| Finite-Difference Time-Domain (FDTD) method and its applications in electromagnetic scattering of complex objects and resonance behaviors of optical microcavities are studied respectively. The following work has mainly been done. Both two-dimension and three-dimension FDTD programs are designed. The dynamic visualization approach of electromagnetic fields is proposed and implemented by using mixed programming in Fortran and MATLAB. An automatic mesh-generating software for FDTD simulations is realized with VBA, which is based on AutoCAD environment. The octree optimization strategy is introduced to improve the time-consuming and memory requirement. An analysis of radar scattering characteristics of complex objects, such as missiles and tanks, is presented. The behaviors of morphological dependant resonance of dielectric cylindrical microcavities illuminated by plane wave are given in the framework of Lorentz-Mie theory. The resonance location, full width at half maximum, quality factor and free spectral range are discussed in detail, and then the resonant patterns of internal field are calculated. Simulation results of cylindrical microcavity by FDTD programs are carried out to compare with Mie theoretic results. Cylinder microcavities with elliptical and rough sidewall are investigated on impact of the deformation and surface perturbation on the intrinsical characteristics of the microcavities. The k-space theory of square-shaped microcavity is introduced, and also the FDTD results are given. A software based on FDTD principle is developed with mixed programming in C/Visual C++, Fortran and MATLAB, which is suitable for microcavities with arbitrary shape coupled by dielectric slab waveguide. With this software, the resonance behaviors of microdisk and microring microcavities are analyzed.
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