Based On Genetic Algorithm To Optimize The Two-dimensional Photonic Band Gap Waveguide Output Characteristics

Photonic Crystals (PCs) describe a class of man-made material with the period variation of refractive index. The huge application and science potential of PCs makes it being an active research region since PCs' discovery in1980s. Recently, the optimization of photonic application, one of the major procedures in future PC production, has been intensively studies by researchers.Under such conditions, we studied the photonic crystal application based on Genetic Algorithm. The mainly works are demonstrated as following:Firstly, we analyzed the characteristics of the PC optimization space. Through analyzing, we find that the optimization space of PC is a combination of discrete and continuous parameters, making the traditional optimization algorithms insufficient. To solve the problem, we propose that Genetic Algorithm might be idea optimization algorithms for the PC optimization.Secondly, to expand the width of PC absolute Band-Gap, we use a combined algorithm of Genetic Algorithm and Plane Wave Expansion method to optimize the structure parameters of two-dimensional unit cells. In the first part, we optimize for the high-frequency absolute Band-Gap. And in the second part, we optimize the structure of the two-dimensional plane style unit cells which are assumed to have large absolute Band-Gap under light line. The results of the two parts meet very well with our assumption, indicating the correction of our optimization strategy.Finally, we utilize the combination algorithm of finite-difference time-domain method to design photonic crystal directional emission and focus applications. The optimized result indicates that we can automatically optimized all the physical influences, including impendence between photonic crystal waveguide and surface layer, phase matching between excitations of each unit cell of the surface layer and so on, can be optimized simultaneously. In addition, by introducing this optimized technology, we will be able to accurately control the emission angles as well as the focal locations. At the end, we study physical mechanism of the wave propagation on the surface layer.