij representing the polarization response from a nanostructured materialis determined by the constituent materials optical properties and the superstructure. Here, we investigate how chiral structures in form of helicoidally stacked uniaxial layers determine mij as a functionof polarization state, wavelength, incidence angle and azimuthal angle of the incoming light. The studied parameters include the layer materials ordinary/extraordinary optical properties, Euler angle values, and layer thickness as well as the thickness and pitch of the helicoidal superstructure. Sub- and superstructure inhomogeneity is also introduced. From the Fresnel-based calculations, mij aswell as the degree of polarization, ellipticity and azimuth of the polarization ellipse are obtained and presented as contour and trace plots to give a complete view of the polarization behavior. The results from the calculations are compared with Mueller matrix spectroscopic ellipsometry measurements of both natural and synthesized helicoidal structures. The measurements were performed with a dualrotating compensator system (RC2, J.A. Woollam Co., Inc.) for wavelengths in the range from 245 to 1000 nm and incident angles from 20 to 75°. For some measurements the azimuthal angle of the incident light was varied. The investigated natural chiral structures were exoskeletons from several beetles in the scarab subfamilies Cetoniinae and Rutelinae. As predicted from the calculations it isobserved that the reflection from these beetles can have a high degree of polarization and high ellipticity (near-circular polarization). Both left- and right-polarization was observed. The synthesized structures are helicoidal nanorods of Al1−xInxN grown on sapphire substrates with metal-nitride seedlayers using UHV magnetron sputtering. Due to an internal composition gradient (a variation of x) in the crystalline structure, the nanorods will tilt away from the substrate normal. Helicoidal structures can thus be obtained by rotating the substrate around its normal during deposition. Samples with different pitch and layer thickness with right-handed as well as left-handed chirality were grown. Also for these structures both left and right near-circular polarized light is observed. By combining calculations, ellipsometry measurements and scanning electron microscopy characterization we get agood input to build layered models of the natural and synthetic samples. After regression fitting agood agreement between calculated and measured optical data were obtained.

  • 44.
    Muñoz-Pineda, Eloy Guadalupe
    et al.
    Cinvestav-Unidad Queretaro, Mexico.
    Mendoza-Galván, Arturo
    Cinvestav-Queretaro, Mexico.
    Mauricio-Sánchez, Reina Araceli
    Landin, Jan
    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.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Polarization properties and structural color of the scarab beetle Cotinis mutabilis (Mayatl)2012Conference paper (Other academic)
    Abstract [en]

    Nature offers a plethora of possibilities for optical biomimetics. Some birds, butterflies, insects and other creatures exhibit brilliant colors as result of diverse optical phenomena produced by micro- and nanostructures at the near surface. Particularly, the shiny metallic colors reflected by the exoskeleton (the so called cuticle) of some beetles show elliptical polarization properties; most commonly of the left-handed type but also the right-handed type has been found [1]. These color and polarization properties have been related to a twisted plywood or Bouligand structure which is comprised by the clustering of chitin nanofibrils wrapped by proteins in a planar woven.

    In this work we report the polarization properties of light reflected from the scarab beetle Cotinis mutabilis (Gory and Percheron 1833) and the microstructure of its cuticle. This species is found in Mexico and the southwestern part of the United States. The specimen under study was collected at the facilities of Cinvestav in Querétaro, Mexico where it is known as mayate (Mayatl in Náuhtl, the language of Aztecs). The Mayatl presents a green mate color in its dorsal side with red-orange stripes in the elytra. On the other hand, the abdominal side shows a shiny green metallic color which is subject of the present study. The polarization properties are investigated by the complete Mueller matrix (M) measured with a dual rotating compensator ellipsometer (J. A. Woollam Co., Inc.) at angles of incidence of 20-75° and wavelength range of 250-1000 nm. In particular, the elements m41 and m14 of M show that green left-handed polarized light is reflected when the beetle is illuminated at near-normal angles of incidence with unpolarized white light. As the angle of incidence increases the maximum of light reflected is blue-shifted. The degree of polarization, ellipticity, and azimuth calculated with relationships between mj1 elements provide a full description of the polarization state of light reflected from the beetle’s cuticle for incident un-polarized light. Scanning electron microscopy images of the cuticle reveal that the epicuticle and exocuticle comprise a (hard) layer ca. 15 μm thick. Two regions can be differentiated in the exocuticle: the outer exocuticle without any clear structure and the inner exocuticle where a clear multilayer structure is observed. Beneath the inner exocuticle is the endocuticle which is comprised by unidirectional layers of microfibrils alternate with layers running at nearly right angles to each other in a pseudo-orthogonal arrangement. The cuticle also was imaged with a microscope coupled to a FTIR system allowing further identification of bands due to chitin.

