| Summary: | 碩士 === 國立交通大學 === 電子物理系所 === 107 === With the advantages of direct band-gap with two degenerate valleys of electronic bands and the atomically-thin thickness, transition metal dichalcogenides (TMDs) is promising for the future application in semiconductor optoelectronics. However, the atomically-thin thickness also limits its optical absorption and emission. Therefore, enhancing the photoluminescence (PL) is critical. On the other hand, exploiting the valley polarization in optoelectronic applications remains difficult due to the valley degeneracy. In order to create an imbalance between the two valleys, we design a new plasmonic structure based on Archimedean spirals. First, we report the design and fabrication of this chiral plasmonic structure, and exploit their optical properties coupling with monolayer WSe2. In the following, the optical field distribution and resonances of the chiral plasmonic structure were first studied by finite-difference-time-domain simulations. The strong field at the center of the chiral plasmonic structure affects carrier decay rates, resulting in strong PL emission. At the same time, we also investigate the influence of the chiral plasmonic structure coupling to monolayer WSe2 on the polarization of PL. The chiral plasmonic structure provides an effective way to enhance the optical signal of TMDs and a possible method for controlling the valley polarization.
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