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  • 1.
    Abramson, Nils H.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Elliptic visualizing optical resolution and kinetic energy2017In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 56, no 5, p. 1413-1416Article in journal (Refereed)
    Abstract [en]

    Diffraction limited resolution as introduced by Abbe is well established, but interference limited resolution was not well known until holographic interferometry was introduced. The holodiagram is used to simplify holography and in a new way visualize the distribution, ratio, and relation among resolutions of different optical techniques, including relativistic phenomena. Resolution, when measured by optical methods based on the number of wavelengths of light, is defined in the following as the minimum distance between resolvable points, or the largest object needed to be resolved. Everywhere in the diagram this resolution is represented by two orthogonal diagonals of rhombs.

  • 2.
    Abramson, Nils H.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Metrology and Optics.
    Holodiagram: elliptic visualizing interferometry, relativity, and light-in-flight2014In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 53, no 11, p. 2398-2404Article in journal (Refereed)
    Abstract [en]

    In holographic interferometry, there is usually a static distance separating the point of illumination and the point of observation. In Special Relativity, this separation is dynamic and is caused by the velocity of the observer. The corrections needed to compensate for these separations are similar in the two fields. We use the ellipsoids of the holodiagram for measurement and in a graphic way to explain and evaluate optical resolution, gated viewing, radar, holography, three-dimensional interferometry, Special Relativity, and light-in-flight recordings. Lorentz contraction together with time dilation is explained as the result of the eccentricity of the measuring ellipsoid, caused by its velocity. The extremely thin ellipsoid of the very first light appears as a beam aimed directly at the observer, which might explain the wave or ray duality of light and entanglement. Finally, we introduce the concept of ellipsoids of observation.

  • 3.
    Abramson, Nils H.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Metrology and Optics.
    Optical resolution and the duality of light2008In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 47, no 19, p. D1-D5Article in journal (Refereed)
    Abstract [en]

    For 15 years, lensless microscopes have been constructed based on the use of holography, a digital CCD detector, and a computer for image reconstruction by use of, e.g., Fourier transformation. Thus, no lens is involved and therefore the conventional resolution limit of half the wavelength no longer applies. Instead of being limited by the wavelength, the resolution is in this case limited by how exact one can measure the phases of the light. It is remarkable that the interference-limited resolution is approximately 0.01X, whereas the diffraction-limited resolution is only of the order of 0.5X. It is my hope that by combining these two techniques it will be possible to increase the magnification in optical systems by at least an order of magnitude. The calculations at so indicate that information does not necessarily decrease with distance.

  • 4.
    Amer, Eynas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gren, Per
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Edenharder, Stefan
    Institut für Technische Optik, Universität Stuttgart.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Stimulated Raman scattering holography for time-resolved imaging of methane gas2016In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 55, no 13, p. 3429-3434Article in journal (Refereed)
    Abstract [en]

    In this paper, pulsed digital holographic detection is coupled to the stimulated Raman scattering (SRS) process for imaging gases. A Q-switched Nd-YAG laser (532 nm) has been used to pump methane gas (CH4) at pressures up to 12 bars. The frequency-tripled (355 nm) beam from the same laser was used to pump an optical parametric oscillator (OPO). The Stokes beam (from the OPO) has been tuned to 629.93 nm so that the frequency difference between the pump (532 nm) and the Stokes beams fits a Raman active vibrational mode of the methane molecule (2922 cm(-1)). The pump beam has been spatially modulated with fringes produced in a Michelson interferometer. The pump and the Stokes beams were overlapped in time, space, and polarization on the gas molecules, resulting in a stimulated Raman gain of the Stokes beam and a corresponding loss of the pump beam through the SRS process. The resulting gain of the Stokes beam has been detected using pulsed digital holography by blending it with a reference beam on the detector. Two holograms of the Stokes beam, without and with the pump beam fringes present, were recorded. Intensity maps calculated from the recorded digital holograms showed amplification of the Stokes beam at the position of overlap with the pump beam fringes and the gas molecules. The gain of the Stokes beam has been separated from the background in the Fourier domain. A gain of about 4.5% at a pump beam average intensity of 4 MW/cm(2) and a Stokes beam intensity of 0.16 MW/cm(2) have been recorded at a gas pressure of 12 bars. The gain decreased linearly with decreasing gas pressure. The results show that SRS holography is a promising technique to pinpoint a specific species and record its spatial and temporal distribution

  • 5.
    Amer, Eynas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gren, Per
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Single-shot polarization digital holography for recording stimulated Raman scattering signal for time-resolved measurement of gaseous species2017In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 56, no 36, p. 10016-10023Article in journal (Refereed)
    Abstract [en]

    The stimulated Raman scattering (SRS) process is sensitive to the relation between the polarization direction of the two laser beams (the pump and the Stokes) that generate it. In this paper, we made use of the polarization sensitivity of the SRS process and used polarization-resolved pulsed digital holography to record the signal from one single-shot hologram. The pump beam polarization was kept vertical, while the Stokes beam polarization was 45 deg. The two polarization components of the Stokes beam were recorded in a single hologram by blending the Stokes beam with two reference beams with orthogonal polarization on the detector. The two components of the Stokes beam were separated in the Fourier domain, and the corresponding intensity maps were calculated. The vertically polarized component of the Stokes beam was amplified due to the SRS process, while the horizontal component experienced no gain. The difference between the vertically and horizontally polarized intensity maps, respectively, was calculated and Fourier transformed to separate the gain signal in the spatial frequency domain. The method was demonstrated on methane (CH4) gas at a pressure of 12 bars. Results show that SRS polarization holography is a promising technique for recording the SRS signal from one single-shot hologram for time-resolved monitoring of specific species. 

