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  • 1.
    Bakker, Jimmy W.P.
    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.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Filippini, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Computer screen photo-assisted off-null ellipsometry2006In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 45, no 30, p. 7795-7799Article in journal (Refereed)
    Abstract [en]

    The ellipsometric measurement of thickness is demonstrated using a computer screen as a light source and a webcam as a detector, adding imaging off-null ellipsometry to the range of available computer screen photoassisted techniques. The results show good qualitative agreement with a simplified theoretical model and a thickness resolution in the nanometer range is achieved. The presented model can be used to optimize the setup for sensitivity. Since the computer screen serves as a homogeneous large area illumination source, which can be tuned to different intensities for different parts of the sample, a large sensitivity range can be obtained without sacrificing thickness resolution.

  • 2.
    Eriksson, Fredrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Ghafoor, Naureen
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Schäfers, F.
    Gullikson, E. M.
    Aouadi, S.
    Rohde, S.
    Hultman, Lars
    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.
    Atomic scale interface engineering by modulated ion-assisted deposition applied to soft x-ray multilayer optics2008In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 47, no 23, p. 4196-4204Article in journal (Refereed)
    Abstract [en]

    Cr/Sc and Ni/V multilayers, intended as normal incidence soft x-ray mirrors and Brewster angle polarizers, have been synthesized by employing a novel modulated low-energy and high-flux ion assistance as a means of engineering the interfaces between the subnanometer layers on an atomic scale during magnetron sputter deposition. To reduce both roughness and intermixing, the ion energy was modulated within each layer. The flat and abrupt interfaces yielded soft x-ray mirrors with near-normal incidence reflectances of R = 20.7% at the Sc 2p absorption edge and R = 2.7% at the V 2p absorption edge. Multilayers optimized for the Brewster angle showed a reflectance of R = 26.7% and an extinction ratio of Rs/Rp=5450 for Cr/Sc and R = 10% and Rs/Rp=4190 for Ni/V. Transmission electron microscopy investigations showed an amorphous Cr/Sc structure with an accumulating high spatial frequency roughness. For Ni/V the initial growth mode is amorphous and then turns crystalline after ~1/3 of the total thickness, with an accumulating low spatial frequency roughness as a consequence. Elastic recoil detection analyses showed that N was the major impurity in both Cr/Sc and Ni/V with concentrations of 15 at. % and 9 at. %, respectively, but also O (3 at. % and 1.3 at. %) and C (0.5 at. % and 1.9 at. %) were present. Simulations of the possible normal incidence reflective properties in the soft x-ray range of 100-600 eV are given, predicting that reflectivities of more than 31% for Cr/Sc and 5.8% for Ni/V can be achieved if better control of the impurities and the deposition process is employed. The simulations also show that Cr/Sc is a good candidate for mirrors for the photon energies between the absorption edges of B (E = 188 eV) and Sc (E = 398.8 eV).

  • 3.
    Ghafoor, Naureen
    et al.
    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.
    Eriksson, Fredrik
    Department of Astrophysics, Columbia University, New York, New York.
    Schäfers, Franz
    BESSY GmbH, Berlin, Germany.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Interface engineered ultra-short period Cr/Ti multilayers as high reflectance mirrors and polarizers for soft X-rays of lambda=2.74 nm wavelength2006In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 45, no 1, p. 137-143Article in journal (Refereed)
    Abstract [en]

    Cr-Ti multilayers with ultrashort periods of 1.39-2.04 nm have been grown for the first time as highly reflective, soft-x-ray multilayer, near-normal incidence mirrors for transition radiation and Cherenkov radiation x-ray sources based on the Ti-2p absorption edge at E = 452eV (lambda = 2.74 nm). Hard, as well as soft, x-ay reflectivity and transmission electron microscopy were used to characterize the nanostructure of the mirrors. To achieve minimal accumulated roughness, improved interface flatness, and to avoid intermixing at the interfaces, each individual layer was engineered by use of a two-stage ion assistance process during magnetron sputter deposition: The first 0.3 nm of each Ti and Cr layer was grown without ion assistance, and the remaining 0.39-0.72 nm of the layers were grown with high ion-neutral flux ratios Phi˙(PhiTi = 3.3, PhiCr = 2.2) and a low energy Eion (ETi = 23.7 and ECr = 21.2), ion assistance. A maximum soft-x-ray reflectivity of R = 2.1% at near-normal incidence (~78.8°) was achieved for a multilayer mirror containing 100 bilayers with a modulation period of 1.379 nm and a layer thickness ratio of Gamma = 0.5. For a polarizing multilayer mirror with 150 bilayers designed for operation at the Brewster angle, 45°, an extinction ratio, Rs/Rp, of 266 was achieved with an absolute reflectivity of R = 4.3%.

