Finite difference time domain studies on sub-wavelength aperture structures

Dissertation

Juuso Olkkonen

Research output: ThesisDissertationCollection of Articles

1 Citation (Scopus)

Abstract

Modern optical technologies, such as microscopy, data storage, and lithography, require optical light spots with lateral dimensions that are much smaller than the wavelength of incident light. In free space, no such light spots are known to exist due to diffraction - a phenomenon exhibited by all electromagnetic waves. In this thesis, the formation of highly confined light spots by means of sub-wavelength aperture structures in metal films is studied via finite difference time domain (FDTD) simulations. It is observed that the otherwise weak light transmittance through sub-wavelength apertures can be remarkably enhanced by filling the aperture by a high refractive index material. The transmittance through the aperture can be further increased by introducing surface corrugations that couple the light impinging outside the aperture into surface waves propagating along the film plane. It is also demonstrated that significant transmission enhancement is obtained by inserting a semitransparent metal film in front of the aperture at the distance that fulfills the Fabry-Pérot resonance condition. The gap between the semitransparent metal film and the film containing the aperture works as a light trapping cavity, enhancing the amplitude of the illuminating monochromatic plane wave. A simple scattered field technique that allows FDTD modeling scattering of obliquely incident plane waves from objects residing in a dispersive multilayer background structure is introduced in this work. The technique is applied to study how a surface plasmon polariton field that is excited in the traditional Otto configuration couples to a 100 nm wide slit in a metal film. As an application example of the aperture structures, the effect of the embedded non-linear aperture layer in the traditional DVD disk on the data storage density is studied via the 3D FDTD method. It is found that the aperture layer enables distinguishing of data marks smaller than 100 nanometers in the far field, making it possible to increase the storage density of DVD disks by a factor of four.
Original languageEnglish
QualificationDoctor Degree
Awarding Institution
  • University of Oulu
Award date12 Nov 2010
Place of PublicationEspoo
Publisher
Print ISBNs978-951-38-7410-0
Electronic ISBNs978-951-38-7411-7
Publication statusPublished - 2010
MoE publication typeG5 Doctoral dissertation (article)

Fingerprint

apertures
wavelengths
metal films
data storage
transmittance
plane waves
theses
finite difference time domain method
polaritons
illuminating
surface waves
slits
far fields
electromagnetic radiation
lithography
trapping
refractivity
microscopy
cavities
augmentation

Keywords

  • finite difference time domain method
  • apertures in metal films
  • surface plasmon polaritons
  • data storage

Cite this

Olkkonen, J. (2010). Finite difference time domain studies on sub-wavelength aperture structures: Dissertation. Espoo: VTT Technical Research Centre of Finland.
Olkkonen, Juuso. / Finite difference time domain studies on sub-wavelength aperture structures : Dissertation. Espoo : VTT Technical Research Centre of Finland, 2010. 134 p.
@phdthesis{afef2851f874489fb3ba71db56fbed0b,
title = "Finite difference time domain studies on sub-wavelength aperture structures: Dissertation",
abstract = "Modern optical technologies, such as microscopy, data storage, and lithography, require optical light spots with lateral dimensions that are much smaller than the wavelength of incident light. In free space, no such light spots are known to exist due to diffraction - a phenomenon exhibited by all electromagnetic waves. In this thesis, the formation of highly confined light spots by means of sub-wavelength aperture structures in metal films is studied via finite difference time domain (FDTD) simulations. It is observed that the otherwise weak light transmittance through sub-wavelength apertures can be remarkably enhanced by filling the aperture by a high refractive index material. The transmittance through the aperture can be further increased by introducing surface corrugations that couple the light impinging outside the aperture into surface waves propagating along the film plane. It is also demonstrated that significant transmission enhancement is obtained by inserting a semitransparent metal film in front of the aperture at the distance that fulfills the Fabry-P{\'e}rot resonance condition. The gap between the semitransparent metal film and the film containing the aperture works as a light trapping cavity, enhancing the amplitude of the illuminating monochromatic plane wave. A simple scattered field technique that allows FDTD modeling scattering of obliquely incident plane waves from objects residing in a dispersive multilayer background structure is introduced in this work. The technique is applied to study how a surface plasmon polariton field that is excited in the traditional Otto configuration couples to a 100 nm wide slit in a metal film. As an application example of the aperture structures, the effect of the embedded non-linear aperture layer in the traditional DVD disk on the data storage density is studied via the 3D FDTD method. It is found that the aperture layer enables distinguishing of data marks smaller than 100 nanometers in the far field, making it possible to increase the storage density of DVD disks by a factor of four.",
keywords = "finite difference time domain method, apertures in metal films, surface plasmon polaritons, data storage",
author = "Juuso Olkkonen",
note = "Project code: 35768",
year = "2010",
language = "English",
isbn = "978-951-38-7410-0",
series = "VTT Publications",
publisher = "VTT Technical Research Centre of Finland",
number = "745",
address = "Finland",
school = "University of Oulu",

}

Olkkonen, J 2010, 'Finite difference time domain studies on sub-wavelength aperture structures: Dissertation', Doctor Degree, University of Oulu, Espoo.

