Yüzey plazmon ile kuvvetlendirilmiş nanoyapılarda ve dalga kılavuzlarında optik kuvvet

The utilization of optical forces at the nano-scale is progressing rapidly following their successful employment in controlling micro-scale particles through optical traps and tweezers. Unlike the micro-scale, the nano-scale resides in the deep subwavelength limit, and thus, cannot bene fit from the simple ray-optics based formulations. Furthermore, the interaction of light with subwavelength structures is in general poor, unless the structure possesses metallic behavior to harness surface-plasmons for e fficient coupling to light. This, in turn, requires the formulation of near fi eld electrodynamics by taking the surface-plasmon excitations into account. These major points drive the basic research on the physics of optical forces at nanoscale for demanding biomedical, chemical and integrated photonic applications. In this thesis work, we investigate the optical forces in two di fferent systems: (i) The surface-plasmon enhanced optical forces on illuminated nanorod pairs, and (ii) the optical forces between coupled dielectric and metal-strip waveguides. We use a theoretical/numerical framework to study the electrodynamics of optical forces starting from Maxwells equations and the Maxwell Stress Tensor. In the first system, we determine the frequency spectrum of the optical force in a range where the surface plasmon resonance of the metal is present. In particular, we address the problem of tunability of the generated optical force and demonstrate that this is possible by incorporating a dielectric interlayer with tunable index of refraction (e.g. liquid crystal). The e ffect of permittivity and dielectric layer thickness on the common and relative forces are investigated in detail. For the coupled waveguides, we start with the coupled mode theory and obtain the modes of parallel dielectric waveguides. The mode pro files are used to determine the lateral stress on the waveguides. By incorporating a simple mechanical model, the structural deformation of the waveguide is obtained. Next, we set-up the model of plasmonic metal-strip waveguides in order to investigate the eff ect of surface-plasmons.