  • 4. Hansson, G
    et al.
    Karlsson, H
    Laurell, F
    Def Res Estab, SE-58111 Linkoping, Sweden Royal Inst Technol, SE-10044 Stockholm, Sweden.
    Unstable resonator optical parametric oscillator based on quasi-phase-matched RbTiOAsO42001In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 40, no 30, p. 5446-5451Article in journal (Refereed)
    Abstract [en]

    We demonstrate improved signal and idler-beam quality of a 3-mm-aperture quasi-phase-matched RbTiOAsO4 optical parametric oscillator through use of a confocal unstable resonator as compared with a plane-parallel resonator. Both oscillators were singly resonant, and the periodically poled RbTiOAsO4 crystal generated a signal at 1.56 mum and an idler at 3.33 mum when pumped at 1.064 mum. We compared the beam quality produced by the 1.2-magnification confocal unstable resonator with the beam quality produced by the plane-parallel resonator by measuring the signal and the idler beam M-2 value. We also investigated the effect of pump-beam intensity distribution by comparing the result of a Gaussian and a top-hat intensity profile pump beam. We generated a signal beam of M-2 approximate to 7 and an idler beam of M-2 approximate to 2.5 through use of an unstable resonator and a Gaussian intensity profile pump beam. This corresponds to an increase of a factor of approximately 2 in beam quality for the signal and a factor of 3 for the idler, compared with the beam quality of the plane-parallel resonator optical parametric oscillator. (C) 2001 Optical Society of America.

  • 5. Hansson, G
    et al.
    Karlsson, H
    Wang, SH
    Def Res Estab, Dept Laser Syst, SE-58111 Linkoping, Sweden Royal Inst Technol, Dept Laser Phys & Quantum Opt, SE-10044 Stockholm, Sweden.
    Laurell, F
    Def Res Estab, Dept Laser Syst, SE-58111 Linkoping, Sweden Royal Inst Technol, Dept Laser Phys & Quantum Opt, SE-10044 Stockholm, Sweden.
    Transmission measurements in KTP and isomorphic compounds2000In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 39, no 27, p. 5058-5069Article in journal (Refereed)
    Abstract [en]

    The optical biaxial nature of crystals in the potassium titanyl phosphate (KTP) family result in anisotropic transmission that depends on the polarization direction of the transmitted radiation with respect to the fundamental crystal axes. Knowledge of the polarization-dependent crystal transmission is important for all wavelength-conversion applications and in particular is the only limitation on possible combinations of wavelengths when one uses the quasi-phase-matching techniques recently developed for the KTP family materials. In this study, polarized transmission spectra of KTiOPO4 (KTP), RbTiOPO4, RbTiOAsO4 (RTA), and KTiOAsO4 were measured over the 0.3-6-mu m wavelength range with a spectrophotometer and a Fourier-transform infrared spectrometer. Seven crystal samples were studied, including four samples of KTP crystals of different origins. Variations in spectral transmission on the short- and long-wavelength edges, as well as visible-wavelength transmission and OH- absorption properties, are presented and discussed. The transmission of one sample of RTP and of RTA was also measured before and after periodic electric field poling. (C) 2000 Optical Society of America OCIS codes: 190.0190, 160.4330, 160.4760, 260.1180, 300.0300, 300.1030.

