Optimization of low-loss and wide-band sharp photonic crystal waveguide bends using the genetic algorithm

This work discusses a robust genetic-algorithm based hybrid optimization scheme which was applied to handle the transmission problem in planar photonic crystal waveguide bend. For test purpose, two objective functions were proposed to characterize the transmission property of bend working at a special frequency or even over an entire frequency range. Optimization results for different 90° and 120° sharp bends have shown that, with the assistant of genetic-algorithm, random sizes of the cylinders surrounding the bend corner which correspond the maximum value of test functions are able to be rapidly obtained and obvious improvement of transmission property can be observed from each optimal bend structure, especially remarkable for the case of 120-I type bend.