Date of this Version
W. Huang, "Dynamic Electron Control using Light and Nanostructure", PhD Dissertation, University of Nebraska-Lincoln
The advent of nano-technology has made possible the manipulation of electron or light through nanostructures. For example, a nano-tip in near-field optical microscopy allows imaging beyond the diffraction limit, and a nano-fabricated hologram is used to produce electron vortex beam. While most schemes of electron control utilize only static components, dynamic electron beam control using both light and nanostructures has not yet been realized. In this dissertation, we explore this possibility and study the interplay between electron, light, and nanostructures. A understanding of such a system may facilitate dynamic electron beam control or even bring new insights to fundamental quantum mechanics.
The direct interaction between light and free electrons is weak, but the presence of nanostructures may modify the electron-light interaction in different ways. First, nanostructures may change a free electron's behavior by deforming the local vacuum field. When the electron's behavior is modified, its interaction with light could change too. Second, the illumination of light on nanostructures may give rise to induced surface charges or surface plasmon polaritons. The near-field of these charge structures could couple strongly with free electrons.
To learn about electron dynamics in the vacuum field, we start with a classical harmonic oscillator. When the oscillator is immersed in the vacuum field, its interaction with light could be modified. Our study shows that the harmonic oscillator exhibits an integer-spaced spectrum instead of a single resonance. On the other hand, to study how induced surface charges could mediate interaction between light and free electrons, we illuminated different surfaces with a low-intensity laser. As an electron beam is brought close to a surface that is illuminated with light, electron deflection was observed. This is considered to be a preliminary study to the effect of light on the electrons in the presence of nanostructures.
The implications of our studies are as follows. First, coherent electron-beam splitting may be possible through using spatial-temporal light modes on nanostructures. Second, electron beams could be used to probe optically induced surface near-fields. Further studies in these directions seem promising and may result in interesting discoveries.
Adviser: Herman Batelaan