Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Effects of surface plasmons in subwavelength metallic structures
KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The study of optical phenomena related to the strong electromagnetic response of noble metals (silver (Ag) and gold (Au) being most popular) over the last couple of decades has led to the emergence of a fast growing research area called plasmonics named after 'surface plasmons' which are electron density waves that propagate along the interface of a metal and a dielectric medium. Surface plasmons are formed by the coupling of light to the electrons on the metal surface subject to the fulfillment of certain physical conditions and they are bound to the metal surface. Depending on whether the metallic medium is a continuous film or a structure having dimensions less than or comparable to the wavelength of the exciting light, propagating or localized surface plasmons can be excited. The structure can be either a hole or an arbitrary pattern in a metal film, or a metallic particle. An array of subwavelength structures can behave as an effective homogeneous medium to incident light and this is the basis of a new class of media known as metamaterials. Metallic metamaterials enable one to engineer the electromagnetic response to  incident light and provide unconventional optical properties like negative refractive index as one prominent example. Metamaterials exhibiting negative index (also called negative index materials (NIMs)) open the door for super resolution imaging  and development of invisibility cloaks. However, the only problem affecting the utilization of plasmonic media to their fullest potential is the intrinsic loss of the metal, and it becomes a major issue especially at visible-near infrared (NIR) frequencies.

The frequency of the surface plasmon is the same as that of the exciting light but its wavelength could be as short as that of X-rays. This property allows light of a given optical frequency to be conned into very small volumes via subwave lengthmetallic structures, that can be used to develop ecient sensors, solar cells, antennas and ultrasensitive molecular detectors to name a few applications. Also, interaction of surface plasmons excited in two or more metallic subwavelength structures in close proximity inuences the far-eld optical properties of the overall coupled system. Some eects of plasmonic interaction in certain coupled particles include polarization conversion, optical activity and transmission spectra mimicking electromagnetically-induced transparency (EIT) as observed in gas based atomicsy stems.

In this thesis, we mainly focus on the optical properties of square arrays of certain plasmonic structures popularly researched in the last decade. The structures considered are as follows: (1) subwavelength holes of a composite hole-shape providing superior near-eld enhancement such as two intersecting circles (called' double hole') in an optically thick Au/Ag lm, (2) double layer shnets, (3) subwavelength U-shaped particles and (4) rectangular bars. The entire work is based on electromagnetic simulations using time and frequency domain methods.

Au/Ag lms with periodic subwavelength holes provide extraordinarily high transmission of light at certain wavelengths much larger than the dimension of the perforations or holes. The spectral positions of the maxima depend on the shape of the hole and the intra-hole medium, thereby making such lms function as a refractive index sensor in the transmission mode. The sensing performance of the double-hole geometry is analyzed in detail and compared to rectangular holes.

Fishnet metamaterials are highly preferred when it comes to constructing a NIM at optical frequencies. A shnet design that theoretically oers a negative refractive index with least losses at telecommunication wavelengths (1.4 1.5 microns) is presented.

U-shaped subwavelength metallic particles, in particular single-slit split-ring resonators (SSRRs), provide a large negative response to the magnetic eld of light at a specic resonance frequency. The spectral positions of the structural resonances of the U-shaped particle can be found from its array far field transmission spectrum at normal incidence. An effort is made to clarify our understanding of these resonances with the help of localized surface plasmon modes excited in the overall particle. From an application point of view, it is found that a planar square array of SSRRs eectively functions as an optical half-wave waveplate at the main resonance frequency by creating a polarization in transmission that is orthogonal to that of incident light. A similar waveplate eect can be obtained purely by exploiting the near-eld interaction of dierently oriented neighbouring SSRRs. The physical reasons behind polarization conversion in dierent SSRR-array systems are discussed.

