Abstract
The polarization dependence of a directional coupler (DC) based on asymmetric cross-slot waveguides is investigated. Due to structural birefringence, the coupling behaviors of the quasi-TE and quasi-TM modes in the DC vary with the waveguide geometry. A polarization-independent directional coupler (PIDC) and polarization beam splitter (PBS) are proposed by tailoring the ratio of the coupling length for quasi-TE and quasi-TM modes. The simulated results show that the coupling lengths of the designed PIDC and PBS are 8 and 28.25 μm, respectively. Both the PIDC and PBS show an insertion loss (IL) on a bandwidth over 100 nm. The extinction ratios are for PIDC and for PBS. The fabrication-error tolerance of the practical devices is also discussed. In this study, we employ a commercial software tool for finite difference eigenmode and three-dimensional finite difference time domain methods to perform the numerical simulations.
© 2018 Optical Society of America
Full Article | PDF ArticleMore Like This
Nai-Chia Cheng, Yao-Feng Ma, Po-Han Fu, Chun-Chieh Chin, and Ding-Wei Huang
Appl. Opt. 54(3) 436-443 (2015)
Yao-Feng Ma, Ming-Je Sung, and Ding-Wei Huang
Appl. Opt. 49(36) 6979-6985 (2010)
Sijie Dai and Jinbiao Xiao
Appl. Opt. 61(1) 126-134 (2022)