The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Electromagnetic Fields in Nanoscale Structures: Effects of Polarization and Spatial Coherence

Jari Lindberg

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Engineering Physics and Mathematics for public examination and debate in Large Seminar Hall of Micronova at Helsinki University of Technology (Espoo, Finland) on the 9th of November, 2007, at 12 noon.

Overview in PDF format (ISBN 978-951-22-9027-7)   [691 KB]
Dissertation is also available in print (ISBN 978-951-22-9026-0)

Abstract

In this thesis electromagnetic near fields in nanoscale structures are investigated. The optical near field is characterized by a strong presence of evanescent (non-radiative) waves which are significant only within the distance of the wavelength of light from the surface of a light emitting or scattering object. These waves play an essential role in the design and characterization of components for nanophotonics and exhibit phenomena not encountered in the conventional far-field optics.

In this thesis, specific optical systems at sub-wavelength scale are studied. In two of them the electromagnetic field is assumed to be deterministic whereas in two other systems the random nature of light is considered. One specific aim of this work is to assess the role of partial polarization and partial spatial coherence in electromagnetic near fields. This type of analysis necessitates the coherence theory of general, non-planar, three-dimensional (3D) electromagnetic fields which has not been available until very recently. The new concepts of electromagnetic coherence theory for 3D fields, such as 3D degree of polarization, electromagnetic degree of coherence, and electromagnetic theory of coherent modes, are applied to study partial polarization and partial spatial coherence of random near fields. Furthermore, the first explicit 3D coherent-mode representation is derived for a certain type of electromagnetic fields.

The topics which are included in this thesis are as follows: Transmission of partially polarized light through a scanning near-field probe tip, is studied in terms of the 3D degree of polarization. The enhanced transmission of light through a single sub-wavelength slit on a metal film is investigated, and the resonance behavior of its transmission spectrum is analyzed. The electromagnetic coherence theory is applied to study surface plasmon resonances in metallic nanocylinders, and their effect on the 3D degree of polarization, the electromagnetic degree of coherence, as well as on the electromagnetic energy transfer in the optical near field is assessed. Also the fluorescence resonance energy transfer (FRET) mediated by plasmon resonant metallic nanoparticles is addressed.

This thesis consists of an overview and of the following 5 publications:

  1. J. Lindberg, T. Setälä, M. Kaivola, and A. T. Friberg, Degree of polarization in light transmission through a near-field probe, Journal of Optics A: Pure and Applied Optics 6, S59-S63 (2004). © 2004 Institute of Physics Publishing. By permission.
  2. J. Lindberg, K. Lindfors, T. Setälä, M. Kaivola, and A. T. Friberg, Spectral analysis of resonant transmission of light through a single sub-wavelength slit, Optics Express 12, 623-632 (2004). © 2004 Optical Society of America (OSA). By permission.
  3. T. Setälä, J. Lindberg, K. Blomstedt, J. Tervo, and A. T. Friberg, Coherent-mode representation of a statistically homogeneous and isotropic electromagnetic field in spherical volume, Physical Review E 71, 036618 (2005). © 2005 American Physical Society. By permission.
  4. J. Lindberg, T. Setälä, M. Kaivola, and A. T. Friberg, Spatial coherence effects in light scattering from metallic nanocylinders, Journal of the Optical Society of America A 23, 1349-1358 (2006). © 2006 Optical Society of America (OSA). By permission.
  5. J. Lindberg, K. Lindfors, T. Setälä, and M. Kaivola, Dipole-dipole interaction between molecules mediated by a chain of silver nanoparticles, Journal of the Optical Society of America A 24, 3427-3431 (2007). © 2007 Optical Society of America (OSA). By permission.

Keywords: optical near field, evanescent wave, surface plasmon, polarization, electromagnetic coherence

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© 2007 Helsinki University of Technology

Last update 2011-05-26