Optical near field interaction of spherical quantum dots
Author
Amirahmadov, Togay
Advisor
Demir, Hilmi Volkan
Date
2012Publisher
Bilkent University
Language
English
Type
ThesisItem Usage Stats
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Abstract
Nanometer-sized materials can be used to make advanced photonic devices.
However, as far as the conventional far-field light is concerned, the size of these
photonic devices cannot be reduced beyond the diffraction limit of light, unless
emerging optical near-fields (ONF) are utilized. ONF is the localized field on the
surface of nanometric particles, manifesting itself in the form of dressed photons
as a result of light-matter interaction, which are bound to the material and not
massless. In this thesis, we theoretically study a system composed of differentsized
quantum dots involving ONF interactions to enable optical excitation
transfer. Here this is explained by resonance energy transfer via an optical nearfield
interaction between the lowest state of the small quantum dot and the first
dipole-forbidden excited state of the large quantum dot via the dressed photon
exchange for a specific ratio of quantum dot size. By using the projection operator
method, we derived the formalism for the transfered energy from one state to
another for strong confinement regime for the first time. We performed numerical
analyses of the optical near-field energy transfer rate for spherical colloidal
quantum dots made of CdSe, CdTe, CdSe/ZnS and PbSe. We estimated that the
energy transfer time to the dipole forbidden states of quantum dot is sufficiently
shorter than the radiative lifetime of excitons in each quantum dot. This model of
ONF is essential to understanding and designing systems of such quantum dots for
use in near-field photonic devices.