Finite difference time domain studies on sub-wavelength aperture structures : Dissertation. / Olkkonen, Juuso.

Espoo : VTT Technical Research Centre of Finland, 2010. 134 p.

Research output: ThesisDissertationCollection of Articles

TY - THES

T1 - Finite difference time domain studies on sub-wavelength aperture structures

T2 - Dissertation

AU - Olkkonen, Juuso

N1 - Project code: 35768

PY - 2010

Y1 - 2010

N2 - Modern optical technologies, such as microscopy, data storage, and lithography, require optical light spots with lateral dimensions that are much smaller than the wavelength of incident light. In free space, no such light spots are known to exist due to diffraction - a phenomenon exhibited by all electromagnetic waves. In this thesis, the formation of highly confined light spots by means of sub-wavelength aperture structures in metal films is studied via finite difference time domain (FDTD) simulations. It is observed that the otherwise weak light transmittance through sub-wavelength apertures can be remarkably enhanced by filling the aperture by a high refractive index material. The transmittance through the aperture can be further increased by introducing surface corrugations that couple the light impinging outside the aperture into surface waves propagating along the film plane. It is also demonstrated that significant transmission enhancement is obtained by inserting a semitransparent metal film in front of the aperture at the distance that fulfills the Fabry-Pérot resonance condition. The gap between the semitransparent metal film and the film containing the aperture works as a light trapping cavity, enhancing the amplitude of the illuminating monochromatic plane wave. A simple scattered field technique that allows FDTD modeling scattering of obliquely incident plane waves from objects residing in a dispersive multilayer background structure is introduced in this work. The technique is applied to study how a surface plasmon polariton field that is excited in the traditional Otto configuration couples to a 100 nm wide slit in a metal film. As an application example of the aperture structures, the effect of the embedded non-linear aperture layer in the traditional DVD disk on the data storage density is studied via the 3D FDTD method. It is found that the aperture layer enables distinguishing of data marks smaller than 100 nanometers in the far field, making it possible to increase the storage density of DVD disks by a factor of four.

AB - Modern optical technologies, such as microscopy, data storage, and lithography, require optical light spots with lateral dimensions that are much smaller than the wavelength of incident light. In free space, no such light spots are known to exist due to diffraction - a phenomenon exhibited by all electromagnetic waves. In this thesis, the formation of highly confined light spots by means of sub-wavelength aperture structures in metal films is studied via finite difference time domain (FDTD) simulations. It is observed that the otherwise weak light transmittance through sub-wavelength apertures can be remarkably enhanced by filling the aperture by a high refractive index material. The transmittance through the aperture can be further increased by introducing surface corrugations that couple the light impinging outside the aperture into surface waves propagating along the film plane. It is also demonstrated that significant transmission enhancement is obtained by inserting a semitransparent metal film in front of the aperture at the distance that fulfills the Fabry-Pérot resonance condition. The gap between the semitransparent metal film and the film containing the aperture works as a light trapping cavity, enhancing the amplitude of the illuminating monochromatic plane wave. A simple scattered field technique that allows FDTD modeling scattering of obliquely incident plane waves from objects residing in a dispersive multilayer background structure is introduced in this work. The technique is applied to study how a surface plasmon polariton field that is excited in the traditional Otto configuration couples to a 100 nm wide slit in a metal film. As an application example of the aperture structures, the effect of the embedded non-linear aperture layer in the traditional DVD disk on the data storage density is studied via the 3D FDTD method. It is found that the aperture layer enables distinguishing of data marks smaller than 100 nanometers in the far field, making it possible to increase the storage density of DVD disks by a factor of four.

KW - finite difference time domain method

KW - apertures in metal films

KW - surface plasmon polaritons

KW - data storage

M3 - Dissertation

SN - 978-951-38-7410-0

T3 - VTT Publications

PB - VTT Technical Research Centre of Finland

CY - Espoo

ER -

Olkkonen J. Finite difference time domain studies on sub-wavelength aperture structures: Dissertation. Espoo: VTT Technical Research Centre of Finland, 2010. 134 p.