  • 6.
    Amer, Eynas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gren, Per
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Stimulated Raman scattering signals recorded by the use of an optical imaging technique2015In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 54, no 20, p. 6377-6385Article in journal (Refereed)
    Abstract [en]

    In this paper, stimulated Raman scattering (SRS) signals have been recorded by an optical imaging technique that is based on spatial modulation. A frequency doubled Q-switched Nd:YAG laser (532 nm) was used to pump a polymethyl methacrylate (PMMA) target. The frequency tripled (355 nm) beam from the same laser was used to pump an optical parametric oscillator (OPO). The Stokes beam (from the OPO) was tuned to 631.27 nm so that the frequency difference between the pump and the Stokes beams fit the Raman active vibrational mode of the PMMA molecule (2956 cm(-1)). The pump beam has been spatially modulated with fringes produced in a Michelson interferometer. The pump and the Stokes beams were overlapped on the target resulting in a gain of the Stokes beam of roughly 2.5% and a corresponding loss of the pump beam through the SRS process. To demodulate the SRS signal, two images of the Stokes beam without and with the pump beam fringes present were recorded. The difference between these two images was calculated and Fourier transformed. Then, the gain of the Stokes beam was separated from the background in the Fourier domain. The results show that spatial modulation of the pump beam is a promising method to separate the weak SRS signal from the background.

  • 7. Andersson, Angelica
    et al.
    Mohan, N. Krishna
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Molin, Nils-Erik
    TV shearography: quantitative measurement of shear-magnitude fields by use of digital speckle photography2000In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 39, no 16, p. 2565-2568Article in journal (Refereed)
    Abstract [en]

    Digital speckle photography combined with TV shearography is developed for precise measurement of the magnitude of the shear field in a linear shear configuration. As an application the method is implemented to determine the slope-change variations of a three-dimensional object with TV shearography in which the shear magnitude is obtained with the digital speckle photography technique

  • 8.
    Andersson, Angelica
    et al.
    Luleå tekniska universitet.
    Runnemalm, Anna
    Luleå tekniska universitet.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Digital speckle pattern interferometry: fringe retrieval for large in-plane deformations with digital speckle photography1999In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 38, no 25, p. 5408-5412Article in journal (Refereed)
    Abstract [en]

    The compensation of large in-plane motions in digital speckle-pattern interferometry (DSPI) with the use of digital speckle photography (DSP) is demonstrated. Ordinary recordings of DSPI are recombined and analyzed with DSP. The DSP result is used to compensate for the bulk speckle motion prior to calculation of the phase map. This results in a high fringe contrast even for deformations of several speckle diameters. In addition, for the case of an in-plane deformation, it is shown that the absolute phase change in each pixel may be unwrapped by use of the DSP result as an initial guess. The principles of this method and experiments showing the in-plane rotation of a plate and the encounter of two rounded plates are presented

  • 9. Bajt, Sasa
    et al.
    Chapman, Henry N
    Spiller, Eberhard A
    Alameda, Jennifer B
    Woods, Bruce W
    Frank, Matthias
    Bogan, Michael J
    Barty, Anton
    Boutet, Sebastien
    Marchesini, Stefano
    Hau-Riege, Stefan P
    Hajdu, Janos
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
    Shapiro, David
    Camera for coherent diffractive imaging and holography with a soft-x-ray free-electron laser2008In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 47, no 10, p. 1673-1683Article in journal (Refereed)
    Abstract [en]

    We describe a camera to record coherent scattering patterns with a soft-x-ray free-electron laser (FEL). The camera consists of a laterally graded multilayer mirror, which reflects the diffraction pattern onto a CCD detector. The mirror acts as a bandpass filter for both the wavelength and the angle, which isolates the desired scattering pattern from nonsample scattering or incoherent emission from the sample. The mirror also solves the particular problem of the extreme intensity of the FEL pulses, which are focused to greater than 10(14) W/cm2. The strong undiffracted pulse passes through a hole in the mirror and propagates onto a beam dump at a distance behind the instrument rather than interacting with a beam stop placed near the CCD. The camera concept is extendable for the full range of the fundamental wavelength of the free electron laser in Hamburg (FLASH) FEL (i.e., between 6 and 60 nm) and into the water window. We have fabricated and tested various multilayer mirrors for wavelengths of 32, 16, 13.5, and 4.5 nm. At the shorter wavelengths mirror roughness must be minimized to reduce scattering from the mirror. We have recorded over 30,000 diffraction patterns at the FLASH FEL with no observable mirror damage or degradation of performance.

  • 10.
    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.

  • 11. Baxter, G. W.
    et al.
    Schlup, P.
    McKinnie, I. T.
    Hellstrom, J.
    Laurell, Fredrik
    KTH, Superseded Departments, Physics.
    Single-mode near-infrared optical parametric oscillator amplifier based on periodically poled KTiOPO42001In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 40, no 36, p. 6659-6662Article in journal (Refereed)
    Abstract [en]

    A singly resonant, single-axial-mode, optical parametric oscillator (OPO) based on periodically poled KTiOPO4 (PPKTP) is reported. Signal (1.68 mum) and idler (2.90 mum) optical bandwidths have been narrowed to < 400 MHz by use of a diffraction grating at grazing incidence. The OPO generates 370 muJ of signal radiation when pumped by 3.1 mJ of 1.064-mum radiation. We implemented a single-pass PPKTP amplifier to yield 2.15-mJ signal and 1.17-mJ idler radiation without broadening the spectral bandwidths.