A rectangular metallic bar having its dipolar resonance in the visible-NIR is called a nanoantenna, owing to its physical length in the order of nanometers. The excitation of localized surface plasmons, metal dispersion and the geometry of the rectangular nanoantenna make an analytical estimation of the physical length of the antenna from the desired dipolar resonance dicult. A practical map of simulated resonance values corresponding to a variation in geometrical parameters of Au bar is presented. A square array of a coupled plasmonic system comprising of three nanoantennas provides a net transmission response that mimicks the EIT effect. The high transmission spectral window possesses a peculiar dispersion profile that enables light with frequencies in that region to be slowed down. Two popular designs of such plasmonic EIT systems are numerically characterized and compared.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , xiii, 67 p.
Series
Trita-ICT/MAP AVH, ISSN 1653-7610 ; 2012:17
Keyword [en]
suface plasmons, extraordinary transmission, metamaterials, shnets, split-ring resonators, plasmon-induced EIT, optical antennas, plasmonics
National Category
Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:kth:diva-103613ISBN: 978-91-7501-501-9 (print)OAI: oai:DiVA.org:kth-103613DiVA: diva2:560960
Public defence
2012-11-05, C22, Electrum Building 229, Kista, 13:00 (English)
Opponent
Supervisors
Note

QC 20121017

Available from: 2012-10-17 Created: 2012-10-16 Last updated: 2012-10-17Bibliographically approved
List of papers
1. Impact of apexes on the resonance shift in double hole nanocavities
Open this publication in new window or tab >>Impact of apexes on the resonance shift in double hole nanocavities
2010 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 18, no 1, 193-203 p.Article in journal (Refereed) Published
Abstract [en]

The transmission of light through metallic films with periodic double nanoholes is studied using vectorial three-dimensional finite element method. Special emphasis is given on understanding different transmission resonances arising in gold and silver films with periodic sub-wavelength holes of different shapes. The spectral shift of the hole-shape resonance resulting from a variation of the hole refractive index is analyzed for a double nanohole geometry in the transmission mode using numerical simulations. Specifically, the role of field enhancement at the apexes of the double nanohole in the sensing of medium within the hole cavity is pointed out and discussed. The presence of sharp apexes within the double nanoholes significantly improves the resonance sensitivity as compared to rectangular holes of comparable area. Impact of possible manufacturing errors on the overall sensitivity is also characterized. Robustness and a relatively simple fabrication procedure make these kinds of refractive index sensors practically attractive.

Keyword
extraordinary optical-transmission, arrays, spectroscopy, sensors, metals, film
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-19100 (URN)10.1364/OE.18.000193 (DOI)000273249400025 ()2-s2.0-73549103366 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
2. Loss optimization in double fishnet metamaterials at telecommunication wavelengths
Open this publication in new window or tab >>Loss optimization in double fishnet metamaterials at telecommunication wavelengths
2011 (English)In: JOURNAL OF THE EUROPEAN OPTICAL SOCIETY-RAPID PUBLICATIONS, ISSN 1990-2573, Vol. 6, 11008- p.Article in journal (Refereed) Published
Abstract [en]

A hole shape optimization study was made for a double fishnet metamaterial producing a negative index of refraction within 1.4 - 1.5 mu m. It is found that within these wavelengths, elliptical holes offer lower losses as compared to rectangular ones and theoretically produce the best figure of merit (FOM) of approximately 6.

Keyword
metamaterials, plasmonics, metal optics
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-32229 (URN)10.2971/jeos.2011.11008 (DOI)000288654800002 ()2-s2.0-84858325717 (Scopus ID)
Note
QC 20110530Available from: 2011-05-30 Created: 2011-04-11 Last updated: 2012-10-17Bibliographically approved
3. Transmission resonances in periodic U-shaped metallic nanostructures
Open this publication in new window or tab >>Transmission resonances in periodic U-shaped metallic nanostructures
2010 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 18, no 17, 17719-17728 p.Article in journal (Refereed) Published
Abstract [en]

