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Exciton-plasmon interactions in metal-semiconductor nanostructures
KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Semiconductor quantum dots and metal nanoparticles feature very strong light-matter interactions, which has led to their use in many photonic applications such as photodetectors, biosensors, components for telecommunications etc.Under illumination both structures exhibit collective electron-photon resonances, described in the frameworks of quasiparticles as exciton-polaritons for semiconductors and surface plasmon-polaritons for metals.To date these two approaches to controlling light interactions have usually been treated separately, with just a few simple attempts to consider exciton-plasmon interactions in a system consisting of both semiconductor and metal nanostructures.In this work, the exciton-polaritons and surface \\plasmon-polaritons are first considered separately, and then combined using the Finite Difference Time Domain numerical method coupled with a master equation for the exciton-polariton population dynamics.To better understand the properties of excitons and plasmons, each quasiparticle is used to investigate two open questions - the source of the Stokes shift between the absorption and luminescence peaks in quantum dots, and the source of the photocurrent increase in quantum dot infrared photodetectors coated by a thin metal film with holes. The combined numerical method is then used to study a system consisting of multiple metal nanoparticles close to a quantum dot, a system which has been predicted to exhibit quantum dot-induced transparency, but is demonstrated to just have a weak dip in the absorption.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , viii, 50 p.
Series
Trita-BIO-Report, ISSN 1654-2312 ; 2012:4
Keyword [en]
plasmons, excitons, quantum dots, nanoparticles, FDTD, surface plasmon polaritons, QDIP, quantum dot infrared photodetector, polaritons
National Category
Nano Technology Theoretical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-93306ISBN: 978-91-7501-301-5 (print)OAI: oai:DiVA.org:kth-93306DiVA: diva2:515634
Public defence
2012-04-26, B2, Brinellvägen 23, KTH, Stockholm, 14:00 (English)
Opponent
Supervisors
Funder
Swedish e‐Science Research Center
Note

QC 20120417

Available from: 2012-04-17 Created: 2012-04-13 Last updated: 2013-04-09Bibliographically approved
List of papers
1. Exciton Polariton Contribution to the Stokes Shift in Colloidal Quantum Dots
Open this publication in new window or tab >>Exciton Polariton Contribution to the Stokes Shift in Colloidal Quantum Dots
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2011 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 13, 5286-5293 p.Article in journal (Refereed) Published
Abstract [en]

We study the exciton polariton contribution to the Stokes shift in colloidal quantum dots (QDs). By detailed quantum mechanical description of light-matter interaction and temporal analysis of incident electromagnetic field across the QD using the finite-difference time-domain method, we have shown that the optical excitation of an exciton in the QD and its coupling with the excitation radiation (i.e., exciton polariton) induce strong variations in the dielectric constant of the QD which contribute significantly to the Stokes shift and cause modifications 50 in the absorption spectrum that agrees well with experiments.

Keyword
CDS NANOCRYSTALS, DEPOSITION, ENERGY, FILMS, DARK
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-32622 (URN)10.1021/jp109608t (DOI)000288885900014 ()2-s2.0-79953677832 (Scopus ID)
Note

QC 20110419

Available from: 2011-04-19 Created: 2011-04-18 Last updated: 2017-12-11Bibliographically approved
2. Dynamic optical response of an excitonic quantum dot studied by solving the self-consistent Maxwell-Schrodinger equations nonperturbatively
Open this publication in new window or tab >>Dynamic optical response of an excitonic quantum dot studied by solving the self-consistent Maxwell-Schrodinger equations nonperturbatively
2010 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 82, no 24, 245305- p.Article in journal (Refereed) Published
Abstract [en]

The optical excitation of a quantum dot in real-world working conditions is studied by self-consistent solution of the time-dependent Schrodinger equation coupled to the Maxwell equations by the finite-difference time domain method, resulting in a polarization modification which is the basis for the enhanced light-matter interaction in many nanoscale devices. The commonly used perturbational analysis approach is compared to the results and found to be an acceptable approximation even for intense femtosecond pulse excitations where using the perturbative approach is risky. This allows device designers and simulators to confidently use the simpler and faster perturbative results in their work.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-30936 (URN)10.1103/PhysRevB.82.245305 (DOI)000286895100004 ()2-s2.0-78651241334 (Scopus ID)
Note
QC 20110309Available from: 2011-03-09 Created: 2011-03-07 Last updated: 2017-12-11Bibliographically approved
3. Increased photocurrent in quantum dot infrared photodetector by subwavelength hole array in metal thin film
Open this publication in new window or tab >>Increased photocurrent in quantum dot infrared photodetector by subwavelength hole array in metal thin film
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2010 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 96, no 23, 231110- p.Article in journal (Refereed) Published
Abstract [en]

Photocurrent enhancement in quantum dot (QD) infrared photodetector (QDIP) with an optical grating of subwavelength hole array in a thin metal film has been studied by calculating the transmission and diffraction of the infrared optical field through the grating and the light-matter interaction between the transmitted optical field and electrons confined in the QD. It is shown that due to the small aspect ratio of realistic QDs in QDIPs, the light diffraction due to the surface plasmon effect at the metal-semiconductor surface and the photonic subwavelength hole array structure is dominant in increasing the photocurrent.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-27515 (URN)10.1063/1.3449117 (DOI)000278695900010 ()2-s2.0-77953508938 (Scopus ID)
Note
QC 20110111Available from: 2011-01-11 Created: 2010-12-13 Last updated: 2017-12-11Bibliographically approved
4. Time-resolved photocurrents in quantum well/dot infrared photodetectors with different optical coupling structures
Open this publication in new window or tab >>Time-resolved photocurrents in quantum well/dot infrared photodetectors with different optical coupling structures
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2012 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 100, no 4, 043502- p.Article in journal (Refereed) Published
Abstract [en]

Temporal developments of photocurrents excited by an infrared radiation pulse in quantum well/dot infrared photodetectors with different optical coupling structures have been theoretically studied. It is shown that the light diffraction in a conventional reflective grating structure is a near-field effect containing severe crosstalk from neighboring pixels. A concave reflector not only eliminates the crosstalk but also strongly diffracts and focuses the incident electric field into deep active layers, which significantly increases the photocurrents in the photodetectors.

National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-91623 (URN)10.1063/1.3678637 (DOI)000300064500067 ()2-s2.0-84863018238 (Scopus ID)
Note
QC 20120323Available from: 2012-03-23 Created: 2012-03-19 Last updated: 2017-12-07Bibliographically approved
5. Enhanced electromagnetic field transfer across semiconductor-and-metal-nanoparticle oligomeric planar structure through exciton-plasmoninteractions
Open this publication in new window or tab >>Enhanced electromagnetic field transfer across semiconductor-and-metal-nanoparticle oligomeric planar structure through exciton-plasmoninteractions
(English)Manuscript (preprint) (Other academic)
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-93437 (URN)
Note
QS 2012Available from: 2012-04-17 Created: 2012-04-17 Last updated: 2012-04-17Bibliographically approved

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