Coupling In 2-D Photonic Crystal Defects And Wavelength Division Multiplexing

Photonic crystals (PCs) are periodic arrangement of dielectric materials. They provide the property of photonic band gap (PBG) which is similar to electronic band gap in semiconductor. As in semiconductor, photonic crystals can effectively control the transmission of light waves by introducing defects. Photonic crystal waveguide and resonant cavity are two basic components to constitute a variety of optoelectronic devices. Due to their compact size and easy integration, these devices are widely investigated. In this paper, the filter composed of photonic crystal waveguides and resonant cavities is discussed as the foundation of WDM.The main research works are as follows:1. The relation between PBG of two kinds of structures (two dimensional triangular lattice and square lattice) for TE polarization and the radius of dielectric cylinder is investigated. And the distributions of two dimensional PCs defect state are also studied. According to the coupling effect between waveguides, the coupling lengths are calculated and a reasonable directional coupler is also designed. By analyzing the coupling characteristic between waveguides and cavities and selecting different transmission direction, a variety of WDM system based on photonic crystal waveguides and micro-cavities can be designed.2. According to the coupled mode theory, the coupling characteristic between waveguides is investigated and a three-channel WDM is proposed. Due to the fact that different wavelengths correspond to different coupling lengths, we can design an ultra-compact multi-channel photonic crystal WDM.3. Firstly, we study the coupling effect between photonic waveguide and micro-cavity, then according to the evanescent coupling and guided-mode resonance theory, the micro-cavity frequency is calculated. Finally, based.on the characteristic, we propose a multi-channel compact WDM, and by optimizing photonic crystal micro-cavity and adding a reflective layer, the transmission efficiency is improved.4. By adding two scattering dielectric columns in a photonic crystal ring resonant, a resonant with high transmission rate is proposed. And the relation between scattering dielectric column radius and wavelength bandwidth is also studied. By changing the radius of the rod in the scattering and coupling region, the bandwidth and value of wavelength can be modulated effectively.