Design Of Simulation Platform For Periodic Structures

Simulation for diffracted electromagnetic fields from grating or photonic crystal isof great importance in their design and analysis. It lays the foundations for the study andanalysis about various periodic structures, and meanwhile it has been widely applied inintegrated circuits. Rigorous coupled-wave analysis (RCWA) method, which is alsowell known as Fourier modal method (FMM), can be utilized to analyze theelectromagnetic field distributions around the optical element of periodic structures bystrictly solving Maxwell’s functions in the grating region, where the polarization ofincident wave is taken into consideration and cyclical nature of medium and relatedfields is applied. Generally speaking, RCWA method is theoretically accurate, providedthat enough diffraction orders are retained. Although RCWA introduces an error whenprocessing numerical calculations, it has high precision and is relatively stable.Therefore, RCWA method has various applications in the design, manufacture,measurement and analysis of periodic structures with arbitrary geometrical size andworking in different wavelengths, such as diffractive optical elements, photonic crystals,and even general crystals.However, the RCWA method involves a large number of matrix computing in thesimulation of periodic structures, especially in the calculation of multi-layeredstructures, which consequently affects the calculation efficiency to a large extent. As aresult, the real-time monitor system based on RCWA method cannot response timely. Inconventional RCWA algorithm, non-rectangular grating is approximated as stackedlamellar grating, thus the number of eigensolutions to be solved is equal to the numberof sub-layers. Perturbation method (PM) introduced into the eigensolutions solving ofRCWA algorithm can greatly enhance the computational efficiency. When the opticaland geometrical parameters of these layers vary slightly, with the help of the PM, theeigensolutions in the eigensolutions-unknown layers can be deduced via theeigensolutions-known layers. In the latish sections of this thesis, a trapezoidal grating isconsidered to show the performance of this method. With the aim of developing method practically feasible in engineering applications,this paper investigates a new method based on the PM and the RCWA method. In thiswork, a simulation software platform is constructed, which can be adopted to analyzethe diffraction characteristics of periodic structures. This simulation platform works inwindows platform, thus it is interface friendly and has wide applications. What’s more,it can simulate the diffraction efficiency of a uniform layer, one-dimensional ortwo-dimensional grating structures with varied shapes, and certain periodicmicro-structures. The users of this simulation platform only need to input someparameters or load relevant configuration file, then click the corresponding button onthe right side. Seconds later, data and relevant curve will be automatically plotted on theinterface. Moreover, parts of the interface are reserved to facilitate future applicationssuch as optimization output. More importantly, the design of graphic user interface(GUI) is designed, which enables visible analysis of the diffraction results easily andintuitively.