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  • 1.
    Burvall, Anna
    et al.
    National University of Ireland, Galway.
    Smith, Arlene
    National University of Ireland, Galway.
    Dainty, Christopher
    National University of Ireland, Galway.
    Elementary functions: Propagation of partially coherent light2009In: Journal of the Optical Society of America A, ISSN 0740-3232, Vol. 26, no 7, p. 1721-1729Article in journal (Refereed)
    Abstract [en]

    The theory of propagation of partially coherent light is well known, but performing numerical calculations still presents a difficulty because of the dimensionality of the problem. We propose using a recently introduced method based on the use of elementary functions [Wald et al. Proc. SPIE6040, 59621G (2005)] to reduce the integrals to two dimensions. We formalize the method, describe its inherent assumptions and approximations, and introduce a sampling criterion for adequate interpolation. We present an analysis of some special cases, such as the Gaussian Schell-model beam, and briefly discuss generalized numerical propagation of two-dimensional field distributions.

  • 2.
    Dai, Daoxin
    et al.
    KTH, Superseded Departments, Alfvén Laboratory.
    He, Sailing
    KTH, Superseded Departments, Alfvén Laboratory.
    Analysis of characteristics of bent rib waveguides2004In: Journal of the Optical Society of America A, ISSN 0740-3232, Vol. 21, no 1, p. 113-121Article in journal (Refereed)
    Abstract [en]

    With a perfectly matched layer boundary treatment, a semivectorial finite-difference method is used to calculate the eigenmodes of a single-mode (SM) or multimode (MM) bent rib waveguide. A detailed analysis is given for the dependence of the bending losses (including the pure bending loss and the transition loss) on geometrical parameters of the bent rib waveguide such as the rib width, the rib height, and the bending radius. The characteristics of the higher-order modes are analyzed. It is shown that the bending loss of the fundamental mode can be reduced effectively by increasing the width and height of the rib. For an integrated device, undesired effects due to the higher-order modes of a MM bent waveguide can be removed by appropriate choice of the geometrical parameters. An appropriately designed MM bent waveguide is used to reduce effectively the bending loss of the fundamental mode, and a low-loss SM propagation in a MM bent waveguide is realized when the bending losses of the higher-order modes are large enough.

  • 3.
    Li, Xuan
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Jin, Yi
    Hyperlens with non-negative effective permittivities and increasing layer thicknessIn: Journal of the Optical Society of America A, ISSN 0740-3232Article in journal (Refereed)
  • 4.
    Lundström, Linda
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Unsbo, Peter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Transformation of Zernike coefficients: scaled, translated, and rotated wavefronts with circular and elliptical pupils2007In: Journal of the Optical Society of America A, ISSN 0740-3232, Vol. 24, no 3, p. 569-577Article in journal (Refereed)
    Abstract [en]

    Zernike polynomials and their associated coefficients are commonly used to quantify the wavefront aberrations of the eye. When the aberrations of different eyes, pupil sizes, or corrections are compared or averaged, it is important that the Zernike coefficients have been calculated for the correct size, position, orientation, and shape of the pupil. We present the first complete theory to transform Zernike coefficients analytically with regard to concentric scaling, translation of pupil center, and rotation. The transformations are described both for circular and elliptical pupils. The algorithm has been implemented in MATLAB, for which the code is given in an appendix.

  • 5.
    Martinsson, Per
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Lajunen, Hanna
    Friberg, Ari
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Communication modes with partially coherent fields2007In: Journal of the Optical Society of America A, ISSN 0740-3232, Vol. 24, no 10, p. 3336-3342Article in journal (Refereed)
    Abstract [en]

    We develop a theory for the description of partially coherent wave fields in linear optical systems in terms of the so-called communication modes. The communication modes are the singular functions and singular values of the appropriate propagation kernels. In particular, we show that optical fields of any state of coherence may be readily propagated through deterministic systems using the modal representation based on the system properties. The relation of the communication modes to the conventional coherent-mode representation is discussed, and expressions for the effective degree of coherence in the optical system are derived. The results are illustrated by numerical examples in optical near-field geometry.