The spectral response of crescent-like metallic nanostructures, a sub-class of U-shaped split-ring resonators, on a glass substrate at normal incidence is studied numerically. Also, the interpretation of transmission resonances arising from periodic conventional standard split-ring resonators with rectangular edges (SSRR) at normal incidence is revisited. In particular, we focus on one specific transmission resonance which is present for nano-crescents (NC) but absent in the case of SSRRs used for metamaterials. It is proposed that for a U-shaped metallic structure of arbitrary geometry, coupling of plasmonic eigen modes at all the surfaces of the three-dimensional structure is essential to be considered. The manner in which the coupling takes place between plasmonic modes at all the surfaces of the three-dimensional structure is what completely characterizes transmission resonances, and it is unique for each given resonance. (C) 2010 Optical Society of America

National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-26842 (URN)000281054400015 ()2-s2.0-77956354494 (Scopus ID)
Note
QC 20101206Available from: 2010-12-06 Created: 2010-11-29 Last updated: 2017-12-12Bibliographically approved
4. Linear birefringence in split-ring resonators
Open this publication in new window or tab >>Linear birefringence in split-ring resonators
2012 (English)In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 37, no 11, 2043-2045 p.Article in journal (Refereed) Published
Abstract [en]

We study polarization-dependent transmission of light through arrays of single-slit split-ring resonator (SSRR) based systems at normal incidence using finite integration time domain (FITD) and finite element methods (FEM). It is found that a conventional planar array of SSRRs acts as an effective optical wave plate at certain polarizations of incident light. The effect is attributed to the intrinsic linear birefringence of individual SSRRs. A comparison is made with other split-ring resonator-based systems exhibiting wave-plate-like properties due to inter-SSRR coupling.

National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-98945 (URN)10.1364/OL.37.002043 (DOI)000305085000089 ()2-s2.0-84863678938 (Scopus ID)
Note
QC 20120710Available from: 2012-07-10 Created: 2012-07-05 Last updated: 2017-12-07Bibliographically approved
5. Interpreting the dipolar plasmon resonance of rectangular metallic nanoantennas
Open this publication in new window or tab >>Interpreting the dipolar plasmon resonance of rectangular metallic nanoantennas
(English)In: Plasmonics, ISSN 1557-1955, E-ISSN 1557-1963Article in journal (Other academic) Submitted
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-103621 (URN)
Note

QCR 20161212

Available from: 2012-10-16 Created: 2012-10-16 Last updated: 2017-12-07Bibliographically approved
6. Effective tunability and realistic estimates of group index in plasmonic metamaterials exhibiting electromagnetically induced transparency
Open this publication in new window or tab >>Effective tunability and realistic estimates of group index in plasmonic metamaterials exhibiting electromagnetically induced transparency
2011 (English)In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 50, no 21, 3958-3961 p.Article in journal (Refereed) Published
Abstract [en]

We study the phenomenon of the electromagnetically induced transparency in planar and stacked plasmonic metamaterials (MMs) using the finite integration time domain and finite element methods. For such structures, the dependence of the tunability of the inherent structural resonances on geometry design is clarified. We also analyze the performance of recently demonstrated MM designs in terms of the achievable group refractive index and losses, which are of great interest for slowing light applications.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-37259 (URN)10.1364/AO.50.003958 (DOI)000292970600027 ()2-s2.0-79960647666 (Scopus ID)
Note
QC 20110810Available from: 2011-08-10 Created: 2011-08-08 Last updated: 2017-12-08Bibliographically approved

Open Access in DiVA

srithesis(3279 kB)4148 downloads
File information
File name FULLTEXT01.pdfFile size 3279 kBChecksum SHA-512
0564b03e3fea62a4e72ac8f3460c96ca8154506db57ae60a20db5d9313c08fffad0cc09b3fae3591c20d1d3021e1a9f5bd24fd3a7d91b6b5a37167382eee9cbe
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Iyer, Srinivasan
By organisation
Optics
Atom and Molecular Physics and Optics

Search outside of DiVA

GoogleGoogle Scholar
Total: 4148 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 648 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf