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Photothermal Effect in Plasmonic Nanostructures and its Applications
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
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 [en]
Plasmonic, Photothermal Effect, Silicon Photonics, Gold Nanoparticles
National Category
Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
URN: urn:nbn:se:kth:diva-143754ISBN: 978-91-7595-059-4 (print)OAI: oai:DiVA.org:kth-143754DiVA: diva2:708769
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
List of papers
1. Nanosecond Photothermal Effects in Plasmonic Nanostructures
Open this publication in new window or tab >>Nanosecond Photothermal Effects in Plasmonic Nanostructures
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.

Keyword
thermodynamic, photothermal, metamaterial absorber, nanoparticle reshaping
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-93651 (URN)10.1021/nn2050032 (DOI)000301945900071 ()2-s2.0-84859135597 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20120423

Available from: 2012-04-23 Created: 2012-04-23 Last updated: 2017-12-07Bibliographically approved
2. Ordered Au nanocrystals on a substrate formed by light-induced rapid annealing
Open this publication in new window or tab >>Ordered Au nanocrystals on a substrate formed by light-induced rapid annealing
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2014 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 6, no 3, 1756-1762 p.Article in journal (Refereed) Published
Abstract [en]

Light-induced rapid annealing (LIRA) is a widely used method to modify the morphology and crystallinity of noble metal nanoparticles, and the nanoparticles generally evolve into nanospheres. It is rather challenging to form faceted Au nanocrystals on a substrate using LIRA. Here the formation of spatially ordered Au nanocrystals using a continuous wave infrared laser is reported, assisted by a metamaterial perfect absorber. Faceted Au nanocrystals in truncated-octahedral or multi-twinned geometries can be obtained. The evolution of morphology and crystallinity of the Au nanoparticles during laser annealing is also revealed, where the crystal grain growth and the surface melting are shown to play key roles in nanocrystal formation. The evolution of morphology also gives the freedom of tuning the absorption spectrum of the metamaterial absorber. These findings provide a novel way for tailoring the morphology and crystallinity of metallic nanoparticles and may pave the way to fabricate refined nano-devices in many potential applications for optics, electronics, catalysis, surface-chemistry and biology.

Keyword
Gold Nanoparticles, Laser-Pulses, Arrays, Femtosecond, Fabrication, Absorber, Surfaces, Growth
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-141722 (URN)10.1039/c3nr05745c (DOI)000330041400069 ()2-s2.0-84892640438 (Scopus ID)
Funder
Swedish Foundation for Strategic Research Swedish Research Council
Note

QC 20140221

Available from: 2014-02-21 Created: 2014-02-21 Last updated: 2017-12-05Bibliographically approved
3. Photothermal reshaping of gold nanoparticles in a plasmonic absorber
Open this publication in new window or tab >>Photothermal reshaping of gold nanoparticles in a plasmonic absorber
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2011 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 19, no 15, 14726-14734 p.Article in journal (Refereed) Published
Abstract [en]

We experimentally demonstrate that a metamaterial nanostructure can have a localized heating response owing to plasmonic resonances in the near-infrared wavelength range (from 1.5 to 2 mu m). With a broadband nanosecond-pulse light, the temperature of composing gold particles in the nanostructure can be easily increased to over 900K within only several nanoseconds, resulting in re-shaping of the particles. The photothermal effect is elaborated with finite-element based numerical simulations. The absorption resonance can in principle be tailored with a great freedom by choosing appropriate metamaterial parameters. The light-induced heating in an artificial metamaterial can be potentially used for all-optical acute temperature tuning in a micro-environment, which may open new frontiers especially in nanotechnology and biotechnology.

Keyword
OPTICAL-PROPERTIES, FEMTOSECOND, NANORODS, HEAT, NANOSHELLS, PARTICLES, ABLATION, METALS
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-37264 (URN)10.1364/OE.19.014726 (DOI)000292877600104 ()2-s2.0-79960539232 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20110810

Available from: 2011-08-10 Created: 2011-08-08 Last updated: 2017-12-08Bibliographically approved
4. Photothermal switching of SOI-waveguide-based Mach-Zehnder interferometer with integrated plasmonic nanoheater
Open this publication in new window or tab >>Photothermal switching of SOI-waveguide-based Mach-Zehnder interferometer with integrated plasmonic nanoheater
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2014 (English)In: Plasmonics, ISSN 1557-1963, Vol. 9, no 5, 1197-1205 p.Article in journal (Refereed) Published
Abstract [en]

We theoretically and numerically investigate photothermal switching of a Mach-Zehnder interferometer (MZI) based on two Si waveguides integrated with plasmonic nanoheater. The nanoheater is a composite nanowire with Au/Al2O3/Au three-layer structure, which is designed to have a high-efficient optical absorption peak at wavelength of 1064 nm. Based on this finding, we further analyze a MZI built with two 40 μm-long symmetric waveguide branches, each integrated with a 20 μm-long nanoheater. The optical switching power of the MZI device is 190 mW (280 mW) for the capped (buried) channel waveguide, when pumped by a circular Gaussian beam with a waist of 10 μm. Alternatively, the switching power can be reduced to 38 mW (56 mW) by using an astigmatic Gaussian beam, with a semi-major axis of 10 μm and an aspect ratio of 5. The switching response time of the MZI is 0.7 μs (1.0 μs) for capped (buried) channel waveguide design. Our design opens a new route for optically driven non-contact optical on-off switching with sub-microsecond time response.

Place, publisher, year, edition, pages
Springer, 2014
National Category
Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-143674 (URN)10.1007/s11468-014-9731-2 (DOI)000341841500026 ()2-s2.0-84901514254 (Scopus ID)
Funder
Swedish Foundation for Strategic Research Swedish Research Council
Note

Updated from "Accepted" to "Published". QC 20141013

Available from: 2014-03-27 Created: 2014-03-27 Last updated: 2017-03-30Bibliographically approved
5. All-optical switching of silicon disk resonator based on photothermal effect in metal-insulator-metal absorber
Open this publication in new window or tab >>All-optical switching of silicon disk resonator based on photothermal effect in metal-insulator-metal absorber
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2014 (English)In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 39, no 15, 4431-4434 p.Article in journal (Refereed) Published
Abstract [en]

Efficient narrowband light absorption by a metal-insulator-metal (MIM) structure can lead to high-speed light-to-heat conversion at a micro-or nanoscale. Such a MIM structure can serve as a heater for achieving all-optical light control based on the thermo-optical (TO) effect. Here we experimentally fabricated and characterized a novel all-optical switch based on a silicon microdisk integrated with a MIM light absorber. Direct integration of the absorber on top of the microdisk reduces the thermal capacity of the whole device, leading to high-speed TO switching of the microdisk resonance. The measurement result exhibits a rise time of 2.0 mu s and a fall time of 2.6 mu s with switching power as low as 0.5 mW; the product of switching power and response time is only about 1.3 mW.mu s. Since no auxiliary elements are required for the heater, the switch is structurally compact, and its fabrication is rather easy. The device potentially can be deployed for new kinds of all-optical applications.

Keyword
Metal insulator boundaries, Silicon, All optical switch, All-optical switching, Direct integration, Light absorbers, Metal insulator metals, Metal-insulator-metal structures, Photothermal effects, Switching power
National Category
Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-143753 (URN)10.1364/OL.39.004431 (DOI)000339878900038 ()2-s2.0-84905014920 (Scopus ID)
Funder
Swedish Foundation for Strategic Research Swedish Research Council
Note

QC 20140901. Updated from manuscript to article in journal. Previous title: All-optical-switching in silicon disk resonator based on photothermal effect of metal-insulator-metal absorber

Available from: 2014-03-27 Created: 2014-03-27 Last updated: 2017-12-05Bibliographically approved
6. Photothermally tunable silicon microring-resonator-based optical add-drop filter
Open this publication in new window or tab >>Photothermally tunable silicon microring-resonator-based optical add-drop filter
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

A themro-optic (TO) silicon photonic add-drop filterwith small switching power and fast response is experimentallydemonstrated. We propose that metal-insulator-metal (MIM)absorbers can be integrated into the silicon TO devices, acting asan efficient and localized heat source. The MIM absorber designintroduces less thermal capacity to the device, comparing to theelectrically driven heater used in conventional TO devices. As a keyelement in silicon photonics, microring resonators have applicationin wavelength-division-multiplexing (WDM) devices, owning to theirunique spectrum properties. In this work, a silicon microring add-dropfilter is equipped with a MIM absorber. Experimentally, the deviceshows a measured optical response time of 5.0 μs and pumping powerderivative of the wavelength shift of 60 pm/mW.

National Category
Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-143750 (URN)
Funder
Swedish Foundation for Strategic Research Swedish Research Council
Note

QS 2014

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

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Citation style
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  • harvard1
  • ieee
  • modern-language-association-8th-edition
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  • en-US
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  • nn-NO
  • nn-NB
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More languages
Output format
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