  • 6.
    Harris, M
    et al.
    Def Evaluat & Res Agcy, Elect Sector, Malvern WR14 3PS, Worcs, England Natl Def Res Estab, Dept Laser Syst, S-58111 Linkoping, Sweden.
    Pearson, GN
    Def Evaluat & Res Agcy, Elect Sector, Malvern WR14 3PS, Worcs, England Natl Def Res Estab, Dept Laser Syst, S-58111 Linkoping, Sweden.
    Ridley, KD
    Def Evaluat & Res Agcy, Elect Sector, Malvern WR14 3PS, Worcs, England Natl Def Res Estab, Dept Laser Syst, S-58111 Linkoping, Sweden.
    Karlsson, CJ
    Olsson, FAA
    Def Evaluat & Res Agcy, Elect Sector, Malvern WR14 3PS, Worcs, England Natl Def Res Estab, Dept Laser Syst, S-58111 Linkoping, Sweden.
    Letalick, D
    Def Evaluat & Res Agcy, Elect Sector, Malvern WR14 3PS, Worcs, England Natl Def Res Estab, Dept Laser Syst, S-58111 Linkoping, Sweden.
    Single-particle laser Doppler anemometry at 1.55 mu m2001In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 40, no 6, p. 969-973Article in journal (Refereed)
    Abstract [en]

    We demonstrate the successful operation of a cw laser Doppler wind sensor at a wavelength of 1.55 mum. At longer ranges (>100 m) the signal conforms closely to complex Gaussian statistics, consistent with the incoherent addition of contributions from a large number of scattering aerosols. As the range is reduced, the probe volume rapidly diminishes and the signal statistics are dramatically modified. At the shortest ranges (<8 m) the signal becomes dominated by short bursts, each originating from a single particle within the measurement volume. These single-particle events can have a very high signal-to-noise ratio (SNR) because (1) the signal becomes concentrated within a small time window and (2) its bandwidth is much reduced compared with multiparticle detection. Examples of wind-signal statistics at different ranges and for a variety of atmospheric backscatter conditions are presented. Results show that single-particle-scattering events play a significant role even to ranges of 50 m, leading to results inconsistent with complex Gaussian statistics. The potential is assessed for a low-power laser Doppler wind sensor that exploits the SNR enhancement obtained with single-particle detection. OCIS codes: 120.0280, 280.3400.

  • 7.
    Hodgkinson, I
    et al.
    Univ Otago, Dept Phys, Dunedin, New Zealand Penn State Univ, Dept Engn Sci & Mech, Computat & Theoret Mat Sci Grp, University Pk, PA 16802 USA Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden.
    Wu, QH
    Univ Otago, Dept Phys, Dunedin, New Zealand Penn State Univ, Dept Engn Sci & Mech, Computat & Theoret Mat Sci Grp, University Pk, PA 16802 USA Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden.
    Knight, B
    Univ Otago, Dept Phys, Dunedin, New Zealand Penn State Univ, Dept Engn Sci & Mech, Computat & Theoret Mat Sci Grp, University Pk, PA 16802 USA Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden.
    Lakhtakia, A
    Univ Otago, Dept Phys, Dunedin, New Zealand Penn State Univ, Dept Engn Sci & Mech, Computat & Theoret Mat Sci Grp, University Pk, PA 16802 USA Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden.
    Robbie, K
    Univ Otago, Dept Phys, Dunedin, New Zealand Penn State Univ, Dept Engn Sci & Mech, Computat & Theoret Mat Sci Grp, University Pk, PA 16802 USA Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden.
    Vacuum deposition of chiral sculptured thin films with high optical activity2000In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 39, no 4, p. 642-649Article in journal (Refereed)
    Abstract [en]

    We present the technique of bideposition to realize thin-film helicoidal bianisotropic mediums (TFHBM's) that exhibit high optical activity. Ne show, by experiment as well as by simulation, that the optical rotation produced by these chiral sculptured. thin films is roughly proportional to the square of the local linear birefringence. Experimental measurements on bideposited TFHBM's of titanium oxide yield a typical value of 5 degrees/mu m for the effective specific rotation in the short-wavelength regime, the corresponding value determined for the standard unideposited TFHBM's is 1 degrees/mu m. Both types of TFHBM's are highly optically active in comparison with quartz, fluorite films, and cholesteric liquid crystals. Bideposited TFHBM's will lend themselves to many different types of optical devices. (C) 2000 Optical Society of America.