  • 12.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Disputing Viking navigation by polarized skylight.1994In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 33, no 21, p. 4754-5Article in journal (Refereed)
    Abstract [en]

    The widely held notion that the Vikings utilized polarization of skylight on overcast days for navigational purposes is demonstrated to have no scientific basis. The use of polarized skylight for navigation under partly cloudfree skies should be treated with caution and skepticism.

  • 13.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Intraocular light scattering in vision, artistic painting, and photography.1994In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 33, no 21, p. 4749-53Article in journal (Refereed)
    Abstract [en]

    Light scattering in the eye is reviewed, and its influence on vision is discussed in some detail. Isotropic scattering and formation of halos around point sources are described with reference to theory and experiments. Artists usually take intraocularly scattered light into account when painting natural scenes. A method to achieve similar effects in photography by the use of diffraction filters in front of the camera lens is demonstrated. A number of photos that illustrate the effects of such filters are shown.

  • 14.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Optical properties of diffractive, bifocal, intraocular lenses.1992In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 31, no 13, p. 2377-84Article in journal (Refereed)
    Abstract [en]

    The resolution of diffractive, bifocal, intraocular lenses was studied with regard to pupil displacement and diameter size through computer simulations, bench measurements, and patient vision-acuity measurements. Good agreement was obtained between these three methods of investigation. In particular, we find that pupil displacements of the order of 1 mm reduce the resolution considerably for these lenses.

  • 15.
    Benckert, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    A method to resolve the 180° ambiguity in speckle photography1991In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 30, no 4, p. 376-378Article in journal (Other academic)
    Abstract [en]

    A new way of resolving the 180° ambiguity in speckle photography is presented. Results from a study of the deformation of a wooden block caused by drying illustrates the method

  • 16.
    Benckert, Lars
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Forsberg, Lars
    Molin, Nils-Erik
    Fresnel diffraction of a Gaussian laser beam by polished metal cylinders1990In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 29, no 3, p. 416-421Article in journal (Refereed)
    Abstract [en]

    A laser beam touching the periphery of a polished cylinder is subjected to both diffraction and reflection. Inthe area where diffracted light and reflected light interact the resulting intensity distribution differs from thepattern predicted by diffraction theory for a sharp edge. The difference increases with cylinder radius. Inthis paper it is shown that a good description of the resulting intensity pattern is obtained by adding thereflected light amplitude to the diffracted amplitude as predicted by the Fresnel-Kirchhoff theory for a sharpedge.

  • 17.
    Bergström, David
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Powell, John
    Laser Expertise Ltd., Nottingham, United Kingdom.
    Kaplan, Alexander
    Luleå University of Technology.
    Absorptance of Non-Ferrous Alloys to Nd:YLF and Nd:YAG Laser Light at Room Temperature2007In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 46, no 8, p. 1290-1301Article in journal (Refereed)
    Abstract [en]

    The measurement of absorptance is important for the analysis and modelling of laser-material interactions. Unfortunately, most of the absorptance data presently available considers only polished pure metals rather than the commercially available (unpolished, oxidised) alloys which are actually being processed in manufacturing. This paper presents the results of absorptance measurements carried out at room temperature on as-received engineering grade non-ferrous metals (Al, Cu and Zn alloys). The measurements were made using an integrating sphere with an Nd:YLF laser at two wavelengths (1053nm and 527nm � which means that the results are also valid for Nd:YAG radiation at 1064nm and 532nm). The absorptance results obtained differ considerably from existing data for polished, pure metals and should help improve the accuracy of laser-material interaction models. Some clear trends were identified. For all 22 cases studied the absorptance was higher than for ideal pure, polished metals. For all Al- and Cu-samples the absorptance was higher for the green than it was for the infrared wavelength, while for all Zn-coatings this trend was reversed. No clear correlation between absorptance and surface roughness was found at low roughness values (Sa 0.15 � 0.60) but one, rougher set of samples (Sa 2.34), indicated a roughness-absorptance correlation at higher roughness levels.

  • 18.
    Bergström, David
    et al.
    Mid Sweden University.
    Powell, John
    Laser Expertise Ltd., Acorn Park Industrial Estate, Nottingham.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Absorptance of nonferrous alloys to Nd:YLF and Nd:YAG laser light at room temperature2007In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 46, no 8, p. 1290-1301Article in journal (Refereed)
    Abstract [en]

    The measurement of absorptance is important for the analysis and modeling of laser-material interactions. Unfortunately, most of the absorptance data currently available consider only polished pure metals rather than the commercially available (unpolished, oxidized) alloys that are actually being processed in manufacturing. We present the results of absorptance measurements carried out at room temperature on as-received engineering grade nonferrous metals (Al, Cu, and Zn alloys). The measurements were made using an integrating sphere with a Nd:YLF laser at two wavelengths (1053 and 527 nm, which means that the results are also valid for Nd:YAG radiation at 1064 and 532 nm). The absorptance results obtained differ considerably from the existing data for polished, pure metals and should help improve the accuracy of laser-material interaction models. Some clear trends were identified. For all 22 cases studied the absorptance was higher than for ideal pure, polished metals. For all Al and Cu samples the absorptance was higher for the green than it was for the infrared wavelength, while for all Zn coatings this trend was reversed. No clear correlation between absorptance and surface roughness was found at low roughness values (Sa 0.15-0.60), but one rougher set of samples (Sa 2.34) indicated a roughness-absorptance correlation at higher roughness levels.