  • 45.
    Valyukh, Sergiy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Åkerlind, Christina
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Simulation of light scattering from biological helicoidal structures2012In: 7th Workshop Ellipsometry, 2012, p. 90-Conference paper (Other academic)
  • 46.
    Akerlind, C
    et al.
    Swedish Defence Research Agency.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Jakobsson, Fredrik
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Kariis, H
    Swedish Defence Research Agency.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Optical properties and switching of a Rose Bengal derivative: A spectroscopic ellipsometry study2011In: THIN SOLID FILMS, ISSN 0040-6090, Vol. 519, no 11, p. 3582-3586Article in journal (Refereed)
    Abstract [en]

    Optical properties in terms of the complex-valued dielectric function were determined for spin-coated films of a Rose Bengal derivative using variable angle of incidence spectroscopic ellipsometry in the visible and infrared wavelength regions. In addition, the thickness and roughness of the films were determined and related to the solution concentration of Rose Bengal. Switching between two different oxidation states of the Rose Bengal derivative was investigated. The two states were chemically induced by exposure to vapors of hydrochloric acid and ammonia, respectively. A substantial and reversible change of the optical properties of the films was observed.

  • 47.
    Mendoza-Galvan, A.
    et al.
    Cinvestav-IPN, Unidad Querétaro, Querétaro, Mexico.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Dmitriev, A.
    Department of Applied Physics, Chalmers University of Technology, Göteborg.
    Pakizeh, T.
    Faculty of Electrical and Computer Engineering, K. N. Toosi University of Technology, Tehran, Iran.
    Käll, M.
    Department of Applied Physics, Chalmers University of Technology, Göteborg.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Optical response of supported gold nanodisks2011In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 19, no 13, p. 12093-12107Article in journal (Refereed)
    Abstract [en]

    It is shown that the ellipsometric spectra of short range ordered planar arrays of gold nanodisks supported on glass substrates can be described by modeling the nanostructured arrays as uniaxial homogeneous layers with dielectric functions of the Lorentz type. However, appreciable deviations from experimental data are observed in calculated spectra of irradiance measurements. A qualitative and quantitative description of all measured spectra is obtained with a uniaxial effective medium dielectric function in which the nanodisks are modeled as oblate spheroids. Dynamic depolarization factors in the long-wavelength approximation and interaction with the substrate are considered. Similar results are obtained calculating the optical spectra using the island-film theory. Nevertheless, a small in-plane anisotropy and quadrupolar coupling effects reveal a very complex optical response of the nanostructured arrays.

  • 48.
    Mendoza-Galvan, Arturo
    et al.
    Cinvestav-Querétaro, Libramiento Norponiente.
    Rybka, M
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, 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.
    Magnuson, Martin
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Barsoum, Michel
    Drexel University.
    Spectroscopic ellipsometry study on the dielectric function of bulk Ti2AlN,Ti2AlC, Nb2AlC, (Ti0.5,Nb0.5)2AlC, and Ti3GeC2 MAX-phases2011In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 109, p. 013530-Article in journal (Refereed)
    Abstract [en]

    The averaged complex dielectric function =2+ /3 of polycrystalline Ti2AlN, Ti2AlC,Nb2AlC, Ti0.5,Nb0.52AlC, and Ti3GeC2 was determined by spectroscopic ellipsometry coveringthe mid infrared to the ultraviolet spectral range. The dielectric functions and correspond tothe perpendicular and parallel dielectric tensor components relative to the crystallographic c-axis ofthese hexagonal compounds. The optical response is represented by a dispersion model with Drude–Lorentz and critical point contributions. In the low energy range the electrical resistivity is obtainedfrom the Drude term and ranges from 0.48 m for Ti3GeC2 to 1.59 m for Ti0.5,Nb0.52AlC.Furthermore, several compositional dependent interband electronic transitions can be identified. Forthe most important ones, Im shows maxima at: 0.78, 1.23, 2.04, 2.48, and 3.78 eV for Ti2AlN;0.38, 1.8, 2.6, and 3.64 eV for Ti2AlC; 0.3, 0.92, and 2.8 eV in Nb2AlC; 0.45, 0.98, and 2.58 eV inTi0.5,Nb0.52AlC; and 0.8, 1.85, 2.25, and 3.02 eV in Ti3GeC2.

  • 49.
    Arwin, Hans
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Mendoza-Galván, A.
    Cinvestav, Querétaro, Mexico.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Dmitriev, A.
    Chalmers University of Technology, Department of Applied Physics.
    Pakizeh, T.
    Chalmers University of Technology, Department of Applied Physics.
    Käll, M.
    Chalmers University of Technology, Department of Applied Physics.
    Artificial Magnetism in Gold-Silica-Gold Metamaterials - an ellipsometric Study2009Conference paper (Other academic)
  • 50.
    Arwin, Hans
    et al.
    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.
    Landin, Jan
    Linköping University, Department of Physics, Chemistry and Biology, Ecology . Linköping University, The Institute of Technology.
    Boulenquez, J.
    INSP, UMR 7588, CNRS, Paris 6 and Paris 7 universities, Paris, France.
    Berthier, S.
    INSP, UMR 7588, CNRS, Paris 6 and Paris 7 universities, Paris, France.
    Ellipsometry applied to natural biophotonic structures: a review2009Conference paper (Refereed)
12 1 - 50 of 87
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