  • 6. Ostlund, O.
    et al.
    Friberg, Ari T.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Radiation efficiency of partially coherent electromagnetic beams2001In: Journal of the Optical Society of America A, ISSN 0740-3232, Vol. 18, no 7, p. 1696-1703Article in journal (Refereed)
    Abstract [en]

    We present a general definition of the radiation efficiency of stationary electromagnetic fields and prove that it is bounded between zero and unity for beams of any state of coherence and polarization. The radiation efficiency may be interpreted as a measure of how directed the radiated fields are, and therefore it can be used to assess the allowed spatial coherence and intensity variations across a beam. We consider a class of partially coherent electromagnetic fields that were recently introduced in the literature and evaluate the radiation efficiencies for two particular examples, namely, the azimuthally polarized symmetric beams and the dipolar beams that are nearly linearly polarized in the central region. The results show that the radiation efficiency is fairly insensitive to the state of polarization and that it differs appreciably from unity for only small values of source and correlation widths.

  • 7. Philip, J.
    et al.
    Carlsson, Kjell
    KTH, Superseded Departments, Physics.
    Theoretical investigation of the signal-to-noise ratio in fluorescence lifetime imaging2003In: Journal of the Optical Society of America A, ISSN 0740-3232, Vol. 20, no 2, p. 368-379Article in journal (Refereed)
    Abstract [en]

    We deduce the signal-to-noise ratio for fluorescence lifetime imaging when using frequency-domain methods. We assume mono-exponential decay and quantum-noise-limited performance. The results are compared with Monte Carlo simulations with good agreement. We also compare our results with previous investigations of time-domain methods for fluorescence lifetime imaging. For a given number of detected photons, we find that frequency-domain and time-domain methods are equally good. The correct choice of detection technique and its parameters is important for obtaining good results.

  • 8. Rydefalk, Staffan
    Fluctuations in the regular transmittance of dispersions of straight circular cylinders with a diameter much larger than the wavelength of the radiation1998In: Journal of the Optical Society of America A, ISSN 0740-3232, Vol. 15, no 6, p. 1689-1697Article in journal (Refereed)
    Abstract [en]

    The expected value and the variance of the regular transmittance of a dilute dispersion of slender straight circular cylinders with a diameter much larger than the wavelength of the radiation are studied theoretically in relation to the dimensions of the cylinders and the diameter of the radiation beam used. Both monodisperse and heterodisperse dispersions are considered. The study is Limited to two particle categories: (i) particles that are short and (ii) particles that are long but thin compared with the diameter of the radiation beam. The expected value is a function of concentration and particle diameter. The variance is proportional to the concentration. The variance is also proportional to particle length in the case of short particles but not in the case of long particles. The results explain interesting possibilities for the characterization of dispersions of large cylindrical particles shown earlier in industrial on-line applications.

  • 9. Rydefalk, Staffan
    Theory of fluctuations in the regular transmittance through a dispersion of large cylindrical particles: extension to higher concentrations1999In: Journal of the Optical Society of America A, ISSN 0740-3232, Vol. 16, no 11, p. 2737-2745Article in journal (Refereed)
    Abstract [en]

    It has been shown in a previous paper [J. Opt. Sec. Am. A 15, 1689 (1998)] that the expected value and the Variance of the fluctuating regular transmittance through a dispersion of slender cylinders can be used to measure properties such as the size and concentration of the dispersed particles. The theory is valid, however, only for very low concentrations or very short path lengths. In practical applications, such as on-line applications, it is often desirable to work at higher concentration X path-length products p to avoid complicated sensor constructions. An extension of the previous theory toward higher values of p is presented. It is based on the assumption of the independence of the regular transmittance of parallel layers of the dispersion. The extended theory shows that information about the dispersion found in the expected Value and variance at very low values of p can also be obtained for higher values of p with a few simple expressions. Therefore applications possible in the case of low p values are also possible for higher p values. Two experimental examples have been included to facilitate the discussion of the theory presented.

  • 10. Setala, T.
    et al.
    Kaivola, H.
    Friberg, Ari T.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Evanescent and propagating electromagnetic fields in scattering from point-dipole structures2001In: Journal of the Optical Society of America A, ISSN 0740-3232, Vol. 18, no 3, p. 678-688Article in journal (Refereed)
    Abstract [en]

    We investigate the propagating and evanescent field contributions in the scattering of an electromagnetic field from a collection of interacting electric point dipoles. Having applications of scanning near-field optical microscopy (SNOM) in mind, we study three different geometries of dipoles placed close to a bulk surface. One of them is chosen to allow a direct comparison with the results recently put forward in the literature [J. Mod. Opt. 44, 327 (1997)] and to point out the discrepancies in the near zone between the held decompositions applied in that paper and in our work. The other two geometries have been selected to illustrate SNOM action in the illumination and collection modes. Within the point-dipole model we investigate the effects of the probe-dipole polarization on the propagating and evanescent fields in the sample-probe system during the scanning of the probe at different heights above the sample.