  • 19.
    Bergström, Per
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Khodadad, Davood
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Hällstig, Emil
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Dual-wavelength digital holography: single-shot shape evaluation using speckle displacements and regularization2014In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 53, no 1, p. 123-131Article in journal (Refereed)
  • 20.
    Bergström, Per
    et al.
    Luleå University of Technology.
    Khodadad, Davood
    Luleå University of Technology.
    Hällstig, Emil
    Optronic Partner dp AB.
    Sjödahl, Mikael
    Luleå University of Technology.
    Dual-wavelength digital holography: single-shot shape evaluation using speckle displacements and regularization2014In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 53, no 1, p. 123-131Article in journal (Refereed)
    Abstract [en]

    This paper discusses the possibility of evaluating the shape of a free-form object in comparison with its shape prescribed by a CAD model. Measurements are made based on a single-shot recording using dual-wavelength holography with a synthetic wavelength of 1.4 mm. Each hologram is numerically propagated to different focus planes and correlated. The result is a vector field of speckle displacements that is linearly dependent on the local distance between the measured surface and the focus plane. From these speckle displacements, a gradient field of the measured surface is extracted through a proportional relationship. The gradient field obtained from the measurement is then aligned to the shape of the CAD model using the iterative closest point (ICP) algorithm and regularization. Deviations between the measured shape and the CAD model are found from the phase difference field, giving a high precision shape evaluation. The phase differences and the CAD model are also used to find a representation of the measured shape. The standard deviation of the measured shape relative the CAD model varies between 7 and 19 μm, depending on the slope.

  • 21.
    Bergström, Per
    et al.
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Khodadad, Davood
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Hällstig, Emil
    Optronic Partner Dp AB, Skellefteå, Sweden.
    Sjödahl, Mikael
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Dual-wavelength digital holography: single-shot shape evaluation using speckle displacements and regularization2014In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 53, no 1, p. 123-131Article in journal (Refereed)
    Abstract [en]

    This paper discusses the possibility of evaluating the shape of a free-form object in comparison with its shape prescribed by a CAD model. Measurements are made based on a single-shot recording using dual-wavelength holography with a synthetic wavelength of 1.4&#xA0;mm. Each hologram is numerically propagated to different focus planes and correlated. The result is a vector field of speckle displacements that is linearly dependent on the local distance between the measured surface and the focus plane. From these speckle displacements, a gradient field of the measured surface is extracted through a proportional relationship. The gradient field obtained from the measurement is then aligned to the shape of the CAD model using the iterative closest point (ICP) algorithm and regularization. Deviations between the measured shape and the CAD model are found from the phase difference field, giving a high precision shape evaluation. The phase differences and the CAD model are also used to find a representation of the measured shape. The standard deviation of the measured shape relative the CAD model varies between 7 and 19 μm, depending on the slope.

  • 22.
    Bhaduri, Basanta
    et al.
    National University of Singapore.
    Quan, Chenggen
    National University of Singapore.
    Tay, Cho Jui
    National University of Singapore.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Simultaneous measurement of translation and tilt using digital speckle photography2010In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 49, no 18, p. 3573-3579Article in journal (Refereed)
    Abstract [en]

    A Michelson-type digital speckle photographic system has been proposed in which one light beam produces a Fourier transform and another beam produces an image at a recording plane, without interfering between themselves. Because the optical Fourier transform is insensitive to translation and the imaging technique is insensitive to tilt, the proposed system is able to simultaneously and independently determine both surface tilt and translation by two separate recordings, one before and another after the surface motion, without the need to obtain solutions for simultaneous equations. Experimental results are presented to verify the theoretical analysis.

  • 23.
    Bjurshagen, Stefan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Hellström, Jonas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pujol, Maria
    Fisica I Cristal-Lografia de Materials (FiCMA), Universitat Rovira I Virgili, Spain.
    Aguiló, Magdalena
    Fisica I Cristal-Lografia de Materials (FiCMA), Universitat Rovira I Virgili, Spain.
    Díaz, Francesc
    Fisica I Cristal-Lografia de Materials (FiCMA), Universitat Rovira I Virgili, Spain.
    Fluorescence dynamics and rate equations analysis in Er3+,Yb3+ doped double tungstates2006In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 45, no 19, p. 4715-4725Article in journal (Refereed)
    Abstract [en]

    The fluorescence dynamics in Er3+ and Yb3+ doped KGd(WO4)(2) and KY(WO4)(2) has been investigated. Lifetimes have been measured for the Yb(F-2(5/2)), Er(I-4(13/2)), and Er(S-4(3/2)) levels around 1, 1.5, and 0.55 mu m, respectively. The Yb(F-2(5/2)) lifetimes show a decreasing trend toward the limiting Er(I-4(11/2)) lifetime with increasing Er-to-Yb concentration ratio, whereas the Er(I-4(13/2)) lifetimes are mostly unaffected by the doping concentrations. A rate equation analysis has been performed to explain the observed behavior and gain is calculated for a continuous-wave laser at 1.53 mu m to find the optimum doping concentrations for high gain.

  • 24.
    Bjurshagen, Stefan
    et al.
    KTH, Superseded Departments, Physics.
    Koch, R.
    Acreo AB, Kista.
    Modeling of energy-transfer upconversion and thermal effects in end-pumped quasi-three-level lasers2004In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 43, no 24, p. 4735-4767Article in journal (Refereed)
    Abstract [en]

    An analytical model of cw quasi-three-level lasers that includes the influence of energy-transfer upconversion (ETU) has been developed. The results of the general output modeling were applied to a laser with Gaussian beams, and rigorous numerical calculations have been made to study the influence of ETU on threshold, output power, spatial distribution of population-inversion density, and fractional thermal loading. The model was applied to a laser operating at 946 nm in Nd:YAG, where the dependence of laser-beam size on laser performance was investigated in particular. A simple model for the degradation of laser-beam quality from a transversally varying saturated gain is proposed that is in good agreement with measurements of the laser in a plane-plane cavity.

