| Summary: | 碩士 === 國立中央大學 === 光電科學與工程學系 === 103 === Photonic band gaps are defined as the frequency intervals that light is forbidden to propagate inside the photonic crystal (PC). This is the most important characteristic of photonic crystals. A photonic crystal waveguide (PCW) can be formed, taking the dielectric rod-array structure as an example, by making a line defect through removing one row of dielectric rods. This is the fundamental method to make a PCW.
In this thesis, we study the transmission properties of two sophisticated PCWs formed by the structures of “PCW of air defect” (PCWA) and “PCW of dielectric rods defect” (PCWD), respectively. Specifically, we design PCWA by taking out a line of rods and changing the radius of the “side-wall rods” of the line defect to , and design PCWD by replacing a line of rods of radius with a line of rods of radius , -being the radius of the rods consisting of the background PC. Both approaches change the dispersion relation of the guided modes, which gives us the possibility of designing nano-devices such like wavelength division multiplexers (WDM) through tuning the radius of the dielectric rods.
Besides the above mentioned wavelength division multiplexers we also design other kinds of WDMs in the square-lattice and triangular-lattice PCs. Based on our simulation results, we find that the WDMs in the triangular-lattice has higher resolution in distinguishing two waves of very close frequencies. These designs, we expect, after some elaboration, can serve as useful nano-devices in the future.
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