  • 8.
    Karlholm, J
    et al.
    Swedish Def Res Agcy, Dept IR Syst, SE-58111 Linkoping, Sweden.
    Renhorn, I
    Swedish Def Res Agcy, Dept IR Syst, SE-58111 Linkoping, Sweden.
    Wavelength band selection method for multispectral target detection2002In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 41, no 32, p. 6786-6795Article in journal (Refereed)
    Abstract [en]

    A framework is proposed for the selection of wavelength bands for multispectral sensors by use of hyperspectral reference data. Using the results from the detection theory we derive a cost function that is minimized by a set of spectral bands optimal in terms of detection performance for discrimination between a class of small rare targets and clutter with known spectral distribution. The method may be used, e.g., in the design of multispectral infrared search and track and electro-optical missile warning sensors, where a low false-alarm rate and a high-detection probability for detection of small targets against a clutter background are of critical importance, but the required high frame rate prevents the use of hyperspectral sensors. (C) 2002 Optical Society of America.

  • 9. Karlsson, CJ
    et al.
    Olsson, FAA
    Natl Def Res Estab, Dept Laser Syst, S-58111 Linkoping, Sweden Def Res & Evaluat Agcy, Malvern WR14 3PS, Worcs, England.
    Letalick, D
    Natl Def Res Estab, Dept Laser Syst, S-58111 Linkoping, Sweden Def Res & Evaluat Agcy, Malvern WR14 3PS, Worcs, England.
    Harris, M
    Natl Def Res Estab, Dept Laser Syst, S-58111 Linkoping, Sweden Def Res & Evaluat Agcy, Malvern WR14 3PS, Worcs, England.
    All-fiber multifunction continuous-wave coherent laser radar at 1.55 mu m for range, speed, vibration, and wind measurements2000In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 39, no 21, p. 3716-3726Article in journal (Refereed)
    Abstract [en]

    The design and performance of a simple, multifunction 1.55-mu m continuous-wave (cw) and frequency-modulated cw coherent laser radar system with an output power of 1 W is presented. The system is based on a semiconductor laser source plus an erbium-doped fiber amplifier, a polarization-independent fiber-optic circulator used as the transmit-receive switch, and digital signal processing. The system is shown to be able to perform wind-speed measurements even in clear atmospheric conditions when the visibility exceeds 40 km. The aerosol measurements indicate the potential to use single-particle detection for wind measurements with enhanced sensitivity. The system can perform range and line-of-sight velocity measurements of hard targets at ranges of the order of several kilometers with a range accuracy of a few meters and a velocity accuracy of 0.1 m/s by use of triangular-wave frequency modulation with compensation of the frequency-modulation response of the semiconductor laser. The system also demonstrates a capability for vibration sensing. (C) 2000 Optical Society of America.

  • 10.
    Larsson, Marcus
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Nilsson, Henrik
    Linköping University, Department of Biomedical Engineering.
    Strömberg, Tomas
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    In vivo determination of local skin optical properties and photon path length by use of spatially resolved diffuse reflectance with applications in laser Doppler flowmetry2003In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 42, no 7-8, p. 124-134Article in journal (Refereed)
    Abstract [en]

    Methods for local photon pathlength and optical properties estimation, based on measured and simulated diffuse reflectance within 2mm from the light source, are proposed and evaluated in vivo on Caucasian human skin. The accuracy of the methods was good (2-7%) for pathlength and reduced scattering but poor for absorption estimation. Reduced scattering and absorption were systematically lower in the fingertip than in the forearm skin (633 nm). A maximum intra-site and inter-individual variation of ~35% in the average photon pathlength was found. The methodology was applied in laser Doppler flowmetry (LDF), where pathlength normalization of the estimated perfusion removed the optical property dependency.

  • 11.
    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.