  • 25.
    Blom, Hans
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Björk, Gunnar
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Lorentzian spatial intensity distribution in one-photon fluorescence correlation spectroscopy2009In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 48, no 31, p. 6050-6058Article in journal (Refereed)
    Abstract [en]

    The theory of autocorrelation-function evaluation in fluorescence correlation spectroscopy is applied to a Lorentzian intensity distribution. An analytical solution to the autocorrelation function for diffusion is deduced for this spatial distribution. Experimental investigation of the distribution is performed using an enlarged detector aperture in a standard confocal setup. The data from the experiment are fitted to the derived autocorrelation function, and a reasonable estimate of the spatial distribution is provided. Estimates are also compared to values computed by molecular detection efficiency simulation. The use of Lorentzian intensity distributions complements conditions where a Gaussian intensity distribution applies, expanding the applicability range of analytical correlation functions.

  • 26.
    Blom, Hans
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Johansson, Mathias
    Gösch, Michael
    Sigmundsson, Toni
    Holm, Johan
    Hård, Sverker
    Rigler, Rudolf
    Parallel Flow Measurements in Microstructures by Use of a Multifocal 4 x 1 Diffractive Optical Fan-Out Element2002In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 41, no 31, p. 6614-6620Article in journal (Refereed)
    Abstract [en]

    We have developed a multifocal optical fluorescence correlation spectroscopy system for parallel flow analyses. Multifocal excitation was made possible through a 4 x 1 diffractive optical fan-out element, which produces uniform intensity in all four foci. Autocorrelation flow analyses inside a 20 μm x 20 μm square microchannel, with the 4 x 1 fan-out foci perpendicular to the flow direction, made it possible to monitor different flows in all four foci simultaneously. We were able to perform cross-correlation flow analyses by turning the microstructure, thereby having all four foci parallel to the direction of flow. Transport effects of the diffusion as a function of flow and distance could then also be studied.

  • 27.
    Blom, Hans
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Johansson, Mathias
    Hedman, Anna-Sara
    Lundberg, Liselotte
    Hanning, Anders
    Hård, Sverker
    Rigler, Rudolf
    Parallel Fluorescence Detection of Single Biomolecules in Microarrays by a Diffractive-Optical-Designed 2 x 2 Fan-Out Element2002In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 41, no 16, p. 3336-3342Article in journal (Refereed)
    Abstract [en]

    We have developed a multifocal diffractive-optical fluorescence correlation spectroscopy system for parallel excitation and detection of single tetramethylrhodamine biomolecules in microarrays. Multifocal excitation was made possible through the use of a 2 × 2 fan-out diffractive-optical element with uniform intensity in all foci. Characterization of the 2 × 2 fan-out diffractive-optical element shows formation of almost perfect Gaussian foci of submicrometer lateral diameter, as analyzed by thermal motion of tetramethylrhodamine dye molecules in solution. Results of parallel excitation and detection in a high-density microarray of circular wells show single-biomolecule sensitivity in all four foci simultaneously.

  • 28. Boyko, Andrey A.
    et al.
    Kostyukova, Nadezhda Y.
    Badikov, Valeriy
    Badikov, Dmitrii
    Panyutin, Vladimir
    Shevyrdyaeva, Galina
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Zukauskas, Andrius
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Marchev, Georgi M.
    Kolker, Dmitry B.
    Petrov, Valentin
    Intracavity difference-frequency mixing of optical parametric oscillator signal and idler pulses in BaGa4Se72017In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 56, no 10, p. 2783-2786Article in journal (Refereed)
    Abstract [en]

    An overall quantum conversion efficiency of 7.8% is achieved by intracavity mixing the signal and idler of a 1.064 mu m pumped Rb: PPKTP optical parametric oscillator in BaGa4Se7. In this way, a pulse energy of similar to 0.71 mJ is generated at similar to 7 mu m for a repetition rate of 100 Hz. Tuning of the mid-IR radiation is demonstrated by heating of the Rb: PPKTP crystal.

  • 29.
    Bruns, Marco
    et al.
    Universität Bremen, Institute of Environmental Physics.
    Buehler, Stefan
    Burrows, John P.
    Universität Bremen, Institute of Environmental Physics.
    Heue, Klaus-Peter
    University of Heidelberg, Institute of Environmental Physics.
    Platt, Ulrich
    University of Heidelberg, Institute of Environmental Physics.
    Pundt, Irene
    University of Heidelberg, Institute of Environmental Physics.
    Richter, Andreas
    Universität Bremen, Institute of Environmental Physics.
    Rozanov, Alexej
    Universität Bremen, Institute of Environmental Physics.
    Wagner, Thomas
    University of Heidelberg, Institute of Environmental Physics.
    Wang, Ping
    Universität Bremen, Institute of Environmental Physics.
    Retrieval of profile information from airborne multiaxis UV-visible skylight absorption measurements2004In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 43, no 22, p. 4415-4426Article in journal (Refereed)
    Abstract [en]

    A recent development in ground-based remote sensing of atmospheric constituents by UV-visible, absorption measurements of scattered light is the simultaneous use of several horizon viewing directions in addition to the traditional zenith-sky pointing. The different light paths through the atmosphere enable the vertical distribution of some atmospheric absorbers, such as NO2, BrO, or O-3, to be retrieved. This approach has recently been implemented on an airborne platform. This novel instrument, the airborne multiaxis differential optical absorption spectrometer (AMAXDOAS), has been flown for the first time. In this study, the amount of profile information that can be retrieved from such measurements is investigated for the trace gas NO2. Sensitivity studies on synthetic data are performed for a variety of representative measurement conditions including two wavelengths, one in the UV and one in the visible, two different surface spectral reflectances, various lines of sight (LOSs), and for two different flight altitudes. The results demonstrate that the AMAXDOAS measurements contain useful profile information, mainly at flight altitude and below the aircraft. Depending on wavelength and LOS used, the vertical resolution of the retrieved profiles is as good as 2 km near flight altitude. Above 14 km the profile information content of AMAXDOAS measurements is sparse. Airborne multiaxis measurements are thus a promising tool for atmospheric studies in the troposphere and the upper troposphere and lower stratosphere region.

