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  • 1.
    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.

  • 2.
    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.

  • 3. Atlasov, K.A.
    et al.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Rudra, A.
    Dwir, B.
    Kapon, E.
    Wavelength and loss splitting in directly coupled photonic-crystal defect microcavities2008In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 16, no 20, p. 16255-16264Article in journal (Refereed)
    Abstract [en]

    Coupling between photonic-crystal defect microcavities is observed to result in a splitting not only of the mode wavelength but also of the modal loss. It is discussed that the characteristics of the loss splitting may have an important impact on the optical energy transfer between the coupled resonators. The loss splitting - given by the imaginary part of the coupling strength - is found to arise from the difference in diffractive outof-plane radiation losses of the symmetric and the antisymmetric modes of the coupled system. An approach to control the splitting via coupling barrier engineering is presented. © 2008 Optical Society of America.

  • 4.
    Atlasow, Kirill A.
    et al.
    Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratory of Physics of Nanostructures, CH-1015 Lausanne, Switzerland.
    Calic, Milan
    Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratory of Physics of Nanostructures, CH-1015 Lausanne, Switzerland.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology. Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratory of Physics of Nanostructures, CH-1015 Lausanne, Switzerland.
    Gallo, Pascal
    Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratory of Physics of Nanostructures, CH-1015 Lausanne, Switzerland.
    Rudra, Alok
    n/Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratory of Physics of Nanostructures, CH-1015 Lausanne, Switzerland.
    Dwir, Benjamin
    Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratory of Physics of Nanostructures, CH-1015 Lausanne, Switzerland.
    Kapon, Eli
    Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratory of Physics of Nanostructures, CH-1015 Lausanne, Switzerland.
    Photonic-crystal microcavity laser with site-controlled quantum-wire active medium2009In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 17, no 20, p. 18178-18183Article in journal (Refereed)
    Abstract [en]

    Site-controlled quantum-wire photonic-crystal microcavity laser is experimentally demonstrated using optical pumping. The single-mode lasing and threshold are established based on the transient laser response, linewidth narrowing, and the details of the non-linear power input-output charateristics. Average-power threshold as low as ~240 nW (absorbed power) and spontaneous emission coupling coefficient β~0.3 are derived.

  • 5.
    Chen, P.Y.
    et al.
    National Nano Device Laboratories, Hsinchu 30078, Taiwan.
    Chen, C.H.
    Department of Computer Science, National Chiao-Tung University, Hsinchu 30050, Taiwan.
    Wang, H.
    Department of Computer Science, National Chiao-Tung University, Hsinchu 30050, Taiwan.
    Tsai, J.H.
    National Nano Device Laboratories, Hsinchu 30078, Taiwan.
    Ni, Wei-Xin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Synthesis design of artificial magnetic metamaterials using a genetic algorithm2008In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 16, no 17, p. 12806-12818Article in journal (Refereed)
    Abstract [en]

    In this article, we present a genetic algorithm (GA) as one branch of artificial intelligence (AI) for the optimization-design of the artificial magnetic metamaterial whose structure is automatically generated by computer through the filling element methodology. A representative design example, metamaterials with permeability of negative unity, is investigated and the optimized structures found by the GA are presented. It is also demonstrated that our approach is effective for the synthesis of functional magnetic and electric metamaterials with optimal structures. This GA-based optimization-design technique shows great versatility and applicability in the design of functional metamaterials. © 2008 Optical Society of America.

  • 6.
    Ghafoor, Naureen
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eriksson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Andrew, Aquila
    SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California, USA.
    Gullikson, Eric
    Center for X-Ray Optics, Lawrence Berkeley National Lab, Berkeley, California, USA.
    Franz, Schäfers
    Institute for Nanometre Optics and Technology Helmholtz Zentrum Berlin für Materialien und Energie, Albert-Einstein-Str. 15, Berlin, Germany.
    Greczynski, Grzegorz
    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.
    Impact of B4C co-sputtering on structure and optical performance of Cr/Sc multilayer X-ray mirrors2017In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 25, no 15, p. 18274-18287Article in journal (Refereed)
    Abstract [en]

    The influence of B4C incorporation during magnetron sputter deposition of Cr/Sc multilayers intended for soft X-ray reflective optics is investigated. Chemical analysis suggests formation of metal: boride and carbide bonds which stabilize an amorphous layer structure, resulting in smoother interfaces and an increased reflectivity. A near-normal incidence reflectivity of 11.7%, corresponding to a 67% increase, is achieved at λ = 3.11 nm upon adding 23 at.% (B + C). The advantage is significant for the multilayer periods larger than 1.8 nm, where amorphization results in smaller interface widths, for example, giving 36% reflectance and 99.89% degree of polarization near Brewster angle for a multilayer polarizer. The modulated ion-energy-assistance during the growth is considered vital to avoid intermixing during the interface formation even when B + C are added.

  • 7.
    Gomez, E. S.
    et al.
    Univ Concepcion, Chile.
    Riquelme, P.
    Univ Concepcion, Chile.
    Solis-Prosser, M. A.
    Univ Concepcion, Chile.
    Gonzalez, P.
    Univ Concepcion, Chile.
    Ortega, E.
    Univ Concepcion, Chile; Austrian Acad Sci, Austria.
    Xavier, Guilherme B
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering. Univ Concepcion, Chile.
    Lima, G.
    Univ Concepcion, Chile; Univ Concepcion, Chile.
    Tunable entanglement distillation of spatially correlated down-converted photons2018In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 26, no 11, p. 13961-13972Article in journal (Refereed)
    Abstract [en]

    We report on a new technique for entanglement distillation of the bipartite continuous variable state of spatially correlated photons generated in the spontaneous parametric down-conversion process ( SPDC), where tunable non-Gaussian operations are implemented and the post-processed entanglement is certified in real-time using a single-photon sensitive electron multiplying CCD (EMCCD) camera. The local operations are performed using non-Gaussian filters modulated into a programmable spatial light modulator and, by using the EMCCD camera for actively recording the probability distributions of the twin-photons, one has fine control of the Schmidt number of the distilled state. We show that even simple non-Gaussian filters can be finely tuned to a similar to 67% net gain of the initial entanglement generated in the SPDC process. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

  • 8.
    Karlsson, Hanna
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Fredriksson, Ingemar
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Larsson, Marcus
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Strömberg, Tomas
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Inverse Monte Carlo for estimation of scattering and absorption in liquid optical phantoms2012In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 20, no 11, p. 12233-12246Article in journal (Refereed)
    Abstract [en]

    A spectroscopic probe with multiple detecting fibers was used for quantifying absorption and scattering in liquid optical phantoms. The phantoms were mixtures of Intralipid and red and blue food dyes. Intensity calibration for the detecting fibers was undertaken using either a microsphere suspension (absolute calibration) or a uniform detector illumination (relative calibration between detectors). Two different scattering phase functions were used in an inverse Monte Carlo algorithm. Data were evaluated for residual spectra (systematic deviations and magnitude) and accuracy in estimation of scattering and absorption. Spectral fitting was improved by allowing for a 10% intensity relaxation in the optimization algorithm. For a multi-detector setup, non-systematic residual spectrum was only found using the more complex Gegenbauer-kernel phase function. However, the choice of phase function did not influence the accuracy in the estimation of absorption and scattering. Similar estimation accuracy as in the multi-detector setup was also obtained using either two relative calibrated detectors or one absolute calibrated detector at a fiber separation of 0.46 mm.

  • 9.
    Lindbergh, Tobias
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Fredriksson, Ingemar
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Larsson, Marcus
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Strömberg, Tomas
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Spectral determination of a two-parametric phase function for polydispersive scattering liquids2009In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 17, no 3, p. 1610-1621Article in journal (Refereed)
    Abstract [en]

    A method for determining a two-parametric Gegenbauer-kernel phase function that accurately describes the diffuse reflectance from a polydispersive scattering media at small source-detector separations (0.23 to 1.2 mm), is presented. The method involves spectral collimated transmission measurements, spatially resolved spectral diffuse reflectance (SRDR) measurements, and inverse Monte Carlo technique. Both absolute calibration (using a monodispersive polystyrene microsphere suspension) and relative calibration (eliminating differences between fibers) of SRDR spectra yielded comparable results. When applied to water dilutions of milk, simulated and measured spectra deviated less than 6.5% and 2.5% for the absolute and relative calibration case, respectively, even for the closest fiber separation. Corresponding values for milk including ink as an absorber, were 13.4% and 7.3%.

  • 10.
    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.

  • 11.
    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.

