| Summary: | 碩士 === 國立清華大學 === 光電工程研究所 === 101 === In the first part of this work, we use finite element method to simulate the optical vortex and super-focus phenomenon within an Archimedes spiral. There are two main factors that influence these phenomena: One is the geometrical charge determined by the geometry of plasmonic spiral device, the other is the spin angular momentum of the incident plane wave. We analyze the two kinds of surface plasmonic phenomenon for trapping particle and rotating particle. Traditionally, optical tweezer use focused laser beam to trap particle and manipulate. Plasmonic can enhance and localize light field which is similar to optical tweezers principle. Therefore, we use that concept to analyze Archimedes spiral structure.
In the secondary part of this work, our samples are fabricated using thermal evaporation to deposit a 200 nm film over a glass substrate. Then we make micro structure of plasmonic spiral device by using focused ion beam (FIB). In the experimental process, we use optical microscope system with a CCD (charge-coupled device) to observe the motion of micro-particles. Finally, we compare video result with simulation result. The simulation result is matching the experimental result which we observe.
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