  • 30.
    Burvall, Anna
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Kolacz, K.
    Jaroszewicz, Z.
    Friberg, Ari T.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Simple lens axicon2004In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 43, no 25, p. 4838-4844Article in journal (Refereed)
    Abstract [en]

    We present the design of a cemented doublet-lens axicon made from spherical surfaces only. Compared with diffractive axicons, refractive cone axicons, and earlier lens axicons with aspheric surfaces, this element is inexpensive and easy to manufacture even with large apertures. The lens axicon is based on the deliberate use of the spherical aberration of the surfaces. The design principles of the element and its characterization, numerically and experimentally, are presented in detail. Although performance was traded for simplicity and robustness, the results show that the lens axicon has the main axicon properties: a narrow, extended line focus of relatively constant width.

  • 31.
    Burvall, Anna
    et al.
    National University of Ireland, Galway.
    Kolacz, Katarzyna
    Institute of Applied Optics, Warsaw.
    Goncharov, Alexander
    National University of Ireland, Galway.
    Jaroszewicz, Zbigniew
    Institute of Applied Optics, Warsaw.
    Dainty, Christopher
    National University of Ireland, Galway.
    Lens axicons in oblique illumination2007In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 46, no 3, p. 312-318Article in journal (Refereed)
    Abstract [en]

    Lens axicons, i.e., lenses or lens systems designed to work like axicons, can be a simple and inexpensive way of generating the characteristic axicon focal line. In the design of most lens axicons, only on-axis properties have been considered. We present the design of a lens axicon with improved off-axis characteristics. It is constructed from a singlet lens but with a double-pass feature that allows for a line of uniform width and a stop positioned to minimize aberrations. We perform off-axis analysis and experiments for this system and for another lens axicon, one designed for its on-axis characteristics. We conclude that the off-axis performance of the double-pass axicon is better than both that of an ordinary cone axicon and that of the other lens axicon.

  • 32. Canning, John
    et al.
    Åslund, Mattias
    Ankiewicz, Adrian
    Dainese, Matteo
    KTH, Superseded Departments, Electronics.
    Fernando, Harendra
    KTH, Superseded Departments, Electronics.
    Sahu, Jayanta Kumar
    KTH, Superseded Departments, Electronics.
    Wosinski, Lech
    KTH, Superseded Departments, Electronics.
    Birefringence control in plasma-enhanced chemical vapor deposition planar waveguides by ultraviolet irradiation2000In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 39, no 24, p. 4296-4299Article in journal (Refereed)
    Abstract [en]

    Complete birefringence compensation is demonstrated in plasma-enhanced chemical vapor deposition waveguides by 193-nm postexposure. A single relaxation process dominates the decay in stress anisotropy, indicating that compressive stress from the substrate leads to an elastic stress anisotropy at the core.

  • 33.
    Carlsson, Torgny E.
    et al.
    KTH, Superseded Departments, Production Engineering.
    Wei, A.
    Phase evaluation of speckle patterns during continuous deformation by use of phase-shifting speckle interferometry2000In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 39, no 16, p. 2628-2637Article in journal (Refereed)
  • 34.
    Casselgren, Johan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Polarization resolved classification of winter road condition in the near-infrared region2012In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 51, no 15, p. 3036-3045Article in journal (Refereed)
    Abstract [en]

    Three different configurations utilizing polarized short-wave infrared light to classify winter road conditions have been investigated. In the first configuration, polarized broadband light was detected in the specular and backward directions, and the quotient between the detected intensities was used as the classification parameter. Best results were obtained for the SS-configuration. This sensor was shown to be able to distinguish between the smooth road conditions of water and ice from the diffuse road conditions of snow and dry asphalt with a probability of wrong classification as low as 7%. The second sensor configuration was a pure backward architecture utilizing polarized light with two distinct wavelengths. This configuration was shown to be effective for the important problem of distinguishing water from ice with a probability of wrong classification of only 1.5%. The third configuration was a combination of the two previous ones. This combined sensor utilizing bispectral illumination and bidirectional detection resulted in a probability of wrong classification as low as 2% among all four surfaces.

  • 35.
    Casselgren, Johan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Leblanc, James
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Angular spectral response from covered asphalt2007In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 46, no 20, p. 4277-4288Article in journal (Refereed)
    Abstract [en]

    By measuring the spectral reflection from the four different road conditions dry, wet, icy, and snowy asphalt, a method of classification for the different surfaces -- using two and three wavelengths -- is developed. The method is tested against measurements to ascertain the probability of wrong classification between the surfaces. From the angular spectral response, the fact that asphalt and snow are diffuse reflectors and water and ice are reflective are confirmed.

  • 36.
    Coppel, L.G.
    et al.
    RISE, Innventia.
    Andersson, M.
    Edström, P.
    Determination of quantum efficiency in fluorescing turbid media2011In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, no 17, p. 2784-2792Article in journal (Refereed)
  • 37.
    Cronhjort, Andreas
    et al.
    Scania CV AB.
    Wåhlin, Fredrik
    Scania CV AB.
    Segmentation Algorithm for Diesel Spray Image Analysis2004In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 43, no 32, p. 5971-5980Article in journal (Refereed)
    Abstract [en]

    An algorithm for segmentation of diesel spray images has been developed. Its most important feature is robustness against experimental setups that fail to guarantee images whose histograms show two distinct peaks. According to the approach presented, only the peak from the background is used, and it is assumed that the background peak is narrow enough not to include too much of the spray. The algorithm has proved successful for evaluation of images from a pressurized vessel as well as from an engine with optical access, with no need for adjusting the tuning parameters. By adjusting them, one may tune the noise sensitivity.

  • 38.
    Daemi, Bita
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Ekberg, Peter
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Mattsson, Lars
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Advanced image analysis verifies geometry performance of micro-milling systems2017In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 56, no 10, p. 2912-2921Article in journal (Refereed)
    Abstract [en]

    Accurate dimensional measurement of micro-milled items is a challenge and machine specifications do not include operational parameters in the workshop. Therefore, a verification test that shows the machine's overall geometrical performance over its working area would help machine users in the assessment and adjustment of their equipment. In this study, we present an optical technique capable of finding micro-milled features at submicron uncertainty over working areas > 10 cm(2). The technique relies on an ultra-precision measurement microscope combined with advanced image analysis to get the center of gravity of milled cross-shaped features at subpixel levels. Special algorithms had to be developed to handle the disturbing influence of burr and milling marks. The results show repeatability, reproducibility, and axis straightness for three micro-milling facilities and also discovered an unknown 2 mu m amplitude undulation in one of them.

  • 39. Dai, D. X.
    et al.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Analysis of multimode effects in the free-propagation region of a silicon-on-insulator-based arrayed-waveguide grating demultiplexer2003In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 42, no 24, p. 4860-4866Article in journal (Refereed)
  • 40. Dai, D. X.
    et al.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Design of an ultrashort Si-nanowaveguide-based multimode interference coupler of arbitrary shape2008In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 47, no 1, p. 38-44Article in journal (Refereed)
    Abstract [en]

    A design procedure for an arbitrarily tapered multimode interference (MMI) coupler based on Si nanowaveguides is presented. First a series of the effective indices of the zeroth and first eigenmodes in multimode waveguides are obtained as the core width increases by using a full-vectorial finite-difference method. Two polynomial functions are used to fit the two relations between the effective indices and the core width. The phase difference Delta phi between the zeroth and first eigenmodes can then be easily calculated when the light goes through any given arbitrarily tapered MMI section. By making the phase difference Delta phi equal to a certain value Delta phi(0) required for an N-fold self-imaging, the length of a MMI coupler is determined. With the present design procedure, an ultrashort 2 x 2 parabolic MMI coupler is designed as an example. The size of the designed ultrashort MMI section is only similar to 1.4 mu m X 4.7 mu m.

  • 41.
    Dai, Daoxin
    et al.
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    He, Jian-Jun
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Compact silicon-on-insulator-based multimode interference coupler with bilevel taper structures2005In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 44, no 24, p. 5036-5041Article in journal (Refereed)
    Abstract [en]

    A novel compact silicon-on-insulator- (SOI-)based multimode interference (MMI) coupler with bilevel taper structures was designed. The MMI section and the S-bend sections of the input-output waveguides are deeply etched. The input-output waveguides connecting to single-mode fibers or other photonic light circuits are etched shallowly to yield single-mode operation. A bilevel taper is introduced in the transition region between the shallowly and deeply etched regions. It is predicted theoretically that this design will not only improve the quality of the self-imaging in the MMI section but will also make the structure compact. Both the excess loss and the nonuniformity of the MMI coupler are reduced. By use of a three-dimensional beam propagation method, the performance of a 1 × 4 MMI coupler based on a SOI is simulated as a numerical example of the novel design. The simulated nonuniformity and the excess loss are approximately 0.0285 and 0.2 dB, respectively.

  • 42.
    Dai, Daoxin
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    He, Sailing
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. KTH, Superseded Departments, Electromagnetic Theory.
    Analysis of the birefringence of a silicon-on-insulator rib waveguide2004In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 43, no 5, p. 1156-1161Article in journal (Refereed)
    Abstract [en]

    A detailed analysis of the polarization characteristics (birefringence) of a silicon-on-insulator (SOI) rib waveguide is given. The fundamental TE- and TM-polarized modes of the SOI rib waveguide are calculated by a semivectorial finite-difference method. The rib width and the slab height of the SOI rib waveguide are normalized with respect to the total height of the silicon layer. A general relation between the two normalized parameters for a nonbirefringent SOI rib waveguide is obtained. According to this relation a nonbirefringent SOI rib waveguide can easily be designed. The fabrication tolerance for a nonbirefringent SOI rib waveguide is also analyzed, revealing that the tolerance can be increased by use of a larger total height of the silicon layer.

  • 43. Dai, Daoxin
    et al.
    Shi, Yaocheng
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Characteristic analysis of nanosilicon rectangular waveguides for planar light-wave circuits of high integration2006In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 45, no 20, p. 4941-4946Article in journal (Refereed)
  • 44. Dai, Daoxin
    et al.
    Shi, Yaocheng
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Comparative study of the integration density for passive linear planar light-wave circuits based on three different kinds of nanophotonic waveguide2007In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 46, no 7, p. 1126-1131Article in journal (Refereed)
  • 45.
    Degerman Engfeldt, Johnny
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Georen, Peter
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, N Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Methodology for measuring current distribution effects in electrochromic smart windows2011In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 50, no 29, p. 5639-5646Article in journal (Refereed)
    Abstract [en]

    Electrochromic (EC) devices for use as smart windows have a large energy-saving potential when used in the construction and transport industries. When upscaling EC devices to window size, a well-known challenge is to design the EC device with a rapid and uniform switching between colored (charged) and bleached (discharged) states. A well-defined current distribution model, validated with experimental data, is a suitable tool for optimizing the electrical system design for rapid and uniform switching. This paper introduces a methodology, based on camera vision, for experimentally validating EC current distribution models. The key is the methodology's capability to both measure and simulate current distribution effects as transmittance distribution. This paper also includes simple models for coloring (charging) and bleaching (discharging), taking into account secondary current distribution with charge transfer resistance and ohmic effects. Some window-size model predictions are included to show the potential for using a validated EC current distribution model as a design tool.

