According to the conventional theory, electromagnetic waves cannot transmit through a sub-wavelength hole. However, an electromagnetic wave in optical regime can transmit through sub-wavelength slits due to surface plasma effect.
From the simulation result of my advisor, it has been shown that the incident wave can be focused to a single-line width beyond the diffraction limit after transmitted through the double-slit. Then, the focused wave can propagate to the far zone. The results has been confirmed by experiment measurements, including the optimized structure studied in the thesis.
In order to understand the effect of the variations in fabrication for the performance, we calculate some variations of the optimized structure.
The result of focused light which can propagate has a wide range of the application possibilities. For example, it removes the limit on photo-lithography which plays an important role in semiconductor industry. It can be also used in biomoleculars with propagating light, especially in the harmless optical regime.

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