| Photonic crystals (PCs) consist of dielectric materials whose refractive index is periodically modulated in space. Its main characteristic is photonic band gap (PBG), frequency ranges in which light propagation is prohibited. Because of its strong control of photons, PCs have attracted great interests for their compactness and potential applications in all-optical communication network. In this thesis, transmission properties of two-dimensional (2-D) PC and photonic crystal waveguide (PCW) with triangular lattices are studied by finite difference time domain (FDTD) method. Some meaningful results are obtained for the design of PCs and related devices.1. The basic knowledge of PCs is introduced. The possible applications and main theoretical research methods of them are also presented.2. The basic FDTD equations of electromagnetic wave propagating are derived from Maxwell's equations. PCs with arbitrary shape and complicated media can be studied by FDTD method in a large range of frequency, which is convenient to analyze the transmission spectra of PC.3. The transmission properties of the 2-D PCs of ellipse dielectric rods are studied. The PBG and center frequency is investigated with the variation of long and short axes and azimuth angle of ellipse dielectric rods. The transmission spectra are further calculated after introducing defect. The results show that the PBG width and the center frequency depend on the shape,the material of rods and the azimuth angles, but the influence of azimuth angles is very small. The results provide the theoretical basis for the design of 2-D PCs.4. The effect of defect on PCW is discussed. The results indicate that more defect modes appear in guided gap with the increase of the radius and the refractive index of medium cylinder. In addition, broader guided gap appears when radius is close to that of air cylinder. Narrow band gaps appear in PCW with large refractive index. The results are very meaningful on design of 2-D PC devices. |
PDF Full Text Request