THESIS
2013
xiii, 154 pages : illustrations (some color) ; 30 cm
Abstract
Electromagnetic force arises in light-matter interactions as a result of momentum transfer and
it has many applications in small particle manipulations and opto-mechanical systems.
Although force on the order of nanonewton can be obtained in a conventional optical trapping
system by using focused laser beam, its magnitude is limited by the power of available laser
sources. To further broaden this field and probe the possibility of manipulating macroscopic
objects, strong electromagnetic forces are necessary. This thesis is devoted to the theoretical
and computational studies of electromagnetic forces, especially the approaches of obtaining
strong forces. We numerically implemented a 3D boundary element method with Nystrom
quadrature rule for the first time. The method can addres...[
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Electromagnetic force arises in light-matter interactions as a result of momentum transfer and
it has many applications in small particle manipulations and opto-mechanical systems.
Although force on the order of nanonewton can be obtained in a conventional optical trapping
system by using focused laser beam, its magnitude is limited by the power of available laser
sources. To further broaden this field and probe the possibility of manipulating macroscopic
objects, strong electromagnetic forces are necessary. This thesis is devoted to the theoretical
and computational studies of electromagnetic forces, especially the approaches of obtaining
strong forces. We numerically implemented a 3D boundary element method with Nystrom
quadrature rule for the first time. The method can address a variety of systems with arbitrary
geometric shapes that a conventional Mie theory cannot handle. Using this method, we
demonstrated that optical trapping force can be greatly enhanced by plasmonic resonance of
metallic structures and a metallic torus can be used to bind small particles. Then we proposed
a parallel-plate cavity structure where orders of magnitude of enhancement of electromagnetic
force can be realized at both the infrared and microwave frequencies. We found that the
attractive force in the infrared regime is caused by the kinetic energy associated with electrons.
The force becomes repulsive in the microwave regime due to the dominant fringe effect. We
developed a transmission line model that can successfully explain the underlying physics. We
show that the electromagnetic stress at the cavity resonance can cause measurable
deformation of a metallic thin film. In the last part of the thesis we show that spin angular
momentum of electromagnetic waves can induce a lateral force on a chiral particle, resulting
in a Spin-Hall-Effect-like phenomenon: particles with chirality of opposite signs tend to move
to the opposing sides of the interface.
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