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Nanosecond Photothermal Effects in Plasmonic Nanostructures
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.ORCID iD: 0000-0002-3368-9786
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
2012 (English)In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 6, no 3, 2550-2557 p.Article in journal (Refereed) Published
Abstract [en]

Photothermal effects in plasmonic nanostructures have great potentials in applications for photothermal cancer therapy, optical storage, thermo-photovoltaics, etc. However, the transient temperature behavior of a nanoscale material system during an ultrafast photothermal process has rarely been accurately investigated. Here a heat transfer model is constructed to investigate the temporal and spatial variation of temperature in plasmonic gold nanostructures. First, as a benchmark scenario, we study the light-induced heating of a gold nanosphere in water and calculate the relaxation time of the nanosphere excited by a modulated light. Second, we investigate heating and reshaping of gold nanoparticles in a more complex metamaterial absorber structure induced by a nanosecond pulsed light. The model shows that the temperature of the gold nanoparticles can be raised from room temperature to >795 K in just a few nanoseconds with a low light luminance, owing to enhanced light absorption through strong plasmonic resonance. Such quantitative predication of temperature change, which Is otherwise formidable to measure experimentally, can serve as an excellent guideline for designing devices for ultrafast photothermal applications.

Place, publisher, year, edition, pages
2012. Vol. 6, no 3, 2550-2557 p.
Keyword [en]
thermodynamic, photothermal, metamaterial absorber, nanoparticle reshaping
National Category
Other Physics Topics
Identifiers
URN: urn:nbn:se:kth:diva-93651DOI: 10.1021/nn2050032ISI: 000301945900071Scopus ID: 2-s2.0-84859135597OAI: oai:DiVA.org:kth-93651DiVA: diva2:517452
Funder
Swedish Research Council
Note

QC 20120423

Available from: 2012-04-23 Created: 2012-04-23 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Fabrication and Characterization of Plasmonic Nanophotonic Absorbers and Waveguides
Open this publication in new window or tab >>Fabrication and Characterization of Plasmonic Nanophotonic Absorbers and Waveguides
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Plasmonics is a promising field of nanophotonics dealing with light interaction with metallic nanostructures. In such material systems, hybridizationof photons and collective free-electron oscillation can result in sub-wavelength light confinement. The strong light-matter interaction can be harnessed for,among many applications, high-density photonic integration, metamaterial design, enhanced nonlinear optics, sensing etc. In the current thesis work, we focus on experimental fabrication and characterization of planar plasmonic metamaterials and waveguide structures. The samples are fabricated based on the generic electron beam lithography and characterizations are done with our home-made setups. Mastering and refinement of fabrication techniques as well as setting up the characterization tools have constituted as a majorpart of the thesis work. In particular, we experimentally realized a plasmonic absorber based on a 2D honeycomb array of gold nano-disks sitting on top of a reflector through a dielectric spacer. The absorber not only exhibits an absorption peak which is owing to localized surface plasmon resonance and is insensitive to incidence’s angle or polarization, but also possesses an angle- and polarization-sensitive high-order absorption peak with a narrow bandwidth. We also demonstrated that the strong light absorption in such plasmonic absorbers can be utilized to photothermally re-condition the geometry of gold nanoparticles. The nearly perfect absorption capability of our absorbers promises a wide range of potential applications, including thermal emitter, infrared detectors, and sensors etc. We also fabricated a plasmonic strip waveguide in a similar metal-insulator-metal structure. The strip waveguide has a modal confinement slightly exceeding that of the so-called plasmonic slot waveguide. We further thermally annealed the waveguide. It is observed that the propagation loss at 980 nm has been decreased significantly,which can be attributed to the improvement in gold quality after thermal annealing.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. x, 55 p.
Series
TRITA-ICT/MAP AVH, ISSN 1653-7610 ; 2014:02
Keyword
Nanophotonics, plasmonics, fabrication
National Category
Nano Technology
Research subject
SRA - ICT
Identifiers
urn:nbn:se:kth:diva-140844 (URN)978-91-7501-995-6 (ISBN)
Public defence
2014-02-27, Sal/hall D, Forum, KTH-ICT, Isafjordsgatan 39, Kista, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Foundation for Strategic Research
Note

QC 20140203

Available from: 2014-02-03 Created: 2014-01-31 Last updated: 2014-02-03Bibliographically approved
2. Photothermal Effect in Plasmonic Nanostructures and its Applications
Open this publication in new window or tab >>Photothermal Effect in Plasmonic Nanostructures and its Applications
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

  Plasmonic resonances are characterized by enhanced optical near field and subwavelength power confinement. Light is not only scattered but also simultaneously absorbed in the metal nanostructures. With proper structural design, plasmonic-enhanced light absorption can generate nanoscopically confined heat power in metallic nanostructures, which can even be temporally modulated by varying the pump light. These intrinsic characters of plasmonic nanostructures are investigated in depth in this thesis for a range of materials and nanophotonic applications.

  The theoretical basis for the photothermal phenomenon, including light absorption, heat generation, and heat conduction, is coherently summarized and implemented numerically based on finite-element method. Our analysis favours disk-pair and particle/dielectric-spacer/metal-film nanostructures for their high optical absorbance, originated from their antiparallel dipole resonances.

  Experiments were done towards two specific application directions. First, the manipulation of the morphology and crystallinity of Au nanoparticles (NPs) in plasmonic absorbers by photothermal effect is demonstrated. In particular, with a nanosecond-pulsed light, brick-shaped Au NPs are reshaped to spherical NPs with a smooth surface; while with a 10-second continuous wave laser, similar brick-shaped NPs can be annealed to faceted nanocrystals. A comparison of the two cases reveals that pumping intensity and exposure time both play key roles in determining the morphology and crystallinity of the annealed NPs.

  Second, the attempt is made to utilize the high absorbance and localized heat generation of the metal-insulator-metal (MIM) absorber in Si thermo-optic switches for achieving all-optical switching/routing with a small switching power and a fast transient response. For this purpose, a numerical study of a Mach-Zehnder interferometer integrated with MIM nanostrips is performed. Experimentally, a Si disk resonator and a ring-resonator-based add-drop filter, both integrated with MIM film absorbers, are fabricated and characterized. They show that good thermal conductance between the absorber and the Si light-guiding region is vital for a better switching performance.

  Theoretical and experimental methodologies presented in the thesis show the physics principle and functionality of the photothermal effect in Au nanostructures, as well as its application in improving the morphology and crystallinity of Au NPs and miniaturized all-optical Si photonic switching devices.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. xvi, 94 p.
Series
TRITA-ICT/MAP AVH, ISSN 1653-7610 ; 2014:04
Keyword
Plasmonic, Photothermal Effect, Silicon Photonics, Gold Nanoparticles
National Category
Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-143754 (URN)978-91-7595-059-4 (ISBN)
Public defence
2014-04-22, Sal/hall D, KTH-ICT, Isafjordsgatan 39, Kista, 14:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council, 63183
Note

QC 20140331

Available from: 2014-03-31 Created: 2014-03-27 Last updated: 2014-03-31Bibliographically approved

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