  • 12.
    Rung, A
    et al.
    Uppsala Univ, Div Solid State Phys, Angstrom Lab, SE-75121 Uppsala, Sweden Swedish Dewf Res Agcy, Dept Funct Mat, SE-58111 Linkoping, Sweden.
    Ribbing, CG
    Uppsala Univ, Div Solid State Phys, Angstrom Lab, SE-75121 Uppsala, Sweden Swedish Dewf Res Agcy, Dept Funct Mat, SE-58111 Linkoping, Sweden.
    Calculated photonic structures for infrared emittance control2002In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 41, no 16, p. 3327-3331Article in journal (Refereed)
    Abstract [en]

    Using an available program package based on the transfer-matrix method, we calculated the photonic band structure for two different structures: a quasi-three-dimensional crystal of square air rods in a high-index matrix and an opal structure of high-index spheres in a matrix of low index, epsilon = 1.5. The high index used is representative of gallium arsenide in the thermal infrared range. The geometric parameters of the rod dimension, sphere radius, and lattice constants were chosen to give total reflectance for normal incidence, i.e., minimum thermal emittance, in either one of the two infrared atmospheric windows. For these four photonic crystals, the bulk reflectance spectra and the wavelength-averaged thermal emittance as a function of crystal thickness were calculated. The results reveal that potentially useful thermal signature suppression is obtained for crystals as thin as 20-50 mum, i.e., comparable with that of a paint layer. (C) 2002 Optical Society of America.

  • 13.
    Steinvall, O
    Def Res Estab, S-58111 Linkoping, Sweden.
    Effects of target shape and reflection on laser radar cross sections2000In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 39, no 24, p. 4381-4391Article in journal (Refereed)
    Abstract [en]

    Laser radar cross sections have been evaluated for a number of ideal targets such as cones, spheres, paraboloids, and cylinders by use of different reflection characteristics. The time-independent cross section is the ratio of the cross section of one of these forms to that of a plate with the same maximum radius. The time-dependent laser radar cross section involves the impulse response from the object shape multiplied by the beam's transverse profile and the surface bidirectional reflection distribution function. It can be clearly seen that knowledge of the combined effect of object shape and reflection characteristics is important for determining the shape and the magnitude of the laser radar return. The results of this study are of interest for many laser radar applications such as ranging, three-dimensional imaging-modeling, tracking, antisensor lasers, and target recognition. (C) 2000 Optical Society of America OCIS codes: 290.1350, 280.3400, 280.3640.

  • 14.
    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

  • 15.
    Valyukh, Sergiy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Slobodyanyuk, Oleksandr
    Taras Shevchenko National University of Kyiv, Ukraine.
    Assessment of minimum permissible geometrical parameters of a near-to-eye display2015In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 54, no 21, p. 6526-6533Article in journal (Refereed)
    Abstract [en]

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

  • 16.
    Wang, Guoliang
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Arwin, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Jansson, Roger
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Optimization of azimuth angle settings in polarizer-compensator-sample-analyzer off-null ellipsometry2003In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 42, no 1, p. 38-44Article in journal (Refereed)
    Abstract [en]

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

  • 17.
    Zeng, Zhenxiang
    et al.
    Shanghai University, Peoples R China.
    Zheng, Huadong
    Shanghai University, Peoples R China; Chinese Minist Educ, Peoples R China.
    Yu, Yingjie
    Shanghai University, Peoples R China.
    Asundi, Anand K.
    Nanyang Technology University, Singapore.
    Valyukh, Sergiy
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Full-color holographic display with increased-viewing-angle2017In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 56, no 13, p. F112-F120Article in journal (Refereed)
    Abstract [en]

    Among the important features of holographic displays are the wide viewing angles and the full color of the reconstructed images. The present work focuses on achievement of both features. We propose an increased-viewing-angle full-color holographic display using two tiled phase-only spatial light modulators (SLMs), a 4f concave mirrors system, and a temporal-spatial multiplexing method. The 4f optical system consists of two concave mirrors and serves to increase the viewing angle. A temporal-spatial multiplexing synchronization control (TSMSC) method is developed to achieve a full-color image and to remove the color crosstalk of the image. We calculate RGB phase-only holograms of a computer-generated color pyramid by using a slice-based Fresnel diffraction algorithm. The experimental results indicate that the proposed display system is feasible to reconstruct a full-color holographic 3D image with a viewing angle of 12.8 degrees, which is about 3.8 times wider than the viewing angle formed by a single SLM. (C) 2017 Optical Society of America

  • 18.
    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.

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