heal.abstract |
Optical tweezers are important tools which nd many applications in fields
such as medicine, biology, microelectronics and even industry. The phenomenon of
optical trapping is based on phenomena of pressure of radiation and it constitutes
of the immobilization of a particle, with size in the order of micrometers (mm),
when this particle is situated under the in fluence of a laser beam. However, the
size limitation of the trapped particle in the optical trapping gave rise to the need
of (made us introduce) introducing the phenomenon of plasmonics in the optical
tweezers problem. Plasmonics are the quantums of plasma oscillations and it is
well known that their excitation can strengthen the electromagnetic eld locally,
giving the possibillity of trapping smaller particles, under the Rayleigh limitation.
In this thesis, we tried to determine,using computational simulations, which
metallic nanostructure is able to increase the local electric eld at a maximum.
The computation of the increase in the electric eld, has been made through the
calcualtion of the total optical force on the surface of the particle, for di fferent
metallic nanostructures. Firstly, we made a short reference to the phenomena of
optical tweezers and plasmonics in two di fferent chapters (Chapter 2 and Chapter 3
respectively), explaining the phenomena and the meanings that are used, in the fol-
lowing chapters of this thesis. In the chapter 4 the results of the three-dimensional
simulations are analyzed, while there is a reference to the two-dimensional simu-
lations as well. In addition, in chapter 5, we refer to the results obtained, using
the computational method of simulation FDTD, and the experimental measure-
ments from the convetional optical trapping experiment, follow (Chapter 6). These
experiments have been conducted in the laboratory of Laser Development and Ap-
plications in the Physics Department, in the School of Mathematical and Phyisical
Sciences. In the conclusion of this thesis, there are some suggestions for future re-
search, in theoritical and experimental basis, as well as some improvements of the
computational models. |
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