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...[ Read more ]

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.