  • 11. Setala, T.
    et al.
    Kaivola, M.
    Friberg, Ari T.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Evanescent and propagating electromagnetic fields in scattering from point-dipole structures: reply to comment2002In: Journal of the Optical Society of America A, ISSN 0740-3232, Vol. 19, no 7, p. 1449-1451Article in journal (Refereed)
    Abstract [en]

    In this reply, we point out that Xiao's comment [J. Opt. Soc. Am. A 19, 1447-1448 (2002)] on our paper [J. Opt. Soc. Am. A 18, 678 (2001)] is based on groundless statements and misunderstandings.

  • 12. Shen, L. F.
    et al.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Analysis for the convergence problem of the plane-wave expansion method for photonic crystals2002In: Journal of the Optical Society of America A, ISSN 0740-3232, Vol. 19, no 5, p. 1021-1024Article in journal (Refereed)
  • 13.
    Su, Rong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Metrology and Optics.
    Ekberg, Peter
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Metrology and Optics.
    Leitner, Michael
    Mattsson, Lars
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Metrology and Optics.
    Accurate and automated image segmentation of 3D optical coherence tomography data suffering from low signal-to-noise levels2014In: Journal of the Optical Society of America A, ISSN 0740-3232, Vol. 31, no 12, p. 2551-2560Article in journal (Refereed)
    Abstract [en]

    Optical coherence tomography (OCT) has proven to be a useful tool for investigating internal structures in ceramic tapes, and the technique is expected to be important for roll-to-roll manufacturing. However, because of high scattering in ceramic materials, noise and speckles deteriorate the image quality, which makes automated quantitative measurements of internal interfaces difficult. To overcome this difficulty we present in this paper an innovative image analysis approach based on volumetric OCT data. The engine in the analysis is a 3D image processing and analysis algorithm. It is dedicated to boundary segmentation and dimensional measurement in volumetric OCT images, and offers high accuracy, efficiency, robustness, subpixel resolution, and a fully automated operation. The method relies on the correlation property of a physical interface and effectively eliminates pixels caused by noise and speckles. The remaining pixels being stored are the ones confirmed to be related to the target interfaces. Segmentation of tilted and curved internal interfaces separated by similar to 10 mu m in the Z direction is demonstrated. The algorithm also extracts full-field top-view intensity maps of the target interfaces for high-accuracy measurements in the X and Y directions. The methodology developed here may also be adopted in other similar 3D imaging and measurement technologies, e.g., ultrasound imaging, and for various materials.

  • 14.
    Yan, Wei
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Ruan, Zhichao
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Influence of geometrical perturbation at inner boundaries of invisibility cloaks2008In: Journal of the Optical Society of America A, ISSN 0740-3232, Vol. 25, no 4, p. 968-973Article in journal (Refereed)
    Abstract [en]

    The influence of a geometrical perturbation (5 at the inner boundaries of both cylindrical and spherical invisibility cloaks on invisibility performance is presented. The analytic solutions for such influence in the case of the general coordinate transformation are given. We show that the cylindrical cloak is more sensitive than a spherical cloak to such a perturbation. The difference results from the different asymptotic properties of eigen-functions for the cylindrical and spherical wave equations. In particular, the zeroth-order scattering coefficient for a cylindrical cloak determined by -1/ln(delta) converges to zero very slowly. The noticeable scattering induced by the slow convergence speed can be decreased by choosing appropriate coordinate transformation functions. More interestingly, the slow convergence can be overcome dramatically by putting a PEC (PMC) layer at the interior boundary of the cloak shell for TM (TE) wave.

  • 15. Yokota, M.
    et al.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Takenaka, T.
    Scattering of a Hermite-Gaussian beam field by a chiral sphere2001In: Journal of the Optical Society of America A, ISSN 0740-3232, Vol. 18, no 7, p. 1681-1689Article in journal (Refereed)
1 - 15 of 15
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