Nano optical propeller based on localized field intensity enhancement of surface plasmons

摘要

There is acting force that light has on any substances, but the force is too weak to be sensed. While the momentum transfer between light and substance can be greatly improved within nanoscales. Scientists have successfully captured and transported micro-particles by using focusing light in liquid state, which is called optical tweezers. However, this approach needs to be processed with removable powerful focal source and meanwhile in a state of liquid. These requirements seriously restrict its development from optical tweezers to optical propeller. This paper proposes a new method: to produce localized surface plasmons enhancement by asymmetric nanostructures so that a gradient optical field whose intensity is 70 times higher than that of incident light is formed on a nano orbit with a length of 200nm. The strong gradient force makes it possible for the small particles laid on nanostructure to get strong momentum at a certain direction without strong light sources, which breaks through the near field gravitation to move. Meanwhile, the nanostructure can be expanded into multistage accelerating structure, and expanded into an array, thus providing a plane thrust and forming an optical propeller in real sense. At last, electron beam lithography (EBL) is employed to prepare structures with only tens of nanometers in size. A series of better preparation technics are concluded to get samples with good shapes, which provides technical guarantee for the application of nano optical propeller in the future.