  • 12.
    Ou, Yiyu
    et al.
    Technical University of Denmark, Lyngby.
    Jokubavicius, Valdas
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Hens, Philip
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kaiser, Michl
    University of Erlangen-Nurnberg, Erlangen, Germany .
    Wellmann, Peter
    University of Erlangen-Nurnberg, Erlangen, Germany.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ou, Haiyan
    Technical University of Denmark, Lyngby.
    Broadband and omnidirectional light harvesting enhancement of fluorescent SiC2012In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 20, no 7, p. 7575-7579Article in journal (Refereed)
    Abstract [en]

    In the present work, antireflective sub-wavelength structures have been fabricated on fluorescent 6H-SiC to enhance the white light extraction efficiency by using the reactive-ion etching method. Broadband and omnidirectional antireflection characteristics show that 6H-SiC with antireflective sub-wavelength structures suppress the average surface reflection significantly from 20.5 % to 1.01 % over a wide spectral range of 390-784 nm. The luminescence intensity of the fluorescent 6H-SiC could be enhanced in the whole emission angle range. It maintains an enhancement larger than 91 % up to the incident angle of 70 degrees, while the largest enhancement of 115.4 % could be obtained at 16 degrees. The antireflective sub-wavelength structures on fluorescent 6H-SiC could also preserve the luminescence spectral profile at a large emission angle by eliminating the Fabry-Perot microcavity interference effect.

  • 13.
    Rejmstad, Peter
    et al.
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Zsigmond, Peter
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Oxygen saturation estimation in brain tissue using diffuse reflectance spectroscopy along stereotactic trajectories2017In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 25, no 7, p. 8192-8201Article in journal (Refereed)
    Abstract [en]

    Diffuse reflectance spectroscopy (DRS) can be used to estimate oxygen saturation (SO2) of hemoglobin and blood fraction (fB) in brain tissue. The aim of the study was to investigate the SO2 and fB in different positions along deep brain stimulation (DBS) trajectories and in specific target regions using DRS and a novel algorithm. DRS measurements were done at 166 well-defined anatomical positions in relation to stereotactic DBS-implantation along 20 trajectories toward 4 DBS targets (STN, Vim, GPi and Zi). The measurements were dived into groups (gray, white and light gray matter) related to anatomical position, and DBS targets, before comparison and statistical analysis. The median SO2 in gray, white and light gray matter were 52%, 24% and 20%, respectively. Median fB in gray matter (3.9%) was different from values in white (1.0%, p < 0.05) and light gray (0.9%, p < 0.001) matter. No significant difference in median SO2 and fB was found between DBS target regions. The novel algorithm allows for quick and reliable estimation of SO2 and fB in human brain tissue.

  • 14. Renhorn, Ingmar G. E.
    et al.
    Boreman, Glenn D.
    Univ Cent Florida, CREOL, Coll Opt & Photon, Orlando, FL 32816 USA .
    Analytical fitting model for rough-surface BRDF2008In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 16, no 17, p. 12892-12898Article in journal (Refereed)
    Abstract [en]

    A physics-based model is developed for rough surface BRDF, taking into account angles of incidence and scattering, effective index, surface autocovariance, and correlation length. Shadowing is introduced on surface correlation length and reflectance. Separate terms are included for surface scatter, bulk scatter and retroreflection. Using the FindFit function in Mathematica, the functional form is fitted to BRDF measurements over a wide range of incident angles. The model has fourteen fitting parameters, once these are fixed, the model accurately describes scattering data over two orders of magnitude in BRDF without further adjustment. The resulting analytical model is convenient for numerical computations. (C) 2008 Optical Society of America.

  • 15.
    Tvingstedt, Kristofer
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Dal Zilio, Simone
    CNR-Istituto Nazionale per la Fisica della Materia, Laboratorio Nazionale TASC Area Science Park - Basovizza S.S.14 I-34012 (TS), Italy.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Tormen , Massimo
    CNR-Istituto Nazionale per la Fisica della Materia, Laboratorio Nazionale TASC Area Science Park - Basovizza S.S.14 I-34012 (TS), Italy.
    Trapping light with micro lenses in thin film organic photovoltaic cells2008In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 16, no 26, p. 21608-21615Article in journal (Refereed)
    Abstract [en]

    We demonstrate a novel light trapping configuration based on an array of micro lenses in conjunction with a self aligned array of micro apertures located in a highly reflecting mirror. When locating the light trapping element, that displays strong directional asymmetric transmission, in front of thin film organic photovoltaic cells, an increase in cell absorption is obtained. By recycling reflected photons that otherwise would be lost, thinner films with more beneficial electrical properties can effectively be deployed. The light trapping element enhances the absorption rate of the solar cell and increases the photocurrent by as much as 25%.

  • 16.
    Valyukh, Sergiy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Simulation of light scattering from exoskeletons of scarab beetles2016In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 24, no 6, p. 5794-5808Article in journal (Refereed)
    Abstract [en]

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

  • 17.
    Valyukh, Sergiy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Chigrinov, V.
    Hong Kong University of Science and Technology, Peoples R China .
    Kwok, H. S.
    Hong Kong University of Science and Technology, Peoples R China .
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    On liquid crystal diffractive optical elements utilizing inhomogeneous alignment2012In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 20, no 14, p. 15209-15221Article in journal (Refereed)
    Abstract [en]

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

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