Analysis Of Transmission Properties Of Periodic Structures At Arbitrary Incident Angles Based On Iterated Finite-Difference Time-Domain Method

The periodic structure is defined as the objects formed by given materials according to a periodic arrangement in space. This kind of structure is widely used in scientific research and practical application because of the special physical properties. Recently, more and more attention has been paid to the periodic structure formed by the dispersive materials, such as frequency selective surface and new types of solar cell. Therefore, it is very important to calculate and analyze all kinds of dispersive periodic structures.The FDTD method is widely used in the calculation of the electromagnetic properties of periodic structures. This method is used to solve the electromagnetic field in time and space by discretizing the electric field and the magnetic field components. Under the condition of normal incidence, the electromagnetic properties of periodic structures can be analyzed easily by using the periodic boundary condition. However, in the case of oblique incidence, there is phase difference in the process of the field value’s converting from the frequency domain to the time domain. In the calculation, because the field value of the electromagnetic field in the future is unknown, there are many difficulties in solving the oblique incidence of the periodic structures using the traditional FDTD method.In this thesis, an iterative algorithm based on the FDTD is utilized, which can keep the field value in the process of each complete iteration. Then the field values obtained from the last iteration approximately replace the future field values needed in the current iteration. Thus the unknown problems of advanced field are solved skillfully under the condition of oblique incidence. With the increasing times of iterations, the approximate field will gradually get to the real field and the calculation error owing to substitution will be smaller. The result of convergence after several iterations is obtained finally. The processes of this thesis are as follows:1. Research background of the periodic structures is introduced, and the importance of the work in this thesis is clarified. The base methods of FDTD are briefly introduced. Based on this, the iterative FDTD method is introduced.2. The algorithm of the iterative FDTD method under the condition of oblique incidence is given, and the concrete implementation process of the algorithm is described in detail. Then the two and three dimensional periodic structures are simulated respectively to verify the validity of this method.3. The iterated FDTD method is further introduced into the analysis of dispersive period structures. By calculating the three examples with extensive application value and important physical significance, the applicability of this method to the Drude dispersion model and the Drude-Lorentz model is verified.4. By adding the special absorbing layer at the back of the PML layer, the absorption of evanescent wave is achieved in the long time of simulating periodic structures.