| Summary: | 碩士 === 國立臺灣大學 === 光電工程學研究所 === 95 === In this research, a two-dimensional finite-difference time-domain (FDTD) analysis is applied to model and study several subwavelength metallic structures. The Drude model for metallic material dispersion is implemented into the FDTD algorithm along with the dispersive uniaxial perfectly matched layer (UPML) as the absorbing boundary condition for the computational domain. This model is employed to study the extraordinary optical transmission of subwavelength slits. Previous literature has shown that when p-polarized wave impinging upon a corrugated metal thin film with a single slit, sharp peaks present on the transmission spectra at wavelengths much larger than the slit width. While the grooves in the input side of the thin film can enhance the transmission, grooves in the output side can shape the emerging radiation pattern. Here we calculate the transmission spectra and scan every factor that controls the transmission, including film thickness, slit width, groove depth, groove period, and the number of grooves. We also test the asymmetric groove patterns. The difference in transmission properties between the perfect electric conductor (PEC) thin film and the metal thin film is examined. We try to design the structure, and the maximum transmission enhancement up to 192 is observed for the PEC case. The resonance modes inside the slit can be used to explain these phenomena. The transmission properties of other periodic structures including periodic arrays of cylinders made of dielectric and metal are also analyzed. The electromagnetic effects on rough metallic surface for surface enhanced Raman scattering are studied.
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