| Summary: | 碩士 === 國立海洋大學 === 光電科學研究所 === 91 === Sub-wavelength periodic structures have many applications in optical devices, for example, gratings, laser cavities, and photonic crystals, etc. The periodic structures can be fabricated by several methods. However, it is not easy to make sub-micron structures with optical methods. Because of the diffraction of light, the structure is limited to the size of wavelength. In this thesis, we present a novel method that can be easily used to fabricate sub-wavelength patterns with high quality. This method uses edge-diffracted light that occurs at the edges of dielectric structures. We found when light passes sub-micron dielectric structures, the edge-diffracted light will merge at higher topographic regions and form focused beams. We’ve verified the focusing effect by the finite-difference time-domain (FDTD) calculations, and the measurement of scanning near-field optical microscopy (NSOM). With this sub-micron focusing effect, we can easily fabricate sub-wavelength periodic structure by exposing photo-resist to these focused beams. One- and two-dimensional sub-wavelength periodic structures were made to demonstrate this photo-lithographic process.
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