  • 46.
    Delacroix, Christian
    et al.
    Hololab, Université de Liège, Belgien.
    Forsberg, Pontus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Karlsson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Mawet, Dimitri
    European Southern Observatory (ESO), Santiago, Chile.
    Absil, Olivier
    IAGL, Université de Liège, Belgien.
    Hanot, Charles
    IAGL, Université de Liège, Belgien.
    Surdej, Jean
    IAGL, Université de Liège, Belgien.
    Habraken, Serge
    Hololab, Université de Liège, Belgien.
    Design, manufacturing, and performance analysis of mid-infrared achromatic half-wave plates with diamond subwavelength gratings2012In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 51, no 24, p. 5897-5902Article in journal (Refereed)
    Abstract [en]

    In this paper, we present a solution for creating robust monolithic achromatic half-wave plates (HWPs) for the infrared, based on the form birefringence of subwavelength gratings (SWGs) made out of diamond. We use the rigorous coupled wave analysis to design the gratings. Our analysis shows that diamond, besides its outstanding physical and mechanical properties, is a suitable substrate to manufacture mid-infrared HWPs, thanks to its high refractive index, which allows etching SWGs with lower aspect ratio. Based on our optimized design, we manufactured a diamond HWP for the 11-13.2 mu m region, with an estimated mean retardance similar to 3.143 +/- 0.061 rad ( 180.08 +/- 3.51 degrees). In addition, an antireflective grating was etched on the backside of the wave plate, allowing a total transmittance between 89% and 95% over the band.

  • 47.
    Dong, Lin
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Sugunan, Abhilash
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Hu, Jun
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Zhou, Sicheng
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Li, Shanghua
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Photoluminescence from quasi-type-II spherical CdSe-CdS core-shell quantum dots2013In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 52, no 1, p. 105-109Article in journal (Refereed)
    Abstract [en]

    Spherical CdSe-CdS core-shell quantum dots (QDs) are found to be flexible in the transition between the type-I regime and the type-II regime with different core/shell dimensions. The quasi-type-II feature of the colloidal dots is confirmed with time-resolved photoluminescence (PL) measurements. Two recombination paths of the excitons with significantly different decay rates are observed and analyzed. The spherical CdSe-CdS core-shell QDs are numerically simulated to investigate the carrier separation. A relatively long radiative lifetime and high degree of spatial carrier separation provide good potential to achieve lasing under continuous-wave excitation. Amplified spontaneous emission at room temperature is detected from the QDs embedded in the polymer matrix. It is shown that a larger shell thickness results in a lower pumping threshold, while a smaller shell thickness leads to higher PL efficiency.

  • 48.
    Echle, Georg
    et al.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Clarmann, Thomas von
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Dudhia, Anu
    Atmospheric, Oceanic, and Planetary Physics, Oxford University.
    Flaud, Jean-Marie
    Laboratoire de Photophysique Moléculaire, CNRS, Université Paris-Sud, Orsay.
    Funke, Bernd
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Glatthor, Norbert
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Kerridge, Brian
    Rutherford Appleton Laboratory, Oxfordshire.
    López-Puertas, Manuel
    Instituto de Astrofísica de Andalucía CSIC, Granada.
    Martin-Torres, Javier
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Stiller, Gabriele P.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Optimized spectral microwindows for data analysis of the Michelson Interferometer for Passive Atmospheric Sounding on the Environmental Satellite2000In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 39, no 30, p. 5531-Article in journal (Refereed)
    Abstract [en]

    For data analysis of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) atmospheric limb emission spectroscopic experiment on Environmental Satellite microwindows, i.e., small spectral regions for data analysis, have been defined and optimized. A novel optimization scheme has been developed for this purpose that adjusts microwindow boundaries such that the total retrieval error with respect to measurement noise, parameter uncertainties, and systematic errors is minimized. Dedicated databases that contain optimized microwindows for retrieval of vertical profiles of pressure and temperature, H2O, O3, HNO3, CH4, N2O, and NO2 have been generated. Furthermore, a tool for optimal selection of subsets of predefined microwindows for specific retrieval situations has been provided. This tool can be used further for estimating total retrieval errors for a selected microwindow subset. It has been shown by use of this tool that an altitude-dependent definition of microwindows is superior to an altitude-independent definition. For computational efficiency a dedicated microwindow-related list of spectral lines has been defined that contains only those spectral lines that are of relevance for MIPAS limb sounding observations.

  • 49.
    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).

  • 50. Franco, C S
    et al.
    Quintero, G A
    Myren, N
    Kudlinski, A
    Zeghlache, H
    Carvalho, H R
    Triques, A L C
    Gonzales, D M
    Gouvêa, P M P
    Martinelli, G
    Quiquempois, Y
    Lesche, B
    Margulis, W
    RISE, Swedish ICT, Acreo.
    Carvalho, I C S
    Measurement of Depletion Region Width in Poled Silica2005In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 42, no 27, p. 5793-96Article in journal (Refereed)
12345 1 - 50 of 221
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