Asymmetric Oval-Shaped-Hole Photonic Crystal Waveguide Design by Artificial Intelligence Optimizers

Abstract

This paper proposes a new kind of photonic crystal waveguide (PCW) called asymmetric oval-shaped-hole PCW (AOPCW). In this PCW, 20 structural parameters are considered, which provides a very flexible PCW to design. The large number of variables makes the design process of this new PCW almost impossible by the current manual try and error methods. Therefore, the AOPCW is optimized automatically by the artificial intelligence optimization technique in three phases. First, the AOPCW is optimized to maximize normalized delay-bandwidth product. Second, it is optimized with respect to two objectives: averaged of group index ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\overline {n_g } $</tex-math> </inline-formula> ) and normalized bandwidth <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$(\Delta \omega /\omega _0)$</tex-math> </inline-formula> . Third, group velocity dispersion is also considered in addition to the two objectives in the second phase, so AOPCW is optimized with respect to three objectives. In all of the three phases, a band mixing avoidance mechanism is also considered and handled. The comparative study of the optimized designs proves that the proposed AOPCW is able to substantially outperform the current PCW structures in the literature. This paper also considers and discusses time-domain simulation issues of the PCW-based optical buffer.